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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
Give some examples of things organisms compete for
Water Food Breeding sites/partners
26
How does availability of resources effect population size in intraspecific competition?
Increase in availability causes increase in population
27
How does availability of resources effect population size in interspecific competition?
One population will normally have an advantage | That population will increase gradually and the other decreases
28
Can two species occupy the same niche if there are limiting resources?
No, cannot happen as one will have an advantage
29
What does an increase in food supply cause?
More individuals are likely to survive Increased probability of reproduction and population will increase Takes a long time to take effect
30
Define predator
An organism that feeds on another organism (prey)
31
Define prey
An organism that is eaten by another (predator)
32
How are predators adapted?
Better adapted for capturing prey | E.g - faster, better camo
33
How have prey become better at avoiding predators?
Better camo Protective features (spines) Concealment behaviour
34
Define predation
When one organism is consumed by the other
35
What occurs when a predator and prey are introduced in a lab?
Predator exterminates prey
36
What are the limitations of predator-prey interactions in labs?
The situation is completely different from real world More area that a prey can be found More diverse environment, places to hide
37
What happens to prey numbers when they get low?
Rarely goes extinct due to increased difficulty in finding and catching prey
38
What is the relationship of population size in predator and prey?
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
Define selection pressure
Individuals that survive (disease, predation, etc.) are more likely to survive and reproduce Causes evolution with advantageous traits
40
What is the abundance?
Number of individuals of a species in a given space
41
Why is it unreasonable to count every organism in a population?
Time-consuming | Causes damage to the environment
42
When can a conclusion be drawn about a habitat or population?
If the samples are representative of the habitat as a whole
43
What are the sampling techniques used in the study of habitats?
Random sampling using frame or point quadrats | Systematic sampling along a belt transect
44
What is a point quadrat?
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
What is a frame quadrat?
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
What should you consider when using quadrats?
Size of the quadrat Number of samples to take in the study area Position of each quadrat in the study area
47
Why should you consider the size of the quadrat?
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
Why should you consider the number of quadrat samples you take in an area?
More samples, more representative Balance between time-consuming and representative Greater number of species in the area, greater number of quadrats required
49
Why should you consider the position of each quadrat in the study area?
For statistically significant results random sampling must be used
50
Why is random sampling used?
Avoids bias in collecting data | Ensures reliable data
51
What is the method for sampling at random?
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
When should systematic sampling along belt transects be used?
When there is a gradual change in the communities of plants and animals
53
What is the method for systematic sampling?
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
What types of abundance are measured?
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
What are the advantages and disadvantages of measuring % cover?
Adv: Rapid collecting of data Individual organisms don't need to be counted Dis: Not useful when there are layers of overlapping layers
56
What is mark-release-recapture?
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
What is the equation for estimated population size in mark-release-capture?
estimated population size = (total individuals in first sample x second sample)/ number of marked individuals recaptured
58
What are the assumptions made in mark-release-capture?
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
Define succession
Changes, over time, in species that occupy a particular area
60
What happens in a stage of succession?
A new species colonises the area | This could change the area
61
What is primary succession?
Succession which starts from bare rock/barren land
62
What is the first stage of succession?
Colonoisation of an inhospitable environment by organisms called a pioneer species
63
Define pioneer species
Species which are able to colonise inhospitable environments
64
What are some common features of pioneer species?
Adapted to tough environment (e.g xerophyte) Ability to photosynthesize Rapid germination of seeds (wind-dispersed) Nitrogen-fixing from atmosphere Asexual reproduction
65
How does a pioneer species allow others to grow there?
Pioneers die and decay Release nutrients and over time make soil Mosses and ferns erode rock and increase the soil
66
What are the normal stages of plant succession and examples ?
Colonisers -> Pioneers -> Weeds -> Shrubs -> Climax community lichens -> grasses -> weeds -> bushes -> trees
67
What is a climax community?
Organisms that make up the final stage of ecological succession Applies for animals, relies on plants and each other
68
What is the usual climax community in the UK?
Deciduous woodland
69
What are some common features that emerge during succession?
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
Define secondary succession
Land which has sustained life is altered (e.g forest fire) and undergoes succession
71
How is secondary succession different?
Area goes through stages faster due to more soil there | Doesn't begin with a pioneer species
72
Define conservation
Management of the Earth's natural resources by humans | Active intervention to maintain ecosystems and biodiversity
73
What are the reasons for conversations?
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
How are habitats maintained by managing succession?
Species that lived before the climax community no longer present in climax community Humans stop succession (e.g burning) to maintain these species
75
How are moorlands managed?
Areas are burned to kill saplings etc. to prevent the climax community from forming

A Level - Biology (22 decks)

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