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AQA A level Biology > 7.4 Populations in ecosystems > Flashcards

7.4 Populations in ecosystems Flashcards

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1
Q

What are the 2 types of environments

A
  • Harsh
  • Mild
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2
Q

What makes it a harsh environment to live in

A
  • Limited water
  • Salty/ saline
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3
Q

Why is there less life in harsh environments

A

It’s harder to adapt to the abiotic factors which determine the survival

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4
Q

What type of factors determine the survival in harsh environments

A

Abiotic

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5
Q

Is there a lot of competition in harsh environments

A

No

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6
Q

Is there a lot of competition in mild environments

A

Yes

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7
Q

Why is there a lot of life in mild environments

A

Because many species are able to adapt to the biotic factors which determine survival

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8
Q

What type of factors determine the survival in mild environments

A

Biotic

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9
Q

What are the 2 shaped graphs that show population growth

A
  • J shaped curve
  • S shaped curve
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10
Q

What is another name for the J shaped curve graph that shows population growth

A

Boom and bust

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11
Q

Generally what type of population does the J shaped curve show

A

Pest insects population around agriculture

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12
Q

What is the biotic potential on a s shaped graph that shows population growth

A

The maximum rate of reproduction in ideal conditions

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13
Q

Why cant populations naturally reach their biotic potential

A

Because of environmental resistance - not always ideal conditions

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14
Q

What does carrying capacity mean

A

Maximum population size the environment can support

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15
Q

What does environmental resistance mean

A

A factor that limits population growth - both biotic and abiotic factors

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16
Q

Define population

A

Individuals of the same species in the same area at the same time

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17
Q

Define Community

A

Populations of different species living in the same habitat at the same time

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18
Q

Define niche

A

The organisms role within ecosystem

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19
Q

What is a fundamental niche

A

The role the organism could play in the environment

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20
Q

What is a realised niche

A

The actually role the organism plays in the environment

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21
Q

What is competition between

A

Individuals

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22
Q

What is interspecific competition

A

Competition between individuals of different species

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23
Q

What is intraspecific competition

A

Competition between individuals of the same species

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24
Q

What type of competition has a greater effect, inter or intra

A

Intraspecific competition because the fundamental niches are exactly the same so one of the individuals will be restricted only to their realised niches

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25
Q

Define abundance

A

The number of individuals existing in a habitat

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26
Q

What is the mark-release-capture equation

A

P= (N1 x N2) / R

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27
Q

What do the letters P, N1, N2, and R mean in the mark-release-capture equation

A

P= estimated population size
N1= Total number of individuals in the first sample
N2= Total number of individuals in the second sample
R= Number of marked individuals recaptured

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28
Q

What are the 4 assumptions made by the mark-release-recapture method

A
  • There are few births/ deaths in the population
  • Proportion of marked: unmarked in 2nd sample is the same proportion in the whole population
  • Marked individuals distribute themselves evenly among rest of population
  • That the method of marking hasn’t been rubbed off/ toxic/ going to make them more conspicuous to predators
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29
Q

What is the minimum number of quadrats required to measure distribution

A

20

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30
Q

What are the 2 ways to position the quadrats

A
  • Random
  • Systematic
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31
Q

How do you select the coordinates for a random sample

A

By using a random number generator

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32
Q

What type of environment would you use a random sampling technique

A

A uniform

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33
Q

What are the 2 types of transects

A
  • Belt
  • Line
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34
Q

What is the difference between a belt transect and a line transect

A

A belt transect measures the abundance in each quadrat whereas a line transect measures everything that touches the line

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35
Q

What type of environment would you use systematic sampling

A

Non-uniform

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36
Q

What are the letters for standard deviation in biology

A

sx

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37
Q

Define species richness

A

A measure of the number of different species in a community

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38
Q

Define ecological succession

A

The change in environment over time

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39
Q

What is a sere

A

A complete succession of plant communities which result in the climax community

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40
Q

What is a primary succession

A

A site of newly formed habitat not previously supported community

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41
Q

What is a secondary succession

A

A site that has previously supported a community

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42
Q

Define ecosystem

A

A community and the non-living/ abiotic components of the environment

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43
Q

Define species diversity

A

The number of different species and the number of individuals of each species within any one community

