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A2 AQA Biology - Burnley College (2024-25) > Genetics, Populations, Evolution & Ecosystems 3.7 > Flashcards

Genetics, Populations, Evolution & Ecosystems 3.7 Flashcards

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1
Q

Populations in ecosystems (AO1)

Define abiotic factor

A

A non-living / physical / chemical factor

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2
Q

Populations in ecosystems (AO1)

Examples of abiotic factors

A

soil pH
temperature
salinity (concentration of salt)
carbon dioxide concentration
humidity
light intensity

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3
Q

Populations in ecosystems (AO1)

Define biotic factor

A

Living / biological factor

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4
Q

Populations in ecosystems (AO1)

Examples of biotic factors

A

predator
prey / food
disease
presence of opposite sex

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5
Q

Populations in ecosystems (AO1)

Define population

A

Groups of organisms of the same species living in the same habitat / ecosystem at the same time;

They have the potential to interbreed;

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6
Q

Populations in ecosystems (AO1)

TRUE OR FALSE

Organisisms of the same species that make up a population have the potential to interbreed

A

TRUE

They will produce fertile offspring

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7
Q

Populations in ecosystems (AO1)

Define community

A

All the populations of the different species in the same habitat / ecosystem at the same time

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8
Q

Populations in ecosystems (AO1)

Define ecological niche

A

The role played by an organism in a
habitat/ecosystem governed by adaptations to biotic/abiotic factors

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9
Q

Populations in ecosystems (AO1)

Explain the advantage of different species occupying different niches (1 mark)

A

Reduced (interspecific) competition for food/resources

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10
Q

Populations in ecosystems (AO1)

Define carrying capacity

A

Certain size of population of a species that can be supported by the ecosystem

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11
Q

Populations in ecosystems (AO1)

What can reduce carrying capacity?

A

Habitat loss;

Reductions in food availability;

Increases in the number of predators;

Disease

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12
Q

Populations in ecosystems (AO1)

An ecosystem supports a certain size of population of a species, called the [1] capacity. There are often numerous habitats within an ecosystem. Within a habitat, a species occupies a [2] governed by an adaption to both [3] and biotic conditions. Populations of different species form a [4].

A

[1] carrying

[2] niche

[3] abiotic

[4] community;;

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13
Q

Populations in ecosystems (AO1)

Ecosystem definition

A

The interaction between a community and the abiotic components of the environment

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14
Q

Populations in ecosystems (AO1)

Competition between organisms of the same species is known as _________________ competition

A

intraspecific

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15
Q

Populations in ecosystems (AO1)

Competition between organisms of different species is known as _________________ competition

A

interspecific

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16
Q

Populations in ecosystems (AO1)

What term describes populations of different species living in the same habitat?

A

Community

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17
Q

Populations in ecosystems (AO1)

Describe and explain what typical patterns emerge when plotting the population sizes of predators and their prey over time (3 marks).

A

As prey populations increase, there is an increased availability of food for the predator population;

This causes a (delayed) increase in predator population;

Due to the increase in predators, the prey population
will decline;

A decline in prey populations leads to a shortage of food for the predators, and over time their population will also decline;

This decline reduces the predation on the prey population, allowing for interbreeding and an increase in the population size

(and repeat)

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18
Q

Populations in ecosystems (AO1)

In northern India, there is a conflict of interests between farmers of livestock (eg cows) and people trying to conserve ibex (a type of wild goat).

When livestock are given extra food, their populations can grow too large and compete with ibex.

Name the type of competition between livestock and ibex.

A

Interspecific

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19
Q

Populations in ecosystems (AO1)

Random sampling reduces __________

A

bias

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20
Q

Populations in ecosystems (AO1)

Random coordinates are produced using a ________________________

A

random number generator

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21
Q

Populations in ecosystems (AO1)

Measurements made within quadrat(s)

A

Number of individuals;
% cover;
Species richness;
Index of biodiversity;

22
Q

Populations in ecosystems (AO1)

Why use percentage cover rather than frequency / number of individuals to count algae.

