BIOL 121A
INTRODUCTORY ZOOLOGY
Topic 1b - Evolutionary Principles
& Zoology Basics
1
DARWIN’S THEORY SUMMARIZED
OBSERVATIONS
PROPOSED MECHANISMS
• Perpetual change
• Gradualism (macroevolution)
• Common descent
• Natural selection (microevolution)
• Multiplication of species
2
COMMON DESCENT
• All living organisms share a common ancestor; all
animals share a common ancestor
• How do we know?
3
Evidence of common descent
HOMOLOGY
• Characteristics ____________________ that may
be ______________________
E.g., Bones of
vertebrate limbs all
have the same parts
but are MODIFIED for
walking, swimming,
flying
4
WHAT ABOUT STRUCTURES THAT
SHARE THE SAME FUNCTION?
These organisms all have a fusiform shape, but did
this arise from homology?
5
Evidence of common descent
ONTOGENY
• Homologous characteristics may only exist during
early development before being _______________
What happens to
our gill slits and tail?
6
DARWIN’S THEORY SUMMARIZED
OBSERVATIONS
PROPOSED MECHANISMS
• Perpetual change
• Gradualism (macroevolution)
• Common descent
• Natural selection (microevolution)
• Multiplication of species
7
MULTIPLICATION OF SPECIES
• ____________ = Evolutionary process by which
new species arise
• What is a species?
• Group (population) of interbreeding individuals of
common ancestry that are reproductively isolated
8
Evidence of multiplication of species
TIME
ALLOPATRIC
(GEOGRAPHIC) SPECIATION
Population
Reproduction barrier
Population
Population
Reproduction barrier
Population
Population
Population
Population
**If the populations can no longer interbreed, a new species has emerged!
9
Heliocidaris crassispina
Strongylocentrotus intermedius
What barriers exist to
reproduction?
https://bmcecolevol.biomedcentral.com/articles/10.1186/s12
862-020-01667-8
10
REPRODUCTIVE BARRIERS
• PREZYGOTIC
• Geographic
• Temporal
• Mechanical
• POSTZYGOTIC
• Fertilization occurs but
hybrids are non-viable, or
sterile
• Behavioural
11
Evidence of multiplication of species
ADAPTIVE RADIATION
• Speciation gone nuts!
Many ecologically diverse species emerge over short geological timescales. HOW?
12
DARWIN’S THEORY SUMMARIZED
OBSERVATIONS
PROPOSED MECHANISMS
• Perpetual change
• Gradualism (macroevolution)
• Common descent
• Natural selection (microevolution)
• Multiplication of species
13
GRADUALISM (VS. PUNCTUATED
EQUILIBRIUM)
• Accumulated, continuous changes in morphologies in
natural populations can ___________________
• But what rate of change occurs?
Slow and constant
= _________________
Inconsistent, with some periods of
great changes and others of little
change = __________________
14
Darwin
Supported by fossil record
showing small morphological
changes (like vestigial
structures)
Supported by fossil record
having large gaps between
diverse body plans
15
DARWIN’S THEORY SUMMARIZED
OBSERVATIONS
PROPOSED MECHANISMS
• Perpetual change
• Gradualism (macroevolution)
• Common descent
• Natural selection (microevolution)
• Multiplication of species
16
NATURAL SELECTION
• Darwin’s model of evolution by natural selection
• 5 observations and 3 inferences
• Is a testable framework – why might this matter?
• Does not include any mechanism of inheritance –
why?
17
NATURAL SELECTION
(MODERN UPDATE)
• The primary agent of evolutionary change where
evolution is defined as
___________________________________
• Acts on
1. Heritable variation
2. The sum of all traits in an animal, not individual traits
18
The relationship between genotype and phenotype can be complicated but has helped
drive understanding of natural selection in modern biology
https://www.frontiersin.org/articles/10.3389/fgene.2015.0017
9/full
19
NATURAL SELECTION MODEL
(VISTA)
1.
Variation (random mutations and DNA
recombination)
2.
Inheritance of traits by offspring
3.
Organisms with the best combo of traits for the
environment survive to reproduce (fitness) Selection
4.
Over time gene frequencies change
5.
New traits (adaptations) and species gradually
emerge (speciation)
20
TYPES OF SELECTION IN
POPULATIONS
1.
Stabilizing selection (reduction in extremes)
2.
Directional selection (selection for an extreme)
3.
Disruptive selection (selection for multiple extremes)
21
22
DARWIN’S THEORY SUMMARIZED
OBSERVATIONS
PROPOSED MECHANISMS
• Perpetual change
• Gradualism (macroevolution)
• Common descent
• Natural selection (microevolution)
• Multiplication of species
23
WHERE ARE WE NOW?
Neo-Darwinism
Mendelian inheritance
Gene mutation (alleles)
Chromosomes
Population genetics
Systematics
Paleontology (speciation and trends)
Darwin
Variation
Inheritance
Natural
Selection
24
NEO-DARWINISM
Microevolution
Natural selection is one mechanism
Speciation
Macroevolution
25
Accumulation of
genetic changes
leads to big things,
like new species
Genetic change
within populations
Driven by various
mechanisms
26
MICROEVOLUTION
• Genetic change in natural populations
• Driven by:
27
SEXUAL SELECTION
• Traits that benefit sexual
reproductive success may
be harmful for survival
• E.g., Peacock tails are
important for mate selection
but what about predators?
28
GENETIC DRIFT
• Changes in gene frequencies from one generation to
the next
• Can occur when population sizes change
• Often limits pool of possible genetic responses to
environmental change
29
Founder effect
Bottleneck effect
Result is the same = loss of genetic variation
30
MACROEVOLUTION
• Large-scale events in evolution
• Speciation and extinction events that result from
microevolution or environmental change
31
MASS
EXTINCTIONS
What happens after an extinction?
• Extinction rate >
speciation rate
• Permian extinction =
90% of all marine
invertebrates
• Cretaceous extinction
= dinosaurs
32
To help you with your studying!
EVOLUTION LEARNING
OBJECTIVES
• Describe the 5 main points of Darwin’s evolutionary
theory
• Explain the evidence supporting perpetual change, common
decent, and multiplication of species
• Explain gradualism and natural selection, including ongoing
controversies with gradualism
• Describe Neo-Darwinism and what new information it
incorporates into our understanding of evolution
• List and explain three mechanisms of microevolution
33
BIOL 121A
INTRODUCTORY ZOOLOGY
Topic 1c - Evolutionary Principles
& Zoology Basics
1
SYSTEMATICS
• Study of the variation among animal populations to
reveal their evolutionary relationships
• _____________ = a part of systematics that deals with
the formal naming and grouping of species
• Why might it be important to have a set naming
scheme?
2
Puma concolor
What am I? Cougar, mountain lion, puma, Florida panther, deer tiger, catamount, lion
3
TAXONOMIC C ATEGORIES
• We use formal, hierarchical
categories to group and name
organisms
• Each major category (except for
species) can be called a taxon (pl.
taxa)
4
A great resource to find marine species names
5
https://www.marinespecies.org/aphia.php?p=search
PH Y L OG ENET IC
TREES
• Evolutionary “trees”
that visually show
the relationships
among organisms or
groups of organisms
• We use shared
___________
(morphological,
genetic) to build
trees manually or
with software
What happens at branch points?
6
PH Y L OG ENET IC
TREES (2)
Clade A
Clade B
Clade C
• _________ are the
fundamental unit
found in trees
• Includes the ancestral
lineage and all species
descended from it
• Can be defined after
each major branch
point (_________)
Organisms in a clade all have defining, shared
characters called __________________
7
PH Y L OG ENET IC
TREES (3)
Sister group to the green clade
• _____________
are the next closest
group in the tree
outside the clade
8
WHAT MAKES A GOOD TREE?
• Ideal trees are parsimonious, meaning they are built with
the least number of branches to achieve a solution that
makes sense
• Ideal clades are ____________________
9
GOOD CLADES VS. BAD CLADES
10
Modern examples of bad clades
“Prokaryotes”
Archaea + Bacteria
11
Modern examples of bad clades
“Invertebrates”
At least one invert
in Phylum
Chordata!
12
PRACTICE
Label the nodes
Identify a monophyletic grouping in this tree
Identify a paraphyletic or polyphyletic grouping in this tree
13
To help you with your studying!
CLASSIFICATION & PHYLOGENY
LEARNING OBJECTIVES
• Describe the hierarchical naming and grouping scheme
used in systematics
• Why are common names problematic?
• What makes a good phylogenetic tree? A good clade?
• Practice reading phylogenetic trees to understand
relationships among organisms
14
BIOL 121A
INTRODUCTORY ZOOLOGY
Topic 2 – Animal Body Plans
1
HOW DO WE CLASSIFY
ANIMALS BASED ON FORM
AND FUNCTION?
2
DIVERSE WAYS TO GROUP
ANIMALS
• Body symmetry
• Body plan
• What openings are present?
• What tissue layers are present?
• What body cavities are present?
• What appendages are present?
• Developmental mode
• Types of cells and cellular organization
3
BODY SYMMETRY
Is this symmetrical?
4
BODY SYMMETRY (2)
5
Bilateria
More complex body plans
associated with evolution of
bilateral symmetry
6
It depends on the group. But there are a few general rules.
DESCRIBING BODY
ORIENTATION
RADIAL
BILATERAL
Aboral
Dorsal
Oral
Posterior
Caudal
Anterior
Cephalic
Ventral
7
BODY OPENINGS
• How many openings? What are they for?
• The usual openings we focus on are relative to the
gut
• Just a mouth = a ___________
• Mouth and anus = _________________
• But what happens when there is no gut?
8
Loss of a mouth and gut can be associated with certain types of lifestyles = parasite
Hi. I’m a tapeworm.
9
TISSUE LAYERS
• Three main embryonic source tissues become all the
cell and tissue types seen in adults
1. ___________ = internal organs, lining of the gut etc.
2. ______________ = muscles, bones
3. ____________ = skin, nervous system
10
CLASSIFICATION BASED ON
EMBRYONIC SOURCE TISSUE*
DIPLOBLASTIC animals
TRIPLOBLASTIC animals
Everyone else
Endoderm and ectoderm only
All three types
11
The caveat of this method is you need to have tissues
12
TISSUE LAYERS (2)
• Two main clades associated with type of classification
• ____________ = all animals including sponges
• ______________ = all animals with at least 2
embryonic source tissues
13
Eumetazoa
Metazoa
Having all three embryonic
source tissues associated with
more complex body plans
14
BODY
C AVITIES
• These are best
visualized in cross
sections
• Triploblastic animals
have body cavities to
allow for separation of
organs (excludes inside
the gut – why?)
Gut lumen (not a cavity)
Coelom (main body
cavity)
• Usually associated with
more complex body
plans
15
COELOMIC C AVITY
• Special body cavities that are completely contained
within a layer of mesoderm
• Animals with no coelom are called ___________
• Animals with a coelom are called _____________
• And… animals with a “fake” coelom are called
_______________
16
LET’S DRAW COELOMIC
C AVITIES
Blue = Ectoderm
Orange = Mesoderm
Yellow = Endoderm
17
AR R ANG E MENT
OF
AP P E NDAG E S
• Especially important
for the classification
of certain taxa
18
DEVELOPMENT MODE
• Animal embryos develop different ways
• Some develop the mouth first, and then the anus =
_________________
• Others develop the anus first, and then the mouth =
_________________
• Animal cells can divide in a spiral or radial (more squarelike) fashion
19
BASIC DEVELOPMENTAL
PATHWAY
Zygote (a
single cell
formed from
egg and
sperm)
Numberedcell stages (4,
8, 16 etc.)
Blastula
(hollow ball
of cells)
Gastrula
(hollow ball
of cells with a
gut tunnelling
through it)
Larval
stage(s) for
some animals
/ Embryonic
stages for
others
Juvenile
The first “opening” that forms
is called the ___________
what happens to it?
20
Most invertebrates
Echinoderms, Chordates
21
Protostomia
Most animals can be grouped
based on the fate of the
blastopore
Deuterostomia
22
What is a
human?
Bigger to
smaller
clades
SUMMARY OF MAJOR ANIMAL
CLADES
23
CELL TYPES
• Certain cell types are unique within a phylum
• E.g., cnidocytes in Cnidaria
24
To help you with your studying!
ANIMAL BODY PLANS LEARNING
OBJECTIVES
• Identify five ways we can use animal body plans and
anatomy to classify animals.
• Identify key clades of animals based on differences in body
plans and anatomy (metazoa, eumetazoa, bilateria,
protostomia, deuterostomia)
• Define and draw an example of an acoelomate, a
pseudocoelomate, and a coelomate
25
BIOL 121A
INTRODUCTORY ZOOLOGY
Topic 3 – Protists
1
A L L E U K A RYOT I C L I F E
SHARES A COMMON
A N C E S TO R
2
KINGDOM PROTISTA
• Originally called Phylum Protozoa
• “the first animals”
• Now has become a catch all taxon for groups that aren’t quite
plant, animal, or fungi
• Mostly unicellular
• All lack collagen and chitin in their cell walls
3
WARNING
• The taxonomy in our textbook represents a snapshot
of what was known at the time
• It is out of date, and I will periodically make you
aware of big changes
• If you look up taxonomy from other sources there
could be differences - use the notes as the definitive
guide
4
KINGDOM
P ROT I S TA H A S A
C L A S S I F I C AT I O N
P RO B L E M
Is it a good clade?
Plants
Animals + Fungi
5
Plants
Animals + Fungi
Based on what we know about phylogenies
from last topic, plants, fungi and animals should
be included in Kingdom Protista to make it
monophyletic
Animals have close protist relatives
6
WHY STUDY PROTISTS?
• They are at the base of the animal tree of life
• Primitive examples of cell differentiation and
organization in colonial forms
• Multicellularity*
7
TRADITIONAL VS. MODERN
CLASSIFICATION SCHEMES
• Traditional = Locomotory mode groups (3)
• FLAGELLATES (flagella; either plant or animal like)
• AMOEBAS (amoeba-like; either naked or shelled)
• CILLIATES (cilia)
8
TRADITIONAL VS. MODERN
CLASSIFICATION SCHEMES
• Modern = RNA-based supergroups (4)
• Based on molecular evidence, modes of locomotion
evolved independently multiple times (e.g. flagella)
9
CILIA VS. FLAGELLA
• Motile structures made of cytoskeletal protein subunits (microtubules) and motor proteins (dyneins)
• Ultrastructure is the same
• “Flagellates” have one or more flagella
• “Ciliates” have 1000s of cilia
10
11
12
“PHYTOFLAGELLATES”
• Protists with one or more flagella for locomotion
• Have chloroplasts, photosynthesis (sometimes)
• Representative groups
• Euglenozoa
• “Green algae”
• Dinoflagellata
13
“Green algae”
Animals + Fungi
14
EUGLENOZOA
• Euglenids/euglenoids/euglenophytes
• Mostly fresh water
• Mixotrophs, switching feeding modes
based on the environment
15
EUGLENA GRACILIS
Beneath cell
membrane is a
matrix of rigid
protein called the
pellicle
It allows the cell to
contract and
change shape
16
The flagella are modified into mucus covered stalks but can be re-grown
in 1 hour
COLONIAL EUGLENID COLACIUM
17
“GREEN ALGAE”
• Close relatives of plants
• Mostly freshwater
• Autotrophic
18
CHLAMYDOMONAS
Have 2 flagella
Special compartment in the
chloroplast called pyrenoids
that promote effective
photosynthesis
19
C OL ONI A L
G R E EN AL G AE
VO LVOX
• Forms spherical,
cooperative colonies
• Cell
differentiation
• Colony polarity
• Primitive
multicellularity?
20
D I N O F L AG E L L AT E S
• Two dissimilar flagella in
different directions, called
dinokont flagellation
• Marine and freshwater
• Mixotrophic
21
CERATIUM
Very common in
freshwater and marine
Spines are longer in
warmer waters
Covered in cellulose
plates called thecal
plates
22
23
TOO MANY C E R AT I U M AND OT H E R
DI NOFL AG ELLAT ES C A N L E A D TO R E D T I D E S
A ND FI SH K I L LS
24
SYMBIODINIUM
Endosymbiotic dinoflagellates
that live in the endoderm of
cnidarians
Provide photosynthetic
products
25
“ZOOFLAGELLATES”
• Protists with one or more flagella for locomotion
• Are heterotrophic or parasitic
• Representative groups
• Parabasalids
• Diplomonads
• Choanoflagellates
26
“Green algae”
Animals + Fungi
Choanoflagellates
27
PARABASALIDS
• Commensal and parasitic forms in
animals and plants
• Responsible for human disease
(e.g. Sleeping Sickness)
• Trypanosoma
28
DIPLOMONADS
• Responsible for human
disease (e.g., Giardia)
• Each are double cells, with
two nuclei and four flagella
• Lack mitochondria
29
C H O A N O F L A G E L L AT E S
• Heterotrophic
• Sessile or motile
• Solitary or colonial
• More on this later!
30
NAKED AMOEBAS
• Protists with pseudopods used for crawling and feeding
• Do not have shell plates or tests
• Are heterotrophic or parasitic
• Representative groups
• Amoebozoa
31
“Green algae”
Animals + Fungi
32
A M O E B O Z OA
• Tubular pseudopods
(lobose) powered
by microfilaments
• Food is obtained via
phagocytosis
33
AMOEBOID MOVEMENT
34
TESTATE AMOEBAS
• Protists with pseudopods used for crawling and feeding
• Have shell plates or tests
• Are heterotrophic, some are symbiotic
• Representative groups
• Foraminifera
• Radiolaria
35
“Green algae”
Animals + Fungi
36
FORAMINIFERA
• Amoeboid with a shell (CaCO3)
• Skinny pseudopods poke out from the shell used for
capturing bacteria and algae
37
38
Biostratigraphy studies for
aging ocean sediments
Position in the water
column can be used to ID
thermocline, upwelling
IMPORTANCE
OF FORAMS
Reconstruct ancient climate
based on their distributions
as microfossils in rock
Oil exploitation
39
RADIOLARIANS
• Amoeboid with a shell (Si)
• Skinny pseudopods poke out from the shell used for
capturing bacteria and algae
40
41
COLONIAL RADIOLARIAN
SOLENOPHAERA COLLINA
http://www.tidelines.org/columns/salty-pretzelhold-mustard
42
CILIATES
• Protists with cilia for locomotion
• Are heterotrophic, some are parasitic
• Representative groups
• Ciliophora
43
“Green algae”
Animals + Fungi
44
CILIOPHORA
• Found anywhere there is water
• Free living, parasitic, commensal
• Taxonomy is currently being
revised
45
COLONIAL CILIATE
ZOOTHAMNIUM
Giant (up to several cm) colonies with cooperation and cell differentiation
They have chemoautotrophic bacterial symbionts
46
Study summary slide
TAXONOMY SUMMARY
• 3 groupings based on locomotion (example taxa)
1.
Flagellates
• Phytoflagellates (Euglenozoa, “Green algae”, Dinoflagellata)
• Zooflagellates (Parabasalids, Diplomonads, Choanoflagellates)
2.
Amoebas
• Naked (Amoebozoa)
• Testate (Foraminifera, Radiolaria)
3.
Ciliates
• (Ciliophora)
47
BIOL 121A
INTRODUCTORY ZOOLOGY
Topic 4 – Porifera
1
We recently looked at
protist representatives
Plants
Animals + Fungi
2
Now our focus shifts to
the origin of the animals
3
WHAT MAKES AN ANIMAL AN
ANIMAL?
1. Eukaryotic cells
2. Multicellular
3. Tissues and cell organization
4. Sexual reproduction
5. Blastula during development
6. Locomotion
7. Dedicated sense organs
8. Heterotrophic
Animals collectively called the Metazoa
4
ARE PROTIST COLONIES
MULTICELLULAR?
