CHAPTER 1. NUTRITION IN PLANTS NOTES Section Name Topic Name

[Pages:7]Class VII

Subject: Science(Biology)

Chapter 1: Nutrition in Plants

CHAPTER 1. NUTRITION IN PLANTS

NOTES

Section Name

Topic Name

1

Nutrition in Plants

1.1

MODE OF NUTRITION IN PLANTS

1.2

PHOTOSYNTHESIS -- FOOD MAKING PROCESS IN PLANTS

1.3

OTHER MODES OF NUTRITION IN PLANTS

1.4

SAPROTROPHS

1.5

HOW NUTRIENTS ARE REPLENISHED IN THE SOIL

Introduction

? All living organisms such as plants and animals require food. So, food is essential for all living organisms.

? Plants are capable of making their food themselves but humans and animals cannot. ? Carbohydrates, proteins, fats, vitamins and minerals are essential components of food, these components are

called nutrients.

MODE OF NUTRITION IN PLANTS

? Plants prepare their food by using raw materials like water, carbon dioxide and minerals. ? The process of utilization of food by a living organism to obtain energy is called nutrition. ? There are two modes of nutrition as shown below in the figure

1. Autotrophs or Autotrophic: - Plants that have chlorophyll trap the energy from the sun and prepare their own food. Such nutrition wherein the food is prepared by the organisms itself is called autotrophic nutrition. The organisms capable of preparing their own food are called autotrophs. All green plants are Autotrophs (Auto means self and trophos means nourishment). They prepare their own food by a process called photosynthesis.

2. Heterotrophs or heterotrophic: - Heterotrophic organisms are those who obtain food from other organisms. Since these organisms depend on other organisms for their food, they are called consumers. All animals and non-green plants like fungi come under this category. Organisms that follow the heterotrophic mode of nutrition are called heterotrophs.

Shayar Singh, PGT ? Biology.

Kendriya Vidyalaya, Khargone

Class VII

Subject: Science(Biology)

Chapter 1: Nutrition in Plants

PHOTOSYNTHESIS -- FOOD MAKING PROCESS IN PLANTS ? Photosynthesis is food making process in plants from simple substances like carbon dioxide and water in the

presence of sunlight.

? Oxygen is released during photosynthesis. The process of photosynthesis can be represented as:

Fig: Diagram showing photosynthesis ? The process of photosynthesis takes place in the green leaves of a plant. ? The food is prepared by the green leaves of a plant in the form of a simple sugar called glucose. ? The extra glucose is changed into another food called starch. This starch is stored in the leaves of the plant. ? The green plants convert sunlight energy into chemical energy by making carbohydrates.

The photosynthesis takes place in the following three steps: 1. Absorption of sunlight energy by chlorophyll. 2. Conversion of light energy into chemical energy, and splitting of water into hydrogen and oxygen by light

energy. 3. Reduction of carbon dioxide by hydrogen to form carbohydrate like glucose by utilizing the chemical energy. Conditions necessary for photosynthesis: The conditions necessary for photosynthesis to take place are:

1. Sunlight 2. Chlorophyll 3. Carbon dioxide 4. Water Raw materials for photosynthesis: The raw materials for photosynthesis are: 1. Carbon dioxide 2. Water How the plants obtain carbon dioxide?

? There are a large number of tiny pores called stomata on the surface of the leaves of plants.

Shayar Singh, PGT ? Biology.

Kendriya Vidyalaya, Khargone

Class VII

Subject: Science(Biology)

Chapter 1: Nutrition in Plants

? The carbon dioxide gas enters the leaves of the plant through the stomata present on their surface. ? Each stomatal pore is surrounded by a pair of guard cells. The opening and closing of stomatal pores is

controlled by the guard cells. How the plants obtain water for photosynthesis: ? The water required by the plants for photosynthesis is absorbed by the root of the plants from the soil through

the process of osmosis. ? The water absorbed by the roots of the plants is transported upward through the xylem vessels to the leaves

where it reaches the photosynthetic cells. 1. The plants also need other raw materials such as nitrogen, phosphorus, iron and magnesium, etc., for building

their body. 2. The plants take these materials from the soil. 3. Nitrogen is essential element used by the plants to make proteins and other compound. Site of photosynthesis: Chloroplasts ? Photosynthesis takes place in the leaves of the plants. ? Leaves have green pigment called chlorophyll ? It helps leaves capture the energy of the sunlight which is then used to prepare food from carbon di oxide and

water. ? Here, you see that solar energy is captured by the leaves and is stored in the plant in the form of food. ? So, we can say that Sun is ultimate source of energy for all living organisms.

