The Evolution
of Animal
Diversity
What Characteristic Define an Animal?
• Eukaryotic cells
• Multicellular
• Ingestive Heterotroph
Other Common Characteristics of Animals
• Lack cell walls
• Sexual reproduction
• Diploid, except for gametes
• Excitable (nervous & muscular) tissue
• Similar embryology (blastula & gastrula)
Early embryonic development
Early embryonic development
blastula
gastrulation
gastrula
Animal Diversity
How did the animal kingdom evolve?
- Oldest fossils are 700 million years old
-Animals probably evolved from an ancestor
of a colonial choanoflagellate
protist
One hypothesis for the origin of
animals
Major Trends in Animal Evolution:
• Development of Tissue Layers
• Patterns of Body Symmetry
• Development of a Body Cavity
• Body Segmentation
Major Trends in Animal Evolution:
Development of Tissue Layers
Most animals have tissues that arise from
three embryologic tissues layers:
• Ectoderm – produce skin and nervous
system
• Endoderm – produces GI tract
• Mesoderm – produces muscle, skeleton and
most organs
Three embryologic tissue layers
Ectoderm
Endoderm
Mesoderm
Major Trends in Animal Evolution:
Patterns of Body Symmetry
• Asymmetrical
• Bilateral symmetry
• Radial symmetry
Body symmetry
Radial = any cut
through main
body axis
produces mirror
image halves
Bilateral = a
cut through
main body
axis produces
right-left
halves
Major Trends in Animal Evolution:
Development of a Body Cavity:
• Allows independent movement of body
wall
• Cushions internal organs
• Provides a hydrostatic skeleton
• Increases flexibility and mobility
Major Trends in Animal Evolution:
Development of a Body Cavity:
• Coelomate – true body cavity fully lined
with mesoderm
• Pseudocoelomate – body cavity in direct
contact with gut
• Acoelomate – lack body cavity
Acoelomate
Pseudocoelomate
Coelomate
Coelomates: Protostomes VS Deuterostomes
Protostomes:
mesoderm forms
from mass of cells
between endoderm
and ectoderm
Deuterostomes:
mesoderm forms as
outpocketing of
gastrulation cavity
Protostomes
Deuterostomes
Visualizing Protostome & Deuterostome Development
Major Trends in Animal Evolution:
Body Segmentation
• Most animals have segmented bodies
• Segmentation increases body flexibility
and mobility
Forms of asexual reproduction
• fission: splitting off of new individual from existing one,
parent cell divides into two parts
• budding: new individual grows from body of original,
can detach (solitary lifestyle) or remain attached
(colonial lifestyle)
• fragmentation: breaking of the body into several pieces,
each of which forms a complete adult (aka regeneration)
• gemmulation: release of specialized groups of cells that
are enclosed in a capsule and grow into new individuals
Sexual Reproduction
• Two haploid gametes (produced by meiosis) fuse to
form a diploid zygote.
• female gamete = ovum = unfertilized egg; usually large
and non-motile cell.
• male gamete = spermatozoan = small, usually
flagellated cell.
• Fertilization occurs in two ways:
– external fertilization -eggs & spermatozoa are shed into the
environment.
– internal fertilization -sperm are deposited or near the
female’s reproductive tract and egg and sperm unite within
the female’s body.
Phylogenetic
tree of Kingdom
Animalia
Phylum Porifera: Sponges
Probably first animals to evolve – similar to
modern colonial choanoflagellate protist
Early embryonic development
What was the distinguishing
characteristic that differentiated a true
multicellular organism and a colonial
protist?
Sponges have specialized cells that exhibit
cellular recognition but lack true tissue layers
Osculum
Epithelial cells
Porocyte cell
Noncellular
mesoglea and
skeletal
components
Anatomy of a Sponge
Choanocytes – specialized
for obtaining food
Ameobocytesspecialized for digestion,
nutrient transport, waste
disposal, skeletal component
manufacure. Can change into
other cell types.
Sponges can reproduce sexually or asexually
Sponges are hermaphrodites, producing
both sperm and eggs.