• Some exhibit rudimentary differentiation among cells
• Some exhibit coordinated interaction among cells
• But two key features are missing:
• Distinct internal environment
• Cellular instead of cytoplasmic level of body organization
5
ARE THERE ANY MULTICELLULAR
“PROTISTS”
You bet. Since seaweeds and kelps are technically nested within Kingdom Protista
6
PROTIST-LIKE ANIMAL
ANCESTOR
• The shared ancestor of all animals was likely protist-like
• But there are several competing theories as to what those
ancestors looked like
1. (Generally accepted) Choanoflagellate-like
2. (Emerging) Archaeocyte-like
7
SIMPLEST ANIMALS
• Phylum Porifera (sponges)
• Phylum Ctenophora (comb jellies)
• Phylum Cnidaria (jellies, anemones, corals)
• We can start to understand how animal life emerged from
protist ancestors by looking at the cell types and genetics
of simple animals
8
PHYLUM PORIFERA
• Defining characteristics: cells with microvillar collars
surrounding flagella, with units from single cells or syncytia
• 98% Marine
• Asymmetrical body plans, no embryonic tissue layers, no
muscles, no nervous elements, no coelom
• Four main taxa (Classes Calcarea, Demospongiae,
Hexactinellida, Homoscleromorpha)
9
10
Sponges are some of the earliest animals,
and part of the “all animal club” = Metazoans
Metazoa = Animalia
11
GENERAL SPONGE
MORPHOLOGY
Water enters many small openings called ostia into the hollow center of the
sponge (spongocoel), and exits through one or more larger openings called
oscula
12
OUTSIDE
INSIDE
SPONGE BODY WALL XSECTION
13
SPONGE LAYERS
• Outer layer made up of flattened epithelial cells
• Pinacocytes form an outer protective later, can
phagocytize large particles
• Porocytes make up the ostia, contractile and can control
water flow
14
SPONGE LAYERS
• Middle layer a non-living matrix of polysaccharide gel
with various cells, skeletal elements (called mesohyl)
• Archaeocytes are wandering amoeboid cells that crawl in
the mesohyl, many roles, can become other cell types
• Sclerocytes secrete skeletal elements called spicules
• Spongocytes secrete protein fibres for support called
spongin
15
Spicules are
beautiful and
taxonomically
useful
Ca and Si
16
SPONGE LAYERS
• Inner layer lined in flagellated collar cells called
choanocytes
17
THE CHOANOCYTE
“Collar cells”
Flagellum beats and
produces a zone of low
pressure
Food is drawn across
the collar and is then
phagocytized
Intracellular digestion
18
CHOANOCYTE ORGANIZATION
Three general sponge body plans
19
CHOANOCYTES =
CHOANOFLAGELLATES?
20
EVIDENCE
• Very similar morphology, feeding mode
• Genomic evidence that modern choanoflagellates are
the closest relative of animals
• Proterospongia is a modern colony of choanoflagellates
that includes individual cells imbedded in a gel matrix
(kinda like mesohyl?)
21
Proterospongiae
22
SPONGE FEEDING
• Most sponges filter feed bacteria and other
small particles using the choanocytes
• Archaeocytes transport packaged food vesicles from
the choanocytes to other cells
• Alternative feedings modes including carnivory
and hosting photosynthetic endosymbionts can
also be seen
23
C ARNIVOROUS SPONGES
FAMILY CLADORHIZIDAE
24
“PHOTOSYNTHETIC” SPONGES
Freshwater sponge
Spongilla has green
algae symbionts in
the mesohyl
25
SPONGE PHYSIOLOGY
• No distinct circulatory system, respiratory system,
excretory system
• Water movement through the sponge does all these
steps
• O2-CO2 exchange via diffusion, ammonia excreted via
diffusion
26
SPONGE REPRODUCTION
• Asexual
• Fragmentation, budding, gemmules (dormant spores)
• Sexual
• Hermaphrodites, sperm produced by choanocytes, eggs
produced by transformation of archaeocytes
• Sperm is broadcast spawned, captured by other sponges
27
SPONGE BROADCAST
SPAWNING
28
GENERAL SEXUAL LIFE HISTORY
29
C AN
SPONGES
MOVE?
30
SPONGE SNEEZING
31
SPONGE TAXONOMY
32
CLASS
C ALC AREA
• Spicules made of
magnesium-calcite
• All three sponge
body plans (ascon,
sycon, leucon)
33
CLASS
DEMOSPONGIAE
• Spicules made of
silica and / or spongin
• Nearly all leucon
• 80% of all sponge
species
• Filter feeding and
carnivorous
representative
34
CLASS
H E X AC T I N E L L I DA
• Six-rayed spicules
made of silica and
chitin
• Entire sponge is
syncytial (one giant
cell!)
• No outer
pinacoderm layer
35
CLOUD SPONGE REEFS IN HEC ATE
STRAIT
(UNESCO HERITAGE SITE)
36
CLASS
H O M O S C L E RO M O R P H A
• Most lack spicules but
they are silica when
present
• New group based on
rRNA
• True epithelial cells
with a basal
membrane and cilia
37
For studying
SUMMARY SLIDE
• Phylum: Porifera
• Clades of interest: Metazoa
• Classes (4): Calcarea, Demospongiae, Hexactinellida,
Homoscleromorpha
• Differ in spicule composition and body plan
• No embryonic source tissues, cannot determine fate of
blastopore, cannot define the type of coelom
38
BIOL 121A
INTRODUCTORY ZOOLOGY
Topic 5 – Cnidaria and Ctenophora
1
PHYLUM CNIDARIA
• Defining characteristics: Intracellular organelles for prey
capture called cnidae
• 99% Marine
• Diploblastic with true tissue organization, cannot determine
fate of blastopore, cannot define the type of coelom
• Six main taxa (Class Anthozoa, Hydrozoa, Cubozoa, Scyphozoa,
[Myxozoa, Staurozoa])
2
3
Because they have complex tissues are considered “Eumetazoans”
Are the sister group to a key transition point in animal evolution = Bilateral Symmetry
Eumetazoa = True tissues
Metazoa = Animalia
4
Which one is this?
G E N E R A L C N I DA R I A N
B O DY P L A N
• Two main types:
• Upright, “anemone-like”
called polyp
• Upside down, “jellyfish-like”
called medusa
5
EXTERNAL BODY SYMMETRY
Both body plans have true radial symmetry
6
ALWAYS EXCEPTIONS!
Sea pens are bilateral overall, but each individual polyp is radial
7
BASIC CONSTRUCTION
• Two living tissue layers:
• Epidermis (outer, ectoderm origin)
• Gastrodermis (inner, endoderm origin)
• Non-living middle layer:
• Mesoglea
8
Red regions are epidermal, blue regions gastrodermis
9
CNIDAE
• Specialized organelles within cells called cnidocytes
• The best-known type is the nematocyst
• Used for feeding and defence
10
11
• Some species of anemones
reproduce through fission
CLONE WARS
• This produces clones
• But clones produced from
different parents do not play
nicely together
12
13
Anthopleura elegantissima undergoing fission
14
Who has a
medusa and who
doesn’t?
CNIDARIAN RELATIONSHIPS
15
CLASS SCYPHOZOA
• Large marine medusae
• Very thick mesoglea layer
• Life cycle includes both sexual and asexual
components
• Alternates between medusa and polyp
16
SCYPHOZOAN INTERNAL
FEATURES
• Mouth connects via pharynx (manubrium) to welldeveloped gastrovascular canals in the bell
• Four gastric pouches are filled with short tentacles
that secret enzymes and nematocysts into prey
(gastric filaments)
• In rare cases, some species also have zooxanthellae as
symbionts in their tissues
17
18
19
CLASS CUBOZOA
• Tiny marine medusae
• Very complex rhopalia
(sensory structures) with
lensed ocelli
• Often extremely toxic “sea
wasps”
20
The lower
lens eye is
capable of
seeing images
and is one of
the most
complex
invert eyes
21
CLASS HYDROZOA
• Mixture of polyp-dominant and medusaedominant forms + weirdos
• Freshwater and marine
• Nematocysts only in outer epidermis, not
in the gastrodermis
• Simplistic ocelli and sensory structures
22
HYDROZOAN MEDUSA
Ocelli
eye spots
Ocelli
eye spots
23
HYDROZOAN POLYP SOLITARY
Found in tropical
freshwater
Reproduce by budding
Amazing regenerative
powers
24
HYDROZOAN POLYP COLONY
• Each polyp called a zooid and will share the
gastrovascular cavity with the rest of the colony
• Individual polyps take on different roles in the colony,
similar to cells taking on different types
• Gastrozooids
• Gonozooids
• Dactylozooids
25
26
UNIQUE HYDROZOAN BODY
PLANS
• Floating colonies = Siphonophores
• E.g. Man-o-war, “Sailor jellies”
• Typically have a structure that provides buoyancy
while clusters of polyps hang beneath
27
“SAILOR JELLIES”
After a big storm, it is not uncommon to find
these Velella velella washed up in Tofino
28
See the same polyp differentiation as in non-moving colonies
“SAILOR JELLIES”
29
HYDROCORALS
• Also called fire corals
• Very well developed
dactylozooids that really hurt
to step on
• Are Hydrozoans that are polyp
dominant!
30
CLASS ANTHOZOA
• No medusa stage at any point in life
• All polyps or colonies of polyps
• Usually have well developed feeding tentacles
with nematocysts
31
GENERAL
A N T H O Z OA N B O DY
PLAN (ANEMONE)
• Tentacles for feeding and
defence
• Muscular column
• Pedal disc attached to
substrate
32
C AN ANEMONES MOVE?
Stompia
33
GENERAL ANTHOZOAN BODY
PLAN (CORALS)
Polyps are like mini anemones
34
35
YES, WE HAVE CORALS IN BC
36
CORAL REPRODUCTION
37
CORAL SYMBIONTS
Remember
Symbiodinium the
dinoflagellate?
Who gets what?
38
PHYLUM CTENOPHORA
• Defining characteristics: rows of cilia plates, adhesive preycapture cells called colloblasts
• Marine
• Almost exclusively predatory and planktonic
• Recent evidence places them as triploblastic, fate of the
blastopore not established, coelom type not established
39
40
Are considered Eumetazoans like Cnidarians but the
position of this phylum is disputed
Eumetazoa = True tissues
Metazoa = Animalia
41
GENERAL MORPHOLOGY
“KINDA SORTA JELLYFISH”
Anus
Fused cilia plates
Mouth
Tentacles are
rooted in a
tentacle sheath
and covered in
sticky colloblasts
cells
42
BODY
SYMMETRY
Biradial rather than radial
43
44
For studying
SUMMARY SLIDE
• Phylum: Cnidaria
• Clades of interest: Metazoa, Eumetazoa
• Classes (4): Anthozoa, Hydrozoa, Cubozoa, Scyphozoa
• Differ in body plan (polyp versus medusa)
• Diploblastic, cannot determine fate of blastopore, cannot
define the type of coelom
45
For studying
SUMMARY SLIDE
• Phylum: Ctenophora
• Clades of interest: Metazoa, Eumetazoa
• Classes (2): Don’t need to know
• Recent evidence places them as triploblastic, fate of the
blastopore not established, coelom type not established
46
BIOL 121A
INTRODUCTORY ZOOLOGY
Topic 7 – Rotifera
1
Rotiferans are tiny creatures with some interesting features
Part of a larger group called Gnathiferans
Lophotrochozoa = No moult, spiral cleavage
Ecdysozoa = Moult
Protostomia = Mouth 1st
Deuterostomia =
Mouth 2nd, radial
cleavage
Bilateria = Bilateral symmetry, triploblastic
Eumetazoa = True tissues
Metazoa = Animalia
2
3
PHYLUM ROTIFERA
(WHEEL ANIMALS)
• Defining characteristics: Muscular pharynx with jaws
(trophi) for catching prey or attaching to substrate,
toes with adhesive glands
• Protostomes, triploblastic, bilateral,
pseudocoelomates
• Non-molting (Lophotrochozoa)
4
Mesoderm only
on one side
Rotifers
5
PHARYNGEAL JAWS (TROPHI)
Calcified structures created by specialized epithelial cells
6
ROTIFERS GROW BY EUTELY
• Mitosis ceases early in development
• As the animals grow bigger, their cells grow bigger
rather than increase in cell number
• Syncytial tissues are common
7
Remember these friends from the protist lab water samples?
8
Others have a transparent shell called a lorica
9
Lorica = diverse
10
WHERE DO THEY LIVE?
• 95% freshwater
• Densities up to 5000 individuals per L
• 5% marine
11
I’m one of the
tiniest animals
(~0.5 mm)
GENERAL
LIFESTYLE
• Free-living (most)
• Some motile, others are
sessile
• Short generation times (1-5
weeks)
• Capture small algae and
zooplankton
12
Feeding via coronal currents
13
Structures
for
nitrogen
excretion
Toes help them
hold on to the
substrate
14
ATTACHMENT TO THE
SUBSTRATE
• Pedal glands / cement glands secrete
sticky substance used for attachment
• Motile species hold on with one or
more toes
• Sessile species get fixed in place by the
secretions
15
They have well-developed nerve clusters (ganglia) and a simple brain
EYES
16
REPRODUCTION
• Parthenogenesis is the most common type, males are
often reduced in size or not present in the
population
• But mothers can import new bits of DNA from bacteria,
fungi and plants via lateral gene transfer
• When sexual reproduction does occur, male makes a
hole in the body wall of the female and injects sperm
17
• Rotifers are an important new
model organism for aging,
especially for lifespan extension
via dietary supplements
AGING RESEARCH
• They are small and squishy
• They have a short lifespan (as little
as 6 days)
• They reproduce asexually and
sexually (when triggered)
18
https://www.giantmicrobes.com/us/products/ro
tifer.html
19
For studying
SUMMARY SLIDE
• Phylum: Rotifera
• Clades of interest: Metazoa, Eumetazoa, Bilateria,
Protostomia, Lophotrochozoa
• Classes: Do not need to know
• Triploblastic, pseudocoelomates, protostomes
20
BIOL 121A
INTRODUCTORY ZOOLOGY
Topic 8a – Mollusca
1
Mollusca, one of the largest and most diverse invertebrate groups!
Lophotrochozoa = No moult, spiral cleavage
Ecdysozoa = Moult
Protostomia = Mouth 1st
Deuterostomia =
Mouth 2nd, radial
cleavage
Bilateria = Bilateral symmetry, triploblastic
Eumetazoa = True tissues
Metazoa = Animalia
2
https://www.mollu
scs.at/index.html
3
PHYLUM MOLLUSCA
• Defining characteristics: Mantle that secretes calcified
elements, radula in the esophagus for feeding, muscular foot
• Protostomes, triploblastic, bilateral, coelomates
• Non-Moulting (Lophotrochozoa)
• Five main taxa: Class Polyplacophora, Gastropoda, Bivalvia,
Scaphopoda, Cephalopoda
4
Coelomate
Rotifers
5
GENERAL MOLLUSC BODY PLAN
• There isn’t one!
• The mollusc body plan is highly varied and modified
among all the different groups
6
MEET HAM
DORSAL
Mantle
Visceral Mass
Shell
Gill
ANTERIOR
POSTERIOR
Mantle cavity
Foot
VENTRAL
7
KEY MOLLUSC FEATURES (TO
UNDERSTAND DIVERSITY)
1. Foot (is it still a foot?)
2. Visceral mass
3. Mantle
4. Shell(s) (how many?)
5. Position and size of mantle cavity
6. Gills (feeding, breathing, or both)
8
https://www.mollu
scs.at/index.html
Can you
recognize some
of these key
features here?
9
THE SHELL
• Calcium carbonate set in a protein matrix
• 30-70% of the shell can be proteinaceous
• Three main layers
• Outer organic = periostracum
• Middle calcium (thick) = prismatic
• Inner calcium (think) = nacreous
10
SHELL
MINERALS
Two common forms of
calcium carbonate are
calcite and aragonite
High levels of Mg2+ in
seawater promote aragonite
formation
11
OCEAN
AC I D I F I C AT I O N
• Increased
atmospheric CO2
dissolves in
seawater
• Causes excess H+
to be produced
• Reduces seawater
pH
12
As the ocean becomes more acidic, the amount of free carbonate ion decreases, making it
harder to calcify
Green line at
top = good,
green line
drops = bad
13
WHAT DOES THIS MEAN FOR
MOLLUSCS?
• Some species have a mixture of calcite and aragonite
sections that will be more stable
• However, changes in carbonate saturation will make
calcification more difficult overall
• This effect is felt mainly by larvae
14
sea pangolin (Chrysomallon squamiferum)
RARE MINERALS C AN ALSO BE
INCORPORATED
15
THE MANTLE
• Specialized epidermal tissue that secretes the organic
and inorganic portions of the shell
• If debris gets trapped between the shell and the
mantle, a pearl may form!
16
Cultured pearl removal – the bivalve isn’t hurt
17
MANTLE C AVITY
• Between the mantle and the visceral mass is a space
called mantle cavity
• Houses the gills (ctenidia)
• Provides an exit for digestive, excretory, reproduction
system
18
(blue)
ctenidia
(gut = pink)
19
CTENIDIA / CTENIDIUM /
(GILLS)
• Comb-like with lots of surface area
• Mainly for gas exchange but some species use them
for food capture / food sorting
• May be associated with sensory organ (ospharadium)
20
HOW GAS EXCHANGE WORKS
• Except squids, countercurrent exchange
One gill
lobe
Water and blood pass each
other going opposite
directions
21
MOLLUSC COELOM
• Very small, restricted to a bag-like structure
surrounding the heart and gonads
Keeps heart and gonads totally separate from the other organs
22
VISCERAL MASS
• “Blob” that includes most organs of the mollusc (not
a coelom)
23
THE RADULA
• “Tongue” made of protein and chitin, studded with
chitin teeth
• Whole structure reinforced with iron in some
species
24
Check out this radula in action!
25
Radula protrudes from radular sac
Supported by odontophore rod
26
Magnetite in the radula of some chitons makes
them ferromagnetic
27
THE
FOOT
Muscular region that
has become heavily
modified
28
For studying
SUMMARY SLIDE
• Phylum: Mollusca
• Clades of interest: Metazoa, Eumetazoa, Bilateria, Protostomia,
Lophotrochozoa
• Classes: Bivalvia, Gastropoda, Polyplacophora, Cephalopoda,
Scaphopoda
• Differ in how the main mollusc features are modified (e.g., shell)
• Triploblastic, coelomates, protostomes
29
Our task for next week is to cover these (5) classes
30
BIOL 121A
INTRODUCTORY ZOOLOGY
Topic 8b – Mollusca
1
Mollusca, one of the largest and most diverse invertebrate groups!
Lophotrochozoa = No moult, spiral cleavage
Ecdysozoa = Moult
Protostomia = Mouth 1st
Deuterostomia =
Mouth 2nd, radial
cleavage
Bilateria = Bilateral symmetry, triploblastic
Eumetazoa = True tissues
Metazoa = Animalia
2
PHYLUM MOLLUSCA
• Defining characteristics: Mantle that secretes calcified
elements, radula in the esophagus for feeding, muscular foot
• Protostomes, triploblastic, bilateral, coelomates
• Non-Moulting (Lophotrochozoa)
• Five main taxa: Class Polyplacophora, Gastropoda, Bivalvia,
Scaphopoda, Cephalopoda
3
4
REPRESENTATIVES FROM EACH
CLASS
5
CLASS POLYPLACOPHORA
CHITONS
• Defining characteristics: Shell forms 7-8 separate
plates, mantle cavity extends along sides of the foot,
many gills
• Live close to shore, only on hard substrates
• Most basal / primitive molluscs
6
MODIFICATIONS FROM HAM
• Shell = 7-8 shell valves
• Mantle = thicker, covers the entire dorsal surface,
called girdle
• Mantle cavity = larger, includes the entire space
between girdle and foot on the left and right side,
contains the ctenidia
7
MODIFICATIONS FROM HAM (2)
• Foot = reduced thickness, used for strong
attachment and crawling
• Radula = no significant modifications
8
Dorsal view
9
Ventral view
10
FEEDING
• Radula used to scrape kelps or other materials off of
rocks
• Teeth often capped by iron oxide
• Some species have an accessory boring organ to
dissolve other mollusc shells!
11
12
Internal view
Digestive, circulatory, excretory, reproductive
13
ORGAN SYSTEMS
• Circulation = open, like most molluscs
• Simple heart, a few vessels, circulates through the main
body cavity (hemocoel)
• Digestion = complete gut, compartments, associated
glands to produce enzymes
14
ORGAN SYSTEMS (2)
• Nervous system = ladder-like with reduced sensory
structures (no eyes, tentacles)
• Reproduction = separate males and females with
discrete gonads, housed in perivisceral coelom with
the heart
15
REPRODUCTION
• Separate sexes, broadcast spawning
• Have one of the very classic mollusc
larval types: the trochophore
16
Katherina tunicata
LOCAL
CRITTERS
Tonicella lineata
17
18
CLASS BIVALVIA
• Defining characteristics: Bivalve shell, loss of radula,
body flattened laterally
• Mainly marine, some freshwater
19
MODIFICATIONS FROM HAM
• Shell = hinged, bivalve shell with left and right valves
• Mantle = lines the shell
• Mantle cavity = massive, modified ctenidia for
suspension feeding
20
MODIFICATIONS FROM HAM (2)
• Foot = laterally flattened, used for digging
• Radula = lost
21
https://www.digitalatlasofancientlife.org/learn/mollusca/bivalvia/
BIVALVE SHELL BASICS
• Left and right valves hinged with a protein ligament
• Held together with one or two adductor muscles
• Clams, mussels = 2
• Oysters, scallops = 1
22
CLAM
MUSSEL
SCALLOP
2
2
1
23
ADDUCTOR MUSCLES
Pallial line points to the left? It’s the left size shell
24
Look for short siphon or big siphon
Mussels, scallops, oysters
Clams
Non-burrowing
Burrowing (WHY??)
