Question

5. Which is each of the following scenarios an example of: bottom-up control or top-down control?

a. Adding nitrogen to grassland results in an increase in grass production (biomass), grasshopper numbers and bird numbers.

b. Biomanipulation

6

Mainland

Examine the visual above.

1. Which island has the greatest number of species?

2. Which island has the lowest extinction rate?

Answer 1

Answer 5: (a) Adding nitrogen to grassland results in an increase in grass production (biomass), grasshopper numbers and bird numbers is an example of bottom up control. Control of trophic structure/ecosystem has two models: Top down Model and Bottom up model. Bottom up model is an example of abiotic control in which inorganic nutrients are added to the soil which help in further increasing the population at each specific trophic level. While Top down model is an example of biotic control in which the population of the individuals at highest trophic level is more which control the population at lower trophic level. So, the given example is of bottom up control.

(b) Biomanipulation is the process in which we deliberately add or remove the predator (at higher trophic level) which further control the ecosystem. So, Biomanipulation is the example of top down control.

Answer 6: This question is based on Island Biogeography theory which stated that the species diversity of an island is decided by its size and distance from mainland. It also depend on rate of immigration and rate of extinction. Smaller Island will have more rate of extinction and least distantly Island will have maximum rate of immigration.

Explained in the Handwritten solution:

Solution: 6 Based on Island Biogeography Theory : Mainland Distance © Nearest to mainland a Island A. 0 Largest Island - Island 'A'. Larger the island, more heterogenesity in terms of habitat will be there, so more will species diversity will be there. L Effect to * Lesser the distance from mainland more will - the chances of immigration. 1 . So, more will be the species divercity. 1. a) So, Island in' will have greatest number of species. because of the least distance and larger size. b) Smaller Island which has maximum species divenity will have less resources availability because there will be more competition among species (Intra as well as Interspecies). So, more extinct action chances will be there. o Island i will have more extinction chances than a because - it has smaller in size. o As Island c' isi smallest in size but it is maximally at - distance it has lowest immigration. So; island "c' will have lowest extinction rate.