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Chapter 17: Animal Evolution and Diversity
I. What makes an animal an animal?
A. 4 features, taken together, distinguish animals from other life
1. Eukaryotic: this feature unites them with all eukaryotes (plants, animals, fungi, and
protists, and separates them from archaea and bacteria (prokaryotes)
2. Multicellular: separates animals from protists, generally unicellular; most plants,
animals and fungi are multicellular
3. Heterotrophic: separates them from plants and algae (plantlike protists), Psing; groups
them with fungi -they ingest food
4. Lack cell walls, distinguishes animals from plants, algae and fungi which have at least
partial cell walls
B. Other features
1. Most animals take food into their bodies for nutrition, they generally have a digestive tract
2. Unique junctions between cells
3. Life cycles
a. except for haploid sperm and egg, all life stages of animals are diploid
b. male and female adults make haploid germ cells (gametes) by meiosis
c. egg and sperm fuse – zygote
d. early mitotic divisions – blastula (embryonic stage)
e. One side of blastula folds inward to form another embryonic stage – gastrula.
1). Gastrula now has an outer cell layer and an inner cell layer from
infolding
2). inner layer becomes digestive system
3). outer layer becomes epidermis and nervous system
4). in most animals, a third layer forms between other 2 layers (endoderm) and
becomes most other internal organs
5). many animals develop from gastrula into adults
6). some animals, like sea star, develop into 1 or more larval stages
(intermediates). A larva is an immature individual that looks very
different from adult, and doesn’t have capacity for sexual reproduction
7). Larvae undergo major change of body form, called metamorphosis, to
become adults capable of sexual reproduction
C. Animals probably evolved from colonial protists
1. Oldest known fossil animals- 700 mya - Precambrian
2. Most modern animal phyla fossils from the Cambrian, 600 mya
3. No fossils show 1st animal - all too complex
4. Speculation about 1st animal
a. colonial protists - cells divide but don’t separate; colonies may have been
hundreds or thousands of cells
b. hollow sphere, possibly. Floating aggregates of cells that ingested organic
nutrients from the waters.
c. division of labor - locomotion, digestion, reproduction; at some point, division of
labor- somatic vs. reproductive
d. still a long way from highly specialized, interdependent nature of true
multicellularity; hollow colony must become layered
e. infolding may have produced a hollow colony for specialized feeding and digestive
cells
f. infolding may have eventually eliminated hollow portion, paving way for more layers
of cell, division of labor.
g. perhaps by this time, junctions may have formed btn cells for distributing nutrients
and holding cells together
h. organism with this level of organization could be called primitive animal, or
protoanimal (organism that gave rise to animals)
i. probably a crawler, not a floater, perhaps ate nutrients off ocean floor
D. Animal Phylogeny overview
1. symmetry
a. radial - Radial animals lack forward orientation, sit on surface of seafloor or drift, waiting for
action to come to them. Bilateral animals - generally quite active and travel head first through
environment. crawl, swim, run, walk, or fly. Sense organs contact environment first and help
animal respond. Humans are bilateral. Why don’t we move head first through the environment?
b. bilateral - Most animals are bilaterally symmetrical - can be divided equally by a single cut into
mirror image right and left side
1. head end - anterior
a. head is prominent part of bilateral animals
1. sensory structures
2. brain
3. mouth
b. brain and sensory structures along with nerves = organ system = nervous
system
2. tail end - posterior
3. dorsal side - back
4. ventral side - front or underside
5. lateral- side surfaces
2. body cavity Most animals have a body cavity, fluid filled space between digestive tract and body wall.
Sponges, cnidarians and flatworms lack them. Fig. shows structures of 3 animals - color of cells
indicates same tissue layers: outside covering region- blue, middle region (pink), and lining of digestive
cavity (yellow). These tissue layers form from cell layers of gastrula in embryonic development
a. . acoelomates - flatworms lack a body cavity
b. pseudocoelomate - roundworms have a cavity called pseudocoelom (false, hollow),
a). an internal space in direct contact with wall of the digestive tract
b). the outer edge of pseudocoelom contacts muscle layer, part of body wall
c. coelomate - other animals have more complex body structure than either of the two above
a). body cavity - coelom - completely lined by a middle tissue layer, which extends from
the body wall and wraps the digestive tract.
b). suspends organs from the body wall
Advantages of coelom:
1). more flexible- animals can crawl and burrow more easily
2). organs grow and move independently of outer body
3). fluids cushion organs, preventing injury; animals with skeletons would do
serious damage to organs without fluids to protect organs during even
mild exercise
4). fluids help circulate O2, waste and nutrients - amoeboid cells help in these
functions
5). fluids provide structure to some animals (like earthworms).
c). structure related to function - small size of flatworms means they don't need a body
cavity, all nutrients and O2 can diffuse in and waste out. Even long ones, like
tapeworms, are very thin.