A

Difficult / too many to count / individual organisms not identifiable / too small to identify/count / grows in clumps;

23
Q

Populations in ecosystems (AO1)

The sundew is a small flowering plant, growing in wet habitats such as bogs and marshes.

Describe how you could estimate the size of a population of sundews in a small marsh (4 marks).

A

1. Use a grid;

2. Use random number generator for random coordinates (for quadrats);

3. Large sample of quadarts (20 or more);

4. Add the total number/frequency in a quadrat and divide by number of quadrats;

5. Valid method of calculating total number of sundews, e.g. mean number of plants per m^2 multiplied by number of m^2 in marsh;

24
Q

Populations in ecosystems (AO1)

Describe how you would determine the mean percentage cover for beach grass on a sand dune (3 marks).

A

1. Use random number generator for random coordinates (for quadrats);

2. Large number of quadrats (20 or more);

3. Divide total percentage by number of quadrats;

25
Q

Populations in ecosystems (AO1)

Outline a method the ecologists could have used to determine the plant species richness at one site (3 marks).

A

1. Use random number generator for random coordinates (for quadrats);

2. Large number of quadrats (20 or more);

3. Count number of different plant species (in each quadrat)

Reject refs to % cover, or counting individuals

Species richness = all the different species (AS content)

26
Q

Populations in ecosystems (AO1)

In addition to a quadrat, what piece of equipment do you need to undertake systematic sampling?

A

Line / belt transect

27
Q

Populations in ecosystems (AO1)

In systematic sampling, quadrats are placed on a transect at ____________ intervals

A

regular

28
Q

Populations in ecosystems (AO1)

What type of analysis can systematic sampling using a line or belt transect allow you to undertake?

A

The impact of an environmental gradient on a population size.

29
Q

Populations in ecosystems (AO1)

Lettuce is classified in the same family as dandelions. Dandelions commonly grow on roadside verges and may accidentally be sprayed with salt when salt is added to the road in winter.

Describe how you could use a transect to investigate whether the distribution of dandelions changed with increased distance from the road (4 marks).

A
  1. Lay tape / rope at right angle / perpendicular to road;
  2. Take samples at regular intervals;
  3. Using a quadrat;
  4. Count numbers / percentage cover of dandelions;
  5. Use several transects;
30
Q

Populations in ecosystems (AO1)

Suggest one precaution needed when marking the pine martens (during mark, release & recapture) to make sure the estimate of the number of pine martens is valid (1 mark).

A

(Marking) does not affect survival/predation/recapture (of the pine marten);

OR

Mark does not rub/wash off/is non-toxic.

31
Q

Populations in ecosystems (AO1)

What are the assumptions made when using the the mark-release-recapture method to make valid estimates of population size?

A

1. The population size does not change between the two capture times.
* There should be no increase in predation of the marked organism
* There should be no migration

2. The marked organisms have enough time to (randomly) disperse/distribute into the rest of the population

3. The marking should not rub off or be lost

4. Sample population is large enough

32
Q

Populations in ecosystems (AO1)

Mark, release, recapture equation

A

You must be able to recall and apply this equation

33
Q

Populations in ecosystems (AO1)

Anolis sagrei is a species of lizard that is found on some of the smallest Caribbean islands.

Describe how you could use the mark-release-recapture method to estimate the number of Anolis sagrei on one of these islands (3 marks).

A

1. Capture sample, mark and release;

2. Method of marking does not make it more visible to predators (i.e. does not affect survivial the lizards);

3. Leave sufficient time for lizards to (randomly) distribute (on island) before collecting a second sample;

4. (Population =) number in first sample × number in second sample divided by number of marked lizards in second sample / number recaptured.

34
Q

Populations in ecosystems (AO2)

A

20

35
Q

Populations in ecosystems (AO2)

The scientists used the mark-release-recapture method to determine the number of pine martens in one area of forest. They captured, marked and released a first sample of 25 pine martens. A week later, they captured a second sample of 35 pine martens from the same area of forest. The scientists calculated that there were 125 pine martens in that area of forest.

