Transcript Animal Diversity

Animal Diversity
Why do we care?
• Understand that organism better
• Comparison allows understanding of other
organisms (ie- humans)
– Ex: plants don’t have centrioles so they probably are
involved in division of chromatids
– Model organisms - Drosophila for genetics
• Gives novel approaches for doing the same thing.
(Hearts)
• New Biotech – drugs (penicillin), enzymes
(restriction enzymes), therapies (gene therapy),
etc
Animal Diversity
Comparative Anatomy
and physiology
How are things accomplished and how does
the way it accomplished affect the way
other tasks are accomplished. What
adjustments have to be made.
Cell Theory
All organisms share some common characteristics:
1. All living organisms are composed of cells
2. Cells are the basic unit of structure and function
3. Cells come from pre-existing cells
Specializations (Organelles) give some understanding of
basic cellular function
Domains of life
Archaea
Life
Prokaryotes
Bacteria
(often
eubacteria)
Eukarya
Archaea
Life
Bacteria
Fungi
Plantae
cellulose
Eukarya
Animals
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Eukaryotic
Multicellular
Heterotrophic
No cell walls
Special structures:
– Collagen
– No cell wall
Cell Wall
composed
of Chitin
Animalia
Characteristics of animals
• Body Plan: Tissues for
specific functions
- Tissues
- Organs
- Organ systems
Keep in mind importance surface area
Why Multicellular?
high surface area
Exchange (ie - O2, CO2, glucose)
Happens at surface
Reflected in organs
Respiratory
Digestive
excretory
Needs of all cells / organisms
• Nutrients & waste exchange
– O2 / glucose / nutrients brought to all cells
– CO2 /wastes taken away
• Protection
• Reproduction
Habitat must be considered
Organisms of a certain size must have some sort of respiratory
and/or circulatory system to get O2 to each cell (especially
visceral ones).  How do different organisms accomplish this?
How does the habitat affect this?  Large aquatic organisms
MUST have exterior respiratory surfaces to address the
reduced amount of O2 in water.
Phylogenetics
• Grouping of species by evolutionary relatedness
• Methods for determining relatedness:
– Classical: Form, function, embryology
– Modern: Molecular
Taxonomy
• Related field – naming and classification system
• Traditionally base on structure (this is a slight distinction)
• Now naming is based on phylogenetics so effectively the same.
Characteristics of the Animal kingdom
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•
•
Eukaryotic
Multicellular
Heterotrophic
No cell walls
Special structures:
– Collagen
– No cell wall
• Body Plan = organization
into distinct components
with specialized function
- Tissues
- Organs
- Organ systems
Classification Methods (Body Plans)
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•
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Body Cavity Type
Symmetry
Tissue Organization
Digestive openings
Circulatory
Excretory
Nervous
Respiratory
Support systems
Locomotion
Habitat
DNA sequence
Enzyme / Protein similarities
These are examples that are specific
(but not restricted) to animals
Organisms with similarities in
these characteristics are placed
more closely together
Example of complete ranking
Bacteria
Archaea
Fungi
Plantae
Cell Wall
Chitin
cellulose
Eukarya
Clades – grouping system
Cladogram (family tree) of a biological group. The red and blue
boxes represent clades (i.e., complete branches). The green
box is not a clade, but rather represents an evolutionary
grade(organisms with common traits), an incomplete group,
because the blue clade is descended from it, but is excluded
Fig. 28-03a
Excavata
Diplomonads
Parabasalids
Euglenozoans
Apicomplexans
Chromalveolata
Alveolates Stramenopiles
Ciliates
Diatoms
Golden algae
Brown algae
Oomycetes
Chlorarachniophytes
Rhizaria
Forams
Radiolarians
Red algae
Chlorophytes
Charophyceans
Archaeplasti
da
Side Note:
All things in yellow are protists
Even though protists are no
longer considered a valid
kingdom the species in this
group have not yet be placed
and so are still most often
refered to as protists
Dinoflagellates
Land plants
Slime molds
Nucleariids
Fungi
Choanoflagellates
Animals
Unikonta
