www.rsmaths99.com

CONTENTS

10.            Transport and Excretion

11.            Respiration in Plants and Animals

12.            Reproduction in Plants and Animals

13.            Weather, Climate and Adaptations

14.            Soil

 

BASIC SCIENCE CLASS VII

10.    TRANSPORT AND EXCRETION

A.

Q1.      What carries the water absorbed by the root to the leaves of a plant?

Ans.     The water absorbed by the root is carried to the leaves of the plant through a system of pipes which are formed by a special tissues called xylem.

Q2.      What does a doctor feel when he checks our pulse?

Ans.     When a Dr. check our pulse he feels our artery throb. This throbbing is called pulse. In other wards we can say that Dr. checks our pulse rate.

Q3.      Why is the heart divided into two  halves by a thick wall?

Ans.     The heart divided into two  halves by a thick wall as this wall prevents oxygenated blood from mixing with deoxygenated blood.

Q4.      Name the organs which comprise the urinary system.

Ans.     The urinary system consists of the kidneys, ureters bladder and urethra.

Q5.      How does the waste filtered by the nephrons reach the urinary bladder?

Ans.     A nephrone is a tiny filters and looks like a small cup with a long tube attached to it. Waste blood filters into the cup and flows through the tubes and collected in larger tube called ureters. Finally ureters carry the waste to the urinary bladder.

Q6.      When there are two solutions separated by a semi permeable membrane, what determines which way substances will flow?

Ans.     Two solutions separated by a semi permeable membrane, the concentration of these solution determine the direction of the flow and the substance will flow from a weaker to a stronger solution through a semi permeable membrane. 

Q7.      What do we excrete in the process of sweating?

Ans.     When we sweat, we excrete water, salt and urea.

B.

Q1.      How does water move up the stem against the force of gravity?

Ans.     Two forces- a push and a pull help to pump up the sap. The absorption of water by the root produces a push. But a much stronger force is the pull produced by transpiration. These two forces work together to move the water up the stem against the force of gravity.     www.rsmaths99.com   

Q2.      Which side of the heart receives blood from all over the body? What happens after that?

Ans.     Right side of the heart receives deoxygenated blood from all over the body. It received by  right artrium and transfer it to right ventricle. Heart pumps the blood to the lungs, where the blood gives up carbon dioxide and receives oxygen, oxygenated blood  enters the left atrium  and reaches the left ventricle .Then heart pumps it to the rest of the body.

Q3.      How does sweating help to maintain our body temperature?

Ans.     The evaporation of sweat requires heat. It is natural that our skin has some heat. When we sweat, the water in the sweat absorb this heat and evaporates. Due to this absorption of heat we feel cool. By this way sweating helps to maintain our body temperature.

Q4.      Why does an egg without its shell swell when it is placed in a bowl of water?

Ans.     when an egg without its shell swell is placed in a bowl of water it swells because the water flows from higher to the lower concentration as egg is having lower concentration of water. The membrane of egg behaves like a semi permeable membrane and through osmosis water flows outer to the inner part of the egg.

            NOTE:                                                                          www.rsmaths99.com   

            Suppose a solution of Root(solute) + Soil(solute). Solvent: water + minerals.

           

Root

 

Soil

1.

Strong solution(more concentrated)

1.

ß

Weaker solution(less concentration)

2.

Concentration of water is low (less water)

2.

ß

Concentration of water is high

(more water)

            Osmosis : is the passage of a solvent from a weaker to a stronger solution

through a semi permeable membrane. ‘OR’

            Osmosis : The process of transfer of water across a semi permeable membrane

 from a region where its concentration is higher to a region where its

 concentration is lower is called osmosis.

Similarly:

           

Honey

 

Egg

1.

Strong solution( content of honey- more concentrated)

1.

ß

Weaker solution( content of egg- less concentration)

2.

Concentration of water is low (less water)

2.

