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Biology Y2 > 7.4: Populations in ecosystems (ecology) > Flashcards

7.4: Populations in ecosystems (ecology) Flashcards

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1
Q

Define population

A

all of the individuals of the same species in a habitat at the same time

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2
Q

Define community

A

all of the individuals of all species in a habitat at the same time

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3
Q

Define ecosystem

A

the relationship between the community and the abiotic environment

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4
Q

What is meant by the term ‘biotic factor’ and describe two examples

A

The living component - interactions between individuals within the community e.g. predation, competition, mutualism

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5
Q

What is meant by the term ‘abiotic factor’ and state two examples found in each of aquatic and terrestrial environments

A

non-living component
aquatic: pH and temperature of water
terrestrial: light intensity, water availability

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6
Q

Name the 2 types of competition and describe the difference between them

A

Intraspecific - between individuals of the same species
Interspecific - between individuals of different species

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7
Q

Using examples, explain the difference between primary and secondary succession

A

Primary = colonisation of bare rock e.g. on a lava flow
Secondary = recolonisation of an area e.g. following a forest fire

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8
Q

Compare and contrast the pioneer and climax communities

A

pioneer - harsh abiotic factors, few plant species (highly specialised), less stable (will change)
climax - less harsh abiotic factors, more plant species (less specialised), more stable (doesn’t change)

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9
Q

Explain why animal biodiversity is greater in a climax community

A

there are more plant species providing a greater variety of food sources and so there are more niches available and so there are more animal species

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10
Q

How can you link the Nitrogen cycle to a wet habitat

A

waterlogged soils, less O2, anaerobic conditions, decrease in nitrates, increase in nitrifying bacteria, increase in N2 gas

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11
Q

Fully describe how you could estimate the size of a population of sundews in a small marsh

A

1- Create a grid using two tape measures
2- Use a random number generator to produce coordinates
3- Place a quadrat at the coordinate and count the number of sundews it contains
4- Repeat at 10 different coordinates on the grid
5- Repeat steps 1-4 in a different area of the marsh
6- Add up the total number of sundews and divide by the number of quadrats used to calculate the mean number of sundews per quadrat
7- Multiply the mean number of sundews per quadrat by the total area of the marsh

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12
Q

Suggest two precautions needed when marking organisms when using the mark-release-recapture method to make sure the estimate of the number of organisms is valid

A

1- Mark isn’t visible to predators, so they are not more likely to be eaten
2- Mark isn’t toxic, so it doesn’t kill them

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13
Q

What is a parasitic relationship

A

Where one member gains, and the other is harmed

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14
Q

What is a mutualistic relationship

A

Where both members gain

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15
Q

What is a commensalistic relationship

A

Where one member gains, and the other neither gains nor is harmed

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16
Q

What is a niche

A

The role an organism plays in its environment

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17
Q

What is the difference between the realised niche and the fundamental niche

A

realised = no species is better than them in this area
fundamental = competition with other species

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18
Q

Define succession

A

The change in structure of a community and an ecosystem over time

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19
Q

What is the difference in time between secondary and primary succession and explain why

A

Secondary is quicker than primary as there are phosphates, nitrates, DOM, seeds, soil etc

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20
Q

How does the standard deviation suggest if the mean of something is significantly greater than the mean of something else

A

if the standard deviations of the mean masses do not overlap

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21
Q

The standard deviations of the mean masses of two samples do not overlap. What does this mean?

A

That the mean mass of one sample is significantly greater than the mean mass of the other sample

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22
Q

HYPOTHESIS TESTING
p =< 0.05 therefore…..

A

the result is significant as the result is not due to chance therefore the null hypothesis is rejected

23
Q

In terms of ecology stats tests,
if measurements are taken and you are looking for a correlation between 2 different measurements, what test would you use?

A

Spearman’s Rank test

24
Q

In terms of ecology stats tests,
if measurements are taken and you are not looking for a correlation between 2 different measurements, but are comparing means from 2 sets of data, what test would you use?

A

Student’s T-test

25
Q

In terms of ecology stats tests,
if measurements are not taken but you collected frequencies, what test would you use?