II. Invertebrates - Most animals are invertebrates, no vertebral column (backbone).
A. Sponges - Phylum Porifera
1. most are marine (oceanic), but some are freshwater
2. most live singly or in clusters formed by budding. Many can regenerate completely if
fragmented into pieces
3. Vase- shaped or cylindrical sponges have radial symmetry - body arranged like pieces of a
pie around radial axis. (any imaginary plane passed vertically through the body will produce
mirror images
4. simple animals - generally, 3 loosely associated layers of cells
a. outside layer of flattened cells provides protection
b. middle body layer has motile cells called amoebocytes and skeletal components
composed of a flexible protein called spongin or mineral containing particles.
c. third cell layer consisting of flagellated cells called choanocytes or collar cells,
have collar like structure surrounding base of flagella. Aided by the flagella on
choanocyte, water flows throughout the pores into the central cavity and then out of
the sponge through its one large opening.
d. biologists believe sponges arose very early in animal evolution, from multicelled
organisms
1). lack digestive tract
2). lack gastrula stage
3). 3 cell layers are not homologous to body layers of other
animals
4). lack nerves and muscles
5). not true tissues
B. Phylum Cnidaria: hydras, jellies, sea anemones and corals. All have radial symmetry and
cnidocytes
1. Radial symmetry is a hallmark of this phylum; any vertical cut will produce mirror images.
Body forms:
a. polyps - columnar with radiating arms called tentacles
b. medusas - umbrella like, fringe of tentacles around umbrella - motile
2. some cnidarians have life cycles with both polyps and medusas
3. carnivores - use tentacles -capture small animals and protists, to push prey into mouth
a. polyp - mouth at top of column, at hub of radiating tentacles
b. medusa- mouth in center of underside of umbrella
4. in both body plans, mouth leads to digestive cavity called gastrovascular cavity
a. undigested food exits thru mouth, no anus; digestive system is said to be incomplete
b. cavity circulates body fluid that services internal cells
c. fluid in cavity provides body structure and support, like water in a balloon
5. All cnidarians have cnidocytes- specialized cells, found on surface of tentacles of polyps
and medusas- fine thread coiled within a capsule. When discharged, thread can sting or
capture prey; some big enough to catch fish
a. defense
b. prey capture
6. several features absent in sponges, present in other phyla:
a. digestive cavity
b. gastrula stage of development
c. presence of tissues. eg sea anemone has well developed nerve and muscle
tissue, it can creep, swim, roll, burrow or somersault away from danger.
d. tissue animals - though some have organs, most cnidarians have tissues that
perform vital functions.
C. Platyhelminthes- flatworms are simplest bilateral animals. Leaf or ribbonlike animals.
1. unusually simple bodies for bilaterals
2. incomplete digestive tract - no anus; most bilateral animals have a complete digestive system
3. flatworms lack an internal cavity; digestive cavity is only space in body, similar to cnidarians it
is a gastrovascular cavity; most bilateral animals have another body space called the body
cavity between digestive system and body wall.
4. 3 major groups of flatworms
a. freeliving (nonparasitic) flatworms - planaria
1). nervous system - dense clusters of nervous tissue (brain), eyespots, small
nerves that branch throughout the body
2). digestive system - highly branched. mouth located not in head, but ventral
surface; muscular tube protrudes through mouth and pulls food in. Planaria live
on undersurfaces of rocks in ponds and streams. Using cilia, they crawl in
search of food. Muscles allow them to twist and turn.
b. flukes - parasites. e.g. Schistosoma - female spends much of time in a groove in the
male’s body; they copulate frequently producing over 1000 eggs/day. Females and
males have suckers to attach to the inside of the blood vessels near the host’s
intestines. Blood flukes infect humans and cause severe disease called schistosomiasis
(blood fluke disease). It’s widespread in Africa, Southeast Asia and South America - 250
million people in 70 countries: severe abdominal pain and dysentery.
c. tapeworms are 3rd type of flatworms, also parasitic. Inhabit the digestive tracts of
vertebrates, including reptiles, birds and mammals.
