Monday, July 25, 2011

CBSE NCERT Class 7 Science Nutrition in Plants

Nutrition in Plants

Fill in the blanks:
(a) Green plants are called _       autotrophs __ since they synthesize their own food.
(b) The foods synthesized by the plants are stored as starch .
(c) In photosynthesis solar energy is captured by the pigment called ___ chlorophyll
(d) During photosynthesis plants take in ____CO2________ and release _ O2
Name the following:
(i) A parasitic plant with yellow, slender, tubular stem.-------  Cascuta
(ii) A plant that has both autotrophic and heterotrophic mode of nutrition.---------  Insectivorous plants
(iii) The pores through which leaves exchange gases. ------- Stomata
(iv)  A plant that has both autotrophic as well as heterotrophic mode of nutrition. --- Pitcher plant.
(v)  An organism that live is an association of an alga and a fungus   ---------- lichen
(vi)  Amarbel is an example of: ----parasites  

(vii) The plant which traps and feeds on insects is----- pitcher plant

Match the items in column I with those in column II:
Chlorophyll ---–       Leaf.
Nitrogen   –––         Bacteria.
 Amarbel   –––      Parasite.
Animals   –––       Heterotrophs.
Insects  –––       Pitcher Plant

What is Nutrients?

Food is essential for all living organisms. Carbohydrates, proteins, fats, vitamins and minerals are components of food. The chemical substance present in components of food is necessary for our body and is called nutrients.

How humans and animals are are directly or indirectly dependent on plants.

All living organisms require food. Plants can make their food themselves but animals including humans cannot. They get it from plants or animals that eat plants. Thus, humans and animals
are directly or indirectly dependent on plants.

Why do we need food ?

Living organisms need food  to build their bodies, to grow, to repair damaged parts of their bodies and provide the energy to carry out life processes.

What is food ?

Food is the source of energy and every cell of an organism gets energy by the breakdown of glucose. The cells use this energy to carry out vital activities of life.

What is Nutrition?

Nutrition is the sum of all including taking food by an organism and its utilization by the body.

The mode of  nutrition in which organisms make food  themselves from simple substances is
called autotrophic nutrition. Ex plants.
The mode of nutrition in which organisms take in ready made food prepared by the plants
called heterotrophic nutrition. Ex animals

Whether food is made in all parts of a plant or only in certain parts?

Only certain part plant like leaves having green pigment chlorophyll. so Leaves are called  the food factories of plants.
Besides leaves, photosynthesis also takes place in other green parts of the plant — in green stems and green branches. The desert plants have scale- or spine-like leaves to reduce loss of water by transpiration. These plants have green stems which carry out photosynthesis.

How do plants obtain the raw materials from the surroundings?

Water and minerals present in the soil are absorbed by the roots and transported to the leaves.
Carbon dioxide from air is taken in through the tiny pores present on the surface of the leaves. Such pores are called stomata. These pores are surrounded by ‘guard cells’

How do the raw materials transport them to the food factories of the plants?

Plants have pipe-like vessels to transport water and nutrients from the soil. The vessels are
made of special cells, forming the vascular tissue. The vascular tissue for the transport of water and nutrients in the plant is called the xylem. The vascular tissue for the transport of water and nutrients in the plant is called the xylem. Thus, xylem and phloem transport substances in plants

What is cell ?

The bodies of living organisms are made of tiny units called cells therefore Cell are called the building blocks of living organism.

Cells can be seen only under the microscope. Some organisms are made of only one cell. They are called Unicellular Ex. Amoeba, Paramecium etc
Living organism made up of many cells are called Multi cellular like man, tree etc

What is the cell membrane?
The cell is enclosed by a thin outer boundary, called the cell membrane Most cells have a distinct, centrally located spherical structure called the nucleus  The nucleus is surrounded by a jelly-like substance called cytoplasm.

What is tissue ?

A tissue is a group of cells that perform specialized function in an organism. For example, the vascular tissue for the transport of water and nutrients in the plant is called the xylem.

What are the main requirements of photo synthesis?

Chlorophyll, sunlight, carbon dioxide and water are necessary to carry out the process of

Explain the process of Photosynthesis?

Carbon dioxide from air is taken in through stomata. chlorophyll helps leaves to capture the energy of the sunlight. This energy is used to synthesize (prepare) food from carbon dioxide and water. Since the synthesis of food occurs in the presence of sunlight, it is called photosynthesis

Carbon dioxide +  water ---------sunlight/chlorophyll--àCarbohydrate  +    oxygen
Here the carbohydrates ultimately get converted into starch

How would you test the presence of starch on leaves?

Put 2-3 drops of dilute iodine solution on the leaves. Appearance of a blue-black colour indicates presence of starch in the leaves.

Why are leaves called the food factories of plants? Explain.

Leaves are called the food factories of plants due to following functions
ü  Green leaves have all the raw materials neccessary to carry the process of photosynthesis. 
ü  They have chlorophyll (green pigment) which captures the energy of sunlight. 
ü  Leaves consist of tiny pores called stomata on their surface. 
ü  Carbon dioxide from air is taken in through stomata. 
ü  Water and minerals are absorbed by the roots from the soil and transported to the leaves by vessels.
    Why sun is called the ultimate source of energy for all living organisms?

The solar energy is captured by the leaves and stored in the plant in the form of food. and this in turn use by other organism to get food to obtain energy Thus, sun is the ultimate source of energy for all living organisms.

Why algae are green in colour?

Algae contain chlorophyll which gives them the green colour. It can also prepare their own food by photosynthesis.