This is just meant to give you an idea of protists
and other organisms you might see, will only
very generally be on lab test
Gymnamoeb
as
Entamoebas
Animals are multicellular,
heterotrophic eukaryotes with tissues
that develop from embryonic layers
• There are exceptions to nearly every criterion for
distinguishing animals from other life-forms
• Several characteristics, taken together, sufficiently
define the group
No tissues
Cellular level
Animals
Hetertrophs, movement, multicellular
Cladogram
Eumetazoa
Parazoa
…of animal kingdom
Highlighting characteristic that distinguishes
or separates with Phyla at bottom
Bilateral Symmetry
3 germ layers
Bilateria
Radial Symmetry
2 germ layers
Radiata
Mouth 1st
Anus 1st
Deuterostomi
Protostomi
Ecdysozoan
(ring of cilia, larval stage)
(shed exoskeleton)
Lack cilia
Porifera
Sponges
Grantia
Cnidaria
Hydra
Jellyfish
Anemones
WVS
Lophotrochozoan
Lost during
evolution
platyhelminthes
Planaria,
Tapeworm
schistosoma
(blood fluke)
water
vascular system
segmented
Annelids
Clamworm
(nereis)
Earthworm
Leech
Mollusca
Nematoda
Clam
Roundworms
Mussels
Cysts
Snails (Trichinella Spiralis)
Squid
Arthropoda
Grasshopper
Crayfish
Echinodermata
Sea Star
Sea Urchin
Sand Dollar
Notochord
Gill slits
Dorsal
hollow
nerve
Chordata
Fetal Pig
Lancelets
(Amphioxus)
PHYLUMS (body plan, developmental & internal organizations)
Sponges
Side note:
Subdivisions of phyla /
alternative classifications
DO NOT MEMORIZE
Campbell p. ?? fig 32.11
No tissues
Cellular level
Parazoa
Hetertrophs, movement, multicellular
Animals
Metazoa
Eumetazoa
Choanoflagellate
Like choanocyte of sponge
Proifera – What’s set’s it apart from Eumetazoa
•Lack True Tissue (and therefore no organs)
Tissues – group of similar cells that together
perform a particular function
If no tissues, what’s set’s it apart from single-celled organisms
(archaea & protists) other than being multi-cellular
They do have differentiated (different) cell types which
distinguishes it from choanflagellates (single-celled)
closest non-animal cousin
Porifera
Sponges
Grantia
For each branching, you should know the characteristic that
separates. Ex: parazoa or porifera are separated from
Eumetazoa (all other animals) by absence or presence of
tissues.
Porifera: Sponges, grantia
Focus on structures required to fullfill
• sedentary animals
the “needs of all cells” idea
• fresh and marine waters
• suspension feeders, capturing food particles
suspended in the water that pass through their body
• Choanocytes, flagellated collar cells, generate a water
current through the sponge and ingest suspended
food (get nutrients in)
• Otherwise all cells are close to water which is both
food source and waste removal
• Water is drawn through pores into a cavity called
spongocoel, and out through opening called osculum
• No Organ systems (digestive, respiratory, etc)
Some things can’t ID like amoebocytes because can’t see
Note: everything in lab manual is fair game
Choanocyte
Osculum
(opening)
Flagellum
Spongocoel
Ostia
/ Pore
Epidermis
= Outer layer
Mesohyl
= middle layer
Food particles
in mucus
Flagellated collar cell
Draw food particles in
Choanocyte
Collar
Phagocytosis of
food particles
Amoebocyte
Spicules
Water
flow
Amoebocytes
Redistribute nutrients
Make spicules
Fig. 33-4
Spongocoel
• Serves for all of the nutrient gathering and waste
removal capacities of the proifera
Should know about choanocytes though
They are the digestive mechanism in sponges
(intracellular = phagocytosis & digestive vacoules)
• Sponges consist of a noncellular mesophyl layer
between two cell layers
• Amoebocytes are found in the mesophyl and play roles
in digestion and structure
• Most sponges are hermaphrodites: Each individual
functions as both male and female
Spicule
• Made by amoebocytes
• made of calcium salts
• structure / protection
Sponges (Porifera)
Identifying features = lots of holes
Ostia / pore
Small hole
In Flow Current
Osculum
Large hole
Exit channel
Grantia (calcareous sponge) a.k.a scypha
Type of sponge characterized by the presence of Spicules
Spicules: hard, crystalline structures secreted outside the cells;
•calcium carbonate, (same material as shells of many marine animals.
