Organisation of an ecosystem Flashcards
Define habitat
The place in which an organism lives.
Define population
A species that occupy the same habitat.
What do food chains show?
Food chains show the feeding relationships of different organisms and the flow of energy between the organisms.
Define biomass
The total dry mass of living material/organisms in an area.
Define community
Populations of different species interacting in a habitat.
What are trophic levels?
The stages in a food chain.
What do arrows in a food chain represent?
The direction of biomass transfer.
Describe a simple food chain
Producer - Primary consumer - Secondary consumer - Tertiary consumer
What is a producer?
An organism which makes its own food.
What types of organisms are primary producers?
Photosynthetic organisms like green plants and algae that trap light energy from the sun.
What is a primary consumer?
An organism that feeds on producers.
What is a secondary consumer?
An organism which feeds on primary consumers.
What is a tertiary consumer?
An organism that feeds on secondary consumers.
What is a predator?
A consumer that kills and eats other animals.
What is prey?
An animal that is killed and eaten by another animal.
Describe the pattern of predators and prey in a stable community
The numbers of predators and prey rise and fall in cycles.
Why are producers the first trophic level?
- Producers provide all biomass for the food chain (production of glucose from photosynthesis).
- The rest of the food chain involves the transfer of this biomass.
What piece of apparatus is used to measure the abundance and distribution of organisms in an area?
Quadrat.
What piece of apparatus is used to study the distribution of organisms across a gradient?
Belt transect.
When considering the abundance of organisms, what is meant by ‘mean’?
The average number of organisms.
How is the arithmetic mean calculated?
Sum of each number of each organism / total number of each type of organism
When considering the abundance of different organisms, what is meant by ‘mode’?
The most populous organism.
When considering the abundance of organisms, what is meant by the term ‘median’?
The organism that represents the middle value when the numbers of each organism are arranged from lowest to highest.
Describe how materials cycle through the living and non-living components of an ecosystem
- Organisms take in elements from their surroundings such as from the soil and air.
- Elements converted to complex molecules which become biomass.
- Elements transferred along a food chain.
- Elements returned to environment during excretion and decomposition of dead organisms.
Give 3 molecules which are cycle through ecosystems
- Oxygen.
- Carbon dioxide.
- Water.
Describe the carbon cycle
- Plants fix carbon dioxide into organic molecules during photosynthesis.
- The organic carbon-containing molecules are passed onto organisms that eat the plants.
- Carbon dioxide is released back into the atmosphere by respiration from animals and plants.
- Carbon dioxide is released from respiration of decomposers that break down dead organisms.
- Dead organisms that are not broken down turn into fossils over millions of years, which can be burnt for fuel releasing carbon dioxide into the atmosphere.
Why is the carbon cycle important?
Carbon-containing molecules such as glucose are important for living organisms to grow and provide energy for vital functions within cells.
Describe the water cycle
- Water from lakes and oceans evaporate.
- The evaporated water condenses into clouds and returns to earth as precipitation.
- The water from precipitation is useful for life on land.
- The water then returns to rivers and oceans through surface runoff.
Why is the water cycle important?
Living organisms require water and the water cycle provides organisms on land with a continuous supply of water.
Why are microorganisms important for the cycling of materials through an ecosystem?
Microorganisms such as bacteria and fungi return carbon to the environment by releasing carbon dioxide through respiration while they decompose dead matter. The decomposition of dead matter in soil returns mineral ions to the environment for other organisms to use (using mineral ions for growth).
What is meant by decomposition?
The breakdown of dead materials into simple organic matter.
How do decomposers break down dead matter?
Decomposers release enzymes which catalyse the breakdown of dead material into smaller molecules.
What are the 2 types of decomposition?
- Aerobic decomposition (with oxygen).
- Anaerobic decomposition (without oxygen).
What factors affect the rate of decomposition?
- Oxygen availability.
- Temperature.
- Water content.
Why is oxygen required for decomposition?
Most decomposers require oxygen for aerobic respiration.
How does the availability of oxygen affect the rate of decomposition?
- As oxygen levels increase, the rate of decomposition increases.
- As oxygen levels decrease, the rate of decomposition decreases.
Why can decomposition still occur the absence of oxygen?
Some decomposers respire anaerobically.
However, the rate of decomposition is slower as anaerobic respiration releases less energy.
How does soil water content affect the rate of decomposition?
Decomposers require water to survive:
- In moist conditions, the rate of decomposition is high,
- In waterlogged soils, there is little oxygen for respiration so the rate of decomposition decreases.
Why does decomposition require water?
Water is required for the secretion of enzymes and absorption of dissolved molecules.
How does temperature affect the rate of decomposition?
Decomposers release enzymes:
- Rate highest at 50°C (optimum temperature for enzymes).
- Lower temperatures, enzymes work too slow, rate decreases.
- High temperatures, enzymes denature decomposition stops.
How is the rate of change calculated when considering decay of biological material?
Rate of change = Change in value / change in time
What is compost and manure?
Compost is decayed organic matter from dead plants and is nutrient-rich.
Manure is animal waste and is nutrient-rich.
How is compost used?
Used as natural fertiliser to promote growth of crops or garden plants.
Describe how biogas generators work
Biogas generators provide methane gas for fuel through anaerobic decomposition that occurs in animal waste.
