CHAPTER 4: BODY MOVEMENTS
Have you stopped to notice the movements in your body? How do your body parts move when you walk, talk, eat, speak or even breathe? In this chapter we will study how movements happen.
HUMAN BODY AND ITS MOVEMENTS:
If you think about it, you’ll notice that certain parts of your body move in a fixed direction while there are other parts that you can freely move in all directions. Some parts cannot be moved at all.
You see, there are places in our bodies where our body parts seem to join. These are the places where we can bend or rotate our body. The places where the bones join together are called joints. We can bend or move our body only at the joints.
Let us see the different types of joints:
1. Ball and socket joints: When the rounded end of one bone fits into the hollow space (called cavity) of the other bone, the joint is called a ball and socket joint. This joint allows movements in all directions. E.g.: Shoulder joint
Ball and socket joints
2. Pivotal joints: In a pivotal joint, a cylindrical bone rotates on a ring. For e.g.: Where the neck joins the head is a pivotal joint.
3. Hinge joints: These joints only allow back and forth movements. For e.g., Knee joint is a hinge joint.
4. Fixed joints: When the bones cannot move at the joint, it is called a fixed joint. For e.g., When you open your mouth, only the lower jaw moves. The upper jaw does not move. This means that the joint between the upper jaw and the head is a fixed joint.
The joints are a part of a bigger structure. All the bones on our body form a framework to give a shape to our body. This framework is called a Skeleton.
The major parts of the skeleton are:
1. Rib Cage: The chest bone and the backbone together form a box like structure called the rib cage. There are some important internal organs that lie inside the rib cage.
2. Backbone: The series of small bones at the center of the back is called the backbone. The rib cage is joined to these bones.
3. Shoulder bones: Either of the two flat triangular bones on each side of the shoulder is called shoulder bone.
4. Pelvic bones: Pelvic bones enclose the portion of your body below the stomach. This is the part that you sit on.
5. Skull: The skull is made up of many bones joined together. It encloses and protects your brain which is the most important part of your body.
There are some additional parts of the skeleton that are not as hard as the bones and which can be bent. These are called cartilage. The upper part of your ear has cartilage. In fact, cartilage is also found in joints of the body.
Another important component utilized in the movement of the body is muscle.
Muscles work together to move a bone. When contracted, the muscle becomes shorter, stiffer and thicker. It pulls the bone. Muscles work in pairs. When one of them contracts, the bone is pulled in that direction. The other muscle of the pair relaxes. To move the bone in the opposite direction, the relaxed muscle contracts to pull the bone towards its original position, while the first relaxes.
A muscle can only pull. It cannot push.
GAIT OF ANIMALS
Gait means the manner of walking or moving. Different animals have different gait. Let us see some examples.
The body of an earthworm is made up of many rings joined end to end. earthworm does not have bones. It has muscles which help to extend and shorten the body. During movement, the earthworm first extends the front part of the body, keeping the rear portion fixed to the ground. Then it fixes the front end and releases the rear end. It then shortens the body and pulls the rear end forward. This makes it move forward by a small distance. Repeating such muscle expansions and contractions, the earthworm can move through soil. Its body secretes a slimy substance to make the movement easier.
An earthworm also has a number of tiny hair like structures called bristles which are connected with the muscles. These bristles help the earthworm get a grip on the ground.
A snail carries a rounded structure on its back. This structure Is called the shell. It is not made of bones but is still called the outer skeleton of the snail. A thick structure and the head of the snail may come out of an opening in the shell. The thick structure is its foot, made of strong muscles. The foot has a wavy motion which helps the snail in moving.
Birds can fly in the air and also walk on the ground. Birds can fly because their bones are hollow and light. The bones of the hind limbs are for walking and perching. The bony parts of the forelimbs are modified as wings. Birds have strong shoulder bones. The breastbones are modified to hold muscles of flight. The muscles of flight are used to move the wings up and down.
The head and tail of the fish are smaller than the middle portion of the body –the body tapers at both ends. This body shape is called streamlined. The shape is such that water can flow around it easily and allow the fish to move in water. The skeleton of the fish is covered with strong muscles. During swimming, muscles make the front part of the body curve to one side and the tail part swings towards the opposite side. The fish forms a curve. Then, quickly, the body and tail curve to the other side. This makes a jerk and pushes the body forward. A series of such jerks make the fish swim ahead. This is helped by the fins of the tail. Fish also have other fins on their body which mainly help to keep the balance of the body and to keep direction, while swimming.
