B4 - Community-level systems Flashcards
What is an ecosystem?
An ecosystem is made up of all the living organisms and physical conditions in the area. The organisms within an ecosystem are called a community and the place they live is a habitat. The total number of organisms of each species is a population.
What are producers, consumers and decomposers?
Producers - organisms that make their own food via photosynthesis
Consumers - organisms that cannot make their own and have to eat other organisms to gain energy
Decomposers - a special group of consumers that gain energy by by feeding on dead or decaying material
What are food chains, food webs and trophic levels?
Food chains - displays what an organism eats
Food webs - a series of interlinked food chains and can display organisms eating multiple other organisms
Trophic level - The position in a food chain, biomass decreases with each trophic level
What are biotic and abiotic factors and how these affect communities?
Biotic factors are the living factors
Abiotic factors are the non-living/physical factors such as:
- Light intensity - needed for photosynthesis so generally the more light the higher the success of plants
- Temperature - has a big effect on the rate of enzymes that control metabolic reactions
- Water level - For most plants and animals a lack of water means death as it’s needed for photosynthesis, makes up most of blood plasma
- Soil pH - This affects the availability of certain minerals in soil and biological activity
What is competition and what do plants and animals need to survive?
Plants and animals need resources to survive however if these are limited they will have to compete for these resources and may result in weaker organisms dying out or leaving that area.
Plants need :
- light, water, minerals, space, carbon dioxide
Animals need :
- food, water, breeding partners, space, shelter
What is interdependence and what are the three main types of ecological relationships?
Interdependence is how organisms depend on each other within a community.
Predator-prey relationship - If the population of prey increase there is a larger food supply for the predators. This can support more predators, so more offspring survive. More predators decreases the food supply of prey so the predator population decreases. This allows the prey population to increase and the cycle starts again.
Mutualistic relationship - When both organisms benefit
Parasitical relationship - Only one organism benefits(the parasite). The other organism suffers(the host).
How to calculate biomass for a trophic level?
1) Take a sample of organisms at each trophic level
2) Kill the organisms and measure the average dry mass
3) Multiply dry mass by number of organisms
Why does biomass decrease at each trophic level?
- Not all the energy from the sun is converted into the plants biomass as most is reflected, some is used for respiration.
Only about 10% of the biomass is converted into new biomass in the consumer, biomass is lost because:
- Not all the organism is eaten
- Some of the biomass is used for respiration
- Some parts of cannot be digested and are removed from the body via egestion
- Waste products are lost through excretion
What are the 3 types of bacteria in the nitrogen cycle?
Nitrifying bacteria - Converts ammonia to nitrates
Denitrifying bacteria - Converts nitrates into nitrogen gas
Nitrogen fixing bacteria - Converts nitrogen gas into nitrates
Describe the carbon cycle:
The carbon cycle is the process by which carbon is cycled through the atmosphere, plants, animals and the Earth.
Carbon dioxide is removed from the atmosphere via photosynthesis in green plants and converts carbon dioxide and water into glucose and oxygen. Glucose is a simple sugar and can be used to make complex carbohydrates which enables plants to grow and develop and the carbon is now part of their extra biomass. This can then be transferred to animals when they eat plants.
Carbon is released back into the atmosphere through:
- burning fossil fuels
- respiration
- decomposition
Why do carbon dioxide levels vary?
- They vary throughout the day as photosynthesis only takes place in the light so carbon dioxide is only removed from the atmosphere during the day. However respiration is continuous so carbon dioxide is always being released into the atmosphere relatively constantly.
Over time carbon dioxide levels have increased mainly due to human activities such as burning fossil fuels and deforestation.
What are detrivores and decomposers?
- Detrivores are small animals that speed up decomposition by shredding organic material into very small pieces so that there is a larger SA for decomposers to work on
- Decomposers are microorganisms that break down/decay dead organic material and can also break down animal waste. Through decomposition nutrients are released which can then be recycled
How do decomposers release nutrients?
Bacteria and fungi release enzymes which break down substances in organic matter. The bacteria can then absorb the soluble nutrients and use them for growth and an energy store. The nutrients are passed on if the bacteria is eaten or if the nutrients are released back into the environment.