Extra Notes on photosynthesis ? Photosynthesis in plants can also takes place in other green parts like green stems, green branches. ? Glucose (simple carbohydrates) is the simplest food synthesized by plants. This glucose made by plants is

converted into complex carbohydrates which are known as starch. ? These simple carbohydrates are used to synthesise other components of food such as proteins and fats. ? Proteins are nitrogenous substances. Plants prepare proteins with the help of nitrogen which is obtained from

the soil. ? Plants use the minerals dissolved in water to convert Glucose (simple carbohydrates) into carbohydrates,

proteins and fats. ? Photosynthesis is important because: 1. It provides food to animals including human beings 2. It puts oxygen gas into the air which is essential for breathing and respiration in animals including human

beings

OTHER MODES OF NUTRITION IN PLANTS

Heterotrophic Nutrition ? Most of the plants have green pigment called chlorophyll and can make their own food. ? Some plants do not have chlorophyll and cannot synthesize their own food and are known as Heterotrophic

plants ? This type of nutrition can be categorized into

1. Parasitic mode of nutrition 2. Insectivorous mode 3. saprophytic mode of nutrition 4. Symbiotic mode of nutrition

Parasites ? In parasitic mode of nutrition, plants depend on other plants or animals for their nourishment. ? Such dependent plants are called as parasites and the ones on which parasites depend are called as hosts. ? A parasite plant climbs on the host plant from which they get all the food. ? The host does not get any benefit from the parasite. ? Some examples of parasites are Cuscuta (akash-bel), Cassytha (amar-bel), hookworms, tapeworms, leeches,

etc.

Shayar Singh, PGT ? Biology.

Fig: Cuscuta Plant Kendriya Vidyalaya, Khargone

Class VII

Subject: Science(Biology)

Chapter 1: Nutrition in Plants

Extra Notes ? Cuscuta (dodder) is a plant that does not have chlorophyll; it sucks food from the host plant through

adventitious roots called haustoria, Cuscuta is therefore a complete parasite. ? Mistletoe plant has green leaves and so can carry out photosynthesis. This plant mainly absorbs water and

minerals from the host plant. Therefore, Mistletoe is called a partial parasitic plant. ? Rafflesia is a parasite of the Tetrastigma plant. It is completely dependent on its host plant for food.

Insectivorous Plants ? The insectivorous mode of nutrition is observed in plants like pitcher plant and the Venus fly trap. ? These types of plants purely depend on other insects and small animals for their nutrition. ? Pitcher plants trap small insects inside the pitcher and insects are digested by the digestive juices secreted

in the pitcher. ? Insectivorous plants grow in those soils which do not contain sufficient nitrogen mineral. ? These types of plants are green and carry out photosynthesis to obtain a part of food.

Extra Notes The leaves of the Venus flytrap have stiff hair like projections on their edges and the entire leaf is divided into two parts, with the middle acting as a hinge. When an insect sits on the leaf, it shuts tightly, trapping the insect inside it. ? The Pitcher plant has a pitcher- shaped structure filled with liquid. it has a flap -like structure on its mouth.

The edge of the opening of the pitcher is slippery. The insect that sits on its slips and falls into the pitcher, getting trapped inside with the closing of the lid. ? The sundew plant has long needle like structures called tentacles covered with sticky substance called mucous. Once an insect sits on it, it gets caught in the mucous and the tentacles fold inward, trapping the insect.

Fig: Insectivores Plant

SAPROTROPHS

? Mode of nutrition in which organisms or plants that obtain their nutrition from dead and decaying organic matter is called Saprophytic mode

? The plants which exhibit saprotrophic mode of nutrition are called as saprotrophs ? Saprotrophs secrete digestive juices onto dead and decaying matter to dissolve it and then absorb nutrients from

it. ? Examples of saprotrophs are moulds, mushrooms, yeasts and some bacteria.

Shayar Singh, PGT ? Biology.

Figure 10: Fungi growing on Bread Kendriya Vidyalaya, Khargone

Class VII

Subject: Science(Biology)

Chapter 1: Nutrition in Plants

Symbiotic plants ? In this mode of nutrition there is a close association between two different plants of different categories. ? In such type of association both the plants get benefited. ? For example, certain fungi live in the roots of the trees. In this case tree provides nutrients to fungi and in return

receives help from it to take up water and nutrients from the soil.

HOW NUTRIENTS ARE REPLENISHED IN THE SOIL

? We know that plants continuously take nutrients from the soil in order to synthesize food. As a result of this amount of nutrients in the soil decreases.

? Nutrients in the soil are replenished by adding fertilisers and manures. ? Fertilisers and manures contain plants nutrients and minerals like nitrogen, phosphorus and potassium. ? Another way to replenish soil is to grow leguminous crops (for example gram, peas, pulses etc.) in the soil. ? The bacterium called Rhizobium can take atmospheric nitrogen and convert it into a soluble form. ? But Rhizobium cannot make its own food. So it lives in the roots of gram, peas, moong, beans and other legumes

and provides them with nitrogen. In return plants provide food and shelter to the bacteria. ? Thus, plants and bacteria have a symbiotic relationship here.

NCERT SOLUTIONS

Question 1: Why do organisms take food?

ANSWER: All living organisms require food to survive. It gives them energy to perform various activities. All

activities such as playing, running, walking, studying, etc. require energy. The various components present in our

food such as carbohydrates, proteins, fats, vitamins, and minerals provide energy to our body. These are also

important for growth and development of the body.

Question 2: Distinguish between a parasite and a saprotroph.

ANSWER:

Parasite

Saprotroph

The organism that grows on the body of another The organism that obtains nutrients from the dead

organism and derives nutrients from it is known as a or decaying organic matter is called saprotroph.

parasite.

