Subject: Biology Date: 12th March 2020

Dear Students,

Carefully read the notes given below, make notes based on your understanding of
the concepts and practice the diagrams mentioned. Utilize your time wisely and start
preparing for the new academic year. All the Best!

Stay safe and avoid crowded areas.

Chapter: Life processes

Introduction:

Life Processes: All organisms perform some basic functions to keep themselves alive.
The basic functions carried out by living organisms to maintain and continue life on this
earth are called life processes. The basic life processes common to all living organisms
are:

Nutrition
Respiration
Transportation of substances
Excretion
Control and coordination(Response to stimuli)
Growth
Movement
Reproduction

Nutrition: The process of nutrition involves the taking of food inside the body and
converting it into smaller molecules which can be absorbed by the body.

Need of nutrition: Organisms need energy to perform various activities. The energy
is supplied by the nutrients. Organisms need various raw materials for growth and
repair. These raw materials are provided by nutrients.

Nutrients: Materials which provide nutrition to organisms are called nutrients.

Carbohydrates, proteins and fats are the main nutrients and are called macronutrients.
Minerals and vitamins are required in small amounts and hence are called
micronutrients.
Respiration: Respiration is the process which releases energy from the food absorbed
by the body.
Transport: Transport is the process in which a substance absorbed or made in one
part of the body is moved to other parts of the body.

Excretion: Excretion is the process in which the waste materials produced in the cells
of the body are removed from the body.

Control and coordination (response to stimuli): Control and coordination is a

process which helps the living organisms to survive in the changing environment
around them.
Importance of control and coordination
A living being does not live in isolation. It has to constantly interact with its external
environment and has to respond properly for its survival. For example; when a hungry
lion spots a deer, the lion has to quickly make a move so that it can have its food. On
the other hand, the deer needs to quickly make a move to run for its life. The
responses which a living being makes in relation to external stimuli are controlled and
coordinated by a system; especially in complex animals.

Growth: The process of growth involves the change from a small organism to a big
organism (or an adult organism).

Movement: In movement, the organism either moves from one place to another or
moves its body parts while remaining at the same place.

Reproduction: The process of reproduction involves the making of more organisms

from the existing ones, so that organisms could live on this earth forever.

Notes:

Nutrition in plants:

Green plants are autotrophic and synthesize their own food by the process of
photosynthesis.
The process, by which green plants make their own food from carbon dioxide and
water by using sunlight energy in the presence of chlorophyll, is called
photosynthesis.
Oxygen is released during photosynthesis.
The process of photosynthesis can be represented as:
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.
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.
Equation:

Conditions necessary for photosynthesis:

1. Sunlight
2. Chlorophyll
3. Carbon dioxide
4. water
Raw materials for photosynthesis:
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.
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.
When water flows into the guard cells, they swell, become curved and cause the
pore to open.
On the other hand, when guard cells lose water, they shrink, become straight and
close the stomatal pores.

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

The site of photosynthesis in a cell of the leaf is chloroplasts which contain
chlorophyll.
Chloroplasts are present in the photosynthetic cells (mesophyll cells) of green
plants. These cells contain more chlorophyll than other plant cells.
 Experiments: The experiments on photosynthesis depend on the fact that green leaves make
starch as food and the starch gives a blue –black colour with iodine solution.

Experiment to show that Sunlight is necessary for photosynthesis:

1. Take a potted plant with green leaves and place it in a dark place for about three
days to destarch its leaves.
2. Take a thin strip of aluminum foil and wrap it in the centre of one leaf on the both
sides so that sunlight may not fall on this covered part of the leaf.
3. The remaining part of the leaf remains uncovered and exposed to sunlight.
4. Now keep the plant in sunshine for about six hours.
5. Pluck the partially covered leaf from the plant and remove its aluminum foil.
6. Remove its green color chlorophyll by boiling the leaf in alcohol with the help of
water bath.
7. Wash the decolorized leaf with water to remove any chlorophyll which may be
sticking in it.
8. Pour iodine solution over the colorless leaf and observe the change in colour of the
leaf.
Observation:
1. On adding iodine solution, Covered part of the leaf does not turn blue-black
showing that no starch is present in this middle part of the leaf.
2. The uncovered part of the leaf which received light turns blue-black showing that
starch is present in this part of the leaf.
Inference: Since the part of the leaf which was covered and hidden from sunlight does not
contain starch and the part of the leaf which was exposed to sunlight contains starch.
Therefore, sunlight is necessary for photosynthesis.
INTEXT Questions and answers:
1. Why is diffusion insufficient to meet the oxygen requirements of multi-cellular organisms
like humans?
Unlike the unicellular organisms, the multi-cellular organisms have complex body
structures with specialized cells and tissues to perform various necessary functions of the
body. Since these cells are not in direct contact with surrounding environment, simple
diffusion cannot meet the oxygen requirement of all these cells.