ß

Concentration of water is high

(more water)

           

Similarly:

                       

Egg

 

Bowl of water

1.

Strong solution( content of egg- more concentrated)

1.

ß

Weaker solution( content of water- less concentration)

2.

Concentration of water is low (less water)

2.

ß

Concentration of water is high

(more water)

 

C.

Q1.      How do roots absorb water from the soil?

Ans.     Water passes from the soil into the root hairs because the solution inside them is stronger then the solution of minerals and water in the soil. In other wards, the concentration of water in the soil is higher than the concentration of water inside the root hairs. The process of transfer of water across a semipermeable membrance from a region where its concentration is higher to a region where its concentration is lower is called osmosis.    www.rsmaths99.com   

Q2.      What are nephrons? How do they help in the excretion of waste?

Ans.     The millions of tiny filters in the kidney are called nephrons. A nephron looks like a small cup or funnel with a longish tube attached to it. There is a mesh of capillaries in each of these cups. Water and waste like urea and salt filter into the cups from the blood in capillaries. Blood cells and other large particles remain in the blood in the capillaries. The clean blood leaves the kidney, while the waste flow into the tubes of nephrons. These tiny tubes join up to form bigger tubes which, in turn, join the ureters.

Q3.      What is dialysis? How is it carried out?

Ans.     When a person suffers from kidney failure he has to undergo dialysis. Dialysis is the process of removing wasts from the blood artificially. The patient’s blood is taken out of an artery and allowed to pass through a tube whose wall is semipermeable. The tube, which is dipped in a solution, acts like a sieve. It allow the smaller waste particles to pass out of the blood in the solution. But it does not allow the blood cells and proteins, which are larger to pass through.  

D.         1. Xylem      2. Sap     3. Heartbeat   4. Semipermeable      5. Lower 6.artium and ventricle

E.         1. – (c) transpiration   2. – (a) proteins     3. – (b) capillaries   4.(b) 72/min.

F.         a – v    b - iii    c – ii    d – vi   e – vii  f – iv   g - i

11.    RESPIRATION IN PLANTS AND ANIMALS

A.

Q1.      How do earthworms breathe?

Ans.     Earthworms breathe through their skin.     www.rsmaths99.com   

Q2.      How does an insect take in air and how does the air reach the different parts of its body?

Ans.     An insect take in air through their spiracles. They have small holes called spiracles on their side, air enters through these holes and reaches all parts of the body through a network of tiny tubes called tracheas or breathing tubes.

Q3.      What is respiration rate?

Ans.     The number of times we breathe in and out in a minute is called respiration rate.

Q4.      How do the leaves of plants exchange gases with the atmosphere?

Ans.     The leaves of plants exchanges with the atmosphere through stomata.

Q5.      Why do gardeners loosen the soil from time to time?

Ans.     Loosing of soil creates air space between the soil particles. This air is essential for the root.

Q6.      When does anaerobic respiration occur in our body?

Ans.     This happens especially when we do something strenuous.

Q7.      What roles do the hair and the membrane of the nasal cavity play?

Ans.     Dust and other particles present in air get trapped by the mucus and hair present in the cavity.

B.

Q1.      How do fish and tadpoles breathe?

Ans.     Fish and tadpoles use gills- gills have filaments, which are somewhat like the teeth of combs. The filaments are full of small capillaries carrying blood. Water entering through the mouth flows over the gills. The oxygen dissolved in the water enters the capillaries and carbon dioxide from the capillaries passes out into the water.

Q2.      Why does the respiration rate increase after exercise?

Ans.     The respiration rate increase after exercise because when we are doing exercise our body utilizes more energy then usual. This requirement is fulfilled by an increase in the respiration rate, which increase the amount of oxygen in the body.

Q3.      What are the two steps involved in respiration?

Ans.     The two steps involved in the respiration are :-

1.      Internal respiration & 2.             External respiration.   www.rsmaths99.com   

Q4.      What is anaerobic respiration? How do we make use of it?