25
Extreme fused siphon
26
BIVALVES ARE NATURAL
CLEANERS
27
FILTER FEEDING
28
SUBSTRATE INTERACTIONS
• Burrowing
• Cementing
• Sticky threads
29
0:35 Razors are some of the fastest digging clams!
30
Mussels use their foot to secrete byssal threads
31
WEIRD BIVALVE SHOUT OUT
• Freshwater mussels produce parasitic larvae called
glochidia that look like mini mussels with teeth
• Mom mussel uses a “sexy mantle” dance to attract a
fish
• Mom mussel then spits the glochidia in the fishes’
face where they attach to the gills
32
33
See Ze Franks version for a laugh NSFW:
https://www.youtube.com/watch?v=V2x8ts5STzY&ab_channel=ZeFrank
34
WEIRD BIVALVE SHOUT
OUT 2
• Ship worms (Teredinids)!
• Long, soft, naked body with mini shell
at the anterior end
• How do you think they digest the
wood?
35
36
Apparently, they eat rocks too
37
For studying
SUMMARY SLIDE
• Phylum: Mollusca
• Clades of interest: Metazoa, Eumetazoa, Bilateria, Protostomia,
Lophotrochozoa
• Classes: Bivalvia, Gastropoda, Polyplacophora, Cephalopoda,
Scaphopoda
• Differ in how the main mollusc features are modified (e.g., shell)
• Triploblastic, coelomates, protostomes
38
BIOL 121A
INTRODUCTORY ZOOLOGY
Topic 8c – Mollusca
1
Mollusca, one of the largest and most diverse invertebrate groups!
Lophotrochozoa = No moult, spiral cleavage
Ecdysozoa = Moult
Protostomia = Mouth 1st
Deuterostomia =
Mouth 2nd, radial
cleavage
Bilateria = Bilateral symmetry, triploblastic
Eumetazoa = True tissues
Metazoa = Animalia
2
PHYLUM MOLLUSCA
• Defining characteristics: Mantle that secretes calcified
elements, radula in the esophagus for feeding, muscular foot
• Protostomes, triploblastic, bilateral, coelomates
• Non-Moulting (Lophotrochozoa)
• Five main taxa: Class Polyplacophora, Gastropoda, Bivalvia,
Scaphopoda, Cephalopoda
3
4
CLASS SC APHOPODA
TUSK SHELLS
• Defining characteristics: Conical tusk shell open at both
ends, anterior adhesive feeding tentacles
• Typically live in sediments in deep water
5
6
MODIFICATIONS FROM HAM
• Shell = single, tusk shape, open at both ends
• Mantle = lines the shell
• Mantle cavity = long groove that runs parallel to the
shell, no ctenidia
7
MODIFICATIONS FROM HAM (2)
• Foot = reduced, used for digging
• Radula = no significant modifications
8
Where is my
head?
9
LIFESTYLE
• Foot burrows into substrate with the small shell
opening sticking out of the sand
• Food is captured with thin tentacles called captacula
• Brought to the mouth using cilia
10
LOC AL CULTURAL
SIGNIFIC ANCE
https://ecampusontario.pressbooks.pub/knowinghome/chapter/chapter-11/
11
CLASS GASTROPODS
SNAILS AND SLUGS
• Defining characteristics: One or no shell, visceral mass
twisted 180 degrees (torsion), protein shield on the foot
(operculum)
• Marine, freshwater, terrestrial
12
MODIFICATIONS FROM HAM
• Shell = when present (coiled or cap-like, single),
when not present (complete loss)
• Mantle = lines the shell or covers the body when
shell has been lost
• Mantle cavity = restricted to anterior region in most,
contains ctenidia
13
MODIFICATIONS FROM HAM (2)
• Foot = no significant modifications
• Radula = heavily modified in some groups
• Visceral mass = twisted so the end of the gut sits
near the head (in most)
14
Torsion folds the posterior end towards the anterior end during development
(torsion)
Mantle cavity
Dorsal
Posterior
Anterior
Ventral
15
GASTROPOD HEAD
• Very well developed with sensory tentacles and eyes
(sometimes on eyestalks)
16
Torsion (Y/N)
GASTROPOD “FLAVOURS”
Prosobranchs / Aquatic Snails (Y)
Opisthobranchs / Sea slugs
(Torsion Lost)
Pulmonates /
Land snails & slugs
(Y in snails, Lost in slugs)
17
PROSOBRANCHS
“AQUATIC SNAILS”
• Most primitive gastropods
(conches, cones, limpets, periwinkles, whelks)
• Well-developed shell with a mantle cavity twisted to
be over the head
• Shells are coiled (snails) or cap-shaped (limpets)
• Foot has proteinaceous shield, operculum
18
conch
limpet
periwinkle
cone
whelk
Aquatic snails have variable shells!
19
Operculum looks like a little trap door
20
FEEDING MODES
• Everything!
• Herbivores
• Omnivores
• Carnivores
• Parasites
21
Tegula is a common local herbivore.
22
Nucella is a common local carnivore
23
????? Who did it?
24
Moon snails use the radula and enzymes to drill perfectly round holes
25
Put the radula on a proboscis and you have a deadly weapon
26
REPRODUCTION
• Some species have separate sexes
• Others are sequential hermaphrodites
• Trochophore and veliger larval forms
27
Egg cases are common, larvae can develop inside!
28
OPISTHOBRANCHS
“SEA SLUGS”
• Marine slug gastropods
(sea hares, sea slugs, bubble shells)
• Reduced or lost shell, reduced or lost mantle cavity,
loss of operculum, reduced or lost ctenidia
• Torsion lost
29
Sea hare
Bubble
shell
Dorid
sea slug
Aeolid
sea
slug
30
Rhinophores are
analogous to the
ospharadium
31
FEEDING MODES
• Grazing on algae or animals
using the radula
• Photosynthesis?
• Suspension feeding?
32
33
Fantastic local nudi Melibe – she smells like
34
PULMONATES
“LAND SLUGS AND SNAILS”
• Land-ish gastropods
(freshwater snails, land snails, slugs)
• Shell present or lost, big mantle cavity with
vascularized “lungs”
• Operculum sometimes present
35
External view
36
REPRODUCTION
• Pulmonates are usually simultaneous hermaphrodites
• Can fertilize each other in a number of creative ways
37
Love darts
38
39
CLASS CEPHALOPODA
• Defining characteristics: Shell if present has internal
chambers, closed circulatory system, foot becomes the
head, large brain in cartilage cranium
40
Octopuses, squids, cuttlefish,
nautiluses
41
MODIFICATIONS FROM HAM
• Shell = Lost in most, when present has chambers
filled with air for buoyancy
• Mantle = Becomes very thick, covers the whole
body
• Mantle cavity = very large, includes the entire space
inside the body
42
MODIFICATIONS FROM HAM (2)
• Foot = heavily modified into the head, arms, and
tentacles (headfoot)
• Radula = present, protected by modified radular
teeth (jaws)
43
External features – lets focus on HAM modifications
44
How does this compare to the other types of cephalopods?
45
Internal features
Look how big the mantle cavity is!
46
LOTS OF MODIFICATIONS TO
SUPPORT PREDATORY LIFESTYLE
1. Big head with lots of sensory structures and
nervous system complexity
2. Powerful locomotory capacity
3. Powerful prey capture capacity
47
CEPHALOPOD NERVOUS SYSTEM
Discrete brain (1) with
remarkable sensory and
learning capabilities
Large, complex eyes
Each arm has its own
“mini brain” (8) –WHY?
48
Octopuses are “handsy” for a good reason!
49
Powerful swimming and jet propulsion
50
Studying cephalopod body plans and locomotion has led to emulation
51
BUOYANCY
Chambers filled with gas and a
little fluid
How would they sink?
52
PREY C APTURE
• Via adhesive tentacles or arms
• Octopus tentacles have muscular suction cups that can
each be individually controlled
• Painful bite via the beak (and toxins!)
53
Sometimes colour change or tools can be used to bamboozle prey
54
PUBLIC SERVICE
ANNOUNCEMENT
55
These gentle creatures are at risk from deep sea mining and oil exploitation
56
CIRCULATORY SYSTEM
• Closed system with discrete vessels
• Three hearts
• 2 branchial / gill hearts for oxygenation
• 1 systemic heart to move thing around
57
Branchial to gills to system to body and back to branchial!
Hemocyanin O2 pigment
58
Many cephalopods have egg cases, like other molluscs
59
It takes an octopus village
60
W E I R D O C TO P U S S H O U TO U T
Hi, I’m an
Argonaut
61
For studying
SUMMARY SLIDE
• Phylum: Mollusca
• Clades of interest: Metazoa, Eumetazoa, Bilateria, Protostomia,
Lophotrochozoa
• Classes: Bivalvia, Gastropoda, Polyplacophora, Cephalopoda,
Scaphopoda
• Differ in how the main mollusc features are modified (e.g., shell)
• Triploblastic, coelomates, protostomes
62
BIOL 121A, Part 2 – Deuterostomes
• Email: Phillip.Morrison@viu.ca
• Office: Building 459, Room 212
• Office hours : 13:30-15:30 on Thursdays
• Email me to make appointment
• Anytime my door is open
• But not 1 hour before lecture starts
• Email if you have any questions
Gonzalez et al., 2017, Current Biology 27, 87–95
Ch. 14
Echinoderms &
Hemichordates
2
Lophotrochozoa = No moult, spiral cleavage
Ecdysozoa = Moult
Protostomia = Mouth 1st
Bilateria = Bilateral symmetry, triploblastic
Eumetazoa = True tissues
Metazoa = Animalia
Deuterostomia =
Mouth 2nd, radial
cleavage
Protostome Features (review)
Protostome = ‘first mouth’
→ blastopore becomes the mouth
Figure 3.14
4
Deuterostome Features
Deuterostome = ‘second mouth’
→ blastopore becomes the anus
Figure 3.14
5
Cladogram of Deuterostomes
6
Sea urchins (Echinodermata) are a great
model species for research on development.
Why does this make sense?
• Your development is similar to a sea urchin’s
• Sea urchins are easy to raise in the lab & produce lots of
eggs (important for medical research)
• Echinoderms are invertebrate deuterostomes – research
with vertebrates can be tricky
7
Clade Ambulacraria
Phylum Echinodermata (‘prickly skin’)
- sea stars, sea urchins, sea cucmbers etc.
Phylum Hemichordata (‘half cord’)
- acorn worms & pterobranchs
8
Phylum Echinodermata
Characteristics found in no other phylum:
1. Calcareous endoskeleton (large plates or small ossicles)
2. Water-vascular system
3. Pedicellariae
4. Dermal brachiae
5. Pentaradial symmetry in adults
Figure 14.5a
9
Phylum Echinodermata
5 main taxa
1. Class Asteroidea (‘aster’ = star) – sea stars
2. Class Ophiuroidea (‘ophi’ = snake) – brittle stars
3. Class Echinoidea (‘echin’ = spiny) sea urchins
4. Class Holothuroidea (‘holo’ = whole) – sea cucumbers
5. Class Crinoidea (‘crino’ = lily) – feather stars, sea lilies
10
Echinoderm Evolution
• Origins in early Cambrian
• Likely descended from bilateral ancestors
– larvae are bilateral
– pentaradial symmetry = derived
• Early forms: sessile with radial symmetry
• Living forms (extant): free-moving
– Class Crinoidea has sessile forms
Cambrian echinoderm fossils
Devonian echinoderm fossils
11
Cladogram of Echinoderms
12
Ecological Relationships
• Marine → cannot osmoregulate
• Intertidal to abyssal regions
• Most are benthic as adults
• Diverse feeding modes:
– suspension feeders, deposit feeders,
scavengers, predators, browsers or grazers
• Some brittle stars are commensal on sponges
• Keystone species
Deep-sea sea cucumber
“Speedy” brittle star
Filter-feeding basket star
13
Class Asteroidea: Sea Stars
• Shorelines, rocks, muddy or sandy bottoms, coral reefs
• ~ 1500 living species
• Range from 1cm – 1m across
14
Asteroid Aboral Features
• Star-shaped body with large central disc & fleshy arms (5 or more)
• Madreporite
• Anus
• Papulae (aka dermal branchiae or skin gills)
• Pedicellariae
• Spines
Aboral surface
(‘dorsal’)
Figure 14.4A
15
Asteroid Oral Features
• Mouth
• Ambulacral grooves
• Tube feet & moveable spines (border ambulacral grooves)
Oral surface
(‘ventral’)
Figure 14.4B
16
Mesodermal Endoskeleton
• Ossicles: calcareous, mesodermal plates
– joined by connective tissue (“catch collagen”)
• Catch collagen → mutable collagenous tissues
– quickly & reversibly change from soft ↔ rigid
• Stereom: meshwork that penetrates ossicles
Asteroidea: ossicles embedded in skin
• softish bodied
Echinoidea: ossicles form test/shell
• hard-bodied
17
Sea Star Internal Anatomy
Figure 14.5A
18
Sea Star Internal Anatomy
Figure 14.5
19
Figure 14.6
Pedicellariae
Functions
• Cleaning
• Protection
• Food capture
Spines
Pedicellariae
Papulae
(skin gills)
20
Coelom & Gas Exchange
• Coelom has ciliated peritoneal lining
– circulates coelomic fluid around body & into papulae
• Respiratory gases diffuse across the papulae & tube feet
– nitrogenous waste = ammonia
Cilia
Papulae
(skin gills)
Coelom
21
22
Water Vascular System
• Coelomic compartment
• Unique system of canals & tube feet
• Water vascular system + ossicles = hydraulic system
Functions:
• Locomotion
• Feeding
• Respiration & excretion
Figure 14.5B
23
Water Vascular System
See Figure 14.5B
1. Madreporite
2. Stone canal
3. Ring canal
4. Radial canal
5. Lateral canal
6. Ampulla
7. Tube feet
Polian
vesicle
24
Water Vascular System
Tube Feet & Locomotion
Ampulla
Valve
Lateral canal
Body wall
Tube feet
Retractor
muscles
• Muscle contractions
– extend & move tube feet
– create suction
Podial muscle
Sucker
25
Shape of Life
• Shape of life video
• Echinoderms: The Ultimate Animal
• https://www.shapeoflife.org/resource/aboutechinoderms
26
Feeding and Digestive System
Two-part stomach
1. Cardiac stomach (eversible)
2. Pyloric stomach
• connected to pyloric ceca (digestive glands) in arms
• digestion mostly extracellular (in pyloric ceca)
– Food broken down outside of cells, smaller nutrients absorbed
Each arm has its own set of digestive glands (pyloric ceca)
27
Asteroid Digestion
(arm & body - sagittal section)
Aboral surface
(“dorsal”)
5. Anus
3. Pyloric stomach
2. Cardiac stomach
1. Mouth
4. Digestive ceca
Oral surface
(“central”)
28
Local Sea Star Diets
Sunflower Sea Star
- Predator (sea urchins)
- Critically endangered
Leather Star
- Grazer
Purple Ochre Sea Star
- Mollusc predator
- Keystone species
29
Keystone Species
A species whose impacts on its community or
ecosystem are larger than would be expected
from its abundance.
Robert T. Paine (1933-2016)
30
Sea star - Pisaster spp., a Keystone species on Pacific coast
Sea stars present: eats mussels → high species diversity
→ low competition
Sea stars absent: mussels dominate → low species diversity
→ high competition (mussels outcompete others)
31
Nervous System
• Decentralized nervous system → no brain or cephalization
• 3 subsystems that each have:
– central nerve ring
– radial nerve
• Systems connect by nerve net
Sense organs
• Eyespot at tip of each arm
• Sensory cells scattered on skin
32
Regeneration & Autonomy
• Regenerate lost parts
• Autotomy: detach injured arm & regenerate
• Cast-off arm can regenerate new sea star
≥ 1/5 of central disc needed
Pacific Sea Star
33
Reproduction
• Separate sexes (most), some with
simultaneous hermaphroditism
• Pair of gonads in each inter-radial space
• Broadcast spawners (external fertilization)
• Brooding in some species (parental care)
→ direct development
• Free-swimming larvae (most)
34
Class Ophiuroidea: Brittle Stars & Basket Stars
• Largest class (> 2000 species)
• Distinct central disk
• Arms: slender, flexible (jointed), & brittle
35
Ophiuroid Anatomy
• No pedicellariae or papulae (skin gills)
• Ambulacral grooves: closed & covered with ossicles
• Tube feet lack suckers → feeding
– locomotion by arm movement
• Madreporite on oral surface
• Five plates → jaws
• No anus
• No intestine
• Organs in central disc
Fig. 14.12
36
Ophiuroid Reproduction (& Gas Exchange)
• 5 bursae (paired) in arm pits → open to oral surface
• Water circulation into bursae
– gas exchange
– discharge of gametes (external fertilization)
• Separate sexes (most), few hermaphroditic
Fig. 14.13
37
Ophiuroid Ecology
• Live on hard substrates where no light penetrates
• Many negatively phototropic / nocturnal
• Suspension or deposit feeders
• May use mucus to catch food
• Very fragile → regeneration & autonomy (more than sea stars)
38
Class Echinoidea
39
Class Echinoidea:
Sea Urchins, Sand Dollars, & Heart Urchins
• Test → made of ossicles that form plates
• Lack arms → test shows five-part symmetry
– ambulacral rows folded up to anus (periproct)
40
Class Echinoidea
Two types
1. Regular: most species
2. Irregular: sand dollars & heart urchins
41
Regular Urchins
• Hemispherical shape
• Pentaradial symmetry (pentaramous)
• Long spines
• Hard-rocky substrate
• Move with tube feet
• Eat algae & other organic matter (urchin barrens)
42
Irregular Urchins
• Secondarily bilateral
• Short spines
• Soft-sandy substrates
• Move mostly with spines
• Collect food particles on ciliated tracts
or with podia
Fig. 14.15
43
Echinoid Features
• Anus, madreporite & genital pores on aboral surface (“dorsal”)
• Pedicellariae: several types, some with venom glands
• Movement: spines & podia
• Aristotle’s lantern
Fig. 14.16
44
Aristotle’s Lantern
• Complex set of chewing structures
• Mouth surrounded by 5 teeth
• Ciliated siphon connect esophagus to intestine
Fig. 14.17
45
Echinoid Reproduction
• Sexes separate
• Broadcast spawners (external fertilization)
46
Sea urchins (Strongylocentrotus spp.)
Three main urchin species
in BC:
• Green
• Purple
• Red (up to 200 years)
47
Urchin roe = “uni” at sushi restaurant
48
Class Holothuroidea - Sea Cucumbers
49
Class Holothuroidea: Sea Cucumbers
• Elongated → oral-aboral axis
• Ossicles reduced & in skin → body wall is leathery
• Lack spines
• 5 rows of tube feet & muscles
50
Holothuroid Form
• Typically lie on one side
• Tube feet only well developed in three strips of ambulacra
• Oral tentacles → 10-30 modified tube feet surrounding mouth
• Secondary bilaterality is present
51
Holothuroidea Features
Oral tentacles:
modified tube
feet
Madreporite:
inside body
cavity
Coelomic cavity
→ hydrostatic
skeleton
Fig. 14.20
52
Holothuroidea Features
• Digestive system →
muscular cloaca
• Respiratory tree →
respiration &
excretion
(gas exchange also through
skin & tube feet)
• Single gonad
Fig . 14.20
53
Ecology of Sea Cucumbers
• Suspension / deposit feeders: consume suspended
particles or detritus off sea floor
• Evisceration: escape response
• Cuvierian tubules: entangle predators
Fig . 14.18
54
Sea Cucumber Feeding
55
Class Crinoidea: Sea Lilies & Feather Stars
56
Class Crinoidea
• “Primitive”
• Fossils → numerous in the past
• Attached for most of life (unique!)
• Many are deep-water species
57
Appearance & Features
• Leathery - calcareous plates
• Five arms branch out to form more arms
– each with lateral pinnules
• Sessile forms have a stalk
• Holdfast present
• Lack:
– Madreporite
– Spines
– pedicellariae
Fig. 14.21
58
59
Phylum Hemichordata
• Formerly considered a subphylum of chordates
– gill slits & rudimentary notochord (= chordate characteristic)
• “notochord” not homologous with chordates
→ evagination of mouth cavity
• Wormlike bottom-dwellers, widely distributed
60
Fig. 14.1
61
Acorn Worms
• Mucus-covered body has three parts
– proboscis + collar + trunk
• Proboscis catches food in mucous strands
• No gills → gas exchange across skin
62
Summary: Echinoderms & Hemichordates
• Deuterostomes – ‘second mouth’ (blastopore → anus)
• Different cleavage & development than Protostomes
• Includes closest invertebrate relatives to chordates.
