organisation of an ecosystem Flashcards
bbc bitesize
boimass
definition
The dry mass of an organism.
decompose
definition
If a substance decomposes, it breaks down into simpler compounds or elements.
decomposer
definition
An organism which eats dead organisms, fallen leaves, animal droppings, etc, and breaks them down into simpler materials.
ecosystem
definition
The living organisms in a particular area, together with the non-living components of the environment.
endangered species
definition
Animals that are close to extinction because of their low numbers.
faeces
definition
Waste matter from the bowels.
food web
definition
A network of food chains, showing how they all link together.
primary consumer
definition
The name given to an organism that eats a producer. A herbivore.
producer
definition
Plants that begin food chains by making energy from carbon dioxide and water.
quadrat
definition
A square frame of known area used for sampling the abundance and distribution of slow or non-moving organisms.
secondary consumer
definition
An organism that obtains its energy by eating the primary consumer.
sampling
definition
The selection of subjects included in a study.
species
definition
A type of organism that is the basic unit of classification. Individuals of different species are not able to interbreed successfully.
transect
definition
A line created, for instance, with a tape measure, along which sampling occurs.
trophic level
definition
The position of an organism in a food chain, food web or pyramid.
zonation
definition
Growing of plants in distinction regions.
Ecosystem
An ecosystem is the interaction between a community of living organisms and their environment. A community is two or more populations of organisms. An ecosystem is the interaction of two or more populations of organisms in their environment.
Producers and consumers
feeding relationships
Feeding relationships show what organisms eat or are eaten by others and through this the levels of organisation in an ecosystem. These can be shown in food chains, which add together to make food webs for a habitat.
Producers
At the base of almost every food chain is a producer. These are plants or algae, which photosynthesise. This means they convert energy from the sun into glucose during photosynthesis produces biomass. It is this which feeds the rest of the food chain.
Levels of organisation
All animals above the producer are called consumers. The first is the primary consumer, the next is the secondary consumer. Animals that hunt and kill others are called predators, and those that are hunted and killed are called prey. The top animal in the feeding relationship is called the apex predator.
Decomposers
Decomposers are bacteria and fungi, which break down dead organisms in a process called decomposition or rotting. They do this by releasing enzymes onto the dead matter and afterwards, consume the broken down substances. They form a vital role in the recycling of matter. When organisms die and decompose plants absorb the broken down nutrients through their roots.
Sampling
why?
It is important to estimate the number of organisms in a population to better understand the relationships in a community. This information is useful for monitoring the impact of conservation projects that aim to conserve endangered species or habitats. It is almost always impossible to count all of the organisms in a population. So we look at a small section of a population to draw conclusions about the rest. This process is called sampling and the area or part of population looked at is called a sample.
What is sampling?
When sampling a population, the numbers of organisms are counted within a sample site, and then the results multiplied to estimate the total number in the entire habitat. Large animals and plants can often simply be counted. However, many smaller animals like insects and smaller mammals need to be trapped first so they can be counted and then released afterwards.
Sampling
pitfalls
Many smaller animals like insects and smaller mammals need to be trapped first so they can be counted and then released afterwards.
Pitfall traps are small traps dug into the ground, which often has food inside to attract small mammals. The sides of these traps are smooth to stop the mammals escaping.
Sampling
kick-sampling
Many smaller animals like insects and smaller mammals need to be trapped first so they can be counted and then released afterwards.
A method is to use large nets to sweep through grasses or leaves of trees in a process called sweep netting. To catch aquatic organism nets are often held downstream of an area of river bed which is then gently disturbed by the person doing the sampling. The small animals float into the net. This is called kick-sampling.
Sampling
pooter
Many smaller animals like insects and smaller mammals need to be trapped first so they can be counted and then released afterwards.
Pooters are small devices used when sampling to suck up small insects safely without them going into your mouth.
What are quadrats?
How are they used?
Quadrats are square frames of wire usually 0.25 m2. These are placed on the ground to look at the plants or slow-moving animals within them.
When looking at plants in a quadrat the following sampling can be used:
- Number of individual species
- Species richness
- Percentage cover
Using quadrats
When looking at plants in a quadrat the following sampling can be used:
Number of individual species
Number of an individual species: the total number of individuals of one species (eg daisies) is recorded.
Using quadrats
When looking at plants in a quadrat the following sampling can be used:
Species richness
Species richness: the number of different plant or animal species is recorded but not the number of individuals within a species.
Using quadrats
When looking at plants in a quadrat the following sampling can be used:
Percentage cover
Percentage cover: the percentage of the quadrat area that is covered by one species (eg grass). This is easier to estimate if a quadrat has wires making smaller sections. Percentage cover rather than number of individuals is used when estimating plant frequencies if it is difficult to identify individual plants, such as grasses or moss.
