Transcript Animal Development and Phylogeny Notes

Today’s Plan: 4/20/10
 Bellwork: Test Q&A (15 mins)
 Animals and Behavior test (the rest of
class)
 If you finish early, work on labs or
animal summary chart
Today’s Plan: 11/13/09
 Continue with animals (15 mins)
 AP Lab 11 (45 mins)
 Finish Animals notes (the rest of
class)
Animal Development and
Phylogeny
 Animals:
Are multicellular
Are consumers
Are eukaryotic
Are motile at some point in their
development
 Reproduce sexually (some are
parthenogenic)
 Develop from embryos
 Have a variety of evolutionary advances
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Symmetry and Body Plans
 2 main body plans: invertebrate and vertebrate
 Of the 2, invertebrate has the most variation
 Some are asymmetric
 Those which have symmetry, exhibit 1 of2 types :
 Radial-may have top and bottom (oral and aboral
sides), but can pass a plane through the body in any
direction and make 2 equal, identical parts
 Bilateral-have dorsal and ventral as well as posterior
and anterior ends. May exhibit cephalization. Can
pass a plane through the body in only one place to
make 2 equal, identical parts
Figure 32-5
Asymmetry
Sponge
No plane of
symmetry
Radial symmetry
Jellyfish
Multiple
planes of
symmetry
Bilateral symmetry
Lizard
Single plane
of symmetry
Posterior
Anterior
Why Symmetry?
 In general, the most primitive
organisms are asymmetric, slightly
more advanced are radially
symmetric, and the most advanced
are bilaterally symmetric
 What’s the significance of symmetry?
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Indicator of health
Serves the organism’s function
Sometimes redundancy of parts
Sometimes directed nervous
response
The Animal Family Tree
 The most primitive animals are conglomerations of cells
with little specialization and no true tissues
 Slightly more advanced animals have cells organized into
distinct tissues, but no organ systems or body cavity
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Diploblastic organisms have only 2 tissue layers (cnidarians
and ctenophorans)
Triploblastic organisms have 3 tissue layers (bilaterally
symmetric organisms)
 The next group has organ systems, but still no body
cavity (acoelomates)
 Still more advanced organisms develop a body cavity
which is unlined (pseudocoelomates)
 The most advanced organisms develop a body cavity
lined in mesoderm (coelomates)
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In protostomes, coelom forms in mesoderm at the sides of
the archenteron (primordial digestive tube)
In deuterostomes, coelom forms in the archenteron wall
Figure 32-6
Acoelomates have no enclosed body cavity.
No coelom
Skin
(from ectoderm)
Muscles, organs
(from mesoderm)
Gut
(from endoderm)
Pseudocoelomates have an enclosed body cavity partially
lined with mesoderm.
Pseudocoelom
Skin
(from ectoderm)
Muscles, organs
(from mesoderm)
Gut
(from endoderm)
Coelomates have an enclosed body cavity completely lined
with mesoderm.
Coelom
Skin
(from ectoderm)
Muscles, organs
(from mesoderm)
Gut
(from endoderm)
Family Tree Continued
 The coelomates are further divided
into two groups:
 Protostomes-”proto”=first,
“stome”=mouth, form from spiral
cleavage
 Deuterostomes-”deutero”=second,
“stome”=mouth, form from radial
cleavage
 Groups are based on the fate of the
Blastopore during gastrulation
Figure 32-10
Animalia
Bilateria
Deuterostoma
Protostoma
Ecdysozoa
Lophotrochozoa
Segmentation
Acoelom
Pseudocoelom
Pseudocoelom
Radial
symmetry
Segmen(in adults)
tation
Growth by molting
Protostome development
Phylogenetic tree based on similarities and
differences in the DNA sequences of
several genes from various animal phyla.
The bars along the branches indicate when
certain morphological traits originated
Deuterostome
development
Coelom
Triploblasty (origin of mesoderm)
Bilateral symmetry and cephalization
Radial symmetry
Diploblasty (ectoderm and endoderm)
Epithelial tissue
Multicellularity
Segmentation
Figure 32-1-Table 32-1a
Figure 32-1-Table 32-1b
Figure 22-11
DURING GASTRULATION, EMBRYONIC TISSUES FORM DISTINCT LAYERS.
Ectoderm
Mesoderm
Endoderm
Cross section
Start of gut
Blastocoel
Blastopore
Whole embryo
Blastopore
1. Different regions of the
2. Gastrulation begins with the
3. The blastocoel shrinks
4. The three embryonic
frog blastula contain
cytoplasmic determinants
(signals or transcription
factors) that determine
their fate during gastrulation.
formation of an opening—the
blastopore—that extends into
the embryo. Cells from the
surface move into the interior
through the blastopore.
as the surface cells
continue to move inward,
forming the three
embryonic tissue layers.
tissue layers are formed,
ready for organogenesis.
