LECTURE 3: LIFE PROCESSES: NUTRITION IN ANIMALS

CLASS X   |    SCIENCE    |    LIFE PROCESSES

      Notes prepared by Subhankar Karmakar

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SCIENCE: CLASS X: CBSE (CLASS NOTES)

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• CLASSIFICATION OF ANIMALS ON THE BASIS OF FOOD HABITS

All the animals can be divided into three groups on the basis of their food habits or eating habits. These are:

• 1. Herbivores
• 2. Carnivores
• 3. Omnivores

• HERBIVORES
• Animals which eat only plants are called herbivores. 
• They are also called Herbivorous animals. 
• Some of the examples are goat cow buffalo horse etc. 

• CARNIVORES
• Those animals which eat only other animals as food are called Carnivores. 
• They eat only the flesh or meat of other animals.
• They are meat eaters.
• They are also called Carnivorous animals. 

• OMNIVORES
• Those animals which eat both, plants and animals, are called omnivores.
• They are also called omnivorous animals.
• Omnivores are plant eaters as well as meet eaters. 
• Human beings,  dog, are omnivorous animals.

Ultimately it is the energy of the Sun which provides food for plants and animals (herbivores, carnivores and omnivores).

• DIFFERENT STEPS IN THE PROCESS OF NUTRITION IN ANIMALS

There are five main processes concerned with the use of food by animals. They are as follows. 

• 1. Ingestion
• 2. Digestion
• 3. Absorption
• 4. Assimilation
• 5. Egestion
• INGESTION

The process of taking food into the body is called ingestion. When we put food into our mouth with hands we are ingesting. 

• DIGESTION

The process in which the food containing large, insoluble molecules is broken down into small, water soluble molecules, which can be absorbed by the body is called digestion. Most animals use both physical like chewing, grinding in mouth and chemical methods like breaking the large molecules using digestive juices like enzymes for digesting. 

• ABSORPTION

The process in which the digested food passes through the intestinal wall into blood stream is called absorption. 

• ASSIMILATION

The process in which the absorbed food is taken in by body cells and used for energy, growth and repair, is called assimilation. 

• EGESTION

A part of the food animals consume remain undigested as they are insoluble in water. The process in which the undigested food is removed from the body is called egestion. 

• NUTRITION IN UNICELLULAR ORGANISMS
• Amoeba is a unicellular organism. It eats microscopic animals and plants as food. The mode of nutrition in Amoeba is holozoic. 
• The process of obtaining food by Amoeba is called Phagocytosis. 
• It also follows the five steps processes for nutrition. 

• INGESTION IN AMOEBA

As Amoeba has no mouth or a fixed place for intake of food, Amoeba injests food by using its Pseudopodia, which is a temporary finger-like projections on the surface of the body. 

When a food particle comes near Amoeba, the food is engulfed with a little surrounding water to form a food vacuole inside the Amoeba. This food vacuole can be considered to be a "temporary stomach" of Amoeba. 

• DIGESTION IN AMOEBA

In Amoeba, food is digested in the food vacuole by digestive enzymes. The enzymes from surrounding cytoplasm enter into the food vacuole and breakdown the food into small and soluble molecules by chemical reactions. Therefore digestion in Amoeba takes place inside the food vacuole due to which the food become soluble.

• ABSORPTION IN AMOEBA

The digested food present in the food vacuole of amoeba is absorb directly into the cytoplasm of amoeba cell by diffusion. Since Amoeba consists of only one small cell it does not required blood system to carry the digested food. The digested food just spreads out from the food vacuole into the whole Amoeba cell. After absorption of food the food vacuole disappears.

• ASSIMILATION IN AMOEBA

A part of the food absorbed in Amoeba cell is used to obtain energy through respiration. The remaining part of absorbed food is used to make the parts of amoeba cell which lead to the growth of amoeba. Thus on assimilating food Amoeba grows in size and then Amoeba can reproduce by dividing into two daughter cells. 

• EGESTION IN AMOEBA

Amoeba has no fixed place for removing the undigested part of food. When a considerable amount of undigested food collected inside amoeba, then it cell membrane suddenly ruptures at any place and the undigested food is thrown out of the body of amoeba. 

• PARAMECIUM

Paramecium is also a tiny unicellular animal which lives in water. Paramecium uses its hair like structures called Cilia to sweep the food particles from water and put them into its mouth. 

