Grade -8(Science) : - Life Process
Unit :-18 Life process
Life process: Living being perform various activities i.e. respiration ,digestion ,excretion ,reproduction etc. to survive .These activities are called life process .
Reproduction : The biological process in which
living organism produce new individual their own kinds
by sexual and asexual method is called reproduction .It help all the organism for continuity of life .
Types of reproduction : It is divided into 2 types :
A)Asexual reproduction: The reproduction which takes place without fusion of male and female gametes is called asexual reproduction .
1.Asexual reproduction in plant and Animals: There are 6 types asexual reproduction in plants and animals:
i)Fission: The process of asexual reproduction in which a parent organism divides into two or daughter organism is called fission .It is two types :
a)Binary fission : The in which parent body divides into 2 daughter organism is called binary fission .For example :Bacteria, diatoms euglena etc.etc.
.ii)Budding: The process of asexual reproduction which takes place by the formation of the buds is called budding .For example :Yeast, Hydra,etc.
iii)Regeneration: The process of asexual reproduction in which
an organism breaks into two or more fragments and each fragments develop into
new organism is called regeneration.For
example: Tape worm ,Planaria, star fish etc.
iv)Fragmentation: The process of asexual
reproduction in which an organism breaks into two or more fragments and each
fragments develop into new organism is called fragmentation .For example: Spirogyra ,Marchantia etc.
v)Sporulation: The process of asexual reproduction which
takes place by the formation spores is called sporulation .For example:Mushroom, moss Fern,etc.
vi)Vegetative propagation : The process of asexual reproduction which takes place by the vegetative parts of plants i.e. root,stem and leaf is called vegetative propagation .For example :
i)By roots :sweet potato,dahlia, etc.
ii)By stem :Potato,onion,ginger,mint
etc.
iii.)By leaf:Bryophyllum,Begonia etc
Advantages
of vegetative propagation:
i)It is cheaper ,easier ,and faster method of reproduction
.
ii)It is used to produce those plants which do not produce good quality of seeds i.e. rose, sugarcane, potato ,banana etc.
iii)The new plants produced by vegetative
propagation are genetically identical to their
parents .
iv)The plants produce by
vegetative propagation grow rapidly .
2.)Sexual reproduction : The reproduction which takes place by the
fusion of male and female gametes is called sexual reproduction. The diagram
show the process of sexual reproduction in animal.
Gamete: The reproductive cell which are produced by reproductive organ of animal
and plants during meiosis cell division is called gamete.It is haploid cell
.They are 2 types :
|
i)Male gamete |
ii)Female gamete |
|
i)It is smaller in size
than that of female gamete . ii)It is active iv)It is motile.(to move)
iii)For example:Spermi (n animal),Pollen grain(in
plant),antherizoid etc  |
ii)It is larger in size
than that of male gamete . iii)It is inactive iv)It is non-motile. iii)For example: Ovum(in animal),Ovual(in plant)
etc.  |
Zygote : The new cell
which is formed by the fusion of male and female gamete after fertilization is
called zygote .It is diploid cell .
Embryo: The development of early stage of zygote by mitosis
cell division is embryo .
Advantages
or significance of sexual reproduction :
i)It help for continuity of
life .
ii)The offspring produced by sexual reproduction are
genetically different ,so it help to bring out variaition in organism .
iii) The offspring produced by sexual rep. have better resistances .
Sexual reproduction in plants:
Flower :The reproductive organs of plants is known as flower .
Parts of flower :A complete flower(i.e. flower having sepal, petal, stamen, and pistil) is divided into 4 parts :
i)Calyx(Sepal): The outer most whorls(cover) of flower is calyx .it is small leaf like and green in colour .It help to
protect the flower during bud stage .
ii)Corolla(Petal): The 2nd outer most whorls of the flower is called corolla .It is bright
,coloured ,and attractive parts of flower.It help to
attract insects towards the flowers for pollination.
