Investigating population and succession Flashcards
What is ecology?
The study of how organisms interact with each other and their environment.
What is a species?
A group of closely related individuals, which are capable of interbreeding and producing fertile offspring
What is a population?
All the individuals of a given species living together in the same area at the same time
What is carrying capacity?
Maximum, equilibrium number of organisms of a particular species that can be supported indefinitely in each stable environment.
Birth rates and death rates are in equilibrium
What is a community?
All the individuals of all the species living together in the same area at the same time
What is a habitat?
The place where an organism lives within an ecosystem
What is a niche?
Describes where an organism lives and what it does (its role). This includes what it feeds on and how it interacts with other organisms and the environment
What is the abundance of a species?
Population size of each species
When estimating, to ensure that the data is not biased what must we do?
Samples must be selected at random
When estimating, to ensure that the data collected is reliable, representative and suitable for statistical analysis, what must we do?
Large number of sample must be taken (more than 20)
How can we check that a large enough sample is used?
If you calculate a new mean value after each sample is taken (this is called a running mean), enough samples have been taken when this running mean shows no change
What is a quadrat?
A frame of known area, which is placed on the ground and an estimation of the population size within the quadrat is made
In what ways can we determine the abundance of species within a quadrat?
Density
Percentage cover
Frequency
How is density used to measure abundance of species within a quadrat?
Actual count of all individuals present
What are the advantages of using a quadrat?
Most accurate
What are the disadvantages of using a quadrat?
Often time consuming
Some species can be difficult to count
How is percentage cover used to measure abundance of species within a quadrat?
The area of the quadrat covered by one species is recorded as a percentage of the total area
Used when there are too many individuals to count
What is a disadvantage of using percentage cover?
In some situations, over layering of species may occur (stratification), therefore, the total percentage cover may be more than 100%
How is frequency used to measure abundance of species within a quadrat?
The proportion of quadrats that contain a particular species
What is a disadvantage of using frequency?
Least accurate
Why is random quadrating done?
To find out what species are present and their relative abundance in a specified area
Compare the species abundance in two different areas
Compare the species abundance at one site (one area) at different seasons/years
When is random quadrating used?
To study stationary or very slow moving populations with fairly uniformed distribution across area
What is the method of random quadrating?
Map the area using two measuring tapes arranged at right angles to each other to form the axes of a grid
Use a random number generator to obtain a serious of random coordinated
Place a quadrat at the intersection of these coordinates
Abundance can then be estimated using a quadrat by:
- frequency, % cover or density
How many quadrats should you use in the sample?
Calculate a running mean
Stop sampling when there is little change
Enough to carry out a statistical test
A large number to make sure mean is reliable (20 or more)
Need to make sure work can be carried out in the time available
Describe how you would determine the mean percentage cover for beach grass on a sand dune (3 marks)
Use a random generator to obtain a series of coordinates
Use a large number/sample of quadrats
Divide total percentage by number of quadrats/samples
What can systematic sampling consist of?
Transect
Belt transect
Interrupted belt transects
How is a transect used in systematic sampling?
Recording what species are touching the line at each sampling point
How is a belt transect used in systematic sampling?
Placing two parallel lines across, a meter apart and recording what species are found between the two lines
How is an interrupted belt transect used in systematic sampling?
Using one line and placing a quadrat down at equally spaced sampling points and recording abundance of species within the quadrat
When carrying out systematic sampling, what must we ensure?
The position of the transect across the area should be random
Enough transects should be performed to ensure data collected is reliable
Describe how you would investigate the distribution of marram grass from one side of the dune to the other
Transect/lay tape measure from one side of the dune to the other
Place quadrat at regular intervals along the line
Count plants/percentage cover OR count plants and record where they touch the transect
What technique is used to estimate the population size of moving/mobile species (animals)?
Mark-release-recapture
What is the method of mark-release-recapture?
animals of a particular species are ethically collected and counted
- the animals are then marked in some way that does not affect ability to feed or increase chance of predation
- the animals are then released and left to redistribute into their population
- after a reasonable time, a second capture is carried out and the total number caught is recorded, as well as how many of those released and recaptured which were previously marked
How is the population size calculated using mark-release-recapture?
(number caught first time x number caught second time) / number caught second time which were marked
What things must be considered when mark-release-recapture is done?
The population size does not change between the two capture times (very few or no increase in birth/death rate or migration)
The marking should not make the marked animals more susceptible to predators or harm them
The marking should not rub off or be lost
Sufficient time should be left for the released
Species should be studied in situ and not removed from the position. Why?
If moved, behaviour will be altered
If removal or disturbance is necessary, the individuals should be returned to the same spot if possible. Why?
More likely to integrate back into their population
As few individuals as possible should be removed. Why?
Don’t want to effect the natural population
There should be minimal damage to organisms or the habitat. Why?
Don’t want to effect the natural population
Sites should not be overused and be given time to recover. Why?
Don’t want to effect the natural population
