GREENWOOD PUBLIC SCHOOL, ADITYAPURAMOUR MOTTO-DEVELOPMENT WITH DELIGHT

CLASS-VII SUBJECT- SCIENCE

Chapter-1 Nutrition in plants

Difficult words:-

Nutrients Heterotrophic Chlorophyll Autotrophs Photosynthesis Parasites Saprophytes Insectivorous Symbiotic Rhizobium Stomata Carbon dioxide Manufacture Decaying Environment

Glossary:-

Nutrition : The process of food and its utilization by the organisms.

Autotrophs : Organisms that can produce their own food.

Heterotrophs : Plants and animals that do not make their food and depend on ready-made food.

Parasite : An organism that lives on the body of other organisms tor food and shelter

Saprophyte : Any plant or microorganism living on dead or decaying organic matter

Symbiosis : The mode of nutrition where two organisms live together for mutual benefit.

Notes-

Necessity of food in living organisms:-

Living organisms require to carry out basic processes such as reproduction,growth, nutrition, respiration,etc.to maintain life .for carrying out all life processes each living organism need daily supply of energy which is provided by the food consumed by them.The food contains substances that provide nourishment to the body are called NUTRIENTS.

Nutrition:-

The process of providing or obtaining the food necessary for health and growth is known as nutrition

There are two modes of nutrition in living organisms Autotrophic nutrition and Heterotrophic nutrition

1. Autotrophic Nutrition:- the word Auto means self and trophos means

nourishment.Autotrophic plants make their own food by the process

known as photosynthesis

2. Heterotrophic Nutrition:- the word heteros means other and trophos

means nutrition. Heterotrophic organism obtain their food from the

bodies of other organisms.

Autotrophic Mode Of Nutrition:-

Green plants can make their own food these self dependent living things are known as autotrophs the process by which they can produce their own food and energy using sunlight and water is known as photosynthesis.

Materials Required for Photosynthesis:-

a. Water and mineral

b. Carbondioxide

c. Chlorophyll

d. Sunlight

Importance of Photosynthesis:-

It is the most important biological process on which all living organisms depend directly or indirectly for food

This process maintains the balance of carbon dioxide and oxygen in the environment

It provides us oxygen for breathing

Heterotrophic Mode Of Nutrition:-

There are some plants which do not contain chlorophyll and so they cannot prepare their own food they depend upon other plants or other organisms to obtain their nourishment. These plants are said to have heterotrophic mode of nutrition and are called heterotrophs. Heterotrophs have been classified into following categories:-

Parasites: - A parasite is a heterotroph that completely depends on another organism for its food.The organism to which the parasite latches onto is called the host.The host, in the process, is deprived of all nutrients for its own growth as they are consumed by the parasite.

For example, Cuscuta (Amarbel) is a nongreen plant that takes readymade food from the plant on which it is growing.

Saprophytes:- Organisms which rely on dead and decaying matter for their food are called Saprotrophs.This mode of nutrition is called saprotrophic nutrition.

For example, Fungi. (Fungi secrete digestive juices on the dead and decaying matter and convert it into a solution.Then they absorb the nutrients from it.)

Insectivorous Plants:- Plants that feed on insects are called Insectivorous plants.These plants are green and carry out photosynthesis.But they grow in nitrogen-deficient soils.So, in order to get nitrogen, they feed on

insects.These insectivorous plants have their parts modified for attracting and catching insects.

For example, The pitcher plant, Venous flytrap

Symbiotic Plants:- Organisms that live together and share their shelter and nutrients are said to be in a symbiotic relationship.Certain fungi live in the roots of trees.The tree provides nutrients to the fungus and, in return, receives help from it to take up water and nutrients from the soil.This association works well for both the fungi and the tree.Another most common example is of Rhizobium bacteria.They reside in the root nodules of leguminous plants.The bacteria provide a plant with nitrogen that they fix and in turn, they get shelter and food from the plant.

