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Animals and Animal Diversity
The Nitty-gritty!
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Ch 32?
Basic Characteristics
•
•
•
•
•
•
Multicellular
Heterotrophic
Mobile
Eukaryotic
Lack cell walls
Bodies are held together by structural
proteins like collagen
• Nervous and muscular tissue unique to
animal kingdom
Reproduction and Development
• Most reproduce sexually, with the diploid
stage usually dominating the life cycle
• After a sperm fertilizes an egg, the zygote
undergoes rapid cell division called cleavage
• Cleavage leads to formation of a blastula
• The blastula undergoes gastrulation,
forming a gastrula with different layers of
embryonic tissues
Video: Sea Urchin Embryonic Development
Fig. 32-2-3
Blastocoel
Cleavage
Endoderm
Cleavage Blastula
Ectoderm
Zygote
Eight-cell stage
Gastrulation
Blastocoel
Cross section
of blastula
Gastrula
Blastopore
Archenteron
• Many animals have at least one larval
stage (sexually immature morphology
that is different from the adult), which
eventually undergoes metamorphosis
• All animals, and only animals, have Hox
genes that regulate the development of
body form
Paleozoic Era (542–251 Million Years Ago) – The
rise of the animal kingdom
• The Cambrian explosion (535 to
525 million years ago) marks the
earliest fossil appearance of
many major groups of living
animals
• There are several hypotheses
regarding the cause of the
Cambrian explosion
– New predator-prey relationships
– A rise in atmospheric oxygen
– The evolution of the Hox gene complex
Concept 32.3: Animals can be
characterized by “body plans”
• Zoologists sometimes categorize animals
according to a body plan, a set of
morphological and developmental traits
Symmetry
• Animals can be
categorized according
to the symmetry of their
bodies, or lack of it
• Some animals have
radial symmetry, while
others show bilateral
symmetry.
Radial
Bilateral
• Two-sided symmetry is called bilateral
symmetry
• Bilaterally symmetrical animals have:
–
–
–
–
A dorsal (top) side and a ventral (bottom) side
A right and left side
Anterior (head) and posterior (tail) ends
Cephalization, the development of a head
Tissues
• Animal body plans also vary according to
the organization of the animal’s tissues
• Tissues are collections of specialized
cells isolated from other tissues by
membranous layers
• During development, three germ layers
give rise to the tissues and organs of the
animal embryo
• Ectoderm is the germ layer covering the
embryo’s surface
• Endoderm is the innermost germ layer
and lines the developing digestive tube,
called the archenteron
• Diploblastic animals have ectoderm and
endoderm
• Triploblastic animals also have an
intervening mesoderm layer; these
include all bilaterians
Body Cavities
• Most triploblastic animals possess a
body cavity
• A true body cavity is called a coelom and
is derived from mesoderm
• Coelomates are animals that possess a
true coelom
Fig. 32-8a
Coelom
Body covering
(from ectoderm)
Digestive tract
(from endoderm)
(a) Coelomate
Tissue layer
lining coelom
and suspending
internal organs
(from mesoderm)
• A pseudocoelom is a body cavity derived
from the mesoderm and endoderm
• Triploblastic animals that possess a
pseudocoelom are called
pseudocoelomates
Fig. 32-8b
Body covering
(from ectoderm)
Pseudocoelom
Digestive tract
(from endoderm)
(b) Pseudocoelomate
Muscle layer
(from
mesoderm)
• Triploblastic animals that lack a body
cavity are called acoelomates
Fig. 32-8c
Body covering
(from ectoderm)
Tissuefilled region
(from
mesoderm)
Wall of digestive cavity
(from endoderm)
(c) Acoelomate
Protostome and Deuterostome
Development
• Based on early development, many
animals can be categorized as having
protostome development or
deuterostome development
Cleavage
• In protostome development, cleavage is
spiral and determinate
• In deuterostome development, cleavage
is radial and indeterminate
• With indeterminate cleavage, each cell in
the early stages of cleavage retains the
capacity to develop into a complete
embryo
• Indeterminate cleavage makes possible
identical twins, and embryonic stem cells
Fig. 32-9
Protostome development
(examples: molluscs,
annelids)
Deuterostome development
(examples: echinoderm,
chordates)
Eight-cell stage
Eight-cell stage
Spiral and determinate
(a) Cleavage
Radial and indeterminate
(b) Coelom formation
Key
Coelom
Ectoderm
Mesoderm
Endoderm
Archenteron
Coelom
Mesoderm
Blastopore
Blastopore
Solid masses of mesoderm
split and form coelom.
