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Biology Unit 4 > Populations > Flashcards

Populations Flashcards

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1
Q

What is a population?

A

All the organisms of one species in a habitat.

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2
Q

What is a community?

A

Populations of different spices in a habitat makes up a community.

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3
Q

What is an ecosystem?

A

All of the organisms in particular area and all of the non-living (abiotic) conditions.

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4
Q

What are abiotic conditions?

A

The non-living features of the ecosystem, e.g. Temperature and availability of water.

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5
Q

What are biotic conditions?

A

The living features of the ecosystem, e.g. The presence of predators or food.

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6
Q

What is a niche?

A

The role of a species within its habitat, e.g. What it eats and where and when it feeds.

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7
Q

What is an adaption?

A

A feature that members of a species have which increases their chance to survive and reproduce.

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8
Q

Why happens when 2 species try to occupy the same niche?

A

If 2 species try to occupy the same niche they will compete with each other for food, resources, etc. One species will be better adapted to living in the niche, e.g. It is better at finding food. Therefore, the less successful species will be out competed for food and it won’t get enough food so only the most successful species will be able to occupy the niche.

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9
Q

What is natural selection?

A

Natural selection is when the organisms with better adaptations are more likely to survive and reproduce and so pass on the alleles for their adaptations. Therefore the advantageous alleles become more common in the population.

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10
Q

Why do you have to take a sample of the area your investigating?

A

You should take a sample of the area you are investigating because it would be too time consuming to measure the number of individuals and distribution of species in the entire area.

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11
Q

How can you avoid bias when taking a sample?

A

You can divide the area you are investigating into a grid by laying out 2 tape measures and you can use a random number generator to select coordinates.

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12
Q

What is abundance?

A

The number of individuals of one species in a particular area.

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13
Q

How can you measure the abundance of an organism?

A

You can simply count the number of individuals.

You can calculate the frequency by seeing how many of the samples a species is recorded in.

You can calculate percentage cover by seeing how much of the area is covered by a species.

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14
Q

What is frequency?

A

The number of samples a species is recorded in.

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15
Q

What is percentage cover?

A

How much of the area is covered by a species. (For plants only).

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16
Q

What is distribution?

A

Where a particular species is in the area being investigated.

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17
Q

What are quadrats useful for?

A

Quadrats are useful for quickly investigating areas with plant species that fit within a small quadrat.

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18
Q

How can you calculate percentage cover by using a quadrat?

A

You can place the quadrat on the ground and count how much of the quadrat is covered by the species. You count a square if it is more than half covered.

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19
Q

Why is percentage cover a good way to investigate populations?

A

It is a quick way to investigate populations and you don’t have to count the individual plants.

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20
Q

What is the purpose of transects?

A

Transects are used to find out how plants are distributed across an area, e.g. How species change from a hedge towards the middle of a field.

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21
Q

What are the 3 types of transects?

A

Line transects, belt transects and interrupted transects.

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22
Q

What is a line transect?

A

A line transect is when a tape measure is placed along a transect and the species which touch the tape measure are recorded.

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23
Q

What is a belt transect?

A

A belt transect is when quadrats are placed next to each other along a transect to calculate species frequency and percentage cover along the transect.

24
Q

What is an interrupted transect?

A

An interrupted transect is when you place quadrats and take measurements at intervals along a transect.

25
Q

What is mark release recapture?

A

Mark release recapture is when you measure the abundance of a mobile species. You capture a sample of a species and count them. You mark them in a way that doesn’t affect their survival. You release them back into their habitat. Wait for a while so the marked ones can mix back into the habitat. Capture a second sample and count them. Count how many of the second sample are marked.

26
Q

What is the equation for mark release recapture?

A

Number in 1st sample x number in 2nd sample / number marked in 2nd sample.

27
Q

What are the assumptions you make when doing a mark release recapture experiment?

A

The marked sample has had time to mix back into the population.
The marking hasn’t affected the individuals chance of survival - e.g. By making them more vulnerable to predation.
That there is no change in the size of the population of the species, e.g. By births, deaths, etc.

28
Q

What is interspecific competition?

A

Interspecific variation is when organisms of different species compete with each other for the same resources.

29
Q

How does interspecific competition affect 2 species?

A

If 2 species are in competition there will be less resources available to both species. Therefore both populations will be limited, e.g. They will have less food each so they will have less energy for growth and reproduction. So the population size of both species will be lower.