2. What criteria do we use to decide whether something is alive?

The presence of life processes (Nutrition, Respiration, Transportation of substances,
Excretion, Control and coordination [Response to stimuli] Growth, Movement,
Reproduction) is a fundamental criterion that can be used to decide whether something is alive
or not.
3. What are outside raw materials used for by an organism?
 Food as source of supplying energy and materials.
 Oxygen for breakdown of food to obtain energy.
 Water for proper digestion of food and other functions inside the body. The raw
materials required by an organism will vary depending on the complexity of the
organism and its environment.

4. What processes would you consider essential for maintaining life?

Life processes such as nutrition, respiration, transportation, excretion, etc. are essential for
maintaining life.
5. What are the differences between autotrophic nutrition and heterotrophic nutrition?

Autotrophic Nutrition Heterotrophic Nutrition

Food is synthesized from simple Food is obtained directly or indirectly from

inorganic raw materials such as CO 2and autotrophs. This food is broken down with the help of
water. enzymes.

Chlorophyll is required. Chlorophyll is not required.

Food is generally prepared during day Food can be obtained at all time.
time.

All green plants and some bacteria have All animals and fungi have this type of nutrition.
this type of nutrition.

6. Where do plants get each of the raw materials required for photosynthesis?

 Carbon Dioxide: Plants get CO2 from atmosphere through stomata.

 Water: Plants absorb water from soil through roots and transport to leaves.
 Sunlight: Sunlight, which is absorbed by the chlorophyll and other green parts of the
plant
 Nutrition in animals:
 Animals are heterotrophs and hence they depend on other organisms (plants and other animals)
for their food.
 All the animals can be divided into three groups on the basis of their food habits. These are:
1. Herbivores
2. Carnivores
3. Omnivores

Herbivores: Those animals which eat only plants are called herbivores. Examples are Goat, Cow, and
Deer etc.

Carnivores: Those animals which eat only other animals as food are called carnivores. Examples are
Lion, Tiger, and Lizard etc.

Omnivores: Those animals which eat both, plants and animals are called omnivores. Examples are
Man, Dog and Crow etc.

It is the energy of sun which provides food for plants, and animals.

Different steps in the process of nutrition in animals

There are five steps in the process of nutrition in animals.

1. Ingestion: The process of taking food into the body is called ingestion.
2. Digestion: the process in which the food containing large, insoluble molecules is broken down
into small, water soluble molecules is called digestion.
3. Absorption: The process in which the digested food passes through the intestinal wall into blood
stream is called absorption.
4. Assimilation: The process in which the absorbed food is taken in by the body cells and used for
energy, growth and repair is called assimilation.
5. Egestion: The process in which the undigested food is removed from the body is called egestion.
Nutrition in Simple Animals:
Amoeba and paramecium are two very simple unicellular animals. In unicellular animals, all the
processes of nutrition are performed by the single cell.

Nutrition in Amoeba:
 Amoeba eats tiny plants and animals as food which floats in water in which it lives.
 The mode of nutrition in Amoeba is holozoic.
 The process of obtaining food by Amoeba is called phagocytosis.

Steps involved in the nutrition of Amoeba:

Ingestion:
 Amoeba ingests food by forming temporary finger-like projections called pseudopodia around it.
 The food is engulfed with a little surrounding water to form a food vacuole (‘temporary
stomach’) inside the Amoeba.
Digestion:
 In Amoeba, food is digested in the food vacuole by digestive enzymes which break down the
food into small and soluble molecules by chemical reactions.

Absorption:
 The digested simple and soluble substances pass out of food vacuole into the surrounding
environment.

Assimilation:
 The absorbed food materials are used to obtain energy through respiration and make the parts of
Amoeba cell which leads to the growth of Amoeba.

Egestion:
 The remaining undigested material is moved to the surface of the cell and thrown out of the body
of Amoeba.

Nutrition in Paramecium:
 Paramecium is also a tiny unicellular animal which lives in water.

Ingestion:
 Paramecium uses its hair like structures called cilia to sweep the food particles from water and
put them into mouth.
 Ingestion is followed by other steps such as digestion, absorption, assimilation and egestion. (as
written in Amoeba)
 Nutrition in Human Beings (Complex Multicellular Animal):

 The various organs of the human digestive system in sequence are: Mouth, Oesophagus (Food
pipe), Stomach, Small intestine and Large intestine.
 The glands which are associated with the human digestive system are: Salivary glands, Liver and
Pancreas.

The various steps of nutrition in human beings are as follows:

Ingestion:
 In human beings, food is ingested through the mouth. The food is put into the mouth with the
help of hands.

