Unit 3 Lesson 2 How Do Plants Reproduce? Copyright © Houghton Mifflin Harcourt Publishing Company
Unit 3 Lesson 2 How Do Plants Reproduce?
How Does a Garden Grow?
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• The series of stages that a living thing goes through as it develops is called a life cycle. It is important to understand plant life cycles, because most of our food comes from plants.
• Most plants grow from seeds.
Unit 3 Lesson 2 How Do Plants Reproduce?
How Does a Garden Grow?
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• First, a seed is placed in soil, so it can sprout. Next, the plant grows until it reaches maturity. A mature plant may grow flowers or cones. Then, these structures make more seeds.
Unit 3 Lesson 2 How Do Plants Reproduce?
Radish Life Cycle
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• A radish goes through three stages during its life cycle.
• A radish seed contains an embryo of a plant. When a seed sprouts during a process called germination, an embryo begins to grow.
Unit 3 Lesson 2 How Do Plants Reproduce?
Radish Life Cycle
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•As a plant continues to grow, it gets larger.
•When a plant grows to its full size, it reaches maturity. Mature plants can make seeds that can grow into new plants.
Unit 3 Lesson 2 How Do Plants Reproduce?
Flowers and Cones
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• Flowers and cones are reproductive structures that make seeds. They produce sex cells.
• Sex cells are used during sexual reproduction.
• Male sex cells are called sperm, and female sex cells are called eggs.
Unit 3 Lesson 2 How Do Plants Reproduce?
Flowers and Cones
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• Fertilization is the process of a sperm and an egg cell joining together.
• A fertilized egg grows into a new plant inside a seed.
Unit 3 Lesson 2 How Do Plants Reproduce?
Flowers and Cones
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• In plants with cones, sperm are made in male cones, and eggs are made in female cones.
Unit 3 Lesson 2 How Do Plants Reproduce?
Flowers and Cones
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• Most cone-bearing plants are trees, such as pines, spruces, and cycads.
Unit 3 Lesson 2 How Do Plants Reproduce?
Flowers and Cones
Copyright © Houghton Mifflin Harcourt Publishing Company
Unit 3 Lesson 2 How Do Plants Reproduce?
Flowers and Cones
Copyright © Houghton Mifflin Harcourt Publishing Company
• Most plants produce seeds in flowers.
• Petals are the outer parts of a flower.
• The male organ is the stamen. It consists of a thin stalk topped by a saclike anther, which produces pollen. These grains of pollen contain the sperm.
• The female organ is the pistil. Its rounded base contains eggs.
• Many flowers have both anthers and a pistil.
Unit 3 Lesson 2 How Do Plants Reproduce?
Flowers and Cones
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Unit 3 Lesson 2 How Do Plants Reproduce?
The Power of Pollen
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• Plants reproduce through pollination.
• Pollination is the process of pollen moving from a male plant part to a female plant part.
• Plants can be pollinated by 1. Wind
2. Flowing water
3. Pollinators, such as bees, birds, and butterflies.
Unit 3 Lesson 2 How Do Plants Reproduce?
Seeds on the Move
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• Animals play a big role in moving plant seeds.
• Many animals eat fruit, which helps spread the seeds contained in the fruit.
• Other animals, such as squirrels, will find and bury seeds.
Unit 3 Lesson 2 How Do Plants Reproduce?
Seeds on the Move
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• Seeds, such as burs, can also travel on an animal’s body.
• Wind and flowing water also move seeds.
Unit 3 Lesson 2 How Do Plants Reproduce?
Seeds on the Move
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Unit 3 Lesson 2 How Do Plants Reproduce?
Seeds on the Move
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Unit 3 Lesson 2 How Do Plants Reproduce?
Seeds on the Move
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Unit 3 Lesson 2 How Do Plants Reproduce?
Other Ways Plants Grow
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• A spore is a cell that can form into a new plant when the conditions are right.
• Some plants, such as mosses and ferns, grow from spores instead of seeds.
Unit 3 Lesson 2 How Do Plants Reproduce?
Other Ways Plants Grow
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• Plants that grow from spores have two distinct forms in their life cycles. Spores are released when the structures that hold them break open. Wind carries the spore to a new spot. If the spot is good, the spore will grow into a plant.
Unit 3 Lesson 2 How Do Plants Reproduce?
Other Ways Plants Grow
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• A fern, or frond, is one form of the plant. Spore clusters will grow on the underside of the fronds.
• If a spore lands in a place with good light and water, it begins to grow into a tiny, flat, heart-shaped structure.
Unit 3 Lesson 2 How Do Plants Reproduce?
Other Ways Plants Grow
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• The heart-shaped structure is the other form of the plant. It produces eggs and sperm.
• If a sperm cell fertilizes an egg cell, a curled frond will begin to develop and push out of the ground.
• The new plant reaches maturity when it can reproduce.
Unit 3 Lesson 2 How Do Plants Reproduce?
Other Ways Plants Grow
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