COMPARING INVERTEBRATES
Chapter 29
Taxonomy
• The system we use today to name and classify
•
all organisms was developed by Carl Linnaeus.
It is known as the system of binomial
nomenclature because every organism has a two
part name.
– Ex: Pantera leo
– Ex: Homo sapiens
• In addition, Linneaeus classified every organism
into a hierarchy of taxa, or levels of
organization.
Taxonomy--Classification
• King
• Kingdom
• Philip
• Phylum
• Came
• Class
• Over
• Order
• For
• Family
• Great
• Genus
• Spaghetti
• Species
Example Classification
• Domain
• Eukarya
• Kingdom
• Animalia
• Phylum
• Chordata
• Class
• Mammalia
• Order
• Primate
• Family
• Hominid
• Genus
• Homo
• Species
• sapiens
Taxonomy
• All life can be
organized into three
domains: Bacteria,
Archaea, and
Eukarya.
Bacteria
• Single celled
•
•
•
•
•
•
prokaryotes
Aerobes/anaerobes
Decomposers
Pathogens
some are
photosynthetic
Have no introns
Includes viruses
Archaea
• Single celled
• Prokaryotes
• Extremophiles
– Methanogens
– Halophiles
– Thermophiles
EUKARYA
• All have nucleus and
•
•
internal organelles
Includes animal and
plant cells
Consists of 4
kingdoms
• KINGDOMS
–
–
–
–
Protista
Fungi
Plantae
Animalia
Kingdom: Protista
Kingdom: Fungi
Kingdom:
Plantae
• Multicellular
• Nonmotile
• Autotrophic
•
•
•
•
(photosynthetic)
Have cell walls
Store sugars as starch
Alternation of generations
Some have vascular
tissue
Kingdom:
Animalia
•
•
•
•
Multicelluar
Heterotrophic
Most are motile
Most reproduce sexually
and are diploid
Kingdom: Animalia
Animal classification
placed into related
groups
1. Invertebrates—
majority of
animals which
lack a backbone
2. Vertebrate-animals with a
backbone
Common Phyla:
Porifera
Cnidarians
Platyhelminthes
Nematodes
Annelids
Mollusks
Arthropods
Echinoderms
Chordates
Evolutionary Trends
A. Specialized Cells, Tissues, and Organs
• As larger and more complex animals
evolved, specialized cells joined together
to form tissues, organs, and organ
systems that work together to carry out
complex functions.
Evolutionary Trends
B. Body Symmetry
• Radial symmetry – parts are arranged in a
circle around a central point
• Bilateral symmetry – parts are mirror images
of each other (left and right sides)
• Asymmetrical – no definite shape
Assymmetrical—Porifera
Evolutionary Trends
• Whereas primitive
animals exhibit radial
symmetry,
sophisticated animals
exhibit bilateral
symmetry.
Evolutionary Trends
C. Cephalization
• Along with bilateral symmetry came the development of
cephalization, which is the concentration of sense organs
and nerve cells in the front (anterior part) of the body.
• The digestive, excretory, and reproductive structuress
are located at the back (posterior) end.
• Invertebrates with cephalization can respond to the
environment in more sophisticated ways that can simpler
invertebrates.
Evolutionary Trends—Cephalization
Evolutionary Trends
D. Segmentation
• Many animals who exhibit bilateral
symmetry also have segmented bodies.
• Segments have often become specialized
for specific functions.
• Segmentation allows an animal to increase
in size.
Evolutionary Trends
E. Coelom Formation
• Germ layers formed early in embryonic development:
– Ectoderm (outermost layer)
– Mesoderm (middle layer)
– Endoderm (innermost layer)
• The coelom is a fluid-filled body cavity that is completely
surrounded by mesoderm tissue.
• It represents a significant advance in animal evolution
because it provides space for elaborate organ systems.
Evolutionary Trends—Coelom Formation
Types of body cavities:
• Acoelomates do not have a coelom (body cavity)
between their body wall and digestive cavity.
• Pseudocoelomates have body cavities that are
partially lined with mesoderm.
• Most complex animal phyla are coelomates,
meaning they have a true coelom that is lined
completely with tissues from mesoderm.
Acoelomate
Body covering
(from ectoderm)
Digestive sac
(from endoderm)
Tissue-filled region
(from mesoderm)
Pseudocoelomate
Body covering
(from ectoderm)
Muscle layer
(from mesoderm)
Digestive tract
(from endoderm)
Pseudocoelom
Coelomate
Body covering
(from ectoderm)
Coelom
Tissue layer
lining coelom
and suspending
internal organs
(from mesoderm)
Digestive tract
(from endoderm)
Coelomate
`
Evolutionary
Trends
F. Embryological
Development
Blastopore: first
opening during the
embryonic stages of
an organism
Evolutionary Trends
F. Embryological Development
• Protostome – blastopore becomes the
mouth, and the anus forms secondarily
• Deuterostome – blastopore becomes the
anus, and the mouth forms secondarily
Trends in Animal Development
Echinoderms Chordates
Arthropods
Annelids
Mollusks
Radial
Symmetry
Roundworms
Flatworms
Cnidarians
Radial
Symmetry
Pseudocoelom
Protostome Development
Three Germ Layers;
Bilateral Symmetry
Sponges
Tissues
Singlecelled
ancestor
Deuterostome
Development
Coelom
Trends in Animal Development
From the Primitive
• No symmetry or radial
symmetry
• No cephalization
• 2 germ layers
• Acoelomate
• No true tissues
• Little specialization
• Sessile
To the Complex
• Bilateral symmetry
• Cephalization with
sensory apparatus
• 3 germ layers
• Pseudocoelomate or
coelomate
• Tissues, organs, and
organ systems
• Much specialization
• Motile
Form and Function in
Invertebrates
Ch. 29-2
Feeding and Digestion
• The simplest animals break down food primarily through
intracellular digestion, but more complex animals use
extracellular digestion.
• In intracellualar digestion food is digested inside the
cells.
– The food size must then be smaller than the cells.
• In extracelluar digestion, food is broken down outside
the cells.
– The food size is larger than the cells of the organism.
• How does a
starfish eat?
Patterns of Extracelluar Digestion
• Some animals such as cnidarians and most
•
•
•
flatworms ingest food and expel wastes through
a single opening.
Some cells of the gastrovascular cavity secrete
enzymes and absorb digested food.
Other cells surround food particles and digest
them in vacuoles.
More complex animals digest food in a tube
called the digestive tract, which may have
specialized regions such as stomach and
intestines.
Intestine
Gizzard
Crop
Mouth/anus
Pharynx
Mouth
Gastrovascular
cavity
Annelid
Anus
Gastrovascular
cavity
Cnidarian
Pharynx
Crop
Arthropod
Anus
Pharynx
Mouth
Mouth/anus
Flatworm
Stomach
and
digestive glands
Rectum
Respiration: Gas exchange of O2 and CO2
Two key features of all respiratory systems:
• Respiratory organs have large surface
areas that are in contact with air or water
• Have ways to keep the gas exchange
surfaces moist to allow diffusion to occur
Respiration
Tracheal
tubes
Gill
Siphons
Movement of water
Spiracles
Insect
Mollusk
Airflow
Spider
Book
lung
Circulation
• In an open circulatory
system, blood is only
partially contained
within a system of
blood vessels.
Heart (s)
Blood vessels
Tissues
Sinuses
(spongy cavities)
Circulation
• In a closed circulatory system, a heart or a
•
•
•
heart-like organ forces blood through vessels
that extend throughout the body.
The blood stays within these blood vessels.
Materials reach body tissues by diffusing across
the walls of the blood vessels.
Blood circulates more efficiently in a closed
circulatory system.
Heartlike structure
Hearts
Small vessels in tissues
Blood
vessels
Heart
Sinuses
and organs
Heartlike
structures
Insect:
Open Circulatory
System
Blood
vessels
Annelid:
Closed Circulatory
System
Excretion
• The excretory system is responsible for
removing waste material and conserving
water.
• Waste product is usually nitrogenous,
meaning it contains nitrogen.
• This waste is usually in the form of
ammonia (NH3), which is very toxic!
Excretion
• In aquatic invertebrates, ammonia diffuses from
their body tissues into the surrounding water
• Terrestrial invertebrates convert:
ammonia  urea (less toxic)
• Some insects and arachnids convert:
Ammonia  uric acid
Excretion
Flame
cells
Flatworm
Excretory
tubules
Nephrostome
Excretory pore
Flame cell
Excretory tubule
Nephridia
Digestive tract
Annelid
Arthropod
Malpighian
tubules
Response—Nervous System
• The nervous system gathers information
from the environment.
• The simplest nervous system, found in
cnidarians, are nerve nets.
Trends in the Evolution of the
Nervous System
• Centralization—nerve cells are more
concentrated (ex: ganglia)
• Cephalization—high concentration of nerve
cells in the anterior region (head/front)
• Specialization—more developed sensory
organs
– To detect light, sound, chemicals, movement,
etc.
Arthropod
Brain
Ganglia
Ganglia
Brain
Nerve
Cells
Flatworm
Cnidarian
Mollusk
Movement & Support
• Most animals use
Three main kinds:
•
skeletons
• Exoskeletons
• Endoskeletons
specialized tissues called
muscles to move,
breathe, pump blood, and
perform other life
functions.
In most animals, muscles
work together with some
sort of skeletal system
that provides firm
support.
• Hydrostatic
Movement & Support
• Hydrostatic skeleton
– No hard structures
– Lacks muscles
– Water filled cavity (gastrovascular cavity)
• Exoskeleton or external skeleton
– Outside the body
– Hard body covering made of chitin
– Has to be shed (molting)
• Endoskeleton
– Structural support inside the body
– Muscles
Reproduction
• Sexual reproduction is the production of offspring from
the fusion of gametes.
– Maintains genetic diversity because it generates new
combinations of genes
• Asexual reproduction
–
–
–
–
–
Ex: Fragmentation
Ex: Budding
All offspring are genetically identical to parent (clones)
Allows for organisms to produce offspring faster
Genetic diversity decreases  less able to deal with changes
Reproduction
• Some organisms are hermaphrodites,
meaning that they produce both sperm
and egg.
Reproduction
Fertilization: unification of sperm & egg
• External fertilization
–
–
–
–
Observed in less complex animals
Eggs are fertilized outside the body
Gametes are released in surroundings
Aquatic environment
• Internal fertilization
– Observed in more complex animals
– Eggs are fertilized inside the female’s body
– Require specialized organs