B2c Flashcards
What happens when animals and plant die and decay?
The elements in their bodies are recycled.
What are many soil bacteria and fungi?
Decomposers, which decay dead organism.
What is the importance of the decay process?
It makes elements available again to living organisms.
What happens as animals and plants grow?
They take In chemicals and incorporate elements from these into their bodies.
What are two of the most important elements required?
Carbon and nitrogen.
What is carbon taken up by plants as?
Carbon dioxide.
Why does recycling of nutrients take longer in waterlogged or acidic soils than it does in well drained natural soils?
It takes longer in waterlogged soils because bacteria and fungi that decompose organic material usually need oxygen to respire and produce energy. Waterlogged soils don’t have much oxygen - so the decomposers have less energy and work more slowly.
It takes longer in acidic soils because extremes of pH slow down the reproduction of decomposers or kill them.
How is carbon recycled in nature?
It is ‘powered’ by photosynthesis.
In photosynthesis plants convert the carbon from carbon dioxide into sugars, removing it from the air.
Eating passes the carbon compounds in the plant along to animals in a food chain or web.
Plant and animal respiration while the organisms are alive releases carbon dioxide back into the air.
Plants and animals eventually die and decay. They’re then broken down by bacteria and fungi in the soil which release carbon dioxide back into the air by respiration as they break down the material.
Material from dead plants and animals can form fossil fuels and when these are burned carbon dioxide is released back into the air.
How is carbon dioxide recycled in the sea?
Marine organisms make shells made of carbonates.
When these organisms die the shells fall to the ocean floor and eventually form limestone rocks.
The carbon in these rocks returns to the air as carbon dioxide, during volcanic eruptions or when the rocks are weathered down.
Oceans can also absorb large amounts of carbon dioxide, acting as huge stores of carbon called ‘carbon sinks’.
What is nitrogen taken up by plants as?
Nitrates
What is the abundance of nitrogen in the air?
78%
Why can’t nitrogen be used directly by plants or animals?
It is very unreactive.
How is nitrogen recycled in the air?
Plants take in nitrates from the soil to make protein for growth.
Nitrogen compounds are then passed along food chains and webs as animals eat plants.
Decomposers break down proteins in rotting plants and animals, and urea in animal waste, into ammonia. This returns the nitrogen compounds to the soil.
How is nitrogen recycled in nature?
Soil and bacteria act as decomposers and decompose proteins and urea and turn them into ammonia.
The conversion of ammonia to nitrates is by nitrifying bacteria.
Denitrifying bacteria turns nitrates to nitrogen gas.
Nitrogen fixing bacteria turns atmospheric nitrogen into nitrogen compounds that plants can use . This happens by lightning - there’s so much energy in a lighting bolt that it’s enough to make nitrogen react with oxygen in the air to give nitrates. Also by living in root nodules on plants like legume plants. This is why legume plants are so good at putting nitrogen back into soil. The plants have a mutualistic relationship with the bacteria - the bacteria get food from the plant and the plant gets nitrogen compounds from the bacteria to make into proteins.
