populations in ecosystems

Question 1

what is a community

Answer 1

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

Question 2

what is an ecosystem

Answer 2

a community and the non-living components of an environment
e.g. tropical rainforests, deserts e.t.c
Ecosystems are dynamic and can be of different sizes

when we say that an ecosystem is dynamic we mean that its characteristics can vary over time

Question 3

what is a niche

Answer 3

A niche is an organism’s role within the ecosystem. Each species occupies its own niche this is influenced by abiotic and biotic factors

Question 4

what are biotic factors

Answer 4

impact of interactions between organisms e.g. competition, predation e.tc.

Question 5

what are abiotic factors

Answer 5

non-living factors in an ecosystem

Question 6

what is the definition of carrying capacity

Answer 6

the maximum population size an ecosystem can support

Question 7

what are some abiotic factors that affect population size

Answer 7

• Ph
• soil quality
• temperature
• oxygen levels
• CO2 levels
• light intensity

plants and animals are adapted to abiotic factors, which develop through the process of natural selection

Question 8

when are species diversity and population size at their largest

Answer 8

species diversity and population size is larger when abiotic conditions are less extreme because there is a higher chance that species survive and reproduce and therefore pass their allele to the next generation

Question 9

what are some of the biotic factors that influence population size

Answer 9

interspecific competition

intraspecific competition

predation

Question 10

what is INTERspecific competition

Answer 10

it is when members of DIFFERENT SPECIES compete for the SAME RESOURCES that are in LIMITED SUPPLY e.g. light, water, food e.t.c

The BETTER ADAPTED INDIVIDUAL is more likely to survive and reproduce

Question 11

what is INTRAspecific competition

Answer 11

it is when members of the SAME species compete for RESOURCES and a mate

these resources can be light, water food e.t.c

Question 12

when competing for mates, who is more likely to “win”

Answer 12

when they are competing for mates, the more well-adapted individuals will be able to perform more “impressive” courtship display pr may have features in better conditions e.g. neater feathers

so they will be more likely to attract a mate and reproduce to produce fertile offspring possessing the advantageous alleles that make them more advantageous in getting a mate

this is another factor that affects population size

Question 13

what is predation

Answer 13

predation is another factor that affects population size

It is the interaction between predator and prey

Question 14

how does predation work

Answer 14

predation has a cyclic fluctuation

the predator population increases as the prey increases because there are more food resources, increasing survival

the prey population increases as predator population decreases as they’re less likely to be predated on so survive

Question 15

what are the different ways that we can estimate population size

Answer 15

1. quadrants
2. belt transects
3. mark- release recapture technique

Question 16

how do quadrats work

Answer 16

1. place 2 tape measures at right angles to create a gridded area to take samples from
2. use a random number generator to generate coordinates to take samples (avoid bias)
3. Place quadrat on the coordinate and either count the abundance of the species or calculate species cover
4. Repeat at least 30 times ( to get a representative sample of the whole population)

Question 17

how do belt transects work

Answer 17

1. tape measures are placed through a NON-UNIFORM ECOSYSTEM e.g. a rocky beach (belt transects are a crucial environment as it would be difficult to place a quadrant here)
2. quadrats placed at intersects along the transect to measure the impact of changes in the environment (in an environment that is non-uniform, the abiotic factors are likely to be different) on different populations of species

Question 18

when do we use mark release recapture

Answer 18

this is used for motile organisms e.g. insects

If we used a quadrant for motile organisms, they may move out of the quadrant when sampling leading to inaccuracies

Question 19

how does mark release recapture works

Answer 19

1. animals are trapped and marked with a substance that must be non-toxic ( so it does not kill them),

weather resistant (so it does not wash off)

and not impacted by predation or reproduction (as this would lead to fluctuation in population size which is not what we want in our experiment)

2. released and left to distribute themselves in the populations
3. They’re recaptured a few days later and a 2nd sample is taken. This is repeated 10 times * this is done to get a represented and reliable result

Question 20

how do we work out population size after mark release and recapture

Answer 20

population size = size of 1st sample x size of 2nd sample/ number of marked recaptured

Question 21

what are the assumptions of mark and release

Answer 21

• enough time must pass in order for organisms to distribute themselves
• no migration (they don’t leave the boundary of the investigation)
• no births or deaths (so it does not affect the population size)

Question 22

what is succession

Answer 22

succession changes in an ecological community overtime

Question 23

what are the first steps of primary succession

Answer 23

1. A pioneer species colonises bare rock or sand
2. Pioneer species are adapted to survive harsh abiotic conditions and change abiotic factors to become less harsh through their death and decomposition
3. moss and smaller plants can now survive, and they further increase the depth and nutrient density of the soil as they die
4. this process continues and continues and larger plants can survive because the abiotic conditions are less harsh and change the environment
5. each new species may change the environment in a way that the previous species can no longer survive as they become outcompeted e.g. larger plants block the sunlight for smaller plants
6. these changes result in a less hostile environment and increase biodiversity
7. Final stage of succession is a climax community

Question 24

what is a climax community

Answer 24

it is a community made of mainly one species (usually trees)

Question 25

what is secondary succession

Answer 25

secondary succession happens on land that’s been cleared or all the plants, but where the soil remains e.g. after a forest fire

The established community of species is usually destroyed, but without too much disturbance to the soul

It can occur during any stage (including the climax stage) after the pioneer stage
The process is similar to primary succession, but because there’s already a soil layer, secondary succession starts at a later stage and the pioneer species are larger plants e.g. shrubs

Question 26

what are conservation techniques

Answer 26

to conserve habitats, succession is often managed
e.g. grazing of cows in the field prevents the grass from releasing nutrients into the soil.

By doing this, a climax community is prevented, so there is a wider variety of habitats and therefore higher species diversity

Question 27

what are some issues with conservations

Answer 27

conservation creates a conflict with human needs

To balance this need, we can e.g. coppice trees, which allows the furniture to be made and allows trees to survive

Question 28

what are the different conservation techniques

Answer 28

1. management of succession
2. seed banks
3. captive breeding programmes
4. fishing quotas
5. protected areas

Question 29

what are the assumptions of Hardy Weinberg equation

Answer 29

five conditions must be met:

• no mutation arise
• the population is isolated that is, there is no flow of alleles or our of the population
• there is no selection, that is all alleles are equally likely to be passed to the next generation
• the population is large
• mating within the population is random