7

CBSE

SCIENCE

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New Delhi-110002

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Preface II

Exam Guru Science-V is based on the latest curriculum guidelines specified by the CBSE. It will certainly prove to be a torch-bearer for those who toil hard to achieve their goal. Salient Features of the Book: ●● The whole book is well designed to aim at total and easy learning. This will not only build their morale but confidence too. ●● Each chapter is subdivided into pictorial flow chart representation, important points to remember, different topics supplied with relevant and solved questions. ●● Flow charts on the onset of a chapter help in quick grasping of the concepts at a glance. ●● All topicwise exercises incorporates VSA-1/2/3 and LA for indepth practice and learning. ●● Most of the important questions from NCERT Text Book and NCERT Exemplar are included. ●● HOTS and Value Based Questions have been given to assess student’s understanding beyond the text and its application in real world. ●● ‘Did you know?’ added for additional general scientific knowledge related to each chapter. ●● Enrichment Activities added for subject enrichment knowledge. ●● Periodic Tests, Half-Yearly Tests and Yearly Examination Tests are provided at the end of the book. ●● Chapterwise Worksheets are provided at the end of each chapter prepare the student from examination point of view. Suggestions for further improvement of the book, pointing out printing errors/mistakes which might have crept in, in spite of all efforts, will be thankfully received and incorporated in the next edition. CBSE Circular No.: Acad-14/2017 Dated: 21/03/2017 Scholastic Area: The assessment structure and examination for classes VI to VIII have been prepared in view of the provisions of RTE-Act 2009 and comprises of two terms i.e. Term-1 and 2 as explained below: Subjects Term-1 (100 marks) Term-2 (100 marks) (1st half of the session) (2nd half of the session) 20 marks Periodic Assessment + 80 20 marks Periodic Assessment + 80 marks for marks for Half Yearly Exam Half Yearly Exam Language - 1 Half Yearly PA 20 Marks PA 20 Marks Yearly Exam Exam • Periodic Test • Periodic Test • Written exam for 80 marks Language - 2 • Written exam 10 marks with 10 marks with with syllabus coverage as for 80 marks syllabus covered syllabus covered below: Language - 3 till announcement with syllabus till announcement Class VI: 10% of 1st term covered till of test dates by Mathematics of test dates by covering significant topics + announcement school school entire syllabus of 2nd term Science of Half Yearly • Note Book • Note Book Class VII: 20% of 1st term exam dates by Submission 5 Submission 5 covering significant topics + Social school marks at term marks at term end entire syllabus of 2nd term Science end • Sub Enrichment Class VIII: 30% of 1st term Any other • S ub Enrichment 5 marks at term covering significant topics + Subjects 5 marks at term end end entire syllabus of 2nd term

(iii)

Contents 1. Nutrition in Plants................................................................................. 5 2. Nutrition in Animals............................................................................ 17 3. Fibre to Fabric..................................................................................... 29 4. Heat..................................................................................................... 38 5. Acids, Bases and Salts........................................................................ 53 6. Physical and Chemical Changes.......................................................... 66 7. Weather, Climate and Adaptations of Animals to Climate................... 76 8. Winds, Storms and Cyclones............................................................... 83 9. Soil.................................................................................................... 100 10. Respiration in Organisms.................................................................. 110 11. Transportation in Animals and Plants............................................... 121 12. Reproduction in Plants...................................................................... 134 13. Motion and Time............................................................................... 144 14. Electric Current and Its Effects......................................................... 156 15. Light.................................................................................................. 171 16. Water: A Precious Resource............................................................... 185 17. Forests: Our Lifeline.......................................................................... 197 18. Wastewater Story.............................................................................. 206 Chapterwise Enrichment Activities.................................................217-254 Term–1 • Periodic Tests (1 & 2)������������������������������������������������������������� 255-256 • Half Yearly Tests (1 & 2)��������������������������������������������������������� 257-260 Term–2 • Periodic Tests (1 & 2)..............................................................261-262 • Yearly Examination Tests (1 & 2)������������������������������������������ 263-268 • Chapterwise Worksheets.................................................................269-304

(iv)

