Life Cycles. Plant Life Cycles. What Is a Life Cycle? Name Date

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1 TEKS 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? 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. 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. Plant Life Cycles 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. 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. 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. and Assessment TEKS Page 1 of 8

2 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. 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 and Assessment TEKS Page 2 of 8

3 A Closer Look: Conifers 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. A seed contains a tiny plant. When conditions are just right, it germinates. Animal Life Cycles 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. 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. Mature tree The seed grows and becomes a seedling. The seedling grows into a mature, or adult, tree. Male cone 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. 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. and Assessment TEKS Page 3 of 8

4 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. Adult butterfly Egg Larva 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 Adult ladybug Eggs Pupa 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. 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. and Assessment TEKS Page 4 of 8

5 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: Hands-On Activity Materials terrarium soil sponge animal eggs or young, such as mealworms, frog eggs, caterpillars, or grubs plant seeds notebook 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? and Assessment TEKS Page 5 of 8

6 Life Cycles For each organism, label the stages of its life cycle using the terms in the word bank. Word Bank seedling mature plant 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? How does the life cycle of a chicken differ from the life cycle of a frog? and Assessment TEKS Page 6 of 8

7 TEKS Assessment 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 Which of the following organisms undergoes direct development? frog fern eagle butterfly When a caterpillar becomes a pupa, what happens inside? 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. and Assessment TEKS Page 7 of 8

8 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 and Assessment TEKS Page 8 of 8