44
Q

Define genetic diversity

A

The variety of genes possessed by the individuals that make up a population of a species

45
Q

Define ecosystem diversity

A

The range of different habitats from a small local habitat to the whole of the Earth

46
Q

What is meant by the term species richness

A

The number of different species in a particular area at a given time

47
Q

What type of system are ecosystems

A

Dynamic

48
Q

What are the 2 major processes within an ecosystem to consider

A
  • The flow of energy through the system
  • The cycling of elements within the system
49
Q

What is a population

A

A group of individuals of one species that occupy the same habitat at the same time and are potentially able to interbreed

50
Q

What 2 major things can cause variation in the size of a population

A
  • Effect of abiotic factors
  • Interaction between organisms
51
Q

What is a community

A

All the populations of different species living and interacting in a particular place at the same time

52
Q

What is a habitat

A

The place where an organism normally lives and its characterised by physical conditions and the other types of organisms present.

53
Q

What is a niche

A

It describes how an organism fits into the environment. it refers to where an organism lives and what it does there

54
Q

Does a niche include all the biotic or all the abiotic factors to which an organism is adapted to survive, reproduce and maintain a viable population

A

Both, both the abiotic and biotic factors are included

55
Q

What is known as the competitive exclusion principle

A

No 2 species occupy exactly the same niche

56
Q

Why don’t populations continue to grow indefinitely, give a few examples

A

Because certain factors limit growth
e.g. food availability, light, water, oxygen, shelter, accumulation of toxic waste, disease, predators

57
Q

The population size of a species that an ecosystem can support is known as

A

The carrying capacity

58
Q

How does temperature influence the size of a population

A
  • Each species has a different optimum temperature at which it is best able to survive- the further away the temperature is to the optimum = fewer individuals in a population able to survive.
    In plants and cold blooded animals, falling temperatures causes enzymes to work more slowly and a reduce in their metabolic rate. An increase in temperature causes denaturing enzymes. Both of these cases reduce the carrying capacity

In warm blooded animals, they can maintain a relatively constant body temp, however when the temp moves further away from their optimum the more energy the organisms uses to maintain their body temp. Leaving less energy for growth so slower maturity so slower reproductive rates = reduced carrying capacity

59
Q

How does a drop in temperature effect the carrying capacity in cold blooded animals and plants

A

If the temp falls below the optimum the enzymes work more slowly and so their metabolic rate is reduced resulting in the population having a smaller carrying capacity

60
Q

How does an increase in temperature effect the carrying capacity in cold blooded animals and plants

A

An increase above the optimum temp results in the enzymes working less efficiently since they gradually undergo denaturation which reduces the population’s carrying capacity

61
Q

How does temperature change effect the carrying capacity in population with warm blooded animals

A

Warm blooded animals can maintain a relatively constant body temp, however if the temp moves further away from the optimum living temp for the animal, the animal then uses a lot of energy trying to keep their body temp, which leaves less energy for individual growth and so they mature more slowly and their reproductive rate slows = reducing populations carrying capacity

62
Q

How does light effect the carrying capacity of a population

A

Increased light intensity increases rate of photosynthesis - faster growth of plants & more spores/ seeds produced = potentially greater carrying capacity. In turn the animals that feed on the plants has a potentially larger carrying capacity

63
Q

How does pH effect the carrying capacity of a population

A

It affects the action of enzymes. A population of organisms is larger where the appropriate pH exists and smaller or non-existent where the pH is different from the optimum

64
Q

How does water and humidity effect the carrying capacity of a population

A

Areas of scarce water, populations are small and consist only of species that are well adapted to living in dry conditions.
Humidity affects the transpiration rate in plants and the evaporation of water from the bodies of animals. In dry air conditions, the population of species adapted to tolerate low humidity will be larger than those without the adaptations.

