LIFE PROCESSES
 Life Processes
 # Metabolism is defined as the sum total of biochemical


changes taking place in the body of living organisms. It consists of two
components:-
 Anabolism are those biochemical changes in which synthesis takes place
which leads to the growth and repair of damaged cells. egphotosynthesis

+ 6O2
 Catabolism is those biochemical changes in which complex molecules
changes into simplest form and releases energy. eg- respiration

C6H12O6 + 6O2 → 6CO2 + 6H2O + 38 ATP
(Adenosine Tri Phosphate)
 # Molecular movement is the defining characteristic of life. It is needed
to keep repairing and maintaining body structures. All these structures
are made up of molecules; they must move molecules around all the
time.
 # Attributes (characteristic features) of Living Organisms: Nutrition is a process of procurement of food by an organism as well as
the utilisation of food for growth and repair of tissues.
 Respiration is defined as the biochemical oxidation of food to release
energy.
 Growth is the process of increase in the mass of living material of
organisms by absorbing and assimilating new materials from the
environment.
 Movement is the displacement of an organism on their own for food,
shelter or avoid unfavourable conditions.
 Irritability is defined as the response to stimuli by living organisms for
their benefit.
 Adaptation is the ability of an organism to change its structure or
behaviour to survive in a particular environment.
 Reproduction is the process by which an organism produces off springs;
more individuals of the same kind.
 Control and coordination- All the life processes are regulated, controlled
and occur in sequence.
 Question 1. Why is diffusion insufficient to meet the oxygen
requirements of multicellular organisms like humans?
 Ans-> In multicellular organisms, like humans all the cells of the body are
not in direct contact of the surrounding environment. Thus, simple
diffusion will not meet the requirement of all cells, as diffusion is very
slow process. Larger organisms therefore, require an elaborate
respiratory and circulatory system for gaseous exchange and their
transportation.
 Answer the following question: 2. What criteria do we use to decide whether something is alive?
 3. What are outside raw materials used by an organism?
 4. What processes would you consider essential for maintaining life?
 NUTRITION
 # A nutrient can be defined as a substance which an organism obtains
from its surroundings and uses it as a source of energy or for the
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biosynthesis of its body constituents (like tissues and organs). Egcarbohydrate, fats, proteins
 Modes of nutrition mean methods of procuring food or obtaining food
by an organism. Important modes of nutrition are # Autotrophic nutrition is that mode of nutrition in which organisms
make or synthesizes its own food (glucose) from the simple inorganic
materials like CO2 and water with the help of sunlight and chlorophyll.
 a. Photosynthesis-Green plants make its own food from carbon dioxide
and water in the presence of chlorophyll and sunlight.
 b. Chemosynthesis-Green sulphur bacteria uses energy released during
decomposition of H2S for synthesis of food.

 # Heterotrophic nutrition is that mode of nutrition in which an organism
cannot make its own food from simple inorganic material like carbon
dioxide and water and depends on other organisms for its food. Types of
heterotrophic nutrition a. Saprotrophic-An organism obtains its food from dead and decaying
organic matter of dead plants, dead animals and rotten materials. egmushroom, yeast, bacteria
 b. Parasitic-An organism derives its food from the body of another living
organism called its host. eg- Cascuta
 (amarbel), Plasmodium, tape worm
 c. Holozoic- An organism takes the complex food materials into its body
the process of ingestion, the ingested food is digested and then
absorbed into the body cells of the organism. eg-man, cat, dog
 d. Symbiotic-In this method both organisms mutually benefit each other.
eg-Rhizobium found in the root nodules of leguminous plants.
 Answer the following questions: 1. Define photosynthesis. Give balanced equation for this process.
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 2. Where do plants get each of the raw materials required for
photosynthesis?
 3. What are the differences between autotrophic nutrition and
heterotrophic nutrition?
 4. What are the necessary conditions for autotrophic nutrition and what
are it’s by products?
 Activity-1
 # Experiment to show that sunlight is necessary for photosynthesis.
 1. We take a potted plant having green leaves and place it in a
completely dark place for about three days to de-starch its leaves.
 2. Take a thin strip of aluminium foil and wrap it in the centre of one leaf
on both sides so that sunlight may not fall on this covered part of the
leaf.
 3. Keep this potted plant in bright sunshine for three to four days.
 4. Pluck the partially covered leaf from the plant and remove its
aluminium foil.
 5. Put the plucked leaf in a beaker containing some alcohol. Place the
beaker containing alcohol and leaf in a water bath. A water bath is being
used here for heating alcohol because alcohol is highly inflammable
liquid. So, if alcohol is heated directly over a flame, then it will catch fire
at once.
 6. Boil the green leaf in alcohol till all its green pigment chlorophyll is
removed. The leaf will now become almost colourless or pale,
 7. Remove the colourless leaf from alcohol and wash it thoroughly with
water to remove any chlorophyll which may be sticking to it.
 8. Place the colourless leaf in a petridish. Drop iodine solution over the
decolourised leaf with the help of a dropper.
 9. The middle part of the leaf which was covered with aluminium foil
(black chart paper) does not turn blue-black on adding iodine solution
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showing that no starch is present in this middle part of the leaf. This is
because sunlight could not reach the covered middle part of the leaf and
hence leaf could not do photosynthesis to make starch.
 10. The uncovered part of leaf which was exposed to sunlight turns blueblack on adding iodine solution showing that starch is present in this part
of leaf.
 11. From the above observation, we conclude that sunlight is necessary
for photosynthesis.