Examples of parasites are Cuscuta and orchids.

Examples of saprotrophs are fungi and some

bacteria.

Question 3: How would you test the presence of starch in leaves?

ANSWER: Experiment to test the presence of starch in leaves:

Take two healthy green potted plants of the same type. Keep one potted plant in a dark room for one or two days

in order to remove all the starch from the leaves. Keep the other plant in sunlight. Now, take one leaf from each

potted plant and put a few drops of iodine solution on them. Then note down the observation.

Plants kept in light and dark conditions No blue-black colour will be observed on the leaves of the plant kept in the dark room. This indicates the absence of starch. Blue black colour will be observed on the leaves of the plant kept in sunlight. This indicates the presence of starch.

Shayar Singh, PGT ? Biology.

Kendriya Vidyalaya, Khargone

Class VII

Subject: Science(Biology)

Chapter 1: Nutrition in Plants

Question 4: Give a brief description of the process of synthesis of food in green plants. ANSWER: Photosynthesis is defined as the process in which the chlorophyll-containing plant cells synthesise food in the form of carbohydrates, using carbon dioxide and water in the presence of solar energy.

Photosynthesis Sources of raw materials required for photosynthesis: (a) Water is taken in from the roots of the plant and is transported to the leaves. (b) Carbon dioxide from the air enters the leaves through the tiny pores called stomata and diffuses to the cells containing chlorophyll. (c) Solar energy is used to break water into hydrogen and oxygen. This hydrogen is combined with carbon dioxide to form food for the plants, which is ultimately used by the animals as well. Thus, photosynthesis can be represented by the following equation.

Question 5: Show with the help of a sketch that the plants are the ultimate source of food. ANSWER:

Photosynthesis Question 6: Fill in the blanks: (a) Green plants are called __________ since they synthesise their own food. (b) The food synthesised by plants is stored as __________. (c) In photosynthesis solar energy is absorbed by the pigment called ___________. (d) During photosynthesis plants take in ___________and release ___________ gas. ANSWER: (a) Green plants are called __autotrophs__ since they synthesise their own food. (b) The food synthesised by the plants is stored as __starch__. (c) In photosynthesis solar energy is absorbed by the pigment called chlorophyll__. (d) During photosynthesis plants take in __carbon dioxide__ and release __oxygen__ gas. Question 7: Name the following: (i) A parasitic plant with yellow, slender and branched stem. (ii) A plant that is partially autotrophic. (iii) The pores through which leaves exchange gases. ANSWER: (i) Cuscuta, (ii) Pitcher plant, (iii) Stomata Question 8: Tick the correct answer: (a) Cuscuta is an example of:

Shayar Singh, PGT ? Biology.

Kendriya Vidyalaya, Khargone

Class VII

Subject: Science(Biology)

Chapter 1: Nutrition in Plants

(i) autotroph

(ii) parasite

(iii) saprotroph

(iv) host

(b) The plant which traps and feeds on insects is:

(i) Cuscuta

(ii) china rose

(iii) pitcher plant

(iv) rose

ANSWER: (a) (ii) parasite, (b) (iii) pitcher plant

Question 9: Match the items given in Column I with those in Column II:

Column I Column II

Chlorophyll Rhizobium

Nitrogen Heterotrophs

Cuscuta

Pitcher plant

Animals

Leaf

Insects

Parasite

ANSWER:

Column I Column II

Chlorophyll Leaf

Nitrogen Rhizobium

Cuscuta

Parasite

Animals

Heterotrophs

Insects

Pitcher plant

Question 10: Mark `T' if the statement is true and `F' if it is false:

(i) Carbon dioxide is released during photosynthesis. (T/F)

(ii) Plants which synthesise their food are called saprotrophs. (T/F)

(iii) The product of photosynthesis is not a protein. (T/F)

(iv) Solar energy is converted into chemical energy during photosynthesis. (T/F)

ANSWER: (i) Carbon dioxide is released during photosynthesis. (F)

(ii) Plants which synthesise their food are called saprotrophs. (F)

(iii) The product of photosynthesis is not a protein. (T)

(iv) Solar energy is converted into chemical energy during photosynthesis. (T)

Question 11: Choose the correct option from the following:

Which part of the plant takes in carbon dioxide from the air for photosynthesis?

(i) Root hair

(ii) Stomata

(iii) Leaf veins

(iv) Petals

ANSWER:

(ii) Stomata

Question 12: Choose the correct option from the following:

Plants take carbon dioxide from the atmosphere mainly through their:

(i) roots

(ii) stem

(iii) flowers

(iv) leaves

ANSWER:

(iv) leaves

Question 13: Why do farmers grow many fruits and vegetable crops inside large green houses? What are

the advantages to the farmers?

ANSWER: Greenhouses allow farmers to regulate the climate and other conditions for the proper growth of

crops. Growing fruits and vegetables in large green houses provide following advantages to the farmers:

1. It allows them to provide optimum temperature to plants.

2.It helps in the protection of plants from rodents.

Shayar Singh, PGT ? Biology.

Kendriya Vidyalaya, Khargone

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