Biodiversity 3: Animals
Learning Outcomes
In this chapter students will:
10.1 Summarize the evolutionary origins of animals, and describe the adaptations that
distinguish the animal kingdom from other kingdoms.
10.2 Describe the nine major branches in the phylogeny of animals, emphasizing the
adaptations that distinguish each branch.
10.3 Describe the anatomical and physiological characteristics of the chordate phylum,
including the key adaptations of subgroups (notably fish, amphibians, reptiles and
mammals).
10.4 Outline the evolutionary relationships and key distinguishing characteristics of the
major groups of mammals (notably primates).
Module Outlines
10.1. Animals are multicellular consumers that evolved from colonial protists.
• CORE IDEA: Animals are multicellular eukaryotes that obtain nutrition by eating other
organisms. Animals evolved from colonial protists around 600 million years ago. There
are now nine major phyla of animals that can be distinguished by specific body features.
A. The first animals evolved around 600 million years ago.
1. This date is based on the fossil record and DNA evidence.
B. Characteristics of animals
1. Mode of nutrition
a. All animals are heterotrophs.
i. All animals eat other organisms.
ii. Other organisms are a source of nutrients and materials for building body
structures.
iii. Animals differ from autotrophs, organisms that make their own food (plants).
2. Nervous system
a. Most animals have one that helps control body systems.
3. Reproductive system
a. Some animals are capable of asexual reproduction.
b. Most animals use sexual reproduction through joining of sperm and egg.
4. Muscles
a. Most animals have muscle cells organized into muscle tissues.
b. Muscles help propel animals and move their body parts.
5. Multicellular
a. All animals are multicellular.
b. Most animals have tissues.
i. Tissues consist of many similar cells that act together to perform a specific
function.
6. Eukaryotes
a. All animals are composed of eukaryotic cells.
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i. Eukaryotic cells each contain a nucleus and other organelles surrounded by
membranes.
7. Diploid
a. Most animals have diploid cells.
b. Diploid cells contain homologous pairs of chromosomes in the nucleus.
i. One member of each pair is inherited from each parent.
c. In most animals, the only haploid cells are sperm and egg.
8. Developmental stages
a. All animals pass through common stages during development.
C. Animal evolution
1. The first animals developed from colonies of protists that most likely had flagella.
a. This is based on fossil evidence and DNA.
b. It happened approximately 600 million years ago.
2. “Cambrian explosion”
a. It happened 540 million years ago.
b. There was a rapid diversification of animals, resulting in a huge variety of animal
forms.
c. Most animal phyla still around today were established around this time.
D. Animal evolutionary tree
1. There are 35 or so known animal phyla.
2. The majority can be grouped into nine phyla.
3. The present phylogenetic tree is based on structural features and genetic analyses.
4. Branch points:
a. Tissues
i. Tissues are groups of similar cells that work together to perform a function.
ii. The presence of tissues is the first major branch point in the phylogenetic tree.
b. Symmetry
i. Asymmetry or lack of symmetry is found only in sponges
ii. Radial symmetry is found only in cnidarians.
iii. All other animals have bilateral symmetry.
10.2. Sponges and cnidarians have unusual body features.
• CORE IDEA: Sponges are mostly marine organisms that lack body symmetry and
tissues. Cnidarians are also primarily marine; they have tissues, radial body symmetry,
and stinging cells.
A. The vast majority of animals are invertebrates.
1. Invertebrates are animals without backbones.
B. Sponges
1. Longest evolutionary history and simplest anatomy
a. Anatomy
i. They have a large central cavity.
ii. Holes in body wall draw nutrient-containing water into central cavity.
iii. Most sponges have a skeleton made of small stiff structures.
2. Wide variety of shapes, sizes, and colors
3. Distinctive characteristics
a. Asymmetrical
i. Irregularly shaped
ii. No planes of symmetry
b. No tissues such as nerves and muscles
i. Do have specialized cells that perform specific functions
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ii. Examples: Feeding cells and skeleton-producing cells
c. Sessile—anchored to one spot
i. Unlike most animals, they remain anchored in one spot.
4. Gallery of sponges
a. There are 9,000 species of sponges.
b. Most live in salt water, but 100 species live in fresh water.