Digestion:
 The digestion of food begins in the mouth itself.
 The teeth cut the food into small pieces, chew and grind it. (Physical digestion)
 The salivary glands in our mouth produce saliva (watery liquid) which contains an enzyme
salivary amylase which digests the starch (carbohydrate) present in the food into sugar.
(Chemical digestion)
 Our tongue helps in mixing this saliva with food.
 The digestion of food remains incomplete in mouth.

Oesophagus:
 The slightly digested food in the mouth is swallowed by the tongue and goes down the food pipe
called oesophagus.
 When the slightly digested food enters the food pipe, the walls of food pipe start contraction and
expansion movements called as peristaltic movement.
 This peristaltic movement of food pipe pushes the slightly digested into the stomach.

Stomach:
 The stomach is a J-shaped organ present on the left side of the abdomen.
 The stomach walls contains three tubular glands in it walls which secrete gastric juice.
 The gastric juice contains three substances: Hydrochloric acid, the enzyme pepsin and mucus.
 The hydrochloric creates an acidic medium which facilitates the action of the enzyme pepsin i.e.
digestion of protein and it also helps in killing the germs which enter the stomach through food.
 The mucus helps to protect the stomach wall from its own secretions of hydrochloric acid.
 The partially digested food then goes from the stomach into the small intestine.

Small intestine:
 From the stomach, the partially digested food enters the small intestine.
 The small intestine is the largest part (about 6.5m) of the alimentary canal.
 The small intestine is very narrow and arranged in the form of a coil in our belly.
 The small intestine in human beings is the site of complete digestion of food (like
carbohydrates, proteins and fats)
 The small intestine receives the secretion of two glands: Liver and Pancreas.
 Liver secretes bile (greenish yellow liquid made in the liver and stored in gall bladder).
  Bile performs two functions:
1. Makes the acidic food coming from the stomach alkaline so that pancreatic enzymes can act on it.
2. Bile salts break the fats present in the food into small globules making it easy for the enzymes to act
and digest them.
The pancreas secretes pancreatic juice which contains enzymes like pancreatic amylase for breaking
down starch, trypsin for digesting proteins and lipase for breaking down emulsified fats.

 The walls of the small intestine contain glands which secretes intestinal juice. The enzymes
present in it finally convert the proteins into amino acids, complex carbohydrates into glucose
and fats into fatty acids and glycerol.
 In this way the process of digestion converts the large and insoluble food molecules into small
water soluble molecules.

Absorption:
 The small intestine is the main region for the absorption of digested food.
 The inner surface of the small intestine has numerous finger-like projections called villi which
increase the surface area for rapid absorption of digested food.
 The digested food which is absorbed through the walls of the small intestine goes into our blood.

Assimilation:
 The blood carries digested and dissolved food to all the parts of the body where it becomes
assimilated as part of the cells and is utilised for obtaining energy, building up new tissues and
the repair of old tissues.

Egestion:
 The unabsorbed food is sent into the large intestine where more villi absorb water from this
material.
 The rest of the material is removed from the body via the anus.
 The exit of this waste material is regulated by the anal sphincter.
INTEXT Questions and answers:

7. What is role of acid in our stomach?

(1) It makes an acidic medium in our stomach which is necessary for activation of pepsin enzyme.
(2) It kills germ present in the food.

8. What is function of digestive enzymes?

The foods consumed by human being are very complex in nature and cannot be utilized directly for our
energy requirement. Digestive enzymes such as amylase, lipase, trypsin, etc. help to break the complex
food particles into simple ones so that these simple particles can be easily absorbed by the blood and
thus transported to all the cells of the body.

9. How is the small intestine designed to digested food?

The digested food coming from the stomach is taken up by the walls of the intestine. The walls of the
small intestine contain glands which secrete intestinal juice. The enzymes present in it finally convert
the proteins to amino acids, complex carbohydrates into glucose and fats into fatty acids and glycerol.
The inner lining of the small intestine has numerous finger-like projections called villi which increase
the surface area for absorption. The villi are richly supplied with blood vessels which take the absorbed
food to each and every cell of the body, where it is utilised for obtaining energy, building up new tissues
and the repair of old tissues.

10. How are fats digested in our bodies? Where does this process take place?
Fats are present in the form of large globules in the small intestine. The small intestine receives the
secretions from the liver and the pancreas. The bile salts (from the liver) break down the large fat
globules into smaller globules so that the pancreatic enzyme lipase can easily act on them. This is
referred to as emulsification of fats. This process takes place in the small intestine.

Practice the following diagrams: (Draw the diagrams in A4 paper)

1. Cross-section of a leaf
2. Open and closed Stomata
3. Nutrition in amoeba
4. The human digestive system

Refer the following link for video:

https://www.youtube.com/watch?v=B2nqrNcN7no