IGCSE Biology Paper-2: Specimen Questions with Answers 188 - 189 of 203
Question 188
Question
MCQ▾The diagram shows a food web.
Which arrow does not show the direction of energy flow?
Choices
| Choice (4) | |
|---|---|
a. | D |
b. | B |
c. | C |
d. | A |
Answer
c.Explanation
- The energy flow in an ecosystem is from the producer level to the consumer level. At each trophic level, 80 to 90 % of energy is lost. Hence, the amount of energy decreases from the producer level to the consumer level that is unidirectional flow.
- Pyramid of energy is always upright because during the flow of energy from one trophic level to the next one, there always occurs a loss of energy.
- 10 per cent Law: Only 10 % of the total energy stored in a trophic level is transferred to the next trophic level of a food chain. Lindeman (1942) gave this law.
Question 189
Question
MCQ▾The diagram shows a cross-section of a flower.
Where does pollen formation takes place take place?
Choices
| Choice (4) | |
|---|---|
a. | Diagram B |
b. | Diagram A |
c. | Diagram D |
d. | Diagram C |
Answer
a.Explanation
Stamen
- Stamen is the male reproductive unit of angiosperms.
- Stamen consists of anther, connective and fi lament.
- The long and slender stalk called as fi lament and the terminal structure is known as anther.
- Typically, angiospermic anther is bilobed which is connected by connective and dithecous i.e.. , each lobe has two theca. The bilobed structure of the anther is tetrasporangiate (four sporangia) . In transverse section, it appears as four sided tetragonal structure consisting of two microsporangia in each lobe.
- Microsporangia develop into pollen sac filled with pollen grains.
- The number, form, and length of stamen vary from species to species.
