Section 8- Ecology and the Environment, P2 Flashcards
Define biodiversity:
Biodiversity is the variety of different species of organisms on Earth, or within an ecosystem.
Why is high biodiversity important?
It makes sure that ecosystems are stable because different species depend on each other for things like shelter and food. Different species can also help to maintain the right physical environment for each other.
What is affecting biodiversity?
Lots of human actions, including deforestation, pollution and global warming.
How can you use quadrats to study distribution across a habitat?
Sometimes abiotic factors change across a habitat.
-to find out how organisms are distributed across a habitat you can use quadrats layed out in a line, forming a belt transect
Explain a practical for how you can use belt transects to study distribution across a habitat:
- mark out the line in the area you want to study
- collect data along the line using quadrats placed next to each other or at regular intervals
- count all the organisms of the species you are interested in or estimate percentage cover or you could record other data such as mean height, light intensity(using a light meter)
- repeat
- plot graphs to see if the changing abiotic factor is correlated with a change in distribution of the species you’re studying
What is the nitrogen cycle?
Nitrogen is recycled in the nitrogen cycle
- it’s very unreactive so it can’t be used by plants or animals directly
- nitrogen is needed for making proteins for growth
How do plants get nitrogen?
Plants get nitrogen from the soil
- nitrogen in the air has to be turned into nitrogen compounds before plants can use it
- animals can only get proteins by eating plants
How does nitrogen get from the air into nitrogen compounds in the soil which plants can use?
Nitrogen fixation happens in two main ways:
- lightning: there’s so much energy in a bolt of lightning that it’s enough to make nitrogen react with oxygen in the air to form nitrates
- nitrogen- fixing bacteria: in the soil and in the roots(nodules) of some plants
What are the four types of bacteria involved in the nitrogen cycle?
DECOMPOSERS- break down proteins and urea and turn them into a ammonia which forms ammonium compounds in the soil
NITRIFYING BACTERIA- turn ammonium into nitrates (nitrification)
NITROGEN-FIXING BACTERIA- turns atmospheric nitrogen into nitrogen compounds
DENITRIFYING BACTERIA- turns nitrates back into nitrogen gas
What are the effects of deforestation?
LEACHING
DISTURBING THE BALANCE OF CARBON DIOXIDE AND OXYGEN
SOIL EROSION
DISTURBING EVAPOTRANSPIRATION
How can deforestation cause leaching?
- trees take up nutrients from the soil, before they can be leached and return them back to the soil when the leaves die
- when trees get removed nutrients get leached and don’t return to the soil leaving infertile soil
How can the balance of carbon dioxide and oxygen be disturbed by deforestation?
- forests take up carbon dioxide by photosynthesis and store it in wood
- when trees are cut down and burnt this disturbs the carbon cycle and contributes to global warming
- fewer trees lead to less photosynthesis taking place so less oxygen is released, causing the levels of oxygen in the atmosphere to decrease
How can deforestation cause soil erosion?
- tree roots hold the soil together
- when trees are removed, soil can be washed away by the rain leaving infertile ground
How can disturbing evapotranspiration be caused by deforestation?
- evapotranspiration includes both water evaporating from the earths surface and from plant transpiration
- this water falls back to earth as rain
- when trees are cut down this leads to less evapotranspiration which can make the local climate drier
