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17.1: Overview of Animals

Difficulty Level: At Grade Created by: CK-12
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Lesson 17.1: True or False

Name___________________ Class______________ Date________

Write true if the statement is true or false if the statement is false.

_____ 1. Animals are multicellular prokaryotes.

_____ 2. Animal cells have cell walls to maintain their shape.

_____ 3. All animals are heterotrophs.

_____ 4. Vertebrates do not have a backbone.

_____ 5. All animal cells are exactly the same shape.

_____ 6. Animals have a nervous system.

_____ 7. Almost all animals digest their food inside their bodies.

_____ 8. Most animals reproduce by sexual reproduction.

_____ 9. Fish are in the phylum Chordata.

_____ 10. Roundworms are in the phylum Arthropoda.

_____ 11. Over 90% of all animals species are vertebrates.

_____ 12. A characteristic of animals is that they have sensory organs.

_____ 13. An exoskeleton is a bony skeleton on the outside of some organisms.

_____ 14. A notochord is a rigid, supportive rod spanning the length of the body of chordates.

_____ 15. The first animals to evolve with true lungs were the reptiles.

Lesson 17.1: Critical Reading

Name___________________ Class______________ Date________

Read these passages from the text and answer the questions that follow.

Evolution of Amniotes

Amphibians were the first animals to have true lungs and limbs for life on land. However, they still had to return to water to reproduce. That’s because their eggs lacked a waterproof covering and would dry out on land. The first fully terrestrial vertebrates were amniotes. Amniotes are animals that produce eggs with internal membranes. The membranes let gases but not water pass through. Therefore, in an amniotic egg, an embryo can breathe without drying out. Amniotic eggs were the first eggs that could be laid on land. The earliest amniotes evolved about 350 million years ago. They may have looked like the animal shown below. Within a few million years, two important amniote groups evolved: synapsids and sauropsids. Synapsids evolved into mammals. The sauropsids gave rise to reptiles, dinosaurs, and birds.

Early Amniote. The earliest amniotes probably looked something like this. They were reptile-like, but not actually reptiles. Reptiles evolved somewhat later. (Image courtesy of ArthurWeasley and under the Creative Commons license CC-BY-SA 3.0.)


1. Why was the evolution of amphibians notable? What did they pioneer?

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2. What characteristic of amphibians necessitates that they live near water?

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3. Define amniote.

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4. What reproductive advantage do amniotes have over pre-amniotes?

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5. What are the important animal groups that evolved from amniotes? What in turn, evolved from these groups?

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Lesson 17.1: Multiple Choice

Name___________________ Class______________ Date________

Circle the letter of the correct choice.

  1. Animal cells and bacterial cells both may have all of the following cell structures except
    1. mitochondria.
    2. DNA.
    3. plasma membrane.
    4. flagella.
  2. Which of the following are animals?
    1. snake
    2. sponge
    3. flatworm
    4. all of the above
  3. Which of the following is not a characteristic shared by almost all animals?
    1. digestion of food internally
    2. the ability to fly
    3. the ability to move, at least at some stage of their life
    4. detection of environmental stimuli
  4. Invertebrates evolved adaptations including
    1. a fluid-filled body cavity.
    2. a complete digestive system.
    3. a symmetrical body.
    4. all of the above.
  5. A skeleton forming outside the animal's body is a(n)
    1. endoskeleton.
    2. exoskeleton.
    3. notochord.
    4. vertebrate.
  6. One of the main challenges animals faced when moving to land was
    1. switching to asexual reproduction.
    2. getting rid of their nervous systems, which would be too sensitive on land.
    3. getting rid of extra water.
    4. not losing too much water from their bodies.
  7. An example of an animal that has a notochord but lacks a backbone is a
    1. tunicate.
    2. fish.
    3. bird.
    4. all of the above
  8. Animals that have eggs with internal membranes that permit diffusion of gases but prevent water loss are classified as
    1. chordates.
    2. echinoderms.
    3. amniotes.
    4. rotifers.

Lesson 17.1: Vocabulary I

Name___________________ Class______________ Date________

Match the vocabulary word with the proper definition.


_____ 1. living on land

_____ 2. animals with a notochord

_____ 3. an animal with a backbone

_____ 4. a hollow nerve cord running the length of the body

_____ 5. a living organism whose eggs are surrounded by membranes

_____ 6. an animal with no backbone

_____ 7. another name for backbone

_____ 8. heterotrophic organisms that can detect environmental stimuli, can move on their own during at least part of their life, and most often digest their food internally

_____ 9. living in the ocean

_____ 10. the parts of an animal that detect environmental stimuli

_____ 11. a non-bony skeleton on the outside of arthropods

_____ 12. cell with a nucleus


a. amniote

b. animal

c. chordate

d. eukaryote

e. exoskeleton

f. invertebrate

g. marine

h. notochord

i. sensory organs

j. terrestrial

k. vertebral column

l. vertebrate

Lesson 17.1: Vocabulary II

Name___________________ Class______________ Date________

Fill in the blank with the appropriate term.

1. Another name for backbone is __________.

2. __________ are heterotrophs that have sensory organs, internal digestion, and the ability to move.

3. __________ organisms live in the ocean.

4. __________ organisms live on land.

5. A __________ is a hollow nerve cord running the length of the animal's body.

6. In animals, __________ detect environmental stimuli.

7. __________ animals have backbones.

8. __________ animals lack a backbone.

9. The eggs of __________ have internal membranes.

10. A __________ has its DNA contained within a nucleus.

11. A __________ has a notochord.

12. Arthropods, such as insects and crustaceans, have a(n) __________ to help protect and support them.

Lesson 17.1: Critical Writing

Name___________________ Class______________ Date________

Thoroughly answer the question below. Use appropriate academic vocabulary and clear and complete sentences.

Land animals evolved from animals that live in the water. What kinds of adaptations did animals evolve that allowed them to move from water to land?

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