 Activity-2
 # Experiment to show that chlorophyll is necessary for photosynthesis.
 1. We take a potted plant like croton or Coleus (having variegated
leaves) whose leaves are partly white.
 2. Place this plant in a completely dark place for about three days to destarch its leaves.
 3. Take out the potted plant from the dark place and keep it in bright
sunshine for three to four days.
 4. Pluck the variegated leaf from the plant and remove its green colour.

5. Put the plucked leaf in a beaker containing some alcohol. Place the
beaker containing alcohol and leaf in a water bath. A water bath is being
used here for heating alcohol because alcohol is highly inflammable
liquid. So, if alcohol is heated directly over a flame, then it will catch fire
at once.
 6. Boil the leaf in alcohol till all its green pigment chlorophyll is removed.
The leaf will now become almost colourless or pale.
 7. Remove the colourless leaf from alcohol and wash it thoroughly with
water to remove any chlorophyll which may be sticking to it.
 8. Place the colourless leaf in a petridish. Drop iodine solution over the
decolourised leaf with the help of a dropper.
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 9. We find that the outer part of the leaf that was originally
white(without chlorophyll) does not turn blue-black on adding iodine
showing that no starch is present in this outer part of the leaf.
 10. The inner part of leaf which was originally green(contains
chlorophyll) turns blue-back on adding iodine solution showing that
starch is present in this part of the leaf.
 11. Hence, we conclude that chlorophyll is necessary for the process of
photosynthesis to take place.
 # Opening and closing of stomata is a function of guard cells. When
water enters into the guard cells, it becomes turgid and the stomata
pore opens while in flaccid condition guard cells shrink and the stomata
aperture closes.

Important functions of stomata are-
 i. Helps in gaseous exchange. During day time, carbon dioxide diffuses in
and oxygen diffuses out. During night, oxygen diffuses in and carbon
dioxide is given out.
 ii. It helps in transpiration (loss of water from the surface of leaves
through stomata).
 iii. It helps in transportation of water from root hair to the leaves and in
osmoregulation.


Chlorophyll traps the solar energy and converts it into chemical energy
during photosynthesis.

The range of wavelength in visible light is from 400 nanometre to 700
nm(violet colour having the minimum wavelength of 400 nm and red
colour having the maximum wavelength of 700 nm)

Chlorophyll absorbs mainly blue-violet light and red-orange light but it
does not absorb the green light. It reflects the green light giving the
plants their characteristic green colour.
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
The carotenoids are yellow, orange, red or brown pigments which
absorb sunlight.

The aquatic plants use the carbon dioxide dissolved in water for
carrying out photosynthesis.

The point at which photosynthesis and respiration in a plant are
exactly balanced, and one process uses up the products of the other
process is called compensation point.