The blastopore (future
anus in frogs) surrounds
a plug of yolk cells.
Figure 22-12
Figure 32-8
PROTOSTOMES
Cleavage
(zygote undergoes
rapid divisions,
eventually forming
a mass of cells)
DEUTEROSTOMES
2-cell
stage
4-cell
stage
8-cell
stage
Gastrulation
(mass of cells
formed by cleavage
is rearranged to
form gut and
embryonic tissue
layers)
Longitudinal
section
Spiral
cleavage
Radial
cleavage
Mouth
Pore
becomes
mouth
Anus
Coelom formation
(body cavity lined
with mesoderm
develops)
Pore
becomes
anus
Gut
Gut
Coelom
Mesoderm
Block of solid
mesoderm splits
to form coelom
Cross section
Mesoderm
Mesoderm pockets
pinch off of gut
to form coelom
Figure 22-8-1
Radial cleavage: Cells divide at right angles to each other.
Spiral cleavage: Cells divide at oblique angles to each other.
A word about Germ layers
 “Germ” layers refers to the 3 layers of
tissues in most animals. The layers are
present at gastrulation during embryonic
development
 Ectoderm is the outermost layer of cells. It
gives rise to the nervous system, skin, hair
and nails
 Mesoderm is the middle layer of cells and is
the most versitile. It becomes the
skeleton, muscles, inner layer of skin,
visceral lining, fatty tissues, and circulatory
system
 Endoderm is the innermost layer of cells. It
gives rise to the gut and organs associated
with digestion and excretion
Why a coelom?
 The most advanced group of
organisms have a coelom. What’s its
significance?
 In order for a body cavity to be
considered a coelom, it must be lined
in mesoderm.
 Mesoderm sections off parts of the body
 This leads to segmentation, a great
evolutionary advance. Why?
Figure 32-7
Hydrostatic skeleton of a nematode
Body wall (in tension—
creates pressure in fluid)
Fluid-filled pseudocoelom
(under pressure—creates
tension in body wall)
Gut
Muscles (cause shape change)
Coordinated muscle contractions result in locomotion.
Muscles relaxed
Muscles
contracted
Muscles
contracted
When the muscles
on one side contract,
the fluid-filled chamber
changes shape and
the animal bends.
Muscles relaxed
About Animal Classification
 As before, new molecular data continues to change
our views on how animals are grouped into phyla.
The bilaterally symmetric animals are particularly
messy to classify
 Our understanding of Hox genes has changed our
views on animal embryology
 There are some points of agreement with respect to
classification:
 All animals share a common ancestor
 Sponges are the base of the animals family tree
 Eumetazoa is a clade of animals with true tissues
(cnidaria and ctenophora, formerly coelenterata)
 Most animal phyla belong to the Bilateria clade
 Chordates and some other phyla belong to the clade
Deuterostomia
Major Invertebrate Phyla
 Sponges were formerly called “Porifera” and are
organisms that have the following characteristics:
 Suspension feeding (capturing food from the water as
it travels through the body
 Pores on the outer surface pull in water and send it
out through the spongocoel and it’s main opening,
the osculum
 All are hermaphroditic
 Have a few specialized cells but no tissues:
 Choanocytes-collar cells that are flagellated for feeding
 Amoebocytes-mobile cells that have pseudopods and
carry nutrients around the body
 These are now split into 2 phyla:
 Calcarea
 Silicea
Figure 32-26
Pseudoceratina crassa
Eumetazoans
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This is a clade, consisting of 2 major phyla of diploblastic
organisms:
 Cnidaria (Includes: jellyfish, hydra, sea anemones, etc)
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Radially symmetrical
Tissue layers (2 distinct-epidermis, gastrodermis)-mesoglea in
between (jelly)
2 forms-medusa (mouth down, free-swimming), and polyp (mouth
up, sessile)
Stinging nematocysts for defense and predation (inside the
cnidocytes)
1st organisms with a nervous system (primitive-nerve net, no
central control)
No matter which shape the organism takes, it’s internal cavity is
the gastrovascular cavity
Food enters the mouth and broken down. Nutrients from the food
are absorbed by the surrounding cells and wastes are expelled
from the mouth (2-way digestive tract)
Ctenophora (Comb Jellies)
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Look like jellyfish, but move via the 8 rows of cilia on their bodies
No cnidocytes/nematocysts, instead use colloblast (specialized
mucous cells) secretions to catch and hold onto prey
Actually have a nervous control structure called the Apical Organ
at one end of the body
Figure 32-27
Polyps attach to substrates.
