4 Ecosystems Flashcards
What is an ecosystem?
Community of living organisms together with their non-living environment.
What components do all ecosystems have?
- Producers.
- Consumers.
- Decomposers.
- The physical environment.
What are producers?
Organism that makes its own food, e.g green plants.
What are consumers?
Organism that eats other organisms.
What are decomposers?
Organism that feeds by breaking down the dead remains of other organisms, helping to recycle nutrients.
What is the physical environment?
All the non-biological components of the ecosystem; for example, the water and soil in a pond or the soil and air in a forest.
What are the living components of an ecosystem called?
The biotic components.
What are the non-living (physical) components of an ecosystem called?
The abiotic components.
What are biotic factors?
Biological factor affecting an ecosystem.
What are examples of biotic factors?
- Food supply.
- Predation.
What are abiotic factors?
Physical or chemical factor affecting an ecosystem.
What are examples of abiotic factors?
- Light intensity.
- Temperature.
What does an ecosystem contain a variety of?
An ecosystem contains a variety of habitats.
What is a habitat?
The place where an organism lives.
What are examples of habits in a pond ecosystem?
They include:
- The open water.
- The mud at the bottom of the pond.
- The surface water
What is the population?
All the organisms of one species living in a particular habitat at a certain time.
What are examples of the possible populations in a pond?
- All the immature frogs (tadpoles)
swimming in a pond are a population of tadpoles - All the water lily plants
growing in the pond make up a population of water lilies.
What is a community?
All organisms of all species found in a particular area at a certain time.
What is an image which shows a pond ecosystem?
What must an ecologist do when he wants to know how many organisms there are in a particular habitat?
He should count a smaller representative part of the population, called a sample.
How can we sample plants or animals that do not move much - like snails?
By using a quadrat.
What is a quadrat?
It is a square used in ecological investigations to sample animals or plants.
How do you figure out what the size of the quadrat should be?
The size of quadrat you use depends on the size of the organisms being sampled.
What is the best size of quadrat to use to count plants growing on a school field?
To count plants growing on a school field, you could use a quadrat with sides 0.5 or 1 metre in length.
What is an example of a student sampling with a quadrat?
What is an important thing to do when using a quadrat?
It is important that sampling in an area is carried out at random.
Why is it important that sampling in an area is carried out at random?
To avoid bias.
What is an example of collecting a biased sample when sampling from a school field?
If you were sampling from a school field, but for convenience only placed your quadrats next to a path, this probably wouldn’t give you a sample that was representative of the whole field.
What is a practical that we can do involving quadrats?
Using quadrats to compare the size of plant population in two areas of a field.
When using quadrats to compare the size of plant population in two areas of a field, how can we sample randomly?
One way that you can sample randomly is to place quadrats at
coordinates on a numbered grid
What is the first step when using quadrats to compare the size of plant population in two areas of a field?
A pair of random numbers is generated, using the random number
function on a calculator.
How are these numbers used?
These numbers are used as coordinates to position the quadrat in the large square
What is the second step when using quadrats to compare the size of plant population in two areas of a field?
The number of dandelions in the quadrat are counted.
What is the third step when using quadrats to compare the size of plant population in two areas of a field?
The process is then repeated for nine more quadrats.
What is the fourth step when using quadrats to compare the size of plant population in two areas of a field?
The tape measures are then moved to area B and the process repeated
to sample from ten more quadrats in that part of the field.
What is an example of a table that we might get from this study?
What are organisms in an ecosystem constantly doing?
The organisms in an ecosystem are continually interacting with each other and with their physical environment.
What are examples of the interactions that these organisms are having?
- Feeding among the organisms.
- Competition among the organisms.
- Interactions between organisms and the environment.
What are we referring to when we say feeding among the organisms?
The plants, animals and decomposers are continually recycling the same nutrients through the ecosystem.
What are we referring to when we say competition among the organisms?
Animals compete for food, shelter, mates, nesting sites; plants compete for carbon dioxide, mineral ions, light and water.