1

Nutrition in Plants

Topics Covered 1.1 Nutrition and its Modes

1.2 Autotrophic Nutrition

1.3 Heterotrophic Nutrition and its Types

Flow Chart NUTRITION OF PLANTS

Autotrophic

Depend on plants for food

Heterotrophic

Plants

Animals

by the process

Photosynthesis

• • • •

Carbon dioxide + Water Sunlight Chlorophyll

Glucose + Oxygen

5

Parasites Insectivores Saprotrophs Symbiosis

– – – –

Cuscuta Pitcher plant Fungi Lichens and Rhizobium

Important Points to Remember • All organisms take food and utilize it to get energy for growth, maintenance and various life processes. • Based on the mode of getting food, organisms are classified as autotrophs and heterotrophs. • Autotrophs prepare their own food using simple inorganic materials like carbon dioxide and water. • Chlorophyll and sunlight are the essential requirements for photosynthesis. • Carbohydrates and oxygen are the products of photosynthesis. • Heterotrophs depend on autotrophs directly or indirectly for food. • Parasitic, saprophytic, insectivorous and symbiotic are the different modes of heterotrophic nutrition in plants. • Plants like Cuscuta are parasites as they take nutrition from the host plant. • Fungi derive nutrition from dead and decaying organic matter. They are saprotrophs. • Symbiotic relationship between Rhizobium and legumes helps in replenishing the soil of its lost nitrogen.

1.1 Nutrition and its Modes Nutrition is the mode of taking in food by the organism and its utilization by the body. Nutrients are the components of food necessary for our body. Nutrients serve different functions. They: – Enable us to build our bodies. – Help us grow. – Help repair damaged parts. – Provide energy to carry out life processes. Nutrition is of two types – autotrophic and heterotrophic. Autotrophs ( Auto- Self, Trophos – Nutrition) are the organisms that can make their own food from simple non – living substances. For example, green plants. Heterotrophs ( Heteros – Other, Trophos – Nutrition) are the organisms that directly or indirectly depend on green plants for nutrition. For example, all animals.

Exercise 1.1 I. Very Short Answer Type Questions (1 Mark) 1. Fill in the blanks: (a) ____________ is the intake of food and its utilization by the body. (b) The two modes of nutrition are _____________ and _____________. (c) ______________ are autotrophs.

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Science–7

(d) Generally all ________________ are heterotrophs. (e) ____________ are the components of food necessary for our body.

II. Short Answer Type Questions (2 Marks)

2. List any four uses of nutrients in our body. 3. Define nutrients and nutrition. 4. Explain, “Heterotrophs depend on autotrophs directly or indirectly for food.” 5. Are all animals heterotrophs? 6. State the main difference between autotrophs and heterotrophs.

Answers 1. (a) Nutrition (b) Autotrophic, heterotrophic (c) Green plants (d) Animals (e) Nutrients 2. Four uses of nutrients are: (i) Enable us to build our bodies. (ii) Help us to grow. (iii) Help repair damaged parts. (iv) Provide energy to carry out life processes. 3. Nutrients are the components of food necessary for our body. Nutrition is the mode of taking in food by the organism and its utilization by the body.

4. Heterotrophs cannot prepare their own food, they either depend on plants (herbivores) directly or indirectly as carnivores for food. 5. All animals are heterotrophic in nature. An exception is Euglena, a protozoan, that has chlorophyll and can therefore photosynthesize. 6. Autotrophs

Heterotrophs

These organisms prepare their own food.

These organisms depend on autotrophs directly or indirectly for food.

E.g. green plants.

E.g. generally all animals

1.2 Autotrophic Nutrition • Leaves are the food factories of plants. They are green in colour as they contain chlorophyll. • Sun is the ultimate source of energy for all living organisms. • Plants use carbon dioxide and water in the presence of sunlight and chlorophyll to make food by photosynthesis (photo – light, synthesis – to make). Food is made in the form of carbohydrate (sugar) and is stored in the form of starch. Oxygen is also released in this process. • Water and minerals present in the soil are absorbed by roots and transported to leaves by vessels that form a continuous passage. Carbon dioxide is taken in through tiny pores generally present on the lower surface of the leaves (stomata). Photosynthesis is important for life as: • Survival of all living organisms directly or indirectly depends on food made by plants.