C. Cnidarians
1. There are 10,000 species of cnidarians.
2. Almost all are marine (sea dwelling).
3. They include sea anemones, hydras, corals, and jellies (or jellyfish).
4. Two body forms:
a. Stationary polyp
i. Grow while fixed to larger objects
b. Floating medusa
i. Floats mouth down, either drifting or contracting its body
c. Some exist as only one form; others change form.
5. Characteristics:
a. Cells are organized into tissues.
i. Epithelial tissue lines the digestive and circulatory cavity.
ii. Water moves in and out of the gastrovascular cavity through a single opening.
iii. The gastrovascular cavity is the central digestive compartment and circulates
nutrients and oxygen.
b. They exhibit radial symmetry.
i. All body parts are arranged around a central axis.
c. The most distinguishing feature of cnidarians is the presence of stinging cells on
their tentacles.
i. Used in defense and to paralyze prey
ii. Contain threads that when discharged can cause painful stings
6. A gallery of cnidarians:
a. Sea anemone
b. Sea wasp, type of jelly
c. Brown hydra
d. Boulder brain coral
i. Large colony that secretes a hard skeleton that accumulates into the “rocks” we
call coral.
10.3. Three phyla of worms have unique structures and belong to separate
evolutionary lineages.
• CORE IDEA: Flatworms, some of which can parasitize humans, lack a digestive tract.
Annelids—with bodies made of fused repeating segments—and roundworms both have
complete digestive tracts. Of the three major phyla of worms, roundworms belong to a
separate evolutionary lineage.
A. Comparison of three worm phyla—flatworms, annelids, and roundworms
1. Same overall body shape
a. Bilaterally symmetrical, long, and thin
2. Considerable variation
3. Each phylum has distinctive features reflecting its evolutionary heritage.
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B. The evolution of worms
1. Organisms that appear closely related may have distinct evolutionary histories.
2. Roundworms evolved in a separate lineage from the other two worm phyla.
C. Flatworms
1. 20,000 species
2. Marine, freshwater, and damp terrestrial habitats
4. Sizes from 1 mm to dozens of feet
5. Gastrovascular cavity—single opening acting as both mouth and anus
6. Several species cause human diseases.
a. Tapeworms
b. Blood flukes
7. Anatomy
a. Bilateral symmetry
b. Gastrovascular cavity
c. Eye spots—crude sensory structures that can detect light
d. Simple brain—clusters of nerve cells
8. Gallery of flatworms
a. Tapeworm
b. Leopard flatworm
C. Annelids
1. Segmentation is a key evolutionary adaptation.
a. Segmentation is the division of the body along its length into a series of repeated
segments.
b. This allows for greater flexibility and more complex movement.
2. 16,000 species
3. Marine, freshwater, and damp terrestrial habitats
4. Anatomy
a. Complete digestive tract—they have a mouth and anus.
b. Closed circulatory system—blood is pumped through enclosed vessels by a series
of hearts.
c. Body segments—they have repeated segments, with many internal organs repeated
in each segment.
5. Gallery of annelids
a. Leech—some species suck blood.
b. Earthworm—improves soil by adding waste to soil.
c. Polychaetes—mostly marine; use feathery appendages to trap food.
D. Roundworms
1. Nematodes
2. Small, cylindrical, and tapered at both ends
3. Not segmented
4. Found in nearly every ecosystem on Earth
a. Many parasitic species
b. In soil, help recycle nutrients
5. Anatomy
a. Complete digestive tract
6. Examples
a. Soil nematodes break down organic refuse.
b. Heartworms—common parasite of dogs and cats spread by mosquitoes.
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10.4. Mollusks are a very diverse phylum.
• CORE IDEA: Mollusks are a diverse group of bilaterally symmetrical soft-bodied
animals, many with shells. Mollusks include gastropods, hinged bivalves, and agile
cephalopods
A. Mollusks
1. Soft-bodied animals
2. Many protected by a hard shell
3. 100,000 known species
4. Mostly marine
5. Body plan
a. Bilateral symmetry divides the body down the middle into two nearly identical
halves.
B. Features of a typical mollusk
1. Three main parts
a Muscular foot, used to move the body
b. Visceral mass—contains most of the internal organs
c. A fold of tissue called the mantle encloses visceral mass and secretes the shell (if
present).
