Plants: Increasing the Numbers PDF

# Plants: Increasing the Numbers ## AIMS - Identify some seed-producing plants. - Study the various stages in the germination of a seed. - Experimentally find out the conditions necessary for germination. - Learn about the two types of crops and the ways of seed dispersal. ## AIDS - An animated...

# Plants: Increasing the Numbers ## AIMS - Identify some seed-producing plants. - Study the various stages in the germination of a seed. - Experimentally find out the conditions necessary for germination. - Learn about the two types of crops and the ways of seed dispersal. ## AIDS - An animated film clip about germination. - Dry gram and bean seeds. - Sprouting gram, bean, wheat, etc. - Charts or slides showing parts of monocot and dicot seeds. - Specimens of seeds with special features that help them to be dispersed. ## Soma's day Soma comes home from school at 3 p.m. She has lunch which consists of roti and vegetables. Now it is 8 p.m. She is having dinner with her family. Talk to your partner and write the names of at least six food items which you see in the picture. ## Our Life depends on plants Our life depends on nature. Plants are a major part of nature. Plants give us food. - Cereals, pulses, vegetables and fruits come from plants. Sugar and oil too are obtained from plants. - Plants provide us with wood, fibre, rubber, gum, tea and coffee. - Plants supply us with life-giving oxygen. - Plants help to reduce soil erosion. Life on earth cannot exist without plants. We need to grow more and more plants since we depend on them. More plants would mean a continuous supply of plant products to meet our needs. **Fig. 1.1 Our life depends on plants** ## New Plants from Seeds Why does a plant produce so many seeds? They do so, because most new plants grow from seeds. Yet all seeds do not grow into new plants. ### Seed Germination The development of a seed into a seedling is called germination. Let us do an activity to find out the conditions necessary for the germination of a seed. Seeds of some plants like wheat, maize and rice have one seed leaf and are called monocot seeds. **Fig. 1.3 A maize seed has one seed leaf.** ### A seed and its parts **Activity 1** Soak some gram seeds in water for a few days. Take one of these seeds. You will notice that it has an outer covering which has swelled because the seed was in water. This outer covering is the seed coat. **Fig. 1.2 A gram seed has two seed leaves.** Remove the seed coat. You will see two seed leaves or cotyledons. Separate them and you will find a baby plant inside. This baby plant has a tiny shoot and a tiny root. Food for the baby plant is stored in the seed leaves. As long as the baby plant does not grow green leaves, it depends on the food stored in the seed. Seeds of some plants like grams, peas and beans have two seed leaves and are called dicot seeds. ### Conditions necessary for the germination of a seed **Activity 2** Take four plates and number them 1, 2, 3, and 4. Take some dry gram seeds. Put some seeds in Plate 1 and keep the plate on a windowsill where it can get air and sunlight. Put some seeds in Plate 2. Keep the plate in a beaker containing water. Now keep the beaker on the windowsill. Put some seeds soaked on moist cotton in Plate 3. Keep the plate inside a refrigerator. Put some seeds soaked on moist cotton in Plate 4. Keep the plate on the windowsill. Keep the cotton of Plate 4 moist all the time. **Fig. 1.4 The conditions necessary for the germination of a seed** **Now fill in the table.** | Plate | Conditions the seeds got | Conditions the seeds didn't get | Did the seeds germinate? | |---|---|---|---| | 1 | Air, warmth (sunlight) | Water | No | | 2 | Water, warmth | Air | No | | 3 | Air, water | Warmth | No | | 4 | Air, water, warmth | | Yes | You will notice that only the seeds in plate 4 have germinated. This shows that air, moisture (water) and warmth (sunlight) are the conditions necessary for germination. This is because a germinating seed needs air to breathe. Water also makes the seed coat soft. This helps the baby plant to break the seed open and come out. Warmth is needed for the cells of the seed to become active. ### Stages in Germination **Activity 3** Soak some gram seeds in water. You will notice that a soaked seed is swollen because it has absorbed water Its coat has also become soft. Now put these soaked seeds on a piece of wet cloth tied over the mouth of a jar (Fig. 1.5). **Fig. 1.5 Stages in germination** Tiny roots will come out of the soft, moist seed coats. Later, shoots too will come out. The root grows downward, towards