Nutrition in Plants 7

Photosynthesis

• Oxygen, which is essential for survival of all living organisms is released during this process. • Photosynthesis is the process by which plants make their own food using carbon dioxide and water from the environment in the presence of sunlight and chlorophyll. Carbohydrates and oxygen are the products. It is the only process by which solar energy trapped by plants is converted into chemical energy of food and hence it is a unique process. Chlorophyll

Carbon dioxide + water æææææ→ glucose + oxygen Sunlight

Stomata (sing. stoma) are tiny pores generally present on the underside of leaves. They carry gaseous exchange and transpiration. A pair of guard cells surround stomata and control its opening and closing.

              Stoma open         Stoma closed

Activity: To show that sunlight is necessary for photosynthesis and that food is stored in the form of starch in leaves. Method: • Take two potted plants of the same kind.

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Science–7

• Keep one of them in dark for three days and another one in sunlight. • Pluck a leaf from each one of them and boil them in spirit heated over a water bath. • Wash the leaves with water and put a drop of iodine solution on both of them. • Record your observations. • Now keep the plant (that was earlier kept in dark ) in sunlight for a few hours and perform the iodine test on its leaf again. Observation • The leaf of the plant kept in sunlight shows blue-black colour with iodine solution while the leaf of the plant kept in the dark does not show this colour change. This is because starch is made in the leaf kept in sunlight but not in the leaf kept in the dark. • When the plant kept in the dark was shifted to sunlight, the leaf showed blue‑black colour with iodine solution confirming the presence of starch. Result Sunlight is necessary for photosynthesis and leaves make food in the form of starch. Sun

Small beaker Green leaf Spirit Water

Potted plant (having green leaves)

Water bath (Big beaker)

Potted plant (having green leaves)

Burner

Plant kept in sunlight

Plant kept in dark

Leaves boiled in spirit

Dropper

Dropper

No blue-black colour produced (No starch present)

Blue-black colour produced (Starch present) Leaf from plant kept in sunlight

Leaf from plant kept in dark

Sunlight is necessary for photosynthesis

Nutrition in Plants 9

• Leaves other than green also have chlorophyll and they photosynthesize. • The slimy green patches on the surface of ponds and other stagnant water bodies are called algae. Since they have chlorophyll, they photosynthesize. • Plants make food in the form of carbohydrates that are made up of carbon, hydrogen and oxygen. These elements can also be used to make proteins and fats. • Plants need nitrogen to make proteins that they get from fertilizers or by the action of nitrogen fixing bacteria.

Exercise 1.2 I. Very Short Answer Type Questions (1 Mark) 1. Fill in the blanks: (a) _____________ is the green pigment found in the leaves. (b) Food is stored in plants in the form of _____________. (c) The exchange of gases in plants takes place through tiny pores called _____________. (d) When iodine is added to starch, it becomes _____________ in colour. (e) The ultimate source of energy for all our needs is the _____________. (f ) _____________ cells control the opening and closing of stomata. (g) ‘Photo’ in the term photosynthesis refers to _____________. (h) The site of photosynthesis in green plants are the _____________. (i) Raw materials required for photosynthesis are _____________ and _____________. (j) _____________ is used to extract chlorophyll from the leaf in the given activity.

II. Short Answer Type Questions-I (2 Marks) 2. State the functions of stomata. 3. Write the word equation for manufacture of food in green plants. 4. What are the raw materials and the products of photosynthesis? 5. Do leaves other than green also photosynthesize? How? 6. What are the slimy green patches on the surface of ponds? Are they capable of photosynthesis? 7. Which elements make up carbohydrates? Which other components of food can be made from these elements? 8. Besides the elements mentioned above, which other element is needed by plants to make proteins. How do plants get it?

III. Short Answer Type Questions-II (3 Marks) 9. What are stomata? Where are they normally found? What controls their opening and closing?

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10. Why is photosynthesis a unique process? 11. Why is photosynthesis essential for life? 12. How do raw materials for photosynthesis enter the plant? 13. Draw and label open stoma. 14. Draw a diagram showing photosynthesis.

