Download Life Cycles

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TEKS Review
3.10C
TEKS 3.10C investigate and compare how animals and plants undergo a series of orderly changes in
their diverse life cycles such as tomato plants, frogs, and lady bugs
Life Cycles
What Is a Life Cycle?
Plant Life Cycles
Every living thing has a life cycle, a
series of changes that occur during its life. An
organism’s life cycle begins when it is born,
hatches, or germinates. The organism grows
and finally reaches adulthood, or maturity.
Eventually, all individual organisms die.
However, the life cycle continues because
mature organisms are able to reproduce.
You can classify plants into two groups—
those that produce seeds and those that do not.
Most plants produce seeds. Seeds are
structures containing a tiny plant called an
embryo that has started to grow inside. The
hard outer covering of a seed protects the
embryo inside. The covering is called a seed
coat. Seeds also have stored food for the
embryo to use when the seed germinates, or
begins to grow.
The first stage in any life
cycle is the formation of a
new individual. For
example, when plants
form seeds, a new
individual is formed. The
seed begins to grow.
Mosses and ferns do not produce seeds.
They produce spores. Like a seed, a spore will
grow into a new plant. However, spores do not
have an embryo inside, and they do not
contain much stored food.
The individual grows and
develops, becoming an
adult. Adults are able to
reproduce, or make more
individuals like
themselves.
All individuals eventually
die. The life cycle will
continue, though, as long
as the adults reproduced
and their young survive.
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Adult fern
The fern life cycle
is very complex.
Spores develop on
the underside of an
adult fern’s leaves.
The spores grow
into a small plant,
and the small plant
eventually becomes
an adult fern.
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A Closer Look: Tomato Plants
A tomato plant starts its life as a seed.
Inside the seed, the embryo is dormant. It is
using very little energy, and it is not growing.
When the temperature and moisture are right,
the seed germinates. A small root and stem
start to grow. A small plant that has just
started to grow is called a seedling. The plant
continues to grow more roots, stems, and
leaves. This is called the vegetative stage.
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3.10C
The next stage is a called a mature plant. At
this time, the plant starts making flowers.
Flowers produce pollen. In order for seeds to
form, pollen must travel from one part of a
flower to another. In tomato plants, bees visit
the flowers. When they carry pollen from one
flower to another, they pollinate the plant. A
fruit, which you know as a red tomato, starts
to grow from part of the pollinated flower.
When you look at a slice of tomato, what do
you see? Seeds! They developed inside the
fruit. And so the cycle starts again.
Tomato Life Cycle
seedling
seeds inside fruit
growing plant
mature fruit
flower being pollinated
flowers developing into fruit
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TEKS Review
3.10C
A Closer Look: Conifers
Animal Life Cycles
Some plants produce seeds without using
flowers. These plants have cones instead.
Conifers are one type of cone-bearing plant.
They include pine trees, A tomato plant starts
its life as a seed. When the temperature and
moisture are right, a small root and stem start
to grow. The plant continues to grow and get
stronger and have more leaves. This is called
the vegetative stage.
There are many variations in animal life
cycles. Some young look very similar to the
adults they will become. Other young do not
look like the adults of their species. They
change drastically as they grow and develop.
A seed contains a tiny
plant. When conditions are
just right, it germinates.
When an animal goes through a change in
body form as part of its life cycle, it is called a
metamorphosis. During the metamorphosis,
new body parts form. This change occurs as a
young animal develops into an adult animal.
Often, the young eat a different food source
than the adults.
A Closer Look: Frogs
Frogs have an interesting life cycle. They
start their lives in eggs. In the egg, a tadpole
develops. When it hatches, it has a mouth,
gills, and a tail. It sticks to the underside of a
plant until it has grown more of a body and
then begins to swim like a fish.
The seed grows and
becomes a seedling. The
seedling grows into a
mature, or adult, tree.
Mature tree
Male cone
After about six weeks, a metamorphosis
begins. Tiny legs start to grow. Three weeks
later, it gets tiny arms. Then it looks like a
frog with a long tail. By the twelfth week, the
tail is absorbed into the body, and the tadpole
has turned into a small frog. Adult frogs have
lungs and must breathe air. They can live on
land, but their skin must stay moist.
Female cone
Male cones produce pollen. Wind carries the
pollen to the female cones. Seeds develop in
the female cones, and the life cycle continues.
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A Closer Look:
Ladybugs and Butterflies
Ladybugs and butterflies are insects that
change during their life cycle. Ladybugs and
butterflies do not look like one another, but
they go through the same stages in their life
cycles. Look at the similarities between the
two life cycles below.
Egg
Adult
butterfly
Larva
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Eventually, a larva will stop growing and
attach itself to a leaf. It changes into a pupa.
Inside the pupa, a metamorphosis occurs. The
organism grows wings and other new body
parts. Its shape changes and it becomes an
adult.
Adult butterflies sip nectar from flowers.
