10.2 energy transfer through ecosystems

Question 1

what is Gross primary productivity in plants?

Answer 1

rate at which light from the Sun catalyses the production of new plant material

Question 2

what is Net primary productivity?

Answer 2

the material produced by photosynthesis stored as new plant body tissues

Question 3

the nitrogen cycle

Answer 3

1- proteins in the soil from urea, faeces and dead matter are decomposed to form ammonium compounds
2- these ammonium compounds are then oxidised by nitrifying bacteria that convert them into nitrates

1- nitrogen fixing bacteria in the soil can convert nitrogen from the soil into ammonia
2- this ammonia is then converted into nitrates by nitrifying bacteria

1- legumes (peas, beans) have nodules on their roots that are full of nitrogen-fixing bacteria

(denitrifying bacteria use nitrates as an energy source and turn nitrates into nitrogen gas)

Question 4

the carbon cycle

Answer 4

1- CO2 is removed from the air by green plants in the process of photosynthesis
2- when plants are eaten by animals, the carbon is passed on and becomes part of the animals bodies

1- when green plants respire they also return some CO2
2- when animals respire they release CO2 to the environment
3- when plants and animals die their bodies are broken down by the action of decomposers
4- CO2 is also released by the combustion of anything that has been living is burnt (wood, straw and fossil fuels)

Question 5

what are examples of carbon sinks?

Answer 5

• bodies
• soil (humus)
• rocks
• limestone
• fossil fuels
• ocean