gravity and the shoot grows upward, towards sunlight. This seedling grows and becomes a plant. ## Dispersal of Seeds Plants are fixed to the ground and cannot move from one place to another. If all baby plants grow near the parent plant, not all would survive. They would not get enough sunlight, food, water and space to grow. Hence, there are some agents in nature to scatter these seeds. These agents carry the seeds or fruits away from their parent pant. This process is called dispersal. ### Agents of Dispersal Dispersal is carried out by the wind, water, animals and by the explosion of fruits. The special structures of certain seeds and fruits help these seeds in dispersal. - **WIND**: seeds of cotton, madar and hiptage - **WATER**: The lotus fruit has a spongy part and the coconut has a fibrous outer covering to enable them to float on water. - **ANIMALS**: Human beings and animals eat fruits like cherries and mangoes and throw away their seeds. Some seeds have hooks or spines. They get stuck to the hairy skin of animals and are carried away. Birds swallow some seeds, which come out unchanged in their droppings. - **EXPANSION**: Some fruits like peas in a pod, burst open or explode when dry. The force of explosion helps to scatter the seeds. **Fig. 1.6 Seeds dispersed by wind** **Fig. 1.7 Seeds dispersed by water** **Fig. 1.8 Seeds dispersed by animals** **Fig. 1.9 Seeds dispersed by explosion** ## New Plants from Other Parts of Plants Besides growing from seeds, new plants also grow from certain other parts, such as roots, stem and leaves of the parent plant. - Some plants like the roses, sugarcane and hibiscus grow from stem cuttings. - The potato is a stem that grows underground and has buds called 'eyes'. Any part of a potato that has buds on it can grow into a new plant. Onion and ginger are also underground stems from which new plants grow. - Sweet potatoes and carrots are examples of plants whose roots plant grow into new plants. - The leaves of plants like the bryophillum can grow into new plants. **Fig. 1.10 Any part of a potato which has an ‘eye' can grow into a new plant.** **Fig. 1.11 A new plant can grow from the root of a sweet potato.** **Fig. 1.12 A stem cutting of a rose can grow into a new plant.** **Fig. 1.13 New plants can grow from the leaves of the bryophyllum.** ## Crops and Vegetables Plants of one kind grown in a particular area or region during a particular period are called crops. Farmers grow different crops in different seasons. Crops like wheat and gram grown from November to April, are called rabi crops or winter crops. Crops grown from June to October are called kharif crops or monsoon crops. Rice, maize, jowar and bajra are kharif crops. - Vegetables like the cabbage, cauliflower, radish, bean and pea grow during winter. - Vegetables like the brinjal, pumpkin and gourd grow in summer. Different plants not only grow in different climates and seasons but also require different kinds of soil. If we know the conditions that are suitable for the germination of seeds, we can grow better crops. - Rice and jute grow in clayey soil which holds plenty of water. That is why more rice is grown in and around West Bengal. - On the other hand, wheat is grown in the sandy and irrigated soil of Punjab and Uttar Pradesh. - Jowar and bajra are grown in sandy soil like that of Rajasthan. - Cotton grows well in the black soil of central and western India. - Tea plants need moist soil and grow on the slopes of hilly areas like Assam, the Nilgiris and Darjeeling. - Coconut trees grow in coastal areas like Kerala and Goa. - Maize grows well in the dry soil of the plains or hills. - Onion and groundnut need well-drained, sandy soil. ## Agriculture Plants need to be grown on a large scale to feed the entire population of a country. The practice of growing plants on a large scale is called agriculture. - Manure is added to soil to increase production. - Fertilizers like urea, super phosphate, ammonium sulphate and nitrate are added to the soil. However, overdose of chemical fertilizers can be harmful for the soil as well as the crops. For a good and healthy crop, we must: - Use healthy and ripe seeds for sowing. - Prepare the soil properly. - Add manure or fertilizers to the soil. - Irrigate the soil. - Use insecticides and pesticides. These are chemicals that are sprayed on standing crops. If sprayed properly, they protect the crops from being destroyed by pests. However, too much of pesticides and insecticides can be harmful to our health. **Fig. 1.14 Maize, a kharif crop, is grown in the summer.** **Fig. 1.15 Wheat, a rabi crop, is grown in the winter.