Answer:
The force of surface tension in the lungs is so great that without something to reduce the surface tension, the airways would collapse after exhalation, making re-inflation during inhalation much more difficult and less effective. Collapse of the lungs is called alectasis.
Explanation:
Answer: Alveoli
Explanation: Alveoli of lungs are surrounded by extensive blood capillaries. The partial pressure of oxygen in the alveoli is higher than the blood entering the pulmonary capillaries, hence oxygen moves into the blood. Carbon dioxide in the lungs simultaneously diffuse out of the blood into the alveolar space.
Answer: The correct statements are 1 and 2:
1.Self-pollination occurs when the pollen from the anther is deposited on the stigma of the same flower, or another flower on the same plant.
2.Cross-pollination is the transfer of pollen from the anther of one flower to the stigma of another flower on a different individual of the same species.
Explanation:
Pollination is the transfer of pollen grains from an anthers to a receptive stigma. In most species of flowering plants, external agents bring about pollination. Also, flowers have evolved special structures and mechanisms to ensure successful pollination.
There are two types of pollination
--> Self pollination: This takes place when mature pollen grains from the anther of a flower fall on the stigma of the same flower or that of another flower on the same plant. This type of pollination brings the male gametes and egg cells of the same plant together. The resultant offspring show very little genetic variation.
--> Cross pollination: This occurs when mature pollen grains of a flower are transferred to the stigma of a flower of another plant of the same or closely related species. This brings the male gametes and egg cells of two different parent plants together. Therefore, there is greater genetic variation among the offspring.