Mesoderm
Folds of archenteron
form coelom.
Anus
Mouth
(c) Fate of the blastopore
Digestive tube
Mouth
Mouth develops from blastopore.
Anus
Anus develops from blastopore.
Fig. 32-9a
Protostome development
(examples: molluscs,
annelids)
Eight-cell stage
Spiral and determinate
Deuterostome development
(examples: echinoderms,
chordates)
Eight-cell stage
Radial and indeterminate
(a) Cleavage
Coelom Formation
• In protostome development, the splitting
of solid masses of mesoderm forms the
coelom
• In deuterostome development, the
mesoderm buds from the wall of the
archenteron to form the coelom
Fig. 32-9b
Protostome development
(examples: molluscs,
annelids)
Deuterostome development
(examples: echinoderms,
chordates)
(b) Coelom formation
Coelom
Key
Ectoderm
Mesoderm
Endoderm
Archenteron
Coelom
Mesoderm
Blastopore
Solid masses of mesoderm
split and form coelom.
Blastopore
Mesoderm
Folds of archenteron
form coelom.
Fate of the Blastopore
• The blastopore forms during gastrulation
and connects the archenteron to the
exterior of the gastrula
• In protostome development, the
blastopore becomes the mouth
• In deuterostome development, the
blastopore becomes the anus
Fig. 32-9c
Protostome development
(examples: molluscs,
annelids)
Deuterostome development
(examples: echinoderms,
chordates)
Anus
Mouth
(c) Fate of the blastopore
Key
Digestive tube
Anus
Mouth
Mouth develops from blastopore. Anus develops from blastopore.
Ectoderm
Mesoderm
Endoderm
Modeling Time
• Let’s go back to the lab.
– Take a sheet of paper with you
– Pick up a direction sheet
– Get 2 colors of dough
Invertebrates
Those without backbones – make up about 95%
of animals
Fig. 33-2
Calcarea
and Silicea
Cnidaria
ANCESTRAL
PROTIST
Eumetazoa
Common
ancestor of
all animals
Lophotrochozoa
Bilateria
Ecdysozoa
Deuterostomia
Sponges
• Lack true tissues and organs
• Live in water (both fresh and salt)
• suspension feeders, capturing food
particles suspended in the water that pass
through their body
• Most sponges are hermaphrodites: Each
individual functions as both male and female
Fig. 33-4
Choanocyte
Osculum
Flagellum
Collar
Food particles
in mucus
Choanocyte
Azure vase sponge (Callyspongia
plicifera)
Spongocoel
Phagocytosis of
food particles
Pore
Epidermis
Spicules
Water
flow
Amoebocytes
Mesohyl
Amoebocyte
Cnidarians
• include jellies, corals, and hydras
• exhibit a relatively simple diploblastic, radial
body plan
• body plan 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
• Carnivores that use tentacles to capture prey
– Armed with enidocytes – cells that fxn in defense
and capturing prey
– Nematocysts – organelles that eject a stinging
thread
Fig. 33-5
Mouth/anus
Polyp
Tentacle
Medusa
Gastrovascular
cavity
Gastrodermis
Body
stalk
Mesoglea
Epidermis
Tentacle
Mouth/anus
Fig. 33-6
Tentacle
Cuticle
of prey
Thread
Nematocyst
“Trigger”
Thread
discharges
Cnidocyte
Thread
(coiled)
Flatworms
• live in marine, freshwater, and damp
terrestrial habitats
• acoelomates
• They are flattened dorsoventrally and have a
gastrovascular cavity
• Gas exchange takes place across the surface
Fig. 33-10
Pharynx
Gastrovascular
cavity
Mouth
Eyespots
Ganglia
Ventral nerve cords
Tapeworms
• Tapeworms are parasites of vertebrates
and lack a digestive system
• Tapeworms absorb nutrients from the
host’s intestine
• Fertilized eggs, produced by sexual
reproduction, leave the host’s body in
feces
Rotifers
• Rotifers are tiny animals that inhabit fresh water, the
ocean, and damp soil
• Rotifers have an alimentary canal, a digestive tube
with a separate mouth and anus that lies within a
fluid-filled pseudocoelom
• Rotifers reproduce by parthenogenesis, in which
females produce offspring from unfertilized eggs