Aurelia aurita
Medusae float near the water surface.
Aurelia aurita
Figure 32-18
Motile larval anemone
Sessile adult anemone
Figure 32-3
Cnidarians and ctenophores are
diploblastic.
Cnidaria include hydra, jellyfish, corals,
and sea pens (shown).
Ctenophora are the comb jellies.
Ectoderm
Endoderm
This dark
blue comb
jelly…
…has just
swallowed
this white
comb jelly
Figure 32-4
Mouth
Tentacles
Tubular body
Basal disk
Captured prey will be
transferred to mouth
Figure 32-24
Reproductive
polyp
Feeding
polyps
(2n)
MITOSIS
Medusa
(2n)
Colonies can
get very large,
with hundreds
of polyps
Egg
(n)
Sperm
(n)
Larva swims via
cilia, then settles
MITOSIS
Zygote
(2n)
Diploid
Haploid
Figure 32-28
Pleurobrachia pileus
Rows of cilia
Sticky tentacles
Lophotrochozoans
 Clade of organisms that have
either/or both a crown of ciliated
tentacles or a cilliated larvae called a
trocophore
 This includes the flatworms
(Platyhelminthes), Rotifers, Molluscs,
and annelids
Figure 33-11
Lophotrochozoa
Ecdysozoa
Figure 33-4
Lophophores function in suspension feeding in adults.
Trochophore larvae swim and feed.
Food particles
Water
current
Anus
Mouth
Mouth
Cilia used in
locomotion
and feeding
Gut
Anus
Acoelomates
 Also called the flatworms b/c they have no
body cavity and a flattened body
 First organisms with bilateral symmetry and
cephalization (anterior and posterior end)
 Organisms with a two-way digestive tract
or none at all
 No need for lungs or gills because of the
flat body plan (O2 exchange via diffusion)
 Water-living or parasitic
 Mostly vermiform (“vermi”=worm)
Figure 33-13
Turbellarians are free living.
Pseudoceros ferrugineus
Cestodes are endoparasitic.
Taenia species
Trematodes are endoparasitic.
Dicrocoelium dendriticum
Rotifers
 Small, freshwater organisms with a ciliated
crown
 Have an alimentary canal with 1-way
digestion
 Some species can reproduce via
parthenogenesis and are all female, others
produce 2 types of eggs and are
parthenogenesis, while others have males
only for the purpose of reproduction
Figure 33-12
Rotaria rotatoria
Corona
Mollusca
 Bilaterally symmetric
 Muscular Foot (ventral)
 Mantle (dorsal)-secretes shell, forms mantle cavity
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Rasping organ called the Radula
Coelomates
Open circulatory system
Primitive kidneys
Gills or primitive lungs
Eyes for seeing
Several ganglia with a more complex nervous sys
Examples include snails, slugs, chitons, limpets,
bivalves (clams, oysters, mussels, scallops),
chambered nautilis, squid, octopus
Figure 33-7b
Mollusc body plan (internal view)
Gill
Mantle
(secretes shell)
Visceral mass
(internal organs
and external gill)
Muscular “foot”
Figure 33-15
Scallops live on the surface of the substrate and
suspension feed.
Lima scabra
Most clams burrow into soft subtrates and suspension feed.
Water out
Siphons
Foot
Food
particles
Water in
Gill
Gills are thin structures for
gas exchange. They also trap
food particles as water passes
through them. Cilia move the
particles to the mouth
Figure 33-16
Snails have a single shell, which they use for protection.
Maxacteon flammea
Land slugs and sea slugs (nudibranchs) lack shells.
Chromodoris geminus
Bright colors warn
potential predators
of presence of
toxins
Figure 33-17
Tonicella lineata
Figure 33-18
Octopus dofleini
Figure 33-4
Lophophores function in suspension feeding in adults.
Trochophore larvae swim and feed.
Food particles
Water
current
Anus
Mouth
Mouth
Cilia used in
locomotion
and feeding
Gut
Anus
Annelids
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1st organisms with segmentation (metamerism)
Closed circulatory system (blood pigments), but gas
exchange occurs via osmosis
1-way digestive tract
Double nerve cord, 2 ganglia, lateral nerves in each
segment (metamere), brain
Taste, tactile, light sensation
Vermiform
Bilaterally symmetric
Head (prostomium) and an anus-bearing terminal portion
New segments form behind head and are pushed back (like
tapeworms)
Circular and longitudnal muscles for complex movement
patterns-in each metamere
Hydrostatic skeleton in each segment
Septa cause internal segmentation, but are traversed by
the gut and nerves
Figure 33-14
Most polychaetes are marine.