•reinforce the body and make it more resistant to attack
Spicules
Sponges: phylum Porifera
Spicules: hard, crystalline structures secreted outside the cells;
•calcium carbonate, (same material as shells of many marine animals.
•reinforce the body and make
it more resistant to attack
Phylum: Porifera
Organism: Grantia (sponge)
w.m. (wetmount)
Spicules
Needle
shaped
Crystalline
structure
Remember each phylum is a huge group of organism,
so can have many diverse appearances. However, the
grantia below while looking different from other
sponges still has many pores, no tissues, etc.
Sponges: phylum Porifera
Phylum: Porifera
Organism: Grantia (sponge)
c.s. (cross-section)
Identifying features:
Incurrent channels leading
into spongocoel (central
cavity )
Notice many open chamber = pores
Sponges: phylum Porifera
What are tissues?
There are many cell types,
but they function
essentially independently.
An isolated cell is still
functional.
Tissues are groups of
similar cells that work
together toward a single
purpose. One cell in a tissue
is useless by itself.
Cnidarians
ancient phylum of eumetazoans (True Tissue)
• All animals except sponges and a few other groups
belong to the clade Eumetazoa,
• Phylum Cnidaria is one of the oldest groups in this
clade
• Cnidarians have diversified into a wide range of
both sessile and motile forms including jellies,
corals, and hydras
• They exhibit a relatively simple diploblastic, radial
body plan
No tissues
Cellular level
Animals
Hetertrophs, movement, multicellular
Cladogram
Eumetazoa
Parazoa
…of animal kingdom
Highlighting characteristic that distinguishes
or separates with Phyla at bottom
Bilateral Symmetry
3 germ layers
Bilateria
Radial Symmetry
2 germ layers
Radiata
Mouth 1st
Anus 1st
Deuterostomi
Protostomi
Ecdysozoan
(ring of cilia, larval stage)
(shed exoskeleton)
Lack cilia
Porifera
Sponges
Grantia
Cnidaria
Hydra
Jellyfish
Anemones
WVS
Lophotrochozoan
Lost during
evolution
platyhelminthes
Planaria,
Tapeworm
schistosoma
(blood fluke)
water
vascular system
segmented
Annelids
Clamworm
(nereis)
Earthworm
Leech
Mollusca
Nematoda
Clam
Roundworms
Mussels
Cysts
snails (Trichinella Spiralis)
Arthropoda
Grasshopper
Crayfish
Echinodermata
Sea Star
Sea Urchin
Sand Dollar
Notochord
Gill slits
Dorsal
hollow
nerve
Chordata
Fetal Pig
Lancelets
(Amphioxus)
PHYLUMS (body plan, developmental & internal organizations)
Eumetazoa
Radial Symmetry
2 germ layers
Radiata
Bilateral Symmetry
3 germ layers
Bilateria
Cnidaria
•True Tissue but
•2 germ layers not 3
So still no organs
•Radial symmetry
Cnidaria
Hydra
True tissue means many cells of the same
type working together.