IV. Long Answer Type Questions (5 Marks) 15. Write an activity to show that sunlight is necessary for photosynthesis.

Answers

1. (a) Chlorophyll (b) Starch (c) Stomata (d) blue – black (e) Sun (f ) Guard (g) Light (h) Leaves (i) Carbon dioxide, water (j) Spirit 2. They carry gaseous exchange and transpiration. 3. Carbon dioxide + water Chlorophyll æææææ→ Sunlight

glucose + oxygen

4. Carbon dioxide and water are the raw materials. Carbohydrates and oxygen are the products. 5. Yes, leaves other than green also photosynthesize. They also have chlorophyll which is masked by other pigments. 6. The slimy green patches on the surface of ponds and other stagnant water bodies are called algae. Since they have chlorophyll, they photosynthesize. 7. Carbohydrates are made up of carbon, hydrogen and oxygen. These elements can also be used to make proteins and fats. 8. Besides other elements, plants need nitrogen to make proteins that they get from fertilizers or by the action of nitrogen fixing bacteria.

9. Stomata (sing. Stoma) are tiny pores generally present on the underside of leaves. A pair of guard cells surround stomata and control its opening and closing. 10. It is a unique process as it is the only process by which solar energy trapped by plants is converted into chemical energy of food. 11. Photosynthesis is important for life as (a) Survival of all living organisms directly or indirectly depends on food made by plants. (b) Oxygen, which is essential for survival of all living organisms, is released during this process. 12. Water and minerals present in the soil are absorbed by roots and transported to leaves by vessels that form a continuous passage. Carbon dioxide is taken in through tiny pores generally present on the lower surface of the leaves (stomata). Guard cells (swollen/turgid) Cell wall Chlorophyll



Chloroplast

13.

Vacuole Stomatal pore Nucleus

Stoma open

Nutrition in Plants 11

Oxygen released into the atmosphere Sun



Chlorophyll Light energy trapped from Sun Light

14.

Carbon dioxide

Glucose formed

Water

Soil

Minerals

Photosynthesis

15. Activity: To show that sunlight is necessary for photosynthesis and that food is stored in the form of starch in leaves. Method: • Take two potted plants of the same kind. • Keep one of them in dark for three days and another one in sunlight. • Pluck a leaf from each one of them and boil them in spirit heated over a water bath. • Wash the leaves with water and put a drop of iodine solution on both of them. • Record your observations. • Now keep the plant (that was earlier kept in dark) in sunlight for a few hours and perform the iodine test on its leaf again. Observation • The leaf of the plant kept in sunlight shows blue-black colour with iodine solution while the leaf of the plant kept in the dark does not show this colour change. This is because starch is made in the leaf kept in sunlight but not in the leaf kept in the dark. • When the plant kept in the dark was shifted to sunlight, the leaf showed blue‑black colour with iodine solution confirming the presence of starch. Result Sunlight is necessary for photosynthesis and leaves make food in the form of starch.

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Science–7

Sun

Small beaker Green leaf Spirit Water

Potted plant (having green leaves)

Water bath (Big beaker)

Potted plant (having green leaves)

Burner

Plant kept in sunlight

Plant kept in dark

Leaves boiled in spirit

Dropper

Dropper

No blue-black colour produced (No starch present)

Blue-black colour produced (Starch present) Leaf from plant kept in sunlight

Leaf from plant kept in dark

Sunlight is necessary for photosynthesis

1.3 Heterotrophic Nutrition and its Types Based on the method of obtaining food, heterotrophic plants are classified as: parasitic, insectivorous, saprotrophic and symbiotic. Parasites are the organisms that live in or on other living organisms (host) and obtain their nutrition from them. For example, cuscuta. Insectivorous plants like pitcher plant trap insects to meet their nitrogen requirement. They are green in colour. The pitcher like structure in pitcher plant is the modified part of leaf. The apex of the leaf forms a lid which can open and close the mouth of a pitcher. Inside the pitcher, there are hair which are directed downwards. When an insect lands in the pitcher, the lid closes and the trapped insect gets entangled in the hair. The insect is digested by the digestive juices secreted in the pitcher. Saprotrophs are the organisms that derive their nutrition from dead and decaying organic matter. Eg fungi like bread mould, mushroom. Saprotrophs secrete digestive juices on the dead and decaying matter and convert it into a solution. They, then absorb nutrients from it.