Caylax and corolla do not directly involve in the
reproduction .
iii)Androcium (stamens): The reproductive parts of plants is called
is androcium. It is divided into two parts i.e. filament
and anther and anther consist of pollen sac that produce male gamete
pollen grains .
iv)Gynocium(pistil or carpel): The female reproductive parts of flower is called gynocium.It is divided
into 3 parts i.e. stigma ,style ,and ovary and
ovary consist of ovules that contains
female gametes eggs and 2 polar nuclei.
Pollination: The process of transfer of pollen grains from anther to stigma of flower is called pollination .It two types
Fig. Cross pollination
|
i)Self pollination |
ii)Cross pollination |
|
i)The
process of transfer of pollen grains from the anther of flower to stigma of same flower or another flower of same plant is
called self pollination. iii)It
occurs only in bisexual flower. iii)It
requires only one plant . |
i)The
process of transfer of pollen grains from the anther
flower of one plant to the stigma of another plant of same species . pollination. iii)It
occurs in unisexual as well bisexual flower. iii).It
requires two or more than two plants.
|
Circulatory system : The group of organs working together to
circulate blood from heart to different parts of body and different
parts of body to heart is known as circulatory system .
Blood : The red liquid connective tissues which continuously in
the human body by carrying O2,CO2, hormone nutrients is
called blood .An average human body of
male adult consist of about 5/6 litre and female about 4/5 litre blood .
Structure
of blood :
It consist of 2 parts :
1)Blood cell
: The 45% solid parts of blood is called blood
cell . They are 3 types :
i)Red
blood cell (RBC) or Erythrocytes
ii)White
blood cell (WBC) Leucocytes
iii)Platelets or Thrombocytes
2.)Plasma : The 55% liquid
parts of blood is plasma .It consist of about 90% water and remaining 10%
consist of hormones ,protein ,glucose ,salt gases ,waste product etc.
Blood
cells :
A)Red blood cell (RBCs) or Erythrocytes :
Red coloured non nucleated ,circular blood cell is called red blood cell .One cubic milli meter (mm) blood contains about 45/ 50 lakhs of RBCs .Its life span is about 120 days .They are formed in the bone marrow and destroyed in liver and spleen . They do not contains nucleus but contains protein pigment of iron is called haemoglobin .Haemoglobin help to make blood red in colour and absorb oxygen from lungs .In a person lack of RBC or haemoglobin causes of Anemia and a person with anemia get tired due to no enough supply of oxygen in the cell.
Functions : i)It help to transport O2 from lungs to different parts of body
and CO2 from different parts of body to lungs.
B) Platelets or thrombocytes :
Small ,colourless, and circular blood
cell are called platelets .One cubic milli meter (mm) blood contains about 2-4 lakhs platelees.Its life span is about 2-3 days .They are formed in bone marrow and in
spleen . They does not contains nucleus and haemoglobin but release thread like fibres is called thromboplastin that help to clot the blood .
Blood vessels : The muscular tubular pipe that carry blood through the tissues and organs is called blood vessels .They are 3 types :
1.)Artery :-
The blood vessels which carry the oxygenated blood
from the heart to the all parts of body(except pulmonary artery) is called
artery .It has thick muscular and more elastic wall because blood remains in high pressure in it. They have no
valve. The thinner branch of artery is called
arterioles and thicker branch is called aorta.
2.)Vein : The blood vessels that carry
deoxygenated blood from different parts of body to heart (except pulmonary
vein) is called vein ).It has thin muscular wall because
blood remains in low pressure in it .They have valve
that control back flow of blood in it due to low pressure .The thinner branch of vein is called venules and thicker branch
is called venacava .
3.)Capillaries :-Very thin and fine network of blood vessels formed by the combination of arterioles and venules is called capillaries. It act act as connection between artery and vein. The exchange of O2 ,CO2 nutrients, and waste product takes place in capillaries .
Heart :
Heart is a conical muscular organ up from cardiac
muscles ,which is situated in the thoracic cavity between two lungs .
Heart is covered by double walled
membrane called pericardium membrane .The fluid
present in between two layers of pericardium membrane is called pericardial fluid . It help to protect heart from injury and absorb shock .