Factors affecting the rate of photosynthesis are as follows-
 1. Light-If the light intensity is slowly increased, the rate of
photosynthesis increases up to a point, after which it becomes constant.
 2. Carbon dioxide-As the amount of carbon dioxide available to a plant is
increased, the rate of photosynthesis increases up to a point and then
becomes constant.
 3. Water-If the amount of water available to a plant decreases, the rate
of photosynthesis decreases.
 4. Temperature-As the temperature is increased, the rate of
photosynthesis increases up to a certain temperature. At high
temperature, the rate of photosynthesis decreases again (it becomes
slow).
 # The site of photosynthesis in a cell of the leaf is chloroplast. In a crosssection of a leaf, chloroplasts can be seen as numerous disk-like
organelles in the mesophyll cells of the palisade tissue just below the
upper epidermis. A sac lined with a membrane containing chlorophyll is
called a thylakoid. One thylakoid stack is called granum (plural grana).
Light reaction takes place in thylakoid or grana and dark reaction takes
place in stroma or matrix.
 DRAWING
 Nutrition in Animals
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 # Animals are heterotrophy hence they obtain their food from plants or
animals which they eat. On the basis of their food habits they are divided
into following types i. Herbivores- eat only plants and plant products eg- goat, cow, horse
 ii. Carnivores- eat only other animals and animal products eg-lion, tiger
 iii. Omnivores- eat both plants and animals eg- man, dog
 # Pitcher plant and the venus fly-trap are insectivorous plants
 # The process of obtaining food and then using it for obtaining energy,
growth and repair of the body is called nutrition. Nutrition involves
following five steps in animals i. Ingestion-The process of procuring (taking) food into the body.
 ii. Digestion-The process in which the large, insoluble food molecules are
broken down into small, water soluble molecules.
 iii. Absorption-The process in which the digested food passes through
the intestinal wall into blood stream.
 iv. Assimilation-The process in which the absorbed food is taken in by
body cells and used for energy, growth and repair.
 v. Egestion-The process in which the undigested food is removed from
the body.
 # Nutrition in amoeba-Amoeba is a unicellular animal which eats tiny
(microscopic) plants and animal which float in water (zooplanktons and
phytoplanktons). The mode of nutrition is holozoic. The process of
obtaining food by Amoeba is called phagocytosis. Amoeba takes food
inside the body by its pseudopodia. The food is engulfed with little
surrounding water form food vacuole inside the amoeba.
 The enzymes from surrounding cytoplasm enters into the food vacuole
and break down the food into small and soluble molecules by chemical
reaction. The digested food is absorbed directly into the cytoplasm by
diffusion.
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 A part of the food is used to obtain energy through respiration; rest is
used for repair, growth and development. Thus on assimilating food
amoeba grows in size and then can reproduce by dividing into two
daughter nuclei. When a considerable amount of undigested food is
collected inside the body, then its cell membrane suddenly ruptures and
the undigested food is thrown out of the body of amoeba.
 Nutrition in human beings-All the processes involved in nutrition is
performed by a combination of digestive organs and glands. The various
organs of the human digestive system in sequence are-mouth,
oesophagus (food pipe), stomach, small intestine (duodenum, jejunum
and ileum), large intestine (colon and rectum) and anus. Salivary glands,
liver, pancreas are also associated with digestive system. The human
alimentary canal which runs from mouth to anus is about 9 metres long
tube. Various steps of nutrition in man are i. Ingestion- In human beings, food is ingested through the mouth.
 ii. Digestion- The mouth cavity (buccal cavity) contains teeth, tongue and
salivary glands. The teeth cuts (incisor) the food into small pieces, tears
(canines), chews and grinds (molars/premolars) it. Salivary glands
secrete salivary amylase (ptyalin) which digests the starch into maltose
sugar. Tongue contains taste buds which is sensitive to different tastes
and helps in mixing food with saliva. Semi-solid paste so formed is called
bolus. Mouth opens into a small funnel shaped
 Mouth opens into a small funnel shaped
 area called pharynx which leads to a long tube called oesophagus. When
the slightly digested food enters the food pipe, the walls of food pipe
starts contraction and expansion movements called peristalsis or
peristaltic movement. This pushes the bolus into the stomach. The
stomach is a J-shaped organ present on the left side of the abdomen.
The gastric glands present in the walls of the stomach secrete gastric
juice which includes-
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 i. Mucus covers the inner linings of the stomach and helps to protect it
from the action of HCl and proteolytic enzymes.
 ii. HCl makes the medium acidic. It kills germs present in food and
converts inactive pepsinogen into active pepsin.
 iii. Pepsin begins the digestion of protein present in food into peptones
and amino acids. Even the sight, smell or thought of food can initiate the
secretion of gastric juice. Partially digested food then goes from the
stomach into the small intestine. Duodenum receives the secretion of
two glands-liver and pancreas through a common duct. The bile secreted
by the liver is normally stored in gall bladder until needed in the
duodenum. Bile is alkaline and contains salts which help to emulsify or
break down fats or lipids present in the food. Bile also makes the
medium alkaline and hence only those enzymes which can work in
alkaline medium are active. Pancreas secretes pancreatic juice which
contains enzymes like trypsin, amylase and lipase. The walls of small
intestine contain glands called succus entericus which secretes enzymes
like amylase, lipase, chymotrypsin, etc. Food is completely digested in
the small intestine by the action digestive enzymes.
fatty acids + glycerol
iii. Absorption- Ileum is specially designed for absorbing digested food.
The inner surface of ileum has millions of tiny, finger-like projections
called villi. It increases the surface area for absorption. Inner layer of
ileum is thin for better absorption and it is richly supplied by blood
vessels. The digested food which is absorbed through the walls of the
ileum goes into our blood.
iv. Assimilation- The blood carries digested and dissolved food to all the
parts of the body cells for obtaining energy as well as for growth and
repair of the body.
v. Egestion- The undigested food passes from the small intestine into a
wider tube called the large intestine. The walls of colon absorb most of
the water from the undigested food. Rectum store undigested food for
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some time. The undigested food is removed from the body through anus
with the help of anal sphincter muscles as faeces.
 DRAWING
 # The liver has multiple functions but its main function is to process the
nutrients absorbed from the small intestine. Bile secreted by it emulsifies
fat. The liver is body’s chemical factory. It also detoxifies potentially
harmful chemicals. It breaks down and secretes many drugs. Excretion of
bilirubin, cholesterol etc. Metabolism of fats, proteins and carbohydrate
take place here. It provides immunity to body.
# A round and depressed lesion or wound is called an ulcer. An ulcer on
the inner lining of the stomach is called peptic ulcer. It is caused by
higher acidity of gastric juice.
# The length of the small intestine differs in various animals depending
on the food they eat. Herbivores eating grass need a longer small
intestine to allow the cellulose to be digested. Meat is easier to digest,
hence carnivores like tigers have a shorter small intestine.
 # Dental caries are tooth decay that causes gradual softening of enamel
and dentine. Masses of bacterial cells together with food particles stick
to the teeth to form dental plaque. Saliva cannot reach the tooth surface
to neutralise the acid as plaque covers the teeth. Brushing the teeth
after eating removes the plaque before the bacteria produce acids. If
untreated, micro-organisms may invade the pulp, causing inflammation
and infection.
 Respiration
 # Respiration is a biochemical oxidation of food to release energy in the
form of ATP molecules.
 # Comparison between respiration and combustion I Similarities: 1. Both are oxidation reactions.
 2. Oxygen is required in both processes.
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 3. Energy is produced in both processes
 4. Both of them are exothermic reactions
 5. Carbon dioxide is given out in both processes.
 II Differences: 1. Respiration takes place in living organism (mitochondria).
Combustion takes place in non-living environment.
 2. It is a biochemical change
It is a chemical change.
 3.
Enzymes are involved. Enzymes are not involved.
 4.
Energy is released very gradually. Energy is released rapidly.
 5. Energy is stored in the form of ATP molecules. Energy is produced in
the form of heat and light.
 # Difference between respiration and breathing: 1. Respiration is a biochemical process.
 2. It takes place in mitochondria.
gills.
Breathing is physical change
It takes place in organs like lungs,
 3. Enzymes are involved. Enzymes are not involved.
 4. It produces energy.
Energy is not involved.
 5.
Food (glucose) combines with O2. Gaseous exchange (O2 is
diffused in CO2 is given out) takes place.
 6. ATP molecules are required and formed. ATP molecules are not
formed or required.