** ## Protection of Crops and Storage of Seeds We need to protect our crops against: - Grazing animals like cows and goats. - Pests such as locusts, grasshoppers and caterpillars. - Diseases. Bigger animals can be kept away by proper fencing. After harvesting, grains need to be protected against moisture. They have to be kept safe from rats, moles, birds, squirrels and insects. So, they must be stored in airtight, sealed containers. Plants, like other living things, need love and care. Under favourable conditions they grow well. A good crop adds to the wealth of a country. ## Let us say it again - Plants are the most useful gifts of nature for humans and animals. - A plant produces many seeds, but only a few are able to grow into new plants. - A seed has a seed coat, seed leaves and a baby plant inside it. - Air, water and warmth are necessary for germination of seeds. - The development of a seed into a seedling is called germination. - Seeds have to get scattered or dispersed, so that they get favourable conditions to grow. - Seeds are dispersed by wind, water, animals and by the explosion of fruits. - A new plant can also grow from stem cuttings, underground parts of plants and leaves. - India has two main types of crops: rabi (winter) and kharif (summer). - We can protect crops and seeds in different ways. ## Let us answer ### A. Tick (✔) the correct answer. 1. A seed with two seed leaves is called a - damaged seed. - monocot. - soaked seed. - dicot seed. 2. Right soil, warmth, enough air and water are necessary conditions for the growth of - children. - birds. - seeds. - books. 3. New plants can grow from the leaves of - ginger. - bryophillum. - onion. - sweet potato. 4. Which feature helps a coconut fruit to float in water? - a fibrous outer covering - a spongy part - presence of hook - presence of spine 5. Plants that need clayey soil to grow well are - wheat and gram - rice and jute - jowar and bajra. - tea and coffee. 6. Insecticides and pesticides protect crops from being destroyed by - drought. - excessive rain. - pests. - elephants. ### B. Fill in the blanks. 1. Maize has ______ seed leaf/leaves. 2. Any part of a potato that has _______ on it can grow into a new plant. 3. In India, crops like wheat and gram are grown from November to April, and are called _______ crops. 4. Onion and _______ need well-drained, sandy soil. 5. Plants help to reduce soil _______. ### C. Complete the series 1. mango: seed :: ______: root 2. hiptage: wind :: ______: explosion 3. cabbage: winter :: ______: summer 4. rice: clayey soil :: ______: black soil 5. maize: dry soil :: ______: sandy soil ### D. If you were a gardener, which part of a plant would you plant to grow a new 1. rice plant? ______ 2. rose plant? ______ 3. ginger plant? ______ 4. onion plant? ______ 5. sweet potato plant? ______ 6. bryophyllum plant? ______ ### E. Write short answers. 1. Name the outer covering of a seed. ______ 2. What is a monocot seed? ______ 3. What is germination? ______ 4. What is meant by dispersal of seeds? ______ 5. What are kharif crops? ______ 6. Why do we spray pesticides on crops? ______ ### F. Answer these questions. 1. How are plants useful to us? ______ 2. Name the different parts of a seed. Draw a diagram and label the parts. ______ 3. Name the conditions necessary for germination. ______ 4. Why must seeds be dispersed? What are the different agents of dispersal? ______ 5. What is agriculture? ______ ### G. Think and answer. 1. A papaya has many seeds. Each papaya seed can grow into a new tree. However, that does not happen. Why? ______ 2. Why can't all seeds be dispersed by the wind? ______ 3. Why can't we grow tea in Rajasthan? ______ # Rocks and Minerals ## AIMS - Identify the different kinds of rocks. - Understand the use of natural resources and its conservation. ## AIDS - National Geographic films on different regions of the earth. - Different kinds of rocks. - Pictures of oil wells and coal mines. ## What are rocks made of? Rocks are made of minerals. A mineral is a natural non-living substance. A rock may contain one or more minerals. The type of a rock depends on the quality, the quantity and the arrangement of minerals in it. According to their formation, rocks are divided into three groups - igneous, sedimentary and metamorphic. ## Kinds of Rocks ### Igneous Rocks Igneous rocks form the base of all forms of land - plains, mountains and ocean beds. They are formed by the cooling and hardening of hot liquid rock material. The hot liquid rock that lies in huge underground pockets of the earth is called magma. The hot material is pushed upward by the pressure of other rocks. Some of it cools and hardens below the surface of the earth while some flows out on the earth's surface and then hardens to form igneous rocks. The magma that reaches the surface of the earth is called lava. The type of igneous rock formed depends on the kind of mineral the magma contains and the size of the mineral particles. **Fig. 7.1 Lava coming out of a volcano** **Fig. 7.2 Igneous rocks form the base of all forms of land.