Using the information provided, calculate how many pine martens in the second sample were marked.

A

7 pine martens

36
Q

Populations in ecosystems (AO2)

Blue tits are small birds that live in woods. An ecologist estimated the size of the blue tit population visiting gardens near a wood in November.

  • She trapped 28 blue tits. She marked all of these birds with small metal rings on their legs.
  • Two weeks later, she trapped another sample of blue tits. Of these birds, 18 were marked and 20 were not marked.

Use the data to estimate the size of the blue tit population.

A

59

37
Q

Succession (AO1)

Hostile environments such as rock and sand are colonised by ______________

A

pioneer species

38
Q

Succession (AO1)

Pioneer species example

A

Lichen

39
Q

Succession (AO1)

TRUE or FALSE:

Lichen are microorganisms

A

TRUE

Lichen are a symbiotic association between a fungus and algae and/or cyanobacteria

40
Q

Succession (AO1)

Characteristics of pioneer species

A

Photosynthesise;

Fix nitrogen;

Asexual reproduction;

Tolerance to hostile environments;

41
Q

Succession (AO1)

At each stage in [1], certain species may be recognised which change the [2] so that it becomes more suitable for other species with different adaptations. The new [3] may change the environment in such a way that it becomes less suitable for the previous species.

A

[1] succession
[2] environment
[3] species

42
Q

Succession (AO1)

Succession occurs in natural ecosystems.

Describe and explain how succession occurs (5 marks).

A

1. (Colonisation by) pioneer (species);
2. Change in environment / example of change caused by organisms present e.g. adds more humus;
(humus = is the formation of a thin / basic layer of soil)
3. Enables other species to colonise / survive;
4. Increase in biodiversity;
5. Stability increases / less hostile environment;
6. Climax community;

43
Q

Succession (AO1)

Final stage of primary succession

A

Climax community

44
Q

Succession (AO1)

Features of a climax community

A

1. Same species present (over long time) / stable community (over long time);

2. Abiotic factors (more or less) constant (over time)

3. Populations stable (around carrying capacity)

45
Q

Succession (AO1)

What happens to the pioneer species as succession progresses to the next stage?

A

They are outcompeted;

by species better adapted to the less hostile environment;

(This is a form interspecific competition)

46
Q

Succession (AO1)

The species that are present change during succession. Explain why (2 marks).

A
  1. Species / plants / animals change the environment / less hostile (habitat);
    e.g. add humus / nutrients etc.
  2. New species / plants that colonise this environment outcompete original species (e.g. pioneer species);
47
Q

Succession (AO2)

A

Crabgrass

48
Q

Succession (AO2)

A

1. Beach grass is the pioneer (species);

2. Pioneers/named species change the (abiotic) environment/habitat/conditions/factors;

Accept example of change e.g. more humus

3. (So) less hostile for named species OR
(So) more suitable for named species;

4. Conifer/hardwood trees represent climax community;

49
Q

Succession (AO2)

Explain the advantage to a plant that colonises 50 years after the pioneer species of having a high rate of photosynthesis at low light intensities.

A

Plant will grow / survive in the shade / when overshadowed (by taller plants) / when receiving less light;

Note that taller trees are a key feature of a climax community

50
Q

Succession (AO1)

Reasons for conserving rainforests

A

1. Conserve / protect
species / plants / animals / organisms

OR For (bio)diversity;

2. Conserve / protect habitats

OR Provides / many habitats ;

3. Reduces climate change;

4. Source of medicines/drugs/wood;

5. Reduces erosion/eutrophication;

6. (For) tourism;

51
Q

Succession (AO2)

Explain why conservation of habitats frequently involves management of succession.

A

Prevents a climax community from forming;

Habitats in earlier stage ofsuccession may be better for some species;

E.g. ground nesting birds on heather moorland

A2 AQA Biology - Burnley College (2024-25) (3 decks)

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