2. Other typical features
a. Radula is a saw-like organ that can cut and scrape up food.
b. Shell may be external or internal, or there may be no shell at all.
c. Gills are used to extract oxygen from water.
d. Open circulatory system pumps blood and distributes nutrients and oxygen.
3. A gallery of mollusks
a. Gastropods (snails and slugs)
i. Most numerous
ii. Saltwater and freshwater
iii. Examples: flamingo tongue snail, banana slug, and garden snail
b. Bivalves (clams, mussels, oysters)
i. Marine and freshwater
ii. Most sedentary
iii. Two shells connected by a hinge
iv. Examples: bay scallop, green mussel, and giant clam
c. Cephalopods (squid and octopuses)
i. Fast, agile marine predators
ii. Some with a large, heavy shell (nautiluses), some with small internal shell
(squids), and some with no shell (octopuses)
10.5. The arthropods are extremely diverse and numerous.
• CORE IDEA: The arthropods include more individuals and species than any other animal
phylum. Common groups of arthropods include arachnids (such as spiders), crustaceans
(such as crabs), and insects (such as grasshoppers).
A. Arthropods are the most numerous and diverse animal phylum.
1. Over a million identified species
2. Over a billion individuals
3. Share basic characteristics
a. Segmented body
b. Tough exoskeleton
c. Several jointed appendages
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B. Features of a typical arthropod
1. Body segments
a. Body is divided into segments along its length.
b. Within segments are specialized structures that perform specific functions.
c. Anatomy
i. Head
ii. Thorax
iii. Abdomen
iv. Jointed appendages for swimming (tail), walking (legs), and defense (pincers)
v. Sensory organs—antenna and eyes on stalks
2. Exoskeleton
a. Hard exoskeleton provides protection and points of attachment for muscles.
b. They must shed exoskeleton to grow in size.
C. Arachnids and horseshoe crabs
1. All share a specialized appendage for feeding.
2. Horseshoe crabs have changed little in hundreds of millions of years.
3. Arachnids
a. These are eight-legged arthropods.
b. Included are spiders, ticks, scorpions, and mites.
c. Most are terrestrial carnivores.
i. Some use fangs loaded with venom.
4. Horseshoe crabs
a. Changed little in hundreds of millions of years
5. Examples
a. Chilean rose tarantula
b. Rocky mountain wood tick
c. Atlantic horseshoe crab
d. Yellow desert scorpion
D. Crustaceans
1. Nearly all (except pill bugs) live in water.
2. They are the dominant group of arthropods in marine and freshwater habitats.
3. Many are valuable food sources (shrimp, lobster, crabs, etc.).
4. Examples
a. Goose-necked barnacles
b. Common rough woodlouse—a type of pill bug
c. Brown crab
F. Insects
1. They outnumber all other animals combined.
2. Branched tubes deliver air to body tissues, enabling insects to breath on land.
2. Most have a head, thorax, and abdomen.
3. They have three pairs of legs.
4. They have one pair of antennae.
5. Many have two pairs of wings.
10.6. Echinoderms are a sister phylum to the chordates.
A. Echinoderms
1. There are 7,000 species and all are marine.
2. They are named after the Greek word for “spiny skin.”
3. This phylum is the most closely related to chordates (including us).
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B. Features of a typical echinoderm
1. Spiny surface—have a bumpy or spiky surface
2. Water vascular system
a. Uses seawater as blood
b. A network of water-filled canals allows the animal to exchange gases with the
environment.
3. Mouth
a. Sea star feeds by pulling apart the two shells of a bivalve and pushing its stomach
through the opening into the bivalve.
4. Tube feet
a. Extensions of the water-vascular system that end in tiny suction cups
5. Endoskeleton
a. Calcium-hardened internal skeleton
6. Regeneration
a. Can regenerate lost body parts if a piece of the central body remains
C. Body symmetry
1. Most echinoderms have five-fold symmetry as adults.
2. Larvae are bilaterally symmetrical.
3. Gallery of echinoderms
a. Northern sea urchin
b. Bennett’s feather star
c. Brittle star
d. Chocolate chip sea cucumber
4. Our evolutionary kinship with echinoderms
a. In echinoderms and chordates, the first opening in the ball of cells develops into the
anus.
b. In all other major phyla, the first opening is the mouth.
10.7. Vertebrates belong to the chordate phylum.
• CORE IDEA: Chordates share four features (hollow nerve cord, notochord, pharyngeal
slits, tail), all of which are visible in the embryo. Most chordates are vertebrates, meaning
they also have an endoskeleton with a backbone and skull.
