19. Organisms & Their Environment Flashcards
Producers definition
organisms that produce their own organic nutrients usually using energy from sunlight, Plants are producers as they carry out photosynthesis to make glucose
herbivore definition
an animal that gets its energy by eating plants
carnivore definition
an animal that gets its energy by eating other animals
primary consumers definition
herbivores - they feed on producers (plants)
secondary consumers definition
predators that feed on primary consumers
tertiary consumers definition
predators that feed on secondary consumers
decomposers definition
bacteria and fungi that get their energy from feeding off dead and decaying organisms and undigested waste (such as faces) by secreting enzymes to break them down
What does a food chain show?
A food chain shows the transfer of energy from one organism to the next, starting with a producer
What is the source of all energy in a food chain?
The source of all energy in a food chain is light energy from the Sun
What do the arrows in a food chain show?
The arrows in a food chain show the transfer of energy from one trophic level to the next
How is energy transferred from one organism to another?
Energy is transferred from one organism to another by ingestion (eating)
What is a food web?
A food web is a network of interconnected food chains
Why are food webs more accurate than food chains?
Food webs are more realistic ways of showing connections between organisms within an ecosystem as animals rarely exist on just one type of food source
What do food webs give us more information on?
Food webs give us a lot more information about the transfer of energy in an ecosystem
What type of relationship does a food web show?
interdependence
interdependent definition
how the change in one population can affect others within the food web
What causes most of the changes in populations?
Most of the changes in populations of animals and plants happen as a result of human impact – either by overharvesting of food species or by the introduction of foreign species to a habitat
Why is human impact on environments so harmful?
Due to interdependence, these can have long-lasting knock-on effects to organisms throughout a food chain or web
What is a trophic level?
Trophic levels describe the position of an organism in a food chain, web or pyramid
Does an animal have to be at only one trophic level? Why?
NO
Animals (known as consumers) can be at different trophic levels within the same food web as they may eat both primary, secondary and / or tertiary consumers
How does energy from the sun flow to the first trophic level?
Energy flows from the sun to the first trophic level (producers) in the form of light
How do producers make use of light energy?
Producers convert light energy into chemical energy and it flows in this form from one consumer to the next
Where is all energy eventually transferred to?
Eventually all energy is transferred to the environment – energy is passed on from one level to the next with some being used and lost at each stage
Is energy flow a cyclical or non-cyclical process?
NON-CYCLICAL
Energy flow is a non-cyclical process – once the energy gets to the top of the food chain or web, it is not recycled but ‘lost’ to the environment
What is energy flow a direct contrast to?
This is in direct contrast to the chemical elements that organisms are made out of, which are repeatedly recycled
(as energy is not recycled)
What has to happen to energy for it to be transferred ?
In order for the energy to be passed on, it has to be consumed (eaten)
Why is not all of the energy from e.g plants passed onto the primary consumer?
However not all of the energy grass plants receive goes into making new cells that can be eaten
Only the energy that is made into new cells remains with the organism to be passed on
Why may an organism not receive all of the energy in a plant?
Even then, some of this energy does not get consumed – for example few organisms eat an entire organism, including roots of plants or bones of animals – but energy is still stored in these parts and so it does not get passed on
In what 4 ways can energy in a an organism be “lost”?
making waste products eg (urine) that get removed from the organism
as movement
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 are food chains rarely longer than 5 organisms long?
This inefficient loss of energy at each trophic level explains why food chains are rarely more than 5 organisms long
If, for example, an organism would prey on the top consumer, why would this not be efficient?
In order to survive, it would have to:
eat a huge number of them every day to get the amount of energy it needed to survive (are there that many barn owls close together?)
not expend much energy itself hunting them (is this likely?)
How much energy is:
available to the organism at the next level
lost as heat and in undigested materials?
10% of energy available to organisms at the next level to make new biomass
90% of energy lost as heat an in undigested materials
What type of consumer are humans? What does this mean?
Humans are omnivores, obtaining energy from both plants and animals, and this gives us a choice of what we eat
What does humans being omnivores impact?
These choices, however, have an impact on what we grow and how we use ecosystems
Looking at this food chain, why would it be better for humans to eat the wheat, rather than the cow?
wheat → cow → human
wheat → human
Given what we know about energy transfer in food chains, it is clear that if humans eat the wheat there is much more energy available to them than if they eat the cows that eat the wheat
This is because energy is lost from the cows, so there is less available to pass on to humans
Therefore, it is more energy efficient within a crop food chain for humans to be the herbivores rather than the carnivores
What do humans feed animals and why?
In reality, we often feed animals on plants that we cannot eat (eg grass) or that are too widely distributed for us to collect (eg algae in the ocean which form the food of fish we eat)
What does a pyramid of number show?
A pyramid of numbers shows how many organisms we are talking about at each level of a food chain.
What does the width of a box in a pyramid of number suggest?
The width of the box indicates the number of organisms at that trophic level
Does a pyramid of numbers always have to be pyramid shaped? Why?