CHAPTER 6 GARBAGE IN, GARBAGE OUT
All the waste material that we throw out because we do not need it constitutes garbage. There is so much garbage generated every day. From plastic bags to broken toys or something as simple as a tissue comes under garbage. Imagine if we were surrounded by all the waste material that we simply throw away. It is, therefore, important to deal with all the waste material.
SOURCES OF GARBAGE:
A few major sources of garbage are:
DEALING WITH GARBAGE
Municipal workers collect the garbage in trucks and take it to landfills. A landfill is a low lying area used to dump wastes. Once the garbage is dumped in landfills, the reusable components are separated from the non-reusable components. The non-reusable component is then spread over the landfill and covered with soil.
Many people deal with garbage by burning it. You must have seen people burning dried leaves on the side of the road. This way of dealing with garbage, however, is extremely harmful for our health as it produces smoke and gases which pollute the environment.
The method of preparing compost with the help of redworms is called vermicomposting. The redworms used for this purpose do not have teeth. They have a structure called ‘gizzard’, which helps them grind their food. Redworms do not survive in very hot or very cold surroundings. They also need moisture around them. The compost prepared by vermicomposting can be used as manure for agricultural purposes.
THINK AND THROW
A major step that can reduce the amount of garbage is thinking before throwing. If you think something can be reused then don’t throw it. For example, instead of throwing plastic bags away, you can use them later to carry something when you need to.
BIODEGRADABLE AND NON-BIODEGRADABLE WASTE
Biodegradable wastes are the waste products that can be easily decomposed by natural elements like bacteria, etc. Examples of biodegradable wastes are vegetable and fruit matter, paper, human and animal wastes etc.
Non-biodegradable wastes are the waste products that cannot be easily decomposed by natural elements. Examples of non-biodegradable wastes are plastic, metals, etc.
Plastic constitutes a major part of our daily life. Let’s look at some of the things we use that are made of plastic. Pens, bottles, toys, bags, buckets, chairs and many more. Using plastic is not a problem. Disposing the plastic is what causes a problem. Plastic is non-biodegradable so it cannot be decomposed. It can however be reused. Make sure to reuse plastic bags and reduce the wastage of plastic.
Plastic cannot be burned. Plastics give out harmful gases on heating or burning. These gases cause a lot of health problems. Plastics can also not be decomposed. The plastic bags thrown on the road get into the sewer system and cause blocking of drains., Sometimes when food items are thrown away in these plastic bags and animals looking for food end up eating the plastic bag which can cause their death.
So, there is no actual way to get rid of the plastic. It is an unnecessary evil. It is, therefore, important to manage plastic waste as efficiently as possible to avoid pollution.
CHAPTER 5 THE LIVING ORGANISMS AND THEIR SURROUNDINGS
The things that move, grow, breathe, need food, feel changes, and reproduce are called living things. The main characteristics of living things are:
An organism, in simple words, is an individual living thing. From microscopic bacteria to an elephant, all living forms are organisms.
ORGANISMS AND THEIR SURROUNDINGS: HABITAT AND ADAPTATION
The process of change by which an organism becomes better suited to its environment is called adaptation.
A habitat is the natural environment and surroundings in which a particular organism lives. The organisms depend on their habitat for their food, water, shelter and other needs.
There are different types of habitats. Some of them are as follows:
1. Terrestrial habitats: The plants and animals that live on land are said to live in terrestrial habitats. For e.g.: forests, grasslands, deserts, etc. Deserts are habitats which do not have much water so naturally the organisms in the desert need to be able to survive without water.
2. Aquatic habitats: The plants and animals that live in water are said to live in aquatic habitats. For e.g.: Ponds, swamps, lakes, oceans, etc.
Some terrestrial habitats:
Deserts: Desert animals like rats and snakes do not have long legs so to stay away from the intense heat, they stay in burrows deep in the sand. Animals like camels store water in their body to survive the lack of availability of water. Desert plants lose very little water through transpiration. The leaves in desert plants are either absent, very small or in the shape of spines. This helps is reducing loss of water from the leaves.
Mountain Regions: Mountain regions are very cold and windy. Animals living in the mountain regions have thick skin or fur to protect them from the cold. The plants that grow in the mountain regions are normally cone shaped and have sloping branches. This helps the rainwater and snow to slide off easily.
Grasslands: Grasslands are the areas where the plants are dominated by grasses. Animals that live in the grasslands range from lion (a predator) to a deer (a prey).
