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The underground water, bearing layer of the earth, which is below the water table is known as an aquifer.
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The valves ensure that no backflow of blood takes place and the blood continues to move only in one direction.
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Electric fuse is a safety device which is based on heating effect of an electric current.
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Sodium hydrogen carbonate (NaHCO3).
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Drip Irrigation is a technique of using narrow tubes to provide water to plants directly at their base. This helps in conservation of water.
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Root, stem and leaves.
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An image which can be obtained on a screen is called a real image.
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Rich in lather, mixed with oil, black–brown water that goes down the drains from sinks, showers, toilets, laundries is dirty and called wastewater.
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We can utilize rain water with the help of rain water harvesting techniques.
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(a) Ant:
Type of food-Sugar, food particles
Mode of feeding -Scraping
(b) Mosquito:
Type of food- Blood
Mode of feeding -Sucking
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Autotrophs means: Auto = self , trophs = nourishment
Autotrophic nutrition is the mode of nutrition in which organisms make food for themselves from simpler substances. Green plants and algae are autotrophs.
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Objects with white surface absorb less heat and reflect more. So, less heat from outside enters the house if the walls of houses are painted white and thus, making it more cooler.
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Distance travelled = speed X time
Speed = 5 km/h
Time = 3 h
So, distance travelled by the car = (5 x 3) km = 15 km
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Large ears of the elephant help it to hear even very soft sounds. They also help the elephant to keep cool in the hot and humid climate of the rainforest.
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The two types of fibres which form the hairy skin of the sheep are :
(a) The coarse beard hair.
(b) The fine soft under hair, close to the skin.
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The factory wastes contain acids which are harmful for the organisms living in water (fishes etc.). Hence, these are neutralized by adding basic substances.
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Decomposers are the organisms which convert the dead plants and animals to humus. Examples are bacteria, tiny insects, millipedes, earthworms, ants etc. Decomposers feed upon the dead plant and animal tissues and convert them into dark coloured substance called Humus, which provides nutrients for the soil. These nutrients are again absorbed by the roots of the living plants. In this way decomposers play an important role in maintaining the balance by the supply of nutrients to the growing plants after decomposing the dead plants and animals into humus.
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A liquid, containing wastes disposed off by household, agricultural and industrial activities in water, is known as sewage.
Untreated sewage contains harmful substances and disease causing organisms. Hence, it is dangerous and unsafe to discharge untreated sewage in water. It can pollute the whole source of water.
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An electric fuse is a safety device which is used to prevent damages to the electric circuits. It contains a wire made up of a material having low melting point so that if large current passes through it, then the heat will be generated due to heating effect of an electric current, which melts the wire and breaks the circuit. Hence, the damage to the electrical appliances and possible wires can be prevented.
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If we stand in front of a plane mirror and raise our left hand, then we will see our right hand been raised in the mirror as an image.
Similarly, if we touch our right ear, then it appears as we touch our left ear as an image.
So in plane mirror, the right side of an object appears to be the left side of an image and the left side of an object appears to be the right side of an image.
Thus, there is an interchange of sides of an object in images formed by the plane mirror.
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Burning of wood produces ash and smoke. So, the properties of wood are changed and new substances are formed. Hence, it is a chemical change.
When wood is cut into small pieces, there is no new substance formed. Each small piece has the properties of wood. Hence, it is a physical change. Thus, burning and cutting of wood are two different types of changes.
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A liquid, containing wastes disposed off by household, agricultural and industrial activities in water, is known as sewage.
Untreated sewage contains harmful substances and disease causing organisms. Hence, it is dangerous and unsafe to discharge untreated sewage in water. It can pollute the whole source of water.
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The three components of the circulatory system in humans are:
1) Blood: A red coloured fluid which carries oxygen, digested food and waste from one part of the body to other.
2) Heart: The pumping organ.
3) Blood vessels: Tubes through which blood can flow to different parts of the body.
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Sanitation and disease are related to each other. If sanitation is there, the probability of diseases will be low. But, if there is no sanitation, various types of diseases will occur and spread. So, to avoid diseases, proper sanitation should be maintained.
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The rainbow is seen as a large arc in the sky with many colours. It generally appears in the sky after the rain. When rain falls, then light from the sun is dispersed through rain drops into different colours and rainbow appears. There are seven colours in a rainbow. They are Violet, Indigo, Blue, Green, Yellow, Orange, and Red (VIBGYOR).
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(a) The two types of vascular tissues in plants are xylem and phloem.
(b) Plants absorb water and mineral nutrients from soil by the help of roots. The roots have root hair which increases the surface area of absorption of the roots. Water is then translocated to upper parts of the plants through xylem which forms a continuous network of channels. They connect roots to the leaves through stems and branches. Thus, water and other nutrients move to all parts of a plant.