A

Chi-squared test

26
Q

What do the values for the correlation coefficient: -1,0,+1 mean in a Spearman’s Rank test

A

-1 = Perfect negative correlation between x and y
0 = no correlation between x and y
+1 = Perfect positive correlation between x and y

27
Q

p =< 0.05 in a spearman’s rank test therefore…

A

There is a significant correlation between and y as the correlation is not due to chance and so the null hypothesis can be rejected

28
Q

p =< 0.05 in a Student’s T-test therefore…

A

there is a significant difference between the means of samples x and y as the difference in means is not due to chance and so the null hypothesis can be rejected

29
Q

p =< 0.05 in a Chi Square test therefore…

A

There is a significant different between observed and expected data as the difference is not due to chance and so the null hypothesis can be rejected

30
Q

What would the null hypothesis of a Spearman’s Rank test be

A

There is no significant correlation between x and y

31
Q

What would the null hypothesis of a Students T- test be

A

There is no significant difference between the mean of sample x and sample y

32
Q

What would the null hypothesis of a Chi Square test be

A

There is no significant difference between the observed and the expected data

33
Q

What does the carrying capacity of a population mean

A

The maximum size that a population can remain sustainable in an ecosystem

34
Q

What does the biotic potential of a population mean and give an example

A

The maximum rate of reproduction in ideal conditions e.g. bacteria growing in a lab

35
Q

What does competitive exclusion mean

A

when a population is wiped out due to another population’s fundamental niche completely overlapping that population’s fundamental niche

36
Q

Is a population more or less likely to survive intra than interspecific competition and why

A

less likely because in intra, they all have the same niches and so their niches completely overlap, and so there is full competition

37
Q

What are the 2 ways of working out population density

A

% cover or % frequency

38
Q

What is the equation for mark-release-recapture and what do the letters mean

A

P = N1 x N2
———–
R
Where 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

39
Q

List the assumptions made by the mark-release-recapture method

A

There are few births/deaths in the population, there is no migration of individuals
Proportion of marked:unmarked in 2nd sample is the same proportion in the whole population
Marked individuals distribute themselves evenly amongst rest of population so that all individuals have equal chance of being captured and recaptured
Method of marking isn’t: lost, rubbed off, toxic, going to make them more conspicuous to predators

40
Q

How many quadrats should be used for reliable results

A

20 or more

41
Q

What is a transect

A

When you put down quadrats down along a transect (straight line) at regular intervals, measuring abundance

42
Q

What is the difference between a line and a belt transect

A

Belt = Measure abundance in quadrat
Line = measure abundance of everything that touches the line

43
Q

What type of sampling method would you use when measuring population distribution in a non-uniform area

A

Systematic sampling - either line or belt transects

44
Q

What type of sampling method would you use when measuring population distribution in a uniform area

A

Random - quadrats

45
Q

What type of sampling method would you use when measuring population abundance of plants

A

Quadrats

46
Q

What type of sampling method would you use when measuring population abundance of animals

A

Kick sampling or capture, mark, release, recapture

47
Q

What is the symbol for standard deviation in BIOLOGY

A

sx NOT 𝜎x

48
Q

what is the equation for calculating diversity index and what do the letters represent

A

D = N(N-1)
———-
∑n(n-1)
N = total number of organisms of all species
n = total number of organisms of a particular species

49
Q

What does biodiversity (diversity index) measure

A

The species richness - number of different species present
and the number of individuals in each species

50
Q

What is species richness

A

the number of different species present

51
Q

What is the pioneer community

A

the first species to colonise an area

52
Q

Explain the events of succession

A

Gradually exposed rocks are weathered away, releasing minerals, gradually forming soil
Pioneer species such as lichens/algae/mosses colonise speeding up breakdown of rocks
Plants with roots colonise these improved soils, their roots grow and further break up the rock
Soil begins to develop as organisms from previous stages die, DOM, increases soil nutrients. Animal communities develop providing extra DOM. Diversity increases, competition increases, and so larger plants outcompete ground plants
Animal population increases, greater seed dispersal
Shrubs grow, trees grow -> climax community

53
Q

What can affect the carrying capacity of a population

A

Food, shelter, water

Biology Y2 (7 decks)

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