Random sampling
Random sampling using a quadrat involves the placing of quadrats at random coordinates. Regardless of whether you are investigating the number of individual species, the species diversity or the percentage cover in different areas you would use random sampling.
systematic sampling
Most sampling is random, but systematic sampling can be used if there is a trend or pattern across the habitat, such as distance up a beach, or altitude on a hillside. If you are using the wrong kind of sampling method for your experiment, this can lead to biased results.
What are we sampling for?
Sometimes we want to see if the number of species or percentage cover changes within an area. This is often as a result of a change in an abiotic factor.
An example of this is an investigation into whether the growth of seaweed depends upon the distance it is found on the seashore from the tide. As we are looking to link a linear change (in this case the number of hours the seaweed is covered by the tide) we would use systematic sampling.
A quadrat could be placed at regular distances, for example every five metres, along an imaginary line called a transect, which would run down the shore. Systematic sampling would be used along the transect to link changes in species to abiotic factors, such as immersion by water, temperature fluctuations, light intensity, all of which are influenced by the tide.
The results from transects can be drawn into kite diagrams. The width of the bar from the middle at any distance shows how many individuals were observed at that point.
Zonation
A change in the distribution of species across a habitat is called zonation. It can happen because of a change in an abiotic factor.
Mean
The mean is the most common type of average we use. To calculate the mean you add all the values together and divide by the total number of values.
Median
To calculate the median, a set of numbers are placed in increasing order of size. The median is the middle number in the list. The two students took an even number of readings, and they calculated the median as the mean of the two middle numbers.
Mode
The mode is the value that appears the most often. In the shade, the mode is four because there are three values of four. In the sun, it is five because there are three values of five.
The second trophic level in all food chains is a what?
The second trophic level in all food chains is an herbivore or omnivore called a primary consumer.
The third trophic level is a what?
The third stage is a carnivore or omnivore which eats the primary consumer. This is called the secondary consumer
The final trophic level is what?
The final level is perch, which is a carnivore and is often called the top or apex predator. Organisms at the tops of food chains have no predators.
What are producers?
Green plants - they make glucose during photosynthesis.
What are primary consumers?
Usually eat plant material - they are herbivores. For example rabbits, caterpillars, cows and sheep.
What are secondary consumers?
Eat animal material - they are omnivores or carnivores. For example cats, dogs and lions.
What are predators?
Kill for food. They are either secondary or tertiary consumers.
What are prey?
The animals that predators feed on.
What are decomposers?
Feed on dead and decaying organisms, and on the undigested parts of plant and animal matter in faeces.
Biomass
Biomass is living or recently dead tissues. The mass of your body is biomass because you are alive. Wood is considered biomass because it was recently a plant. Fossil fuels are not considered biomass because they are the remains of organisms that died millions of years ago and have been chemically changed from the original living tissue.
Pyramids of biomass
The amount of biomass can be measured at different trophic levels in a food chain. The total biomass of each trophic level is often represented as a modified bar chart called a pyramid of biomass. In a food chain from a healthy ecosystem the biomass at each trophic level must reduce.
Pyramids of biomass are always perfectly shaped. If this is not the case, then the ecosystem is likely to be unhealthy and in danger.
Pyramids of biomass must be drawn with the:
- bars equally spaced around the midpoint
- bars touching
- bar for the producer at the bottom
- length of each bar is proportional to the amount of biomass available at each trophic level
Calculating efficiency of biomass transfers
The efficiency of biomass transfer is a measure of the proportion of biomass transferred from a lower trophic level to a higher one. Usually around 10% of biomass is transferred between trophic levels in a healthy ecosystem and the remaining 90% is used by the organisms during life processes.
Q. This is an example of a food chain:
phytoplankton → zooplankton → herring → sea lion
The total biomass within the phytoplankton is 14.6 kg. The total biomass within the zooplankton is 1.3 kg. What is the efficiency of this transfer?
To complete this calculation, divide the amount from the higher trophic level by the amount from the lower trophic level and multiply by one hundred. That is, divide the smaller number by the bigger one (and multiply by one hundred).
percentage efficiency transfer = (biomass in higher trophic level / /biomas in lower trophic level) x 100
percentage efficiency transfer = (1.3kg/14.6) x 100 = 8.9%
Percentage efficiency transfer equation
percentage efficiency transfer = (biomass in higher trophic level / /biomas in lower trophic level) x 100
What is used for estimating the number of plants?
Quadrat
What is the name of the sampling square used in fieldwork?
Quadrat
A 0.25 m^2 quadrat was placed in a 100 m^2 field. Five daisy plants were counted in the quadrat. What is the estimated number of daisies in the field?
(5/0.25) x 100 = 2000 daisies in the field.
Energy for all food chains comes from what source?
Sun
Producers are usually what?
Plants
How is energy in food chains lost?
Respiration and heat
What happens to the biomass at each stage in a food chain?
Decreases
How do decomposers break materials down?
Using enzymes
