Name ______________________________Class ______________ Date _________
Animal Body Plans and Evolution
Lesson Objectives
Discuss some trends in animal evolution.
Explain the differences among the animal phyla.
Lesson Summary
Features of Body Plans Each animal phylum has a unique organization of body
structures called its “body plan.” The features of a body plan include
levels of organization: cells, tissues, organs, organ systems
body symmetry
• radial symmetry: body parts extend from a central point
• bilateral symmetry: left and right sides are mirror images, with front and back ends
differentiation of germ layers:
• endoderm, the innermost layer
• mesoderm, the middle layer
• ectoderm, the outermost layer
formation of a cavity, or fluid-filled space between the digestive tract and the body wall
• a true coelom (found in most complex animal phyla) develops in the mesoderm and is lined
with tissue derived from the mesoderm
• a pseudocoelom is only partially lined with mesoderm
• Some invertebrates lack a body cavity and some have only a primitive, jellylike layer
between the ectoderm and endoderm.
patterns of embryological development
• Sexually reproducing animals begin life as a zygote, or fertilized egg.
• The zygote develops into a hollow ball of cells, the blastula.
• The blastula folds in on itself and creates a tube that becomes the digestive tract; the tube
has a single opening, the blastopore:
In protostomes (most invertebrates), the blastopore becomes the mouth.
In deuterostomes (chordates and echinoderms), the blastopore becomes the anus.
segmentation: repeated parts, such as the segments of worms
cephalization: the concentration of sense organs and nerves near the anterior (head) end
limb formation: external appendages such as legs, flippers, and wings
The Cladogram of Animals The features of body plans provide the evidence needed to
build a cladogram, or phylogenetic tree, of all animals. Animal phyla are usually defined by their
adult body plans and patterns of embryological development.
The characteristics of animals vary within each phylum.
Each phylum may be thought of as an “evolutionary experiment.” Phyla with successful body
plans have survived.
Name ______________________________Class ______________ Date _________
Features of Body Plans
1. Complete the table of main ideas and details about animal body plans. Use the boxes to list
and summarize the features of animal body plans.
Features of Body Plans
Main Idea: Feature of Body Plan Details: Important structures or patterns
of development
Levels of organization
None, radial, or bilateral
Germ layers
Body cavity
Patterns of embryological
development
Repeated parts, such as the segments of worms
Cephalization
Limb formation
2.
Sketch two common objects that show the difference between radial symmetry and bilateral
symmetry. Label your sketches and explain them.
Name ______________________________Class ______________ Date _________
3.
Label each of these organisms with the kind of symmetry it exhibits.
4.
Draw three sketches that show the difference between acoelomate, pseudocoelomate, and
coelomate animals. Label ectoderm, mesoderm, and endoderm in your sketches.
Name ______________________________Class ______________ Date _________
5. Label the diagram showing the difference between deuterostomes and protostomes. Label the
following structures: blastula, blastopore, ectoderm, endoderm, mesoderm, mouth,
protostome.
For Questions 6–14, complete each statement by writing the correct word or words.
6. Deuterostomes that show radial symmetry in their adult form are called ________________.
7. ___________________ are bilaterally symmetrical animals with three germ layers and no
coelom.
8. ___________________ are protostomes with a true coelom and cephalization without
segmentation.
9. Members of the ____________________ phylum have no body symmetry.
10. Animals in the _____________________ phylum have specialized cells and tissues,
but no organs.
11. Both __________________ and ________________ are segmented protostomes with
bilateral symmetry.
12. In addition to echinoderms, ___________________ are also deuterostomes.
13. An important way in which the body plan of mollusks differs from that of arthropods is that
mollusks lack _____________________.
14. Only members of the _______________________ phylum have a pseudocoelom.
Name ______________________________Class ______________ Date _________
The Cladogram of Animals
Use the cladogram to answer Questions 15–17.
15. On the lines provided, label the names of the animal phyla that correspond to the letters in
the diagram.
a. _________________
b. __________________
c. __________________
d. __________________
e. __________________
f. __________________
g. __________________
h. __________________
i. ___________________
16. What characteristics define the branch of the cladogram that leads to the mollusks?
________________________________________________________________________
________________________________________________________________________
17. Is a chordate a “better” animal than a sponge? Explain your answer.
________________________________________________________________________
________________________________________________________________________
18. Cows, hawks, and whales are all vertebrates. However, their forelimbs are noticeably
different. Explain how “evolutionary experiments” that yield variations on a body plan have
produced such diversity among vertebrates. Use forelimb structures as an example.
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
Name ______________________________Class ______________ Date _________
Animal Evolution and Diversity
Invertebrate Evolution and Diversity
Lesson Objectives
Explain what fossil evidence indicates about the timing of the evolution of the
first animals.