 # The process of inhaling fresh air from the atmosphere into lungs and
expelling carbon dioxide out is known as breathing. It is a mechanical
process which involves two distinct steps 1. Inspiration-During this phase, the diaphragm move downwards and
intercostal muscles attached to the ribs outwards due to which thoracic
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cavity expands. It results into an increase in the volume of thoracic cavity
which reduces air pressure inside the lungs hence from outside rushes
into lungs through the nostrils, trachea and bronchi.
 2. Expiration-During this phase, the muscles attached to the ribs relax.
The diaphragm moves upwards and intercostal muscles inwards due to
which volume of thoracic cavity is reduced hence air pressure inside the
lungs increases so air from the lungs diffuses out into trachea, nostrils
and then out of the body.
 # Mechanism of cellular respiration:- Glucose (C6H12O6) is a six-carbon
compound. It is the simple food which is oxidised in the cell of living
organisms during respiration. The decomposition of glucose to pyruvic
acid is called glycolysis. It occurs in the cytoplasm of the cell. The
oxidation of glucose to pyruvic acid does not require oxygen.
 # If oxygen is available in sufficient amount, then pyruvate is completely
oxidised to carbon dioxide and water and 38 ATPs are formed. If oxygen
is not sufficient, pyruvate is converted to ethanol and carbon dioxide in
yeast or lactic acid in muscle cells and only 2 ATPs are formed.
 # There are two types respiration: 1. Aerobic respiration