NO
This is because the size of the organism is also important – one large organism, like the oak tree in the pyramid above, contains enough energy to support many smaller organisms (the insects)
What are two important things to remember when drawing a pyramid of numbers?
You cannot change the trophic level of the organisms – they must stay in the same order as in the food chain with producers on the bottom, followed by primary consumers, then secondary consumers, then tertiary consumers
Generally, the larger an individual organism is, the less of them there are
What does a pyramid of biomass show?
A pyramid of biomass shows how much mass the creatures at each level would have without including all the water that is in the organisms (their ‘dry mass’)
Do pyramids of biomass have to be pyramid-shaped? Why?
YES
This is because the mass of organisms has to decrease as you go up a food chain – if we take our first food chain as an example, it’s impossible to have 10kg of grass feeding 50kg of voles feeding 100kg of barn owls
Why are pyramids of biomass better than pyramids of number?
Pyramids of biomass provide a much better idea of the quantity of 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
Why are there nutrient cycles?
Nutrients such as carbon and nitrogen are not endless resources
There is a finite amount of each element on the planet and as such, they need to be RECYCLED in order to allow new organisms to be made and grow
- In what form is carbon take out of the atmosphere in and what is it used for?
Carbon is taken out of the atmosphere in the form of carbon dioxide by plants to be used for photosynthesis
- Where does the carbon dioxide the plants have absorbed go?
It is passed on to animals (and microorganisms) by feeding
- How is this carbon returned to the atmosphere?
It is returned to the atmosphere in the form of carbon dioxide by plants, animals and microorganisms as a result of respiration
- What is a natural source of carbon in the Earth and how is this formed?
If animals and plants die in conditions where decomposing microorganisms are not present the carbon in their bodies can be converted, over millions of years and significant pressure, into fossil fuels
- How is the carbon in fossil fuels released?
When fossil fuels are burned (the process is known as combustion), the carbon combines with oxygen and carbon dioxide is released into the atmosphere
What is an increased use of fossil fuels causing?
Increased use of fossil fuels is contributing to an increase in the carbon dioxide content of the atmosphere
What is mass deforestation causing, in relation to the carbon cycle?
In addition, mass deforestation is reducing the amount of producers available to take carbon dioxide out of the atmosphere by photosynthesis
What is mass deforestation specifically for land causing, in relation to the carbon cycle?
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 are burnt down, releasing yet more carbon dioxide into the atmosphere
What are the 4 basic steps of the carbon cycle?
Carbon is taken out of the atmosphere by photosynthesis
It is passed on to animals and decomposers by feeding
It is returned by respiration; in plants, in animals and in decomposing
microorganisms
In addition, it is returned (in increasing amounts) by combustion of fossil fuels
- Where do water molecules move between?
Water molecules move between various locations – such as rivers, oceans and the atmosphere – by specific processes
- How is water able to move between certain locations?
This is possible because water changes state at a relatively low temperature
- In what form does water enter the atmosphere?
Water enters the atmosphere as water vapour
- In what two processes can water vapour enter the atmosphere?
evaporation
- transpiration
- How does evaporation work?
Energy from the Sun heats the Earth’s surface and water evaporates from oceans, rivers and lakes
- How does transpiration work?
Transpiration from plants releases water vapour into the air
- What does the warmer air of the lower atmosphere do?
The warmer air of the lower atmosphere rises, taking the water vapour with it
- What happens to the warm air as it rises and what does this form?
The moist air cools down as it rises
Water vapour condenses back into liquid water, forming clouds
- How does water return to the earth?
Water returns to Earth in the form of precipitation
- How does precipitation occur?
As the water droplets in the cloud get bigger and heavier, they begin to fall as rain, snow and sleet
This is called precipitation
- What is nitrogen used for?
Nitrogen as an element is required to make proteins
- Why is N2 gas not very useful?
Neither plants nor animals can absorb it from the air
- Why can N2 gas not be absorbed from the air?
N2 gas is very stable and the bonds holding the nitrogen atoms together would need massive amounts of energy to break (the two nitrogen atoms in a nitrogen molecule are held together by a triple covalent bond)
- In what two ways can N2 be taken out of the air and converted into something which can be used?
nitrogen fixing bacteria
- lightning can ‘fix’ it
- How can nitrogen fixing bacteria convert N2 to a useable form?
take N2 gas and change it into nitrates in the soil
- How can lightning convert N2 to a useable form?
splitting the bond between the two atoms and turning them into nitrous oxides like N2O and NO2 that dissolve in rainwater and ‘leach’ into the soil
- Where can nitrogen fixing bacteria be found?
found ‘free living’ in soil and also in the root nodules of certain plants (peas, beans, clover – we call them leguminous plants)
- In what form do plants absorb N?
Plants absorb the nitrates they find in the soil and use the nitrogen in them to make proteins
- How do animals absorb N?