Interpret the cladogram of invertebrates.
Lesson Summary
Origins of the Invertebrates It is not known when the first multicellular animals
evolved from single-celled eukaryotes.
Animals probably evolved from ancestors they shared with choanoflagellates more than
565 million years ago.
Fossils from the Ediacara Hills of Australia date from roughly 565 to 544 million years ago.
Their body plans are different from those of anything alive today. Some seem to be related to
invertebrates such as jellyfishes and worms.
Fossils from the Cambrium Explosion (which began about 542 million years ago) show how
animals evolved complex body plans over a span of 10–15 million years. Many had body
symmetry, a front and back end, specialized cells, and appendages, structures such as legs or
antennae protruding from the body. Some had hard body parts that became fossilized.
By the end of the Cambrian Period, the basic body plans of the modern phyla were
established.
Today, invertebrates are the most abundant animals on Earth.
Cladogram of Invertebrates The cladogram of invertebrates presents current
hypotheses about evolutionary relationships among major groups of modern invertebrates.
The major invertebrate phyla are the sponges, cnidarians, arthropods, nematodes
(roundworms), flatworms, annelids, mollusks, and echinoderms.
• Sponges have pores in their bodies.
• Cnidarians are radially symmetrical animals with stinging tentacles.
• Arthropods have segmented bodies, a hard external skeleton, jointed appendages, and
cephalization.
• Nematodes, or roundworms, are nonsegmented worms with pseudocoeloms. Their digestive
tracts have two openings.
• Platyhelminthes, or flatworms, are the simplest animals to have three germ layers, bilateral
symmetry, and cephalization.
• Annelids are worms with segmented bodies and a true coelom.
Name ______________________________Class ______________ Date _________
Larvae are the immature stages of development in some animals, such as mollusks. Many
mollusks have a free-swimming larval stage called a trochophore. The trochophore is also
characteristic of many annelids, indicating that annelids and mollusks are closely related.
• Mollusks are soft-bodied animals that usually have a shell. They also have a true coelom
and complex organ systems.
• Echinoderms have spiny skin and exhibit radial symmetry.
Origins of the Invertebrates
1.
How much time passed between the appearance of the first prokaryotic cells and the
emergence of multicellular organisms?
________________________________________________________________________
2.
What are choanoflagellates? What is their significance in animal evolution?
________________________________________________________________________
________________________________________________________________________
3.
How old is our oldest evidence of multicellular life?
________________________________________________________________________
For Questions 4–9, write the letter of the correct answer on the line at the left.
________ 4. The first animals were tiny and soft-bodied, so
A.
B.
C.
D.
no fossilized bodies exist.
few fossilized bodies exist.
fossilized bodies are plentiful.
the only fossils that exist are “trace fossils.”
________ 5. Fossil evidence indicates that the first animals began evolving
A. during the Cambrian Period.
B. before the Cambrian Explosion.
C. after the Cambrian Explosion.
D. after the Cambrian Period.
________ 6. Why are the fossils of the Ediacara Hills of Australia important?
A.
B.
C.
D.
Their body plans are different from those of anything alive today.
Some had cells, tissues, and specialized organs.
Some were differentiated into a front and back end.
Some were autotrophic.
________ 7. Over a period of 10–15 million years in the Cambrian Period, animals evolved
A.
B.
C.
D.
into eukaryotic, photosynthetic forms.
the ability to survive on the bottom of shallow seas.
complex body plans, including cells, tissues, and organs.
into modern, vertebrate forms.
Name ______________________________Class ______________ Date _________
________ 8. Structures such as legs or antennae that protrude from the body are
A.
B.
C.
D.
trace fossils.
appendages.
shells, skeletons, and other hard body parts.
evidence of an extinct phylum.
________ 9. Which animals are the most abundant on Earth?
A. arthropods
B. mollusks
C. sponges
D. invertebrates
Cladogram of Invertebrates
10. Write “yes” or “no” to indicate how certain features distinguish each phylum of
invertebrates. The first row is completed as an example.
Tissues
Sponges
no
Radial
Bilateral
Protostome
Deuterostome
symmetry
symmetry
development
development
no
no
no
no
Cnidarians
Arthropods
Nematodes
(Roundworms)
Flatworms
Annelids
Mollusks
Echinoderms
11. Describe three evolutionary trends you see in invertebrates.
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
Name ______________________________Class ______________ Date _________
Chordate Evolution and Diversity
Describe the most ancient chordates.
Interpret the cladogram of chordates.
Lesson Summary
Origins of the Chordates Embryological studies suggest that the most ancient
chordates were related to the ancestors of echinoderms.
