Organisms and their environment Flashcards
What is the sun to biological systems?
The Sun is the principal source of energy input to biological systems
Describe the flow of energy of living organisms
The light energy from the Sun is harnessed by producers (plants and some bacteria) which convert light energy into chemical energy. Some of this energy is used in carrying out life processes but the stored chemical energy is then passed on to the primary consumer through feeding. Some is used up in life processes but when it is consumed by secondary and then tertiary consumers the energy is passed further up the food chain. At every trophic level (producers, consumers, decomposers), energy is lost as heat to the surroundings during metabolic processes like respiration. The energy is returned to the environment through decomposition.
Food chain definition
shows the transfer of energy from one organism to the next, beginning with a producer
Food web definition
a network of interconnected food chains
How to construct a food chain?
- Identify the producer first (normally a plant)
- Add the primary consumer next
- Add secondary consumer and then tertiary consumer (add quaternary if there)
🌟 Arrows go from nutrient source to predator
Producer definition
an organism that makes its own organic nutrients, usually using energy from sunlight, through photosynthesis
consumer definition
an organism that gets its energy by feeding on other organisms
- Consumers may be classed as primary, secondary, tertiary and quaternary according to their position in a food chain
Herbivore definition
an animal that gets its energy by eating plants
Carnivore definition
an animal that gets its energy by eating other animals
Decomposer definition
an organism that gets its energy from dead or waste organic material
Trophic level definition
the position of an organism in a food chain, food web or ecological pyramid
- Producer is trophic level one, quaternary consumer is trophic level five
Why do most of the changes in populations of animals and plants happen?
Most of the changes in populations of animals and plants happen as a result ofhuman impact- either byoverharvesting of food speciesor by theintroduction of foreign species to a habitat
How does overharvesting affect the food chains/web?
Overharvesting occurs when humans remove a large number of individuals from a species, such as fish or certain animals, at a rate faster than they can reproduce. If a species in a food chain is overharvested, it creates an issue as the predators that rely on them for food may struggle to find enough food, leading to a decline in their populations and it leads to an increase in their nutrient source as they have less predators
How does the introduction of foreign species affect the food chains/web?
Introduction of foreign species into a habitat creates competition for resources which disrupts food chains and food webs. They may have no natural predators in the new environment, allowing them to reproduce rapidly and dominate the ecosystem leading to a decline in native species
Pyramid of number
- Tells us the population numbers of organisms in different trophic levels
- Thewidth of the boxindicates thenumber of organismsat that trophic level
- A pyramid of number doesn’t always have to be pyramid shaped (This is because it doesn’t account for thesize of the organism, different sizes have different energy requirements)
🌟 General rule larger organisms tend to have smaller populations
When drawing remember that you can’t change the trophic levels. Trophic level 1 is always on the bottom
Pyramid of biomass
- A pyramid of biomass shows the total dry mass of living organisms (biomass) at each trophic level in a food chain.
- Pyramids of biomass are always pyramid shaped because there must always be more biomass in the previous trophic level to support the next
Why are pyramids of biomass more accurate than the pyramid of number?
Pyramids of biomass are more accurate than pyramids of number because they provide a much better idea of thequantityof the plant or animal material at each level of a food chain and therefore are a better way of representing interdependence within the food chain
What does a pyramid of energy show?
- A pyramid of energy shows the total amount of energy that is transferred through each trophic level in an ecosystem over a certain period of time
- Not all of the energy grass plants receive goes into making new cellsthat can be eaten. Only the energy that is made into new cells remains with the organism to be passed on.
How much energy gets passed on from one trophic level to the next?
Only 10% of energy gets passed on from one trophic level to the next
Where is the majority of energy used up (90%) in organisms?
- making waste productsthat get removed from the organism
- as movement
- through respiration
- as heat(in mammals and birds that maintain a constant body temperature)
- as undigested waste(faeces) that is removed from the body and provides food for decomposers
Why do food chains usually have fewer than five trophic levels
Food chains usually have fewer than five trophic levels because of the significant energy loss that occurs at each trophic level, making it difficult to sustain a large number of higher-level consumers. There is less and less energy available to support organisms as you move up the food chain, at higher trophic levels (e.g., tertiary and quaternary consumers), there is often insufficient energy to support large populations or additional predators.
In order to survive, it would have to:
- eat a huge number of prey every day to get the amount of energy it needed to survive
- not expend much energy itself hunting them
Why is it more energy efficient for humans to eat crops?
- Given what we know aboutenergy transfer in food chains, it is clear that if humans eat the wheat there ismuch more energy availableto them than if they eat the cows that eat the wheat
- This is because90% of energy is lost each trophic level so the higher you go there is less available to pass on to humans. Therefore, it ismore energy efficient within a crop food chain for humans to be the herbivores rather than the carnivores
Explain the carbon cycle
- Carbonis taken out of the atmosphere in the form ofcarbon dioxideby plants to be used for photosynthesis
- It is passed on to animals (and microorganisms) byfeeding
- It is returned to the atmosphere in the form ofcarbon dioxideby plants and animals as a result ofrespiration
- When organisms die decomposers break down the organic molecules through the process of respiration to gain energy, releasing carbon dioxide back into the atmosphere
- If animals and plants die in conditions where decomposing microorganisms are not present the carbon in their bodies is trapped and can be converted, over millions of years and significant pressure, intofossil fuels
- When fossil fuels are burned in combustion, the carbon combines with oxygen andcarbon dioxide is releasedinto the atmosphere
- Increased use of fossil fuelsis contributing to an increase in the carbon dioxide content of the atmosphere.
- In addition,mass deforestationisreducing the number of producersavailable to take carbon dioxide out of the atmosphere by photosynthesis. This problem is exacerbated by the fact that in many areas of the world, deforestation is taking place for land rather than for the trees themselves, and as such they areburnt down, releasing yet more carbon dioxide into the atmosphere
🌟 Carbon is stored in the atmosphere as CO2, in plants as sugars, in animals as sugars, in dead organisms and in fossil fuels
Why is nitrogen needed and why can’t it be absorbed from the air?
Nitrogenis an element is required to make proteins. Neither plants nor animals canabsorb it from the airas N2gas is very stable and cannot be easily broken down