• Some species are unusual in that they lack males
entirely
Mollusca
• Phylum Mollusca includes snails and slugs,
oysters and clams, and octopuses and squids
• Most molluscs are marine
• Molluscs are soft-bodied animals, but most
are protected by a hard shell
• All molluscs have a similar body plan with
three main parts:
– Muscular foot
– Visceral mass
– Mantle
• Many molluscs also have a water-filled
mantle cavity, and feed using a rasplike
radula
Fig. 33-15
Nephridium
Visceral mass
Coelom
Heart
Intestine
Gonads
Mantle
Stomach
Shell
Mantle
cavity
Mouth
Radula
Anus
Gill
Foot
Nerve
cords
Esophagus
Mouth
Radula
Gastropods
•
•
•
•
Most gastropods are marine,
Most have a single, spiraled shell
Slugs lack a shell or have a reduced shell
The most distinctive characteristic of
gastropods is torsion, which causes the
animal’s anus and mantle to end up above its
head
Fig. 33-17
(a) A land snail
(b) A sea slug
Fig. 33-18
Mantle
cavity
Anus
Mouth
Stomach
Intestine
Bivalves
• Molluscs of class Bivalvia include many
species of clams, oysters, mussels, and
scallops
• They have a shell divided into two
halves
• The mantle cavity of a bivalve contains
gills that are used for feeding as well as
gas exchange
Fig. 33-19
Fig. 33-20
Mantle
Hinge area
Coelom
Gut
Heart Adductor
muscle
Digestive
gland
Anus
Mouth
Excurrent
siphon
Shell
Palp
Foot
Mantle
cavity
Gonad
Gill
Water
flow
Incurrent
siphon
Cephalopods
Octopus
• Class Cephalopoda
includes squids and
octopuses,
carnivores with beaklike jaws surrounded
by tentacles of their
modified foot
• Cephalopods have a
closed circulatory
system, welldeveloped sense
organs, and a
complex brain
Squid
Chambered
nautilus
Annelids
• Annelids have bodies composed of a
series of fused rings
Concept 33.4: Ecdysozoans are
the most species-rich animal
group
• Ecdysozoans are covered by a tough
coat called a cuticle
• The cuticle is shed or molted through a
process called ecdysis
• The two largest phyla are nematodes and
arthropods
Nematodes
• Nematodes, or roundworms, are found in
most aquatic habitats, in the soil, in moist
tissues of plants, and in body fluids and
tissues of animals
• They have an alimentary canal, but lack a
circulatory system
• Reproduction in nematodes is usually sexual,
by internal fertilization
• Some are parasitic
Arthropods
• The arthropod body plan
consists of a segmented
body, hard exoskeleton,
and jointed appendages,
Fig. 33-29
Cephalothorax
Antennae
(sensory
reception)
Head
Abdomen
Thorax
Swimming appendages
(one pair located
under each
abdominal segment)
Walking legs
Pincer (defense)
Mouthparts (feeding)
• The body of an arthropod is completely
covered by the cuticle, an exoskeleton made
of layers of protein and the polysaccharide
chitin
• When an arthropod grows, it molts its
exoskeleton
• Arthropods have an open circulatory
system in which fluid called hemolymph is
circulated into the spaces surrounding the
tissues and organs
Echinoderms
• Sea stars and most other echinoderms are slowmoving or sessile marine animals
• A thin epidermis covers an endoskeleton of hard
calcareous plates
• Echinoderms have a unique water vascular
system, a network of hydraulic canals branching
into tube feet that function in locomotion, feeding,
and gas exchange
• Males and females are usually separate, and sexual
reproduction is external
Fig. 33-39
Anus
Stomach
Spine
Gills
Central disk
Digestive glands
Madreporite
Radial
nerve
Ring
canal
Gonads
Ampulla
Podium
Radial canal
Tube
feet
Fig. 33-40
(a) A sea star (class Asteroidea)
(b) A brittle star (class Ophiuroidea)
(c) A sea urchin (class Echinoidea)
(d) A feather star (class Crinoidea)
(e) A sea cucumber (class Holothuroidea)
(f) A sea daisy (class Concentricycloidea)
Vertebrates
The ones with backbones
