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Year 2 Biology > Populations In Ecosystems > Flashcards

Populations In Ecosystems Flashcards

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1
Q

What is ecology?

A

The study of the inter-relationships between organisms and their environment (the environment includes both abiotic and biotic factors)

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2
Q

What is an abiotic factor?

A

An ecological factor that makes up part of the non-biological environment of an organism

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3
Q

What are some examples of abiotic factors

A

Temperature, PH, rainfall and humidity

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4
Q

What’s a biotic factor?

A

An ecological factor that makes up part of the living environment of an organism

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5
Q

What are some examples of biotic factors?

A

Food availability, predation and competition

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6
Q

What is an ecosystem?

A

All the living and non-living components of a particular area
(Can range in size from very small to very large)

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7
Q

What are the 2 major processes to consider within an ecosystem?

A

The flow of energy through the system and the cycling of elements within the system

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8
Q

What’s some examples of ecosystems?

A

Oak woodland or a freshwater pond or lake

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9
Q

Within each ecosystem, there are a number of species; each species is made up of a group of individuals that make up a…

A

Population

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10
Q

What is a population?

A

Group of individuals of the same species that occupy the same habitat at the same time

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11
Q

What is carrying capacity?

A

An ecosystem supports a certain size of population of a species

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12
Q

The size of a population can vary as a result of

A
  • the effect of abiotic factors
  • interactions between organisms e.g. Intraspecific (between organisms of the same species) and interspecific (between organisms of different species) competition and predation
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13
Q

In the different habitats of an oak woodland there are populations of:

A

nettles, worms, green woodpeckers, beetles etc,

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14
Q

What is a community?

A

All the populations of different species living and interacting in a particular particular place at the same time.
(Examples in woodland= oak trees, hazel, shrubs, blue tits, ladybirds,fungi, and bacteria

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15
Q

What is a habitat?

A

The place where an organism normally lives, characterised by the physical conditions (abiotic factors) and other organisms present
(Within an ecosystem there are many habitats e.g. in an oak woodland, the leaf canopy of the trees may be a habitat for blue tits, while a decaying log is the best habitat for woodlice)

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16
Q

Within each habitat there are smaller units, each with their own microclimate, these are called

A

Microhabitats e.g. crevice on the bark of an oak tree may be a microhabitat for lichen

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17
Q

An ecological niche describes how

A

An organism fits into the environment- what a species is like, where it occurs, what it eats and its interaction with other species- it includes all the abiotic and biotic conditions to which an organism is adapted to survive, reproduce and maintain a viable population

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18
Q

No two species occupy exactly the same niche=

A

Competitive exclusion principle

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19
Q

To study a habitat, it is often necessary to count the number of individuals of a species in a given space=

A

Abundance

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20
Q

Why are only small samples of habitats studied in detail?

A

It is virtually impossible to identify and count every organism- to do so would be time-consuming and would almost certainly cause damage to the habitat being studied

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21
Q

As long as samples are ______ of the habitat as a whole, any conclusion drawn from the findings will be reliable

A

Representative

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22
Q

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

A

Random sampling using frame quadrats and systematic sampling along a belt transect

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23
Q

Describe a quadrat and briefly how it is used

A

Square frame divided by string or wire into equally sized subdivisions. The quadrat is placed in different locations within the area being studied using random sampling. The abundance of each species within the quadrat is then recorded

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24
Q

What are 3 factors to consider when using a quadrat?

A

1- size of quadrat to use
2- the number of sample quadrats to record within the study area
3- the position of each quadrat within the study area

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25
Q

Why do you need to consider the size of the quadrat to use?

A
  • depends upon the size of the plants or animals being counted and how they are distributed within the area e.g. larger animals require larger quadrats
  • where a population of species is not evenly distributed throughout the area, a large number of small quadrats will give more representative results as opposed to using a small number of larger quadrats
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26
Q

Why do you need to consider the number of sample quadrats to record within the study area?

A

The larger the number of sample quadrats the more reliable the results will be for a valid conclusion, however the recording of species within a quadrat is a time-consuming task, and so a balance needs to be struck between the reliability of the results and the time available

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27
Q

If a large number of different species in the area are being studied, what size sample would you take?

A

A large number would be required to produce reliable results for a valid conclusion

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28
Q

Why do you need to consider the position of each quadrat within the study area?

A

In order to produce statistically significant results, random sampling must be used

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29
Q

How do you perform random sampling?

A

1- lay out 2 tape measures at right angles, along two sides of the study area (creating a grid)
2- obtain a series of coordinates by using random numbers taken from a table or computer generated
3- place a quadrat at the intersection of each pair of coordinates and record the species within

30
Q

Why is it sometimes more informative to measure the abundance and distribution of a species in a systematic rather than random manner?