Ans.     The process by which food is broken down to release energy in the absence of oxygen is called anerobic respiration. Yeast and many bacteria respire by this way.The process, also called fermentation, is used in making wine and bread.

C.

Q2.      Describe the path taken by inhaled air from the nostrils to the lungs.

Ans.     Air enters our body through the nostrils and passes into the nasal cavity. From there it travels through the pharynx, treachea, bronchi and bronchioles, into alveoli. Alveoli are tiny air sacs.

Q3.      What makes air enter our lungs when we inhale?

Ans.     When we inhale, the chest muscles pull down the diaphragm. At the same time the ribcage move outwards. Both these movements increase the volume of the chest cavity and makes air rush in to fill the alveoli.    www.rsmaths99.com   

Q4.      How does oxygen from the air in the lungs reach the cells?

Ans.     The alveoli are surrounded by tiny blood vessels. Oxygen from the inhaled air passes into these and combines with haemoglobin to form oxyhaemoglobin. Blood carris the oxygen to the cells from the lungs and carries back carbon dioxide from the cells to the lungs. Carbon dioxide passes from the blood vessels into the alveoli and is thrown out when we exhale.

D.         1.        

12.    REPRODUCTION IN PLANTS

A.

Q1.      What are the different ways in which plants reproduce asexually?

Ans.     There are three ways in which plants reproduced asexually they are:-

1.      Spore formation

2.      Budding

3.      Vegetative reproduction.

Q2.      What is pollination?   www.rsmaths99.com   

Ans.     The transfer of pollen grains from anther to the stigma is called pollination.

Q3.      What happens to the ovary after fertilization?

Ans.     After fertilization the ovule develops into the seed, which contains the baby plant formed by the gygote. The ovary develops into the fruit.

Q4.      Name one plant in which seeds are dispersed by the explosion of the fruit.

Ans.     Jasmine is  one plant in which seeds are dispersed by the explosion of the fruit.

Q5.      Why do seeds need to be dispersed?

Ans.     Seeds have to be dispersed in order that they do not have complete with the parent plant for water, minerals and light.

B.

Q1.      What is vegetative reproduction? Why is it also called vegetative propagation?

Ans.     In vegetative reproduction, new plants develop from parts other then the reproductive organs.

            Plants which are capable of vegetative reproduction are propagated(grown) extensively by making use of the vegetative parts from which new plant can grow. This is why the terms ‘vegetative reproduction’ and ‘vegetative propagation’ are used.

Q2.      How do insects help to bring about pollination?   www.rsmaths99.com   

Ans.     When the anthers mature, they burst and release pollen grains. These pollen grains stick to the body of insects and birds visiting a flower to gather nectar. When the bird or the insect visits another flower, some of the pollen grains get dusted of on to the stigma.

Q3.      What are the special features of wind-pollinated flowers?

Ans.     The flower of some plants are small and produce huge quantities of small, dry and light pollen grains. The pollen has to be small, dry and light to be carried by the wind. It is produced in great quantities because a lot of it is lost is being blown by the wind.

Q4.      What is unisexual flower? Name one. Can such a flower be self-pollinated?

Ans.     Unisexual flowers are those flowers that have either the male part or the femal part.

            No, self-pollination is not possible in such flowers. Ex. – maize.

C.

Q1.      Distinguish between self-pollination and cross- pollination. How is pollen from other flowers prevented from reaching the stigma of a self- pollinated flower?

Ans.     Self Pollination – The pollen grains are carried to the stigma of the same flower.

            Cross Pollination - The pollen grains are carried to the stigma of the different flower of the same kind.

            Different plants have a different mechanism to prevent pollen grains from other flowers from reaching the stigma of a self- pollinated flower. Example peas, beans etc., are designed in such a way that the entry of pollen grains from other plants is not possible.