(c) Stomata are tiny openings or pores present on the undersurface of the leaves used for exchange of gases. The pore is known as stoma which is surrounded by a pair of guard cells which are responsible for opening and closing of stomata. The stomata open when the guard cells are turgid, full of water and closes when there is excess loss of water through transpiration. The guard cells become flaccid resulting in closure of stomata.
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(a) Spirogyra (an alga) multiplies vegetatively by fragmentation. The algae grows rapidly in presence of water and nutrients. An algal filament breaks up into two or more fragments. These fragments or pieces grow into new individuals. This process continues and they cover a large area in a short period of time.
(b) Sporogenesis refers to the process of reproduction through spores. It occurs in reproductive structures known as sporangia which produce spores. Example: Moss and ferns.
(c) Hydra and yeast reproduce by the process of budding, where a new organism forms eventually and breaks away from the parent body.
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An electric heater is a device that converts electric energy into heat energy. It is based on the principle of heating effect of electric current.Electric appliances contain a coil of wire known as element.When an electric heater is switched on, the element becomes red hot due to the passage of current through it. This red hot element begins to give out heat.
An electric bulb is also based on the same principle, i.e., heating effect of electric current.
In case of an electric bulb, the element gets heated to such a high temperature that it begins to glow while the element of an electric heater does not get heated to such high temperature and so, it does not glow like an electric bulb.
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The wax of the candle melts, then vaporizes and burns. Melting of wax is a physical change as molten wax can be solidified back to the wax and no new substance is formed. When wax vapours burn, smoke and carbon dioxide are formed which are new substances. Hence, it is a chemical process.
Another example in which both the physical and chemical changes take place is - lightening of torch bulb using dry cell. Lighting of the torch bulb is physical change since no new substance is formed. The current from the dry cell is obtained by the chemical substances inside it. The chemicals in the cell get converted into new substances and hence the cell ultimately becomes useless. It is a chemical change.
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Forest is known as a “Dynamic living entity” i.e., full of vitality and life because of the following reasons:
1. As there are different varieties of plants in forest, it provides greater opportunity for food and habitat for the herbivores.
2. As there are large number of herbivores in forest, they increase the availability of food for a large number of carnivores.
3. Decomposers help in maintaining the supply of nutrients to the growing plants in the forests.
Thus life starts from plants, moves to herbivores then carnivores and in the end decomposers decompose the dead and decay material into the nutrients that plants use from the soil.
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The digestive tract and the associated glands.
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Temperature of our body can be measured by the help of clinical thermometer.
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The rearing of silkworms for obtaining silk is known as sericulture.
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Weather is defined as the condition of the atmosphere with respect to the temperature, humidity, rainfall, wind speed etc.
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Soil contain the rotting dead matter called as humus.
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Tornado is a dark funnel shaped cloud that reaches the ground from the sky. Mostly the tornadoes are weak. They can be form within the cyclones.
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The process of breakdown of food in the cell with the release of energy is called cellular respiration.
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Carbon dioxide Water chlorophyll Glucose Oxygen
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The process of taking out threads from the cocoon for use is known as reeling. e.g. reeling the silk means unwind threads or fibres of silk from the cocoon.
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Total distance traveled =2.4km=2.4x1000m=2400m.
Speed is 2m/sec
As time = (Distance/speed)
time=2400/2=1200sec.
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Similarity: Both amoeba and human use digestive juices to digest food.
Difference: Human needs to chew food whereas in amoeba, there is no chewing.
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Air gets trapped between two thin sweaters. Being a bad conductor of heat, air does not allow the body heat to flow outside. Hence, two thin sweaters keeps us warmer than wearing just one thick sweater.
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Polar bears have white fur so that they are not easily visible in the snowy white background, which help it to protect them from their predators. It also helps them in catching their prey. Polar bear have thick layer of fat to protect them from extreme cold.
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In summers, near the equator the land warms up faster and most of the time the temperature of the land is higher than that of water in the oceans. Thus, the air above the land gets heated up and rises upwards and the colder air from the oceans rush in, to take its place. These winds which flow from oceans to land are called monsoon winds. These winds from the oceans carry water with them and cause rain.
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Wind, rainfall, temperature, light and humidity are the factors which affect the soil.
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Earthworms breathe through their moist and slimy skins. Gases can easily pass through them. While frogs have a pair of lungs which are the important organ in the gaseous exchange like human beings. They can also breathe through their skin which is moist and slippery.
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Time taken = 20 minutes =20 X 60 seconds = 1200 seconds
Speed = 2 m/s
Distance = speed X time
= (2 X 1200) m
= 2400 m
Since, 1 km = 1000 m
Hence, distance = 2.4 km
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(i)The process of removing the fleece of sheep from its body along with a thin layer of skin is called shearing.
(ii)Usually shearing is done during the hot weather.