Nutrition in Plants 13

Pitcher plant (insectivorous) showing lid and pitcher

Symbiosis is an association where two organisms live together and share shelter and nutrients. For example, 1. Lichens are a symbiotic association between an alga and a fungus. The alga provides food to the fungus that it prepares by photosynthesis while the fungus provides shelter, water and minerals to the alga. 2. Rhizobium lives in the root nodules of leguminous plants. It receives shelter and nutrition from the plant and in return it converts nitrogen from the atmosphere into soluble form and provides it to the plant.

Exercise 1.3 I. Very Short Answer Type Questions (1 Mark) 1. Fill in the blanks: (a) _________________ is an insectivorous plant. (b) Bacteria called _________________ fix nitrogen for leguminous plants. (c) _________________ associations are always give and take type of relations. (d) _________________ element is fixed by Rhizobium. (e) _________________ is the non – photosynthetic part of the lichen. (f ) Saprophytes are _________________ in colour. (g) Some _________________ plants are also heterotrophic in nature.

II. Short Answer Type Questions-I (2 Marks)

2. Pitcher plant and Venus flytrap are green plants that photosynthesize. Why do they trap insects? 3. Explain symbiosis in lichens.

III. Short Answer Type Questions-II (3 Marks)

4. How does an insectivorous plant absorb nutrients from the insect trapped by it? 5. Why are nitrogenous fertilizers not added to soil in which leguminous plants are grown?

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Science–7

6. What are saprotrophs? How does a saprotroph digest its food? 7. How would you test the presence of starch in leaves? 8. Distinguish between a parasite and a saprotroph. 9. Give a brief description of photosynthesis in green plants. 10. Show with the help of a sketch that plants are the ultimate source

(NCERT) (NCERT) (NCERT) of food. (NCERT) 11. Potato and ginger are both underground parts that store food. Where is food prepared in these plants? (NCERT Exemplar) 12. Wheat dough left in the open, after a few days, starts to emit a foul smell and becomes unfit for use. Give reason. (NCERT Exemplar) 13. Nitrogen is essential for plant growth. But farmers who cultivate pulses do not apply nitrogenous fertilizers during cultivation. Why? (NCERT Exemplar)

Answers

1. (a) Pitcher plant (b) Rhizobium. (c) Symbiotic (d) Nitrogen (e) Fungus (f ) non-green (g) green 2. Insectivorous plants like pitcher plant, Venus flytrap trap insects to meet their nitrogen requirement as they grow in soil that lacks nitrogen. 3. Lichens are a symbiotic association between an alga and a fungus. The alga provides food to the fungus that it prepares by photosynthesis while the fungus provides shelter, water and minerals to the alga. 4. Insectivorous plants like pitcher plant trap insects. The pitcher-like structure in pitcher plant is the modified part of leaf. The apex of the leaf forms a lid which can open and close the mouth of pitcher. Inside the pitcher, there are hair which are directed downwards. When an insect lands in the pitcher, the lid closes and the trapped insect gets entangled in the hair. The insect is digested by the digestive juices secreted in the pitcher. 5. Rhizobium, a bacterium that can fix atmospheric nitrogen, lives in the root nodules of leguminous plants. It receives shelter and nutrition from the plant and in return it converts nitrogen from the atmosphere into soluble form and provides it to the plant. So, nitrogenous fertilizers are not added

to soil in which leguminous plants are grown. 6. Saprotrophs are the organisms that derive their nutrition from dead and decaying organic matter. For example, fungi like bread mould, mushroom. Saprotrophs secrete digestive juices on the dead and decaying matter and convert it into a solution. They, then absorb nutrients from it. 7. The presence of starch in leaves can be tested by Iodine test. When we remove chlorophyll from leaf by boiling it in alcohol and then put 2 drops of iodine solution, its colour changes to blue and indicates the presence of starch. 8.

Parasite

Saprotrophs

(i) Parasite feeds (i) They feed on a living on dead and organism. decaying organism. (ii) The organism (ii) They do not on which feed on a living it feeds is organism. called host. ( iii) A parasite takes readymade food from the organism on which it feeds.

( iii) They secrete digestive juices on the matter they live and convert it into a solution and then absorb it.

Nutrition in Plants 15

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