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Biology > 19. POPULATIONS IN ECOSYSTEMS > Flashcards

19. POPULATIONS IN ECOSYSTEMS Flashcards

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1
Q

Define what a population is

A

A group of organisms of the same species occupying a particular space at a particular time that can potentially interbreed

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2
Q

Define a habitat

A

A place where a community of organisms live

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3
Q

Define an ecosystem

A

A biological community of interacting organisms and their physical environment

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4
Q

Define a community

A

All the populations of different species living in a habitat

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5
Q

Name the three stages of a population growth curve

A

Lag phase, exponential phase, carrying capacity

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6
Q

Compare the birth rate and the death rate in lag phase

A

Birth rate > death rate

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7
Q

Explain why population growth is slow in the lag phase, even though resources are plentiful

A

Because the number of individuals is low

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8
Q

Compare the birth rate and the death rate in the exponential phase

A

Birth rate > death rate

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9
Q

Explain why population growth is fast in the exponential phase

A

Resources are plentiful and there are no limiting factors

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10
Q

Define carrying capacity

A

The maximum population size that an environment can support

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11
Q

Compare birth and death rates in carrying capacity

A

Birth rate = death rate

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12
Q

Explain why the population size is stable in carrying capacity

A

Because resources are limiting

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13
Q

Recall the 7 limiting factors of population growth rate and carrying capacity

A

Food, space, water, mates, parasites/pathogens/disease, light intensity/availability, nesting sites

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14
Q

Which extra phase do bacterial populations experience at the end of the their population growth curves?

A

Death phase

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15
Q

Why do bacterial populations experience a death phase after their carrying capacity?

A

As O2 is used up they respire anaerobically, producing ethanol. This becomes toxic and kills the bacteria.

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16
Q

Within a habitat, different species occupy different niches. What are niches governed by?

A

Adaptations to biotic and abiotic factors, e.g. food sources

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17
Q

What is the benefit of species occupying different ecological niches?

A

There is less competition for resources

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18
Q

What type of competition exists between individuals of the same species?

A

Intraspecific

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19
Q

What type of competition exists between individuals of different species?

A

Interspecific

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20
Q

What is the competition exclusion principle?

A

When two species are competing for limiting resources, the one that uses the resources more effectively will ultimately eliminate the other

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21
Q

How will increasing competition affect population size / population growth rate / carrying capacity?

A

Increasing competition will decrease population size / population growth rate / carrying capacity

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22
Q

How will decreasing competition affect population size / population growth rate / carrying capacity?

A

Decreasing competition will increase population size / population growth rate / carrying capacity

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23
Q

Why do population size fluctuate seasonally?

A

Because resource availability fluctuates seasonally, therefore so does competition, and so does population size

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24
Q

Which type of species show seasonal fluctuations in population size?

A

Prey, herbivores, primary consumers

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25
Q

Why do predator population sizes show regular, cyclic population sizes?

A

Because the predator population size will fluctuate after the prey population size. As the pre population decreases, intraspecific competition increases and the predator population decreases

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26
Q

Out of the predator and prey, which population fluctuates first, and which fluctuates after?

A

The prey population fluctuates first (because it fluctuates with the seasons), and the predator population fluctuates after (because it is dependent on the prey population)

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27
Q

Define succession

A

Succession is a change in a community over time due to changing abiotic factors

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28
Q

What is a pioneer species?

A

The first species to colonise a habitat (after a disturbance)

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29
Q

How do pioneer species make the habitat more suitable / less hostile for other species?

A

They change the abiotic factors

30
Q

Give two examples of how pioneer species may change the abiotic factors within a habitat to make them more suitable for other species

A

They may contain nitrogen fixing bacteria, which will increase the nitrogen-containing compounds in the soil. They may be decomposed by saprobiotic bacteria, increasing the nutrient content of the soil.

31
Q

What happens to the population of the pioneer species as the population of the second species increases?

A

It decreases

32
Q

Why does the pioneer species eventually disappear?

A

Because the second species is better adapted, and so outcompetes the pioneer species

33
Q

What happens to the biodiversity of an ecosystem as succession proceeds?

A

It increases

34
Q

What is a climax community?