** #### Granite Granite is the most common igneous rock on the earth’s surface. The three main minerals in granite are quartz, feldspar and mica. The colour of granite, grey or pink, depends upon the content of its feldspar. This hard stone is used for making buildings, statues and streets. #### Pumice Pumice is another light-coloured igneous rock. It has many holes and pockets which are formed by the gases trapped inside at the time of its formation. This light lava rock is light grey or cream-coloured. Dentists use powdered pumice for polishing our teeth. #### Obsidian Obsidian is another lava rock. It looks almost like black glass. Because of its sharp edges it is used to make cutting tools. **Fig. 7.3 Some Igneous rocks** ### Sedimentary Rocks A major portion of the earth's land surface is covered with sedimentary rocks. These are formed from pebbles, sand, mud or clay that are deposited in oceans. These sediments are brought to the shore by flowing water or floating ice and are piled up in layers. The layers are cemented together by minerals. There are many kinds of sedimentary rocks. Certain kinds of sedimentary rocks are formed from the shells of tiny sea creatures. Others are formed from dissolved minerals that settle by the side of oceans. **Fig. 7.4 Sedimentary rocks form a major portion of the earth’s surface.** #### Sandstone Sandstone is a common sedimentary rock. It is made from particles of sand that get cemented together. It mostly contains quartz grains. Sandstone may be yellow, brown, red or pink-coloured. #### Conglomerate Conglomerate is a rock of uneven texture. It is formed from pebbles and gravel cemented together by minerals and sand and carried by water. Conglomerate is found mostly in shades of grey and orange. It is used as an ornamental rock and for polishing ornaments. #### Shale Shale is made up of clay and mud particles that are piled up in layers. Because of its clay content it is used to make tiles and bricks. #### Limestone Limestone is made up of a mineral called calcite, which was once a part of animal shells. It is mostly grey or white. Chalk is one form of limestone. Limestone is used for making bricks and glass, and for separating pure metals from their ores. Scientists can find out about life on earth by studying sedimentary rocks, because the traces of ancient plant and animal life, called fossils, are found in them. These may be shells, bones of animals, prints of leaves or footprints. **Fig. 7.5 Some sedimentary rocks** **Fig. 7.6 A starfish fossil in sedimentary rock** The Red Fort in New Delhi is made of sandstone. ### Metamorphic Rocks Metamorphic rock is the result of the transformation of an existing rock, in a process called metamorphism, which means 'change in form'. Most metamorphic rocks were once either igneous or sedimentary. Tons and tons of pressure, which favours heat build-up, changed them to metamorphic rocks. In some rocks the minerals are broken into smaller ones, while in others the minerals are stretched into flat particles. There are many kinds of metamorphic rocks. #### Slate Slate is a metamorphic rock made from shale. It breaks into thin layers. It is used to make slates and blackboards. #### Gneiss Gneiss is a metamorphic rock that is formed from granite. It has light and dark bands. #### Marble Marble is a widely used metamorphic rock. It is found in different colours, white being the most common. Polished marble gleams so it is used to make statues and buildings. #### Quartzite Quartzite was once sandstone. Quartzite is too hard to be used as a building stone but it is used for making statues. **Fig. 7.7 Some metamorphic rocks** ## Minerals Minerals are underground natural resources. Some minerals found in rocks are metallic and some are non-metallic. - **Metallic minerals**: Some useful metals can be profitably obtained from metallic minerals called ores, such as haematite, bauxite, pyrite and calamine. We get iron, aluminium, copper and zinc respectively from these ores. These metals are commonly used for making utensils, machines, furniture, wires, coins and coaches of trains and aeroplanes. Precious metals like