Nutrients Being Replenished in Soil:-

Plants absorb mineral nutrients from the soil in order to make their own food and for other important processes.Soils need to be enriched with nutrients such as nitrogen, phosphorus, potassium etc regularly.Only then can we grow plants and keep them healthy.There are 17 most important nutrients for plants.6 are called macronutrients and rest are called micronutrients.Macronutrients are required in large quantities while micronutrients are required in very small quantities.

Activity:-

Aim:-To prove that carbon dioxide is necessary for photosynthesis

Method:-Take a potted plant with long leaves and place it in the dark for 2-3 days to make it starch free.Take a leaf from this plant and insert half of it in a bottle containing caustic potash (KOH) through a split cork.Caustic potash absorbs carbon dioxide, hence the portion of the leaf in the bottle will not get carbon dioxide.The portion of the leaf outside the bottle will get carbon dioxide. Cork the bottle and place it in sunlight for a few hours.

Observation:-Test the leaf for starch. Make a note of the part of the leaf that turns blue-black.

Chapter-2

Nutrition in Animals

Difficult words:-

Holozoic s Parasites Carnivorous Ectoparasites Endoparasites Egestion Assimilation Absorption Digestion Pseudopodia Vacuole Alimentary Oesophagus Peristalsis Ruminants

Glossary:-

Herbivores : animals that depend upon plants for their food

Carnivores : animals that depend upon other animals for their food

Omnivores :animals that consume plants as well as animals

Scavengers : carnivorous animals which consume dead remains of animals killed by predators

Ruminant : animal that regurgitates and then masticates its food after swallowing

Peristalsis : contraction and expansion of the muscles of the oesophagus

Pseudopodia : fake feet of Amoeba which engulfs food

Notes:-

Heterotrophs:- Animals do not make their own food but depend on the food synthesised by plants. Hence they are called heterotrophs and they show heterotrophic mode of nutrition. when the food is taken in the form of solid particles as a whole the method of food intake is known as holozoic nutrition

Classification of Heterotrophs :-

Based on eating habits the heterotrophs are classified as follows:-

3. Herbivorous Animals:- These are the animals that obtain their food only from plants. example cow, sheep, goat, elephant, Kangaroo, giraffe, etc.

4. Carnivorous Animals:- These are the animals that obtain their food by killing other animals.They never eat plants or plant products.example Tiger, lizards, lion, etc.

5. Omnivorous Animals:- These are the animals that eat both plants as well as other animals for nutrition example bear, dog, human beings, etc.

6. Parasites:- these Organisms obtain their food from other animals either by living inside or outside the body example tapeworm and round worm.

7. There are two types of parasites:- 8. endoparasite:- parasite which obtains its food from the human body by

living inside the body. Example-mosquitos 9. ectoparasites:- parasite which sucks the blood of the human body or cattle

from outside the body.Example- leech 10. Scavengers:- Scavengers are those animals that feed on the remains

of dead animals preyed on by Predators example vulture, crows, jackal, etc.

Process of Nutrition:-

There are 5 steps in the process of Nutrition:-

Ingestion: -The process of taking food into the body is called ingestion. Digestion:- The breakdown of complex components of food into simpler

substances is called digestion.Partial digestion takes place in the stomach and complete digestion takes place in the intestine.

Absorption:- It is the processin which simple soluble digested food is absorbed by the body Fluids of living organism

Assimilation:- The substances that are absorbed are transported through blood vessels to various organs of the body where it is utilized to build complex substances like proteins essential for the body. This is called assimilation.

Egestion:- It is the process in which the undigestedand unabsorbed food is thrown out from the body.

Nutrition in Amoeba:-

Amoeba is single-celled organism, microscopic in nature found in pond water. Amoeba regularly changes its shape and position.

Process of Digestion in Amoeba:-

a. Amoeba captures the food particles with the help of pseudopodia. The process is called as phagocytosis.

b. A food vacuole is thus created with the food material inside.

c. Digestive juices are produced into the food vacuole when it is moving through the cytoplasm.

d. They act on the food and disintegrate it down into simpler substances and the digested food is then absorbed.

e. Finally, the food vacuole opens to the outside and undigested food is released into surrounding water.

