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A2 Biology - unit 4 > Unit 3.4.1 - Populations > Flashcards

Unit 3.4.1 - 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 species.

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3
Q

What is an ecosystem?

A

All the organisms living in a certain area and the non living conditions (abiotic, and biotic).

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4
Q

What are the biotic conditions?

A

The living features of an ecosystem.

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5
Q

What are the abiotic conditions?

A

Non living features of an ecosystem.

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6
Q

Give two examples of biotic conditions.

A

Animals and plants that live within the ecosystem.

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7
Q

Give two examples of abiotic conditions.

A

Temperature and soil within the ecosystem.

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8
Q

What is a habitat?

A

The place where an organism lives within the ecosystem.

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9
Q

What is a niche?

A

The role of a species within a habitat.

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10
Q

What can a niche be split into?

A

Biotic interactions and abiotic interactions.

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11
Q

What is a biotic interaction?

A

What the organism eats or what it is eaten by.

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12
Q

What is an abiotic interaction?

A

The temperature range the organism can live in or the time of the day it is active.

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13
Q

What is meant by niches are unique?

A

They can only be occupied by one species.

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14
Q

What is an adaptation?

A

A feature that some members of a species have that mean it is better suited to its environment.

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15
Q

What three categories can adaptations be split into?

A

Physiological, behavioural and anatomical.

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16
Q

What two things are you looking at when investigating populations?

A

Abundance and distribution of species.

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17
Q

What is the abundance of a species?

A

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

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18
Q

What two ways can you look at the abundance of a species?

A

The frequency of the species or by using percentage cover.

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19
Q

What does distribution of the species mean?

A

Where a particular species is within a given area.

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20
Q

Why are samples of the population taken when investigating population size?

A

It would be too time consuming and often impossible to measure the frequency distribution of every member of the population.

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21
Q

Why should samples be random?

A

To avoid bias.

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22
Q

Why should you repeat your results?

A

It allows you to outline any anomalous results and make your results more reliable.

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23
Q

How can you make sure your results are accurate?

A

Large sample size and create a running mean.

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24
Q

When do you stop taking a running mean?

A

When the mean no longer changes.

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25
Q

What are two methods of taking samples?

A

Quadrats and transects.

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26
Q

What is a quadrat?

A

Square frame divided up into grids.

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27
Q

How you would choose where to put your quadrat down?

A

Split your area up into a grid and assign coordinates to each square. Then use a random number generator to create coordinates for you to put the quadrat down at.

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28
Q

When measuring percentage cover of a species when do you count each square as a percentage?

A

If it is more than half covered.

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29
Q

Why is the percentage cover sometimes quicker than measuring the frequency of species?

A

You don’t have to count all the individual plants.

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30
Q

What you can use a transect for?

A

To see how plants and animals are distributed across an area.

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31
Q

Name three types of transects.

A

Line, belt and interrupted.

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32
Q

How do you use a line transect?

A

You place a tape measure along the transect and then count the species that touch the tape measure.

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33
Q

How do you use a belt transect?

A

You place quadrats next to each other along the transect and calculate the species frequency or percentage cover.

34
Q

How do you do an interrupted transect?

A

Same method as line or belt transects but you only take measure at certain intervals or at random points.

35
Q

What is mark-release-recapture?

A

A method used to measure the abundance of more mobile species.

36
Q

How do you carry out mark-release-recapture?

A

Capture a sample of the species and mark them in a harmless way. Release them back into their habitat. Wait for a suitable amount of time. Take the second sample and count how many of them have markings from before.

37
Q

During mark-release-recapture why do you have to mark them in a harmless way?

A

So that it doesn’t affect their chance of survival.

38
Q

What is the equation to estimate the population size from mark-release-recapture.

A
39
Q

What is the accuracy of the mark-release-recapture?

A

Whether the marked sample has had enough time and opportunity to mix back in with the population.

40
Q

What do you have to ensure when doing the m-r-r method?

A

There is any great population size changes due to birth, deaths or migration.

41
Q

What is a risk assessment?

A

Something that identifies the risks during fieldwork and how to reduce the chances of them happening.

42
Q

What are the two ethical issues that surround doing fieldwork?

A

You can damage the environment or affect organisms that live there.

43
Q

Give one example of damage to the environment and what it is caused by.

A

Soil erosion by increased footfall.

44
Q

Give one example of how fieldwork can affect organisms.

A

It can cause them stress.