Some aquatic habitats:
Oceans: Many other sea animals have streamlined bodies to help them move easily in water. There are some sea animals like dolphins and whales that do not have gills. They breathe in air through nostrils or blowholes that are located on the upper parts of their heads. This allows them to breathe in air when they swim near the surface of water. The plants in the oceans and seas grow on the ocean floor.
Ponds and lakes: Some plants have their roots fixed in the soil below water. In aquatic plants, roots are much reduced in size and their main function is to hold the plant in place.
BIOTIC AND ABIOTIC THINGS AROUND US
Biotic components: The living things in a habitat are called its biotic components. E.g.: Plants, animals, etc.
Abiotic components: The non-living things in a habitat are called its abiotic components. E.g.: Air, water, soil, etc.
CHAPTER 3: GETTING TO KNOW PLANTS
Have you ever observed the plants around you? Do you see how different they are? Some plants are huge and some are just tiny shrubs. Let us see the different parts of a plant
CLASSIFICATION OF PLANTS:
Plants can be classified into three categories based on their various characteristics:
1. Herbs: Plants with green and tender stems are called herbs. They are usually short and may not have many branches.
2. Shrubs: Some plants have the stem branching out near the base. The stem is hard but not very thick. Such plants are called shrubs.
3. Trees: Some plants are very tall and have hard and thick brown stem. The stems have
branches in the upper part, much above the ground. Such plants are called trees.
There are also creepers which are plants with weak stems that cannot stand upright and spread on the ground while those that take support on the neighbouring structures and climb up are called climbers.
PARTS OF PLANT:
1. Stem: Stem conducts water. Minerals dissolved in water also move up in the stem, along with the water. The water and minerals go to leaves and other plant parts attached to the stem, through narrow tubes inside the stem.
2. Leaf: The part of a leaf by which it is attached to the stem is called petiole. The broad,
green part of the leaf is called lamina. The lines on the leaf are called veins. The thick vein in the middle is called the midrib. The design made by veins in a leaf is called the leaf venation. If this design is net-like on both sides of the midrib, the venation is called reticulate. But if the veins are parallel to one another, it is called parallel venation.
The functions of leaves are transpiration and photosynthesis. Transpiration is a process by which water comes out of the leaves in the form of vapour. Photosynthesis is a process through which leaves prepare their food in the presence of sunlight and a green coloured substance present in them. Oxygen is given out in this process. The food ultimately gets stored in different parts of plant as starch.
3. Roots: Roots are the part of the plant that is under the soil. The roots help in holding the plant firmly in the soil. They are said to anchor the plant to the soil. There are two types of roots:
(i) Tap root: There is one main root and many small roots.
(ii) Fibrous root: There is no main root. All the roots are similar.
4. Flower: A flower is the reproductive part of the plant. Let us see the different parts it has:
(i) Petals: The prominent parts on an open flower are called petals.
(ii) Sepals: The small leaf like structures are called sepals.
(ii) Pistil: The innermost part of a flower is called pistil. The pistil also has stigma, style, ovary.
(iii) Ovary: It is the lowermost, swollen part of the pistil. It contains small bead-like structures called ovules.
The number of sepals, petals, stamens, etc. may be different in different flowers. In fact, sometimes, some parts may also be absent.
CHAPTER 2 COMPONENTS OF FOOD
Do you know why your mother tells you to drink milk daily even though you may not like it? Well, it is because milk contains a lot of nutrients. What is a nutrient, you ask?
Okay, let’s try to understand what food is made up of.
You see, human body needs some important components to perform certain functions. These components are called Nutrients. A nutrient is a substance used by an organism to survive, grow, and reproduce.
The major nutrients are: Carbohydrate, Proteins, Fats, Vitamins and Minerals. We also need dietary fibres and water
Think about what you eat in a meal. A chapatti, dal and a vegetable is quite basic in a meal. The different food items form a balanced diet and add nutrients to your body.
A balanced diet is nothing but a proper combination of food that contains all the nutrients.
WHAT DO NUTRIENTS DO?
1. Carbohydrates: Carbohydrates provide us energy. Sources of carbohydrates are wheat, potato, sugarcane, rice, etc.
2. Fats: Fats also give us energy. However, fats give us more energy than carbohydrates. Sources of fats are milk, cream, butter, etc.
Note: Foods containing fats and carbohydrates are also called energy giving foods.
3. Proteins: Proteins are needed for the growth and repair of our body. Foods containing proteins are called body building foods. Sources of proteins are eggs, milk, paneer, etc.