(iii)The fleece provides woollen fibres that are processed to obtain woollen yarn.
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An adaptation is trait of an organism that has been favoured by natural selection. Adaptations are of following types:-
- Structural adaptations are special body parts of an organism that help it to survive in its natural habitat (e.g., skin colour, shape, body covering).
- Behavioral adaptations are special ways of a particular organism that behaves to survive in its natural habitat.
- Physiological adaptations are systems present in an organism that allow it to perform certain biochemical reactions (e.g., making venom, being able to keep a constant body temperature).
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The materials which allow heat to pass through them easily are known as conductors. For example-copper, iron etc.
The materials which do not allow heat to pass through them are known as insulators. For example- wood, plastic etc.
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When an ant bites, it injects an acidic liquid into the skin, which causes the burning sensation and pain. Calamine solution (Zinc carbonate) is basic in nature. It neutralizes the acid and relieves us from the pain.
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Grass eating animals like cows, buffaloes etc. quickly swallow the grass and store it in a separate part of the stomach called rumen.
In rumen, the food is partially digested and is called cud.
The cud returns to the mouth in small lumps and is chewed by the animal. The process is known as rumination and the animals are called ruminants.
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When we blow air into the mouth of the bottle, the air has higher speed near the mouth. Due to this, the air pressure decreases there. The air pressure inside the bottle is higher than that near the mouth. The ball is pushed out by the air inside the bottle. This is why a paper doesn’t go inside.
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(a) When a pile of cocoons is either boiled or exposed to steam, the silk fibres separate out.
(b) The natural lustrous appearance of silk makes it attractive.
(c) Mulberry silk moth
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The differences between a parasite and a saprotroph are as follows:
| Parasite | Saprotroph |
| (1) A parasite mostly lives in or on the living host. (2) Parasite derives nutrients from the living organisms.
Example- Cuscuta (Amarbel) | (1) A saprotroph lives on dead and decaying matter. (2) Saprotroph derives nutrients from dead and decaying organisms.
Example - Fungi |
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(a) The climatic conditions in rainforests are highly suitable for supporting an enormous number and variety of animals. Tropical rainforests lie near to the Equator. This region receives rainfall distributed regularly throughout the year, about 6-33 feet a year. It remains frost free and warm all year long, with temperatures between 70° and 85°F with very little daily fluctuation. Because of continuous warmth and rain, this region supports wide variety of plants and animals. The major types of animals living in the rainforests are monkeys, apes, gorillas, lions, tigers, elephants, leopards, lizards, snakes, birds and insects. Tropical rainforests are found in Western Ghats and Assam in India, Southeast Asia, Central America and Central Africa.
(b) To overcome the competition for food and shelter, some animals are adapted to get food which is not easily reachable. Example, red-eyed frog has developed sticky pads on its feet to help to climb tress on which it lives. Another example is of the Toucan bird, which possesses a long, large beak. This helps a toucan to reach the fruits on branches which are otherwise too weak to support its weight.
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When an object covers equal distances in equal intervals of time then, it is said to be in uniform motion.
For example: If a car covers 100 km every hour, 50 km every half an hour, 25 km every quarter of an hour and so on, then its motion is said to be uniform.
Therefore, the truck covered a total distance of 30km.
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Different layers are referred to as horizons.
- The uppermost layer; the top soil, also called as A-horizon is generally dark in colour and fertile as it is rich in humus and minerals. This layer is generally soft, porous and can retain more water. This provides shelter for many living organisms such as worms, rodents, moles and beetles. The roots of small plants are embedded entirely in the topsoil.
- The next layer;middle layer called B-horizon has a lesser amount of humus but more of minerals. This layer is generally harder and more compact.
- The third layer is the C-horizon , which is made up of small lumps of rocks with cracks and crevices. Below this layer is the bedrock, which is hard and difficult to dig with a spade. water can be held in the tiny gaps.
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(a) Neutralisation reaction
(b) (i)No change (ii)No change
(c) Phenolphthalein gives pink colour with basic solution and remains colourless in acidic solution. Therefore, solution (X) is a base.
(d) China rose indicator gives dark pink colour with an acidic solution and green colour with a basic solution.
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The process of breathing in humans occurs as follows:
When air is inhaled, it passes through our nostrils into the nasal cavity. With the help of windpipe, the air reaches our lungs from the nasal cavity. From nasal cavity, the air enters the lungs. During inhalation, the ribs move up and outwards and diaphragm moves down. This occurs due to changes in the volume of lungs due to the movements of the rib cage and diaphragm. This movement causes a fall in the lung pressure due to which air rushes into the lungs. During exhalation, ribs move down and inwards, while diaphragm moves up to its former position. This reduces the size of the chest cavity, thereby increasing the pressure in the lungs and air is pushed out of the lungs.
