Ecosystems Flashcards
What is an ecosystem?
A set of interacting, interdependent biotic and abiotic components
What 2 types of factors can affect an ecosystem?
1- Biotic
2- Abiotic
What is a biotic factor?
A living factor
What is an abiotic factor?
A non-living factor
Name 5 abiotic factors
1- Light 2- Temperature 3- Water availability 4- Oxygen availability 5- Edaphic soil factors
Name 3 biotic factors
Competition for:
1- Food
2- Space
3- Breeding partners
Explain how light is an abiotic factor
Photosynthesis = success of plant species
Explain how temperature is an abiotic factor
- Enzymes = faster/slower metabolic reactions
- Migration + hibernation
Explain how water availability is an abiotic factor
Lack of water = water stress = death
Explain how oxygen availability is an abiotic factor
Aerobic respiration
Explain how soil factors are an abiotic factor
Different soil types have different sized particles which affects the organisms that can live there
What is biomass?
The mass of living material present in a particular place or in particular organisms
What is the easiest way of measuring biomass?
- Calculate dry mass
How do you calculate dry mass?
Discount water content by:
- Killing organism
- Place in oven at 80°C
Why might dry mass not be representative?
Only a small sample is taken to minimise destruction of organisms
What are the units of biomass?
- Land = g m -2
- Water = g k -3
What is the energy available at each trophic level measured in?
kJ m-2 yr-1
What is ecological efficiency?
The efficiency with which biomass of energy is transferred from one trophic level to the next
Why do producers only convert 1-3% of sunlight into biomass?
- Approximately 90% is reflected
- Other factors may limit PHS
- Some energy is lost for PHS reactions
What is gross production?
The total solar energy that plants convert to organic matter
How do you calculate net production?
Gross production - respiratory losses
Why do consumers convert a maximum of 10% biomass from food to their own organic tissue?
- Not all of the biomass is eaten
- Some energy is transferred as heat
- Some parts of an organism are indigestible
- Some energy is lost in excretory materials
How do you calculate ecological efficiency?
Energy after transfer/Energy before transfer x 100
What can humans do to maximise ecological efficiency?
- Remove predators
- Remove competition
- Provide food
- Provide optimum abiotic conditions
Describe the nitrogen cycle
- Nitrogen is fixed into ammonia by Rhizobium (roots) & Azotobacter (soil)
- Also by Haber process & lightning
- Ammonia undergoes nitrification into nitrites, by Nitrosomonas
- Nitrites undergo nitrification into nitrates, by Nitrobacter
- Nitrates undergo denitrification into nitrogen gas
- Or nitrates are taken up by plants & then to animals so plant & animal protein undergoes ammonification by decomposers into ammonia
Describe the carbon cycle
- CO2 photosynthesised into plant material
- Carbon is transferred to animals via feeding
- CO2 is returned to atmosphere via respiration
- When animals/plant die, the carbon is released by decomposition back to atmosphere
- If decomposition is prevented, carbon forms fossil fuels which, when combusted, release CO2 into atmosphere
What is primary succession?
Succession that occurs on newly formed land with no organic material
Describe the first stage of primary succession
Pioneer community
- Pioneer species colonises inhospitable land
Describe the second stage of primary succession
Intermediate community
- Weathering of bare rock produces basis of a soil
- Pioneer species decompose & release humus
- Soil can now support secondary colonisers
- Secondary colonisers decompose & release organic material so the soil can now support tertiary colonisers etc
What are 2 adaptations of the pioneer species?
- Ability to photosynthesise
- Tolerant to extreme environments
Describe the third stage of primary succession
Climax community
- Optimum conditions
- Environment rarely changes
- 1 or 2 species become dominant
What is plagioclimax?
The final stage of succession, when humans interrupt it
