Populations A2

Question 1

define community

Answer 1

all populations of different organisms living and interacting in a particular place at the same time

Question 2

define habitat

Answer 2

place where organism usually lives

Question 3

define population

Answer 3

group of individuals of the same species occupying the same habitat at the same time

Question 4

define niche

Answer 4

all conditions and resources needed for an organism to survive and reproduce
how an organism fits into the environment
governed by abiotic and biotic conditions

Question 5

define ecosystem

Answer 5

all the interacting biotic and abiotic features in a specific environment

Question 6

abiotic factors

Answer 6

non-living features of an environment

Question 7

examples of abiotic factors

Answer 7

temperature, pH, light

Question 8

define biotic factors

Answer 8

living features of an environment

Question 9

why use random sampling

Answer 9

to avoid bias

Question 10

how to use a quadrat

Answer 10

set up grid
choose random coordinates using random number generator
measure percentage cover or species frequency
place a large number of quadrats on coordinates and calculate a mean per quadrat
times mean number of plants per quadrat by number of quadrats in the area

Question 11

what does percentage cover measure

Answer 11

abundance

Question 12

when is percentage cover useful

Answer 12

when counting number of individuals is impractical e.g too many, hard to distinguish individuals so finds an estimate

Question 13

cons of quadrats

Answer 13

underestimates small organisms and overestimates large ones

Question 14

define species frequency

Answer 14

number of individuals of each species in a quadrat

Question 15

why use a large number of quadrats

Answer 15

keep going until the mean is stable and there’s enough for a statistical test

Question 16

why is deforestation/the removal of hedgerow bad

Answer 16

fewer species
less habitats
fewer food sources
increase in CO2 in the air since less photosynthesis

Question 17

why do farmers benefit from the removal of hedgerow

Answer 17

more predators for pests able to get in

Question 18

when to use a transect

Answer 18

when there is a transition in the environment

Question 19

how to make a transect

Answer 19

place quadrats at a regular interval along the line
count plants/percentage cover
use several quadrats
may not be representative of area

Question 20

how to do mark release recapture

Answer 20

capture smaple, mark and release
appropriate method of marking (doesn’t harm/rub off)
take a second sample and count marked organisms
population = number in sample 1 x number in sample 2/number marked in sample 2

Question 21

assumptions of mark release recapture

Answer 21

population must remain stable
no emigration/immigration
no loss to predation
marking does not affect survival
birth rate and death rate equal
all belong to one population

Question 22

define carrying capacity

Answer 22

ecosystem can only support populations of a specific size

affected by abiotic factors, inter and intraspecific competition and predation

Question 23

define intraspecific competition

Answer 23

between members of same species

Question 24

define interspecific competition

Answer 24

between members of different species

Question 25

when does interspecific competition stop

Answer 25

when one species outcompetes the other for things like food space light breeding territory

Question 26

why are predator prey relationships difficult to work out

Answer 26

they are hard to show in a lab

data from natural environments should be taken with caution