4. Vitamins: Vitamins help in protecting our body from diseases. There are many types of vitamins such as Vitamin A, Vitamin B, Vitamin C, etc. Some sources of vitamins are fish oil and milk for vitamin A; orange and lemon for vitamin C; milk, butter and fish for vitamin D.
5. Minerals: Minerals are needed by our body in small quantities. They help in proper growth of the body and maintain good health. Sources of minerals are milk, spinach, eggs, etc.
6. Dietary fibres: Dietary fibres are also known as Roughage. They do not provide any nutrients but they help our body get rid of undigested food. Sources of roughage are whole grains, pulses, fresh fruits and vegetables.
7. Water: Water helps our body absorb nutrients from food.
For our proper growth and good health, our diet should have all the nutrients that our body needs. There should also be a good amount of roughage and water. A diet that contains a proper amount of all the nutrients is called a balanced diet.
A balanced diet can be different for different people depending on their age or the type of work that they do.
Food should also be cooked properly so that the nutrients are not lost.
Nutrition is important but the fact is that too much of a nutrient can cause problems. For e.g.: Too much fat can lead to obesity.
On the other hand, not enough of a nutrient can cause deficiency of that mineral.
Therefore, it is important to eat a balanced diet.
Sometimes the food we eat may lack a particular nutrient. If this continues over a long period of time, it may lead to a deficiency of that nutrient. Deficiency of one or more nutrients can cause disorders or diseases in our bodies. Such diseases are called deficiency diseases.
List of deficiency diseases:
CHAPTER 1 FOOD: WHERE DOES IT COME FROM?
Food is one of the most basic human requirements and there are so many sources that we can get food from. There are plants which provide us vegetables, cereals, fruits, etc. and then there are animals which give us milk, eggs, meat, etc.
Think about all the food items we eat at home. There are so many ingredients used in making the simple dishes. There are vegetables, spices, salt, oil and so much more.
What was the last thing you ate? Do you know about it? Where does it come from? How is it made?
To answer these questions, let us study in detail about the food we eat.
PLANT PARTS AND ANIMAL PRODUCTS AS SOURCES OF FOOD
We now know that plants and animals are the source of our food. Let us see how we get food products from them
Sometimes a plant can have two or more edible parts. You’ve eaten the fleshy part of a melon but did you know that the melon seeds can also be eaten? Talk about mustard. The seeds of the mustard plant give us oil and its leaves are used as a vegetable.
WHAT DO ANIMALS EAT?
What do you think animals eat? Do they eat plants? Do they eat other animals? Or do they eat both?
Well, animals can be classified into three groups:
In which group do you think humans are? Humans are omnivores. They eat both plants and other animals.
CHAPTER 6 AIR AROUND US
Air is simply a mixture of gases and dust particles. All living things need air. Humans and animals need it to breathe and plants need it for photosynthesis. Air is everywhere around you even if you think it isn’t. Even an empty bottle is not empty. It is filled with air.
Constituents of air
1. Water vapour
Air contains water vapour. The water that evaporates from water bodies or is released by plants through transpiration, reaches the atmosphere, as we’ve studied before. Water vapour in air is an important part of the water cycle.
Oxygen is vital for all living things for respiration. Oxygen is also necessary for burning. Plants replenish the oxygen in the atmosphere through photosynthesis. During photosynthesis, plants give out oxygen.
About 78% of the earth’s atmosphere is nitrogen. Nitrogen does not support burning.
4. Carbon dioxide
Plants and animals consume oxygen and give out carbon dioxide. The process of burning also releases carbon dioxide.
5. Dust and smoke
Smoke is a mixture of gases and dust particles which can be harmful. Dust particles are always present in some quantity in the air.
Oxygen and Nitrogen together make up 99% of the atmosphere. The remaining 1% contains Carbon Dioxide, other gases, water vapour and dust particles. Air is also dissolved in water and is also present in soils in the burrows and holes that animals (like rabbits) dig.
Air is, without a doubt, the most necessary prerequisite for living things to survive.
CHAPTER 5 WATER
Water is one of the most basic needs of humans. We need water not just for drinking but also for a number of other purposes like bathing, cooking, cleaning, etc.
Our very survival depends on water. Trees and crops use water to grow and they give us food.
Water cycle is a cyclic process through which water evaporates from the surface of the earth, reaches the atmosphere and then cools down to form clouds and then falls back to the surface.
Plants lose water by the process of transpiration. Tis releases water vapour into the air. In addition to this, water from the oceans and seas evaporates as it gets heated up by the sunlight. All this water vapour rises into the atmosphere.