Chordata
• Four key characters of chordates:
– Notochord
– Dorsal, hollow nerve cord
– Pharyngeal slits or clefts
– Muscular, post-anal tail
Fig. 34-3
Dorsal,
hollow
nerve cord
Muscle
segments
Notochord
Mouth
Anus
Muscular,
post-anal tail
Pharyngeal
slits or clefts
• The notochord is a longitudinal, flexible rod
between the digestive tube and nerve cord
• It provides skeletal support throughout most
of the length of a chordate
• In most vertebrates, a more complex, jointed
skeleton develops, and the adult retains only
remnants of the embryonic notochord
• The nerve cord of a chordate embryo
develops from a plate of ectoderm that rolls
into a tube dorsal to the notochord
• The nerve cord develops into the central
nervous system: the brain and the spinal cord
• In most chordates, grooves in the pharynx called
pharyngeal clefts develop into slits that open to the
outside of the body
• Functions of pharyngeal slits:
– Suspension-feeding structures in many invertebrate chordates
– Gas exchange in vertebrates (except vertebrates with limbs, the
tetrapods)
– Develop into parts of the ear, head, and neck in tetrapods
• Chordates have a tail posterior to the
anus
• In many species, the tail is greatly
reduced during embryonic development
• The tail contains skeletal elements and
muscles
• It provides propelling force in many
aquatic species
Early Chordate Evolution
• Ancestral chordates may have resembled
lancelets
• Gene expression in lancelets holds clues
to the evolution of the vertebrate form
Fig. 34-6
BF1
Otx
Hox3
Nerve cord of lancelet
embryo
BF1
Otx
Hox3
Brain of vertebrate embryo
(shown straightened)
Forebrain
Midbrain
Hindbrain
Concept 34.2: Craniates are
chordates that have a head
• The origin of a head opened up a
completely new way of feeding for
chordates: active predation
• Craniates share some characteristics:
a skull, brain, eyes, and other sensory
organs
Derived Characters of Craniates
• Craniates have two clusters of Hox
genes; lancelets and tunicates have only
one cluster
• One feature unique to craniates is the
neural crest, a collection of cells near
the dorsal margins of the closing neural
tube in an embryo
• Neural crest cells give rise to a variety of
structures, including some of the bones
and cartilage of the skull
Fig. 34-7
Dorsal edges
of neural plate
Neural
crest
Notochord
Neural
tube
Migrating neural
crest cells
Derived Characters of
Vertebrates
• Vertebrates have the following derived
characters:
– Vertebrae enclosing a spinal cord
– An elaborate skull
– Fin rays, in the aquatic forms
Lampreys
• Lampreys (Petromyzontida) represent the
oldest living lineage of vertebrates
• They are jawless vertebrates inhabiting
various marine and freshwater habitats
• They have cartilaginous segments
surrounding the notochord and arching
partly over the nerve cord
Chondrichthyans (Sharks, Rays,
and Their Relatives)
• Chondrichthyans (Chondrichthyes)
have a skeleton composed primarily of
cartilage
• The cartilaginous skeleton evolved
secondarily from an ancestral mineralized
skeleton
• Includes the sharks, rays, and skates
Pelvic fins
Fig. 34-16
Ray-Finned Fishes and Lobe-Fins
Spinal cord
Swim
bladder
Dorsal fin
Brain
Adipose fin
(characteristic
of trout)
Caudal
fin
Nostril
Anal fin
Cut edge
of operculum
Liver
Gills
Heart
Kidney
Lateral
line
Anus
Stomach
Intestine
Gonad
Pelvic
fin
Urinary
bladder
Fishes control their buoyancy with an air sac
known as a swim bladder
Fig. 34-17
(a) Yellowfin tuna (Thunnus albacares)
(b) Clownfish (Amphiprion ocellaris)
(c) Sea horse
(Hippocampus
us)
ramulos
(d) Fine-spotted moray eel
(Gymnothorax dovii)
Tetrapods
• Tetrapods have some specific
adaptations:
– Four limbs, and feet with digits
