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A2 Biology > T10.1 - The Nature of Ecosystems > Flashcards

T10.1 - The Nature of Ecosystems Flashcards

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1
Q

Define population

A

A group of organisms of the same species, living in the same area at the same time.

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2
Q

Define community

A

A group of populations living together and interacting with each other within a given area.

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3
Q

Define habitat

A

The environment in which a species normally lives, or the location of a living organism.

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4
Q

Define habitat biodiversity

A

A measure of the number of different habitats found within an area.

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5
Q

State what is meant by the term ecosystem

A

All the living organisms and all the nonliving components in a specific habitat, and the interactions between them.

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6
Q

State what is meant by the term niche

A

The functional position and role of an organism within its environment.

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7
Q

State what is meant by the term fundamental niche

A

The entire set of conditions under which an organism can survive and reproduce (i.e. where it can live).

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8
Q

State what is meant by the term realised niche

A

The set of conditions used by a given organism after interactions with other species are taken into account (i.e. where it does live).

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9
Q

What term is given to all or the areas of the surface of the earth where living organisms survive.

A

Biosphere

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10
Q

What is a biome?

A

A major ecosystem, distinguished by its climate and plant species which live there.

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11
Q

What are biotic factors?

A

The living factors in a habitat when an organism lives

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12
Q

What are abiotic factors?

A

The non living factors in a habitat where the organism lives

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13
Q

What is competitive exclusion

A

When one species uses resources more efficiently and drives the other species to local extinction.

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14
Q

What is resource partitioning?

A

When two or more species alter their use of the niche to avoid direct competition, allowing for co-existence.

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15
Q

What do food chains show?

A

Linear feeding relationship between species in a community

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16
Q

What do arrows represent in a food chain

A

Transfer of energy and matter as one organism is eaten another, pointing in direction of energy flow

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17
Q

What is meant by trophic level?

A

The feeding position that an organism holds in a food chain, web, pyramid of numbers or biomass

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18
Q

List the trophic levels from first to fourth

A
  1. Producers
  2. Primary consumers
  3. Secondary consumers
  4. Tertiary consumers
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19
Q

What are autotrophs?

A

Organisms that produce their own food by converting carbon dioxide (from atmosphere or dissolved in water) into organic compounds

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20
Q

What is the difference between photoautotrophs and chemoautotrophs?

A

Photoautotrophes use light energy
Chemoautotrophes use energy released from the oxidation of inorganic compounds

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21
Q

Give example of photoautotroph

A

Plants or algea

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22
Q

Give an example of a type of chemoautotroph

A

Nitrosomonas / Nitrobacter / Methanogens / Iron bacteria

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23
Q

How do chemoautotrophs make organic compounds?

A

Chemosynthesis - oxidise inorganic energy sources to synthesize organic compounds from carbon dioxide.

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24
Q

Name three examples of heterotrophs

A

Consumers, detritivores, saprotrophs

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25
Q

Define hetertroph

A

An organism that eats other plants or animals for energy and nutrients.

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26
Q

What is a pyramid of numbers?

A

Graphical representation of the number of organisms at each trophic level of a food chain.

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27
Q

Give an advantage and disadvantages of pyramids of number

A

It is easiest to mease (counting), but can be distorted by large organisms.

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28
Q

What is a pyramid of biomass?

A

Graphical representation of the combined biomass of all the organisms at each trophic level of a food chain.

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29
Q

Why is dry biomass more accurate that wet biomass?

A

Water content in organisms is variable

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30
Q

Explain the shape of a pyramid of biomass

A

Always upright in shape, as biomass diminishes along food chains as carbon dioxide and water (urea) is released

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31
Q

Explain why pyramids of biomass for marine ecosystems are not upright

A

Phytoplankton replace their biomass at such a rapid rate they can support a larger biomass of zooplankton

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32
Q

State an advantage of a pyramid of biomass

A

More accurate representation than pyramid of numbers as not inverted by large organisms.

33
Q

What are the disadvantages of a pyramid of biomass?

A

Calculating dry biomass requires destruction of the material.
To avoid destroying whole habitats, small samples are taken and results scaled up - so only estimate.
Does not take into account rate of biomass production.

34
Q

What is a pyramid of energy?

A

Graphical representation of the total energy content of all organisms at each trophic level of a food chain.

35
Q

What are the advantages of a pyramid of energy?

A

It will never appear inverted as some of the energy stored in one source is always lost upon transfer
It takes into account the rate the producers are reproducing over a period of time.

36
Q

What is a disadvantage of a pyramid of energy?

A

Extremely difficult to measure accurately

37
Q

Explain where decomposers go on a pyramid

A

Decomposers occupy every trophic level after the first, so appear to the side, separate to the rest

38
Q

How is the abundance (population size) of a species in a habitat measured?

A

Random sampling using quadrats

39
Q

When assessing abundance of an organism, why must the sample sites be selected at random?

A

To prevent bias and get a representative sample

40
Q

How can you select random sample positions?

A

Use random number tables/generators to plot coordinates within the habitat.
Select coordinates from a map and use GPS.

41
Q

How can abundance be quantified?

A

Quantitative - Percentage cover, frequencies
Qualitative - ACFOR scale

42
Q

What does ACFOR stand for?

A

Abundant
Common
Frequent
Occasional
Rare

43
Q

Describe how a point quadrat is used to estimate percentage cover

A

Metal pins are dropped through each hole in turn and ‘hits’ are recorded.
Percentage cover = (No. of hits / total no. of hits) x 100

44
Q

What will the number of samples taken depend on?