1). Long, ribbon like bodies with repeated parts.
2). no digestive tracts themselves - absorb partially digested nutrients directly
3). head is armed with suckers and teeth to attach to host.
4). behind head, a short neck generates the repeated parts;
5). youngest repeated part is behind the neck, oldest part at the posterior
end of the worm.
6). Repeated parts filled with male and female reproductive parts.
7). parts at posterior end filled with eggs; break off, pass from body in feces.
8). Humans can become infected by a large tapeworm (20 m) Taeniarhynchus
D. Nematodes - roundworms -pseudocoelom and complete digestive tract
1. cylindrical worms with a finely tapered tail; head is more blunt.
2. tough, nonliving skin called cuticle, resists drying or crushing
3. pseudocoelomates
4. complete digestive tract; mouth near head, anus near tail. food travels one way;
specialization in digestive tract - highly efficient
a. anterior region churns and mixes food w/enzymes
b. posterior region absorbs nutrients and disposes of waste
5. Nematodes are among the most numerous of animals in terms of number of individuals and
number of species;
a. important decomposers, they live wherever there is rotting organic matter - soil, lakes,
rivers, oceans
b. also parasites of plants and in body fluids of animals.
c. 90,000 species are known and likely that 10x exist; freeliving worms are most
abundant
d. humans are host to at least 50 species, many of which cause major health problems
1). hookworms
2). heartworms in dogs
3). trichinella - trichinosis (NASTY!! worms may infect heart or brains)undercooked pork may contain juveniles - cook meat until no longer pink
e. conservation of body form among nematodes - all look pretty much as described
E. Phylum Mollusca - snails, slugs, oysters, clams, octopus and squids are examples of great variety body
structure NOT conservative in this group!
1. most have soft bodies protected by hard shell
2. molluscus in latin means “soft”
3. basic body plan a. muscular “foot” - locomotion
b. mantle - outgrowth of body surface that protects animal
1). produces shell in clams and snails
2). also: respiration, waste disposal and sensory reception.
3). mantle cavity - created by mantle formation - may house a gill to extract O2
in water and dispose of fluid wastes
4). many molluscs have radula- a rasping tongue for scraping
c. true coelom - 3 small cavities
1). for heart
2). for reproductive organs
3). one forms part of kidney
d. circulatory system - distributes nutrients and water - has taken over the function of a
large coelom
4. Different body features in different groups
a. gastropods - fresh water, salt water, terrestrial. In fact, this group has the only
molluscs that live on land; 75,000 species
1). terrestrial snails, slugs lack gills; mantle cavity has evolved into a huge lung
2). most are marine; sea slugs are unusual mollusks, lacking a mantle, mantle
cavity and shell
b. bivalves - (bi = double, valva = leaf of folding door); include clams, oysters, mussels,
scallops.
1). have shells divided into 2 halves, hinged together
2). sedentary, live in sand or mud
3). muscular foot used for digging/anchoring
4). mucus coated gills to trap fine food particles
5). scallop - many eyes around mantle edges. can clap its shell shut and squirt
water from its mantle cavity, jetting itself a short distance away
c. cephalopods (greek - kephale = head, pous = foot) - built for speed and agility
1). a few have large, heavy shells, but most have small internal shell (squid), or
lack it all together (octopus)
2). marine predators - beaklike jaws and radula to crush or rip prey apart
3). mouth at base of foot, which is divided into numerous tentacles for catching
and holding prey
4). squids a). draws water into mantle cavity, fires it out - fast sreamlined animal
b). large complex brain
c). among most complex sense organs in animal kingdom - lens (focus
light) and retina (images)
5). all cephalopods have complex brains and sense organs, contribute to
success as predators
6). Octopuses have larger, more complex brains, proportionate to body size
than almost any animal. good learners!
F. Phylum Annelida - Segmentation - subdivisions of the body along its length; this feature played a major role
in evolution of many complex animals. Phylum Annelida (annelus = ring) - segmented worms; 15000 species.