A. The chordate phylum has two broad divisions.
1. Invertebrate chordates
2. Vertebrates
B. Features of chordates
1. Tail
a. A tail is found in all chordate embryos.
b. It extends posterior (back) of the anus.
c. It is the “tailbone” of the backbone in adult humans.
2. Notochord
a. This is a flexible supporting rod along the back.
b. In adult humans, this develops into a component of the spinal column.
3. Nerve cord
a. This runs along the dorsal (top) surface.
b. In adult humans, this becomes part of the spinal cord.
4. Pharyngeal slits
a. These are grooves located behind the mouth.
b. In adult humans, parts remain as the eustachian tubes that link the ears to the throat.
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C. Invertebrate chordates
1. They lack a skull and backbone.
2. Lancelets
a. These are small, sword-shaped animals.
b. They burrow into the sand and filter water to capture food.
3. Tunicates
a. They adhere to stationary objects like rocks.
b. Tunicates feed by filtering seawater.
D. Chordate evolution
1. Diagram of main groups of chordates and novel features for each group
2. Examine the phylogenetic tree on page 287.
E. Features of vertebrates
1. Most chordates are vertebrates—animals with backbones.
2. All vertebrates have the four features common to all chordates plus an endoskeleton
(internal skeleton) that includes a backbone and skull.
10.8. The first vertebrates to evolve were fishes.
• CORE IDEA: There are several lineages of modern fishes, including hagfishes (which
lack jaws and recognizable backbones), lampreys (which lack jaws), cartilaginous fishes
(with skeletons made of cartilage), and bony fishes (with calcium-hardened skeletons).
A. The first vertebrates evolved 500 million years ago.
1. Devonian period (419–359 million years ago)—called “Age of Fish”
B. Jawless fishes
1. They have skulls but lack jaws.
2. Hagfish
a. There are 40 species.
b. Have a skull but lack a recognizable backbone in the adult
c. Scavenge along sea floor
d. Exude slime when threatened
3. Lampreys
a. Have a skull and backbone but lack a jaw
b. Most live as parasites by attaching suckers to sides of larger fish and feeding on blood.
C. Cartilaginous fishes
1. These are the first vertebrates with jaws.
2. They evolved 470 million years ago.
3. Their flexible skeletons are made of cartilage.
4. There are 800 species, including sharks and rays.
5. Anatomy
a. Electrosensors detect electric fields produced by muscle contractions of prey.
b. Gills—Cartilaginous fishes must constantly move to keep water flowing over gills.
c. Lateral line system—a row of sensory organs along sides that detect changes in
water pressure produced by nearby prey
d. Jaws—supported by a hinged pair of bones
6. Examples
a. Hammerhead shark
b. Stingray
D. Bony fishes
1. There are more species of bony fishes than any other group of vertebrates.
2. They dominate freshwater and marine habitats.
3. Anatomy
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a. Skeletons are reinforced with calcium.
b. Operculum protects gills.
i. Moving the operculum allows oxygenated water to flow over gills, even when
the fish is not moving.
c. Eyes—They have good eyesight and a keen sense of smell.
d. Gills extract oxygen from water.
d. Scales—Most bony fish have scales covering their skin.
e. Lateral line system—can detect movement in the surrounding water.
f. Swim bladder—a gas-filled sac that helps keep a fish buoyant.
4. Examples
a. Lake trout
b. Skipjack tuna
c. Spotfin butterflyfish
d. Thorny seahorse
E. Lobe-finned fishes
1. They have muscular fins supported by rod-shaped bones.
a. Similar to amphibian limb bones
2. They include the line that gave rise to amphibians.
3. Examples
a. Coelacanth, which were once thought to be extinct
b. Lung fishes, which have a connection between the swim bladder and digestive
system that lets them extract oxygen from air
10.9. Amphibians and reptiles were the first tetrapods to occupy land.
• CORE IDEA: Amphibians are tetrapods—four-legged vertebrates that live on land—but
they are tied to the water to reproduce. Reptiles, including birds, reproduce via an
amniotic egg that can survive on dry land.
