Photosynthesis:

Definition:
Photosynthesis is a process in which plants manufacture their food (simple carbohydrates) in the presence of chlorophyll and sunlight by the combination of carbon dioxide and water.

Raw Material For Photosynthesis:
i) Carbon dioxide: Taken from air
ii) Water: Absorbed by roots from soil
iii) Sunlight: From Sun
iv) Chlorophyll: green pigment present in leaves

By-Products Of Photosynthesis:
i) Carbohydrates (simple sugar): used by plants as a food material and excess of it is converted into starch
ii) Oxygen: Released into air

Importance Of Photosynthesis:
i) Major process of food production in plants
ii) Utilization of CO2 of the atmosphere and liberation of oxygen
iii) Important in reducing CO2 of the atmosphere which is dangerous for the human beings as well as animal health.

Pollination:

Definition:
Pollination is the phenomenon of transfer of pollen from male reproductive organ (anther) to female reproductive organ (stigma) in flowering plants through biological or physical agency.

Types Of pollination:
There are two types of Pollination

i) Self-Pollination:
In this type of pollination pollens are transferred to the stigma in the same flower. Some plants are by nature self-pollinated as wheat and grasses.

ii) Cross Pollination:
In this type the pollen grains are transferred from the anther of one flower to the stigma of another flower. The cross pollination is considered and advantageous to the plant as the seeds produced by cross-pollination are usually greater in number and the plant germinated from them are superior in vigour, height and weight.

Vehicles For Pollination:
Vehicles for pollination are animals, water, wind and insects. Therefore cross pollination may be:
a) Entomophily-by insects
b) Anemophily-by wind
c) Hydrophily-by water
d) Zoophily-by animals

Importance Of Pollination:
• Vital process for reproduction in plants
• Reproduction is carried out by reproductory organs of plants due to pollination
• It is the process by which seeds are produced.

Fertilization:

The fusion of male and female gametes is called fertilization.

Types Of Fertilization:
Following are the major types of fertilization:
i) External Fertilization
ii) Internal Fertilization
iii) Self-Fertilization
iv) Cross-Fertilization

External Fertilization:
• This type of fertilization is generally observed I simple aquatic animals.
• In such animals both ova and sperms are released into the water where fertilization occurs.
• In terms of evolution external fertilization is of primitive type and is not better biologically as compared to internal fertilization.

Internal Fertilization:
• In the internal fertilization the females keep ova inside their bodies and males deposit sperms within the tube of reproductive tacts of females.
• For all land animals internal fertilization is almost must because sperms are quickly killed by dehydration.
• In terms of evolution internal fertilization is highly evolved and much better biologically as compared to external fertilization.

Self-Fertilization:
• Self-fertilization occurs within the same animal.
• It is that fertilization in which sperms are used by the ovaries of same animal e.g. Tapeworm

Cross-fertilization:
• Cross-fertilization is the process in which sperms of one animal are transferred into the body of another animal e.g. Earthworm.