B4.1 Ecosystems Flashcards
Give 3 molecules which are cycled through ecosystems
Oxygen, carbon dioxide and water
Briefly describe how water is cycled through an ecosystem
- Water evaporates from rivers and lakes and from transpiration
- Water condenses as clouds
- Water is returned through precipitation
Briefly describe how carbon dioxide is cycled through an ecosystem
- Carbon dioxide is fixed through photosynthesis
- Respiration releases carbon dioxide
- Decomposition releases carbon dioxide
- Combustion releases carbon dioxide
Briefly describe how nitrogen is cycled through an ecosystem
- Nitrogen is fixed by lightning, the Haber process and bacteria
- Denitrifying bacteria release nitrogen back to the atmosphere
Why is recycling in ecosystems necessary?
- To create a continuous flow of nutrients
- To provide fresh water
How would a decrease in oxygen availability affect the rate of decomposition?
- Lack of oxygen causes microorganisms to respire anaerobically
- Anaerobic decay is slower than aerobic decay
How would a change in temperature affect the rate of decomposition?
- A decrease in temperature slows the rate of the decomposition reactions
- A large increase in temperature will denature enzymes, slowing or even stopping decomposition
Give 4 abiotic factors that affect communities
- Light intensity
- Temperature
- Soil pH
- Moisture levels
Give 4 biotic factors that affect communities
- Number of predators
- Food availability
- Disease
- Human activity
What are the 3 types of interdependence?
Mutualism, parasitism and predation
What is parasitism?
- Where one organism lives on another and takes nutrients from the other organism
- This is beneficial to the parasite and detrimental to the host
What is mutualism?
- Two organisms depend on each other
- Both of the organisms benefit from the
relationship
Give 4 things animals compete for
- Mates
- Space
- Food
- Water
Give 4 things that plants compete for
- Light
- Water
- Minerals
- Space
What is a producer?
An organism that makes its own food
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 biomass?
The dry mass of all of the living organisms in an area
Why is dry mass used for biomass?
Because the wet mass varies as the amount of water in the organism varies
How do you calculate the efficiency of biomass transfer?
efficiency = (energy transferred / total energy available) × 100
Why are biomass transfers not 100% efficient?
Energy is lost through
- Egestion (removal of faeces)
- Excretion (removal of urine)
- Respiration
- The production of inedible bones and shells
How does the efficiency of biomass transfers affect the number of trophic levels in a biomass pyramid?
The less efficient the transfers, the fewer trophic levels and the fewer organisms in higher trophic levels