• Clade Ambulacraria:
• Phylum Echinodermata – 5 classes, various ecological strategies
• Phylum Hemichordata – not chordates
• Echinoderm features:
• Pentaradial symmetry is secondarily derived (larvae – bilateral)
• Water vascular system
• Dermal ossicles => “endoskeleton”
• Some groups have pedicellariae
• Regeneration (autotomy)
• Catch collagen (mutable collagen)
• Ecologically, may be very important (keystone species)
63
Next …
Chordates (Ch. 15)
64
Ch 16. Fishes
Part B – Bony Fishes
Osteichthyes: Ch. 16 - Part B
Phylogeny of Fishes
Osteichthyes
• The “bony” fishes,
and tetrapods
Fig. 16.1
Cladogram of the Fishes
Fig. 16.2
Osteichthyes: Bony Fishes & Tetrapods
Three features unite bony fish & tetrapods
1. Endochondral bone replaces cartilage during development
2. Lung or swim bladder present
• Derived from gut
3. Several shared cranial and dental characters
Osteichthyes (“os” = bone; “ichthy” = fish)
•
•
Actinopterygii (“actin” = ray; “pter” = fin)
Sarcopterygii (“sarco” = flesh; “pter” = fin)
Osteichthyes
Actinopterygii
• Fins have “rays”
• ~31,000 spp.
Sarcopterygii
• Fins supported by muscle
and bones, “fleshy”
• 8 spp.
Osteichthyes – Key Adaptations
1.
Bony Operculum
• Protects gills
• ↑ H2O flow
• Streamlines body
2.
Swim bladder/Lungs
• Buoyancy or air breathing
3.
Specialized jaw musculature
• Suction feeding
Actinopterygii (ray-finned fishes)
Actinopterygii = ray-finned fishes
3 main clades
1. Cladistia (“clad” = branch; “istia” = tissue)
•
bichirs (13 spp.)
2. Chondrostei (“chond” = cartilage; “os” = bone)
•
sturgeons, paddlefish (27 spp.)
3. Neopterygii (“neo” = new, modern; “pter” = fin)
•
modern ray-finned fish (> 29,600 spp.)
1. Cladistia
- Bichirs
• Paired lungs → facultative air-breathers
• Freshwaters of Africa
• Spiracles on top of head
• Ganoid scales
– tough enamel (ganoin) & bone
• Diphycercal caudal fin
2. Chondrostei
- paddlefishes & sturgeons
2. Chondrostei
(Fig. 16.15 b, c)
“Primitive” Ray-finned fishes (sturgeons & paddlefishes)
• Skeleton mostly cartilage (derived)
• Notochord, simple vertebrae
• Intestine - spiral valve
• Ganoid scales (tough enamel & bone)
• Heterocercal caudal fin
• Ventral mouth
• Most are extinct, few extant species
So why are they bony fish?
Why are they bony fish?
Bony scutes
bony operculum
Shark or Sturgeon???
3. Neopterygii – “modern” bony fishes
Bowfin
Gars
Teleosts
Teleosts
Bowfin
Gar
Teleosts
• ~29,600 species, nearly half of all vertebrates
• Bony skeleton
• Thin scales
• Homocercal tail
• Terminal mouth
• Elaborate fins
• Jaw → suction feed
• Swim bladder
• Freshwater fish – hyperosmotic
• Saltwater fish – hypoosmotic
Teleost Scales
Thin, light, flexible:
• Thin dermal bone
• Cycloid
• Ctenoid
Fig. 16.14
Elasmobranchii
Cladisitia
Chondrostei
Neopterygii
Fig. 16.12
Osteichthyes
- Actinopterygii - ray-finned fishes
- Sarcopterygii - lobe/fleshy-finned fishes
Sarcopterygii (lobe-finned fishes)
Coelacanth (2 spp.) & Lungfish (6 spp.)
• Gills & lungs
• Fleshy fins with muscle & bone
• Diphycercal caudal fin
• Spiral valve!
• Notochord persists!
→ Extinct form gave rise to tetrapods
Fig. 16.13
Sarcopterygii
Lungfishes
Closest relatives of tetrapods
3 surviving genera
Freshwater – fish are hyperosmotic
Australian lungfish (1)
• 1 lung, but relies on gills
• Don’t survive out of water
• Endangered
African (4) & South American lungfish (1)
• 2 lungs – obligate air breathers
• Do survive out of water
• Aestivation (“hibernation”)
• Coccoon for months to years
(Also Fig. 16.18)
Sarcopterygii
Lungfishes
African Lungfish – Aestivation
• Burrows into sediment as
pool dries
• Secretes a mucous cocoon
• Dormant for months to
years
Fig. 16.18
Sarcopterygii
Coelacanth
• Though to be extinct 70 MYA
• Captured in 1938 (Africa)
• More later caught (Comoro
Island & Indonesia)
Fig. 16.19
Sarcopterygii
Coelacanth
Physiology
• Non-functional lung, filled with fat
• Marine – osmoconformer (retains urea, like elasmobranchs)
Fish Circulation
Water breathing fish (e.g., Tuna)
• Heart upstream of gills
• One-way circulation
Modifications for air-breathing in next chapter
Locomotion in Fishes
Transverse
section
W-shaped
Fig. 16.20
• Movement: trunk and tail muscles
• Myomeres:
–Zig-zag (W-shaped) muscle bands
–Attach to several vertebrae
• Alternate sides contract → tendons to tail → thrust
Locomotion
• Undulating: efficient at low speed
• Limit undulations to tail: ↓ drag
• Fast species (e.g., Tuna)
–Stiff, narrow caudal peduncle
–High aspect ratio tail (height > width)
–Movement only at tail, more efficient
Fig. 16.22
Fig. 16.21
The Lamnid-Tuna Evolutionary Convergence
• Thunniform swimming
• Endothermy
Yellowfin tuna
Shortfin mako shark
Dr. Robert Shadwick, UBC
The Lamnid-Tuna Evolutionary Convergence
Salmon Shark
Dr. Barbara Block, Stanford
Bluefin tuna
Endothermy in Teleost Fishes
Regional Endothermy or Regional Heterothermy
• ability of some fishes to maintain certain tissues or body regions
warmer than the surrounding water
• retain internally generated heat
Endothermy in Teleost Fishes
Billfish
Tuna
Opah
• Evolved at least 3 times in
teleosts (billfishes, tuna, opah)
• Mechanisms for generating and
retaining heat
‒ specialized tissues
‒ vascular countercurrent
heat exchangers (retia
mirabilia)
Significance
• Enhanced physiological
performance in colder water
• Expand thermal niche
Swordfish Brain Heater
Carey (1990) National Coalition for Marine Conservation, 103-122
Maintaining Buoyancy in Bony Fishes
• Swim bladder regulates buoyancy
• Arose from paired lungs of early Devonian fishes
–used for air-breathing in some freshwater fishes
–lung & swim bladder: homologous
–lung & gill: analogous
Fig. 16.11
Swim Bladder
Maintains neutral buoyancy
• Present in most pelagic fish (what about tuna?)
• Absent in most benthic fish
• Adjust gas volume → neutral buoyancy
• Use less energy for swimming
Types:
1. Physostomus (“open”) (“physo” = bladder; “stom” = mouth,
opening)
• Gulp & burp gas, pneumatic duct connects to gut (i.e., open)
2. Physoclistous (“closed”) (“physo” = bladder; “clist” = closed)
• Gas from blood, not connected to gut (i.e., closed)
Physostomous Swim Bladder
(Gulp & Burp Strategy)
• Swim bladder connects to esophagus
• ↑ buoyancy: gulp air
• ↓ buoyancy: burp/vent air
• Surface-dwelling fish
• E.g., salmon, trout, herring
Swim bladder
Esophagus
Physoclistous Swim Bladder
Blood O2 → bladder
Gas gland: O2 “in”
Ovale: O2 “out”
• Rete mirabile: supplies O2 to
gas gland via counter-current
flow/exchange
Fig. 16.23
• Arteries (in) and veins (out)
• Very cool and quite complex
physiology!
Physoclistous Swim Bladder
Gas Resorption
If buoyancy is too positive:
1. Ovale muscles relax
2. Gas → ovale
3. Gas diffuses → blood
4. Bladder shrinks (↓ vol)
NOTE: cannot occur quickly!
Fish Gills – Anatomy (form)
• Gill arch
• Blood vessels (capillaries)
• Gill rakers (filter feeding)
in lamellae
• Blood flow countercurrent
to water flow
• Filaments
• Lamellae
– sites of gas exchange
Fig. 16.24
Fish Respiration – physiology (function)
Countercurrent exchange
– Water & blood flow in opposite (counter) directions
– Countercurrent exchange: ↑ gas exchange very effectively
➢ Extract 85-90% of O2 from H2O
Countercurrent exchange
Water
100%
70%
40%
15%
Mouth
Out
Body
Heart
90%
60%
30%
5%
Blood
Osmoregulation in Teleost Fishes
• Osmoregulators
• Ionoregulators
Seawater (35 ppt) - concentration of
dissolved ions (mM)
Na
Cl
K
Ca
Mg
SO4
Osm
469
546
10
10
53
28
~1000
Hagfish
Shark
Coelacanth
Eel
(bony fish)
Osmoregulation
Marine vs. Freshwater Fish
Marine fish
• Fish = hypoosmotic
• Water = hyperosmotic
• Problem: fish loses water via
osmosis
Freshwater fish
• Fish = hyperosmotic
• Water = hypoosmotic
• Problem: fish gains water via
osmosis
Osmoregulation cont’d
Marine vs. Freshwater Fish
Marine fish
• hypoosmotic →“dehydrate”
• Drink seawater, minimal urine
• Cells in gills pump out ions (Na+, Cl-, K+)
• Salts removed via kidney & feces
Freshwater fish
• hyperosmotic →“explode”
• Kidneys pump out H2O, much dilute
urine
• Cells in gills pump in Na+ & Cl• NaCl intake from food
Fig. 16.25
Spawning Migrations: Definitions
Diadromy / Diadromous (“dia”= two,“dromous”= to run):
• Fish that migrate between freshwater (FW) and saltwater (SW) to
reproduce.
Anadromy / Anadromous: (“ana”= upward or against, “dromous” = to run)
Fish that migrate upstream to spawn in FW
• Fish do most feeding/growing in SW
• e.g., salmon, striped bass, shad, sturgeon
Catadromy / Catadromous: (“cata”= down or with, “dromous” = to run)
Fish that migrate downstream to spawn in SW
• Fish do most feeding/growing in FW
• e.g., eels, some gobies, some perches (barramundi)
Catadromous Migration – Freshwater Eels
• Spend most of lives in FW → migrate to sea to spawn
• Fall: adults swim downriver to the sea to spawn → none return
‒spawn once & die = semelparous
• Spring: young eels (elvers) appear in coastal waters & swim
upstream
Anadromous Migration - Pacific Salmon
• Spend adult lives at sea, return to
FW to spawn
• Semelparous: spawn once & die
• Nutrient transfer from marine to
FW and then terrestrial
environments is VERY important
for these ecosystems
➢ “Marine-derived nutrients”
Fig. 16.28
Pacific Salmon - Homing (orientation)
Return to natal stream:
• Ocean: magnetic, solar, & celestial
cues
• Nearshore: olfaction → guided by
odor of natal stream
➢Juveniles imprint on natal stream
Sockeye salmon spawning
Sockeye salmon and Kokanee
•
Life cycle of Pacific Herring
• Iteroparous (spawn multiple times)
• Age:  15 yrs
• Mature: 2 to 4 yrs
• 30,000 eggs/female/year
• Sticky eggs
• Very important in ecosystem/food chain as “forage fish” species
Reproduction in Teleosts
Eastern Mosquitofish
Diverse reproductive strategies
• Most Dioecious
• Some Monoecious
• Most Oviparous (many eggs)
Ovoviviparous
• Ovoviviparous
Banded Jawfish – Male
• Viviparous
• Parental Care (some)
Mouthbrooding
Tetrapod ancestor?
Summary – Osteichthyes (Ch. 16 – Part B)
• Evolution and classification
• Actinopterygii and Sarcopterygii
• Features and basic anatomy
• Locomotion – moving faster!
• Endothermy
• Buoyancy – going “up”? (or “down”)
• Respiration – Gills and countercurrent gas exchange
• Osmoregulation – keeping the water “in” (or “out”) to survive
• Reproduction – where and how many times
• Anadromous and catadromous
• Semelparous and iteroparous
• Sarcopterygii – Tetrapod ancestor
Ch 16. Fishes
Part A – Jawless &
Cartilaginous Fishes
1
Major Groups of Vertebrates
Vertebrates → 2 major groups
1. Agnatha:
- jawless fish ~530 mya
2. Gnathostomata:
- jawed vertebrates ~400 mya
2
Fishes are not a
monophyletic group
Fishes - all
vertebrates that are
not tetrapods
~31,000 living spp.
Fig. 16.1
3
Cladogram of the Fishes
Fig. 16.2
4
Agnathans (= “without jaws”), i.e., Jawless fishes
Early Agnathans:
Muscular pharynx → feeding & respiration
Agnathan characteristics:
1. No jaws!
2. Vertebrae reduced or absent
3. Notochord
4. Fibrous & cartilage skeleton
5. No paired fins
6. No scales
7. Indistinct stomach
5
Agnathan Groups
1. Ostracoderms – extinct groups
(“ostrac” = shell, “derm”= skin)
Fig. 15.11
2. Clade Cyclostomata – extant groups
(“cyclo” = round, “stom” = mouth)
• Clade Myxini – hagfishes
• Clade Petromyzontida - lampreys
6
Myxini - Hagfishes
• 300 mya
•  78 spp.
• Marine, benthic, deep
• Scavengers/predators
• Survive months without eating
• Almost blind – use scent & touch
• Life history poorly known
– Dioecious
– External fertilization
– Large eggs (~3 cm)
– No larval stage
7
Hagfish Physiology
• Osmoconformers
– only vertebrate that
ionoconforms to sea
water (like echinoderms)
Seawater (35 ppt) - concentration of
dissolved ions (mM)
Na
Cl
K
Ca
Mg
SO4
Osm
469
546
10
10
53
28
~1000
• Low blood pressure:
– 1 main heart
– 3 accessory hearts
8
Hagfish Feeding
• Attach: tooth-plated mouth
–teeth are keratin, not bone
• Rasp: tongue
• Leverage: knotting behaviour
Fig. 16.3
9
Hagfish Coolness
• Slime Production!!!
– Slime glands → secrete mucins & slime threads
– Slime = 99.996 % seawater
(Fig. 16.3)
10
11
Hagfish Slime
12
Petromyzontida – Lampreys
-
13
Petromyzontida – Lampreys
(“petra” = rock, “myzon” = sucking)
• 41 species globally
• <50% predators (parasitic?) (e.g., Pacific lamprey)
• Marine & fresh water
• >50% non-parasitic (e.g., brook lamprey)
• Freshwater filter-feeders
• Adults do not feed (only survive few months)
14
Petromyzontida – Lampreys
Reproduction
• All species spawn in freshwater
• builds nest in gravel
• sheds eggs and males release sperm
• Adults spawn & die – semelparous (only breed once)
15
Lamprey – Semelparous Reproduction
1. Male builds a nest
2. Nest
5. Lamprey dies
after spawning
3. Male attaches to
female’s head
4. Eggs shed into
the water as they
are fertilized
All photos taken by John Brunzell, USFWS,
16
Lamprey Development
• Eggs → ammocoete larvae
• Larvae filter feed
• Larvae: 3-7 yrs
• Endostyle proteins regulate
metamorphosis
Fig. 16.4
17
Parasitic Lamprey - Feeding
• Attach: sucker-like mouth, keratin teeth
• Rasp: flesh & suck fluids
• Anticoagulant ↑ blood flow
18
Sea Lamprey
•
Jacana/Science Source
19
Sea Lamprey problems in the Great Lakes
20
Ostracoderms
Extinct ostracoderms likely gave rise to
jawed fishes (placoderms initially)
Fig. 15.11
21
Gnathostomata (Jawed vertebrates)
• Common ancestor → jawed vertebrates
• New structures arise from existing structures
• Pharyngeal arches → jaws
•The jaw is one of the most important innovations
in vertebrate evolution
22
Fig. 16.1
23
Cladogram of the Fishes
Fig. 16.2
24
Origins of Jaws
• Modification of first two pharyngeal arches (originally gill supports)
• Mandibular arch → upper jaw (palatoquadrate) & lower jaw (Meckel’s cartilage)
• Hyoid arch → braced jaws against brain case (cranium)
• Neural crest → pharyngeal skeleton (including lower jaw)
25
Jaws – what a great innovation!!!
• Structure for grasping and manipulation
• “Armed” with teeth
‒Defense or feeding
• Feeding options
‒Carnivore (piscivore), planktivore, herbivore
‒Specialized feeders
• Ultimately, permitted an increase in size
Placoderms – 1st jawed fish
Fig. 15.12
•Bony armour
•Paired fins: provide stability
•~ 400-430 mya (Devonian – “The Age of Fishes”)
•Diverse: adaptive radiation because of jaws?
27
Devonian Period is
the “age of fishes”
Fig. 16.1
28
Cladogram of the Fishes
Fig. 16.2
29
30
class Chondrichthyes (Cartilaginous Fishes)
- “chondro” = cartilage, “ichthy”= fish
Cartilage skeleton
• Lighter than bone
• More flexible
• Stress points calcified
Two clades (subclasses):
Elasmobranchii
• Sharks, skates & rays
• > 1060 spp.
Holocephali
• chimaeras & ratfishes
• > 47 spp.
31
Elasmobranchii
- “elasmo” = plate; “branchia” = gill
- Includes Sharks, Skates & Rays
32
Shark Appearance & Features - I
1. Fusiform (not rays & skates)
2. Mouth ventral
3. 5-7 open gill slits (no operculum)
4. Placoid scales (“dermal denticles”)
Fig. 16.5
33
Shark Appearance & Features - II
5. Heterocercal tail
6. Heavier than H2O (negatively buoyant)
• No swim bladder
• Heterocercal tail - ↑ lift
• Squalene in liver - ↓ fish density
7. Keen sense of smell
Fig. 16.13
34
Shark Diversity (>500 spp.)
35
Apex Predator!!!
36
Rays & Skates ( >600 spp.)
• “Flat sharks”
• Enlarged pectoral fins
• Diverse: skates, sting rays, electric rays,
manta rays, guitarfish
• Teeth for crushing prey
• molluscs & crustaceans, sometimes fish
• Some are filter feeders
• Rays (some): Tail with poison spines
• Skates: dorsal fins & thorns
37
e.g., Mantas, Eagle Rays, River rays
38
Elasmobranch Scales: Placoid Scales
• Dermal denticles: derived from the dermis = dermal scales
• Functions: hydrodynamics (reduce drag) & protection
Placoid Scales
Enamel
Dentine
Pulp cavity
Epidermis
Fig. 16.12
Dermis
39
Placoid scales (i.e., dermal denticles)
40
Elasmobranch Teeth
- Modified scales (denticles)
→ replaceable rows of teeth
New teeth
forming
Teeth
Dermis
Epidermis
Fig. 16.5
41
Elasmobranch Digestive System
• Spiral valve – corkscrewed lower intestine
• ↑ surface area in short intestine
Spiral valve
Fig. 16.6
42
Elasmobranch Physiology
Homeostasis
•
•
•
•
Seawater (35 ppt) - concentration of
dissolved ions (mM)
Na
Cl
K
Ca
Mg
SO
Osm
4
Osmoconformers
469 546 10 10 53
28
~1000
Ionoregulators
Salt gland in rectum → secretes salts
Urea in tissues → osmoconform → osmotic concentration  SW
43
Elasmobranch Physiology
Sensing the environment
Lateral line
• Provides spatial awareness
• Neuromast cells
‒sense vibration & H2O currents
‒mechanoreceptors
Ampullae of Lorenzini
• sense (bio)electric fields
• electroreceptors
Fig 16.8
44
Respiration: Ventilation of the Gills (most fish)
• H2O in via mouth … out via gill slits/opening
H2O
Mouth
Pharynx
45
Respiration: Ventilation of the Gills (most fish)
• H2O in via mouth … out via gill slits/opening
• Batoids & some sharks have spiracles that take in water
• may prevent gill clogging in benthic species
Spiracle
46
Circulation – ‘closed’ system
Heart (all fish): 4 chambers → one-way flow
• Sinus venosus
• 1 atrium
• 1 ventricle
• Conus arterisosus
atrium
sinus venosus
➢Bulbus in bony fish
to gills
aorta
ventricle
conus arteriosus
• Deoxygenated blood: heart → gills
(gas exchange at gills ↑O2 ↓CO2 )
• Oxygenated blood: gills → body
• Fish: low blood pressure (compared to tetrapods)
• Blood flow ↑ by muscle contraction (swimming)
47
Circulation – One-way
48
Greenland shark heart
49
Elasmobranch
Reproduction
• Late age at maturity → years to decades
• Internal fertilization:
claspers (modified pelvic fin)
• Long gestation periods → up to 2 years
50
Elasmobranch Claspers
• Spines & hooks to grasp female
• Clasper siphon expels water and sperm into female's cloaca
51
Elasmobranch
Reproduction
Egg case
Oviparous: (“ovi” = egg; “parous” = give birth)
- Lay eggs (externally)
Viviparous: (“vivi” = live)
- Direct development & live birth
a) Ovoviviparous: eggs hatch inside mother
– intrauterine cannibalism (some sharks) - siblings eat
smaller embryos and unfertilized eggs
b) Placental viviparity: young nourished by placenta
– Histotrophy (stingrays) – form of matrotrophy → nutrients
from uterine secretions (“milk”)
52
Viviparity
• Sharks: 75% of species are viviparous
• Nutrition provided by mother internally for development
• Give birth to fully formed juvenile predators
Hammerhead shark
with 15 pups
removed from uterus
53
How old are sharks?