Sponges have many cells that are the same
but they each work independently
This is an explanation of germ layers
for your information, you will only be
tested on whether or not something
has 2 or 3 germ layers
2 layers: Endoderm & ectoderm
3 layers
3 layers =
True organs
Usually coelom
Fig. 33-5
Mouth/anus
Polyp
Tentacle
Medusa
Gastrovascular
cavity
Gastrodermis
(endoderm)
Body
stalk
Mesoglea
(extracellular matrix)
Epidermis
(ectoderm)
Tentacle
Mouth/anus
• The basic body plan of a cnidarian is a sac with a
central digestive compartment, the gastrovascular
cavity
• A single opening functions as mouth and anus
• There are two variations on the body plan: the
sessile polyp and motile medusa
• Cnidarians are carnivores that use tentacles to
capture prey
• The tentacles are armed with cnidocytes, unique
(to cnidaria) cells that function in defense and
capture of prey
• Nematocysts are specialized organelles within
cnidocytes that eject a stinging thread
Fig. 33-6
Cnidocytes – 1 cell
Tentacle
Cuticle
of prey
Thread
Nematocyst
“Trigger”
Thread
discharges
Cnidocyte
Thread
(coiled)
Digestion &
respiration & etc.
Gastrovascular cavity
Enzymes in cavity
Extracellular digestion
Reproduction
Sexual or asexual
Budding
Asexual
Genetically
identical
Phylum Cnidaria
Phylum Cnidaria
Eumetazoa
Bilateral Symmetry
3 germ layers
Bilateria
Radial Symmetry
2 germ layers
Mouth 1st
Protostomi
Anus 1st
Deuterostomi
3 germ layers
= true organs
Bilateral symmetry
Mouth
Anus
from blastopore
Symmetry & mouth anus development
Don’t worry about this
It does not mean will end
being radially symmetrical
3 germ layers usually
means a coelom
Difference between
protosomes and
deuterosomes
Body Cavity = coelom
GI Tube (mouth to
anus) within a tube
(coelom)
Allows room for filling
e.g. heart and
pericardial cavity
Gastrovascular cavity (
1 opening)
Packed with cells
surrounding it
Nothing resembling coelom
GI suspended in cavity by mesentery
Peritoneum - Lining on both sides by epithelitum
Eumetazoa
Bilateral Symmetry
3 germ layers
Bilateria
Radial Symmetry
2 germ layers
Mouth 1st
3 germ layers
Anus 1st
Deuterostomi
Protostomi
= true organs
Bilateral symmetry
Mouth
Anus
from blastopore
Lophotrochozoan
Ecdysozoan
(ring of cilia, larval stage)
(shed exoskeleton)
platyhelminthes
Lack cilia
Lost
Planaria, Tapeworm
,schistosoma (blood fluke)
Annelids
Clamworm
Earthworm
Mollusca
Nematoda
Arthropoda
Clam
Roundworms
Crayfish
Grasshopper
Lophotrochozoa
• The clade Lophotrochozoa was identified by
molecular data
• Some develop a lophophore (ciliated tentacle
surrounding mouth) for feeding, others pass
through a trochophore larval stage, and a few have
neither feature
Bilateria
Anus 1st
Mouth 1st
Deuterostomi
Protostomi
Lophotrochozoan
Ecdysozoan
(ring of cilia, larval stage)
(shed exoskeleton)
platyhelminthes
Lack cilia
Lost
Planaria, Tapeworm
,schistosoma (blood fluke)
Larval stage
Has ring of cilia
Platyhelminthes = Flatworms
•
•
•
•
•
Ex: Planaria, tapeworms, schistosoma (blood fluke)
Members of phylum Platyhelminthes live in marine,
freshwater, and damp terrestrial habitats
Although flatworms undergo triploblastic (3 germ layers)
development, they are acoelomates
Note this is an exception
They are flattened dorsoventrally and have a
Which is why they can have this
gastrovascular cavity
Gas exchange takes place across the surface, and
protonephridia regulate the osmotic balance
Thin enough that all cells are close to water which is both
food source and waste removal – no specific organs for
circulatory etc
Tapeworm
200 µm
Proglottids with
reproductive structures
Hooks
Sucker
Scolex
Cephalization
• Planarians (non-parasitic flatworm) have lightsensitive eyespots and centralized nerve nets
• The planarian nervous system is more complex and
centralized than the nerve nets of cnidarians
• Planarians are hermaphrodites and can reproduce
sexually, or asexually through fission
Fig. 33-10
Pharynx
Digestive system
Gastrovascular
cavity
Mouth
Eyespots
Ganglia
Ventral nerve cords
Flatworms: phylum Platyhelminthes
Pharynx
Different sections of the Gastrovascular cavity
NOT a body cavity (coelom)
Planaria excretory system
• Like nephron
• Cilia creates current that pulls in interstital fluid
• Get secretion and reabsorption
Fig 44.11
Planaria Reproductive system
• Male female
Flatworms: phylum Platyhelminthes
Three tissue layers in embryo. Almost all animals share this basic feature; the sponges and
cnidarians are exceptions.