30
Q

What happens when 2 species compete with each other?

A

If 2 species compete with each other but one is better adapted then the less well adapted species will be out competed for food and resources and it won’t be able to survive alongside the better adapted species.

31
Q

What is intraspecific competition?

A

Intraspecific competitor is when organisms of the same species compete with each other for the same resources.

32
Q

How does a population size vary during intraspecific competition?

A

The population of a species increases when resources are plentiful. As the population increases there will be more organisms competing for the same amount of space and food. Eventually, resources and space become limiting so there isn’t enough for all the organisms so the populations begins to decline. Therefore there is a smaller population so there is less competition for space and food and the population begins to grow again.

33
Q

What is predation?

A

Predation is when an organism kills and eats another organism.

34
Q

How do predator and prey relationships vary?

A

As the prey population increases there is more food for predators, so the predator population grows. As the predator population increases more prey gets eaten so the prey population declines. This means there is less food for predators so the predator population decreases.

35
Q

Why can organisms population increase in ideal conditions?

A

In ideal conditions animals don’t have to use up as much energy maintaining their body temperature, so more energy can be used for growth and reproduction. Therefore the population size increases.

36
Q

Why can’t organisms population Increase as fast in non ideal conditions?

A

In non ideal conditions animals have to use more energy in maintaining their body temperature, so they have less energy for growth and reproduction. Therefore the population size will decrease.

37
Q

What is birth rate?

A

Birth rate is the number of births every year for every 1000 people in the population.

38
Q

What is death rate?

A

Death rate is the number of deaths every year for every 1000 people in the population.

39
Q

What is population growth rate?

A

Population growth rate is how much the population size increases or decreases in a year.

40
Q

How can you calculate population growth rate?

A

Population growth rate (per 1000 people per year) =

Birth rate - death rate

41
Q

What is the demographic transition model (DTM)?

A

The demographic transition model is a graph which shows the changes in birth rate, death rate and total population size for s human population over a long period of time.

42
Q

What happens on stage 1 of the demographic transition model?

A

In stage 1 the birth rate and death rate are very high and they fluctuate. The total population is low.

43
Q

Why is the birth rate and death rate high in stage 1 of the Demographic transition model?

A

The birth rate is high because there is no birth control or family planning and education is poor. Lots of children die at a young age so parents have more children so enough survive to work and look after them.
Death rate is high because there is poor health care, sanitation and diet, which leads to disease and starvation.

44
Q

What happens in stage 2 of the demographic transition model?

A

The birth rate remains high and the death rate falls, lower that the death rate of stage 1. The population increases rapidly because the birth rate becomes much higher than the death rate.

45
Q

Why does the death rate fall and the birth rate remain high in stage 2 of the demographic transition model?

A

Death rate falls because health care, sanitation and diet improve. Birth rate remains high because there is still little birth control or family planning.

46
Q

What happens in stage 3 of the demographic transition model?

A

In stage 3 the birth rate falls rapidly and the death rate falls, but more slowly. The population increases at a slower rate.

47
Q

Why does the birth rate fall rapidly in stage 3 of the demographic transition model?

A

The birth rate falls rapidly because of the use of brith control and family planning. Also, the economy becomes more based on manufacturing rather than agriculture, so fewer children are needed to work.

48
Q

What happens is stage 4 of the demographic transition model?

A

The birth rate and death rate are low and they fluctuate at a low level. The population is stable but high.

49
Q

Why is the birth rate low in stage 4 of the demographic transition model?

A

The birth rate is low because there is more demand for luxuries, so less money is available to raise children. Children are not needed to work so parents have fewer children.

50
Q

What happens in stage 5 of the demographic transition model?

A

The birth rate begins to fall and the death rate remains stable. The population starts to decrease.

51
Q

Why does the population start to decrease in stage 5 of the demographic transition model?

A

The birth rate falls below the death rate because children are expensive to raise and people often have dependant elderly relatives. The death rate remains steady because larger generations of elderly people die.

52
Q

What do survival curves show?

A

Survival curves show the percentage of individuals that were born in a population that are still alive at any given age.

53
Q

What do age population pyramids show?

A

Age population pyramids show how many males and how many females there are in every age group in a population.

54
Q

What do population growth curves show?

A

Population growth curves show how the population changes over time.

55
Q

What is a habitat?

A

The place where an organism lives.

Biology Unit 4 (5 decks)

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