gold, silver and platinum are used for making jewellery. - **Non-metallic minerals**: Coal and petroleum are valuable underground resources. They contribute greatly to our total energy supply. ### Coal Coal is one of the most valuable minerals stored in the earth. It has been used as a fuel for hundreds of years. Asia has more than one-third of the world’s coal. Millions of years ago land was low-lying, and covered with thick swampy forests. As plants died, they fell into the swamp and began to decay. New vegetation pressed the dead plants to the bottom. Due to extreme pressure the vegetable matter changed into peat, lignite and coal. In India, coal mines situated in Sohagpur (Madhya Pradesh), Dhanbad (Jharkhand), Raniganj (West Bengal), Neyveli (Tamil Nadu) and Singareni (Telangana). Coal is used as a fuel - for cooking. - for heating homes and buildings. - for producing electricity in power plants. - in steam engines, and - in blast furnaces in the steel industry. **Fig. 7.8 Some petroleum products** ### Petroleum Petroleum or crude oil has several names like rock oil, fossil fuel, black gold and liquid sunlight. This fossil fuel is formed from the dead remains of ancient land and sea creatures. Millions of years ago the dead remains of these living things got buried in layers and gradually changed into oil and gas. In India, petroleum is obtained from many places. Some of these are Ankleshwar in Gujarat, Digboi in Assam and Bombay High on the Mumbai coast. The main use of petroleum is as fuel in different forms. It is also used for dry-cleaning. It is used for making lubricating oil, printing ink and medicines. Paraffin wax obtained from it is used to make candles, waterproof cartons and polish. ## Oral Questions Choose the correct answer. 1. Precious metals like gold, silver and aluminium / iron / platinum, are used for making jewellery. 2. Silver / Coal / Gold, is used as a fuel in blast furnaces in the steel industry. 3. Petroleum or crude oil is also called black gold / white gold / black diamond. ## Conserve Natural Resources "The earth has enough for everybody’s need but not enough for everybody’s greed," said Mahatma Gandhi. We must conserve natural resources. - To save fuel at home, we must keep our stoves and machines in good condition. ## We should use coal and oil very carefully. We should also use inexhaustible sources of energy like the sun, wind and water. ## Mineral deposits in the earth are limited. They should not be used carelessly or wasted while mining. ## Animals and plants too are gifts of nature to human beings. Since they depend on each other for their survival, the balance between the two must not be disturbed. ## Let us say it again - The earth is made up of rocks. Rocks are made of minerals. - Rocks are of three kinds--igneous, sedimentary and metamorphic. - Igneous rocks are formed by the cooling of magma. Sedimentary rocks are formed from sediments. Igneous or sedimentary rocks change into metamorphic rocks. - Other useful underground resources are minerals, metals, coal and petroleum. - Coal is formed from vegetable matter. - Petroleum is formed from dead remains of land and sea creatures. - We should conserve natural resources. ## Let us answer ### A. Tick (✔) the correct answer. 1. The base of plains, mountains and ocean beds is - metamorphic rocks. - sedimentary rocks. - igneous rocks. - none of these 2. This is not a main mineral of granite. - quartz - calcite - mica - feldspar 3. The traces of ancient plants and animals found in rocks are called - vessels. - fossils. - tonsils. - none of these 4. This is formed from trees and other plants which died millions of years ago. - sandstone - coal - granite - slate 5. Which of the following is obtained from petroleum and is used for making candles and waterproof cartons? - coal - pumice - marble - paraffin wax ### B. Write T for True or F for False. 1. Precious metals like gold and silver are used for making utensils. 2. Asia has more than one-third of the world's coal. 3. Fossil fuel and black gold are some other names of coal. 4. Dentists use powdered pumice for polishing our teeth. 5. Shale is used as an ornamental rock. ### C. Write short answers. 1. What are rocks made up of? 2. What are minerals? 3. What is slate commonly used for? 4. Name two valuable underground resources. 5. Name any two places in India where coal mines are situated. ### D. Answer these questions. 1. How are igneous rocks formed? 2. What are ores? Name any four common ores. 3. Why are coal and petroleum important to man? 4. Why is petroleum called a fossil fuel? 5. Write two uses of limestone.