Terrestrial (damp soil), freshwater and marine (some swim, most are bottom dwelling scavengers) habitats;
separate head and tail; body segments all very similar
1. Earthworms are segmented (Fig. 18.10)
a. coelom is partitioned by walls
b. nervous system (yellow) has a cluster of cells in each segment
c. excretory organs (green) repeated in each segment
d. digestive tract is not segmented; it passes through the segment walls from the mouth
to the anus.
e. circulatory system - dorsal and ventral blood vessels;
1. accessory hearts
2. main heart
2. Dragonfly - also segmented, though less uniformly than earthworm
a. segments most pronounced in abdomen.
b. head and thorax - fused segments
c. Each pair of legs and wings emerges from a segment in the thorax
3. Humans have segments, not homologous with earthworm’s or dragonfly’s
a. Backbone is repeated series of knobs called vertebrae, and muscles associated with
vertebrae are segmented.
b. stomach muscles are segmented
4. Advantages of segmented bodies
a. great bodily flexibility
b. mobility; probably an adaptation for movement
5. Oligochaetes - Earthworms one of 3 large annelid groups
a. eats its way through soil extracting nutrients as soil passes thru digestive tube.
Undigested material passes through anus at posterior end.
b. earthworms are incredibly valuable1). they till the soil and enrich it
2). they improve the texture; Darwin estimated that an acre of land (Britain) had
about 50,000 earthworms that produced about 18 tons of feces/yr.
6. Polychaetes (gk- poly = many, chaeta = hair) most live on the seafloor; some freshwater or
estuaries. Most annelids are polychaetes.
a. segmented appendages help worms wriggle
b. segmented appendages increase surface area for taking up O2 and dispose of
wastes
c. many marine species live in tubes; extend feathery appendages to trap suspended
food particles
d. tubes formed by sticky proteins secreted near mouth
7. Leeches are 3rd group of annelids; blood suckers, some are freeliving, eating snails and
insects. Most leeches are fresh water; a few terrestrial species inhabit moist vegetation in the tropics
a. until this century, leeches were used to remove “bad blood” from patients
1). razor-like jaws cut through skin
2). saliva contains strong anesthetic
3). and strong anticoagulant - prevent heart attacks
b. leeches used on burn victims and in reattachments
G. Phylum Arthropoda 1. nearly a million types of segmented animals - includes crayfish, lobsters, crabs, barnacles,
spiders, ticks and insects.
2. arthropod population of earth is about a billion billion 1018 ! most successful phylum of animals
ever, in terms of diversity, distribution and sheer numbers.
3. Fossils indicate intermediates btn annelids and arthropods - Cambrian, 550 mya. But
molecular analysis shows an earlier ancestor of both, two different evolutionary lines.
4. Arthro = jointed, pod = foot; jointed appendages in this phylum. Appendages in lobster for
walking, feeding, swimming, sensory reception and defense.
5. exoskeleton - hard external skeleton- chitin: polysaccharide, w/proteins
a. protection
b. attachment for muscles to move appendages
c. thick in some places thin in others
d. molting- periodic shedding of exoskeleton, secretion of new one
6. annelids have similar segments; most arthropods have distinct groups
lobster, e.g.
a. head- sensory parts: antennae, eyes and mouthparts
b. thorax-pincers for defense and 4 prs. legs for walking
c. abdomen- swimming appendages
7. horseshoe - living fossil - survived w/ little change for hundreds of millions of yrs. Only
survivor of spiderlike arthros abundant in seas 300 mya
8. closest living relative of horseshoe crabs - arachnids: spiders, ticks, mites, scorpions. Most
arachnids live on land.
a. Scorpions are nocturnal hunters. eat mainly insects and spiders
b. mites- thousands can live in a few square centimeters of carpet or in a dust bunny;
not disease carriers; many people are allergic
9. crustaceans - nearly all aquatic- lobster, crayfish, shrimps, crabs, barnacles.
a. barnacles live in limestone shell; jointed appendages protrude from shell to catch
small invertebrates and suspended particles. body and appendages covered with
chitinous exoskeleton
10. centipedes and millipedes- jointed legs identify them as arthropods
a. millipedes- plant eaters
b. centipedes - carnivores with poison claws used in defense and to paralyze prey like
cockroaches and flies.
11. these 4 groups make up 170,000 living species. Insect numbers dwarf all other groups
H. CLASS Insecta- more total insects than all other animal species combined.
prominent on land for 400 my.
fewer in water, especially salt water
.
1. common features: 3 part body- head, thorax, abdomen
2. head- sensory antennae, eyes
3. several prs of mouthparts adapted for particular kinds of eating
a. biting and chewing plants - grasshopper
b. lapping up fluids- houseflies
c. piercing skin and sucking blood- mosquito
4. adults- 3 prs legs, 1 or 2 prs wings.
