Organisation of an ecosystem Flashcards
Define population
All the organisms of one species in a habitat
Define habitat
Place where an organism lives
Define community
The populations of different species living in a habitat
Define ecosystem
The interaction of a community of living organisms (biotic) with the non-living (abiotic) parts of their environment
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 amount of living material
What are trophic levels?
The stages in a food chain
What do the arrows in a food chain represent?
The direction of energy flow or biomass transfer
Describe a simple food chain
producer → primary consumer → secondary consumer → tertiary consumer
What is a producer?
An organism that makes its own food
What types of organisms are primary producers?
Photosynthetic organisms like green plants and algae that trap energy from the sun
What is a primary consumer?
An organism that feeds on producers
What is a secondary consumer?
An organism that 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 hunted and killed by another for food
Describe the pattern of predators and prey in a stable community
The number 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 via 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 the term ‘mean’?
The average number of organisms
How is the arithmetic mean calculated?
Sum of each number of each organism/the total number of each type of organism.
Describe how materials cycle through the living and non-living components of an ecosystem
- Organisms take in elements from their surroundings e.g. soil, air
- Elements are converted to complex molecules which become biomass
- Elements transferred along food chains
- Elements returned to environment during excretion and decomposition of dead organisms
Give 3 molecules which are cycled through ecosystems
- Oxygen
- CO2
- Water
Describe the carbon cycle
- CO2 removed from the atmosphere by green plants and algae through photosynthesis. Carbon used to make glucose which turns into carbs, fats and proteins that makes up the bodies of plants
- Plants and algae respire, returning some carbon to the atmosphere as CO2
- When plants and algae are eaten by animals, carbon becomes part of the carbs, fats and proteins of their bodies. It moves through the food chain
- Animals respire, returning some carbon to the atmosphere as CO2
- When plants, algae and animals die, detritus feeders and microorganisms feed on their remains. these organisms respire, returning some carbon to the atmosphere as CO2
- Animals produce waste that is broken down by detritus feeders and microorganisms
- Combustion of wood and fossil fuels releases CO2 back into the air
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
- Evaporation: water evaporates from the surface of land and bodies of water
- Transpiration: loss of water vapour from plants directly into the atmosphere
- Respiration: loss of water vapour from animals directly into the atmosphere
- Condensation: it rises into the air and condenses to form clouds
- Precipitation: water droplets in clouds get heavier and fall as rain, snow or hail
- 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 (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 e.g. plants use mineral ions for growth
What is meant by decomposition?
The breakdown of dead materials into simpler 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 two types of decomposition?
- Aerobic decomposition
- Anaerobic decomposition
What factors affect the rate of decomposition?
- Oxygen availability
- Temperature
- Moisture level
Why is oxygen required for decomposition?
Most decomposers require oxygen for aerobic respiration
How does availability of oxygen affect rate of decay?
- As oxygen levels increase, the rate of decomposition increases
- As oxygen levels decrease, the rate of decomposition decreases
Why can decomposition still occur in the absence of oxygen?
Some decomposers respire anaerobically.
However, the rate of decomposition is slower as anaerobic respiration produces less energy
How does soil water content affect the rate of decomposition?
Decomposers require water to survive:
- In most conditions, the rate of decay 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 degrees Celsius (optimum temperature)
- Lower temperatures, enzymes work too slowly, rate decreases
- High temperatures, enzymes denature, decomposition stops
What is compost?
The nutrient-rich product of the rapid decay of waste biological material (dead plants and animal waste) in optimum conditions set by gardeners and farmers.
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.
Describe how environmental conditions affect communities
- Environmental conditions e.g. temperature, soil pH, light intensity affect the abundance and distribution of organisms within communities
- e.g. rising global temperatures have been linked to the extinction of frog species
How can different temperatures be bad for certain communities?
- If the temperature is too low, growth will be slower as organisms will use more energy to stay warm
- If the temperature is too high, organisms can die and water will become limited as evaporation increases
How can changes in water levels affect ecosystems?
- Animals may have to migrate to find water.
- Melting ice caps may destroy the habitats of some animals (either animals living in icy regions or by sea level rise).
How can atmospheric gases affect ecosystems?
- Some organisms cannot survive when certain gases are present
- Polluted water can cause illness to animals that drink it
What detrimental impacts can sulphur dioxide have on the environment?
- Formed when fossil fuels containing impurities are burnt
- Sulphur dioxide can dissolve in water to form acid rain which can erode buildings and pollute water sources
What detrimental impacts can carbon monoxide have on the environment?
- Carbon monoxide is formed from the incomplete combustion of fossil fuels
- Carbon monoxide binds irreversibly to haemoglobin which prevents it from carrying oxygen
- Too much exposure can cause unconsciousness and death
Name 5 greenhouse gases
- Water vapour
- Carbon dioxide
- Nitrous oxide
- Methane
- CFCs
Give 3 human activities that contribute to greenhouse gases
- Burning fossil fuels
- Deforestation
- Large scale livestock farming
How do greenhouse gases lead to global warming?
- Greenhouse gases allow heat from the sun to enter the atmosphere.
- The gases act as a ‘blanket’ and trap the heat in the atmosphere.
State 3 negative consequences of global warming
- Sea level rise caused by melting icebergs.
- Disrupted farming and agriculture.
- Increased spread of diseases in warmer climates.
