Populations and Ecosystems - B11

Question 1

Define habitat.

Answer 1

the place where an organism lives within an ecosystem

Question 2

Define community.

Answer 2

all the different populations of different species in a habitat.

Question 3

Define environment/ecosystem.

Answer 3

the set of conditions that surround an organism, consisting of biotic factors and biotic factors

Question 4

What is a biotic factor?

Answer 4

living features if the ecosystem

Question 5

What is an abiotic factor?

Answer 5

non-living features of the environment

Question 6

What factors reduce population size?

Answer 6

predation, human activity(hunting, pesticides), disease/parasites, intraspecific competition, interspecific competition

Question 7

Define niche.

Answer 7

the role of an organism within it’s ecosystem including it’s biotic and abiotic interactions e.g. what it eats, where and when it feeds

Question 8

What is included in the niche a species occupies?

Answer 8

-it’s biotic interactions
-it’s abiotic interactions, e.g. the temp range an organism can live in, the time of day it’s active

Question 9

What are the implications of no two species having the same niche?

Answer 9

if species don’t have the same niche, there is no/less interspecific competition for resources such as food

Question 10

What is the competitive exclusion principle?

Answer 10

if two species have the same niche, one will outcompete the other.

Question 11

What is an adaptation?

Answer 11

An adaptation is a feature of a species that increases their chances of survival and reproduction. It can be physiological, physical or behavioural.

Question 12

What is population size?

Answer 12

The total no. of organisms of one species in a habitat.

Question 13

What is the carrying capacity?

Answer 13

The maximum population size of a species that an ecosystem can support. It varies as a result of biotic and abiotic factors.

Question 14

How do abiotic factors effect population size?

Answer 14

-the pop. size of any species varies due to abiotic factors
-e.g. the amount of light, water or space availability, temperature, chemical composition of surroundings
-when abiotic conditions are favourable, organisms grow and reproduce successfully

Question 15

What intraspecific competition?

Answer 15

competition between individuals of the same species

Question 16

Why is intraspecific competition a cyclical change?

Answer 16

-population grows and changes continuously
-population grows when resources are plentiful
-resources become limited so population decreases
-smaller population means less competition so more growth and reproduction occurs

Question 17

What is interspecific competition?

Answer 17

competition between organisms of different species for the same resources
-the resource to the populations could be limited to both populations
-or if two organisms are competing but one is better adapted, the less adapted species is likely to be out-competed

Question 18

How do the populations of prey and predator change due to predation?

Answer 18

-their populations interlinked, as the population of one changes, so does the other.
-as prey population increases, there’s more food for predators, so predator population grows
-as the predator population increases, more prey are eaten so the prey population then begins to fall
-less food for predators, so predator population decreases

Question 19

Why do we use a log graph?

Answer 19

the range between the smallest and largest number is too big, so allows for a large range to be plotted.

Question 20

What are the mark points for quadrat questions?

Answer 20

-grid the area you want to sample
-take random samples to remove bias
-use a random no. generator to generate coordinates to take samples at
-place quadrat at that coordinate and count the number
-take a large sample by repeating many times(which makes the sample representative)
-running mean can be calculated and when the running mean stabilises, enough samples have been taken
-calculate mean per quadrat
-multiply per quadrat by number of quadrats that fit into the area(other methods are available)

Question 21

define population

Answer 21

a group of the same species in a particular space at a time, that can interbreed.

Question 22

Why do we take samples?

Answer 22

to estimate numbers of plants and animal species in a particular habitat, to estimate the numbers of each organisms

Question 23

What are the different methods for investigating populations?

Answer 23

-quadrats
-used for studying non-motile organisms
-always a known size e.g. 1m^2 or 0.25m^2
-a square frame divided into a grid of 100 smaller squares

Question 24

define abundance

Answer 24

the number of individuals of one species in a particular area(i.e. population size)
-can be estimated by counting the number of individuals in samples.

Question 25

define frequency

Answer 25

the number if samples a species is recorded in - e.g. 70% of samples

Question 26

define percentage cover

Answer 26

how much of an area you’re investigating is covered by a species

Question 27

how is percentage cover estimated?

Answer 27

-visual estimate
-if over half the square is covered, count it

Question 28

define distribution

Answer 28

where particular species is within the area you’re investigating

Question 29

Why do we use random sampling?

Answer 29

too time consuming to count every organism so instead we take samples

Question 30

What are the mark points for random sampling?

Answer 30

1)choose a small area within the area being investigated
2)some samples should be random to avoid bias. Use a random number generator
3)use appropriate technique to sample
4)take a large sample so that data is representative
5)take mean of data and multiply by size of the whole area

Question 31

How is the running mean calculated?

Answer 31

-the running mean is calculated each time a new sample is collected
-once the mean no longer changes by a large amount, stop sampling, as you have a representative estimate for that area

Question 32

What is a transect?

Answer 32

lines across an area if interest can help you to find out how organisms are distributed across an area

Question 33

What is a belt transect?

Answer 33

Quadrats are placed next to each other along the transect to sample species along the transect

Question 34

What is an interrupted belt transect?

Answer 34

Quadrats placed at regular intervals - makes it easier to sample over large distances

Question 35

What are the mark points for a transect question?

Answer 35

-randomly place transect down across sampling area using random coordinates using a random number generator
-place quadrat down at regular intervals along transect
-record abiotic factor
-repeat many times at other randomly placed lines across the area
-until the running mean does not vary much

Question 36

What is mark-release-recapture?

Answer 36

a method used to measure the abundance of more mobile species

Question 37

What are the mark points for mark-release-recapture questions?

Answer 37

1)capture a sample of species and count
2)mark in a harmless way e.g. spot of paint or tag
3)release back into habitat
4)wait a set amount of time and take a second sample from the same population
5)count how many of the sample are marked
6)calculate total population using equation:
total population= no. caught in 1st sample x no. caught in second sample / no. marked in second sample

Question 38

What ways do we evaluate the accuracy of MRR?

Answer 38

1)the marked sample has had enough time and opportunity to mix back into the population
2)marking is not toxic so doesn’t effect survival
3)marking doesn’t make more visible to predators
4)marking doesn’t was off so recaptured organisms can be identified
5)there are no changes in population size sue to births, deaths or migration during the period of study

Question 39

What are some of the ethical issues with MRR?

Answer 39

-could cause the animals unnecessary stress - could reduce their chances of survival on release
-animals may learn not to be trapped the next time - skewing the results
-to minimise stress, investigations should be planned so that organisms are treated carefully and kept and handled as little as possible