They no longer have mouthparts for chewing
leaves. Their mouth is now like a straw. Adult
ladybugs have a hard shell. Their wings are
underneath the shell. When adults reproduce,
the female lays eggs and the life cycle begins
again.
A Closer Look: Chickens
Pupa
Eggs
Adult
ladybug
Many animals, including birds, mammals,
fish, and reptiles, do not undergo a
metamorphosis during their life cycle. In these
animals, young are born live or hatch from an
egg. The young have the same body form as
the adults. The young grow and develop
continuously and slowly become adults. When
animals mature in this way, it is called direct
development.
Larva
Pupa
Both life cycles begin with an egg. When
the egg hatches, a worm-like larva crawls out.
Larvae eat a lot of food. Butterfly larvae,
called caterpillars, eat leaves. Ladybug larvae
eat tiny insects such as mites and aphids. As
the larvae grow, they shed their skin several
times.
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Chickens undergo direct development.
The life cycle begins when a hen—an adult
female—lays an egg. Inside the egg, an
embryo is developing. The chick hatches, and
it has all the body parts of an adult. Each day,
it grows and develops a little more.
Eventually, it matures and becomes an adult.
Adults can reproduce.
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Name ______________________________________ Date _________
Materials
Hands-On Activity
terrarium
soil
sponge
animal eggs or
young, such as
mealworms, frog
eggs, caterpillars,
or grubs
• plant seeds
• notebook
•
•
•
•
Life Cycles in a Terrarium
You can observe life cycles in a terrarium. A terrarium is an enclosed
area for raising and studying plants and animals. It is like an aquarium,
but it is not filled completely with water. A terrarium that houses a desert
environment will have very little water. A terrarium that houses a marsh
environment will have an equal mix of land and water.
Procedure:
1. Choose a plant and an animal whose life cycle you can easily study. First, find out what
type of animal eggs or larvae are available where you live.
2. Design a terrarium for the animal whose life cycle you will study. Research the animal’s
needs, and make sure the terrarium has everything your animal will need to survive. Add
some plant seeds that will grow well in the environment you make.
3. Each day, record your observations in a notebook. Watch the organisms in your terrarium
carefully for changes as they grow and develop. Make drawings to accompany the
information you record.
4. After several weeks, write a report of your observations. Present your report to the class.
Discussion Questions:
1. Which stages of a plant life cycle did you observe?
2. Which stages of a plant life cycle were you not able to observe?
3. Which stages of an animal life cycle did you observe?
4. Which stages of an animal life cycle were you not able to observe?
5. How did using a terrarium make it easier to collect, record, and analyze
information about life cycles?
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Name ______________________________________ Date _________
Life Cycles
For each organism, label the stages of its life cycle using the terms in the word bank.
seedling
mature plant
Word Bank
larva
tadpole
egg
adult
pupa
Tomato Plant
seed
___________________
___________________
Ladybug
___________________
___________________
___________________
adult
Frog
egg
___________________
___________________
Some plants have flowers. Why are flowers important in the life cycle of these plants?
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How does the life cycle of a chicken differ from the life cycle of a frog?
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Page 6 of 8
Name ______________________________________ Date _________
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3.10C
TEKS Assessment 3.10C
Fill in the letter of the best choice.
Which of the following is a young frog
that will turn into an adult?
A moth and a ladybug undergo the same
stages in their life cycles. Which of the
following stages comes after a moth’s
pupa stage?
Mario saved a seed from his apple and
planted it. What might he expect to see
come up out of the ground first?
a small green apple
a seedling apple tree
the roots of an apple tree
a mature apple tree
When a caterpillar becomes a pupa, what
happens inside?
Which of the following organisms
undergoes direct development?
It hibernates.
It grows different organs and
wings.
It rests and comes out just the
same.
It comes out the same shape, but
smaller since it couldn’t eat.
frog
fern
eagle
butterfly
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Answer Key
Hands-On Activity (p. 5)
1. Answers will vary based on the types of seeds planted. Students should be able to observe
seeds, seedlings, and young plants. Some types of plants, such as marigolds, flower
quickly, and allow an opportunity to observe flowers and the production of seeds by
mature plants.
2. Answers will vary but should be based on individual observations.
3. Answers will vary but should be based on individual observations.
4. Answers will vary but should be based on individual observations.
5. Sample answer: I was able to easily find the organisms in the terrarium. I did not have to
search outside for the organisms I wanted to observe.
Student Response Activity (p. 6)
1. Tomato plant—seedling, mature plant; Ladybug—egg, larva, pupa; Frog—tadpole, adult
2. Flowers are the reproductive structures of plants. After pollination occurs, flower are able
to produce seeds, which helps to ensure continuation of the species.
3. Chickens undergo direct development. Young chickens have all the body parts of an adult.
Frogs undergo a metamorphosis during their life cycle. The young (tadpoles) look very
different than the adults, and they grow new body parts when they become an adult.
TEKS Assessment (p. 7)
1. D
2. B
3. C
4. D
5. B
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