Acoelomate: Flatworms don't have any kind of coelom or pseudocoelom; their bodies are
basically solid. This simple body structure led biologists to conclude that the phylum
Platyhelminthes branched off from the rest of the animals before the evolution of the coelom.
However, some genetic studies have led some researchers to argue that flatworms descended
from an ancestor that had a coelom, and later lost the coelom.
Gastrovascular cavity: The digestive tract has only one opening, and branches throughout the
body. Flatworms do extracellular digestion, like most animals.
Pharynx: a muscular tube through which the flatworm can suck food into its gastrovascular
cavity. The opening into the pharynx could be considered the mouth, but since this animal has a
two-way gut, that opening also must function as the anus.
Flatworms: phylum Platyhelminthes
Fluke
No metamerization
Bilateria
Mouth 1st
Anus 1st
Protostomi
Deuterostomi
Lophotrochozoan
Ecdysozoan
(ring of cilia, larval stage)
(shed exoskeleton)
Lack cilia
segmented
Lost during
evolution
platyhelminthes
Planaria,
Tapeworm
schistosoma
(blood fluke)
Annelids
Clamworm
(nereis)
Earthworm
Leech
Mollusca
Clam
Mussels
snails
Annelids
• Annelids have bodies composed of a series of fused
rings (segmented = metamerism)
• The phylum Annelida is divided into three classes:
– Oligochaeta (earthworms and their relatives)
– Polychaeta (polychaetes)  clamworm
– Hirudinea (leeches)
Fig. 33-22
Cuticle
Epidermis
Coelom
Circular
muscle
GI
Metaniephridium
Septum
(partition
between
segments)
Metanephridium
Longitudinal
muscle
Anus
Dorsal vessel
Chaetae
Intestine
Fused
nerve
cords
Ventral
vessel
Nephrostome
Metanephridium
Clitellum
Esophagus
Pharynx
Giant Australian earthworm
Cerebral ganglia
Crop
Intestine
Gizzard
Mouth
Subpharyngeal
ganglion
Blood
vessels
Ventral nerve cord with
segmental ganglia
Earthworm
Reproduction
Similarly, for all organs
Identify organs and what they are for
For which organ systems
Clitellum
Annelid Excretory system
Metanephridium
analagous to nephron but
Pulls in coelomic fluid
Fig 44.12
Clamworm = nereis
Palp
With tooth
Cirri
(tentacles)
Cecum
Prostomium (first body segment)
Clamworm Respiratory System
Parapodium (functions as gill)
And as feet
Bilateria
Mouth 1st
Anus 1st
Deuterostomi
Protostomi
Lophotrochozoan
Ecdysozoan
(ring of cilia, larval stage)
(shed exoskeleton)
Lack cilia
segmented
Lost during
evolution
platyhelminthes
Planaria,
Tapeworm
schistosoma
(blood fluke)
Annelids
Clamworm
(nereis)
Earthworm
Leech
Mollusca
Clam
Mussels
Snails
Squid
Larval stage
Has ring of cilia
No tissues
Cellular level
Animals
Hetertrophs, movement, multicellular
Cladogram
Eumetazoa
Parazoa
…of animal kingdom
Highlighting characteristic that distinguishes
or separates with Phyla at bottom
Bilateral Symmetry
3 germ layers
Bilateria
Radial Symmetry
2 germ layers
Radiata
Mouth 1st
Anus 1st
Deuterostomi
Protostomi
Ecdysozoan
(ring of cilia, larval stage)