A

Where some form of gradual change (transition) in the communities of plants and animals takes place

31
Q

Give an example of when you would measure the abundance and distribution of a species in a systematic rather than random manner?

A

The distribution of organisms along a line of succession, such as, through sand dunes by the edge of the sea and inland into woodland

32
Q

How are transects used?

A

A belt transect can be made by stretching a string or tape across the ground in a straight line. A frame quadrat is laid down alongside the line and the species within it recorded. It is then moved a certain distance down the tape and the process is repeated. This gives a record of species in a continuous belt

33
Q

Random sampling with quadrats and counting along transects are used to obtain measures of abundance. What is abundance?

A

Number of individuals of a species within a given area

34
Q

For species that don’t move around, abundance can be measured in several ways depending on the size of the species being countered and the habitat. Examples include:

A
  • frequency= likelihood of a particular species occurring in a quadrat e.g. if a species occurs in 15/30 quadrats, the frequency of occurrence is 50%
  • percentage cover= an estimate of the area within a quadrat, that a particular plant species
35
Q

Give an example of when you would measure the abundance and distribution of a species in a systematic rather than random manner?

A

The distribution of organisms along a line of succession, such as, through sand dunes by the edge of the sea and inland into woodland

36
Q

How are transects used?

A

A belt transect can be made by stretching a string or tape across the ground in a straight line. A frame quadrat is laid down alongside the line and the species within it recorded. It is then moved a certain distance down the tape and the process is repeated. This gives a record of species in a continuous belt

37
Q

Random sampling with quadrats and counting along transects are used to obtain measures of abundance. What is abundance?

A

Number of individuals of a species within a given area

38
Q

For species that don’t move around, abundance can be measured in several ways depending on the size of the species being countered and the habitat. Examples include:

A
  • frequency= likelihood of a particular species occurring in a quadrat e.g. if a species occurs in 15/30 quadrats, the frequency of occurrence is 50%
  • percentage cover= an estimate of the area within a quadrat, that a particular plant species
39
Q

What are the pros and cons of frequency?

A

✅this method is useful where a species such as grass, is hard to count- it gives a quick idea of the species present and their general distribution within an area
❌ however it does not provide information on the density and the detailed distribution of a species

40
Q

What are the pros and cons of percentage cover?

A

✅ useful when a species is particularly abundant or is or is difficult to count
✅ data can be collected rapidly and individual plants do not need to be counted
❌ less useful where organisms occur in several overlapping layers (more probably plants)

41
Q

Why can’t the methods of measuring abundance be used on motile organisms?

A

The method of measuring abundance works well with plant species and non-motile or very slow moving animal species that remain in one place, however motile animals move away when approached- they are often hidden and are therefore difficult to find and identify

42
Q

Briefly describe mark-release-recapture technique

A

A known number of animals are caught and marked in some way, and then released back into the community. Some time later, a given number of individuals is collected randomly and the number of marked individuals is recorded.

43
Q

What is the equation used to calculate estimate population size?

A

Total number of individuals in first sample X total number of individuals in second sample divided by the number of marked individuals recaptured
(Lincoln index)

44
Q

Mark-release-recapture relies on a number of assumptions. What are these?

A
  • the proportion of marked to unmarked individuals in the second sample is the same as the proportion of marked to unmarked individuals in the population as a whole
  • the marked individuals released from the first sample distribute themselves evenly amongst the remainder of the population and have sufficient time to do so
  • population has a definite boundary, so there is no immigration or emigration out of the population
  • there are few, if any, deaths within the population
  • the method of marking does not make the individual more conspicuous and therefore more liable to predation
  • the mark or label is not lost or rubbed off during the investigation
45
Q

When using the mark-release-recapture technique, explain how the marks put on the individuals captured in the first sample make them more easily seen by predators and so proportionally more are eaten than unmarked individuals might affect the final estimate of the population?

A

Population over-estimated as there will be proportionally fewer marked individuals in the second sample

46
Q

When using the mark-release-recapture technique,explain how between the release of marked individuals and the collection of a second sample, an increased birth rate leads to a very large increase in the population might affect the final estimate of population

A

Population over-estimated as there will be proportionally fewer marked individuals in the second sample, because all the ‘new’ individuals will be unmarked

47
Q

When using the mark-release-recapture technique, explain how between the release of marked individuals and the collection of a second sample, disease kills large numbers of all types of individuals might affect the final estimate of a population

A

No difference because the proportion of marked and unmarked individuals killed should be the same

48
Q

What is succession?