Q2.   Describe what happens after a pollen grain reaches the  

stigma.     www.rsmaths99.com   

Ans.  When a pollen grain reaches the stigma, a thin tube grows from the pollen grain called the pollen tube down through the pistil. It grows until it reaches the ovule and enters it. The male nucleus moves into the ovule and fuses with the egg to form the zygote.

Q3.   Describe the features of fruit/seeds dispersed by animals and the wind.

Ans.     Plants have devised ways by which seeds are dispersed. By animals, birds and other animals eat the fruit and throw away the seeds. Some plants have fruit or seeds with hooks, bristles or spines. They get attached to the fur of animals and carried away from the parent plant.

            By the wind, some plants have winged seeds, and some have tufts of hair such as cotton seeds which help them ride on the wind.

 

13.    WEATHER, CLIMATE AND ADAPTATIONS

A.

Q1.      What do you understand by the term ‘weather’?

Ans.    Weather is the atmospheric conditions in that place on that day and time.

Q2.      Mention three things that determines the climate of the place.

Ans.     Three things that determines the climate of the place are:

            (i) Latitude   (ii) height above sea level  (iii) distance from the sea

Q3.      What kind of thermometer is used to measure the maximum and minimum temperatures?    www.rsmaths99.com   

Ans.    Maximum and minimum thermometer is used to measure the maximum and minimum temperatures.

 

Q4.      Mention one adaptation that helps xerophytes survive the harsh conditions of their habitat.

Ans.    Xerophytes leaves are modified into spines and the spongy stem store water.

Q5.      What does a simple rain gauge consist of?

Ans.    A simple rain gauge is a graduated cylinder with a collector fitted on top.

Q6.      How are the flowering plants of polar regions adapted to their  habitat?

Ans.    The flowering plants of polar regions adapted to their  habitat by their short-lived and complete their life cycle during the short summer.

Q7.      Mention two adaptations that help elephants survive in their habitat.

Ans.    An elephant has two adaptations that help to survive in their habitant are –

            (i) Elephant have arge ears which helps to radiate heat from the body.

            (ii) It has a trunks they use it to spray water over their backs.

B.                                                                     www.rsmaths99.com   

Q1.      Why is city warmer than the surrounding rural areas?

Ans.    City is warmer than the surrounding rural areas because concrete absorbs more heat than the ground and  retains heat for longer. In urban area there are lack of trees but in  rural areas tree provides shade and cooling effect through transpiration.

Q2.      Name the instrument used to measure relative humidity. How does it work?

Ans.    Hygrometer is used to measure the relative humidity. A simple hygrometer consists of two thermometers. The bulb of one of the thermometers is wet. Since, evaporation causes cooling, the wet-bulb thermometer records a lower reading than the dry-bulb thermometer. The difference between the two readings is used to calculate the relative humidity.

Q3.      Mention two ways by which animals adapt themselves to a cold and two adaptations that help conifers survive in their habitat.

Ans.    Penguins and Polar bears have a very thick lyer of fat under their skin. This protects them from the cold and acts a store of food in winter. Polar bears survive on this store of fat when they sleep during the winter.

            Conifer have conical leaves that helps the snow slide off and their needlelike leaves reduce water loss through transpiration.

Q4.      How do camels survive in deserts?   www.rsmaths99.com   

Ans.    Camels have the following adaptations that help them to survive in the deserts-

            (i) Camel can drink large quantities of water at a go.

(ii) They excrete very concentrated urine to reduce the loss of water.

(iii)  They can also tolerate changes in their body temperature, which helps them cope with the hot days and cold noghts of the desert.

Q5.      What is disruptive coloration? How does it help?

Ans.    Some animal has stripes on their body such as tiger and zebras which help them to hide among tall grasses. This type of pattern on the body is called disruptive coloration. It breaks up the shape of the body visually and confuses the prey or predator.

Q6.      Why does the leeward side of a mountain not get much rainfall?