(shed exoskeleton)
Lack cilia
Porifera
Sponges
Grantia
Cnidaria
Hydra
Jellyfish
Anemones
Hermit crab
WVS
Lophotrochozoan
Lost during
evolution
platyhelminthes
Planaria,
Tapeworm
schistosoma
(blood fluke)
water
vascular system
segmented
Annelids
Clamworm
(nereis)
Earthworm
Leech
Mollusca
Nematoda
Clam
Roundworms
Mussels
Cysts
Snails (Trichinella Spiralis)
Squid, octopi
Arthropoda
Grasshopper
Crayfish
Echinodermata
Sea Star
Sea Urchin
Sand Dollar
Notochord
Gill slits
Dorsal
hollow
nerve
Chordata
Fetal Pig
Lancelets
(Amphioxus)
PHYLUMS (body plan, developmental & internal organizations)
5 features typical in mollusks
•Mantle – secretes CaCO3 shell
•Shell – external skeleton of calcium
carbonate. Lacking in some (e.g. slugs, octopi)
•Foot – Muscular structure for digging (clams)
crawling (snails), grabbing (octopus)
•Ctenidia – like gills for filtering food & gas
exchange
•Radula – rasping organ for scraping (not in
clams which are filter feeders)
Molluscs
Dorsal
(back)
Near hinge
Oldest portion
Anterior
(Front)
Posterior
(back)
Ventral
(front)
http://www.biologyjunction.com/clam_dissection.htm
Anterior
Mantle - tissue that lines both valves & covers the
soft body of the clam.
Points toward
Anterior end
Remove gills (and foot) to find visceral mass
mouth
Bilateria
Mouth 1st
Anus 1st
Deuterostomi
Protostomi
Lophotrochozoan
Ecdysozoan
(ring of cilia, larval stage)
(shed exoskeleton)
Nematoda
Roundworms
Cysts
(Trichinella Spiralis)
Larval stage
Has ring of cilia
Larval stage
Does NOT Have
ring of cilia
Or no larval
stage at all
Arthropoda
Grasshopper
Crayfish
Exoskeleton
Nematodes
• or roundworms, found in most aquatic habitats, soil, moist
tissues of plants, and in body fluids and tissues of animals
• have an alimentary canal, lack circulatory system
• Reproduction in nematodes is usually sexual, by internal
fertilization
Fig. 33-26
Encysted juveniles
Muscle tissue
Trichinella spiralis
50 µm
Nematode: Trichinella spiralis
Parasite in cyst
How to identify
Later you will recognize
muscle tissue
All mammalian tissue
is fairly uniform with
tissue transitions that
are fairly defined /
complete so the cyst
looks pretty aberrant
(unusual)
Embryo inside
Arthropoda
• Most diverse phylum  Changing
• Chitinous exoskeleton
– Jointed appendages
– Growth/molting
• Segemented
– Head, thorax, abdomen
– External appendages that can be modify
– Tagmatization – fusion of appendages
(crustaceans)
Cephalon
Carapace –
shell covering the cephalothorax
Evidence of tagamatization
No tagamatization
Athropod – Crayfish sexing
Using one hand to hold the crayfish dorsal side up in the dissecting
tray, use scissors to carefully cut through the back of the carapace
along dissection cut line 1. Cut along the indentations that separate
the thoracic portion of the carapace into three regions. Start the cut
at the posterior edges of the carapace, and extend it along both sides
in the cephalic region.