A

How an ecosystem changes with time

49
Q

During succession, biotic conditions change as

A

Abiotic conditions change

50
Q

Succession takes place in a series of stages. At each stage, new species colonise the area and these may change the environment. These species may alter the environment in a way that makes it:

A
  • less suitable for existing species; as a result, the new species may out-compete the existing one and so take over a given area
  • more suitable for other species with different adaptions; as a result, this species may be out-competed by the better adapted new species

In this way, there is a series of successional changes which alter the abiotic environment; these alterations can result in a less hostile environment that makes it easier for other species to survive. As a result, new communities are formed and biodiversity is changed/increased

51
Q

The first stage of this type of succession is the colonisation of an inhospitable environment by organisms called

A

Pioneer species

52
Q

Pioneer species make up a pioneer community and often have features that suit them to colonisation. These may include:

A
  • asexual reproduction so that a single organism can rapidly multiply to build up population
  • the production of vast quantities of wind-dispersed seeds of spores, so they can easily reach isolated situations, such as volcanic islands
  • the ability to photosynthesise, as light is normally available, but other food is not- they are therefore not dependent on animal species
  • ability to fix nitrogen from the atmosphere because, even if there is soil, it has few or no ingredients
  • tolerance to extreme conditions and rapid changes in conditions
  • short life cycle
53
Q

Explain why lichen (primary coloniser) is referred to as a pioneer species and the stages that follow

A
  • one of the few kinds of organisms capable of surviving on inhospitable areas e.g. bare rock
  • can survive considerable drying out (tolerance to extreme conditions)
  • in time, weathering of the base rock by the actions of the lichens produces sand or soil, although this in itself cannot support other plants
  • however, as lichens die and decompose they release sufficient nutrients to support a community of small plants
  • in this way, the lichens change the abiotic environment by creating soil and nutrients for the organisms that follow
  • mosses are typically the next stage in succession (secondary colonisers) followed by ferns
  • with the continuing erosion of the rock and the increasing amount of organic matter available from the death of these plants, a thicker layer of soil is built up
  • the organic material holds water making it easier for other plants to grow; again, these species change the abiotic environment, making it less hostile and so more suitable for the organisms that follow, e.g. small flowering plants such as grasses (tertiary colonisers) and in turn, shrubs and trees to woodland (climax)
54
Q

What do the pioneer species do to the abiotic conditions?

A

Changes them to make it less hostile so other species can being to colonise

55
Q

Does the pioneer species survive?

A

No, it will die and be decomposed and add to the soil

56
Q

What is a climax community?

A

A stable community- no further succession

57
Q

Animals have undergone a similar series of successional changes which have been largely determined by the plant types available for foods and habitats. Give an example:

A
  • the dead lichens provide food for animals such as mites
  • the growth of mosses and grasses provide food and habitats for insects, millipedes and worms
  • these are followed in turn by secondary consumers such as centipedes which feed on these organisms
  • the development of flowering plants, including trees, helps to support communities of butterflies and moths as well as large organisms, such as reptiles, mammals and birds
58
Q

During any succession there are a number of common features that emerge:

A
  • the non-living (abiotic) environment becomes less hostile
  • greater number of and variety of habitats and niches
  • increased biodiversity
  • increased variety of food sources
  • more complex food webs
  • increased biomass
59
Q

Features of a climax community:

A
  • same species present (over long time)/ stable community over time
  • abiotic factors (more or less) constant over time
  • population stable, around carrying capacity
60
Q

Primary succession happens on bare rock, whereas secondary succession occurs

A

On land that has been cleared/felled areas (bare soil)

61
Q

What are some differences between primary and secondary succession?

A

Primary:

  • bare land
  • no soil
  • takes longer to reach climax community

Secondary:

  • felled areas
  • soil present
  • climax community reached more quickly
62
Q

In general, what happens to biodiversity as succession continues

A

Increases

63
Q

What sort of activities prevent succession?

A

Mowing, animal grazing and managed fires

64
Q

Ethical issues or mark, release and recapture

A
  • marking method could be toxic
  • Mark makes the animal more conspicuous to predators
  • capture and marking method is harmful or overall stressful to the animal
65
Q

Where can you see an example of succession in one time frame?

A

Beaches

66
Q

What is intraspecific competition?

A

Individuals of the same species compete with one another for resources such as food, water, breeding sites etc- it is the availability of such resources that determines population size

67
Q

What is interspecific variation?

A

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

68
Q

When populations of two different species are in competition one will normally have a

A

Competitive advantage over the other = population of this species will increase in size whilst the other will diminish

69
Q

What is the competitive exclusion principle?

A

Where two species are competing for limited resources, the one that uses these resources most effectively will ultimately eliminate the other I.e. no two species can occupy the same niche indefinitely when resources are limited

70
Q

To show how a factor influences the size of a population it is necessary to link it to the birth rate and death rate of individuals in a population- give an example of why this is necessary

A

An increase in food supply does not necessarily mean there will be more individuals could just mean bigger ones. Therefore, important to show how a factor such as change in food supply affects the number of individuals in a population e.g. increase in food supply means that more individuals are likely to survive and so there is an increased probability that they will produce offspring and so population will increase

Year 2 Biology (4 decks)

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