Classifying Animals Lesson 3

Classifying Animals
Lesson 3
Let’s brainstorm different animals that we have seen.
With your partner, write down as many different
animals you can think of in one minute.
• Now that you’ve brainstormed different
animals let’s classify each one as a vertebrate
or invertebrate. Partners, write beside each
animal “V” for vertebrate or a “I” for
To which group of animals do you
• Vertebrates, mammals
• What are some things that we can do, but
animals can’t do?
• Examples: We can read, write, talk, and think.
Let’s read “Look and Wonder” on p.48.
• How do you determine whether an organism
is an animal?
• You can look at characteristics such as how it
gets food, how it reproduces, and whether it
Let’s read pages 50-51.
• What characteristic sets invertebrates apart
from vertebrates?
• The lack of a backbone.
• Where do most simple invertebrates live?
• In water or moist environments.
Look at the images on pgs. 50-51.
• What is unique about sponges and what kind
of symmetry do they have?
• Sponges are the only animals without real
tissues or organs. They are asymmetrical.
Let’s look closely at this word.
What is the base word in asymmetrical?
What does the word symmetry mean?
It means “the same on either side of a dividing line”.
The end of this word ical means “having symmetry”.
What is the prefix?
The prefix a means “not”.
So, asymmetrical means “not having symmetry”.
radial symmetry
• Radial means “rod or spoke of a wheel”.
• Radial symmetry means “wheel-like
bilateral symmetry
• Bilateral means “a side”.
• bi means “two”.
• Bilateral symmetry means “two-sided
Animal diversity
• Often, people think of animals as being large,
living on land, having four legs, and furry. This
is a misconception. There is a tremendous
diversity among animals- from very simple
sponges to mammals.
“Quick Check” questions p. 51
• What are some simple invertebrates?
• Sponges, cnidarians, and worms.
• What characteristics do scientists use to
classify cnidarians?
• All cnidarians have stinging cells. They also
have radial symmetry.
Let’s read pages 52-53.
• Complex invertebrates- the term complex
means “having many parts”. These
invertebrates have many recognizable body
parts and organs. They also can grow larger
than simple invertebrates.
What are three phyla of complex
• mollusks
• echinoderms
• arthropods
Muscular foot or tentacles
An example is a snail.
What type of symmetry do mollusks have?
Mollusks have bilateral symmetry.
• Many tube feet
• An example is a sea star.
• What type of symmetry do echinoderms
• Echinoderms usually have radial symmetry.
An example is a crab.
What type of symmetry do they have?
Bilateral symmetry
Look at the images on pgs. 52-53.
• How is the snail’s shell formed?
• The mantle secretes the shell.
• Why can you often see a sea star’s skeleton on
the outside?
• Spines from the skeleton often project
through their skin.
• Where is the crab’s skeleton?
• On the outside of its body.
“Read the Photo” p. 53
• What do arthropods have in common?
• Both arthropods have jointed legs and
segmented bodies.
“Quick Check” questions p. 53.
• What body parts do arthropods have that
echinoderms do not have?
• Head, eyes, legs
• The smaller the animal, the simpler the
animal. Is this statement generally true?
• No. Most insects, for example, are smaller
than mollusks but not simple at all.
Let’s read pgs. 54-55.
• What three characteristics do vertebrates
have in common?
• They have backbones, bilateral symmetry, and
a skeleton inside their bodies.
• Why do reptiles have to sun themselves?
• Reptiles sun themselves to stay warm because
they are cold-blooded and cannot
automatically keep their body temperature
What are the three classes of fish?
• Jawless fish
• cartilaginous fish
• bony fish
“Read a Photo” p. 55.
• How are birds and reptiles different?
• Birds have feathers. Reptiles have dry skin and
With a partner, answer the “Quick
Check” questions on p. 55 (3 min.)
• What are characteristics of vertebrates?
• Vertebrates have backbones, bilateral
symmetry, and skeletons inside their bodies.
• Why do many reptiles hide at night and stay
completely inactive?
• Since reptiles rely on environmental heat, they
cannot get warm enough at night to be active.
Let’s read p. 56.
• What characteristics make humans mammals?
• We have hair, large brains, and nourish our
young with milk.
• What does it mean to say that birds and
mammals are “warm-blooded”?
• They generate their own body heat.
“Quick Check” questions p. 56
• What characteristics are shared by all mammals?
• All mammals have hair, feed their young milk, have
large brains, and are warm-blooded.
• How do marsupials benefit from carrying their young
in a pouch?
• Marsupials protect their young by carrying them in a
Choose the BEST answer.
• Which animal exhibits radial symmetry?
A. Worm
B. Jellyfish
C. Sponge
D. Mollusk
Choose the BEST answer.
• How are annelid worms, such as earthworms,
different from other worms?
A. They have a digestive system
B. Their bodies are divided into segments.
C. Their bodies have bilateral symmetry.
D. They live inside the bodies of other animals.
Choose the BEST answer.
• Which structure allows bony fish to easily go
up or down in water?
A. Jaw
B. Gills
C. Cartilage
D. Swim bladder
Choose the BEST answer.
• Which animal is warm-blooded?
A. Eagle
B. Shark
C. Salmon
D. Bullfrog
A koala and a giraffe look very different, but they are both
animals. Give an example of how these organisms are alike and
an example of how they are different.
• Both have hair.
• They are different in that the koala has a
pouch to carry its young and the giraffe does
not have a pouch.