65
Q

When any abiotic factor is below the optimum for a populations, what generally occurs

A

Fewer individuals are able to survive since their adaptations are not suited to the conditions, if no individuals have adaptations that allow survival, the population becomes extinct

66
Q

What is intraspecific competition

A

Competition that occurs when individuals of the same species compete with one another for resources such as food, water, breeding, sites, etc.

67
Q

If the availability of resources is great, what does that mean for the population

A

The larger the population

68
Q

What is interspecific competition

A

It occurs when individuals of different species compete for resources such as food, light, water, etc.

69
Q

What is known as the competitive exclusion principle

A

When there is the complete removal of one species, due to competition

70
Q

What does the competitive exclusion principle state

A

That where 2 species are competing for limited resources, the one that uses these resources most effectively will ultimately eliminate the other.

71
Q

What is a predator

A

An organism that feeds on another organism, known as their prey

72
Q

What is the effect of predator-prey relationship on population size

A
  • Predators eat the prey = reducing prey populations size
  • Fewer prey means more competition between the predators
  • Reduced predator population since some are unable to obtain enough prey to survive or to reproduce
  • Fewer predators means less prey eaten so more survive and are able to reproduce
  • Prey population increases
  • More prey= more food for predators so predator population increases
73
Q

Name other reasons for cyclic fluctuation in populations, other than predator-prey relationships

A
  • Disease
  • Climatic factors
74
Q

Why is it important for a population to experience crashes from predators, disease or climatic factors

A

It causes selection pressure, meaning those that can withstand these adverse conditions are more likely to survive and reproduce - so the population evolves to be better adapted to the prevailing conditions

75
Q

What are the 2 sampling techniques used in the study of habitats

A
  • random sampling using frame quadrats or point quadrats
  • systematic sampling along a belt transect
76
Q

Why is avoiding bias when sampling good

A

Avoiding bias by sampling randomly ensures that the data obtained are reliable

77
Q

What are the 3 main steps when sampling at random

A
  • Lay out 2 long tape measures at right angles, along 2 sides of the study area
  • Obtain a series of coordinates by using random numbers taken from a random number generator
  • Place quadrat at the intersection of each pair of coordinates and record the species within it
78
Q

When would a systematic sample be better than a random sample

A

Where there’s some form of gradual change in the communities of plants and animals takes place.

79
Q

What is meant by the word abundance

A

The number of individuals of a species within a given area

80
Q

What is the minimum number of quadrat that must be used in an experiment to obtain reliable data

A

20

81
Q

Describe the mark-release-recapture method

A

A known number of animals are caught, marked, and then released back into the community. Later, a given number of individuals is collected randomly and the number of marked individuals is recorded.

82
Q

What is the equation for the mark-release-recapture method

A

estimated population size = (total number of individuals in the first sample x the total number of individuals in the second sample) / number of marked individuals recaptured

83
Q

Name assumptions the mark-release-recapture method relies on

A
  • The proportion of marked to unmarked in the second sample is the same as the proportion in the population as a whole
  • The marked individuals released distribute themselves evenly amongst the rest of the population
  • No immigration into or emigration out of the population
  • There are few if any deaths or births
  • The method of marking is not toxic, nor make the individual more liable to predation
  • The mark doesn’t rub off
84
Q

What does the term succession describe

A

Describes the changes, over time, in the species that occupy a particular area

85
Q

Succession takes place in a series of stages. At each stage new species colonise the area and these may change the environment. How may these species later change the environment?

