B4a Flashcards
What two ways are there too estimate population size?
Scaling up from a small area.
Using capture - recapture.
How do you use the scaling up from a small sample area method to estimate population size?
A quadrat is a square frame enclosing a known area. You can study the small area within a quadrat and scale up your findings to make estimates for larger areas:
1) Count all the organisms in a 1m squared quadrat.
2) Multiply the number of organisms by the total area (in m squared) of the habitat.
How do you use capture-recapture to estimate population size?
1) Capture a sample of the population and mark the animals in a harmless way.
2) Release them back into the environment.
3) Recapture another sample of the population. Count how many of this sample are marked.
4) Estimate population size using this equation:
population size = number in first sample x number in second sample / number in second sample previously marked
How does the sample size affect the accuracy of the estimate?
The bigger your sample, the more accurate your estimate of the total population is likely to be.
When using capture-recapture data, what assumptions need to be made?
1) There have been no changes in the population size due to deaths, immigration (individuals moving into the area) or emigration (individuals moving out of the area).
2) The sampling methods for the capture and recapture were identical (e.g. the pitfall trap was set up in the same way each time)
3) The marking hasn’t affected the individuals’ chance of survival (e.g. by making them more visible to the predators).
What is the difference between an ecosystem and a habitat?
An ecosystem is all the organisms living in a particular area, as well as the non-living (abiotic) conditions, e.g. temperature, salinity and soil quality. An ecosystem isn’t the same as a habitat - a habitat is just the place where an organism lives.
What is the difference between a population and a community?
A population is all the organisms of one species in a habitat (the place where an organism lives). Populations of different species in a habitat make up a community.
What does it mean for an ecosystem to be self supporting in all factors other than an energy source?
Ecosystems are self supporting - they contain almost everything they need to maintain themselves. Water, nutrients and essential elements like carbon all get recycled within the ecosystem. The only thing that’s needed from outside the ecosystem is an energy source. This is normally the sun.
How do you map the distribution of organisms in a habitat using a transect line?
1) Transects are used to describe the distribution of organisms.
2) Distribution is where organisms are found within a particular area. You can investigate distribution using lines called transects.
3) To do a transect, you mark out a line using a tape measure and place quadrats next to each other all the way along the line. You then count and record the organisms you find in the quadrats.
4) If it’s difficult to count all the individual organisms in the quadrat you can calculate the percentage cover. This means estimating the percentage area of the quadrat covered by a particular type of organism, e.g. by counting the number of little squares covered by the organisms.
5) You can plot the results of a transect line in a kite diagram. This allows you to map the distribution of organisms in an area.
How do you interpret data from kite diagrams?
Kite diagrams show the distribution and abundance (number) or organisms along a transect.
The abundance of each organism is shown by the thickness of the kite shape. The abundance is plotted above and below a central line to make the shape symmetrical, on the y axis as a percentage.
The x axis shows the distance along the transect line.
What is zonation?
The gradual change in the distribution of species across a habitat.
How can a gradual change of an abiotic factor result in the zonation of organisms in a habitat?
Abiotic factors are all the non-living, physical factors in an environment - e.g. light, temperature, water, oxygen, salinity (salt level) and soil quality. The distribution of organisms is affected by abiotic factors because organisms are adapted to live in certain physical conditions.
A gradual change in abiotic factors can lead to zonation of organisms in a habitat.
For example, in a coastal habitat, changes in salinity and soil depth result in zones where different types of plants grow.
What is biodiversity?
Biodiversity is the measure of the variety of life in an area. Biodiversity includes:
1) The amount of variation between individuals of the same species in an area.
2) The number of different species in an area.
3) The number of different habitats in an area.
What is the difference between natural and artificial ecosystems?
Natural ecosystems have a higher biodiversity than artificial ones. Natural ecosystems maintain themselves without any major interference from humans - e.g. native woodlands and natural lakes. Artificial ecosystems are created and maintained by humans - e.g. forestry plantations and fish farms.
Compare the biodiversity of native woodlands and forestry plantations.
Native woodlands have a higher biodiversity than forestry plantations.
Native woodlands:
1)Variety of tree species - e.g. birch, hazel, oak.
2) Trees are different sizes and ages.
3) Variety of plant species - e.g. flowers, shrubs.
4) Variety of habitats - e.g. different trees and shrubs for birds to nest in, different types of leaf litter for invertebrates to live in.
5) Variety of animal species - e.g. different species of invertebrates, birds and mammals.
Forestry Plantations:
1) One species of tree is planted for timber - e.g. pine, fir.
2) Blocks of trees are planted at the same time - so many trees are the same age.
3) Fewer plant species because trees are densely planted - leaving less room and light for other plants.
4) Fewer habitats because there aren’t enough plant species to create them.
5) Fewer animal species because there aren’t as many habitats or sources of foods.
