3. Investugating Population

Question 1

What 2 things do you need to look at when investigation populations of organisms ?

Answer 1

Looking at abundance

Distribution of species in area

Question 2

Define abundance

Answer 2

Number of individuals of one species in a particular area

Question 3

How can abundance be estimated C

Answer 3

• Simply counting number of individuals in sample taken
• frequency - number of samples a species is recorded in
• percentage cover ( slow moving species only ) how much of the area you’re investigating is covered by a species

Question 4

Define distribution

Answer 4

Where a particular species is within the area you’re investigating

Question 5

Random sampling method

Answer 5

• choose area to sample
• sample should be random to avoid bias - number generator
• appropriate technique to take sample
• repeat process taking as many sample as possible - reduce liklihood they’re down to chance
• number of individual for whole area now estimated by taking the mean of the data collected in each sample and multiply it by size of whole area

Question 6

Random number generators

Answer 6

Divide field into a grid
Using random number generator and letter generator to select coordinates

This will be random no bias

Question 7

Running means

Answer 7

Work out the mean of the data each time you collect a new sample

Once the mean no longer changes by a large amount you should have data that gives realistic estimate for whole area

This will be different in each study

Question 8

Name 3 methods of investigating populations

Answer 8

1 quadrats

2 transects

3 capturing motile organisms

All depends upon organism and habitation

Question 9

What are quadrats and transects used for V

Answer 9

Non motile organisms

Like plants or coral
Slow moving

Question 10

None motile organism

Answer 10

Don’t move around

They’re fixed to surface

Sessile organisms

Question 11

What is a wuadrat ?

Answer 11

Square frame divided into a grid of 100 smaller squares by strings in frame

Question 12

How to use quadrats

Answer 12

Placed on ground at different points within area investigation

Species frequency
Number of individuals in each quadrat
% cover of species

Are ways ^^ you can measure

Question 13

When would you use transects

Answer 13

Organisms distribution over area

Sand across dune to woodland
Psammosere

Question 14

Name 2 types of transects

Answer 14

Belt transects

Interrupted transects

Question 15

Belt transects

Answer 15

Quadrats placed next to each other along the transects to work out species frequency and % cover along the transects

Question 16

Interrupted belt transects

Answer 16

Instead of investigating whole transects you can take meatremenr using quadrats placed at regular intervals

Every 2 metres

Large distance covered - quicker but less info given

Question 17

Capturing motile organisms

Answer 17

Depends upon your study

• flying - sweep net
• aquatic - net
• ground insects - pitfall trap