Sexual Reproduction
Motile sponge larva
Newly settled sponge
Asexual Sponge Reproduction
1. Budding
2. Gemmules
Sponge Reproduction
Sponge Classes
• Demospongae (spongin)
• Calcarea (Ca)
• Hexactinella (Si)
Major Trends in Animal Evolution:
1. Evolution of
tissue layers
Phylum Cnidaria Coelenterata):
Hydra
Jellies
Anemones
Corals
Phylum Cnidaria Characteristics:
• Radial symmetry
• True tissue layers (but only 2, not 3)
• Cnidocytes/nematocysts (stinging cells) for
prey capture
• Gastrula stage of development
• Digestive (gastrovascular) cavity
• Diversity of Living Things: Phylum Cnidaria
• Phylum Cnidaria (Jellyfish, Sea Anemones, Corals, Sea Combs)
• Phylum Cnidaria: The Stinging Animals
• Nerve Net, with nerve cells, but not
centralization/brain
• Excretion of water through specialzed cells
• Both extracellular and intracellular digestion
• One opening -2 way digestive system
• Dioecious
• Planula/ciliated larvae
Radial symmetry
Radial symmetry allows a
sessile animal to meet its
environment equally from all
sides
Arms & Camp, 1995
Early embryonic development
blastula
gastrulation
gastrula
Polyp and medusa forms of cnidarians
Medusa
Polyp
Purves et al., 1992
Cnidocytes and nematocysts
Firing Nematocysts
Brum et al., 1994
For jellies and hydra:
For anemones and corals:
A comparison of poriferans & cnidarians
Coral reefs have enormous biodiversity.
Zooxanthellae
Cnidarian Classes
• Hydrozoa fresh water hydras
• Anthozoa sea anemones, corals
• Siphonphora Portuguese Man-A-War
• Scyphozoa jellyfish
Life Cycle of a Cnidarian
Jellyfish, Coral Feeding, Coral Spawning, 2, Moon jelly
Ctenophora
“comb jellies” “sea walnuts”
•
•
•
•
Radially symmetrical w/ mesoglea
Eight rows/ “combs” of banded cilia that propel
No polyp stage
Hermaphroditic
Major Trends in Animal Evolution:
1. Evolution of
tissue layers
2. Evolution of
bilateral
symmetry
Bilateral symmetry
Only one plane of symmetry
that produces mirror-image
halves
Cephalization:
evolutionary trend toward
concentration of sensory
structures at the anterior
end
Arms & Camp, 1995
• Triploblastic- 3 embryonic layers
• Ectodermskin, nervous structures
• Endoderm- digestive tract, reproductive
• Mesoderm -
muscles, skeleton, body systems
Hallmark characteristics of flatworms:
• Bilateral symmetry
• Three tissue layers
• Acoelomates – solid bodies without a body
cavity
Phylum Platyhelminthes
 flat, thin body and there are no spaces between tissue layers
therefore no cell is far from the environment, diffusion for
circulation and respiration
 most primitive animals w/ bilateral symmetry
 bilateral symmetry allow for further specialization w/ a
dorsal and ventral end, anterior and posterior end, allows
organism to respond more immediately to environment
 "brain"-collection of nerve cells at anterior end
• "cephalization" tendency towards brain formations
• Kingdom Animalia: Phylum Platyhelminthes
• Phylum platyhelminthes: The Flatworms
Acoelomates
Solomon et al., 1996
Cestoda
(tapeworms)
Trematoda
Walls, 1982
Turbellaria
(free-living flatworms)
Walls, 1982
(flukes)
Class Turbellaria:
•
•
•
•
•
•
•
•
•
•
free living, planarians
eyespot, cilia over body surface
predatory/saprophytic
one digestive opening located ventrally medial, extendable
pharynx attached to mouth
branched digestive tract/glands
sexual and asexual reproduction: hermaphroditic &
regeneration
flame cells for water excretion & nitrogenous wastes
2 main nerves w/ side braches
no resp sys, gas exchange through surface and environment
Basic Anatomy of a Planarian
Internal anatomy of free-living
Planaria flat worm
Arms & Camp, 1995
Gastrovascular cavity
Class Trematoda: Flukes
•
•
•
•
•
•
VD.LS.4.11.14516 Life Cycle
-internal/external parasites
-attach to host w/suckers
-protective cuticle
-asexual reproduction of larvae in snail
-sexual reproduction of fluke in sheep
• -have a digestive system
• Blood Fluke Life Cycle
Figure 33.10 The life history of a blood fluke (Schistosoma mansoni)
Trematoda-parasitic
flukes
Endo-parasites of
vertebrates, have at least 2
hosts (complicated life
cycles)
Blood fluke -get from being
in water with snails and
sewage
Liver fluke- if eat uncooked
fish
Lung fluke-if eat uncooked
crab
Class Cestoda: Tapeworms
• no brain or "head"
• scolex (w/ hooks & suckers) for attaching to
intestine
• self reproduction organs (hermaphroditic)
• repeating units called proglottids
• larva consumed by 1st host, encyst in muscle, 2nd
host consumes muscle & adult form in
• intestinal tract
Cestoda-tapeworms
Endoparasites of vertebrates.