What are we referring to when we say interactions between organisms and the environment?
Plants absorb mineral ions, carbon dioxide and water from the environment; plants also give off water vapour and oxygen into the environment; animals use materials from the environment to build shelters; the temperature of the environment can affect processes occurring in the organisms; processes occurring in organisms can affect the temperature of the environment (all organisms produce some heat).
What are the factors that influence the numbers and distribution of organisms in an ecosystem?
Biotic and abiotic factors.
What kind of factors are biotic factors?
Biological factors.
What are examples of biotic factors?
- Availability of food and competition for food resources.
- Predation.
- Parasitism.
- Disease.
- Presence of pollinating insects.
- Availability of nest sites.
What kind of factors are abiotic factors?
Chemical factors.
What are examples of abiotic factors?
- Climate, such as light intensity, temperature and water availability.
- Hours of daylight.
- Soil conditions, such as clay content, nitrate level, particle size, water content and pH.
- Other factors specific to a particular habitat, such as salinity (salt content) in an estuary, flow rate in a river, or oxygen concentration in a lake.
What do which factors that affect population sizes and distribution of organisms depend on?
The type of ecosystem.
What are some of the main abiotic factors of a river?
- Depth of water.
- Flow rate.
- Type of material at the bottom of the stream (stones, sand, mud, etc).
- Concentration of minerals in the water.
- pH.
- Oxygen concentration.
- Cloudiness of the water.
- Presence of any pollution.
Is it only either abiotic or either biotic factors that will affect this river?
The main biotic factors affecting animals in the river will be food supply, either from plants or other animals. But other factors are important too - large fish could not live in a shallow stream.
Then, how can we figure out which are the most important factors in an environment?
It is impossible to generalise about which factors are the most important.
What is an example of this, and how do the factors differ from one environment to the other?
In a heavily polluted river all the organisms could be killed by the pollution, while in a clean river depth and flow rate might have a greater effect on the animals that could live there.
What is another thing that the factors may do?
The different factors may also affect one another.
What is an example of the different factors that affect one another?
For example, a faster flow rate could mix the water with air, increasing the amount of dissolved oxygen.
What is the main factor affecting large ecosystems?
Climate, particularly temperature and rainfall.
What is an example of how climate affects large ecosystems?
Climate is the reason why tropical rainforests are restricted to a strip near the equator of the Earth, while pine forests grow in the higher latitudes of the northern hemisphere.
How can feeding relationships be represented?
The simplest way of showing feeding relationships within an ecosystem is a
food chain.
What is a food chain?
It is a flow diagram showing the feeding
relationships in an ecosystem.
What does an arrow in a food chain represent?
- It means ‘is eaten by’.
- It shows the direction of energy flow.
What is a trophic level?
Different feeding levels in a food chain.
What are the different names of the trophic levels in a food chain?
- Producer.
- Primary consumer.
- Secondary consumer.
- Tertiary consumer.
- Quaternary consumer.
What is a producer?
Organism that makes its own food, e.g green plants.
What is a primary consumer?
Organism that feeds on producers.
What is a secondary consumer?
Organism that feeds on a primary consumer.
What is a tertiary consumer?
Organism that feeds on secondary consumers.
What is a quaternary consumer?
Organism that feeds on tertiary consumers.
What is another name for a quaternary consumer?
The top carnivore.
Why are food chains good?
Food chains are a convenient way of showing the feeding relationships
between a few organisms in an ecosystem.
Why are food chains bad?
They oversimplify the situation.
What is an example of a marine food chain?
plankton → crustacean → fish → ringed seal → polar bear.
How can we use this food chain to explain how they are oversimplified?
The marine food chain above implies that only crustaceans feed on plankton,
which is not true. Some whales and other mammals also feed on plankton.
How can we gain a fuller unserstanding?
You need to consider how the different food chains in an ecosystem relate to each other.
What is a food web?
A diagram showing the way in which several food chains are linked together in an ecosystem.
What is an image of the food web of a salmon?
What is good about this food web?