A. Tetrapods
1. All terrestrial (land-dwelling) vertebrates are tetrapods.
a. “Four feet”—animals with four limbs
2. First tetrapods were amphibians descended from lobe-finned fishes.
a. Fishes with primitive lungs and muscular, bony fins
3. All modern tetrapods evolved from these first tetrapods.
B. Amphibians
1. They exhibit a blend of aquatic and terrestrial adaptations.
a. Aquatic adaptations
i. Eggs—They lack shells and must remain in the water.
ii. Tadpoles—They are frog larvae.
iii. Gills—Tadpoles have gills and fins.
iv. Lateral line—Like fish, amphibians use this as a sensory organ.
b. Terrestrial adaptations
i. Lungs are used to breathe air.
ii. Moist skin supplements gas exchange.
iii. Musculoskeletal system provides support and aids in locomotion.
iv. Limbs are supported by strong bones.
2. They are limited by their need to breed in water.
3. There are 6,000 species.
4. Gallery
a. Frogs—have powerful legs for hopping
b. Toads—frogs that live entirely on land as adults
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c. Caecilians—resemble worms or snakes
d. Salamanders—Some are aquatic, while others walk on land.
C. Reptiles
1. Key evolutionary adaptations to complete their entire life cycle on land are the
following:
a. Amniotes—They have an amniotic egg.
i. The amniotic egg provides a life support system for the embryo.
ii. The fluid-filled sac is called amnion.
2. One hypothesis places reptiles into four groups.
a. Turtles
i. Shells made of two hard shells fused to vertebrae
ii. Example: Green sea turtle
b. Crocodilians
i. Alligators and crocodiles
ii. Use upturned nostrils to breathe air while submerged
iii. Example: American alligator
c. Dinosaurs and birds
i. Birds branched off from dinosaurs about 160 million years ago.
ii. All birds (except for a few species) display adaptations for flight.
iii. These include small internal organs, lack of teeth, wings, keen senses and
complex behavior.
iv. Examples: Archaeopteryx (ancient bird) and red-tailed minla
d. Lizards and snakes
i. About 8,000 species
ii. Snakes are legless but retain small pelvic bones, evidence of their relationship to
lizards.
iii. Examples: Komodo dragon and grass snake
10.10. Mammals have hair and produce milk.
• CORE IDEA: All mammals have hair and produce milk in mammary glands. Modern
mammals can be divided into three major groups: monotremes (which lay eggs),
marsupials (which mature in pouches), and eutherians (which mature while connected to
placentas).
A. History
1. The first mammals evolved 180 million years ago.
2. During the age of dinosaurs, mammals were small and nocturnal.
3. After dinosaurs died out, mammals rapidly diversified.
B. Mammal features
1. Mammary glands
a. Mammals produce milk to nourish newborns.
b. Mammals have extended parental care compared to most animals.
2. Hair
a. Mammals are endotherms; that is, a constant, warm internal temperature results
from their metabolism.
b. Hair provides insulation.
c. Other animals (except birds) are ectotherms and must absorb body heat from the
environment.
C. Monotremes
1. Egg-laying mammals
2. Examples
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a. Duckbilled platypus
i. They are found exclusively in eastern Australia and Tasmania.
ii. They lay eggs.
iii. Females secrete milk onto fur.
b. Echidna
i. They are found throughout Australia.
D. Marsupials
1. The embryo begins development attached to a primitive placenta.
2. The tiny, embryonic offspring completes development in the pouch, where it attaches
itself to a nipple.
3. Most marsupials are found in Australia.
a. Australia was isolated when split off from other land masses around 60 million
years ago.
b. The eastern gray kangaroo is found in Australia.
4. The North American opossum is found in the United States.
E. Eutherians
1. Placental mammals have offspring that spend considerable time attached to a placenta
in the mother’s uterus.
2. There are over 5,000 species.
3. Features
a. Placenta
i. It is more complex than that of marsupials.
ii. It provides for long physical association between mother and developing child.
b. Amniotic sac
i. Many mammals are born encased in an amniotic sac.
ii. The placenta is the “afterbirth.”
4. Gallery
a. Land mammals—most mammals
i. Dog
b. Bats—winged mammals
i. Gray long-eared bat
c. Cetaceans—aquatic mammals
i. Bottlenose dolphins
10.11. Humans evolved from ancestral primates several million years ago.
• CORE IDEA: Humans are primates that split off from other lineages 6–7 million years
ago. Several known hominin species displayed key human features before the appearance
of Homo sapiens, around 300,000 years ago.