Use forceps to carefully lift away the remaining parts of the
carapace, exposing the underlying gills and other organ
Fig. 33-35
Abdomen
Thorax
Head
Compound eye
Antennae
Heart
Cerebral ganglion
Dorsal
artery
Anus
Crop
Vagina
Malpighian
tubules
Ovary
Tracheal tubes
Nerve cords
Mouthparts
Arthropod excretory system
Malpighian tubules
Addresses problem of desiccation
Actively secretes from
hemolymph into digestive
tract. Nitrogenous wastes
secreted as uric acid and
excreted in feces
Sexing
Double = female
Spiracle
Eumetazoa
Bilateral Symmetry
3 germ layers
Bilateria
Radial Symmetry
2 germ layers
Mouth 1st
3 germ layers
Anus 1st
Deuterostomi
Protostomi
= true organs
Bilateral symmetry
Mouth
Anus
from blastopore
Lophotrochozoan
Ecdysozoan
(ring of cilia, larval stage)
(shed exoskeleton)
platyhelminthes
Lack cilia
Lost
Planaria, Tapeworm
,schistosoma (blood fluke)
Annelids
Clamworm
Earthworm
Mollusca
Nematoda
Arthropoda
Clam
Roundworms
Crayfish
Grasshopper
Bilateria
Anus 1st
Protostomi
Mouth 1st
Deuterostomi
WVS
water
vascular system
Echinodermata
Sea Star
Sea Urchin
Sand Dollar
Notochord
Gill slits
Dorsal
hollow
nerve
Chordata
Fetal Pig
Lancelets
(Amphioxus)
Echinodermata
• Water Vascular System
– Movement
– Circulatory system – distribute coelomic fluid
• Endoskeleton – calcareous plates
• Radial symmetry as adults
– Juvenile have bilateral symmetry
Starfish young
Note Radial symmetry
Canals are visible showing the water vascular system
Fig. 33-39
Anus
Stomach
Spine
Gills
Central disk
Digestive glands
Madreporite
Radial
nerve
Ring
canal
Gonads
Ampulla
Podium
Radial canal
Tube
feet
Aboral ( opposite mouth) side
aboral
oral
Fertilized eggs grow into bipinnaria and later
into brachiolaria larvae, which either grow
using a yolk or by catching and eating other
plankton. In either case, they live as plankton,
suspended in the water and swimming by
using beating cilia. The larvae are bilaterally
symmetric — unlike adults, they have a distinct
left and right side. Eventually, they undergo a
complete metamorphosis, settle to the
bottom, and grow into adults.
http://www.madreporite.com/science/science.htm
Chordates – 4 features
• Notochord - Stiffing rod - Made of cartilage initially
• Dorsal, Hollow nerve chord
• Pharyngeal gill slits – lost during development
• Post-anal tail
Filled with CSF
Chordate
Nerve cord
notochord (tube below nerve cord)
Gill slits
Post-anal tail
Subphylum includes vertebrates = spinal cord
So all vertebrates are chordates, but not all chordates
are vertebrates
However, vertebrates are the vast majority of
chordates, only a few exceptions
Chick 48hrs
Chick 48hrs
Chordate: Amphioxus (lancelet)
A notable exception, invertebrate = no spine
Does NOT have a skeleton surrounding nerve cord
Immature Lancelet
Nerve cord and notochord
Post-anal tail
Anus
Gill slits
The notochord is a flexible rod-shaped body
found in embryos of all chordates. It is
composed of cells derived from the mesoderm
and defines the primitive axis of the embryo.
Chordate: Tunicate (sea tulip)
Another notable exception, invertebrate = no spine
Does NOT have a skeleton surrounding nerve cord
Does have segmentation but not a worm
So likely a chordate