It gives a clearer picture of the
feeding relationships involved in a freshwater ecosystem in which salmon are the top carnivores.
What is a disadvantage of food webs?
This is still an oversimplification of the true situation, as some feeding
relationships are still not shown.
Why is a food web still better than a food chain though?
It does, however, give some indication of the interrelationships that exist between food chains in an ecosystem.
How can we use a food web?
With a little thought, you can predict how changes in the numbers of an organism in one food chain in the food web might affect those in another food chain.
What is an example of how we can see a cause-and-effect relationship in the food web we described above?
We can look at what would happen if there was a decline in the leech population.
What might be some consequences of the leech population declining?
- The stonefly nymph population could increase as there would be more
midge larvae to feed on. - The stonefly nymph population could decrease as the mature salmon might
eat more of them as there would be fewer leeches. - The numbers could remain the same due to a combination of the above.
What is a major disadvantage of both food chains and food webs?
Although food webs give us more information than food chains, they don’t give any information about how many, or what mass of organisms is involved. Neither do they show the role of the decomposers.
How can we find out this information then?
To see this, we must look
at other ways of presenting information about feeding relationships in an
ecosystem.
What is an alternate way of presenting information like in food webs, but with mass and numbers?
Ecological pyramids.
What are ecological pyramids?
Ecological pyramids are diagrams that represent the relative amounts of
organisms at each trophic level in a food chain.
What are the two main types of ecological pyramids?
- Pyramids of numbers.
- Pyramids of biomass.
What are pyramids of numbers?
A diagram in which blocks making
up a pyramid represent the total numbers of organisms at
each trophic level.
What are pyramids of biomass?
A diagram in which blocks making
up a pyramid represent the total mass of organisms at each trophic level.
What is biomass?
Total mass of organisms, e.g. in an ecosystem.
What are examples of two food chains?
grass → grasshopper → frog → bird
oak tree → aphid → ladybird → bird
What is a diagram which shows the pyramids of numbers for the two food chains?
What is a diagram which shows the pyramids of biomass for the two food chains?
What is an explanation of the two pyramids for the ‘grass’ food chain?
The two pyramids for the ‘grass’ food chain look the same – the numbers at each trophic level decrease. The total biomass also decreases along the food chain – the mass of all the grass plants in a large field would be more than that of all the grasshoppers which would be more than that of all the frogs, and so on.
What is an explanation of the two pyramids for the ‘oak tree’ food chain?
The two pyramids for the ‘oak tree’ food chain look different because of the size of the oak trees. Each oak tree can support many thousands of aphids, so the numbers increase from first to second trophic levels. But each ladybird will need to eat many aphids and each bird will need to eat many ladybirds, so the numbers decrease at the third and fourth trophic levels. However, the total biomass decreases at each trophic level – the biomass of one oak tree is much greater than that of the thousands of aphids it supports. The total biomass of
all these aphids is greater than that of the ladybirds, which is greater than that of the birds.
What would the ‘oak tree’ food chain look like if the birds were parasitised by a nematode worm?
oak tree → aphid → ladybird → bird → nematode worm.
What would the pyramid of numbers look like now with the parasitised birds?
What is an explanation of this pyramid of numbers?
The pyramid of numbers now takes on a very strange appearance because of the large numbers of parasites on each bird.
What would the pyramid of biomass look like now with the parasitised birds?
What is an explanation of this pyramid of biomass?
The pyramid of biomass, however, has a true pyramid shape because the total
biomass of the nematode worms must be less than that of the birds they parasitise.
Why are diagrams of feeding relationships a pyramid shape, with reference to an example of a rabbit?
The explanation is relatively straightforward. When a rabbit eats
grass, not all of the materials in the grass plant end up as rabbit! There are
losses.
What are examples of some of these losses in terms of a rabbit?
- Some parts of grass are not eaten (the roots for example).
- Some part are not digested and so are not absorbed - even though rabbits have a very efficient digestive system.
- Some of the materials absorbed form excretory products.
- Many of the materials are respired to release energy, with the loss of carbon dioxide and water.
