Populations in ecosystems

Question 1

What is a community

Answer 1

all populations of different species in the same area at a given time

Question 2

What is an ecosystem

Answer 2

a community and the non living components of an environment

Question 3

What is a niche

Answer 3

an organisms role within the ecosystem, each species has its own niche

Question 4

What are biotic factors

Answer 4

impact of interactions between organisms

Question 5

What are abiotic factors

Answer 5

non-living factors in an ecosystem

Question 6

what is carrying capacity

Answer 6

the maximum population size an ecosystem can support

Question 7

Examples of abiotic factors

Answer 7

pH, temperature, light intensity, oxygen levels, carbon dioxide levels

Question 8

How do plants + animals become adapted to abiotic factors

Answer 8

natural selection

Question 9

how is diversity and population size affected by abiotic factors

Answer 9

extreme abiotic conditions leads to less species diversity and smaller population sizes as less species are likely to survive and reproduce in extreme conditions

Question 10

What is interspecific competition

Answer 10

Biotic factor

members of different species compete for the same resource that is in limited supply

the better adapted individual is less likely to survive and reproduce

Question 11

What is intraspecific competition

Answer 11

Biotic factor

members of the same species compete for resources or a mate

more well adapted individuals will perform more impressive courtship behaviour or have features in better conditions so more likely to attract a mate and reproduce

Question 12

How can predation influence population size

Answer 12

Predator population increases as prey population increase as there are more food sources, so increasing survival for predators but decreasing survival for prey

However as prey population decreases due to increasing predators, this will cause predator population to decrease as there are less food sources

this decrease in predator population causes an increase in prey population and this cycle repeats itself

Question 13

3 ways of estimating population size

Answer 13

quadrats
belt transects
mark release recapture

Question 14

How are quadrats used to estimate population size

Answer 14

used to sample slow or non-motile organisms

place 2 tape measures at right angles to take a gridded area to take samples from

use a random number generator to generate co-ordinates to take samples from, this avoids bias

place quadrat on co-ordinate and count the number of species or calculate percentage cover

repeat this at least 30 times to obtain a representative sample of mean abundance or percentage cover for one quadrat

multiply this value by how many quadrats fit in the total area of field or area you’re investigating

Question 15

How to use a belt transect to estimate population size

Answer 15

Tape measure is placed in a non uniform ecosystem

quadrat placed at intervals along the transect to measure the impact of changes in the environment

count the number of squares the species is present in, the total number of individuals in the quadrat or the percentage cover of the quadrat of the species

Question 16

How is mark release recapture used to estimate population size

what is the equation to estimate

Answer 16

used for motile organisms

animals are trapped and marked with a non toxic, weather resistant substance, also does not influence predation or reproduction

they are released and left to distribute themselves in the population

recaptured a few days later and a 2nd sample is taken, this is repeated at least 10 times to give a representative result

POPULATION SIZE = (SIZE OF 1ST SAMPLE X SIZE OF SECOND SAMPLE)/NUMBER OF MARKED IN 2ND SAMPLE

Question 17

Assumptions made for mark release recapture estimations

Answer 17

Enough time for organisms to distribute themselves

no migration

no births or deaths

marking of the organisms hasn’t made them susceptible to predation

Question 18

What is succesion

Answer 18

a change in an ecological community over time

Question 19

Steps of primary succession

Answer 19

1. a pioneer species colonises bare rock or sand
2. these are adapted to survive harsh abiotic conditions and change abiotic factors to be less harsh through death and decomposition
3. moss and smaller plants can now survive, and they further increase depth and nutrient density of the soil when they die
4. this process continues, and larger plants can survive, which furthers change in the environment
5. each new species can change the environment in a way that the previous species can no longer survive in as they become out competed
6. these changes result in a less hostile environment and increases biodiversity
7. primary succession results in a climax community which is mainly made up of trees

Question 20

How are habitats conserved and what is an example

Answer 20

succession can be manages

this prevents a climax community, so a wider variety of habitats and therefore a higher species diversity

this can provide conflict between human needs and conservation

coppice trees, so timber can be harvested but the tree can still survive