– Ears for detecting airborne sounds
Fig. 34-19
Bones
supporting
gills
Tetrapod
limb
skeleton
Amphibians
• Amphibian means “both ways of life,”
referring to the metamorphosis of an
aquatic larva into a terrestrial adult
• Most amphibians have moist skin that
complements the lungs in gas exchange
• Fertilization is external in most species,
and the eggs require a moist
environment
Fig. 34-22
(a) Tadpole
(b) During
metamorphosis
(c) Mating adults
Concept 34.6: Amniotes are tetrapods that
have a terrestrially adapted egg
• Amniotes are a group of tetrapods whose
living members are the reptiles, including
birds, and mammals
• Have an amniotic egg, which contains
membranes that protect the embryo
• Other terrestrial adaptations include relatively
impermeable skin and the ability to use the
rib cage to ventilate the lungs
Fig. 34-25
Chorion
Amnion
Allantois
Yolk sac
Embryo
Amniotic
cavity
with
amniotic
fluid
Shell
Yolk
(nutrients)
Albumen
Reptiles
• Reptiles have scales that create a waterproof
barrier
• They lay shelled eggs on land
• Most reptiles are ectothermic, absorbing
external heat as the main source of body
heat
• Birds are endothermic, capable of keeping
the body warm through metabolism
Fig. 34-26
Birds
• Many characters of birds are
adaptations that facilitate flight
• The major adaptation is wings with
keratin feathers
• Other adaptations include lack of a
urinary bladder, females with only one
ovary, small gonads, and loss of teeth
Fig. 34-28
Finger 1
(b) Bone structure
Palm
Finger 2
(a) Wing
Forearm
Shaft
Vane
Finger 3
Wrist
Shaft
Barb
Barbule
Hook
(c) Feather structure
Fig. 34-29
Toothed beak
Airfoil wing
with contour
feathers
Wing claw
Long tail with
many vertebrae
Mammals
• Mammals have
– Mammary glands, which produce milk
– Hair
– A larger brain than other vertebrates of
equivalent size
– Differentiated teeth
three living lineages of mammals
emerged: monotremes, marsupials,
and eutherians
• Monotremes are a small group of egg-laying
mammals consisting of echidnas and the
platypus
• Marsupials – when the embryo develops within
a placenta in the mother’s uterus
• A marsupial is born very early in its development
• It completes its embryonic development while
nursing in a maternal pouch called a marsupium
• eutherians have a longer period of pregnancy
• Young eutherians complete their embryonic
development within a uterus, joined to the
mother by the placenta
Fig. 34-32
Fig. 34-33
(a) A young brushtail possum
(b) Long-nosed bandicoot
Fig. 34-34
Marsupial
mammals
Plantigale
Eutherian
mammals
Deer mouse
Marsupial mole
Marsupial
mammals
Wombat
Woodchuck
Mole
Tasmanian devil
Sugar glider
Eutherian
mammals
Wolverine
Flying squirrel
Kangaroo
Patagonian cavy
Primates
• Most primates have hands and feet
adapted for grasping
• Other derived characters of primates:
– A large brain and short jaws
– Forward-looking eyes close together on the
face, providing depth perception
– Complex social behavior and parental care
– A fully opposable thumb (in monkeys and
apes)
Fig. 34-36
Fig. 34-38
(a) New World monkey
(b) Old World monkey
Humans
• A number of characters distinguish
humans from other apes:
– Upright posture and bipedal locomotion
– Larger brains
– Language capabilities and symbolic thought
– The manufacture and use of complex tools
– Shortened jaw
– Shorter digestive tract
Fig. 34-40
Paranthropus
robustus
0
Homo
ergaster
Paranthropus
boisei
0.5
Homo
Homo
neanderthalensis sapien
s
?
1.0
Australopithecus
africanus
1.5
2.0
2.5
Kenyanthropus
platyops
Australopithecus
garhi
Australo3.0 pithecus
anamensis
3.5
Homo
rudolfensis
4.0
4.5
5.0
Ardipithecus
ramidus
Australopithecus
afarensis
5.5
6.0
6.5
7.0
Homo
erectus
Orrorin tugenensis
Sahelanthropus
tchadensis
Homo
habilis