• Evolutionary age:
• Earliest sharks appeared ~400 mya
• Biological age:
• Can be long-lived (longest among vertebrates?)
• Greenland shark dated to be ~390 years old (± 120 y)
54
How big are sharks?
Whale sharks can be 10 to 15 m long
55
Shark Endothermy
Warm sharks!
• Retain internally generated heat
to maintain select body regions
warmer than the surrounding
water.
• Known as:
‒ Regional Endothermy or
‒ Regional Heterothermy
• Common thresher shark (family
Alopiidae)
• Lamnid sharks (family Lamnidae)
‒ shortfin mako, longfin mako,
salmon shark, porbeagle,
white shark
Shark Endothermy
Generate heat:
• Internalized red-muscle
Retain heat:
• Vascular countercurrent heat
exchangers (retia mirabilia)
most fish/sharks
57
Dr. Barbara Block, Stanford
Salmon sharks (Family Lamnidae)
• Endothermic
• Core body: ~25 ºC (water: 3 to 8 ºC)
• Red muscles (RM) only function at 20-30ºC
(mammal like)
• RM & stomach T independent of water T
‒Homeothermic
• Heat → strong swimming, ↑digestion & ↑
nervous activity
Bernal et al. (2005) Nature
58
Shark Conservation
• Sharks are overfished worldwide
• ~61 spp. threatened with extinction
• Late age at maturity + long gestation + small
litter sizes = popl’n decline
• Fear / miseducation
• Shark fin soup
59
Holocephali - Ratfishes & Chimaeras
• Holocephali (“holo” complete or whole, “ceph” = head)
- Ratfishes, ghost sharks, chimaeras and rabbitfishes
(c) Spotted ratfish
(Hydrolagus colliei)
Videos: https://www.youtube.com/watch?v=CV0D6G4CTio&feature=emb_logo
https://www.youtube.com/watch?v=yCsa-YLTQVQ
60
Holocephali - Ratfish
• Common ancestor w/ Elasmobranchs ~400 mya
• No placoid scales (except on claspers)
• Diet: small fish and invertebrates
• have claspers (and 1 on head called a tentaculum)
• Internal fertilization
• Upper jaw fused to cranium (unlike elasmobranchs)
• 3 large, permanent slow growing tooth plates (no “shark” teeth)
tentaculum
61
Ratfish
“Opercula”
Sharks: small fleshy gill flaps
• do not prevent backflow
• cannot draw water over gills
Ratfish: fleshy flap (“opercula”)
– may ↑ water flow & ↓ backflow
– but less effective than bony opercula
62
63
Summary: Agnatha & Chondrichthyes
• Phylum Vertebrata
• Agnatha
• Cyclostomata
‒ Myxini – Hagfishes
‒ Petromyzontida – Lampreys
• Ostracoderms (extinct)
• Gnathostomata (jaws + paired appendages)
• Placoderms (extinct)
• Chondrichthyes
‒ Elasmobranchii
‒ Holocephali
Ch. 15
Vertebrate
Beginnings:
The Chordates
Rashpal Dhillon, Rush Studio.
Phylum Chordata
Lophotrochozoa = No moult, spiral cleavage
Ecdysozoa = Moult
Protostomia = Mouth 1st
Bilateria = Bilateral symmetry, triploblastic
Eumetazoa = True tissues
Metazoa = Animalia
Deuterostomia =
Mouth 2nd, radial
cleavage
Chordate Evolution & Classification
• Name Chordata comes from the notochord
• Notochord is 1 of 5 characteristic features of
Phylum Chordata
Figure 15.1
Cladogram of Phylum Chordata
Figure 15.2
Chordate Phylogeny
Monophyletic clade:
1. Share a common
ancestor, and …
2. Includes ALL
descendants from
that ancestor
• Chordates likely
arose at base of
Cambrian period
• Divided into 3
subphyla
Figure 15.3
Phylum Chordata
Protochordates
Subphylum Urochordata (Tunicata) – sea squirts
Subphylum Cephalochordata – lancelets
Vertebrates
Subphylum Vertebrata – vertebrates
Five Chordate Characteristics
1. Notochord
2. Dorsal hollow nerve
cord (DHNC)
3. Pharyngeal slits
4. Endostyle/Thyroid
5. Postanal tail
(p. 343-344)
1. Notochord
• Flexible rod extends length of body
• Semi-rigid:
• Fibrous & elastic sheaths around
fluid-filled cells
• Functions:
• Support
• Stiffening
• Muscle attachment
• Bends without shortening
➢ permits undulatory movements
Figure 15.1
1. Notochord (cont’d)
Elastic sheath
Fibrous sheath
Fluid-filled
cells
• Persists in:
‒ protochordates
‒ jawless vertebrates
• Jawed vertebrates:
‒ 1st part of endoskeleton to
appear in embryo
→centra & intervertebral
discs
Centrum
2. Dorsal Hollow Nerve Cord
AKA Dorsal Tubular Nerve Cord
• Single, tubular cord dorsal to digestive tract
• Vertebrates: anterior end enlarges to form brain
• Cord produced in embryo by enfolding of ectodermal cells
Vertebra w/ hole (foramen) for spinal cord
3. Pharyngeal Slits
• Connect pharyngeal cavity to outside
• Form by:
• in-pocketing of ectoderm &
• evagination of endoderm of pharynx
• In aquatic chordates:
• 2 pockets break through to form pharyngeal slit
• In amniotes (reptiles, birds, & mammals)
• Pockets may not break through & pouches are formed
3. Pharyngeal Slits
Functions:
• Protochordates:
‒ filter feeding
‒ ion exchange
• 1st vertebrates:
‒ feeding, ion regulation, & respiration
‒ Vertebrate ancestor → slits bear gills
• Jawed fishes: gills → respiration & ion regulation
• Tetrapods: middle ear cavity, eustachian tube,
tonsils, parathyroid gland
4. Endostyle or Thyroid Gland
• Endostyle or thyroid gland found in all chordates
• Some cells in endostyle secrete iodinated proteins
Functions:
• Protochordates & larval lamprey → filter feeding
• Endostyle secretes mucus to trap food
• Vertebrates (including adult lamprey)
• Endostyle → Thyroid gland: homologous structures
‒ iodinated-proteins → hormones
5. Postanal Tail
• Postanal tail + musculature provide motility in protochordates
• Efficiency increased in fishes (swimming)
• Used for balance in many mammals
• smaller or vestigial in some lineages (e.g., human coccyx)
Five Chordate Characteristics
1. Notochord
2. Dorsal hollow nerve
cord (DHNC)
3. Pharyngeal slits
4. Endostyle/Thyroid
5. Postanal tail
(p. 343-344)
Subphylum Urochordata (Tunicata)
Tunicates or sea squirts
Tunicates
• ~ 3000 species in all seas at all depths
• Most are sessile as adults – some are free-living
• Swimming larvae with all 5 chordate features
• Sessile adults with only pharyngeal slits & endostyle
Adult Tunicate
• Tunic = nonliving test
• Adults lose most chordate
characteristics
• During metamorphosis
• Notochord & tail disappear
• Dorsal nerve cord reduced
• Incurrent & excurrent siphons
• Pharyngeal slits (basket)
• Endostyle: ciliated groove secretes
mucus
Figure 15.4
Tunicate
Respiration & Reproduction
Simple circulation
•Heart & 2 blood vessels
•Takes turns pumping in opposite
(2) directions
Monoecious
•Gametes out siphon
•External fertilization
Tunicate
Life Cycle
Gametes fuse
Tail lost
Figure 15.5
Dorsal nerve cord becomes
single ganglion
Subphylum Cephalochordata
Lancelets
•~ 32 species, 5 occur in North America
•~3-7 cm long
•Thin & slender – gas exchange by diffusion
•Coastal sandy bottoms
•5 chordate features throughout life
Branchiostoma
(aka Amphioxus)
Lancelet Anatomy
1.
2.
3.
4.
5.
No gills (not specialized for respiration)
No heart
No red blood cells
No brain
Dioecious
V-shaped
Figure 15.7
Lancelet Physiology
•
•
•
Closed circulatory system – no heart
Blood carries nutrients, not gases
Blood pumped by peristaltic contractions in vessel wall
–
–
Blood passes upward through branchial arteries (2 & 7) in
pharyngeal bars to paired dorsal aortas (1)
Blood distributed to tissues by capillaries, then collected in
veins (11-14) and returned to ventral aorta (8)
Branchiostoma (old name = Amphioxus)
Subphylum Vertebrata
Vertebrates
Figure 15.2
Adaptations That Guided Early
Vertebrate Evolution
Earliest Vertebrates larger & more active than protochordates
bigger → higher metabolic rate → more food
• Required (selected for) specialized structures & adaptations:
➢ find, capture, & digest food
➢ support higher metabolic rate
• Musculoskeletal modifications
• Physiological upgrades
• Brain and sensory structures
➢ Later: Paired fins and jaws
Musculoskeletal Modifications
Vertebrate Endoskeleton
• cartilage → bone
• grows with body & permits larger body size
• greater economy of building materials
• disclike centra replace notochord
• neural spines on vertebrae = muscle attachment
• V → W-shaped muscles: ↑ strength & control
Musculoskeletal Modifications
Vertebrate Exoskeleton
• Earliest fishes were partly covered in a bony, dermal armor
→ modified in later fishes as scales
• Most vertebrates are protected with keratinized structures
derived from the epidermis
→ reptilian scales, hair, feathers, claws, and horns
Physiology Upgrade
• Pharyngeal adaptations
• Gut adaptations
• Circulatory adaptations
Physiology Upgrade
Pharyngeal Adaptations
Early chordates → small & sessile
• Perforated pharynx = filter-feeding device
• Cilia flows water through pharyngeal slits & food trapped by mucus
Early vertebrates → larger & predatory
• Muscular pharynx = pump for suction feeding
• Pump forces H2O through slits: more food → larger size
• Animals became too big for O2 diffusion across skin
• Evolution of highly vascularized gills
➢ function of pharynx shifted to primarily gas exchange
Physiology Upgrade
Evolution of the vertebrate gill
• Gas exchange at skin constrains life
H+ H+
O2 H+ H+
O2
evolution
ancestral
deuterostome
early vertebrate
H+ H+
O2
early fishy vertebrate
Physiology Upgrade
Evolution of the vertebrate gill
Sackville et al., 2022. Ion regulation at gills precedes gas exchange and the origin of
vertebrates. Nature 610, 699-703.
Physiology Upgrade
Circulatory Adaptations
1. Gills
2. Chambered heart
3. Muscular blood vessels
4. Erythrocytes containing hemoglobin
➢ Enhanced transport of nutrients & respiratory gases
Efficient respiration allowed:
1.
↑ metabolic rate
2. Predatory life-style
Physiology Upgrade
Gut Adaptations
To manage increased ingestion of food
• Gut: food movement by ciliary action → muscular action
• Accessory digestive glands: liver & pancreas
➢ produce secretions that aid digestion
New Head, Brain, &
Sensory Systems
Shift from filter feeding to active predation required (selected for)
new sensory, motor, & integrative controls:
• Anterior end of nerve cord → tripartite brain
➢ brain protected by cranium (vertebrate head)
• Paired sense organs (vision, equilibrium, & sound)
• Specialized sensory structures (e.g., olfaction & electroreception)
Vertebrate head & special sense organs resulted from:
• Neural Crest & Ectodermal Placodes
➢ Embryonic innovations present only in vertebrates
43
Neural crest – Ectodermal cells lying along embryonic neural tube that
contribute to development of:
– much of the cranium
– pharyngeal skeleton (including lower jaw)
– some endocrine glands
– Schwann cells
– tooth dentine
Ectodermal placodes – Plate-like ectodermal thickenings appearing on
either side of neural tube (give rise to sensory structures)
• Initiate differentiation/development of eyes, ears, nose
‒ olfactory epithelium, lens of eye, inner ear epithelium, some ganglia, some
cranial nerves, lateral-line mechanoreceptors, and electroreceptors
IMPORTANT: Vertebrate head, with complex sensory structures
located close to mouth (later equipped with jaws), stemmed from
these new embryonic tissues
44
Ancestral Vertebrate Stock
Fossil invertebrate chordates are rare
• Burgess-Shale of Canada
• Chengjiang & Haikou in China
• Pikaia
• Burgess Shale
• ~ 5 cm
• V-shaped myomeres & notochord
= chordate
• Early cephalochordate?
• Haikouella lanceolata
• Haikou, China
• Notochord, pharynx, & dorsal nerve cord
• Pharyngeal muscles, paired eyes, & brain
• No cranium & brain not 3-lobed
➢ Not a vertebrate (sister taxon?)
45
Chordate Evolution
Chordates have taken two paths in early evolution
1. sedentary urochordates
2. active, mobile cephalochordates & vertebrates
Walter Garstang, 1928:
Was the ancestral chordate a sedentary filer feeder?
Hypothesis: the vertebrate ancestor lost the ability to
metamorphose into a sessile adult, instead developing gonads and
reproducing in the larval form (paedomorphosis)
Prediction: Cephalochordates more closely related to Vertebrates
than Urochordates (ancestral)
Vertebrate
ancestor?
47
Position of Amphioxus
Testing Garstang’s Hypothesis
Genetic, developmental, & fossil evidence:
• Cephalochordates not more closely related to Vertebrates
➢ sister taxon to Urochordates & Vertebrates (= clade)
➢ sessile Urochordates represent a derived condition
➢ amphioxus may better represent the ancestral chordate
Predicted ancestor
Reject hypothesis
Pikaia
48
Earliest Vertebrates
Myllokunmingia
Haikouichthys
Fossils from 530-500 mya
• Haikouella – eyes, brain
Figure 15.9: Haikouella
• Haikouichthys - gills, brain, eyes
• Myllokunmingia - gill bars, heart, eyes, ears
Vertebrates were present at the start of
Cambrian period ~ 530 mya
49
Conodonts – early true vertebrates?
• Fish-like (agnathan)
• Cambrian to Jurassic
• Tooth-like structures (fossils)
• 1st bones in verts? (~500 mya)
Characteristics:
– W-shaped myomeres
– Cranium
– Notochord
– Paired eyes
➢eye muscles
Figure 15.10
50
Ostracoderms
• Jawless fishes armored with bone in dermis
• Not a monophyletic group, but similar in morphology
• Fossils: late Cambrian & Devonian
• Lacked paired fins
• Muscle-powered pharyngeal skeleton (filter feeders?)
➢ filter feeders (?) & predators (?)
51
Early Jawed Vertebrates
Agnatha (“without jaw”)
• jawless vertebrates (paraphyletic)
Gnathostomata (“jaw mouth”)
• all living & extinct jawed vertebrates (monophyletic)
• pharyngeal arches → jaws
➢ new structures arise from existing structures
• “The origin of jaws was one of the most important events in
vertebrate evolution” (page 350)
52
Placoderms & Acanthodians
1st jawed fish
Fig. 15.12
• Bony armour
• Paired fins → provide stability
• ~ 400-430 mya
• Diverse in Devonian → adaptive radiation because of jaws?
• Paraphyletic groups, now extinct
– a group of placoderms → all other gnathostomes
– a group of acanthodians → cartilaginous fishes
53
Cladogram of Fishes
Fig. 16.2
54
Origins of Jaws
• Modification of first two pharyngeal arches (originally gill supports)
• Mandibular arch → upper jaw (palatoquadrate) & lower jaw (Meckel’s cartilage)
• Hyoid arch → braced jaws against brain case (cranium)
• Neural crest → pharyngeal skeleton (including lower jaw)
55
Summary: Chordate Origins
• Phylum Chordata
• Protochordates
– Subphylum Urochordata (= Tunicata) – tunicates/sea squirts
– Subphylum Cephalochordata – lancelets
• Subphylum Vertebrata
• 5 Chordate Characters
1. Notochord
2. Dorsal hollow nerve cord (DHNC)
3. Pharyngeal slits
4. Endostyle/Thyroid
5. Postanal tail
• Key steps in vertebrate evolution
• Endoskeleton/muscle changes
• Physiological upgrades (gills)
• Neural crest & ectodermal placodes
• Paired fins & jaws
Next … Fishes!!! (Ch. 16)
58
BIOL 121A
INTRODUCTORY ZOOLOGY
Topic 11c – Arthropoda
1
Arthropoda = segmented animals that shed an external exoskeleton, ecdysis
Largest and most diverse animal phylum
Lophotrochozoa = No moult, spiral cleavage
Ecdysozoa = Moult
Protostomia = Mouth 1st
Deuterostomia =
Mouth 2nd, radial
cleavage
Bilateria = Bilateral symmetry, triploblastic
Eumetazoa = True tissues
Metazoa = Animalia
2
Subphylum
Subphylum
Subphylum
Class
3
PHYLUM ARTHROPODA
• Defining characteristics: Exoskeleton made of chitin, jointed
appendages
• 85% of all animals
• Protostomes, triploblastic, bilateral, coelomates
• Moulting (Ecdysozoa)
• Eight main taxa: Class Arachnida, Merostomata, Pycnogonida,
Chilopoda, Diplopoda, Hexapoda, Malacostraca, Thecostraca
4
3 MAIN FLAVOURS OF ARTHROPOD
SUBPHYLA
Crustaceans
Chelicerates
Insects
Spiders, scorpions
Horseshoe
crabs
Myriapods
Crabs, shrimps,
lobsters
Millipedes
Barnacles
Sea spiders
Centipedes
5
CRUSTACEANS
• Defining characteristics: Shared DNA features, similar
compound eye structures
• Hexapoda, Malacostraca, Thecostraca
6
“Insects”
7
“Non-insect crustaceans”
GENERAL FEATURES (INSECTS)
• Three tagmata
= head, thorax, and abdomen
• Source of bias for the study of arthropods,
all tagmata are defined based on how they
appear in hexapods!
8
APPENDAGES
• Antennae ( 1 set)
• Walking legs (3 pairs)
• Wings ( 2 pairs)
9
(2 pairs, usually)
(1 pair)
(3 pairs)
10
SEGMENTS (INSECTS)
• Segments 1-5 = Head
• 1 = Antennae
• 3 = Mandibles (jaws)
• 4-5 = Maxillae (mouth parts)
• Segments 6-8 = Thorax
• 6-8 = Paired walking legs, Wings on 7 and 8
11
SEGMENTS (INSECTS) 2
• Segments 8-19* = Abdomen
• Significantly reduced, could be reproductive or sensory
structures
12
CLASS HEXAPODA
INSECTS
• Defining characteristics: 3 pairs of walking legs
• Found everywhere
• All feeding modes
13
>1M species, 1500 families
Hexapods are cool – Take ENTOMOLOGY
14
INSECT
ECOLOGY
• Important community
members
• Decomposers
• Carnivores
• Herbivores
15
POLLINATION = MUTUALISM
• Entomophily, pollination by insects helps
80% of plants world-wide complete their
life cycles
• Bees and other pollinators see flowers
differently!