A. Humans are
1. Eukaryotes
2. Animals
3. Chordates
4. Mammals
5. Primates
B. Primate evolution
1. The common ancestor to all primates lived around 65 million years ago.
2. Fossil evidence suggests that the human line split from other primates around 6–7
million years ago.
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C. Primates
1. Early primates lived in trees; bodies display features adapted for this habitat:
a. Eyes close together on front of face—3-D vision
b. Agile hands with fingernails and sensitive fingertips
c. Extended parental care
d. Excellent hand-eye coordination
e. Limber hip and shoulder joints
f. Brains large relative to body size
2. Humans belong to a group of primates called apes.
D. Important points about human evolution
1. Humans did not evolve from chimps.
a. We share a common ancestor 6–7 million years ago.
b. Humans and chimps have evolved separately for hundreds of thousands of
generations.
2. Human evolution did not proceed from one species to the next, each one evolving to
be more modern.
a. Human evolution is not an orderly procession.
b. Many species represent evolutionary dead ends: they died out.
c. Many species also coexisted at the same time and place.
3. Key human features did not evolve all at once.
a. Key human features such as upright posture, ability to speak, and large brains
evolved separately and at different times over millions of years.
E. Timeline of human evolution
1. There are approximately 20 different hominin species.
a. Hominins are the human branch of the tree of life.
2. The evolutionary relationship of these various species remains a topic of active debate.
3. Species
a. Australopithecus afarensis
i. 3.2-million-year-old female nicknamed Lucy
ii. Earliest example of bipedalism
b. Homo habilis
i. Earliest member of our own genus, Homo
ii. Known to have made tools
c. Homo erectus
i. First hominin to have migrated out of Africa about 1.8 million years ago
ii. Taller with larger brains
iii. Built huts and fires; made clothes; designed stone tools
d. Homo neanderthalensis
i. Also called Neanderthals
ii. Larger brains than our own
iii. DNA evidence suggests Neanderthals and H. sapiens interbred.
e. Homo sapiens
i. The oldest known fossils of our species are found in Ethiopia, dating to between
200,000 and 300,000 years ago.
ii. DNA evidence traces our ancestry back to Africa.
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Key Terms
10.1 Animals are multicellular consumers that evolved from colonial protists.
Bilateral symmetry
Phyla
Tissues
Heterotroph
Radial symmetry
10.2 Sponges and cnidarians have unusual body features.
Cnidarian
Medusa
Gastrovascular cavity
Polyp
Invertebrates
Radial symmetry
Sponge
10.3 Three phyla of worms have unique structures and belong to separate evolutionary
lineages.
Annelid
Gastrovascular cavity
Segmentation
Flatworm
Nematode
10.4 Mollusks are a very diverse phylum.
Bivalve
Gastropod
Cephalopod
Gills
Foot
Mantle
Mollusk
Radula
Visceral mass
10.5 The arthropods are extremely diverse and numerous.
Arachnid
Crustacean
Arthropod
Insect
10.6 Echinoderms are a sister phylum to the chordates.
Echinoderm
Endoskeleton
10.7 Vertebrates belong to the chordate phylum.
Chordate
Notochord
Endoskeleton
Pharyngeal slit
Nerve cord
Tail
10.8 The first vertebrates to evolve were fishes.
Bony fishes
Gills
Cartilaginous fishes
Lobe-finned fishes
Tube feet
Vertebrate
Operculum
Swim bladder
10.9 Amphibians and reptiles were the first tetrapods to occupy land.
Amniotic egg
Reptile
Amphibian
Tetrapod
10.10 Mammals have hair and produce milk.
Endotherm
Mammal
Eutherian
Mammary gland
Marsupial
Monotreme
10.11 Humans evolved from ancestral primates several million years ago.
Hominin
Primate
Word Roots
• A = without
• Amphi = two or both
• Auto = self or same
• Bi = twice or two
• Cephalo = head
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• Di = two, twice, or double
• Ecto = outer, outside, or external
• Endo = within
• Exo = outer, outside, or external
• Gastro = referring to belly or stomach
• Hetero = other or different
• Homo = human being
• Mamma = breast
• Platy = flat
• Pod = foot
• Troph = nourishment or food
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