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Biology-19-Populations In Ecosystems > Investigating Populations > Flashcards

Flashcards in Investigating Populations Deck (13)
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What is the abundance

The number of individuals of a species In a given space


What are the two types of quadrant

A point quadrant

A frame quadrat


What’s a point quadrat

Consists of a horizontal bar supported by two legs. A set intervals along the horizontal bar are ten holes, through each of which a long pin may be dropped. Each species that touches the pin is recorded


What’s a frame quadrat

A square frame divide by string or wire into equally sized subdivisions. The quadrat is placed in different locations within the area being studied. What he abundance of each species within the quadrat is recorded

It is often designed so that it can be folded to make it more compact for storage and transport


What are the three factors to consider when using quadrats

Size of the Quadrat to use- will depend on the size of the plays or animals being counted and how they are distributed within the area

The number of sample quadrat s to record within the study - the larger the number of samples the more reliable the results will be.

The position of each quadrat within the study area - to produce statistically significant results a technique called random sampling must be used


How do we do random sampling

1. Lay out two long tape measures at right angles, along two sides of the study area

2. Obtain a series of coordinates using a random numbers from a generator

3. Place a quadrat at the intersection of each pair of coordinates and record the species within it


How do we do systemic sampling along belt transects

1. Stretching a string or take across the ground Ina straight line

2. A frame quadrat is laid down alongside the line and the species within it recorded

3. It’s then moved it’s own length along the line and the process is repeated

4. This gives a record of species in a continuous belt


What is frequency

It’s the likelihood of a particular species occurring in an quadrat

Gives a quick idea of the species present and their general distribution within an area (e.g. grass)


What is percentage cover

Is an estimate of the area within a quadrat that a particular species covers

Useful when a species is difficult to count

It is quick however doesn’t count overlapping


What is necessary to obtain reliable results

Large sample size - many quadrats are used and the mean of all the samples is obtained

The larger the number of samples, the more representative of the community as a whole will be the results


What’s the formula for estimated population size in mark release recapture

Estimated population size = total no. Of individuals caught in 1st sample x total no. Of individuals caught in 2nd sample / number of marked individuals in 2nd sample


Describe the mark release recapture test

1. Capture a sample of species using an appropriate technique

2. Mark them in a harmless way

3. Release them back into their habitat

4. Wait a week, then take a second sample from the same population

5. Count how many of the second sample are marked. You can use the equation to estimate population size


What assumptions does the recapture release technique rely on

The marked sample has had enough time and opportunity to mix and in with the population

Population has a definite boundary so that there is no immigration into or out emigration out of the population

The marking hasn’t affected the individuals chance of survival and the marking itself is still visible

No changes in population sizes due to births, deaths and migration during the period of study