What are the main components presents in carbohydrates?
The main components presents in carbohydrates are carbon, hydrogen and oxygen.

From where do the plants obtain nitrogen?

Soil has certain bacteria  that convert gaseous nitrogen into a usable form and release it into the soil. These soluble forms are absorbed by the plants along with water.

By adding fertilizers rich in nitrogen to the soil farmers also made nitrogen available for plants

What is parasitic nutrition?

The mode of by which parasitic organism get and synthesize their food is called parasitic nutrition. Example Cucuta It does not have chlorophyll It takes readymade food from the plant
on which it is climbing. The plant on which it climbs is called a host.

How Pitcher plants get their nutrition?

There are a few plants which can trap insects and digest them. Such plants may be green or of some other colour. Such insect-eating plants are called insectivorous plants.
Example Pitcher plant
When an insect lands in the pitcher, the lid closes and the trapped insect gets entangled into the hair. The insect is digested by the digestive juices secreted in the pitcher.

Why does the pitcher plant feed on insects though it is green? 

The pitcher plant does not get all the required nutrients especially those of nitrogen from the soil, hence it feeds on insects.

What is saprotrophic nutrition? What is the mode of nutrition in fungi?
This mode of nutrition in which organisms take in nutrients in solution form from dead and decaying matter is called saprotrophic nutrition. Plants which use saprotrophic mode of
nutrition are called saprotrophs. Example Fungi that secrete digestive juices on the dead
and decaying matter and convert it into a solution. Then they absorb the nutrients from it.

How do fungi appear suddenly during the rainy season?

Air generally consists of fungal spores. When these spores come in contact with warm things they germinate and grow. During rainy season, there are more chances of things getting wet.
Hence, fungi appear more in rainy season.

What do you under stand by symbiotic relationship present in some organism?

Some organisms live together and share shelter and nutrients. This is called symbiotic relationship . E.g. an alga, and a fungus live together fungus provides shelter, water and
Minerals to the alga and, in return, the alga provides food which it prepares by photosynthesis.

What is Symbiosis?
Symbiosis - It is the type of nutrition in which two different kinds of depend on each other for their nutrition. In this both the organisms are benefitted by each other e.g., lichen. In this one alga and one fungus live together and remain in symbiotic relationship.

How nutrients are replenished in soil?
Nutrients are replenished in soil by following ways
1.By  spreading manure or fertilizers that contain nutrients such as nitrogen in the fields
2.By  The bacterium Rhizobium that can take atmospheric nitrogen and convert it into a soluble form.

How do leguminous plants help replenishing soil fertility?

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, the plants provide food and
shelter to the bacteria

Distinguish between a parasite and a saprotrophs
1. A parasite takes readymade food from the organism on which it feeds.
2. They feed on a living organism.
3. The organism on which it feeds is called host.
4. It deprives the host of valuable nutrients.

1. They secrete the digestive juices on the matter they live and convert it into a solution and then absorb it.
2. They feed on dead and decaying organism.
3. They do not feed on a living organism.
4. There is no host at all.

Why algae are green in colour?

Algae are green in colour as they contain chlorophyll which gives them the green colour. Algae can also prepare their own food by photosynthesis. Slimy, green patches in ponds or in other stagnant water  bodies are algae.

Activity 1
Aim: To prove the essentiality of green colour pigment chlorophyll for photosynthesis.
Procedure: Following steps are performed in a sequential order.
Step-1: Take a beaker with boiling water and drop a leaf into it. Let it boil for 2 minutes.
Step-2: Take the leaf out of the beaker and place it in a test tube with alcohol. Place this test tube in a hot water bath for 10 minutes. Alcohol decolourises the leaf by removing chlorophyll from it by the process of bleaching.
Step-3: Remove the leaf from alcohol and wash it with warm water. Place it on a tile for further test.
Step-4: Add 2 drops of iodine on to the leaf. The portions which contained chlorophyll turn into bluish-black colour. The portions which did not contain chlorophyll and did not participate in photosynthesis remain the same.
Inference: From the experiment we can infer that green parts of the leaves synthesised starch and non-green parts did not perform photosynthesis to form starch.
Activity 2
Aim: To explain the essentiality of light in photosynthesis
Procedure: Following steps are performed in a sequential order.
Step-1: A leaf is selected on a plant and is covered with black paper.
Step-2: Plant is destarched by keeping it in atmost darkness for 3 days. Pick a leaf and test it to 
confirm that the plant is starch free. i.e. It did not perform photosynthesis in the darkness.
Step-3: Expose the same plant to sunlight for a day.
Step-4: Test the leaf covered with black paper using iodine. It does not turn blue-black as it has not synthesised starch. Starch synthesis did not happen as it is not exposed to sunlight.
Inference: Photosynthesis did not occur in the leaf covered with black paper confirming the essentiality of light for the synthesis of starch.
Activity 3
Aim: To prove the requirement of carbon dioxide for photosynthesis
Procedure: Following steps are performed in a sequential order.
Step-1: A potted plant is taken and placed in complete darkness for few hours.
Step-2: Take potassium hydroxide in a conical flask rubber stoppered with a cork. Insert one leaf ( still attached to parent plant) into through a hole in the rubber cork. Potassium hydroxide absorbs all the left-over carbon dioxide from the flask.
Step-3: Entire arrangement is exposed to sunlight for 6 hours.
Step-4: The leaf placed in the conical flask with potassium hydroxide solution is tested with iodine solution. This does not turn into bluish-black colour.
Inference: The leaf trapped inside the conical flask did not perform photosynthesis as it did not receive any carbon dioxide.



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