B4 Cycles Flashcards
1
Q
nutrient cycling
A
- plants absorb nutrients from soil
- passed onto animals when plant eaten (feeding/digestion)
- plants lose material (leaves), organisms die
- decomposers release trapped nutrients
- many nutrients released back into soil & reabsorbed by plants
- some nutrients released into atmosphere
(Nutrients passed through biotic & abiotic components of ecosystem)
2
Q
What materials are cycled
A
- carbon
- nitrogen
- water
3
Q
Nitrogen cycle
A
- nitrogen exists in soil as nitrates dissolved in water
- water with nitrates taken up by roots & used to make proteins
- plant eaten, nitrogen compounds passed on to animal
- when plants/animals die, or faeces/urea released, compounds decomposed & released back into soil as ammonia (compound of nitrogen & hydrogen), reabsorbed by plant roots
- nitrogen-fixing bacteria live in roots of some plants & combine nitrogen from air with oxygen to form nitrates
- nitrates in water absorbed by plant roots again
4
Q
Why does nitrogen exist in soil as nitrates dissolved in water
A
- most organisms can only use nitrogen (to make DNA/proteins) when is it part of a compound (nitrate)
- so it can be absorbed by the plant roots
5
Q
What does the water cycle do
A
moves water & nutrients through atmosphere, soil, rivers, lakes, oceans & brings fresh water to people, animal, plants around world
6
Q
Water cycle
A
- precipitation
- rainwater runs of surface into oceans / percolation: trickles through gaps in soils/rocks
- water absorbed through plant roots
- evaporation/transpiration forms water vapour
- moist air rises & cools, water vapour condenses back into liquid water droplets, forming clouds
- repeat
7
Q
What is the carbon cycle
A
Process by which carbon cycled through atmosphere, living organisms (plants/animals) & fossil fuels
8
Q
The carbon cycle
A
- carbon dioxide in atmosphere
- absorbed by plants for photosynthesis
- plants eaten by animals, carbon transferred
- plants/animals die & decompose
- carbon in decaying matter/waste released as decomposers respire
- over millions of yrs, dead plants/animals become fossil fuels
- fossil fuels burnt & carbon released
- carbon dioxide also constantly released through respiration of animals
9
Q
How is carbon removed from atmosphere
A
- CO2 removed during photosynthesis in green plants / algae / phytoplankton
- converts CO2 & water into glucose & oxygen
- carbon part of plants extra biomass as used to make starch, fats, proteins which enables growth & development
- animals eat plants = carbon transferred, some used to produce fats/proteins in animals body
10
Q
How is carbon released back into atmosphere
A
- respiration: all living organisms respire to transfer energy from chemical stores in food = CO2 produced & released
- decomposition: plants/algae/animals die = decomposers break down remains, releasing CO2 as they respire
- burning fossil fuels: fossil fuels (coal, oil, natural gas) = store of carbon, release trapped carbon when burst
11
Q
Why do CO2 levels vary throughout day
A
- photosynthesis only takes place is light = CO2 only removed from atmosphere in day
- respiration carried out by all living organisms throughout day & night = CO2 released at relatively consistent rate
12
Q
Why has average carbon dioxide concentration increased significantly recently
A
Due to human activities:
- combustion of fossil fuels
- deforestation
= contributes to global warming