16
PARASITOIDS
Use other critters as a source of nutrition for their offspring
17
GENERAL FEATURES
(NON-INSECT CRUSTACEANS)
• Two tagmata
= cephalothorax and pleon
Cephalon
= cephalothorax
when fused
• Cephalon is the head
• Pereon is the thorax
• Pleon is the abdomen
18
APPENDAGES
• Antennae (2 pairs)
• Short maxillipeds to move food around
• Claws (chelipeds, 1 pair)
• Walking legs (4 pairs)
• Swimmerets (in lobsters and shrimps, not in crabs)
19
This arrangement comes from decapod crustaceans as they are most well known
SEGMENTS
(NON-INSECT CRUSTACEANS)
• Segments 1-5 = Cephalon
• 1 = Antennae 1 (short and branched)
• 2 = Antennae 2 (long and unbranched)
• 3 = Mandibles (jaws)
• 4-5 = Maxillae (mouth parts)
• Segments 6-14 = Pereon
• 6-8 = Maxillipeds
• 9-14 = Cheliped (claw) and Paired walking legs
20
SEGMENTS
(NON-INSECT CRUSTACEANS) 2
• Segments 15-19 = Pleon
• 15-18 = Pleopods (swimmerets)
• 19 = Uropod
Lobsters, shrimp, crayfish only
21
cheliped
cheliped
w1
w1
w2
w3
w4
w2
w3
w4
swimmerets
uropod
22
CLASS MALACOSTRAC A
CRABS , SHRIMPS , LOBSTERS , PRAWNS
• Defining characteristics: 20 body segments,
compound eyes placed on movable stalks
• All environments
• Largest class of crustaceans and the most diverse
collection of body plans (>40K living species)
23
24
Meet Darth Vader
25
Meet the gunslinger of the sea
26
1:30 Watch the mouthparts!
27
How to sex your crabs
28
CLASS THECOSTRACA
B ARNACLES
• Defining characteristics: Encrusting organisms with
flat calcified plates
• Marine, some free-living, others parasitic
• Head end attached to the rock (really!) and use legs
to kick food into their mouths
29
30
Feed on small planktons using feathery appendages called cirri, complete loss
of walking legs
31
BARNACLES GO TO GREAT
LENGTHS TO REPRODUCE
32
CRUSTACEANS
SUMMARY
• Body regions (Tagmata) = 3 (insects), 2 (non-insect
crustaceans)
• Characteristic appendage(s) = None
• Pairs of walking legs = 3 (insects), 4 (crabs, lobsters), lost
in barnacles
• Hexapoda, Malacostraca, Thecostraca
33
For studying
SUMMARY SLIDE
• Phylum: Arthropoda
• Clades of interest: Metazoa, Eumetazoa, Bilateria,
Protostomia, Ecdysozoa
• Classes: Arachnida, Merostomata, Pycnogonida, Chilopoda,
Diplopoda, Hexapoda, Malacostraca, Thecostraca
• Differ in appendages and body plan
• Triploblastic, coelomates, protostomes
34
BIOL 121A
INTRODUCTORY ZOOLOGY
Topic 11b – Arthropoda
1
Arthropoda = segmented animals that shed an external exoskeleton, ecdysis
Largest and most diverse animal phylum
Lophotrochozoa = No moult, spiral cleavage
Ecdysozoa = Moult
Protostomia = Mouth 1st
Deuterostomia =
Mouth 2nd, radial
cleavage
Bilateria = Bilateral symmetry, triploblastic
Eumetazoa = True tissues
Metazoa = Animalia
2
Subphylum
Subphylum
Subphylum
Class
3
PHYLUM ARTHROPODA
• Defining characteristics: Exoskeleton made of chitin, jointed
appendages
• 85% of all animals
• Protostomes, triploblastic, bilateral, coelomates
• Moulting (Ecdysozoa)
• Eight main taxa: Class Arachnida, Merostomata, Pycnogonida,
Chilopoda, Diplopoda, Hexapoda, Malacostraca, Thecostraca
4
3 MAIN FLAVOURS OF ARTHROPOD
SUBPHYLA
Crustaceans
Chelicerates
Insects
Spiders, scorpions
Horseshoe
crabs
Myriapods
Crabs, shrimps,
lobsters
Millipedes
Barnacles
Sea spiders
Centipedes
5
CHELICERATES
• Defining characteristics: Only arthropods with no
antennae, body in two sections with no distinct head,
chelicerae (first pair of appendages)
• Spiders, scorpions, horseshoe crabs, sea spiders
6
GENERAL FEATURES
• Body divided into two regions: prosoma, opisthosoma
Head + Thorax
Abdomen
(Cephalothorax)
7
Prosoma
Opisthosoma
8
APPENDAGES
• NO antennae
• Clawed appendages called chelicerae on either side
of the mouth for food ripping and predation
• Food manipulators with blunt ends called pedipalps
• Walking legs (4 pairs)
9
Legs
10
SEGMENTS
• Segments 1-6 = Prosoma
• 1 = Chelicerae
• 2 = Pedipalps
• 3-6 = Paired walking legs
• Segments 7-20 = Opisthosoma
• Heavily modified or lost
11
CLASS MEROSTOMATA
• Defining characteristics: Appendages on opisthosoma are
flattened into ‘book gills’, final segment modified into long
spike
• Only 4 living species, remained relatively unchanged for
450MY
• All marine
12
13
Meet the Horseshoe Crab
A chill predator of clams and worms
https://oceantoday.noaa.gov/fullmoonremarkablehorseshoecrab/welcome.html
14
Book gills
15
BOOK GILLS
• Series of flaps on
the abdomen that
resemble pages of a
book
• Gas exchange in
water, limited in air
16
THEY ARE THREATENED
• Their blood has the blue pigment hemocyanin and is
an essential ingredient in biomedical research
• Sells for $20,000 USD / kg
• Wild horseshoe crabs are heavy exploited
17
CLASS ARACHNIDA
• Defining characteristics:Varied opisthosoma appendages
from book lungs (internal) to spinnerets
• Mainly terrestrial
• Spiders, scorpions, mites, ticks
18
19
LIFESTYLE
• Spiders
• Solitary carnivores, usually only
interact to mate
• Scorpions
• Mainly nocturnal, solitary
carnivores, cannibalism common
• Mites / ticks
• Parasitism common, may live on
or in association with hosts
20
APPENDAGE MODIFICATIONS
• Chelicerae = preset in all, may be hollowed out for
delivery of venom (spiders mainly)
• Pedipalps = Modified into claws in scorpions, blind
end appendages in the other groups
• 4 pairs of walking legs
21
SPECIALIZED ABDOMINAL
APPENDAGES
• Opisthosoma often separated from prosoma by
narrow stalk (pedicel) in spiders
• Spiders also have abdominal appendages called
spinnerets near the anus for release of silk
• Scorpions have modified final abdominal segment into
a stinger
22
23
??
24
Cannibal scorpions – trigger warning it’s a bit spicy
25
Scorpions have two methods to capture prey: brute force (large body, big pedipalps), or
venom (small body, small pedipalps)
26
RESPIRATION
• Book gills have been modified to sit inside the
abdomen as book lungs
• Air gets in via holes call spiracles and is piped via
tracheae tubes to the lungs for gas exchange
27
28
CLASS PYCNOGONIDA
• Defining characteristics: No clear tagmata, extendible
proboscis around mouth, variable pairs of walking legs
• Marine, often deep sea
• Sea spiders
29
I look creepy but I’m actually very nice
I have a long tongue
(proboscis)
30
LIFESTYLE
• Carnivorous and
scavengers, mainly on
sessile inverts like
sponges, anemones
• They use their long
proboscis to “fish
around” inside of prey
and pull out the good
stuff
31
32
GENERAL ANATOMY
• No clear prosoma or opisthosoma, body is reduced
to a stubby trunk
• “All legs”
33
APPENDAGES
• Chelicerae are present as well as palps
• 3rd pair of appendages is special = ovigers
• Unique to this group
• 4-6 pairs of walking legs
34
Sea spider Dads are great
35
CHELICERATES
SUMMARY
• Body regions (Tagmata) = 2
• Characteristic appendage(s) = Chelicerae
• Pairs of walking legs = 4
• Spiders, scorpions, horseshoe crabs, sea spiders
36
MYRIAPODS
1000S OF LEGS
• Defining characteristics: No unique synapomorphies
but have many many legs!
• Ancestors were likely some of the first terrestrial
animals
• Centipedes, millipedes
37
38
LIFESTYLE
• Mainly detritovores
in moist terrestrial
environments
• Some predators
(centipedes)
39
40
GENERAL FEATURES
• Two tagmata
= head and trunk
• Trunk is comprised of
elongated thorax and
reduced abdomen
• How did this compare
to the chelicerates?
41
SEGMENTS
• Segments 1-5 = Head
• 1 = Antennae
• 2 = Lost during development
• 3 = Mandibles (jaws)
• 4 = Maxilla 1 (flappy mouth parts)
• 5 = Maxilla 2 (stringy mouth parts)
• Segments 6 onwards = Trunk
• 6 = Maxillipeds (centipedes)
• Paired walking legs (10s to 100s)
42
MOUTH
PARTS
• Flappy primary
maxillae form the
lower lip
• Mandibles / jaws are
inside the mouth
43
RESPIRATION
• Openings to the
outside = spiracles
• Connected to the
inside via tracheal
system that delivers O2
to the tissues
44
EXCRETION
• Malpighian tubules = tubules extending
from the back of the gut
• Absorb solutes and wastes from
hemolymph
• Passes solid nitrogenous waste to the gut
for excretion
45
CLASS CHILOPODA
CENTIPEDES
• One pair of walking legs per segment, spiracles on
the top or side of the body
• All venomous
• Predatory
46
47
APPENDAGE MODIFICATIONS
• 1st pair trunk / thoracic appendages (maxillipeds) modified
for venom delivery
48
IMPORTANT PREDATORS
Large centipede in the South Pacific feeds
on seabird chicks
Important for nutrient cycling to transfer
“marine” nutrients to a terrestrial
ecosystem
Cormocephalus coynei
49
CLASS DIPLOPODA
MILLIPEDES
• Two pairs of walking legs per segment, spiracles on the
bottom of the body
• Produce noxious chemicals as a defense
• Detritovores
50
51
APPENDAGE MODIFICATIONS
• Segments of the trunk are fused together in pairs, resulting
in two sets of walking legs per trunk segments
52
DEFENSE MECHANISMS
• Unlike centipedes, millipedes can’t bite and are slow moving
• Option 1 = defense coil
53
DEFENSE MECHANISMS
• Unlike centipedes, millipedes can’t bite and are slow moving
• Option 2 = release noxious chemicals through holes along
the side of their bodies
• Including cyanide!
54
Lemurs use millipede spray to get high
55
MYRMECOPHILY
• Some species of millipedes
live in close association with
ants
• Symbiotic and commensal
• Used by the ants to clear nest
space in some cases!
Family Pyrgodesmidae
56
Are these
the same as
chelicerates
?
MYRIAPODS
SUMMARY
• Body regions (Tagmata) = 2
• Characteristic appendage(s) = None
• Pairs of walking legs = Many
• Centipedes, millipedes
57
For studying
SUMMARY SLIDE
• Phylum: Arthropoda
• Clades of interest: Metazoa, Eumetazoa, Bilateria,
Protostomia, Ecdysozoa
• Classes: Arachnida, Merostomata, Pycnogonida, Chilopoda,
Diplopoda, Hexapoda, Malacostraca, Thecostraca
• Differ in appendages and body plan
• Triploblastic, coelomates, protostomes
58
BIOL 121A
INTRODUCTORY ZOOLOGY
Topic 11a – Arthropoda
1
Arthropoda = segmented animals that shed an external exoskeleton, ecdysis
Largest and most diverse animal phylum
Lophotrochozoa = No moult, spiral cleavage
Ecdysozoa = Moult
Protostomia = Mouth 1st
Deuterostomia =
Mouth 2nd, radial
cleavage
Bilateria = Bilateral symmetry, triploblastic
Eumetazoa = True tissues
Metazoa = Animalia
2
PHYLUM ARTHROPODA
• Defining characteristics: Exoskeleton made of chitin, jointed
appendages
• 85% of all animals
• Protostomes, triploblastic, bilateral, coelomates
• Moulting (Ecdysozoa)
• Eight main taxa: Class Arachnida, Merostomata, Pycnogonida,
Chilopoda, Diplopoda, Hexapoda, Malacostraca, Thecostraca
3
4
GENERAL BODY PLAN
• Segmented with fused / modified body regions for
specialized functions (tagmatization)
• Exoskeleton of chitin that must be shed by ecdysis
• Internal body cavity is a hemocoel, like molluscs
5
Different body regions called tagmata
6
EXOSKELETON STRUCTURE
• Epidermal cells secrete the exoskeleton
• Two main regions:
• Epicuticle (outer) – waxy lipoprotein
• Procuticle (inner, makes up the majority) – chitin
7
Not all exoskeletons are calcified, special layer in the procuticle
8
HARDENING THE EXOSKELETON
• Crustaceans = add Ca2CO3 into the procuticle
• All arthropods = tanning
• Protein cross-links form spontaneously in the procuticle
immediately after it is secreted by epidermal cells
9
Exoskeleton is not
uniform thickness
Joints are places
where procuticle is
extremely thin
10
ECDYSIS
Was this
true for
Nematodes?
• To increase in body size, the entire exoskeleton must
be shed at once
• Old exoskeleton is degraded by enzymes and split
open by allowing water or air in to “inflate” it
• Under neural and hormonal control
11
Y-organ in the head
Prothoracic glands in the thorax
Produces ecdysteroids to trigger moulting
12
NERVOUS SYSTEM
Complex brain and sensory structures in head region
Ventral nerve cord with metamerism (ganglia associated with body segments)
13
CIRCULATION
• Open/closed hybrid system
• Blood leaves heart through closed vessels
• Blood enter the heart via holes directly from the
hemocoel (main body cavity)
14
Closed
vessels,
blood exits
heart
Blood enters from the hemocoel / main body space
Heart usually located dorsally,
tube-like form
15
VISUAL SYSTEMS
• Two levels of complexity:
• Ocelli (small cup with light sensitive surface)
• Compound eye (filled with many stacks of lenses and
receptor cells organized into units called ommatidia)
• Can detect UV and polarized light!
16
17
Mantis shrimp take vision to the extreme
18
Using technology to visualize the world through mantis shrimp eyes
19
REPRODUCTION
• Almost exclusively sexual, some asexual, some
parthenogenesis
• Mix of internal and external fertilization
20
Many larval forms
21
Big deviation from the textbook**
3 MAIN FLAVOURS OF ARTHROPOD
SUBPHYLA
Crustaceans
Chelicerates
Insects**
Spiders, scorpions
Horseshoe
crabs
Myriapods
Crabs, shrimps,
lobsters
Millipedes
Barnacles
Sea spiders
Centipedes
Three classes
Two classes
Three classes
22
Subphylum
Subphylum
Subphylum
Class
23
For studying
SUMMARY SLIDE
• Phylum: Arthropoda
• Clades of interest: Metazoa, Eumetazoa, Bilateria, Protostomia,
Ecdysozoa
• Classes: Arachnida, Merostomata, Pycnogonida, Chilopoda,
Diplopoda, Hexapoda, Malacostraca, Thecostraca
• Differ in appendages and body plan [Hexapods deviate from
textbook classification]
• Triploblastic, coelomates, protostomes
24
BIOL 121A
INTRODUCTORY ZOOLOGY
Topic 10 – Nematoda
1
Nematoda = unsegmented round worms that shed an external cuticle, ecdysis
Lophotrochozoa = No moult, spiral cleavage
Ecdysozoa = Moult
Protostomia = Mouth 1st
Deuterostomia =
Mouth 2nd, radial
cleavage
Bilateria = Bilateral symmetry, triploblastic
Eumetazoa = True tissues
Metazoa = Animalia
2
PHYLUM NEMATODA
(ROUND WORMS)
• Defining characteristics: Paired sensory organs on the head
• Protostomes, triploblastic, bilateral, pseudocoelomates
• Moulting (Ecdysozoa)
• Parasitic and beneficial species
3
THE MOST ABUNDANT
MULTICELLULAR ANIMAL ALIVE TODAY
4
ALL HABITATS AND
LIFESTYLES
• Free-living and parasitic
• Terrestrial, aquatic, marine, in hosts
• Microscopic to 10s of cm long
5
C . ELEGANS: THE MOST FAMOUS
NEMATODE
• Caenorhabditis elegans
• Model organism for neuronal development
• First organism to have the whole genome
sequenced!
6
GENERAL BODY PLAN
• Most are 1-2 mm long, unsegmented worms
• Covered by a thick, non-living cuticle
• Made of collagen
7
CROSS SECTION
Something is missing…
8
GROWTH PATTERNS
• Nematodes can increase in size between moults!
• Only moult 4 times in their life
• Grow via eutely
9
PHYSIOLOGY
• Gas exchange by diffusion, no circulatory system
• Complete gut, metanephridia, well-developed nervous
system
• Muscles only run in one direction!
10
11
REPRODUCTION
• Many species are parthenogenic
• Others have separate sexes
12
Hookworms
PARASITIC NEMATODES
13
PARASITES ARE NOT ALL BAD…
A mild hookworm infection could be used to combat gluten intolerance
14
15
For studying
SUMMARY SLIDE
• Phylum: Nematoda
• Clades of interest: Metazoa, Eumetazoa, Bilateria,
Protostomia, Ecdysozoa
• Classes: do not need to know
• Triploblastic, coelomates, protostomes
16
BIOL 121A
INTRODUCTORY ZOOLOGY
Topic 9 – Annelida
1
Annelida = our last group in the blue box, segmented worms
Lophotrochozoa = No moult, spiral cleavage
Ecdysozoa = Moult
Protostomia = Mouth 1st
Deuterostomia =
Mouth 2nd, radial
cleavage
Bilateria = Bilateral symmetry, triploblastic
Eumetazoa = True tissues
Metazoa = Animalia
2
PHYLUM ANNELIDA
• Defining characteristics: one or more pairs of chitin bristles
(setae), most are segmented (metamerism)
• Protostomes, triploblastic, bilateral, coelomates
• Non-Moulting (Lophotrochozoa)
• Two main taxa: Class Clitellata, Polychaeta
3
Polychaetes,
earthworms,
and leeches!
4
Mesoderm only
on one side
Rotifers
Nematodes
5
METAMERISM
• Repeating body segments, each with their own
musculature, nervous system, circulatory system,
reproduction, and excretion
• Each segment contains its own coelom
6
ORGAN SYSTEMS
• Circulation
• Closed system, multiple hearts in anterior region, dorsal
and ventral blood vessels
• Digestion
• Complete gut, different compartments
7
ORGAN SYSTEMS (2)
• Nervous system
• Brain, concentrated nerve cord located ventrally
• Sensory
• Simple eyes (in polychaetes), sensory bristles made of
chitin,
8
ORGAN SYSTEMS (3)
• Excretion
• Simple kidneys (metanephridia) located in each segment
• Reproduction
• Simultaneous hermaphrodism common, two types of
gonads
9
Coelom
Dorsal blood vessel
Ventral nerve cord
Ventral blood vessel
10
Taxonomy is horrendous – we are going to deviate from the textbook a bit
Class Polychaeta
Class Clitellata
11
Phylum Annelida
Class Polychaeta
Class Clitellata
Sedentaria
TUBE WORMS
Leeches
Earthworms
Errantia
NON-TUBE WORMS
12
CLASS POLYCHAETA
• Marine segmented worms
• Most are predators and scavengers, sometimes of
vertebrates
• Some live in tubes (Sedentaria) and others are free-living
(Errantia)
13
EXTERNAL FEATURES
• Divide into three parts:
• Head (1st segment prostomium, 2nd segment
peristomium)
• Trunk (main body segments)
• Tail (fused segment at end, pygidium)
14
15
EXTERNAL (2)
• Each segment has triangular appendages called
parapodia and bristles called setae
16
EXTERNAL (3)
• Some species (scale worms) also have proteinaceous
scales on the dorsal surface
17
FEEDING
• Eversible pharynx with chitinous jaws
18
Meet the Bobbit worm
19
POLYCHAETES GET AROUND
In methane ICE
In deep sea VENTS
In Challenger Deep (10 km)
Pompeii worm
20
TUBES TUBES TUBES
21
CLASS CLITELLATA
• Freshwater or land-based segmented worms
• Hematophagous, predatory, or scavengers
• Have a shared external feature (series of fused segments
near the anterior) called the clitellum
22
EARTHWORMS
1st = Prostomium, 2nd = Peristomium, sections up to the clitellum do not show
metamerism
23
Before clitellum:
Hearts, Gonads,
Mouth, Pharynx,
Crop, Brain
In each body
segment after
clitellum:
Gut portion, paired
Metanephridium,
ventral nerve cord,
dorsal and ventral
vessel
24
FEEDING
• Earthworms
provide ecosystem
services by
bioturbating the
soil
• Makes space for
roots, and their
feces (worm
castings) provide
fertilizer
25
LEECHES
Main difference from earthworms?