Fossils of the earliest chordates (Cambrian Period) show muscles arranged in a series; traces
of fins; sets of feathery gills; a head with paired sense organs; and a skull and skeletal
structures likely made of cartilage, a strong connective tissue that is softer and more flexible
than bone. Cartilage supports all or part of a vertebrate’s body.
Modern chordates are very diverse, consisting of six groups: the nonvertebrate chordates and
the five groups of vertebrates—fishes, amphibians, reptiles, birds, and mammals.
Cladogram of Chordates The cladogram of chordates presents current hypotheses
about relationships among chordate groups. Major groups are:
Nonvertebrate chordates: The tunicates and the lancelets lack backbones.
Jawless fishes: Lampreys and hagfishes lack vertebrae and have notochords as adults.
Sharks and their relatives: They have jaws and skeletons made of cartilage.
Bony fishes: These animals have skeletons made of true bone. Most modern bony fishes are
ray-finned fishes. One group of ancient lobe-finned fishes evolved into the ancestors of
tetrapods, which are four-limbed vertebrates.
Amphibians: Amphibians live in water as larvae but on land as adults. They breathe with
lungs as adults, but most require water for reproduction.
Reptiles: Reptiles have dry, scaly skin, well-developed lungs, strong limbs, and shelled eggs
that do not develop in water.
Birds: Birds can regulate their internal body temperature. They have an outer covering of
feathers, strong yet lightweight bones, two legs covered with scales that are used for walking
or perching, and front limbs modified into wings.
Dinosaurs and birds are now considered to be in one clade, which is part of the larger reptiles
clade. Modern birds are, therefore, reptiles. The traditional class Reptilia, which is not a clade,
includes living reptiles and dinosaurs but not birds.
Mammals: Mammals produce milk from mammary glands, have hair, breathe air, have fourchambered hearts, and regulate their internal body temperature.
Origins of the Chordates
For Questions 1–8, write True if the statement is true. If the statement is false, change the
underlined word to make the statement true.
__________
1.
__________
2.
Embryological evidence suggests that the most ancient chordates were
related to the ancestors of echinoderms.
Pikaia was an early vertebrate fossil.
Name ______________________________Class ______________ Date _________
__________
3.
__________
__________
__________
__________
__________
4.
5.
6.
7.
8.
The earliest known invertebrate fossil was Myllokunmingia, which had
muscles arranged in a series, traces of fins, sets of feathery gills, a head
with paired sense organs, and a skull and skeletal structures.
The earliest vertebrate fossils had skeletons made of bone.
Cartilage is a strong connective tissue that is more flexible than bone.
Most modern chordates are vertebrates.
Modern chordates include five groups of vertebrates.
The most numerous group of vertebrates today is the mammals.
Cladogram of Chordates
9. Write “yes” or “no” to indicate how certain features distinguish each subphylum of chordates.
The first row is completed as an example.
Vertebrae
Jaws and
Paired
Appendages
True
Bone
Lungs
Four
Limbs
Amniotic
Egg
Endothermy
Nonvertebrate
chordates
Jawless
fishes
Sharks and
their relatives
Bony fishes
Amphibians
Reptiles
Birds
Mammals
10. Sharks and their relatives were the earliest group of animals with jaws to evolve. Why are
jaws a significant evolutionary development?
________________________________________________________________________
________________________________________________________________________
11. What three adaptations were needed for chordates to move from living in water to living on
land?
________________________________________________________________________
________________________________________________________________________
Name ______________________________Class ______________ Date _________
12. One group of feathered dinosaurs led to modern birds. What advantage might feathers have
given these dinosaurs?
________________________________________________________________________
13. How do mammals differ from all other chordates on the cladogram?
________________________________________________________________________
14. Which chordate groups can regulate their body temperatures internally?
________________________________________________________________________
15. Much evidence supports the hypothesis that modern birds share a common ancestor with
dinosaurs. Make a sketch to show the probable evolutionary relationships among modern
birds, modern reptiles, and extinct dinosaurs. Circle the clades shown in your diagram.
16. The order in which the major groups of chordates evolved makes sense. For example, a bony
skeleton had to evolve before a vertebral column. A vertebral column had to develop before
four limbs. Explain why certain traits had to evolve before the traits now seen in birds.
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
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Name ______________________________Class ______________ Date _________
Primate Evolution
Identify the characteristics that all primates share.
Describe the major evolutionary groups of primates.
Describe the adaptations that enabled later hominine species to walk upright.
Describe the current scientific thinking about the genus Homo.
Lesson Summary
What Is a Primate? In general, a primate is a mammal that has relatively long fingers and
toes with nails instead of claws, arms that can rotate around shoulder joints, a strong clavicle, and
a well-developed cerebrum.
Many primates have eyes that face forward, giving them binocular vision, which is the ability
to combine visual images from both eyes to provide three-dimensional views.