Alvinella pompejana
Chaetae
Most oligochaetes are
terrestrial.
Paranais litoralis
Most leeched live in freshwater.
Hirudo medicinalis
Ecdysozoans
 Clade consisting of organisms that go
through ecdysis (molting) b/c they
have exoskeletons
 Includes the Pseudocoelomates
(Nematodes) and Arthropods
Figure 33-19
Ecdysozoa
Lophotrochozoa
Figure 33-5
Nematodes
 Have round bodies (pseudocoel)
 Organisms have sphincters to hold in
organs
 Both free-living and parasitic
 Ex: hook worm, Ascaris, pinworm, trichina
worm, dog heartworm
 Often have complex life styles
w/intermediate hosts
 Often have male and female forms with
dimorphism
Figure 33-21
Strongyloides species
Nematodes
Arthropods
 Arthro=jointed, pod=foot, all have jointed
appendages
 Exoskeleton made of chitin (a protein) and
sometimes calcium carbonate
 Have metamorphosis
 Bilateral symmetry, open circulation,
nervous system like that of annelids
 Have gills, air tubes, or book gills
 Have head, thorax, and abdomen
(sometimes head and thorax are fused into
a cephalothorax
Figure 33-7a
Arthropod body plan (external view)
Tagma
Head
Thorax
Abdomen
Jointed limbs
Exoskeleton
(covers body)
Segmented body
Figure 33-23
Spider, showing general chelicerate features
Dolomedes fimbriatus
Posterior region
Anterior region
Chelicerae
Mites are ectoparasitic.
Dermatophagoides species
Figure 33-24
Deep-sea lobster
Enoplometopus occidentalis
Red barnacle
Barnacles
secrete their
own shells
Carapace
Fiddler crab
Tetraclita species
Uca vocans
Compound
eyes on
stalks
Figure 33-23-Table 33-1-1
Figure 33-23-Table 33-1-2
Deuterostomia
 This is a clade that includes all
deuterostome animals
 The major phyla within this clade are
the Echinoderms and Chordates
Figure 34-1
Echinoderms
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Non-metameric adult with radial symmetry
Larvae are bilaterally symmetric
No head or brain, circular ring and radial nerves
Skeleton of embedded ossicles (calcium carbonate)
within the dermis
Pedicellariae for catching and moving food
Water vascular system with tube feet for locomotion
One-way digestive tract (sometimes with eversible
stomach)
Dermal branchae also help with vascularization
Usually separate sexes
Ex: sea stars, sea lillies, sea urchins
Figure 34-2
Figure 34-3
Figure 34-21
Invertebrate Chordates
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2 major Phyla: Cephalochordata and Urochordata
Widespread
Marine
Have a notochord at some point in their development
Pharyngeal Gill slits
Dorsal Nerve cord (tubular)
Postanal tail
Bilateral Symmetry
Segmented muscles in an unsegmented trunk
Ventral heart w/ closed circulation
Complete digestive system
Figure 34-5a
Figure 34-5b
Figure 34-23
Figure 34-24
Figure 34-7-1
Figure 34-7-2
Vertebrate Chordates
 Have all of the characteristics of invertebrate
chordates, but also have a vertebral column and
spinal cord
 These are also called the craniates-have a head
 Major Classes include:
 Myxini-Hagfish
 Pterromyzontida-Lampreys
 Chondrichtheyes-Sharks, skates, and rays
 Osteictheyes (Actinopterygii, Actinistia, Dipnoi)-Bony
fish
 Amphibians-frogs, salamanders
 Reptiles-lizards, snakes, crocodillians
 Aves-Birds
 Mammalia-duh!
Figure 34-25
Figure 34-26
Figure 34-27
Figure 34-28
Figure 34-29
Figure 34-35
Figure 34-37
Figure 34-36
Figure 34-38
Figure 34-31
Figure 34-32
Figure 34-33
Trends in Chordate Evolution
 From plain chordate characteristics to
having a cranium
 From cranium to jaw (made from gills of
fish)
 Tetrapodal body plan (made from fins of
fish)
 Amniotic (membranous) egg-waterproofing
 Feathers (from scales of reptiles)
 From oviparity (monotremes) to viviparity
(marsupials and eutherians)
Figure 34-10
Figure 34-12
Figure 34-14
Figure 34-16
Figure 34-17