Science [3 Mark Questions]

	Aerobic Respiration	Anaerobic Respiration
1.	Method: It is the common method of respiration.	It occurs permanetly only in a few organisms. In other it may occur as a temporary measure to overcome shortage of oxygen.
2.	Steps: It is completed in 3 steps- glycolysis, krebs cycle and terminal oxidation.	There are two steps- glycolysis and anaerobic breakdown of pyruvic acid.
3.	Oxygen: It requires oxygen.	Oxygen is not required.

Blood circulation in human heart is called double circulation as blood passes twice through the heart in order to complete one cycle-once through right side as deoxygenated blood and once through left side as oxygenated blood. Deoxygenated blood passes to lungs. It returns to left side as oxygenated blood. Oxygenated blood is supplied to different parts of the body. It returns to right side of the heart as deoxygenated blood.

Green plants are autotrophs are that use light as source of energy, carbon dioxide as chief carbon source and water as electron donor to fix the atmospheric carbon dioxide into organic compounds (carbohydrates). The carbohydrates which are not immediately consumed by plants are stored as starch.Since autotrophs are the only organisms that can fix the atmospheric carbon dioxide into organic compounds, these organisms occupies first trophic level in food chain and serve as source of food and energy for all other organisms of higher trophic levels (heterotrophs/ consumers).
Hence, in absence of these plants, whole functioning of whole ecosystem will come to hault due to lack of food and energy source for consumers (herbivores, carnivores and omnivores)