A

The final stable community in succession

35
Q

Give three features of a climax community

A
  1. it is stable
  2. the abiotic factors are constant
  3. the populations are stable (at carrying capacity)
36
Q

Name some factors that may affect the size of the community in a climax community

A

Nutrient availability, any factor that affects the rate of photosynthesis, disease, predators, space for nests, and competition

37
Q

Name some natural resources that humans use for their own benefit

A

Timber, crude oil, salt, metal ores

38
Q

Because the human population is so large, we are using our natural resources unsustainably. What does unsustainable mean?

A

We are using resources at a faster rate than they can replenish naturally

39
Q

What two things do we need to manage the conflict between to maintain sustainability?

A

Human need and conservation

40
Q

Define conservation

A

Conservation is the maintenance of biodiversity by restoring ecosystems

41
Q

Conservation is an active process. What does this mean?

A

It requires human participation and intervention

42
Q

Name four reasons for conservation

A

Maintaining / increasing biodiversity, protecting endangered species, conserving sources of medicine, reducing erosion and eutrophication

43
Q

What is the main loss to humans in the process of conservation?

A

Financial, e.g. cost of outlay or loss of income

44
Q

Name the process of sustainable timber production

A

Coppicing

45
Q

Why is coppicing sustainable?

A

Trees are kept alive whilst wood is harvested from them

46
Q

Describe rotational coppicing

A

Sections of forest are coppiced one at a time, leaving other sections to regrow so they are ready to be harvested again later

47
Q

Why does managing / halting succession increase global biodiversity?

A

By managing / halting succession, you will maintain different habitats and different food sources, increasing biodiversity

48
Q

When would you use a quadrat to sample species?

A

When estimating the number of species in an area

49
Q

Which type of sampling is quadrats?

A

Random sampling

50
Q

To be representative, why must sample sizes be large?

A

To minimise the effect of anomalies

51
Q

To be representative, why must samples be chosen at random?

A

To avoid bias

52
Q

What two ways can an area to be quadratted by mapped?

A

Using coordinates and using numbered areas

53
Q

If an area to be quadratted is mapped using coordinates, how would you choose your random sample?

A

Using a random coordinate generator

54
Q

If an area to be quadratted is mapped using numbers, how would you choose your random sample?

A

Using a random number generator

55
Q

Describe how you would calculate the total estimated population in an area using quadrats

A
  1. Count the individuals in each quadrat
  2. Find the sum of the individuals in each quadrat and divide by the numner of quadrats (giving the average individuals per quadrat)
  3. Multiply by the total area
56
Q

When would you use a belt transect to sample a species?

A

When calculating achange in apopulation/community over adistance in response to achanging environmentalfactor.

57
Q

Which type of sampling are belt transects?

A

Systematic sampling

58
Q

Describe a disadvantage of using belt transects

A

They may not go through all representative areas

59
Q

What piece of equipment could be used to lay a belt transect?

A

Tape measure

60
Q

How do the quadrats have to be laid along the belt transect?

A

At regular intervals

61
Q

As well as counting the individuals in each quadrat along the transect, what else must you do?

A

Measure the abiotic factor using appropriate equipment

62
Q

Which statistical test would you apply to your data from a belt transect, and why?

A

Spearman’s Rank, to calculate the correlation coefficient, which will calculate the strength of the correlation between two variables

63
Q

What is a kite diagram?

A

A diagram used to represent the abundance of species along a transect

64
Q

When would you calculate percentage cover when sampling?

A

When there are too many individuals to count, e.g. grass

65
Q

Why is using sampling to estimate the number of animals in an ecosystem problematic?

A

They are motile. So you could count the same organism twice and some not at all.

66
Q

Name the technique used to estimate animal populations in ecosystems

A

Mark, release, recapture

67
Q

What do we have to ensure about the method we use to mark individuals?

A

It doesn’t come off
It doesn’t harm the individuals
It doesn’t increase their chance of being predated
It doesn’t change their behaviour

68
Q

Why do we leave a period of time between releasing the marked individuals, and recapturing the second sample?

A

To allow them to randomly disperse back into the population

69
Q

Recall the equation used to calculate the estimated population of animals using the mark, release recapture method

A

Estimated total population = number of organisms initially caught x number of organisms in second sample / number of marked organisms recaptured

70
Q

Apart from an appropriate marking method and leaving sufficient time to disperse, what other conditions are must be assumed for mark, release recapture to be valid?

A

No migration
The same sampling method is used each time
No breeding / births or death
The sample size is large enough

Biology (26 decks)

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