Animals eat the plants (or other animals) and get the nitrogen they need from the proteins in the plant or animal
- How is N returned back to the soil from animals?
Waste (urine and faeces) from animals sends nitrogen back into the soil as ammonium compounds (the urea in urine contains nitrogen)
- What happens to the N present in animals and plants when they die?
When the animals and plants die, they decay and all the proteins inside them are broken down into ammonium compounds and put back into the soil by decomposers
- Why are ammonium compounds not useful and how is this problem fixed?
The plants can’t absorb ammonium compounds though, so a second type of soil bacteria, nitrifying bacteria, are used to convert the ammonium compounds
- What do nitrifying bacteria do? how is the useful?
nitrifying bacteria, convert the ammonium compounds to nitrites and then to nitrates, which can then be absorbed by plants – and so the cycle goes on
- What third type of bacteria also uses N?
type of (anaerobic) bacteria called denitrifying bacteria
- Where are denitrifying bacteria found?
found in poorly aerated soil (ie not much oxygen)
- What do denitrifying do?
These bacteria take the nitrates out of the soil and convert them back into N2 gas
- How can farmers help decrease the number of denitrifying bacteria?
Farmers can help reduce the amount of these unhelpful bacteria by ploughing and turning over soil
Population definition
A population is defined as a group of organisms of one species, living in the same area at the same time
Community definition
A community is defined as all of the populations of different species in an ecosystem
Ecosystem definition?
An ecosystem is defined as a unit containing the community of organisms and their environment, interacting together (eg a decomposing log, a lake)
What do living organisms compete with each other for?
All living organisms compete with each other for food, water and living space
What type of organisms increase their populations the fastest?
Those which are the best adapted to their environments generally increase their populations at the expense of those less well adapted
What 3 factors affect population growth?
Food supply
Predation
Disease
In what way has human population been growing for the last 150 years?
Human population growth globally has been increasing exponentially for the last 150 years
What are reasons for the exponential growth of the human population?
Improved technology leading to an abundance of food = rapid increase in birth rate
Improved medicine, hygiene and health care = decrease in death rate
What is the name of a population growth graph which looks like an s?
The shape of this curve ( a little like an ‘S’), gives it its name – a sigmoid growth curve
What 4 phases does a sigmoid graph have?
lag phase
log
phase
stationary phase
death phase
What is the lag phase on a s graph?
organisms are adapting to the environment before they are able to reproduce; in addition, at this stage there are very few organisms and so reproduction is not producing larger numbers of offspring
What is the log phase on a s graph?
(aka exponential phase) – food supply is abundant, birth rate is rapid and death rate is low; growth is exponential and only limited by the number of new individuals that can be produced
What is the stationary phase on a s graph?
population levels out due to a factor in the environment, such as a nutrient, becoming limited as it is not being replenished; birth rate and death rate are equal and will remain so until either the nutrient is replenished or becomes severely limited
What is the death phase on a s graph?
population decreases as death rate is now greater than birth rate; this is usually because food supply is short or metabolic wastes produced by the population have built up to toxic levels
Are organisms in natural environment likely to show a population growth like a sigmoid growth curve? Why?
NO
- because they’re affected by many other factors
What factors affect can organisms in a natural environment? 5
changing temperature or light
predators
disease
immigration (individuals moving into the area)
emigration (individuals moving out of the area)
Define food chain
The transfer of energy from one organism to the next, beginning with a producer
Define trophic level
The position of an organism in a food chain, food web, pyramid of numbers or pyramid of biomass
Why is the transfer of energy from one trophic level to the next inefficient?
Because of egestion, excretion, respiration and production of inedible bones and shells
Define food web
A network of interconnected food chains
Define Producer
An organism that makes its organic nutrients usually from energy from sunlight through photosynthesis
Define Consumer
An organism that gets its energy by feeding on other organisms
Define Herbivores
An animal that gets its energy by eating plants
Define Carnivores
An animal that gets its energy by eating other animals
Define Decomposer
An organism that gets its energy from dead or waste organic material
Why is the pyramid of biomass better than the pyramid of numbers?
Pyramids of biomass take into account the size of organisms
Less misinterpreted
Range of numbers may be enormous
What is the importance of the water cycle?
Living organisms require water- provides organisms with a constant supply of water
How is nitrogen fixed?
By lightning and bacteria -root nodules of certain plants (peas, beans, clover – leguminous plants) take N2 gas and change it into nitrates in the soil
What produces ammonium ions?
Decomposers break dead matter down into ammonium ions
What converts ammonia into nitrites and nitrates
Nitrifying bacteria
What absorbs nitrate ions?
Plants
What release nitrogen back into the atmosphere?
Denitrifying bacteria
What is deamination?
Removal of the amine group in an amino acid
What is nitrogen fixation?
is when N2 and H2 combine to form ammonium ions then nitrate if oxygen is present
What are legumes used for?
To avoid using so much nitrogen- containing fertiliser so therefore it is less expensive