45
Q

What is a causal relationship?

A

When a change in one variable changes the other.

46
Q

When can a causal relationship be called correlation?

A

When every other variable is controlled so you know it is a direct change that causes the final change.

47
Q

Give four abiotic factors that can affect population size.

A

Amount of light, water or space available and temperature.

48
Q

Give three biotic factors that can affect population size.

A

Interspecific competition, intraspecific competition and predation.

49
Q

What is interspecific competition?

A

When organisms of different species compete with each other for the same resources.

50
Q

What is intraspecific competition?

A

When organisms of the same species complete with each other for the same resources.

51
Q

What type of change can intraspecific competition cause to a population size?

A

Cyclic change.

52
Q

Why can intraspecific competition cause cyclic change in population size?

A

When the population increases there will be more organisms competing for the same resources. Eventually the resources become limited and there isn’t enough for all the organisms. So the population declines. Smaller population means there is less competition and so more organisms will survive and reproduce increasing the population.

53
Q

What is predation?

A

When predators kill and eat the prey.

54
Q

Population of predators and prey are said to be?

A

Interlinked.

55
Q

Why are population sizes or predators and prey said to be interlinked?

A

As the population of the prey increases there is more food for the predators. The size of the predator population begins to increase. As more of the prey is eaten their population begins to decline. There is less food for predators. Predator population declines. With less predators more prey can survive and reproduce. Increase in prey population size.

56
Q

What are the main two factors that affect human population size?

A

Birth rate and death rate.

57
Q

What is birth rate?

A

The number of live births every year per 1000 people in the population.

58
Q

What is death rate?

A

The number of people that die every year for every 1000 people in the population.

59
Q

What is population growth also known as?

A

Natural increase.

60
Q

What is population growth rate?

A

How much the population size increases or decreases in the year.

61
Q

How do you calculate population growth rate?

A

Birth rate - death rate.

62
Q

What is population growth rate measured in?

A

per 1000 people per year

63
Q

What is the DTM?

A

A graph that shows how the birth rate, death rate and total population size has changed over a long period of time.

64
Q

How many stages is the DTM split up into?

A

Five

65
Q

What happens during stage 1 of the DTM?

A

Birth date and death rate fluctuate at high level so the total population remains low.

66
Q

What are four reasons why birth rate is high during stage 1 of the DTM?

A
  1. There is no birth control 2. No family planning 3. Education is poor 4. High infant mortality rate so parents have more children so more will survive to adulthood
67
Q

What are three reasons why death rate is high during stage 1 of the DTM?

A
  1. Bad healthcare 2. Bad sanitation 3. Bad diet … leading to disease and starvation
68
Q

What happens during stage 2 of the DTM?

A

Death rate begins to fall but birth rate remains high so the total population increases rapidly.

69
Q

Why does the death rate fall during stage 2 of the DTM?

A

Improvement in healthcare, sanitation and diet.

70
Q

What happens during stage 3 of the DTM?

A

Birth rate begins to fall rapidly and death rate begins to fall more slowly so the total population begins to increase at a slower rate.

71
Q

Give four reasons why the birth rate falls during stage 3 of the DTM?

A
  1. Increased birth control. 2. Increased family planning. 3. More children surviving to adulthood. 4. Less children needed to work on the farms as there is a shift to industrial work
72
Q

What happens during stage 4 of the DTM?

A

Birth rate and death rate are at a low level so the population remains high and stable.

73
Q

What happens during stage 5 of the DTM?

A

Birth rate begins to fall again and the death rate remains constant meaning the total population starts to decrease.

74
Q

Give two reasons why the birth rate begins to fall during stage 5.

A
  1. Children are expensive so parents have fewer children. 2. Some people decide to have no children at all.
75
Q

What is life expectancy?

A

The average age a new born can expect to life to.

76
Q

How can you find life expectancy?

A

Finding the age that 50% of the population from that cohort are dead.

77
Q

What are the three types of graphs that can represent human population?

A

Population growth curves, survival curves and age population pyramids.

78
Q

What do population growth curves show?

A

How the total population is changing.

79
Q

What do survival curves show?

A

The percentage of all the individuals that were born within a population that are still alive at a given age.

80
Q

What is the survival rate?

A

The percentage of people that are still alive at a given age.

81
Q

What do age population pyramids show?

A

How many males and females there are within different ages groups of a population.

82
Q

Draw the DTM.

A

A2 Biology - unit 4 (8 decks)

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