INTERMEDIATE STAGE BIOLOGY
Biology
Sindh Text Book Board, Jamshoro.
INTERMEDIATE STAGE
BIOLOGY
BOOK TWO
FOR CLASS XII
For
Sindh Textbook Board, Jamshoro.
Book arranged by
Biology
Sindh Text Book Board, Jamshoro.
CONTENTS
CHAPTER
1
HOMEOSTASIS
3
CHAPTER
2
SUPPORT AND MOVEMENT
7
CHAPTER
3
CO-ORDINATION AND CONTROLS
38
CHAPTER
4
REPRODUCTION
74
CHAPTER
5
GROWTH AND DEVELOPMENT
82
CHAPTER
6
CHROMOSOMES AND DNA
92
CHAPTER
7
CELL CYCLE
98
CHAPTER
8
VARIATION AND GENETICS
104
CHAPTER
9
BIOTECHNOLOGY
112
CHAPTER
10
EVOLUTION
118
CHAPTER
11
ECOSYSTEM
122
CHAPTER
12
SOME MAJOR ECOSYSTEM
132
CHAPTER
13
MAN AND HIS ENVIRONMENT
141
Book arranged by
Biology
Sindh Text Book Board, Jamshoro.
Chapter 1
HOMEOSTASIS
OSMOREGULATION:
It is the control of the gain and loss of water and dissolved solute.
EXCRETION:
The removal of excess and unwanted products from cells are called as excretion.
THERMOREGULATION:
The maintenance of the internal temperature within range that allows cell to
function efficiently is called as thermoregulation.
FEED BACK SYSTEM:
There are number of physiological process functioning in the body to maintain the
homeostasis. It requires the check and balance.
The check and balance system is called as feedback system.
Usually hormones control this feed back system but it is ultimately controlled by
nervous system.
When any change in the internal environment takes place it is detected by the
receptors and immediately reported to control center that is brain which decided
about the appropriate responses and sends its instructions to the effectors. That
plays very important role and brings the substance back to normal.
The feed back may be negative or positive.
NEGATIVE FEED BACK:
The opposite effect produced in the relation to any changes in the body fluids is
called as negative feed back. For example when a person takes the sugar the
level of glucose will rise in blood. It will triggers the mechanism, that will
decreases the level of glucose back to the normal level.
POSITIVE FEED BACK:
Similar affects produced which leads to the enhancement of change. For example
once child birth process begins then each succeeding event will make it more
likely that the process will continue until the completion.
OSMOREGULATION:
The metabolic reaction on which life depends require a precise balance of water
and dissolved salt. Among the salts whose concentration must be reguylated and
amino acids, proteins and dissolved ions such as sodium potassium, calcium, and
bicarbonate. Each cell must adapt to definite quantity of the water in relation to
salts in it to perform its function. Homeostatic
mechanism maintain the
concentration by osmoregulatuion.
BALANCE OF WATER AND SALTS:
Osmosis occur when two solutions of different concentrations are separated by
cell membrane.
Book arranged by
Biology
Sindh Text Book Board, Jamshoro.
There is net movement of water from hypotonic solution to hypertonic solution
until the solute concentration are equal on both sides of the cell.
When the concentration of water is greater outside the cell the water moves from
outside to inside the cell and the cell become turgid. The cell swells and may
burst. But if there is loss of water from cells the cell shrinks and dries. To avoid
this condition the cell osmoregulatte themselves to keep water and salt balance.
OSMOREGULATION IN PLANTS:
Efficient functioning of plant cell and the whole plant depend on maintaining the
water content at the steady state. According to the availability of the water the
plants are divided into four groups.
1.
2.
3.
4.
Hydrophates
Mesophates
Xerophates
Halophates
HYDROPHATES:
Hydrophates are those plants which are found in the fresh water. The plants may
be partly or totally submerged in water They do not have any difficulty in
obtaining water. To remove excessive water, they have following adaptations.
ADAPTIONS:
?
?
?
?
Their leaves are large so surface area is large for removal of excessive
water by transpiration.
They have large numbers of stomata at upper surface of leaves,.
The stomata always remain open.
Root is absent if present root hairs are absent.
MESOPHATES:
The type of plants that are found in the moderate supply of water majority of
angiosperms are mesophates. These are the land plants and can easily maintain
their water balance.
When there is sufficient supply of water, the stomata are kept open but when
there is restricted supply the stomata are closed.
To prevent excessive loss, the stems and leaves are covered with cuticle.
Shape of leaves is variable which also helps in regulating the water. Leaf fall also
help in regulating the water.
XEROPHATES:
These are the plants which are found in the dry placesuch as deserts, steep hills.
Under such conditions, the water potential is very low. They have the following
adaptions to prevent the water loss.
Root is deep vertical to absorb more water from soil and it also spread
horizontally.
Leaves in most cases are absent or shed during dry season. In such cases the
stem become green and performs the function of photosynthesis.
Leaves become small or modified into spines to reduced the rate of transpiration.
The leaves are covered with cuticle or by hairs.
Number of stomata are reduced and are sunken type.
Book arranged by
Biology
Sindh Text Book Board, Jamshoro.
In rainy season stem root and leaves store water in their parenchymatous cells
such parts are called succulent.
HALOPHATES:
The plants growing in salt marshes close to sea are called halophates. They have
to absorb water, which has high salt concentration
Such plants actively absorb salt by their root and as the salt concentration in their
root cell become high, they absorb water by osmosis.
Excess of salt absorbed by root, stored in the cells is executed out from salts
glands in leaves.
The salt thus secreted by some species help them to trap water vapours from air,
which is being absorbed in liquid form by leave surface.
EXCRETION:
Survival in any environment requires an accurate balance between excretion and
animal¡¯s need of water and salts. The excretory system plays a central role in
homeostasis by forming and excreting urine while regulating the amount of salt
and water in body fluid.
EXCRETION IN ANIMALS:
Animals are very active group of organisms and need energy for life activities.
They get energy from the break down of food. As a result many waste products
are produced. They are harmful if remain in the body for long time. Therefore,
excretion is necessary to keep the animal alive.
EXCRETION IN PLANTS:
Among plants oxygen, water, carbon dioxide and some mineral crystal could be
looked as a waste.
OXYGEN:
It is a by product of photosynthesis and is eliminated through stomata.
CARBON DIOXIDE:
It is by product of respiration which is eliminated through stomata.
WATER:
Extra amount of water is excreted by transpiration or in some land plants it is
excluded in liquids form from hydathodes found at the margin and tips of the
leaves which is called as guttation.
CRYSTAL FORMATION:
The plants produce some organic and inorganic salt which are stored in the leaves
the leaves die and fall off and thus plants gets rid off these salts.
Falling of yellow leaves in the autumn season is a mean to get rid off such
poisonous substances.
OSMOREGUALTION IN FRESH WATER ANIMALS:
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