Segments are only in the outer body wall
No organs duplicated, no internal segments
Clitellum is there but cannot be seen easily
26
FEEDING
• Hematophagous leech species like Hirudo medicinalis
use modified proboscis or jaws to pierce the skin
• Secrete hirudin to prevent clotting
• Blood is stored in a large crop with large gut surface
area for digestion
27
For studying
SUMMARY SLIDE
• Phylum: Annelida
• Clades of interest: Metazoa, Eumetazoa, Bilateria,
Protostomia, Lophotrochozoa
• Classes: Clitellata, Polychaeta [note deviation from
textbook]
• Differ in habitat, lifestyle, and external anatomy
• Triploblastic, coelomates, protostomes
28
“The Move on to Land”
Ch. 17 – The Early Tetrapods &
Modern Amphibians
From Water to Land in Ontogeny and Phylogeny
Ontogeny
The life cycle of frogs includes
• Production of masses of eggs
• Hatch into aquatic tadpoles
• Metaphorsis → terrestrial adult
Phylogeny
Evolutionary transition from water
to land took millions of years
2
Movement From Water to Land
Perhaps the most dramatic event in animal evolution
• Life originated in water
• Bodies are mostly water
• Cellular activities occur in water
➢ Modifications of organs, anatomy, & physiology
• Vascular plants, pulmonate snails, & tracheate arthropods made
transition earlier
Water vs. Land
– Differences & Challenges
1. Oxygen
• 20x more O2 in air
• diffuses more rapidly through air than water
• Lungs & skin → gas exchange
2. Air density
• 1000x less dense (less buoyancy & support)
• 50x less viscous or “thick”
➔ little support against gravity
➔ therefore, terrestrial vertebrates developed strong limbs
– remodeled endoskeleton for structural support
Water vs. Land (cont’d)
3. Temperature (T) regulation
• Air T fluctuates (T cycles)
➔ behaviour/physiology strategies required
Body temperature regulation (thermoregulation)
Ectothermic → heat from environment (externally generated heat)
Endothermic → heat from metabolism (internally generated heat)
Poikilothermic → body T variable – fluctuates w/ environmental T
Homeothermic → body T stable – independent of environmental T
Thermoregulatory strategies
Poikilothermy
Endothermy
Tropical fish
Ectothermy
Polar fish
Homeothermy
Water vs. Land (cont’d)
4. Habitat diversity
• ↑ habitat variety (↑ food)
➔ New unexploited habitats and resources available
➔ Radiation of new species
Plants, snails, & arthropods
Devonian Origin the Tetrapods
416 mya: bony fish diversified → many FW forms
Why move to land?
– Aquatic predators
– Terrestrial food opportunities
Characteristics that made move to land possible:
Lungs → because gills collapse & dry out in air
Nares → chemoreception & breathe in air
Paired fins → support & move body (limbs with bones & muscles)
Evolution of Air Breathing in Fishes
• Freshwater habitats are inherently unstable (low O2)
• Air-breathing evolved in multiple fish groups
Water breather
Gill-breathing fish
• Heart upstream of gas exchange organ
• One-way circulation
Air & water breather
Gills & Lungs
• e.g., Bowfin, Gar, Australian Lungfish
• Circulation to lung
• O2-rich blood from lungs, mixes with
O2-poor blood returning to the heart
Air Breathing in the Ancestral Lineage to Tetrapods
South American Lungfish
•
•
•
•
•
•
Obligate air-breathers
Increased vascularization of lung
Septation of atrium (right & left)
Partial septum in ventricle
Double circulation
Gill → CO2 excretion
Cladogram of Tetrapods
Fig 17.1
Fish vs. Amphibian Locomotion
(what upgrades were required for move to land?)
1. Fish: undulate
→ amphibians: same
- but now need to lift body off ground
2. Fish: pectoral girdle fixed to skull
→ amphibians: detached from skull
3. Fish: pelvic girdle 2 bones in body wall
→ amphibians: 3 bones fused to spine
Early Tetrapods
Eusthenopteron
• Could paddle itself
through bottom mud
• Had both lungs and
“walking” fins
385 MYA
Early Tetrapods
Tiktaalik
• Intermediate between lobefinned fishes & tetrapods
• Probably used limbs to
support body while placing
snout above water to
breathe air
• Flat body – move in water
• Finlike tail
• Pectoral (shoulder) girdle
separate from skull
375 MYA
Early Tetrapods
Acanthostega
• Had clearly formed digits
on both forelimbs and
hindlimbs
• Body dragged on the
ground
• Aquatic
365 MYA
Early Tetrapods
Ichthyostega
• Bulkier limb muscles to
walk onto land, but did
not walk very well
• Probably amphibious
365 MYA
Early Tetrapods
Limnoscelis
• An anthracosaur
• 5 digits on all limbs
300 MYA
Early Tetrapod & Amphibian Evolution
Amniotes
Fig 17.3
Lissamphiba: Modern Amphibians
(> 7,900 spp.)
Class Amphibia (= “both kinds of life”)
1. Order Gymnophiona (“naked of a snake”) – caecilians
2. Order Urodela (“tail evident”) – salamanders
3. Order Anura (“without tail”) – frogs & toads
Modern Amphibians
• > 7, 900 living species
• Ectotherms - body temp. depends on envnt’ & restricts
where they can live
• Metamorphosed adults adapted to life in air
• Modified olfactory (smell) epithelium
‒ detect airborne chemicals (odors)
‒ nares located on dorsal surface
• Ears detects sounds in air
Tied to Water
• Eggs easily desiccate → need moist environment
• Larvae have gills (or direct development)
• Cutaneous respiration (requires moist skin)
• Thin skin (lose water) → restricted to moist habitats
Caecilians: Order Gymnophiona (Apoda)
•
•
•
•
•
•
•
•
~ 200 living species
Elongate, limbless, burrowing animals
Tropical forests: South America, Africa, India, & Southeast Asia
Feed primarily on worms & small invertebrates
Many vertebrae
Long ribs
No limbs
Terminal anus
Figure 17.4
Caecilian Reproduction
•
•
•
•
•
•
Internal fertilization
Eggs deposited in moist ground near water
Aquatic larvae in some species
Laval development in egg in other species
Eggs guarded – develop in folds of body (some species)
Some species viviparous – embryos eat wall of oviduct
Figure 17.4
Salamanders: Order Urodela (Caudata)
• > 700 living species
• Tailed
• Carnivores: larvae & adult
• Limbs at right angle
- Inefficient “undulators”
Salamander Reproduction
• Aquatic larvae & terrestrial adults (most)
– some aquatic throughout life cycle
– fully terrestrial species → direct development
• Internal fertilization in most
Sperm transfer
• ♀ lays chin on ♂ tail
• ♂ drops spermatophore
• ♂ moves ahead
• ♀ picks it up in vent
27
Salamander Reproduction
• Aquatic – eggs in water
• Larva: gills & finlike tail
• Lose gills if metamorphosis occurs
• Terrestrial – eggs on land in moist places
• Parental care
• Gilled larva: hatch with lungs, lose gills
Figs 17.6
17.7
Salamander Respiration
Plethodontidae – lungless
• Gills & lungs (some with both)
• Some terrestrial groups lack lungs
– use cutaneous & buccal (mouth)
respiration
– likely evolved in cold streams
➢ lungs buoyant
➢ lots of O2
Cutaneous respiration
• Extensive vascular nets in skin
• Gas exchange: O2 & CO2
Paedomorphosis
•
•
•
•
Paedomorphosis: keep juvenile traits
Mudpuppy & Axolotl retain gills as adults
Mudpuppy does not metamorphose
Axolotl sexually matures with larval morphology
→ can metamorphose depending on conditions
Frogs & Toads: Order Anura (Salientia)
• ≈ 7,000 species
• Most common amphibian  90% of the class
• 250 mya (Triassic)
• Must live near water source
• Reproduction → water
• Water-permeable skin
• Ectotherms: prevents inhabiting polar & subarctic habitats
• Most have a tailed larval stage & tailless, jumping adults
Adult Frogs & Toads
Tail-less adults → Jumpers
• Head/neck fused
• Longer limbs (↑ leverage)
• Fewer Vertebrae (many fused)
Adaptations to Water
• Webbed feet
• Eyes & nostrils on dorsal side
• New evolutionary trend since Icthyostega
• WHY???
Respiration
• Pulmo-cutaneous
• Positive pressure breathers
Amphibian Circulation
Tetrapods:
Double circulation
1. Pulmonary circuit
2. Systemic circuit
Amphibian Heart:
• Sinus venosus
• 2 Atria
• 1 Ventricle (some mixing of blood)
• Conus arteriosus
• Pulmocutaneous circulation
Anuran Life History - Reproduction
Usually solitary until breeding season (warm season)
Breeding
•♂♂ call & attract ♀♀
• honest signal (cannot be faked)
Frog chorus
•↑ volume
•↓ predation
Mating
•♂ clasps ♀ (amplexus)
•External fertilization
Frog Life Cycle
• Breed & grow during warm seasons (Spring & Summer)
Metamorphosis
Fig. 17.16
Metamorphosis: Tadpole to Frog
Tadpole
Eggs
External gills
Internal gills
Adult
Lungs develop &
gills resorbed
Tail resorbed
Hindlimbs
Forelimbs &
adult mouth
Tadpoles
• Tadpoles look and act entirely different from adult frogs
• External gills → internal gills covered with a flap of skin
• Spiracle on left side (water enters mouth → gills → out spiracle)
• Finned tail
• Herbivores (some cannibals)
External Gill
Spiracle
42
Unusual Reproductive Strategies
Marsupial frog
Surinam frog
-carries eggs in pouch on back
-eggs embedded in brooding pouch on back
Poison dart frog
-tadpoles hatch on back and are carried
Darwin’s frog
-froglets develop in vocal pouch
44
Anuran Life History – Cold Season
Winter dormancy – hibernation in temperate climates
• Aquatic → pond mud
• Terrestrial → forest litter
• Glucose & glycerol → antifreeze in cold climates
– Protection from damaging effects of ice-crystal formation
• Reduced energy use → stored glycogen & fat
46
Hearing in Amphibians
1.
Tympanum vibrates against columella
2.
Columella – transfer vibrations → cochlea
3.
Cochlea (inner ear) – sound bends hair cells sending signals via nerve → brain
4.
Eustachian tube – equalizes pressure
Amphibians in Decline
Amphibian populations
declining due to:
– Habitat ↓
– Pollutants
– Diseases / parasites
– Exotic species
– Ozone depletion
– Noise pollution
– Unknown factors
Next ...
To become independent from water, what
did vertebrates need?
The amniotic egg → the Amniota (amniotes):
– Reptilia (nonavian reptiles)
– Aves (birds, avian reptiles)
– Mammalia
Ch. 18
Amniote Origins &
Nonavian Reptiles
Madagascar Day Gecko
Early Tetrapod & “Reptile” Evolution
Amniotes
Fig 17.3
Enclosing the Aquatic Habitat
• Animals with shell-less eggs are tied to water
• Development of shelled egg freed groups to exploit land
• Clade Amniota – lineage with amniotic egg
–Reptilia (nonavian reptiles)
–Birds (reptiles – dinosaurs)
–Mammals
Diversity of Clade Reptilia
Archosaurs
Reptilia – nonavian reptiles
• nearly 9500 species
≈320 U.S. & Canada
• The Age of Reptiles
Lepidosaurs
–Mesozoic: 165 million years
• Cretaceous mass extinction
–many lineages extinct
–Modern nonavian reptiles =
surviving lineages
Testudines
Amniotes are Monophyletic
Early diversification produced 3 patterns of fenestrae
➢anapsid (ancestral), diapsid, & synapsid
Three Reptile Groups (as seen in lab)
See Fig. 18.2 on p. 397
1. Anapsid (“an” = without, “apsis” = arch)
– No temporal opening
2. Diapsida (“di” = double)
– 2 temporal openings
3. Synapsida (“syn” = together)
– 1 temporal opening
Anapsids
• Found in earliest amniotes & modern turtles
• Probably ancestral
• ... but turtles are probably secondary anapsids
Otic notch
Diapsid Amniotes
2 temporal openings
Early diapsids gave rise to 5 clades:
1. Lepidosaurs(sprawling reptiles)
– lizards, snakes, tuataras
2. Archosaurs (legs under)
– dinosaurs, pterosaurs, crocodilians, birds
3. Sauropterygians (lizard flippers)
– plesiosarus & other extinct aquatic groups
4. Ichtyosaurs
– extinct dolphin-like forms
5. Turtles
– diapsid fenestrae lost early in turtle evolution
Synapsid Amniotes
• Single pair of temporal openings (low on cheeks)
• Mammals & extinct relatives (Pelycosaurs & Therapsids)
• Openings → large muscles (elevate lower jaw)
Dimetrodon (Pelycosaur)
270 mya
Adaptations of Amniotes
Derived features of Amniotes
1. Amniotic egg
2. Keratinized (waterproof) skin
3. Rib (costal) ventilation of the lungs
4. Stronger jaws
5. High pressure cardiovascular system
6. Water-conserving nitrogen excretion
7. ↑ brain & sensory organs
Amniote Characters
1. Amniotic egg
No longer dependent on water
Amniotic Egg
Fig 18.3
Extra-embryonic membranes (4):
1. Amnion – encloses embryo in fluid
2. Allantois –metabolic waste & gas exchange
3. Chorion – gas exchange
4. Yolk sac – food & nutrition
Amniote Characters
2. Thicker, waterproof skin
• Thicker
• Keratinized → Protection
• Less water-permeable (lipids)
Keratinized Skin
Keratin structures that project from the skin
• Hair
• Feathers
• Scales
• Claws
Reptile Scales
• Keratin (beta keratin)
• Epidermal
• Osteoderms = dermal bony plates
‒crocodiles & many lizards
• What about fish scales?
Epidermis
Dermis
Fig 18.4
Reptile Scales
• Crocodilians: scales remain throughout life
• Lizards & snakes: shed epidermis
• Turtles: add layers of keratin under scutes (= modified scales)
Amniote Characters
3. Efficient lungs
Amniote lungs:
• More complex & ↑ surface area
• Ventilation using costal (rib) muscles
Rib Ventilation of the Lungs
Amphibians = push air into lungs (buccal pumping)
Amniotes = negative pressure breathers (ribs)
Rib Ventilation of the Lungs
Aspiration
• thoracic cavity expands → negative pressure draws air in
• costal muscles or muscles pulling on liver
Amniote Characters
4. Strong jaw
Amniote Characters
5. Circulation – High Pressure Cardiovascular System
• Sinus venosus – reduced
• 2 Atria – separates deoxygenated (body) & oxygenated (lungs) blood
• Variation in ventricular separation
➢Most reptiles: 3 interconnected compartments
➢Crocodiles: 2 Ventricles (also birds & mammals)
Conus arteriosus
•Becomes pulmonary
& systemic trunks
Shunting in some reptiles
-blood bypasses lungs
Amniote Characters
6. Water-Conserving Nitrogen Excretion
• Water needed to excrete
ammonia (fish)
• Reptiles excrete concentrated
uric acid
– conserves water (resorbed in
bladder)
• Mammals excrete urea
‒ concentrated in kidneys
Amniote Characters
7. Advanced nervous & sensory systems
• Larger brain
• Good vision (optic lobe)
• Olfactory epithelium
– Snakes, lizards, & mammals
• Heat/infrared (pit vipers)
Reptilian Monophyletic Clades
Clade Archosauria: crocodilians, birds, dinosaurs, & pterosaurs
Reptilia: archosaurs, lepidosaurs, & turtles
Fig. 18.2
Nonavian Reptiles = Paraphyletic group
4 living clades: Testudines, Squamata, Sphenodonta, Crocodilia
Extinct Plesiosaurs, Ichthyosaurs, Pterosaurs, & Dinosaurs
Fig. 18.2
Testudines – Turtles
Fig. 18.2
Testudines – Turtles
Turtles
• Triassic origins ≈240 mya
• Shell: Carapace & Plastron
• Lack teeth
• Poor hearing
• Good sense of smell
• Colour vision
No teeth, but has a
keratinized plate
Fig 18.8
Turtle Shell
• Ribs & vertebrae fused to carapace
• Neck & tail vertebrae not fused
• Girdles are inside the ribs (= turtle synapomorphy)
• Negative pressure breathers
➢Uses abdominal & pectoral muscles
Turtle Reproduction
• Oviparous
• ♂ has concave plastron
• ♂ has long copulatory organ to reach
under shell
• Temperature → sex (many reptiles)
- high → ♀
- low → ♂
• Natal beach homing
- Extensive migrations in some species
Diverse Habitats & Diets
• Terrestrial, marine, freshwater
• Tropical, temperate
• Carnivores & herbivores
Marine turtles can reach large sizes
Leatherback turtle
Galápagos Tortoises
Weigh several hundred kg, and live >150 years
Fig 18.10
Local: Western Painted Turtles
Lepidosauria
Squamata - Lizards & Snakes
• 95% of all living nonavian reptiles (> 9100 species)
• Lizard & snake origins in Jurassic
• Diversified in Cretaceous
Lepidosauria
Squamata - Lizards & Snakes
Fig. 18.2
Snakes
Two specializations:
1. Extreme body elongation
•rearrangement of internal organs
2. Skull specializations
•swallow large prey
Squamate Reproduction
Most oviparous
Some viviparous
• most ovoviviparous
‒ e.g., northern alligator lizard
• rare placental viviparity
‒ e.g., garter snakes
Paired copulatory structure
− Hemipenis (pl. hemipenes)
Kinetic Skull
- moveable joints
- opens widely
Fig 18.11
➔ snake & lizard adaptive radiation
Lizards: “Lacertilia”
• Diverse: terrestrial, burrowing, aquatic, arboreal, aerial
• Carnivores, insectivores, herbivores
• Some have reduced limbs or are limbless
• Moveable eyelids (unlike snakes)
Common Wall Lizard
Western Skink
Pygmy Short Horned Lizard
Caudal Autotomy
•Tail autotomy → antipredator adaptation
•Pre-capture defense - deflects attacks
Naidenov and Allen (2021). Ecology and Evolution.11:3058–3064
Lizard Thermal Strategies
•Ectothermic – behaviorally thermoregulate
•Some seasonally endothermic
Tegus – reproductive endothermy
Komodo Dragon (Varanus komodoensis) - Monitor
The largest lizard (3 m)
Panther Chameleon (Fucifer pardalis)
Long, sticky-tipped tongue, for capturing prey
European Glass Lizard (Pseudopus apodus)
A legless lizard
Tokay Gecko (Gekko gecko)
A very vocal gecko (named after its call)
Gila Monster (Heloderma suspectum)
A highly venomous lizard (Mexican Beaded Lizard also venomous)
Northern Alligator Lizard
• Found in BC
• ~ 20 cm
• Live birth (ovoviviparous)
Caudal autotomy
Marine Iguana (Amblyrhynchus cristatus)
Marine Iguanas
• Found only on the Galápagos
Islands
• Marine – unique among extant
lizards
• Forage on marine algae
• Salt glands to excrete excess salt
Salt Glands
• Some reptiles have salt glands in head (eyes, nose, or mouth)
– Kidneys can’t handle salt influx
• Sea turtles, sea snakes, crocodiles, marine iguana & other lizards
‒ also, marine birds
• Secrete concentrated salt solution & conserve water
– eat salty animals & marine algae
Oral salt gland
(sea snakes & crocodiles)
Nasal salt gland
(lizards & birds)
Orbital salt gland
(sea turtles)
Amphisbaenians – Worm Lizards
• Fossorial (burrowing)
• Skull solid & spade shaped
• Skin forms into moving rings to grip soil (like earthworms)
• Eyes beneath skin & no ear openings
Most lack limbs
Snakes: Serpentes
• Limbless - no girdles or vestigial
• Numerous vertebrae – short & wide
➢ lateral undulations
• Ribs ↑ rigidity of vertebral column
➢ resistance to lateral stress
Snake Form & Function
• Lack external ear openings
➢ internal ears → low frequency sound
• Sensitive to vibrations
• Most have poor vision
➢ arboreal snakes → excellent vison
Lizard
Snake
Parrot Snake – arboreal
Snake Form & Function
• No moveable eyelids
• Eyes permanently covered
➢ ‘spectacle’ = transparent scale
• Rearranged internal organs
➢ left lung reduced & in front of right lung
• Kinetic skull
➢2 halves of lower jaw joined by muscle
Glottis
Snake Senses
•Jacobson’s organ
‒ roof of mouth – olfactory epithelium
‒ forked tongue collects scent
• Poorly developed sense of smell in nostrils
Snake Senses
•Pit organs: infrared receptors
• Pythons, boas, & pit vipers
• Detect <0.003 oC
• Track warm prey – direct strikes
Fig 18.22
Snake Prey Capture
• Most grab & swallow prey alive – actively forage
• Some constrict prey – ambush predators
Goat
Venomous Snakes
• < 20% of snake species
• Fangs to inject venom
• Muscles erect fangs
Snake Reproduction
• Most oviparous
• Some ovoviviparous - cool climates
• Rare viviparous - cool climates
Tuataras: Sphenodonta
• Lizard-like & live in burrows
• 1 living species
• Slow growing & long lived
‒ sexually mature 10-20 years
‒ eggs every 4 years
• Parietal eye
‒ detects changes in light intensity
‒ daily & seasonal rhythms
Archosauria
Crocodilia - Alligators, caimans, crocodiles, & gharials
Mesozoic ancestors (>200 my)
– 11 m & 3,500 kg
– Modern: 6 m & 1,000 kg
Locomotion
– Swim: undulate tail
– Slow (crawl): sprawling gait
– Fast (run): limbs under body
Crocodiles & Alligators
• Replaceable teeth in sockets
• 2° palate → divides nasal cavity from oral cavity
– Also in mammals
– Breathe when mouth full of water or food
2°
1°
Crocodile vs Alligator
Crocodile
(bottom teeth also visible/interlaced)
Alligator
(mostly top teeth visible)
Crocodilians
Nile Crocodile (Crocodylus niloticus)
American Alligator (Alligator mississipiensis)
Crocodilian Reproduction
Oviparous: 20-90 eggs buried or in mound
• Extensive parental care
• Hatchlings call
• Female guards for 2+ years
• Temperature determines sex ratio
• High → ♂
• Low → ♀
(opposite of turtles)
Archosauria
Dinosaurs & Pterosaurs
• Appeared in Triassic
• Dominated after Triassic-Jurassic
extinction
• Pterosaurs 1st flying vertebrates
66 million years ago dinosaurs went
extinct … or did they?