Head region (scolex) is modified
for attachment inside intestine.
No digestive system
Proglottids produce male and
female gametes at same time,
create fertilized eggs that pass
out with feces.
Host gets infected by eating
food contaminated with eggs,
(or putting contanimated fingers
in mouth).
Major Trends in Animal Evolution:
1. Evolution of
tissue layers
2. Evolution of
bilateral
symmetry
3. Development of
a pseudocoelom
Phylum Nematoda: roundworms
Animations:
Videos:
Intestinal Worms, Schistomasis Filariasis,
Filiarasis, Threadworms
Hallmark characteristics of roundworms:
• Three tissue layers
• Bilateral symmetry
• Pseudocoelom
• Complete digestive tract – one way passage of
nutrients from mouth to anus
Major Trends in Animal Evolution:
1. Evolution of tissue
layers
2. Evolution of
bilateral symmetry
3. Development of a
pseudocoelom
4. Development of a
true body cavity:
coelom
What the significance of coelom lined with
mesoderm?
Pseudocoelomate
Coelomate
Phylum Mollusca: Soft Bodied Animals
 Head/foot w/ sensory and motor organs
 Visceral mass w/ well developed organs of digestion, excretion and
reproduction
 Mantle which encloses visceral mass and secretes the shell
 Respire through gills & mantle
 Radula is a movable tooth like chitinous strip
 CaCO3 shell
 3 chambered heart, open circ system
• siphon
• N wastes removed through nephridia
• Kingdom Animalia: Phylum Mollusca
• Phylum Mollusca (Mollusks)
• Mollusks : Mollusks, such as squids and octopuses are explored in this
video segment.
• Visualizing Movement in Mollusks
• Mollusks Facts and Fun
Phylum Mollusca
gastropods
cephalopods
pelecypods
All mollusks have a similar body plan:
Class Gastropoda
• univalves; snail & slugs, abalones, limpetsFeeding
Gastropod VD.LS.4.11.20156 Radula, octopus
• mantle which secreted shell (layer of cells)
• radula, rasping feeding device
• muscular foot
• gills for gas exchange w/i mantle which absorbs O2 from
H2O
• land varieties can have a lung
• open circulatory system, tissues bathed in blood
Hemocyanin=blue
• trochophore larvae
• Leopard Slug Mating , Nudibranch
Class Pelecypoda
• bivalves: clams, mussels,
oysters, scallops
• no radula
• have 2 shells controlled by
adductor and abductor
muscles
• incurrent and excurrent
siphon
Not Just for Chowder
Class Cephalopoda
• octopus, squid, nautilus,
cuttlefish
• shell b/co internal (xcept
nautilus)
• foot evolves into flexible
arms
• closed circulatory system
for more efficient travel to
muscles
• siphon used in locomotion
Octopus Camouflage 2
Mimic Octopus
Octopus Hatching & Learning
Giant Squid
Major Trends in Animal Evolution:
Development of
segmentation
Phylum Annelida
Earthwormsterrestrial worm
movement
Polychaetes –
marine segmented
worms swimming
Leeches
Segmentation:
The combination of a true coelom that acts as
a hydrostatic skeleton and segmentation
allows for controlled directed movements.
• A skeleton gives muscles something to
contract against and allows coordinated
movement.
• Segmented circular muscles along with
longitudinally directed muscles allows for
forward directed movements.
