Question

open - ended questions: answer the following questions in complete sentences. 1. explain why there are usually fewer organisms at the top of an ecological pyramid than at the bottom. 2. describe what would happen to an ecosystem if the producer level suddenly decreased. 3. give an example of an ecosystem and briefly describe what its pyramid of numbers might look like.

Explanation:

1. In an ecological pyramid, energy transfer is inefficient. Only about 10 - 20% of energy is passed from one trophic level to the next. Producers at the bottom capture energy from the sun and form the base of the pyramid. As we move up the trophic levels, there is less available energy, so fewer organisms can be supported at the top.
2. If the producer level in an ecosystem suddenly decreased, it would lead to a shortage of food and energy for primary - consumers. This would cause a decline in the population of primary - consumers. Subsequently, secondary - consumers that rely on primary - consumers would also be affected, leading to a cascading effect throughout the ecosystem. The pyramid of numbers would show a reduced base, and the numbers at higher levels would also decrease, potentially making the pyramid more narrow and less stable.
3. An example of an ecosystem is a grassland ecosystem. Producers like grasses form the base of the pyramid. Primary - consumers such as grasshoppers feed on the grasses. Secondary - consumers like frogs eat the grasshoppers, and tertiary - consumers like snakes eat the frogs. The pyramid of numbers in a grassland ecosystem would have a large number of grasses at the base, fewer grasshoppers, even fewer frogs, and the least number of snakes at the top.

Answer:

1. There are usually fewer organisms at the top of an ecological pyramid than at the bottom because energy transfer between trophic levels is inefficient, with only about 10 - 20% of energy being passed on, so less energy is available to support organisms at higher levels.
2. If the producer level in an ecosystem suddenly decreased, there would be a shortage of food for primary - consumers, leading to a decline in their population, and this would have a cascading effect on higher - level consumers, making the pyramid of numbers more narrow and less stable.
3. A grassland ecosystem is an example. Grasses are producers, grasshoppers are primary - consumers, frogs are secondary - consumers, and snakes are tertiary - consumers. The pyramid of numbers has a large number of grasses at the base, fewer grasshoppers, even fewer frogs, and the least number of snakes at the top.