Plants and animals have predictable life cycles.. Students know the sequential stages of life cycles are different for different animals, such as butterflies, frogs, and mice... amph
Trang 1Genre Comprehension Skill Text Features Science Content
Nonfi ction State the Purpose • Captions
• Labels
• Glossary
Animal Life Cycles
Scott Foresman Science 2.4
Standards Preview
Standard Set 2 Life Sciences
2 Plants and animals have
predictable life cycles As a basis for
understanding this concept:
2.b. Students know the sequential
stages of life cycles are different for
different animals, such as butterflies,
frogs, and mice
ISBN 0-328-23503-2
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Life Sciences
by Nancy Day
Trang 2amphibian
insect
larva
life cycle
mammal
pupa
tadpole
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publisher deeply regrets any omission and pledges to correct errors called to its attention in subsequent editions.
Unless otherwise acknowledged, all photographs are the copyright of Dorling Kindersley, a division of Pearson.
ISBN: 0-328-23503-2
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by Nancy Day
Trang 3What is
a life cycle?
Living things grow
Living things change
This growth and change
is called a life cycle.
Every life cycle has steps or stages
Living things
have life cycles.
3
Animals look different at each stage
All animals change size
Many animals change shape
Some animals change color
Living things change size.
Trang 4Growing and Changing in
Different Ways
A mammal is an animal
Young mammals look like their parents
They change size as they grow
An insect is an animal
It has three body parts and six legs
It changes size, color, and shape
as it grows
Bears are mammals
5
An amphibian is an animal.
It lives in water for part of its life
Young amphibians do not look like their parents
They change size, shape, and color, too
This is a young toad
Toads are amphibians
An adult toad
Trang 5What is the life
cycle of a frog?
A frog is an amphibian
It begins life as an egg
Some frog eggs fl oat in the water
A tadpole hatches from the egg
It swims out
A tadpole is a very young frog.
A frog egg is tiny
A tadpole has a tail
7
The tadpole grows and changes
It grows back legs fi rst
Later come the front legs
The tadpole’s legs get stronger
Its tail gets smaller
This tadpole is nine weeks old
This frog is twelve weeks old
Trang 6From Young Frog to Adult Frog
The frog is no longer a tadpole
It is no longer a young frog
Now it is an adult
An egg
A young
tadpole
An older
tadpole
9
The adult frog may lay eggs in the water
Those eggs might become tadpoles
Then the life cycle starts over again
An adult frog
Trang 7What is the life
cycle of a mouse?
Mice are mammals
A baby mouse is called a mouse
It looks like its parents
But it is much smaller
It does not have hair
Newborn mice
11
The mouse grows
It looks more like its parents
At last, the mouse is an adult
It can have baby mice
Then the life cycle starts over
Two-week old mice
Adult mice
Trang 8What is the
life cycle of a
butterfl y?
A butterfl y is an insect
It starts life as an egg
Next, a caterpillar hatches
A caterpillar is a larva
A larva is a young insect.
egg
larva
13
A hard case grows around the caterpillar
It is now a pupa.
Out of the pupa comes an adult butterfl y
It looks nothing like a caterpillar!
Trang 9What is the
life cycle of a
grasshopper?
A grasshopper is an insect
It starts as an egg
The egg hatches
Out comes a young grasshopper
It is a nymph
nymph
15
eggs
The nymph has six legs
It does not have wings
The nymph grows into an adult
The adult grasshopper has two pairs
of wings
adult
Trang 10amphibian an animal that lives part of its
life in water and part on land
parts and six legs
and changes
or fur on its body
insects’ life cycles
life cycle
1 Go back to what you read about young
insects, mammals, and amphibians Which look like their parents? Which do not?
2 What are the four stages of the butterfl y’s
life cycle?
dog grow from a newborn kitten or puppy
to an adult? How did they look after they were born? When did they start to play?
Who or what did they play with? What did they eat?
pictures on pages 8 and 9 What is their purpose for being there?