5. ability to fly- evolutionary success
6. metamorphosis- part of development. life stages may look like adult (incomplete) or
not (complete metamorphosis)
7. insect orders:
a. Orthoptera- grasshoppers, crickets, locusts, cockroaches, preying
mantises. most are herbivores. praying mantises are predators, use forelegs to
grip prey
b. Odonata- dragonflies and damselflies- two prs wings biting mouthparts,
carnivores. Larvae of larger species eat tadpoles and small fish
c. Hemiptera- true bugs- bedbugs, waterstriders, stink bugs. Most feed on
plant sap; bedbugs feed on blood. Two pairs of wings, fore wing thickened and
leathery.
d. Coleoptera- beetles- largest order in the animal kingdom.occur almost
everywhere from high mtns to streams, seashores, forests, desert, etc.
carnivores, herbivores, omnivores. 2 prs wings, only hindwings used in flight.
Forewings hard cover for hindwings.
e. Lepidoptera - moths and butterflies. 2 prs wings, hindwings smaller. wings
and body covered w/scales- dust. Mouthparts form a long drinking tube- nectar.
tube coils up when not in use.
f. Dipteran- flies- houseflies, fruitflies, gnats, mosquitoes. single pr wings, small
club shaped organ - haltere- balance in flight. mosquitoes- long mouthparts,
spread malaria.
g. Hymenoptera- ants, bees, wasps. 2 prs wings, use both in flight. hindwings
smaller, hooked to rear of forewings- behave as a single functional unit. Thorax
and abdomen separated by a narrow waist. Herbivores and omnivores. some
have complex social organization
I. Phylum Echinodermata- spiny skin, endoskeleton, water vascular system
1. eg sea urchins and sea stars,
2. lack segments
3. radially symmetrical as adults; larval stage bilaterally symmetrical. Echinoderms, therefore,
are not closely related to cnidarians.
4. spiny or rough skin, spines embedded
5. spines part of endoskeleton
6. vascular water system- network of water filled canals, that branch into tube feet
a. sea stars grab bivalve with tube feet and push stomach through mouth, into bivalve.
digests soft parts of prey.
7. strong powers of regeneration- regrow feet and arms, and sea cucumbers can regrow organs.
8. Sea urchins are spherical and have no arms; algae eaters
J. Phylum Chordata- our phylum. 4 distinctive features in embryos
1.
2.
3.
4.
dorsal hollow nerve cord
notochord - flexible longitudinal nod btn digestive tract and nerve cord
gill structures- in pharynx, region of digestive tube behind mouth
post anal tail (posterior to anus).
a. vertebrates
b. invertebrates
1). tunicates- large gill apparatus; adhere to rocks and boats. tunicate larvae
exhibit the above 4. Eat fine organic matter caught by mucus around gills
2). lancets- marine chordates- feed on suspended particles; have segmented
muscles to flex body side to side. Gill apparatus traps food.
II. Vertebrates comprise most of the Phylum Chordata. – Vertebrate Phylogeny
A. skull and backbone- repeating segments called vertebrae. Skeleton encloses main part of
nervous system
1. most vertebrates have skeletal parts supporting appendages; made of bone and/or cartilage;
mostly nonliving cells, but some are living to secrete nonliving material, so skeleton can grow
with the animal, unlike arthropods nonliving skeleton which must be shed.
B. Most vertebrates have hinged jaws
1. lampreys- fishlike, but lack paired fins and jaws- toothed, sucking disc for a mouth; more closely
related to extinct jawless relatives than any other living organism
2. jaws evolved from skeletal rods supporting the gills- hinged mouths allow wide variety
of
prey, not just feeding on suspended particles
C. Fish- jawed vertebrates with gills and paired fins
1. Class Chondrichthyes - cartilaginous fishes (sharks, rays and skates)
a. flexible skeleton made of cartilage
b. most sharks are adept predators- fast and streamlined, acute senses, power jaws
1). poor eyesight
2) great sense of smell
3). electrosensors- on head; can detect muscle movement in nearby animals
4). lateral line system: along side of body; can detect change in water pressureanimals swimming nearby
2. Class Osteichthyes- bony fishes, eg trout and goldfish. Skeleton reinforced by hard calcium
salts.
