UNIT 3. PLANTS. 5 primary / Natural Science Pedro Antonio López Hernández Colegio La Presentación de Granada

Transcription

1 UNIT 3. PLANTS 5 primary / Natural Science Pedro Antonio López Hernández Colegio La Presentación de Granada

2 CHARACTERISTICS OF PLANTS A plant is a living thing with limited mobility. There are many different types of plants. All plants have one thing in common: they are living things that make their own food. PARTS OF A PLANT 3. LEAVES They capture sunlight and carbon dioxide from the air. Then, they use the sunlight, carbon dioxide, water and minerals to make nutrients. 1. ROOTS They enable plants to take in water and minerals from the soil. Some plants store nutrients in their roots. They need four substances to make their own food: water, minerals, sunlight and carbon dioxide. They use three main organs to make it: 2. STEMS They keep the plant upright and support it. The trunk of a tree is a very thick stem. It also carries water, minerals and nutrient to other parts of the plant through vessels. Flowering plants They have organs like flowers, fruits and seeds that help them to reproduce. Angiosperms Angiosperms, like apple trees, are plants that grow fruit with seeds. Gymnosperms Gymnosperms, like pine trees, are plants that have seeds but don t have fruit. CLASIFFICATION OF PLANTS Non-flowering plants They don t have seeds. They reproduce through spores. Spores are tiny cells that germinate and grow into a new plant. Ferns They have root, leaves and stem. Fern spores are formed on the underside of the leaves Mosses They don t have root, leaves and stem. Moss spores are produced in capsules.

3 PLANT NUTRITION Photosynthesis Respiration Plants make their own nutrients through photosynthesis. They absorb carbon dioxide and water with minerals and release oxygen into the air. This process take place in green leaves during the day. Leaves absorb energy from sunlight through a green pigment called chlorophyll and use it to produce glucose and oxygen. It is related to how plants get energy. Plants absorb oxygen from the air. Then, the oxygen ands nutrients are transformed into energy. Finally, the plant releases carbon dioxide and water vapour into the air. Respiration takes place during the day and night, because they need energy 24 hours a day. Water Carbon dioxide Sunlight Glucose Oxygen Sunlight Oxygen Carbon dioxide Carbon dioxide Oxygen Water and minerals Glucose

4 HOW DO PLANTS MAKE NUTRIENTS? Day Night 1. Plants absorb water and dissolved minerals through their roots. This mixture of water and minerals is called raw sap. PHOTOSYNTHESIS Produces nutrients. Releases oxygen. Elaborated sap: Nutrients 2. Xylem vessels are tubes that carry the raw sap from the roots to the leaves. 3. Leaves absorb carbon dioxide through pores called stomas. Raw sap: Water and minerals ENERGY 4. Photosynthesis takes place inside the leaves. Sunlight transforms raw sap and carbon dioxide into nutrients inside the leaves. 5. The nutrients formed inside the leaves are called elaborated sap. RESPIRATION They produce energy. Releases carbon dioxide. ENERGY RESPIRATION They produce energy. Releases carbon dioxide. 6. Phloem vessels are small tubes that transport elaborated sap all over the plant. Water and minerals

5 SEXUAL REPRODUCTION IN PLANTS 1. REPRODUCTION IN FLOWERING PLANTS It takes place inside the flower when two reproductive cells from two different plants come together. This generates a new plant that is similar to them. They have male and female reproductive organs Classification of flowers Male organs The stamen is the male reproductive organ: 1. The anther produces and holds pollen. They usually look like fine yellow dust. 2. The filament gives support to the anther. Corolla Calyx Female organs The pistil is the female reproductive organ: 1. The stigma has a sticky top to trap pollen. 2. The style is a tube tat connects the stigma and ovary. 3. The ovary is the central part of the pistil and contains the ovules. 4. Once an ovule is fertilised it becomes a seed. Male flower The male flower produces pollen. Female flower The female flower produces ovules. Hermaphrodite flower In many flowers, the male and female parts are inside the same flower.

6 THE POLLINATION OF FLOWERS Pollination occurs when pollen reaches the pistil and travels down it, where it fertilises the ovule. This is called fertilisation. Then, the ovary becomes a fruit and the ovule becomes a seed. When seeds fall to the ground and germinates, a new plant grows. Wind, insects and other agents can accidentally transport pollen from one flower to another. Self-pollination Cross-pollination Female flower Seed Fruit Male Flower Pollen New plant New plant Pollen is transferred from the stamen of a flower to the pistil of another flower of the same plant. Pollen is transferred from the stamen of a flower to the pistil of the flower of another plant of the same type.

7 2. REPRODUCTION IN NON- FLOWERING PLANTS They don t have flowers or seeds. They use spores to reproduce. Ferns reproduce this way. 1. Sori (singular, sours) are sacks that contain thousands of spores. They are located under the fern leaves. 2. Spores fall to the ground and form organs that produce reproductive cells. 3. After fertilisation, a new fern begins to grow.

8 ASEXUAL REPRODUCTION IN PLANTS Many plants that grow flowers and seeds can also reproduce through fragmentation. In fragmentation, a new plant grows from a fragment of the parent plant. 1. First, a small fragment breaks off the plant. 2. Then, the fragment falls to the ground and germinates. 3. Finally, a new plant begins to grow. This new plant is an identical replica of the parent plant. Types of fragments: Stolons are aboveground stems that grow horizontally. As they grow, they develop roots that produce a new plant. Strawberries are stolons. Cutting are stems that produce new roots when they are separated from the parent plant. Geraniums and grapevines grow from cutting. Tubers are underground stems. Tubers store many nutrients that they get from the soil. Potatoes are tubers. Bulbs are at the bottom of the stem. They grow underground. Bulbs store nutrients for the plant. When planted in the ground, each bulb gives rise to a new plant. Garlic and onions are bulbs. Rhizomes are underground stems that grow horizontally. New plants grow from these stems. Asparagus and iris plants are rhizomes.

9 HOW DO PLANTS RESPOND TO THEIR ENVIRONMENT? Plants can move Plants react to their environment by moving. There are two different ways plants move: Nastic movements 1. Phototropism is a tropic movement and occurs when plants grow towards sunlight. Tropic movements The movement of the plant does not involve growth. For example: A carnivorous plant suddenly closes it leaves when an insects touches it. 2. Hydrotropism is another tropic movement that occurs when the roots of plants sense water in the ground and always grow towards the source of water. They occur when plants move towards or away from a stimulus and involve growth. For example: Some plants grow toward sunlight. 3. Gravitropism occurs when plants react to gravity. This explains why roots always grow down into the soil.

10 HOW DO PLANTS RESPOND TO THEIR ENVIRONMENT? Plants respond to the seasons Plants also respond to environmental changes in light, temperature and humidity and this influences their life cycle. Observe how the Beech trees (deciduous) responds to weather changes in each season: