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A Level - Biology > 19: Ecosystems > Flashcards

19: Ecosystems Flashcards

1
Q

Define ecology

A

The study of inter-relationships between organisms and their environment

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2
Q

Define abiotic and biotic factors

A 
Abiotic = non-living factors
Biotic = living factors
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3
Q

Give some examples of abiotic factors

A

Temperature

Rainfall

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4
Q

Give some examples of biotic factors

A

Competition

Predation

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5
Q

Define a community

A

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

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6
Q

Define an ecosystem

A

Dynamic systems made up of a community and all the abiotic factors

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7
Q

What are the two processes in an ecosystem which should be considered?

A

Flow of energy

Cycling of elements

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8
Q

Define population

A

Group of individuals of one species, in the same habitat at the same time that could interbreed

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9
Q

Define carrying capacity

A

Size of a population that an ecosystem can support

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10
Q

How does the size of a population vary?

A

Effect of abiotic factors

Interactions between organisms (biotic)

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11
Q

Define a habitat

A

Place where an organism lives and is characterised by the physical conditions and other organisms present

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12
Q

Define a microhabitat

A

Smaller units within habitats called microhabitats with their own microclimate

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13
Q

Define an ecological niche

A

Where an organism lives and what it does there

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14
Q

What is the competitive exclusion principle?

A

No two species occupy exactly the same niche

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15
Q

Define population size

A

Number of individuals in a population

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16
Q

What should be done to the population size if it increases at a ever-increasing rate? e.g bacteria growth is exponential

A

Plot the log number of bacteria

This shows all data points

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17
Q

How is temperature a limiting factor for plants cold-blooded animals? (e.g reptiles)

A

Too cold: Reactions slow down (enzymes slow down) and metabolic rate is reduced
Carrying capacity of a population decreases
Too hot: enzymes will denature
Carry capacity decreases

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18
Q

How is temperature a limiting factor for warm-blooded animals?

A

Any change: although animals maintain body temp
Significant change causes a large amount of energy spent to maintain it
Less energy for growth and maturation, reproductive rate decreases
Carrying capacity of the population is reduced

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19
Q

How is light a limiting factor?

A

Ultimate source of energy in ecosystems
More light, more photosynthesis, plants grow faster
Carrying capacity increases
Carrying capacity of consumers etc. could increase

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20
Q

How is pH a limiting factor?

A

Affects action of enzymes (denaturation)

Population of organisms in optimum pH is larger than that where pH is not optimum

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21
Q

How is water a limiting factor?

A

Populations are small where there is a lack of water unless well adapted
Water is essential

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22
Q

How is humidity a limiting factor?

A

Effects transpiration rates

Dry air causes a large amount, meaning non-adapted organisms will die quickly

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23
Q

Define intraspecific competition

A

Competition between members of the same species

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24
Q

Define interspecific competition

A

Competition between members of different species

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25
Q

Give some examples of things organisms compete for

A

Water
Food
Breeding sites/partners

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26
Q

How does availability of resources effect population size in intraspecific competition?

A

Increase in availability causes increase in population

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27
Q

How does availability of resources effect population size in interspecific competition?

A

One population will normally have an advantage

That population will increase gradually and the other decreases

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28
Q

Can two species occupy the same niche if there are limiting resources?

A

No, cannot happen as one will have an advantage

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29
Q

What does an increase in food supply cause?

A

More individuals are likely to survive
Increased probability of reproduction and population will increase
Takes a long time to take effect

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30
Q

Define predator

A

An organism that feeds on another organism (prey)

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31
Q

Define prey

A

An organism that is eaten by another (predator)

32
Q

How are predators adapted?

A

Better adapted for capturing prey

E.g - faster, better camo

33
Q

How have prey become better at avoiding predators?

A

Better camo
Protective features (spines)
Concealment behaviour

34
Q

Define predation

A

When one organism is consumed by the other

35
Q

What occurs when a predator and prey are introduced in a lab?

A

Predator exterminates prey

36
Q

What are the limitations of predator-prey interactions in labs?

A

The situation is completely different from real world
More area that a prey can be found
More diverse environment, places to hide

37
Q

What happens to prey numbers when they get low?

A

Rarely goes extinct due to increased difficulty in finding and catching prey

38
Q

What is the relationship of population size in predator and prey?

A

Predators eat prey, reduces population of prey
Greater competition in predators due to less prey
Predator population decreases due to lack of prey
Fewer predators mean more prey survive and reproduce
Prey population increases
Repeats

39
Q

Define selection pressure

A

Individuals that survive (disease, predation, etc.) are more likely to survive and reproduce
Causes evolution with advantageous traits

40
Q

What is the abundance?

A

Number of individuals of a species in a given space

41
Q

Why is it unreasonable to count every organism in a population?

A

Time-consuming

Causes damage to the environment

42
Q

When can a conclusion be drawn about a habitat or population?

A

If the samples are representative of the habitat as a whole

43
Q

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

A

Random sampling using frame or point quadrats

Systematic sampling along a belt transect

44
Q

What is a point quadrat?

A

Horizontal bar on two legs, ten evenly spaced holes on the bar
Long pin dropped through each hole
Any species the pin touches is recorded

45
Q

What is a frame quadrat?

A

Square frame divided by string/wire into equally sized subdivisions
Placed in different locations in study area
Abundance of each species within the quadrat recorded

46
Q

What should you consider when using quadrats?

A

Size of the quadrat
Number of samples to take in the study area
Position of each quadrat in the study area

47
Q

Why should you consider the size of the quadrat?

A

Depends of size of plants/animals being counted
Larger species require larger quadrat
Uneven distribution requires a large number of small quadrats (more representative)

48
Q

Why should you consider the number of quadrat samples you take in an area?

A

More samples, more representative
Balance between time-consuming and representative
Greater number of species in the area, greater number of quadrats required

49
Q

Why should you consider the position of each quadrat in the study area?

A

For statistically significant results random sampling must be used

50
Q

Why is random sampling used?

A

Avoids bias in collecting data

Ensures reliable data

51
Q

What is the method for sampling at random?

A

Lay out two tape measures at right angles along two sides of the study area
Generate a series of random coordinates using a computer
Place quadrat at intersection at each pair of coordinates and record species within it

52
Q

When should systematic sampling along belt transects be used?

A

When there is a gradual change in the communities of plants and animals

53
Q

What is the method for systematic sampling?

A

Belt transect made by stretching a string/tape along the ground in a straight line
Frame quadrat is laid down alongside the line and abundance is recorded
Moved a set length along the line and process repeated
Gives a record of species in a continuous belt

54
Q

What types of abundance are measured?

A

Frequency - likelihood of a species occurring in a quadrat, does not provide information on density and detailed distribution of a species
Percentage cover - estimate of area in a quadrat that a species covers

55
Q

What are the advantages and disadvantages of measuring % cover?

A

Adv: Rapid collecting of data
Individual organisms don’t need to be counted
Dis: Not useful when there are layers of overlapping layers

56
Q

What is mark-release-recapture?

A

Known number of animals are caught and marked
Released back into the community
New individuals captured randomly and the number of marked ones are recorded

57
Q

What is the equation for estimated population size in mark-release-capture?

A

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

58
Q

What are the assumptions made in mark-release-capture?

A

Proportion of marked:unmarked in 2nd sample is same as in the whole population
Marked individuals distribute evenly among others
Few births/deaths in population
Marking is does not cause death
Mark is not lost/rubbed off during the investigation

59
Q

Define succession

A

Changes, over time, in species that occupy a particular area

60
Q

What happens in a stage of succession?

A

A new species colonises the area

This could change the area

61
Q

What is primary succession?

A

Succession which starts from bare rock/barren land

62
Q

What is the first stage of succession?

A

Colonoisation of an inhospitable environment by organisms called a pioneer species

63
Q

Define pioneer species

A

Species which are able to colonise inhospitable environments

64
Q

What are some common features of pioneer species?

A

Adapted to tough environment (e.g xerophyte)
Ability to photosynthesize
Rapid germination of seeds (wind-dispersed)
Nitrogen-fixing from atmosphere
Asexual reproduction

65
Q

How does a pioneer species allow others to grow there?

A

Pioneers die and decay
Release nutrients and over time make soil
Mosses and ferns erode rock and increase the soil

66
Q

What are the normal stages of plant succession and examples ?

A

Colonisers -> Pioneers -> Weeds -> Shrubs -> Climax community
lichens -> grasses -> weeds -> bushes -> trees

67
Q

What is a climax community?

A

Organisms that make up the final stage of ecological succession
Applies for animals, relies on plants and each other

68
Q

What is the usual climax community in the UK?

A

Deciduous woodland

69
Q

What are some common features that emerge during succession?

A

Abiotic environment becomes less hostile - more soil meaning more water and nutrient retention
Increased number and variety of habitats
Greater biodiversity - increases until climax then slightly decreases
More complex food webs - increased biomass

70
Q

Define secondary succession

A

Land which has sustained life is altered (e.g forest fire) and undergoes succession

71
Q

How is secondary succession different?

A

Area goes through stages faster due to more soil there

Doesn’t begin with a pioneer species

72
Q

Define conservation

A

Management of the Earth’s natural resources by humans

Active intervention to maintain ecosystems and biodiversity

73
Q

What are the reasons for conversations?

A

Personal - maintain planet for our lives
Ethical - respect other living things
Economic - productivity is greater if ecosystems are maintained
Cultural/aesthetic - people find it inspirational

74
Q

How are habitats maintained by managing succession?

A

Species that lived before the climax community no longer present in climax community
Humans stop succession (e.g burning) to maintain these species

75
Q

How are moorlands managed?

A

Areas are burned to kill saplings etc. to prevent the climax community from forming

A Level - Biology (22 decks)

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