1). lateral line system
2). great smell
3). excellent eyesight
4). operculum- protective flap over gill that can pass water thru gill when fish is
stationary. sharks don’t have this.
5). swim bladder- gas filled sac for buoyancy
6). finsa). ray finned- fins supported by thin, flexible skeletal rays
b). lobe finned- fins are muscular, supported by stout bones- extinct
except for coelacanth; uses fins to waddle on ocean floor
D. Class Amphibia- mixture of terrestrial and aquatic adaptations; part of life cycle must be completed in water.
1. frogs- adult spends much time on land, lays eggs in water,
2. tadpole stage in water; gills, lateral line system, long finned tail.
3. metamorphosis into adult- terrestrial insect eater, 4 legs, external eardrums and lungs. No
lateral lines
4. Amphibians today account for only 8% of all vertebrae, but were first terrestrial vertebrates.
Possibly land vertebrates evolved from lobefins, who have lungs and gills; or, they evolved from
lungfishes.
E. Class Reptilia- snakes, lizards, turtles, crocs and alligators- several adaptations for terrestrial life not found
in amphibians1. skin covered with scales waterproofed with keratin (protein)
2. eggs covered with parchment shells to retain water- full life cycle on land
a. fluid filled sac called amnion
b. yolk- nourishment
3. ectothermic- do not use metabolism to control body temperature (cold blooded)
a. sit on warm rocks
b. go into shade if it gets too hot
4. historically very successful- dinosaurs
a. vegetarians and carnivores
b. may have been endothermic, none left today
5. dinosaur lineage survives today as birds
F. Class Aves- birds. evolved from 2 legged reptiles 150-200 mya.
1. inherited scales on legs
2. amniotic eggs,
3. toenails containing keratin
4. general body form
5. feathers were derived from dinosaur scales, a few dinos had downlike feathers; birds are
endothermic, feathers provide insulation
6. Archaeopteryx (= ancient wing, gk)
a. teeth
b. winged claws
c. tail w/ many vertebrae
d. not an ancestor of modern birds, extinct side lineage
7. Birds bodies are adapted for flight
a. lack teeth (extra weight)
b. tail- few small vertebrae
c. wings lack claws
d. feathers- hollow shafts
e. bones are hollow
f. large breast (flight) muscles (white meat)
g. some soar (turkey vultures) others beat wings really fast (hummers)
h. flightless species (emu) evolved from flying ancestors
G. Class Mammalia- evolved from reptiles 225 mya
1. during age of reptiles, a number of mouse sized insect eating nocturnal mammals.
2. diversity increased after downfall of reptiles
3. most mammals are terrestrial, but there are 1000 sp. of winged forms (bats) and 80 sp. of
aquatic forms (whales, dolphins, etc.).
4. endothermic- high rate of metabolism
5. hair- insulate body
6. mammary glands- produce milk to feed young
7. monotremes- egg laying mammals eg platypus in Australia
8. most mammals are born rather than hatched
a. nourished in mom by placenta- tissue that is both maternal and embryonic
9. marsupials- pouch mammals
a. brief gestation
b. development completed inside pouch (marsupium) attached to nipples
c. mostly in Australia (diversified greatly here), NZ, Central and South America
10. eutherians- commonly called placentals- more longlasting assoc. than marsupial placentas
a. placenta is red tissue in afterbirth
b. silvery tissue is amniotic sac- homologous with reptiles amnion
F. Phylogeny of Animal Kingdom
1. Embryonic development may give clues to evolutionary heritage- Coelomate animals
a. protostome- coelom develops from cells that form between digestive tube and
embryonic body wall.
b. deuterostome- coelom forms from hollow outgrowths of digestive tube of early
embryo
2. See table p. 392 and fig. 18.23 for recap
ch 18 Homework Questions/Lesson Objectives
1. Distinguish the animal kingdom from other kingdoms, and describe additional characteristics of animals.
2. Distinguish between: radial and bilateral symmetry; gastrovascular, pseudocoelomic and coelomic cavities; tissue,
organ and organ system; invertebrates and vertebrates.
3. Describe characteristics of species that belong to each of the phyla we covered.
4. Explain advantages of the following features to animal groups that evolved with t hem:
bilateral symmetry, coelomic cavities, segmentation, endoskeletons, jaws, amniotic eggs, feathers, and placentas.
5. Trace the phylogenetic relationships among animal phyla.