A
  • Making it less suitable for the existing species. As a result the new species may out-compete the existing one and so take over a given area
  • Making it more suitable for other species with different adaptations. As a result this species may be out-competed by the better adapted new species
86
Q

What is the name for the organisms that are involved in the first stage of succession that colonise an inhospitable environment

A

Pioneer species

87
Q

What’s the name of the community that the pioneer species create

A

Pioneer community

88
Q

Name some features of a pioneer species that suits them to colonise

A
  • Asexual reproduction, so a single organism can rapidly multiply to build up a population
  • The production of vast quantities of wind-dispersed seeds or spores so they can easily reach isolated situations
  • Rapid germination of seeds
  • The ability to photosynthesis - not dependent on animal species
  • The ability to fix nitrogen from atmosphere - soil has little to no nutrients
  • Tolerance to extreme conditions
89
Q

What is a climax community

A

When the community is in a stable state and comprises a balanced equilibrium of species with few, if any, new species replacing those that have become established - in this state many species flourish and there is much biodiversity

90
Q

During an succession there are a number of common features that emerge, what are they ?

A
  • The abiotic environment becomes less hostile
  • A greater number and variety of habitats and niches
  • Increased biodiversity
  • More complex food webs
  • Increased biomass
91
Q

What determines the dominant species in a climax community

A

Abiotic factors like climate

92
Q

Why does the secondary succession occur more rapidly

A

Because the soil already exists in which spores and seeds often remain alive in the soil, and there is an influx of animal and plants through dispersal and migration from the surrounding area

93
Q

In the secondary succession, will all of the species in the climax community be the same as the first climax community and why

A

NO, because the land has been altered in some way, e.g. by fire, so some of the species in the climax community will be different

94
Q

What is conservation

A

The management of the Earth’s natural resources by humans in such a way that maximum use of them can be made in the future.

95
Q

When human conserve, what 2 things are they maintaining

A
  • Ecosystems
  • Biodiversity
96
Q

What are the main reasons for conservation

A
  • Personal
  • Ethical
  • Economical
  • Cultural and aesthetic
97
Q

Explain the personal reason for conservation

A

To maintain our planet and therefore our life support system

98
Q

Explain the ethical reason for conservation

A

Other species have occupied the Earth far longer than we have and should be allowed to coexist with us. Respect fro living things is preferable to disregard for them

99
Q

Explain the economic reason for conservation

A

Living organisms contain a gigantic pool of genes with the capacity to make millions of substances, many of which may prove valuable in the future. Long-term productivity is greater if ecosystems are maintained in their natural balanced state.

100
Q

Explain the cultural and aesthetic reason for conservation

A

Habitats and organisms enrich our lives. Their variety adds interest to everyday life and inspires writer, poets, artists, composers, and others who entertain and fulfill us

101
Q

Name 2 methods of conservation used in moorlands to prevent a climax community

A
  • Grazing
  • Burning of heather
102
Q

Loss of nutrients into Lake Malawi has resulted in a decrease in some fish populations, explain why (4 marks)

A

-Growth/increase of algae/ surface plants/ algal bloom blocks light
- Reduced photosynthesis so plants die
- Saprobiotic organisms respire aerobically
- Less oxygen for fish to respire

103
Q

The mark-release-recapture method can be used to estimate the size of a fish population, explain how (4 marks)

A
  • Capture sample, mark and release
  • Ensure marking is not harmful
  • Allow time for fish to randomly distribute before collecting second sample
  • Population= number in first sample x number in second sample divided by the number of marked fish in second sample
104
Q

Succession occurs in natural ecosystems, Describe and explain how succession occurs (4 marks )

A
  • Colonisation by pioneer species
  • Pioneer species change environment factors
  • Environment becomes more hostile for new species
  • Increase in biodiversity
  • TO climax community
105
Q

Describe how you could estimate the size of a population of sundews in a small marsh (5 marks)

A
  • Use a grid / use tape measures
  • Method of obtaining random coordinates / random number generator
  • Count number in a quadrat
  • Use 30 quadrats and calculate mean number per quadrat
  • Mean number of plants per quadrat multiplied by number of quadrats in marsh

AQA A level Biology (35 decks)

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