Ans.    When moisture-laden winds meet a range of mountains, they get pushed up. When it climb, causing condensation and bring rainfall. When the winds finally cross to the other side of the mountains they do not have enough moisture to bring rainfall. Thus, the leeward side of a mountain not get much rainfall as the windward side.

D.        1. Climate     2. Millimeters          3. ears            4. increases  5. Claws

            6. mammals  7.

E.         (a) Equatorial – (iii) broad-leafed evergreen trees

            (b) Tropical – (i) deciduous trees   www.rsmaths99.com   

            (c) Cool temperature – (v) conifers

            (d) Polar – (ii)mosses

            (e) desert – (iv) cacti

F.         1. – (b)Upper lip and nose   2.- (c)having different food preferences

            3. –(a) fog   4. – (d) all of these

 

14.    SOIL

A.

Q1.      What role does oxygen present in the air play in the formation of soil?

Ans.     The oxygen in the air reacts with some minerals on the rocks and makes the rocks crumble.

Q2.      How do changes in temperature help in weathering rocks?

Ans.     When the rocks are heated they expand. When they cool they contract. This constant expansion and contraction weakens them and make them break.

Q3.      Mention the various components of  soil?  www.rsmaths99.com   

Ans.     Soil contains mineral derived from rocks, humes formed by decomposition of organic matter, water and the soil.

Q4.      Which type of soil is considered the best for the growth of plants?

Ans.     Loamy soil

Q5.      Which type of soil has a grater water-holding capacity-sandy or clayey?

Ans.     Clayey soil

B.

Q1.      How does rain help in formation of soil?

Ans.     Rainwater loosens pieces rock and carries them with it. The pieces of rocks tumble and knock against each other and make themselves small. The flowing water deposits them on land when they slow down. The rainwater also enters cracks in rocks and freezes in winter. When water freezes it expands. This makes rocks crack further and break.    www.rsmaths99.com   

Q2.      What characteristic of soil have a role to play in the growth of plants?

Ans.     Soil contains mineral, water air and humus. It also contains bacteria, fungi, algae and tiny organisms which make the soil fertile and convert the nitrogen of the air into nitrogenous compounds that plants can use.

Q3.      Which layer of the soil supports the growth of plants? What are the characteristics of this layer?

Ans.     A horizon, this is the topmost layer of soil, often referred as topsoil. Its dark colour is due to the presence of humus. The particles of this layer are the finest and the action of decomposers makes this layer porous. This layer supports most plants.

Q4.      What is substratum? Is the topsoil always derived from this layer?

Ans.     Substratum is the third layer of the soil also called as C horizon. It consists of large pieces of broken rocks and coarse soil particles called gravel. It is derived from the layer of hard rock that lies beneath. No, the topsoil is not always derived from this layer.   www.rsmaths99.com   

Q5.      What happens to the rainwater that seeps through the topsoil?

Ans.     When rainwater seeps to the topsoil it dissolves soluble minerals and diposits them in the top layer.

C.

Q1.      What are the advantages and disadvantages of sandy and clayey soil?

Ans.     Advantages:

a] Clay Soil - The fine particles are packed more closely. Water clings to this type of soil and does not pass through easily. 

b] Sandy soil - Sandy soil are light and easy to plough. The layer particle s are packed loosely, so there is a lot of air spaces between them.

Disadvantages:

Clayey Soil – There is not enough space between particles for air. This type of soil is heavy and difficult to plough. When it dries it becomes really hard.

Sandy Soil – This type of soil doesnot hold water. It lets the water drain off. So the soil dries out soon after the rain and plants are deprived of water. The dry soil gets blown away easily.

Q2.      What are the organisms living in the soil called? How do they help to improve the fertility of soil?    www.rsmaths99.com   

Ans.     The organisms living in the soil are called biota. The help to improve the fertility of soil by breaking down organic matter and changing atmospheric nitrogen to nitrogenous compounds and aerating the soil.