Effects of Light on organisms(biology

1. Effect of light on protoplasm: sun rays may penetrate such covers and cause excitation, activa­tion, ionization and heating of protoplasm of different body cells. Ultraviolet rays are known to cause mutational changes in the DNA of various organisms.
2. Effect of light on metabolism:The metabolic rate of diffe­rent animals is greatly influenced by light. The increased intensity of light results in an increase in enzyme activity, general metabolic rate and solubility of salts and minerals in the protoplasm. Solubi­lity of gases however, decreases at high light intensity. Cave dwe­lling animals are found to be sluggish in their habits and to contain slow rate of metabolism.
3. Effect of light on pigmentation:Light influences pigmenta­tion in animals. Cave animals lack skin pigments. If they are kept out of darkness for a long time, they regain skin pigmentation. The darkly pigmented skin of human inhabitants of the tropics also indicates the effect of sunlight on skin pigmentation. The skin pig­ment’s synthesis is dependent on the sunlight.

Light also determines the characteristic patterns of pigments of different animals which serve the animals in                sexual dimorphism and protective colouration. Animals that dwell in the depths of the ocean where the                        environ­ment is monotone, though pigmented do not show patterns in their colouration.

4. Effect of light on animal movements:Some animals move in response to light called phototaxis. Positively phototactic animals such as Euglena, move towards the source of light, while negatively phototactic animals such as planarians, earthworms, slugs move away from the source of light.
5. Growth response such as phototropism
6. Photoperiodism and biological clocks: this regulates flowering in pants

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Dr. Bbosa Science