Structure of heart
Heart is divided into 4 chambered i.e. upper right chamber is called right auricle ,lower right chamber is called right ventricle, upper left chamber is called left ventricle and lower left chamber is called left ventricle
. It also consist of following
parts :
i)Venacava
:
ii)Aorta
:
iii)Pulmonary
artery .
iv) pulmonary vein :
v)Valves : The
small opening of the heart chambers that does not allow the blood in the opposite direction is called valve
.There are 4 valves in human heart . They are :
i)Tricuspid valve or right atrio
ventricular valve :
ii)Bicuspid valve or mitral valve or left atrio ventricular valve :
iii)Pulmonic valve
iv)Aortic valve :
Blood circulation : The process of the body
which help in transportation
nutrients,O2 and hormones to the different parts of body and
collect waste product to their respective organs is known as blood circulation .
1.)The walls of ventricle has thicker muscular wall than that auricles
,why?
Ans. The ventricles pumps the
blood into artery through aorta and requires
more pressure but auricles collect the blood from vena cava through the vein and requires
less pressure ,therefore the walls of ventricles has muscular wall than
that of auricles .
2.)The bleeding from the artery is very dangerous or the wall of artery is thicker than that of
vein ,why ?
Ans. The heart pumps the pure blood into artery with in
very high pressure so during bleeding pure blood flow out with very high pressure .Therefore the
bleeding from artery is very dangerous or wall of artery is thicker than that
of vein .
Photosynthesis:-The process of making food by green plants using carbon dioxide and water in the presence of sun light and chlorophyll is known as photosynthesis . The process of photosynthesis also can be written following ways :
Carbon dioxide + water→ Sun ligh/Chlorophyll Glucose (Starch) +oxygen + energy `+Heat
Raw materials essential for
photosynthesis
i.)Carbon dioxide – The source of carbon dioxide is
atmosphere for all terrestrial plants
but aquatic plants use dissolved CO2
water through gaseous exchange carried
out by stomata.
ii)Water – Water
is one of the raw material for photosynthesis .Plants absorbs water and dissolved minerals from soil the
help of roots. .
iii.)Sunlight – The green pigment present in green plants that traps solar energy form sun.
iv)Chlorophyll :-Chlorophyll is the green pigment
present in green parts of the plants mainly in leaves .Chlorophyll contains
chloroplast which help in photosynthesis .
A.)To demonstrate a green leaf contains starch .
Fig .Leaf
starch test
Method :
1.
Set up the equipment.
2.
Light the bunsen Burner and boil the water. When the
water has boiled add the first leaf
3.
Wait one minute for
the leaf to boil .
4.
Turn off the Bunsen Burner and take out the leaf.
5.
Dip the leaves in alcohol to them colourless
6.
Wash leaf in cold water .
7.
Put the leaves on a
petri dish and drop few drop of iodine on
the leave
8.
Observe, After about
two minutes the iodine will soak in and turn black if starch is present
9.
This show that leaves
contains starch as it turns black in iodine .
b.)EXPERIMENT TO SHOW THAT OXYGEN IS PRODUCED DURING PHOTOSYNTHESIS .
B)To prove that oxygen is produced during photosynthesis
following steps need to do
1.Place water plant i.e. Hydrila in a beaker
containing pond water.
2.Cover the plant with short stemmed funnel.
3.Invert the test tube full of water
and cover the stem of the funnel.
4.While placing the test tube,
ensure that the level of the water in beaker is above the level of stem of
funnel.
5.Expose the apparatus to the sunlight.
6.After few hours, gas bubbles will form and collect in the test tube.
6.Test the gas in the test tube.
7.A glowing splinter
bursts into the flame shows the presence of oxygen.
· Observation: Gas bubbles in a test tube.
Result:
Presence of oxygen.
Conclusion: Formation of gas bubbles prove that oxygen is produced by the
green plants during photosynthesis.
C.)Experiment to Prove Light is
Essential for Photosynthesis!
Apparatus and materials required:
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