Ch. 19 – Birds
Snow Geese
during migration
Cretaceous mass extinction
66 mya
Non-avian dinosaurs & 75% species ➔ extinct
Archosaur survivors were ...
•Crocodiles & Birds
Clade Reptilia - Archosauria
Fig. 18.2
Origin of Birds
Birds are a group of
Theropod Dinosaurs
• Origins in early Jurassic
• Diversified in Cretaceous
> 10,500 living species
• Birds inhabit all biomes
• Feathers
- birds & other dinosaurs
Fig 19.2
Characteristics of Aves (150 my of evolution)
see box on page 416
1)
2)
3)
4)
5)
6)
7)
8)
Neck long & S-shaped
Feathers & leg scales
Forelimbs → wings (not all fly)
Hindlimbs → walk, perch, swim
Endothermic
Beak (keratin) → no teeth
Eggs
Modified skeleton
e.g., pygostyle, synsacrum, sternum
Dinosauria
3 major dinosaur clades
• Ornithischia
• Sauropodomorpha
• Theropoda
Sauropods
Dreadnoughtus
Ornithischians
Parasaurolophus
Theropods
Masiakasaurus
Three Alternative Hypotheses of Early Dinosaur Phylogeny
“Traditional”
“Alternative”
“New”
Černý, D., Simonoff, A.L. Statistical evaluation of character support reveals the instability of higher-level dinosaur phylogeny. Sci Rep 13, 9273 (2023).
Archaeopteryx
Discovered in 1861
–  147 mya
– Size of a crow
– Theropod (dinosaur) with S-shaped neck
Fig. 19.1
Archaeopteryx
Features:
Reptilian:
1. Long bony tail
2. Teeth
3. Clawed fingers
4. Abdominal ribs
Bird:
5. Feathers
6. Light skull
7. Fercula (wishbone)
Fig 19.1
But ... may not have been capable of strong upstroke
Mosaic Evolution
• Characteristics of modern birds did not appear all at once
• Transitional forms – derived & ancestral traits
• Feathers preceded birds & flight
Relationships of Theropoda (Saurischia)
Fig. 19.3
Modern Bird Groups (living birds = Neonithes)
Neognathae
(=“new jaw”)
Flying birds
(99% of birds)
Paleognathae
(=“old jaw”)
Flightless (ratite) birds
Flightlessness
Not all neognathae birds fly
Flightlessness evolved:
• In several neognathae groups → convergent evolution
• On islands → no predators → flight is energetically costly
• Flightless birds on continents → large paleognaths
– Ostrich, rhea, cassowary, emu → outrun predators
Dodo: 64 y to
extinction
Moa: 145y to
extinction
Neognathae
Paleognathae
Paleognathae: (“paleo”=old, “gnatha”=jaw)
• Ratites: (“flat ribs”, “ratis”=raft) nonflying birds
• Palate → reptilian (“old jaw”)
Elephant birds:
• extinct
1000ya
• 450 kg, 3 m
• 34 cm egg
Terror birds:
• extinct 3mya
• 1-3 m
• SA carnivore
Rhea (SA)
Kiwi (NZ)
Kakapo (NZ)
Emu (AUS)
Ostrich (Struthio camelus)
The largest living bird
Figure 19.27
Neognathae (“neo”=new, “gnatha”= jaw)
Carinates: (“carina” = keel)
Flight → adaptive radiation
Feathers
Lightweight, flexible, & strong
Epidermal – keratin
Homologous to reptile scales
Functions (4)
1. Flight
2. Aerodynamics
3. Insulation / H2O-proofing
4. Colour/display & camouflage
Eagle-owl Threat Display
Microraptor
Microraptor Threat/Courtship Display?
Feather Types
Flight
Insulation
Shape
Airflow
Colour
Waterproofing
Steering
Display
Insulation
Flight Feathers
Contour
• Covert feathers: smooth airflow (airfoil shape)
Flight
• Primary feathers: thrust
• Secondary feathers: lift
Secondary
Primary
Covert
Skeleton – Pneumatized Bones
Pneumatized Bones
• Air cavities
• Hollow but dense
– denser than mammal bone
• Stiff & strong
• Fewer bones
– fused bones
Fig. 19.6
Skeleton – Bird Skull
• Light & mostly fused (diapsid ancestor)
• Kinetic skull → upper jaw & skull
• Large braincase & orbits
33
Skeleton – Rigid Body
• Vertebrae fused
– except cervical (neck)
– Synsacrum
Synsacrum
• Furcula – fused clavicle
– flexes
– returns elastic energy
• Keel on sternum
Fig. 19.5
Skeleton – Rigid Body
• Ucinate processes
– brace ribs
Ucinate
processes
• Pygostyle
– reduced caudal vertebrae
– fused
Pygostyle
Fig. 19.5
Skeleton – Modified Forelimb Bones
Radius
Humerus
2nd Digit
Ulna
(elbow)
3rd & 4th
Digit
Forelimb highly modified for flight:
– Fewer bones & fused
Flying Vertebrates
Pterosaur
Mammal
Bird
Convergent evolution ➔ analogous structures
Flight Muscles
• Pectoralis: pulls wing ↓ stroke
– Largest of the two (power)
• Supracoracoideus: raises wing ↑ stroke
• Low center of gravity
– ↑ stability
Fig. 19.7
The secret to flight = wing camber
Bernoulli principle
Lift
Lift
(Figs. 19.13-19.15)
Flapping Flight
Downstroke = power
• Primary feathers → thrust
➢ displace air backward → propelling bird forward
Upstroke
• Little lift (most birds)
• Wings fold & return to original position (reduces drag)
Downstroke
Upstroke
Wing shapes relate to
ecological specialization
4 types of bird wings:
Fig. 19.16
Elliptical wings
• Highly maneuverable
• Low speed w/o stalling
• Quick take-off
• Low aspect ratio
‒ Length:Width (L/W)
‒ “Low” = length similar to width
• e.g., sparrows & flycatchers
High-speed wings
• Fast flyers
• Feed in flight
• Migrate long distances
• Swept-back, tapered wings
• High aspect ratio
length > width
• e.g., swallows & falcons
Swallows – high-speed wings
Active Soaring Wings
• Long-distance soarers
• Wind provides the lift
• Less maneuverable
• Slow/long take-off
• Long & narrow
• Very High aspect ratio
length >> width
• e.g., albatross,
shearwater, gannet
Passive Soaring Wings
• High life at low speed
• Often land soarers
• Wing slots reduce turbulence
• Smooth & quiet
• Low aspect ratio
• e.g., larger hawks, eagles, owls,
vultures
Legs
• Main muscles in thigh
‒ Near center of gravity
‒ Agile, slender feet
• Tendons to feet
‒ Perching & talons
• Countercurrent heat exchangers
Fig. 19.8
Bird Beaks
• Bone + keratin sheath
• Adapted to food habits
➢ form = function
Fig 19.9
Digestive System
Stomach
• Proventriculus – secretes gastric juice
• Muscular gizzard – grinds food
Crop
• Esophagus → stores food
Circulation
4-chambered heart (complete septum)
• Large → strong ventricular walls
• High metabolism & high heart rates
➢ heart rate is inverse of body size
• Turkey 100 bpm (beat per min.)
• Chickadee: sleep = 500 bpm; active = 1,000 bpm
• Hummingbird: rest = 150 bpm; active = 1, 250 bpm
Nucleated
red blood cells
Respiration
Fig. 19.10
• Negative pressure breathers
• Use air-sacs & parabronchi (lungs)
• Efficient & complex
– Adapted to high metabolism
& altitude (low O2)
• Parabronchi - finest branches of bronchi, tube-like
– Not tidal ventilators like reptiles & mammals
– Flow-through ventilation = continuous stream of oxygen
Breathing in birds
a
2 breath cycles
- follow path of 1 “packet” of air:
a→b→c→d
b
Cycle 1
a. In Air → posterior sacs
b. Out Air → lungs
c
d
Cycle 2
Fig. 19.10
c. In Air → anterior sacs
d. Out Air → exits
Excretion
• No urinary bladder
‒ Why? (think, form & function)
• Nitrogenous waste = Uric acid
‒ Concentrated in cloaca & combined
with fecal matter
• Salt glands
‒ Marine birds – drink SW
‒ Secrete sol’n 2x salinity of SW
‒ Homologous to reptiles (marine
iguanas)
Fig. 19.11
Sensory Systems
Excellent hearing & vision
• Hawk vision is 8x better than
humans
• Owl is 10x better
– Owls can also hear in “3D”
• Olfaction in some (carnivores,
sea birds, pigeons)
Migration
• Seasonal migrations (some birds)
• Seasonal productivity
– Southern wintering regions/ northern breeding regions
• Some use “flyways”
Bar-tailed Godwit
11, 000 km / 9 days
Bird
Migrations
118 species
Navigation Cues
1. Landmarks
2. Sun
3. Celestial
4. Magnetic
– Remember, need senses for all of these
signals/modalities
Reproduction
Males
• Breeding season: testes ↑ 300x
• Cloaca-cloaca contact
• Penis in ducks & ratite birds
Females
• left ovary/oviduct develops
Fig. 19.21
Mating Systems
Social Monogamy: one partner (~ 90% birds)
• One partner each breeding season
‒ lifetime monogamy in some species
• Both parents attend nest/eggs/offspring
• May mate with others
‒ ↑ genetic diversity
‒ ↑ reproductive success
‒ ↑ fitness
Mate choice: ♀ selects ♂
Mating Systems
Polygamy: > 1 mate
1. Polygyny - ♂ has many ♀ (common)
2. Polyandry - ♀ has many ♂ (rare)
Polygyny – Sage Grouse Lek
Male grouse collect at a lek (collective display ground)
Male grouse does not care for young
♂’s compete & ♀’s choose
Parental Care
Altricial
– Naked
– Dependent
Precocial
– Downy
– Mobile
– More common in ground
nesters
Fig. 19.24
Passenger Pigeon (extinct)
• 1866 - Flocks:
– 1.5 km wide x 500
km long
– 14 hours to pass
– ~3.5 billion birds
• Extinction (forced):
– Habitat loss
– Over-hunting
– Behaviour
https://www.audubon.org/magazine/mayjune-2014/why-passenger-pigeon-went-extinct
Ch. 20
Mammals
Class Mammalia (5,700 spp.)
Clade Amniota
Fig. 18.2
Evolution of Synapsids
Fig. 20.1
Earliest Synapsid Groups
➢ “Stem Mammals”
➢ paraphyletic groups
Pelycosaurs
• Differentiated teeth
Therapsids
• Erect gait with upright limbs
beneath body
Cynodonts
• Heterodont teeth
• 2° palate
• Loss of lumbar ribs → diaphragm
• Turbinates
Turbinates
• Moisten & warm-up/cooldown breath
•Found in birds & mammals
Cladogram of Synapsids
Early Mammals of Late Triassic
Small (mouse-sized), with many Mammal Features:
• Heterodont teeth & 2° palate (cynodont ancestor)
• Diphyodont dentition (replaced once)
• Lower jaw = 1 bone (Dentary bone)
– 2 other jaw bones → middle ear
• New jaw joint = squamosal-dentary joint
–defining characteristic for fossil mammals (“mammalian forms”)
The Mammalian Jaw
Squamosal
Dentary
• New joint
Heterodonty
-Sqaumosaldentary joint
• Bigger jaw muscles
• Complex jaw motions
• Occluding teeth
➢Chewing
Squamosaldentary joint
Middle ear
Anthwal and Tucker. 2022. Evolution and development of the mammalian jaw joint:
Making a novel structure. Evolution & Development;25:3–14.
More Mammal Features
• Endothermic
‒early forms probably not as warm
• Hair
• Diaphragm
• Skin glands
• Mammary glands → lactation
–probably evolved in late Triassic
• 3 ear ossicles (middle ear bones)
& ectotympanic (holds ear drum)
–modified jaw bones (better hearing)
Mammalian Circulatory System
4-chambered heart (2 atria + 2 ventricles)
• Completely separate pulmonary & systemic circuits
• Large → strong ventricular walls
Red blood Cells
• Nonnucleated & biconcave
Mammal Diversification
• Mammals diversified in Jurassic & Cretaceous
–so did insects & flowering plants
–mammal dentition & jaw → exploit new food sources
• Mammal diversity exploded in Cenozoic (dinosaurs extinct)
Mammal Clades
Prototheria (= “first wild animals”): egg-laying
Monotremata (=“one opening/hole”) (5 spp.)
Theria (= “wild animals”): live birth, no shell
Metatheria (= “after wild animals”) (>330 spp.)
• Marsupials (pouched mammals)
Eutheria (= “true wild animals”) (>6,000 spp.)
• Placental mammals
Prototheria: Monotremes
•Duck-billed platypus & echidna (4 spp.)
•Australia & New Guinea
Metatheria - Marsupials
• Kangaroos, wombats, koalas, etc
• Pouched & viviparous
• ~70% of the extant spp. → Australia
• ~ 100 spp. in South & Central America
• 1 spp. in North America (opossum)
Virginia opossum
North American marsupial
Eutheria - Placentals
•Majority of mammals (>6,000 spp.)
•Viviparous, long gestation, & placenta
•Diverse
Hair
• Keratinized protein filament (α-keratin)
• Grows from follicle (epidermal → sunk into dermis)
–grows continuously
–stops at certain length
–new hair pushes out old hair
2 kinds of hair in Pelage
Underhair
• dense & soft → insulation
Guard hair
• coarse & long → protection & colouration
Fig. 20.4
Hair - Molting
Most mammals molt (shed) periodically – humans too
• twice annually in most mammals
Snowshoe Hare
Hair Loss (not molting)
Summer coat
Winter coat
Hair - Functions
• Insulation & water proofing
– Sea otter ~ 150,000 hairs/cm2
• Camouflage or warning
• Defence
– Porcupine quills
• Tactile sense
– vibrissae (= whiskers)
Horns
• True horns: antelopes, sheep, & cattle
• Keratin sheath + bone core
• Not shed (grow continuously)
• Both sexes
Bighorn Sheep
Rams
Ewe
Alpine Ibex
Antlers
• Deer family
• Bone
• Develop beneath “Velvet”
• Shed annually (after breeding season)
• Size & complexity increases with age
• Typically, male 2° sexual character
Fig. 20.8
Other Horns
Pronghorn Antelope
• horns are like true horns
• keratinized portion is branched
• shed annually
Giraffe
• horns are like antlers
• skin covering
• not shed
Rhinocerous:
• horn = hairlike keratinized filaments
• not attached to skull
Glands
Integumentary glands → epidermis
4 main classes
1. Sweat glands
2. Scent glands
3. Sebaceous glands
4. Mammary glands
Fig. 20.4
Mammary Glands
• Females (rudimentary on males)
• Mammae (breasts) develop along milk line
• Lactation → nipples
• Monotremes lack nipples
➢ Milk patch (= pores on belly)
Echidna puggle
Milk patch
Milk Line
Food & Feeding
Mammals exploit a wide variety of food sources
• Variety of diets → modified teeth (form follows function)
• First synapsids → homodont dentition (uniform)
• Mammals → heterodont dentition (differentiated)
Mammal teeth
➢ four types
Mammalian Teeth
Heterodont dentition (different types)
• Incisors – biting, snipping (cut food)
• Canines – piercing
• Premolars & Molars
– Crush, grind, and ...
– Chew! (evolutionary innovation)
Diphyodont: 2 sets of teeth
1. Deciduous (milk/baby teeth)
2. Permanent (adult teeth)
• One set of 3rd molar – “wisdom”
Feeding Specializations
Teeth, jaws, tongue, digestive tract → adapted to feeding habits
4 general trophic categories (some other specializations)
1. Insectivores
• Insect eaters
2. Carnivores
• Meat eaters
3. Herbivores
• Plant eaters
4. Omnivores
• Plant & meat eaters
Fig. 20.11
Digestive Systems
Insectivores
• Often small - eat invertebrates
‒ shrews, moles, most bats
• Teeth with pointed cusps (pierce exoskeleton)
• Short digestive tract – no cecum
• Some large insectivores lack teeth (anteaters & pangolins)
Teeth with pointed cusps
Herbivores
2 groups
1. Browsers & Grazers (ruminants) – ungulates
2. Gnawers (nonruminants) – rodents & rabbits
Teeth
• Canines reduced/absent → diastema (gap)
• Molars broad & high-crowned (grinding)
• Rodent incisors keep growing
Herbivores
Digestion → Vertebrates lack enzyme (cellulase) to digest cellulose
• Fermentation: microbial digestion
• Long complex digestive tracts
• Fermentation chambers & cecum
• Ruminants have 4-chambered stomach
‒ microbial digestion (rumen) → cud re-chewed
• Coprophagy (eat feces) – rabbits & many rodents
Carnivores
• Foxes, dogs, weasels, cats, etc.
• Kill prey
➢ long canines & strong, clawed limbs
• Teeth for cutting meat & crushing bone
➢ bladelike premolars & molars
• High protein diet → short digestive tract
Canines
Premolars & molars
(bladelike)
Lions Feeding
Fig. 20.13
Omnivores
• Mixed diet
• Dietary opportunists
• Multipurpose teeth
➢ broad rounded molars
• pigs, raccoons, bears, most primates
Migration
Reasons:
• Resources
• Escape predators
Flight & Echolocation
Bats → only true flying mammal
• Nocturnal
Echolocation:
• Navigate & locate prey
Fig. 20.17
Reproduction
• Mating seasons (most mammals)
➢ coincide with best time to give birth & year
• Males → can copulate any time
➢ copulatory organ = penis
• Females → estrus cycle (heat)
• 3 reproductive patterns – monotremes, marsupials, placentals
Echidna 4-headed penis
Prototheria: Monotremes
• Oviparous = no gestation
‒ embryos develop 10-12 days
‒ leathery shell forms
‒ eggs laid & incubated 12 days
• Milk but lack nipples
Metatheria - Marsupials
• Shelled embryo → free in uterus
• “Hatched” embryo → uterine wall (not implanted)
‒ yolk sac (transient placenta)
• Short gestation: give birth to embryo → pouch
• Long lactation & maternal care
Virginia Opossums in Pouch
Metatheria - Marsupials
3 offspring simultaneously
1. Embryo - uterus
2. Fetus - pouch
3. Nursing young
➢ Nurse for much longer than placentals
Eutheria - Placentals
• Long gestation w/ parental care
• Embryo implants in uterine wall
➢ nourished by placenta
• Well developed at birth
• Altricial & precocial strategies
• Shorter time to weaning
Torpor
Mammals → endotherms
• Hair
• Subcutaneous fat
• Brown adipose tissue
Some mammals → Torpor
• cold-inhabiting mammals
• ↓activity & ↓metabolic rate
• Hibernation = deep torpor, or
winter torpor
↓ body
temp
The biggest…ever!!
• Blue whale
•150 tons (40 elephants)
• Tongue = size of elephant
• Heart = size of cow
• Buoyancy enables growth
Blue Whale: Heart Rate
Synapsid
Phylogeny
Fig. 20.1
Deuterostomes
Fig. 15.3
Cladogram of Phylum Chordata
Figure 15.2