Unlike amoeba paramecium has a mouth and it has cilia all over its body. When the cilia present around the mouth region of paramecium move back and forth, they sweep the food particles present in water into the mouse a paramecium. This is egestion for paramecium. 

LECTURE 2: CLASS 10 : LIFE PROCESSES : PHOTOSYNTHESIS - I

CLASS X   |    SCIENCE    |    LIFE PROCESSES

      Notes prepared by Subhankar Karmakar

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click to access other class notes

SCIENCE: CLASS X: CBSE (CLASS NOTES)

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• NUTRITION IN PLANTS
• The process by which green plants make their own food like glucose from carbon di oxide and water by using sunlight energy in the presence of chlorophyll is called photosynthesis.
• Chlorophyll is present in the green coloured bodies called chloroplasts inside the plant cells. 
• The leaves of a plant are green because they contain tiny green coloured organelles called Chloroplasts. 
• The process of photosynthesis
• The chemical reaction of the photosynthesis

6CO₂ + 6H₂O + Light energy (in the presence of chlorophyll) ⟹ C₆H₁₂O₆ + 6O₂

• PHOTOSYNTHESIS

Plants prepare their food (glucose) in the green leaves of the plant by combining carbon-di-oxide and water in the presence of sunlight and chlorophyll. The process is known as Photosynthesis.

• CHLOROPHYLL:

Chlorophyll is a green pigment found in the mesosomes of cyanobacteria and in the chloroplasts of algae and plants. It is needed for the process of photosynthesis.

• CARBON-DI-OXIDE

The plants derive carbon-di-oxide from the air by the plant leaves. Carbon-di-oxide enters the leaves through the small pores in them called stomata. 

• WATER

Water required for food preparation is taken from the soil through the roots. Water is transported to the leaves from the soil through the roots and stem. 

• SUNLIGHT

The sunlight provides the energy required to carry out the chemical reactions involved in the preparation of the food. The energy in the sunlight is absorbed with the help of chlorophyll. 

• Oxygen gas is produced as a by-product during the preparation of food by photosynthesis. This oxygen gas goes into the air. 
• The food prepared by the green leaves of a plant is in the form of a simple sugar called glucose. Glucose thus produced is sent to the different parts of the plant.
• The extra glucose is changed into another food called starch. This starch is stored in the leaves of the plant. Glucose and starch are called carbohydrates. 
• Green plants convert sunlight energy into chemical energy by making carbohydrates. 

• THE PHOTOSYNTHESIS PROCESS
• 1. Absorption of sunlight energy
• 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 utilising the chemical energy obtained by the transformation of light energy. 

• Conditions necessary for photosynthesis by green plants as well as autotrophic nutrition
• 1. Sunlight
• 2. Chlorophyll
• 3. Carbon dioxide
• 4. Water

A. Describe an experiment to show that Sunlight is necessary for photosynthesis

We know that green leaves make starch as food. As starch gives a black-blue colour with iodine solution. Plants store starch in their leaves. The green leaves of a plant are destarched by keeping this plant in a completely dark place in a room for atleast three days. 

• 1. We take a potted plant having Green leaves and place it in a completely dark place for about 3 days to destarch its leaves.
• 2. We take a thin strip of aluminium foil and wrap it in the centre of one leaf on both the sides. The covered part will not receive sunlight.
• 3. We keep this potted plant in bright sunshine for 3 to 4 days. 
• 4. We pluck the partially covered leaf from the plant and remove its Aluminium foil then immerse this leaf in boiling water for a few minutes. This will break down the cell membranes of leaf cells and make the leaf more permeable to iodine solution.
• 5. We put the plucked leaf in a beaker containing some alcohol. Place the beaker containing alcohol and leaf in a water bath and starts to heat it till the leaf becomes colourless. The boiling water will remove the chlorophyll from the green leaf. 
• 6. We remove the colourless leaf from alcohol, wash it in hot water and keep it in a petridish. We drop iodine solution on the leaf. 
• 7. The part which was wrapped in aluminium foil will not turn blue-black but rest of the parts of the leaf will become blue-black. 
• 8. Since the wrapped part didn't get sunlight, it did not produce starch. We can now conclude that 
• (i) sunlight is necessary for the process of photosynthesis.
• (ii) leaves make starch as food by photosynthesis.

• Variegated leaves:

The leaves which are partly green and partly white are called variegated leaves. The white part of the leaves doesn't contain chlorophyll. 