Process of Nutrition in Human Beings:-The digestive tract and the associated glands together constitute the digestive system in humans.This constitutes the whole path along which food moves through the body, starting from the mouth and ending at the anus.Digestive tract includes the oesophagus, stomach, small

intestine and large intestine.Salivary glands, liver and pancreas are the major digestive glands.

I. Buccal Cavity:-The buccal cavity is more commonly known as the mouth, and it is the beginning of the digestive system for humans.It consists of the tongue and teeth.

Teeth: Helps in chewing food and breaking down food into smaller particleTooth Decay:-Bacteria present in mouth break down the sugars present from the leftover food and release acid.These acids gradually damage the teeth and results in tooth decay.

Tongue: Fleshy muscular organ attached at the back to the floor of the buccal cavity.It helps in mixing saliva with food while chewing and aids in swallowing.The tongue possesses tastes buds that help us recognise different tastes.

Saliva:Three pairs of salivary glands are present around the mouth and they pour their secretion, saliva, into the mouth by salivary ducts.Saliva has mucous and salivary amylase.Mucous helps in easy passage of food through the food pipe.Salivary amylase is an enzyme responsible for breaking of starch content of food into simpler sugars.

II. Oesophagus:- The food that is swallowed, passes into the oesophagus.It is a muscular tube, about 25 cm long, with a sphincter (valve/opening) at each end.Its function is to transport food and fluid, after being swallowed, from the mouth to the stomach.Food is propelled down by as there in movement through the walls of the food pipe.

III. Stomach:-It is a thick-walled bag-like structure.It obtains food from the food pipe and opens into thesmall intestine towards the other opening.The inner

lining of the stomach produces mucus, hydrochloric acid(HCl)and other digestive juices.Food is churned into semi-solid mass in the stomach.Enzymes present in the gastric juice disintegrate the food.Hydrochloric acid helps in partial digestion of proteins and also kills harmful bacteria.

IV. Small Intestine:-This is a highly coiled organ of 7.5 metres length.It receives secretion from the liver and pancreas.Complete digestion and absorption of food take place in the small intestine.The inner walls of the intestine have finger-like outgrowth called villi.Villi increase the surface area for absorption of food.Each villus has a small network of blood vessels.Absorbed food by villi is transferred to the body via blood vessels.

V. Large intestine:- It is wider and shorter than the small intestine.It is 1.5m in length.Absorption of water and salt from undigested food occurs in the large intestine.Remaining waste matter is passed out through the rectum.Time to time, faecal matter is removed through the anus (egestion).

Ruminants:-

Rumination is the process by which the cattle regurgitates previously consumed feed and masticates it a second time.and the animals are called ruminants. The stomach of a ruminant has four chambers.

Rumen:- This is the first chamber and is very large. The food reaches ruman after swallowing here it gets partially digested and is called cud

Reticulum:- This is a second chamber where the cud goes and is sent back to the mouth to be chewed further.

Omasum:- This is the third Chamber where th rechewed food reaches after swallowing again.Here the food is further digested by digestive juices.

Abomasum:- This is the fourth chamber.The food is further digested here. After digestion the food goes to the small and large intestine for absorption of nutrients.

Activity:-

Aim:-To study the effect of saliva on starch

Method:-Take 2 gm of cornflour and add 25 mL of water to it to make a solution. Take 5 mL from this mixture in a test tube and add 2 drops of iodine. Observe the change in the colour.You will notice that the colour changes to violet proving that cornflour has starch in it.

Now, collect about 5 mL of saliva from your mouth in a test tube.

Take to mL of the cornflour mixture in another test tube and add to it 2 mL of freshly collected saliva. Shake it well and keep it aside for about minutes. Divide this mixture in two test tubes.

To one test tube add 2 drops of iodine. Mark it as 'A'. Shake the test tube well.

To the other add 3-4 drops of Benedict's solution and mark it as 'B'. Shake the test tube well (Benedict's solution gives brown colour with sugar).

Observation:- You will notice tube A does not show violet colour with iodine thereby showing that there is no starch in it.Tube B shows brownish colour with Benedict's solution thereby showing the presence of sugars.It is hence proved that starch of cornflour is converted into sugars by the action of saliva.