As it goes higher into the atmosphere, it cools down and forms clouds. These clouds are nothing but tiny droplets of water. These droplets combine to form bigger drops of water which sometimes become so heavy that they start falling. This is what we call rain. Water can sometimes also fall in the form of hail or snow. This happens when the water gets so cold up in the atmosphere that it converts into solid form.
The rain or snow falls on the surface of the earth. It may fall on either on land or on water bodies like oceans, seas, etc. When it falls on the land, it gets absorbed by the ground. This adds up to the ground water which is either available in open wells or is drawn up by a hand pump or tube well.
This movement of water from the surface of the earth to the atmosphere and then back to the surface is called Water Cycle.
Droughts and floods
In some areas, rainfall is very less. But sometimes this lack of rainfall may continue for a very long period of time which may cause droughts. Drought is a long period of time characterized by abnormally low rainfall due to which there may be a shortage of water.
However, excessive rainfall is also not favourable. If there is abnormally more rainfall, the water level of water bodies like rivers and lakes increases. This may cause dry land to submerge in water. This is called flood.
Conservation of water
With the increasing population, the supply of water is decreasing every day. Although two-thirds of the earth’s surface is covered in water, most of it is in the oceans and seas. This is salt water and cannot be used for every day purposes. We have a very limited amount of fresh water supply due to which there is a shortage of water in many parts of the world. This makes it important to conserve water.
Rainwater harvesting is a way to conserve rain water. In order to make sure that rain water is not wasted, we can collect it. This is called rainwater harvesting. Rainwater can be collected and stored to be used later.
Rainwater can be harvested from rooftop and through pipes, it reaches the storage tanks. This water can be used for various household activities like washing clothes & utensils, cleaning and after filtering, it can be used for drinking and cooking as well.
Rainwater can also be allowed to go directly into the ground from drains that run along the side of the road.
CHAPTER 4 CHANGES AROUND US
A change is a process by which a material turns into something different that it was before. A tiny sapling becoming into a huge tree is an example of a change. The season turning from summer to winter is also a change.
Types of changes:
If we can reverse a change i.e. get back the material that we started with, it is called a reversible change.
If we cannot get back the material that we started with, the change is called non-reversible or irreversible.
Ways to bring a change:
Boiling Is when beyond which if water is heated, it starts to evaporate i.e. it changes from liquid to vapour.
This is the process by which water vapour cools down and changes into liquid state.
This is the process by which conversion takes place from liquid state to solid state.
This is the process in which conversion takes place from solid state to liquid state.
These changes can all be categorized into reversible and non-reversible changes. We’ll learn later about how the changes around us can be grouped.
CHAPTER 3 SEPARATION OF SUBSTANCES
There are many reasons as to why we might want to separate substances from a mixture. Some of them are:
There are a number of methods that can be used to separate a mixture of two solids. Some of them are:
In this method, the impurities are picked up by hand in order to separate them from the useful components. When the impurities are large in size and less in amount, handpicking can be used. This method is employed for separating dirt or stones from wheat and pulses.
When seeds have to be separated from the stalks, threshing is used. In order to free the grains from the stalks, the latter is beaten after drying them in the sun. Handpicking cannot be done in this case as each stalk has many grains attached to it. Therefore, threshing is used for this purpose.
Winnowing is used to separate mixtures when one component is lighter and the other one is heavier. The mixture is dropped from a height so that the lighter particles are carried away by the wind while the heavier particles fall straight down on the ground. This method is widely used by farmers to separate the wheat from the chaff.
In this process we pass the mixture through a sieve in order to remove the fine particles of impurity. A sieve is simply a mesh or a net through which the mixture is passed. This process is used in construction sites to separate sand from pebbles.
Separation of insoluble solids from liquids
1. Sedimentation, decantation and filtration
Sedimentation is used when the impurities i.e. the insoluble solid is heavier than the liquid and therefore it settles down to the bottom. This process is called sedimentation.
Decantation is when the liquid (along with the dust) is removed.
Filtration is when a filter medium which allows the fluid to pass through but retains the solid particles is used to filter out the fine solid particles from a liquid. Usually filter papers or strainers are used for filtration.
Separation of soluble solids
1. Evaporation and condensation
The process of conversion of water into vapour is called evaporation. Salt is obtained from sea water through this very process. Sea water is allowed to stand in shallow pits and when sunlight heats up the water, it slowly evaporates and the salt is left behind.
Condensation is the reverse process of evaporation. When water vapour converts into liquid form, the process is called condensation.