B. Describe an experiment to show that Chlorophyll is necessary for photosynthesis.

• 1. We take a potted plant having variegated leaves like a croton plant. The white part of the leaves doesn't contain chlorophyll whereas the green part contains chlorophyll. 
• 2. We place the plant in a completely dark place for about three days. 
• 3. We take out the plant and keep it under bright sun for 3 to 4 days 
• 4. We pluck the variegated leaf from the plant , boil it in water for few minutes, and then remove its green colour  chlorophyll by boiling in alcohol. The green part of the leaf  get decolourised.
• 5. We wash the decolourised leaf with hot water to soften and remove left-over Chlorophyll. 
• 6. We now pour iodine solution over the colourless leaf and observe the change in colour of the leaf. 
• 7. The inner part of leaf which was originally green turns blue black on adding iodine. 
• Chlorophyll is necessary for the process of photosynthesis to take place. 

C. Describe an experiment to show that Carbon Dioxide is necessary for photosynthesis.

• 1. We take a potted plant having narrow leaves and place it in a completely dark place for about three days to destarch its leaves. 
• 2. Take a glass bottle having a wide mouth and put some potassium hydroxide solution in it. 
• 3. Take a rubber cork which fits tightly into the mouth of the glass bottle and cut it into two halves. 
• 4. We put the destarched leaves in such a way, that upper half of the leaf should remain outside the glass bottle and only the lower half of the leaf should be inside the glass bottle.
• 5. The potted plant is kept in sunlight for 3 to 4 days. Upper half gets the carbon dioxide from air but lower half didn't get carbon dioxide as potassium hydroxide absorbed the carbon dioxide of the inside jar. 
• 6. We pluck the leaf and boiled it in alcohol then wash it with water.
• 7. We pour iodine solution over the colourless leaf. We observe that lower part of the leaf doesn't turned blue-black but the upper part became blue-black. 
• The photosynthesis to make starch in the leaf does not take place without carbon dioxide. 

Raw Materials for photosynthesis

The preparation of carbohydrates by plants by the process of photosynthesis requires two materials a. Carbon dioxide and b. Water

HOW THE PLANTS OBTAIN CARBON DIOXIDE

• STOMATA

There are large number of tiny pores called stomata on the surface of the leaves of plants. and green stem. The green plants take carbon dioxide from air for photosynthesis. The carbon dioxide gas enters the leaves of the plant through the stomata present on their surface. 

• STOMATAL PORES AND GUARD CELLS

STOMATAL PORES & GUARD CELL

• Each stomatal pore is surrounded by a pair of guard cells. The opening and closing of stomatal pore is controlled by the guard cells. 
• • When water flows into the guard cells, they swell, become curved and cause the pore to open. 
• • When guard cells lose water, they shrink, become straight and close the stomatal pore. 
• Plant losses water through the open stomatal pores hence when carbon dioxide is not needed by the plants, these pores are closed. 
• Oxygen gases produced during photosynthesis also goes out through the stomatal pores. 
• In most of the broad-leaved plants, stomata occur only on the lower surface of the leaf but in narrow-leaved plants, stomata are equally distributed on the both sides of the leaf. 
• Aquatic plants use the carbon dioxide gas dissolved in water for carrying out photosynthesis. 

HOW THE PLANTS OBTAIN WATER FOR PHOTOSYNTHESIS

• The water required by the plants for photosynthesis is absorbed by the roots of the plants from the soil through the process of osmosis. The water is absorbed by the roots of the plants is transported upward through the xylem vessels to the leaves. 
• Other nutrients like nitrogen, phosphorus, iron and magnesium etc. by the plants for its growth are taken by the plants from the soil through the roots of the plants. 

SITE OF PHOTOSYNTHESIS: CHLOROPLASTS

• Chloroplasts are the disc-like cell organelles of the photosynthetic cells of green plants which contain chlorophyll. At Chloroplasts photosynthesis take place. 
• The middle layer of the leaves are palisade layer and spongy layer and they contain photosynthetic cells which are called mesophyll cells. 
• Carbon dioxide enters through stomata and diffuses into the mesophyll cells and reaches the Chloroplasts. 
• Water is carried to the leaf by xylem and passes into the mesophyll cells by diffusion and reaches the Chloroplasts. 
• To reduce the water loss, there is a thin waxy protective layer called cuticle above and below a leaf.