Phylum Annelida
 Coelomate: w/ all organs suspended in the body cavity by
an attached membrane “peritoneum”
 Have a closed circulatory system w/5 hearts which pump
blood through ventral vessel and blood returns to heart
through dorsal blood vessel
 Segmented repeating body parts: metamerism
evolutionary advantage: an animals can increase in size by
adding segments and the segments can become specialized
 Locomotion through unsegmented body parts
• Body= respiratory surface (can use gills)
• Earthworm Systems
• Ecological Importance of Annelids
Class Polychaetes
(greatest variety in annelids)
• Marine, can reach up to 3
meter VD.LS.4.11.16756
Sand Mason Worm
• can be free moving or
sedentary
• Can have antennae and jaws
• Have parapodia w/ setae
VD.LS.3.20.36231 Sea Mouse
• can have external gills
• Peritoneum-mem. from inner
mesoderm holding organism
place
• Trochophore larvae: w/ apical
tuft, girdle of cilia and mouth
• Marine Worms, Plumed
Worm
Class Oligochaetes
• Digestion: food, mouth,
pharynx, crop, gizzard,
intestine
• Excretion: anus and
nephridia for N wastes
• Locomotion: muscle groups
& 2 prs or 4 setae per
segment, also to grip earth
• Reproduction:
hermaphroditic, clitellum
Class Hirudinea
• leeches
VD,LS.4.12.23455
Locomotion
• Free living and parasitic
• Parasitic species have
rasping teeth
• secrete hirudin, an
anticoagulant
NOVA Now Leeches
Giant Leech
Major Trends in Animal Evolution:
Development of
jointed appendages
Phylum Arthropoda:
Arthropod =
“jointed foot”
Jointed appendages and
a hard exoskeleton has
made arthropods the
most successful phyla
of animals.
Exoskeleton
• chitinous exoskeleton (a cuticle
secreted by underlying epidermis
that contains chitin) chitin is a
polysacchride also found in the cell
walls of fungi
• the exoskeleton serves as an armor
to protect the soft body of the insect,
as well as to aid in mobility
• this outside skeleton must be shed
periodically as the athropod grow
the shedding is called “ecdysis”
External skeleton made of chitin allowed the
arthropods to inhabit the land:
• protection
• waterproofing
• anchor site for attachment of muscles
Disadvantage of an exoskeleton :
• most be shed to allow growth (molt)
• restricts movements around joints
• limits ultimate size of the organism (heavy)
Metamorphosis
• growth accompanied by ecdysis
(molting) of the exoskeleton, can
become 33% larger than before
the shed
Incomplete Metamorphosis
• Can grow by complete or
incomplete metamorphosis
• Butterfly emerging
Complete Metamorphosis
Introduction to Arthropods
 arthro-joint
pes-foot
(greek)
 largest phylum, most successful & ubiquitous, 3x's all other
animals species
 coelomate
 exoskeleton w/ chitinous (polysaccharide) plates & hinges
which must be shed
 muscles attached to inner exoskeleton
 molting necessary, many larval stages, complete &
incomplete metamorphosis
 loss of metamerism: segments fused
 segmental structures (appendages) b/co struct & fnctally
diff.
Arthropods Videos
 modified head, thorax and abdomen (cephalothorax)
 nervous sys. w/ dorsal ant. brain -> ventral nerve
cord w/ ganglionic swellings in each segment
 open circ system, tissues bathed in blood
 dioecious
• 5 senses: compound & simple eyes, taste, smell
through pheromones, touch, hearing
Horseshoe crab, Limulus polyphemus
Orb spider, Araneus quadratus
House dust mite, Dermatophagoides sp.