A

The size of the habitat
The time of year
The diversity of the habitat being studied

45
Q

Suggest ways to get a more accurate estimate of population size (abundance)

A

The larger the sample size the more accurate the estimate
So use larger quadrats/use more quadrat positions

46
Q

Outline how to estimate population size in a given area.

A

Place frame quadrat at minimum of 10 random positions.
Count number of organisms in each quadrat and calculate mean.
Calculate population size (no.): mean x (total area of habitat / area of quadrat)

47
Q

Outline how to estimate the density of organisms in a given area.

A

Place frame quadrat at minimum of 10 random positions.
Count number of organisms in each quadrat and calculate total.
Calculate density (no. per metre squared):
total / (no. of quadrats x area of each quadrat)

48
Q

Outline how to estimate the relative abundance of a plant species in a given area.

A

Place frame quadrat at minimum of 10 random positions.
Count number of each plant in each quadrat and calculate total.
Calculate relative abundance (%):
(No. of plant X in all quadrats / Total no. of all plants) x 100

49
Q

Outline how to estimate the of a plant species in a given area.

A

Place frame quadrat with 10x10 grid at minimum of 10 random positions.
Count how many whole squares are covered by each species of plant.
1 square = 1%.

50
Q

How is the distribution of organisms measured in a habitat?

A

Systematic sampling using a line/belt transect

51
Q

What is a transect?

A

Line across a habitat used to measure the change in distribution and abundance of organisms in an area.

52
Q

What is zonation

A

The changing distribution pattern of a species in response to a change in an abiotic factor or competition.

53
Q

What can transect data be used for?

A

data can used to identify optimum conditions as a well as zones of stress and zones

54
Q

What is a line transect used for?

A

For large/rare animals e.g snakes

55
Q

What are belt transcects?

A

Qudrats are placed along a transect line and numbers of organisms in each qudrat are counted.
Continous belt transects place quadrat continuously along the transect line with no gaps.
Interrupted belt transects place quadrats at regular intervals along the transect line.

56
Q

What is kite diagram

A

Graph that shows the number of animals (or percentage cover for plants) against distance along a transect.

57
Q

Suggest some abiotic factors that could affect the abundance and distribution of organisms in a habitat

A

Light intensity, pH, salinity, temperature, Wind speed, humidity, water availability

58
Q

Suggest some biotic factors that could affect the abundance and distribution of organisms in a habitat

A

Competition, predation, herbivory, human activities etc.

59
Q

What piece of apparatus is used to sample plants and slow moving (sesile) animals?

A

Quadrats

60
Q

What method is used to sample fast moving (motile) animals?

A

Mark Release Recapture

61
Q

Outline the mark-release-recapture method

A

Capture sample of animals.
Record the number captured - S
Mark each individual, ensuring it doesn’t cause harm, and release them.
Capture a second sample after a set period of time e.g. 48 hours, using the same capture technique.
Record number captured in second time = S .
Record the number of recaptured (marked) animals - R.
Calculate population size using the Lincoln Index: N = (S x S ) / R

62
Q

What method would you use to compare abundance of organisms in two different areas?

A

Random sampling using quadrats in both areas.

63
Q

What would you use Student’s t-test for?

A

To determine if there is a significant difference between two means for one characteristic between two sub-groups (e.g. comparing mean fruit weight for two crops grown in different fields)

64
Q

When can you use student t-test for?

A

When the sample size is less than 30 and the data is normally distrubuted

65
Q

What is the null hypothesis when using the t-test?

A

There is no significant difference between sample A and sample B, any difference is due to chance or sampling error.

66
Q

How do you calculate the degrees of freedom when using the t-test?

A

total number of data values minus 2

67
Q

What siginificance level is used in statistical tests?

A

p=0.05

68
Q

What is the name of the value that you compare the t value with?

A

Critical value

69
Q

If the value is less than the critical value, what do you conclude?

A

There is greater than 5% propbaility that the difference between the two means is due to chance or sampling error.
Therefore ACCEPT the null hypothesis; there is no significant difference between the mean of sampel A and sample B.

70
Q

If the t value is greater than the critical value, what do you conclude?

A

There is less than 5% propbaility that the difference between the two means is due to chance or sampling error.
Therefore REJECT the null hypothesis; there is a significant difference between the means of sample A and sample B.

71
Q

What would you use Spearman’s rank correlation coefficient (r ) for?

A

To determine if there is a correlation between two variables.

72
Q

What is the null hypothesis for Spearman’s rank correlation coefficient?

A

There is no statistically significant correlation between (variable 1) and (variable 2), any correlation is due to chance.

73
Q

How do you calculate the degrees of freedom for Spearman’s rank?

A

n (number of pairs of data)

74
Q

If r = -1, what does this indicate?

A

There is a perfect negative correlation between the two variables (as x increases, y increases)

75
Q

If r = +1, what does this indicate?

A

There is a perfect positive correlation between the two variables (as x increases, y decreases).

76
Q

If r = 0, what does this indicate?

A

There is no correlation between the two variables.

77
Q

When you are thinking about correlation, just remember this rule

A

The closer the correlation is to 0, the weaker it is, while the closer it is to +/-1, the stronger it is.

78
Q

If the is less than the critical value, what do you conclude?

A

There is greater than 5% probability that the correlation is due to chance.
Therefore ACCEPT the null hypothesis; there is no statistically significant correlation between variable 1 and variable 2.

79
Q

If the is greater than the critical value, what do you conclude?

A

There is less than 5% probability that the correlation is due to chance.
Therefore REJECT the null hypothesis; there is a statistically significant correlation between variable 1 and variable 2.

A2 Biology (9 decks)

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