ATP
 2. Anaerobic respiration

C6H12O6 (glucose) glyco

2ATP

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 # Differences between aerobic and anaerobic respiration
Aerobic respiration
Anaerobic respiration
 1. Aerobic respiration takes place in the presence of O2 Anaerobic
respiration takes place in the absence of O2
 2.
Complete breakdown of food occurs.
food occurs.
Partial breakdown of
 3. The end products are carbon dioxide and water.
The end products
are ethyl alcohol and CO2 (in yeast) or lactic acid in muscles.
 4. Produces considerable amount energy (38 ATPs).
energy (2 ATP molecules)
Produces less
 5. It takes place in cytoplasm and mitochondria. It takes place in
cytoplasm only.

 # The respiration in plants differ from that in animals in three respects 1. All the parts of a plant (like root, stem and leaves) perform respiration
individually. On the other hand, an animal performs respiration as a
single unit.
 2. During respiration in plants, there is a little transport of respiratory
gases from one part of plant to the other whereas respiratory gases are
usually transported over long distances inside an animal.
 3. The respiration in plants occurs at a slow rate. The respiration in
animals occurs at much faster rate.
 # The respiration in plants differ from that in animals in three respects 1. All the parts of a plant (like root, stem and leaves) perform respiration
individually. On the other hand, an animal performs respiration as a
single unit.
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 2. During respiration in plants, there is a little transport of respiratory
gases from one part of plant to the other whereas respiratory gases are
usually transported over long distances inside an animal.
 3. The respiration in plants occurs at a slow rate. The respiration in
animals occurs at much faster rate.

 # Respiration in plants occurs during day time as well as night.
Photosynthesis occurs only during day time. Gaseous exchange in plants
occurs in the roots, stems and leaves of plants by diffusion. The net
gaseous exchange during day time is – O2 diffuses out, CO2 diffuses in.
The net exchange during night - CO2 diffuses out, O2 diffuses in.
 # Plants die if their roots remain waterlogged for a considerable time
because too much water expels all the air from in-between the soil
particles. Due to this, oxygen is not available to the roots for aerobic
respiration. Alcohol produced due to anaerobic respiratory may kill the
plant.
 Lenticels is an area in a woody stem where the cells are loosely packed,
allowing the gaseous exchange.
 Stomata are the pores on the lower surface of the leaves
 # Respiration in animals
In simple unicellular animals like amoeba respiration takes place by
simple diffusion of gases through the cell membrane.

In earthworm, leeches and frogs the gaseous exchange takes place
through skin over the entire body surface, this type of respiration is
called cutaneous mode of respiration.

In insects like grasshopper, cockroaches, houseflies etc. Gaseous
exchange through tubes called trachea or tiny holes on their body called
spiracles.
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
In fish, prawn and tadpole of frogs gaseous exchange occurs through
gills.

Gaseous exchange occurs through lungs in reptiles, birds, mammals.