Emperor scorpion, Pandinis imperator
Phylum Arthropoda:
Subphylum: Chelicerata
Solomon et al., 1996
Phylum Arthropoda:
Subphyla Aquatic Mandibulates
Class: Crustacea
Krill
http://members.aol.com/iq3d2/deep_sea/Hi_Res/Krill.jpg
Mantis shrimp larva
Gooseneck barnacle
Brum et al., 1994
Pink fairy crab
David Doubilet; National Geographic, Jan 1999
Subphyla Aquatic Mandibulates
Class Crustacea
• Carapace that covers head and thorax, 6
segments in abdomen
• Respires through gills
• N wastes excreted through green gland
• crayfish, crabs, lobsters, shrimp, Daphnia,
pillbugs, barnacles, prawns
Phylum Arthropoda:
Uniramia
Diplopods: Millipede
Praying mantis
Campbell et al., 1999
Potter 1982
Insecta
Greater stag beetle, Lucanus cervus
Potter 1982
Chilopods: House centipede, Scutigera coleoptera
Subphyla Terrestrial
Madibulates/Myriapods
Class Diplopoda
• "millipedes"
• range from 2mm - 28cm
• have mandibles for chewing decaying
vegetation
• 2 pairs of legs per segment adapted for
burrowing
Subphyla Terrestrial
Madibulates/Myriapods
Class Chilopoda
• "centipedes"
• range from 3-30cm
• have fangs, are predacious carnivores some
species consume frogs, birds snakes and mice
• 1 pair of legs per segment, adapted for running
• appendages on last segment used for defense not
locomotion
Insecta
• Insecta
70% of all animals on earth 30 orders:
– Diptera:“2 wings”flies, gnats, mosquitoes
– Coleoptera: “shield wings”beetles
– Hymenoptera: “membrane wing”bees, wasps, ants
– Lepidoptera: “scale wing” moths & butterflies
•
•
•
•
3 Body Sections
3 prs of legs per thorax
1 pr antennnae
excrete N through Malpighian tubules eliminated in dry uric
acid crystals
• respire through tracheae and spiracles
• Complete & Incomplete Metamorphosis
• Parthenogenesis
Harmful Insects
• Pests, vectors of pathogens, crop
eaters, sting, bite
Botfly, Bed Bugs
Beneficial Insects
• Pollination, honey, silk, food
(entomophagy), biological control,
designer genes
Eating Machines
Medicinal Maggots
Forensic Entomology
Crime Scene Creatures
Major Trends in Animal Evolution:
Development of a
body cavity from
the gastrulation
cavity:
deuterostome
coelomates
Protostomes
Deuterostomes
Coelomates: Protostomes VS Deuterostomes
Protostomes:
mesoderm forms
from mass of cells
between endoderm
and ectoderm
Deuterostomes:
mesoderm forms as
outpocketing of
gastrulation cavity
• Deuterostomes (echinoderms and chordates) develop the anus first,
then the mouth at the other end of the embryo. Deuterostomes are
coelomate animals these embryological characteristics:
– Radial cleavage in embryonic cell division: the daughter cells sit on top of
previous cells.
– Fate of cells is indeterminate; if embryonic cells are separated, each one
develops a complete organism.
– The blastopore is associated with the anus, and the second embryonic opening is
associated with the mouth.
Phylum Echinodermata
Sea star
Sea urchin
Brittle star
Sea Lily
Echinoderms:
• All are marine organisms
• Larvae are bilaterally symmetrical
• Adults are slow moving or sessile and have
have petamerous radial symmetry (although
they are not perfectly symmetrical)
• Embryologic development makes them more
similar to chordates than to the cnidarians
• Visualizing an Echinoderm
• Unique to echinoderms is the water vascular
system, a network of hydraulic canals branching
into extensions called tube feet.
– These function in locomotion, feeding, and gas exchange.
Echinos=spiny
Derma=skin
Echinoderms include : sea star, sea urchin, sea cucumber,
sand dollar, basket stars brittle stars
marine & largely bottom dwellers
 pentamerous radial symmetry, from bilateral ancestor
 internal skeleton w/calcareous ossicle that may articulate,
bears projecting spines/tubercles
 series of canals, water vascular system
 no excretory organs
• mostly dioecious w/ external fertilization
• Fertilization in a Sea Urchin
Echinoderm Classes
• Asteroidea: star shaped, free moving, with bodies
composed of rays
• Ophiuroidea: basket stars, serpents stars, brittle stars
• Echinoidea: sea urchins, sand dollars
– Fertilization
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•
•
•
•
Holothuroidea: sea cucumber (anus)
Crinoidea: Sea lillies, feather stars
Colentricycloidea: sea daisies
Classes of Echinoderms
Sea cucumber Fights with Guts
Protostomes
Deuterostomes
Coelomates
Pseudocoelomates
Acoelomates
Bilateral symmetry
Brum et al., 1994
Primitive Chordates
• Anatomy of a Tunicate
References
• http://cas.bellarmine.edu/tietjen/images/phylum_porifera.htm
• http://www.cartage.org.lb/en/themes/sciences/Zoology/Biologicaldiverstity/Animals
II/AnimalsII.htm
• Parasites How They Live
• Invertebrates Close Up
• Animals webpage