Question

QUESTION 9

1. The largest impact that humans have on the Nitrogen cycle is due to:

		combustion of fossil fuels
		deforestation
		domestication of animals
		production and application of synthetic fertilizers

3 points   

QUESTION 10

1. The C:N ratio of plant litter is important because litter with a

		high C:N ratio does not contain enough nitrogen for decomposers, resulting in immobilization
		low C:N ratio cannot be utilized by most organisms without extra carbon available
		low C:N ratio does not contain enough nitrogen for decomposers, resulting in immobilization
		high C:N ratio cannot be utilized by most organisms without extra carbon available

3 points   

QUESTION 11

1. The end of the Permian period was characterized by a mass extinction of

		marine invertebrates
		small mammals
		large mammals
		dinosaurs and other large reptiles
		birds

3 points   

QUESTION 12

1. Internal nutrient cycling

		does not include mineralization of organic matter; it only involves transformation of organic matter from one form to another
		is the cycling of carbon between ecosystems and atmosphere
		is relatively more important in tropical climate than in the temperate climate
		is the re-translocation of nutrients within a single organism, for example from leaves to roots of a tree

3 points   

QUESTION 13

1. Decimation of blue crab populations in Massachusetts (select all that apply):

		led to the decline of nitrogen fixation in salt marshes
		caused destruction of salt marshes leading to lower denitrification rates
		caused the decline of herbivorous crabs leading to lower ammonification rates
		lowered nitrification rates due to the widening of soil anoxic zone

Answer 1

Question 9: combustion of fossil fuels

Because the main activity of human impact the nitrogen cycle is fossil fuel combustion. The combustion of fossil fuel releases nitric oxides into air and combine with other elements produces acid rain or smog.

Question 10 : High C:N ratio does not contain enough nitrogen for decomposers, resulting in immobilization.

Question 11: marine invertabrates

Because permian period is between 286-245 million years ago. End of permian period was characterized by mass extension of many sea animals.

Question 12: is the retranslocation of nutrients within a single organism, for example from leaves to roots of a tree.

Because internal nutrient cycle is the cycling of nutrients through components of ecosystem.