Respiratory organs have three common features-
 i. All the respiratory organs have a large surface area to get enough
oxygen.
 ii. All the respiratory organs have thin walls for easy diffusion and
exchange of respiratory gases.
 iii. They have a rich blood supply for transporting respiratory gases.
 # Respiration in fish: - The fish breathes by taking in water through its
mouth and sending it over the gills. When water passes over the gills, the
gills extract dissolved oxygen from this water. The extracted oxygen is
absorbed by the blood and carried to all the parts of the fish. The carbon
dioxide produced by respiration is brought back by the blood into the
gills for expelling into the surrounding water.
 # Respiratory system of man consists of the following parts-Nose, nasal
passage, trachea, bronchi, lungs and diaphragm. Our nose two holes
called nostrils which lead to nasal cavity. Nasal cavity is separated from
the mouth cavity by a hard bony plate. Hair and mucus filters the air and
passes into pharynx and then into the wind pipe (trachea) through a slit
called glottis. At the top of the trachea is a flap of cartilage called
epiglottis which covers the mouth of trachea so that food may not enter
the trachea after we swallow food. The trachea does not collapse even
when there is no air in it because it is supported by rings of soft bones
called larynx. The upper end of trachea has a voice box called larynx. The
trachea runs down the neck and divides into two smaller tubes called
bronchi which are connected to their respective lungs. The lungs lie in
the thoracic cavity which is separated from abdominal cavity by a
muscular partition called diaphragm. The lungs are covered by two thin
membranes called pleura. Each bronchus divides in the respective lungs
to form large number of smaller tubes called bronchioles which ends in
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pouch-like air-sacs called alveoli. The walls of alveoli are very thin and
they are surrounded by very thin blood capillaries. There are millions of
alveoli in each lung which provides large surface area for exchange of
gases (50 m2-100 m2).
# The thinning of lung tissues
leading to the rupture of alveoli is called emphysema.
 # In 24 hours, we breathe in about 15000 litres of air.
 # There are two vocal cords stretched across the voice box. The vocal
cords vibrate to produce sound which results in speech.
 # Transport is a life process in which a substance absorbed in one part of
the body of an organism is carried to other parts of its body. Organisms
need transport systems in their bodies to supply all their cells with food,
oxygen, water and other materials.
 # Transport system in plants is less elaborate than in animals. Plants are
less active, so their cells do not need to be supplied with materials so
quickly. Plants have two transport systems 1. Xylem carries water and minerals. It consists of four components i. Xylem vessels are non-living, long tubes which run like a drainpipe
through the plant. The walls of xylem vessels are made of cellulose and
lignin. Wood is made almost entirely of lignified xylem vessels. Xylem
vessels have pits (no lignin deposition) on their thick walls. They provide
strength.
 ii. Tracheids are long thin spindle shaped cells with pits on their walls.
They are dead cells with lignified walls but do not have open ends so
water pass from one tracheid to another through these pits.
 iii. Xylem parenchyma is made up of living cells. It fills empty spaces and
stores food.
 iv. Xylem fibres are made up of dead cells. They give support.

 https://youtu.be/OSqhTmiXhVI
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 # Mechanism of transport of water and minerals-The plants take in
water from the soil through their root hairs by process of diffusion. It
passes from cell to cell by osmosis through the epidermis, root cortex,
endodermis and reach the root xylem. The water enters from the root
xylem vessels into stem xylem vessels. It reaches to the leaves through
the branched xylem vessels which enter from the petiole (stalk of the
leaf) into each and every part of the leaf. 1-2% of water absorbed by the
plant is used by the plant.
 The continuous evaporation of water from the cells of a leaf creates a
kind of suction which pulls up water through the xylem vessels. Capillary
action, cohesive force between water molecules and adhesive force
between water and vessels also help in the ascent of sap from the roots
to the leaves through the stem.

 2. Phloem translocates the food made in the leaves. It carries food from
leaves to all other parts. It also transports hormones made by plants in
their root and shoot tips. Phloem consists of four elements i. Sieve tubes are made up of living cells with cytoplasm but no nucleus.
They are joined end to end to form long tubes. The end walls of cells of
the phloem form sieve plates which have holes in them.
 ii. Companion cell has a nucleus and many other cell organelles. It is
located next to each sieve tube and supply it some of its requirements.
 iii. Phloem parenchyma fills the empty spaces and stores food.
 iv. Phloem fibre gives mechanical support and protection to inner parts
of the body.