What is a diagram which shows that not all the grass eaten by a rabbit ends up as rabbit tissue?
How much of the grass ends up in new rabbit cells?
In fact, only a small fraction of the materials in the grass ends up in new cells in the rabbit.
What happens to these losses at each stage in the food chain?
Similar losses are repeated at each stage in the food chain, so
smaller and smaller amounts of biomass are available for growth at successive trophic levels. The shape of pyramids of biomass reflects this.
What is feeding in reference to energy?
Feeding is a way of transferring energy between organisms.
What is another way of modelling ecosystems?
Another way of modelling ecosystems looks at the energy flow between the various trophic levels.
What is something different about the way of showing the flow of energy through ecosystems?
This approach focuses less on individual organisms and food chains and rather more on energy transfer between trophic levels (producers, consumers and decomposers) in the whole ecosystem.
What are the key ideas when using the method of the flow of energy through ecosystems?
- Photosynthesis ‘fixes’ sunlight energy into chemicals such as glucose and
starch. - Respiration releases energy from organic compounds such as glucose.
- Almost all other biological processes (e.g. muscle contraction, growth,
reproduction, excretion, active transport) use the energy released in
respiration. - If the energy released in respiration is used to produce new cells, then the
energy remains ‘fixed’ in molecules in that organism. It can be passed on to
the next trophic level through feeding. - If the energy released in respiration is used for other processes then it
will, once used, eventually escape as heat from the organism. Energy is
therefore lost from food chains and webs at each trophic level.
What is an image of an energy flow diagram?
What does this energy flow diagram show?
It shows the main ways in which
energy is transferred in an ecosystem. It also gives the amounts of energy
transferred between the trophic levels of this particular (grassland) ecosystem.
What amount of energy is transferred from one trophic level to the other?
As you can see, only about 10% of the energy entering a trophic level is
passed on to the next trophic level.
What does this rate of 10% being transferred on tell us about food chains?
This explains why not many food chains
have more than five trophic levels.
What is an example of a food chain?
A → B → C → D → E
What things can we deduce when coming thinking about 10% of energy only being passed along, in terms of the length of the chain?
If we use the idea that only about 10% of the energy entering a trophic level is
passed on to the next level, then, of the original 100% reaching A (a producer),
10% passes to B, 1% (10% of 10%) passes to C, 0.1% passes to D and only
0.001% passes to E. There just isn’t enough energy left for another trophic
level.
Why are there six trophic levels in some parts of the world?
In certain parts of the world, some marine food chains have six trophic
levels because of the huge amount of light energy reaching the surface waters
Are the chemicals in our body new?
The chemicals that make up our bodies have all been around before –
probably many times.
What is this cycle of the constant recycling of substances referred to as?
This constant recycling of substances is all part of the cycle of life, death and decay.
What plays a key role in recycling?
Microorganisms.
What do the microorganisms do in recycling?
They break down complex organic
molecules in the bodies of dead animals and plants into simpler substances, which they release into the environment.
What is another cycle that we need to be familiar with?
The carbon cycle.
What is carbon?
Carbon is a component of all major biological molecules.
What are some named molecules that contain carbon?
Carbohydrates, lipids, proteins, DNA, vitamins and many other molecules all contain carbon.
What are the processes that are important in cycling carbon through ecosystems?
- Photosynthesis ‘fixes’ carbon atoms from carbon dioxide into organic
compounds. - Feeding and assimilation pass carbon atoms already in organic compounds
along food chains. - Respiration produces inorganic carbon dioxide from organic compounds.
(mainly carbohydrates) as they are broken down to release energy - Fossilisation – sometimes living things do not decay fully when they die due
to the conditions in the soil (decay is prevented if it is too acidic) and fossil
fuels (coal, oil, natural gas and peat) are formed. - Combustion releases carbon dioxide into the atmosphere when fossil fuels
are burned.
What is an image that shows the main stages of the carbon cycle?
What is an image that shows a typical illustration of the carbon cycle?
