Chapter 19 - Organisms and their environment Flashcards
What is the principle energy source in biological systems?
The sun is the principal source of energy input to biological systems. Energy flows through living organisms starting with light energy from the sun and then it is transferred to chemical energy in organisms. This energy is eventually transferred to the environment. E.g. as heat.
What is a food chain?
A food chain shows the transfer of energy from one organism to the next, beginning with a producer.
What is a food web?
A food web is a network of interconnected food chains.
What are producers?
Producers are organisms that produce their own organic nutrients usually from energy from sunlight. Plants are producers as they carry out photosynthesis to make glucose.
What is a herbivore?
Herbivore is an animal that gets its energy by eating plants.
What is a carnivore?
Carnivore is an animal that gets its energy by eating other animals.
What are primary consumers?
Primary consumers are herbivores as they feed on plants.
What are secondary consumers?
Secondary consumers are predators that feed on primary consumers.
What are tertiary consumers?
Tertiary consumers are predators that feed on secondary consumers.
What are decomposers?
Decomposers are bacteria and fungi that get their energy from feeding off dead and decaying organisms and undigested waste by secreting enzymes to break them down.
What is a trophic level?
A trophic level is the position of an organism in a food chain, food web or ecological pyramid.
What is a pyramid of numbers?
A pyramid of numbers show how may organisms are at each level of a food chain. They are not always pyramid shaped.
What is a pyramid of biomass?
A pyramid of biomass shows how much dry mass the creatures at each level. These are always pyramid shaped. This is because the mass of organisms has to decrease as you go up a food chain.
Why are pyramids of biomass more accurate than pyramids of numbers?
Pyramids of biomass provide a much better idea of the quantity of the plant or animal material at each level of as food chain and therefore are a better way of representing interdependence within the food chain.
What is a pyramid of energy?
A pyramid of energy shows the amount of energy ‘passed on’ by being consumed through a food chain.
What processes are involved in the carbon cycle?
Carbon is taken out of the atmosphere in the form of carbon dioxide by plants to be used for photosynthesis.
It is passed on to animals and microorganisms by feeding.
It is returned to the atmosphere in the form of carbon dioxide by plants, animals and microorganisms as a result of respiration.
If animals and plants die in conditions where decomposing microorganisms are present, their bodies can be decomposed.
If animals and plants die in conditions where decomposing microorganisms are not present, the carbon can be converted over millions of years and significant pressure into fossil fuels.
When fossil fuels are burned, combustion, carbon dioxide is released into the atmosphere.
What processes are involved in the nitrogen cycle?
Nitrogen gas in the air can be converted into a usable form using nitrogen fixing bacteria to convert N2 gas into ammonium compounds, which can then be converted into usable nitrates or by using lightning which can split the bond between the two N atoms, turning them into nitrous oxides like N2O and NO2 that dissolve in rainwater and leach into the soil.
Plants absorb nitrogen from the soil in the form of nitrates and use it to build proteins.
Animals eat the plant and get the nitrogen they need from the plant proteins. This nitrogen is passed up the food chain.
Waste (urine and faeces) from animals sends nitrogen back into the soil in the form of ammonium compounds. This process is called deamination.
The bodies of dead plants and animals’ decay and all the proteins inside them are broken down into ammonium compounds by decomposers.
The plants can’t absorb ammonium compounds so nitrifying bacteria convert the ammonium compounds to nitrites and then to nitrates which can be absorbed by plants.
Denitrifying bacteria takes nitrates out of the soil and converts them back to N2 gas. This process reduces soil fertility and is bad for plant growth. Denitrifying bacteria are anaerobic so aerating the soil can reduce the rate of denitrification.
During decomposition, microorganisms break down dead plants, animals and waste products, converting organic nitrogen into ammonia NH3 or ammonium ions NH4+ in a process called ammonification.
During nitrification, specific bacteria convert ammonia NH3 or ammonium ions NH4+ into nitrites NO2- and then into nitrates NO3-. This process allows plants to absorb nitrogen in a form they can use for growth.
During nitrogen fixation, certain bacteria convert atmospheric nitrogen N2 into ammonia NH3 which can then be used by plants. This process can occur in the soil or in the roots of certain plants.
Denitrification is the process where bacteria converts nitrates NO3- back into nitrogen gas N2 releasing it into the atmosphere and completing the nitrogen cycle. This process usually occurs in anaerobic conditions where oxygen is limited.
Diagram of a sigmoid population growth curve