 # Transport of food and other substances-The food (glucose) is made in
the mesophyll cells of a leaf. It is transported in plants by phloem tissues.
The food made in leaves is loaded into the sieve tubes by utilising energy
in the form of ATP. Water now enters into sieve tubes containing sugar
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by the process of osmosis due to which the pressure in phloem rises.
This high pressure produced in the phloem tissue moves the food to all
the parts of the plant having less pressure in this tissue. Other
substances made by the plant like hormones are also carried by the
phloem tubes from one part of the plant to its other parts.
 DRAWING
 The human circulatory system consists of the heart, arteries, veins,
capillaries and blood.
 # Blood is a fluid connective tissue. The main components of blood are i. Plasma is a colourless liquid which consists of 90% water and dissolved
substances such as proteins, digested food, common salt, waste
products like carbon dioxide and urea and hormones. RBCs, WBCs and
platelets are immersed in it.
 ii. Erythrocytes or RBCs are circular in shape. Mature mammalian RBCs
do not have nuclei. They contain red colouring pigment called
haemoglobin which carries oxygen in the body. Life span is about 4
months.
 iii. Leucocytes or WBCs fight infection and protect us from diseases. They
are spherical or irregular in shape and manufacture antibodies which are
responsible for providing immunity in our body.
 iv. Platelets are tiny fragments of special cells formed in the bone
marrow. They help in the coagulation/clotting of blood after a cut or in a
wound.

 # Functions of blood: 1. It carries carbon dioxide from the body cells to the lungs for breathing
out.
 2. It carries digested food from the small intestine to all the parts of the
body.
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 3. It carries hormones from the endocrine glands to different organs of
the body where they are needed.
 4. Blood carries waste product like urea from the liver to the kidneys for
excretion as urine.
 5. Blood protects the body from diseases. WBCs kill the bacteria and
other germs which cause diseases.
 6. Blood regulates the body temperature. This is because the blood
capillaries in our skin help to keep our body temperature constant at
about 370c.
 Blood vessel, a vessel in the human or animal body in which blood
circulates. The vessels that carry blood away from the heart are called
arteries, and their very small branches are arterioles. Very small
branches that collect the blood from the various organs and parts are
called venules, and they unite to form veins, which return the blood to
the heart. Capillaries are minute thin-walled vessels that connect the
arterioles and venules; it is through the capillaries that nutrients and
wastes are exchanged between the blood and body tissues.
 * The heart is roughly triangular in shape. It is made up of cardiac
muscle. The size of our heart is about the same size as our clenched fist.
It has four compartments called chambers. Left and right chambers are
separated by a wall called septum. The upper two chambers of heart are
called atria (atrium) and the lower two chambers of heart are called
ventricles. The two atria receive blood from the two main veins and the
two ventricles transport blood to the entire body and the lungs. The left
atrium is connected to the left ventricle through a bicuspid valve.
Similarly, the right atrium is connected to the right ventricle through
another valve tricuspid valve. These valves prevent the backflow of
blood into atria when the ventricles contract to pump blood out of the
heart to the rest of the body. A sheath of tissue called pericardium
protects the muscular heart.

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 * The heart beat is due to the rhythmic contraction and relaxation of the
heart muscles which make up the atria and the ventricles.
 * Circulation of blood in the human body- When the muscles of all the
four chambers of the heart are relaxed, the pulmonary vein brings the
oxygenated blood from the lungs into the left atrium of the heart. When
the left atrium contracts, the oxygenated blood is pushed into the left
ventricle through the bicuspid valve. When the left ventricle contracts
the oxygenated blood is forced into the main artery called aorta. Aorta
then branches into smaller arteries which go into different body organs
(except the lungs). When the oxygenated blood passes through the
capillaries, it gives oxygen to the body cells. It also gives the digested
food and other dissolved materials to the body cells. At the same time,
CO2 produced during respiration enters into the blood. The
deoxygenated blood from the body organs enters into the main vein.
The main vein carries the deoxygenated blood to the right atrium of the
heart. When the right atrium contracts, deoxygenated blood is pushed
into the right ventricles through the tricuspid valve. Then the right
ventricle contracts and the deoxygenated blood is pumped into the lungs
through the pulmonary artery. A circulatory system in which the blood
travels twice through the heart in one complete cycle of the body is
called double circulation. In the human circulatory system the pathway
of blood from the heart to the lungs and back the heart is called
pulmonary circulation and the pathway of blood from the heart to the
rest of the body and back to the heart is called the systemic circulation.
 DRAWING
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