The well-developed cerebrum enables complex behaviors.
Evolution of Primates Humans and other primates evolved from a common ancestor that
lived more than 65 million years ago. Early in their history, primates split into two groups:
Primates in one group look very little like typical monkeys. This group contains the lemurs
and lorises.
Primates in the other group include tarsiers and anthropoids, or humanlike primates. Monkeys,
great apes, and humans are anthropoids. Anthropoids split into two groups about 45 million
years ago.
• The New World monkeys have prehensile tails, which can coil tightly around a branch to
serve as a “fifth hand.”
• Old World monkeys do not have prehensile tails. Great apes, also called hominoids, include
gibbons, orangutans, gorillas, chimpanzees, and humans.
Hominine Evolution The hominoids in the lineage that led to humans are called
hominines. The skull, neck, spinal column, hip bones, and leg bones of early hominine species
changed shape in ways that enabled later species to walk upright.
The evolution of bipedal, or two-footed, locomotion freed both hands to use tools.
The hominine hand evolved an opposable thumb that could touch the tips of the fingers,
enabling the grasping of objects and the use of tools.
Hominines also evolved much larger brains.
The oldest hominine fossil may be Sahelanthropus, roughly seven million years old.
Fossils of one early group of hominines, Australopithecus, showed they were bipedal apes that
probably spent some time in trees.
Paranthropus probably had a diet like that of modern gorillas. This species lived two to three
million years ago.
The Road to Modern Humans Many species of the genus Homo existed before Homo
sapiens appeared. At least three other Homo species existed at the same time as early humans.
Homo neanderthalensis survived in Europe until 28,000–24,000 years ago. H. sapiens
coexisted with the Neanderthals for several thousand years.
Name ______________________________Class ______________ Date _________
What Is a Primate?
For Questions 1–4, complete each statement by writing the correct word or words.
1. Primates have ______________ on their fingers and toes.
2. Primates are good climbers because they have a strong shoulder joint attached to
a strong ______________.
3. The ability to combine vision from both eyes is ______________ vision.
4. The “thinking” part of the brain is the ______________.
Evolution of Primates
For Questions 5–11, write the letter of the correct answer on the line at the left.
________ 5. How long ago did the common ancestor of all primates live?
________
________
A. 65 million years ago
C. 45 million years ago
B.
D. 28,000 years ago
56 million years ago
6. Which of these is NOT an anthropoid?
A. gibbon
C. human
B.
D. tarsier
orangutan
7. What factor contributed to the split of two groups of anthropoids about 45 million
years ago?
A. One group developed a prehensile tail.
B.
The continents where they lived moved apart.
C. They diverged from the lemurs and tarsiers.
________
________
D. The climate became colder.
8. Which characteristic distinguishes the New World monkeys from the Old World
monkeys?
A. prehensile tail
C. binocular vision
B.
D. mammary glands
9. Which of these is a hominoid?
A. loris
B.
________
opposable thumb
lemur
D. gibbon
10. Which primate is the closest relative of humans?
A. gorilla
________
C. tarsier
C. orangutan
B. gibbon
D. chimpanzee
11. How did scientists confirm which primate was the closest primate relative to
humans?
A. by comparing the skeletons
B.
by studying behavior
C. by using DNA analyses
D. by using geographic analyses
Name ______________________________Class ______________ Date _________
Hominine Evolution
12. Complete the Venn diagram to compare human and gorilla skeletons.
13. What do Lucy and the Dikika Baby have in common? Which one is more complete?
________________________________________________________________________
________________________________________________________________________
14. Why did scientists conclude that Paranthropus probably ate a diet that included coarse and
fibrous plant foods?
________________________________________________________________________
15. Why do we now think about human evolution as a shrub with multiple trunks rather than
a family tree?
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
Name ______________________________Class ______________ Date _________
The Road to Modern Humans
For Questions 16–21, write True if the statement is true. If the statement is false, change the
underlined word to make the statement true.
______________
16. One species of our genus, Homo, existed before our species,
Homo sapiens.
______________ 17. The earliest fossils that can definitely be assigned to the genus Homo are
from the species H. ergaster.
______________ 18. Researchers agree that the genus Homo originated in Asia and migrated
to other parts of the world.
______________ 19. One way to discover the migration patterns of human ancestors is to
compare the mitochondrial DNA of living humans.
______________ 20. Early Homo sapiens lived at the same time as another, closely related
species, Homo neanderthalensis.
______________ 21. The only surviving species of the once large and diverse hominine clade is
Homo erectus.
22. What evidence do scientists use to classify extinct species of the genus Homo? How do
scientists differentiate extinct species of Homo from each other and from the modern
species?
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
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