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biology > Populations > Flashcards

Populations Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

What is an ecosystem?

A

All of the living organisms and non-living components in a specific habitat and their interactions.

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2
Q

What are abiotic factors?

A

Non-living factors affecting organisms (e.g. temperature, light intensity).

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3
Q

What are biotic factors?

A

Living factors affecting organisms (e.g. food supply, predation).

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4
Q

What is a community?

A

All of the organisms of different species in a habitat.

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5
Q

What is a population?

A

All of the organisms of one species in a habitat.

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6
Q

What is a habitat?

A

The place where an organism lives

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7
Q

What is a niche?

A

The role of a species in an ecosystem, governed by adaptation to biotic and abiotic conditions (e.g. what it eats, what temp it can tolerate)

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8
Q

What is the biosphere?

A

The entire volume of the Earth’s surface where living things can be found.

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9
Q

What is a biome?

A

A large, naturally occurring community of flora and fauna occupying a major habitat.

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10
Q

How do you reduce the chance that a sample is not a true reflection of the population?

A

-Samples must be taken at random to avoid bias.
-Enough samples must be taken to get a representative result with a reliable mean, where anomalies can be calculated.

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11
Q

How is abundance measured?

A

By counting the frequency of a particular plant species (number of plants in a quadrat) or measuring % cover (area of a quadrat that is covered by a particular species).

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12
Q

What is the method for random sampling?

A

1) Place 2 long tape measures at right angles to each other as axes in the area to be studied.
2) Generate random numbers using a calculator etc.
3) Use these as coordinates on the axes to place the quadrats.
4) Count the number of plants of each species or estimate the % cover of each species in a quadrat. Do at least 10 quadrats.

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13
Q

What is the method for belt transect sampling?

A

1) Place a long tape measure across the sampling area.
2) Place quadrats at regular intervals.
3) Count the number of plants of each species or estimate % cover of each species in each quadrat. Do at least 10 quadrats.

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14
Q

When is belt transect sampling used?

A

To study the change in biodiversity across a habitat where there is an environmental gradient, e.g. wet to dry.

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15
Q

When is random sampling used and not used?

A

To avoid bias and study the biodiversity in an area where plants are randomly or uniformly distributed.
Not used if plants are grouped in clumps.

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16
Q

What is standard deviation?

A

A measure of the spread of data about the mean.

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17
Q

What does it mean if standard deviation bars overlap?

A

There is no significant difference in the 2 means, so they could be down to chance

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18
Q

What does it mean if standard deviation bars don’t overlap?

A

There is a significant difference between the 2 means

19
Q

What does a null hypothesis suggest?

A

That there is no significant difference or significant correlation.

20
Q

What does it mean if the p value is < 0.05?

A

The difference/correlation is significant because there is a less than 5% probability that the difference/correlation is due to chance.

21
Q

Suggest 2 advantages of estimating % cover rather than counting plants

A

-It’s quicker
-It may be hard to define individual plants

22
Q

Why are mobile animals hard to capture?

A

They move quickly and try to hide.

23
Q

Explain the process of the mark-release-recapture technique to estimate population size

A

-Capture a large sample of animals using a trapping technique.
-Count all of the animals in the first sample (S1) and mark them using non-toxic paint etc.
-Release all the animals in the first sample and give them time to mix with the rest of the population.
-Capture a second sample of animals using the same trapping technique.
-Count all of the animals in the second sample (S2) and record how many of these are marked (R).
-Use the equation S1xS2 / R

24
Q

What are the conditions for a valid estimate using the mark-release-recapture method?

A

-The mark does not affect survival.
-The mark persists during the investigation.
-The marked animals have enough time to mix randomly with the rest of the population.
-No births, deaths, immigration, or emigration between the first and second sample, so the population size remains constant.

25
Q

What is carrying capacity?

A

The maximum stable population size of a species that an ecosystem can support

26
Q

What is carrying capacity affected by?

A

-Abiotic (e.g. energy used to keep warm if cold surroundings, so less energy for growth and reproduction).
-Biotic factors (e.g. population of red squirrels is limited by competition with other red squirrels and grey squirrels)

27
Q

What is the competitive exclusion principle?

A

When 2 species are competing for limited resources, one uses them more effectively than the other, eliminating the other species.

28
Q

What is competition?

A

A struggle between individuals for resources that are not in adequate amounts to supply all individuals who depend on them.

29
Q

What does competition increase and decrease?

A

It increases death rate, but decreases reproduction rate.

30
Q

What is intraspecific competition?

A

Competition between individuals of the SAME species (competing for same resources as they occupy the same niche)

31
Q

Describe intraspecific competition

A

-When resources become scarce, intraspecific competition slows down population growth, so the population enters the stationary phase.
-Overall helps to keep the population stable.
It’s also the driving force between natural selection, as the best-adapted individuals will outcompete the less well-adapted. They are more likely to survive to reproduce to pass on the favourable alleles to offspring.

32
Q

What is interspecific competition?

A

Competition between individuals of DIFFERENT species for the same resource. E.g. grey squirrels outcompeting red squirrels.

33
Q

What are the 3 typical features of a predator-prey relationship?

A

-The numbers of both populations go up and down in a regular cycle.
-Predator numbers peak after prey numbers.
-Prey numbers are generally higher than predator numbers.

34
Q

What is succession?

A

A series of changes in a community of organisms over time.

35
Q

What is primary succession?

A

Development of a community from bare rock.

36
Q

What is secondary succession?

A

The development of a community after soil has been introduced.

37
Q

What are pioneer species?

A

Colonisers of bare rock (a hostile environment).

38
Q

Describe the process of succession, starting from bare rock

A

-The rock erodes, pioneer species die and decompose.
-This causes soil to form from the dead matter and conditions become less hostile. This allows small plants to grow, which then succeed the algae and lichen because they outcompete them (shade them from light etc).
-The soil gets deeper, with more humus and minerals, so larger plants can grow which outcompete the smaller plants, having deeper roots and a greater biomass.
-Biodiversity then increases as there is a greater variety of food sources for animals and a greater variety of niches.
-Index of diversity increases, as there is an increased number of species and individuals in these species.
-A climax community is formed.

39
Q

What is a climax community?

A

The final, stable community for a given climate (deciduous forest in UK).

40
Q

Describe how succession occurs (5) - exam style

A

-Colonisation by pioneer species
-Change in environment enables other species to colonise/survive
-Change in biodiversity
-Stability increases/environment becomes less hostile
-Climax community is established

41
Q

Describe the process of succession with sand

A

-Sand starts to pile up at the high tide line.
-Ridges of sand begin to accumulate.
-Pioneer plants such as marram grass begin to grow.
-They have an underground network of stems that stabilise the sand, allowing other species to colonise.
-The marram grass is outcompeted and dies out.
-Humus content of the soil increases.
-Shrubs begin to grow in the new soil, and trees then outcompete these.
-This is the climax community.

42
Q

What is conservation?

A

The protection and management of species and habitats in a sustainable way.

43
Q

How do burning and grazing/mowing prevent a climax community forming?

A

They both prevent trees from growing

44
Q

What are other ways of managing habitats and species for conservation?

A

-Seed banks (storage of seeds from plants under threat)
-Captive breeding (endangered species being bred in zoos)
-Fishing quotas (limiting fishing of certain species to protect future stocks)
-Protected areas (national parks etc to protect places from urban and industrial development)

biology (18 decks)

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