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A2 Biology 1 > Populations > Flashcards

Populations Flashcards

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1
Q

What is a population?

A

All the individuals of a particular species in a particular habitat at a particular time

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2
Q

What is an ecological niche?

A

Where an organism lives and it’s role in that habitat

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3
Q

What is a community?

A

All the individuals of different species in a particular habitat at a particular time

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4
Q

What is an autotroph?

A

A plant/ primary producer which manufactures its own food

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5
Q

What does a herbivore eat?

A

Autotrophs

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6
Q

What do secondary consumers eat?

A

Herbivores

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7
Q

What are decomposers?

A

Bacteria and fungi who obtain nutrients by breaking down the remains of dead organisms
They live in the soil (generally) and feed on detritus, dead, decaying organic matter. There are two groups, the detritivores and the saprobionts/saprophytes

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8
Q

Name some abiotic factors (4 marks)

A

Abiotic factors: the non-living/physical components of the environment (temperature, light, soil pH)
• Light intensity: affects plants only
• Carbon dioxide concentration: affects plant populations only
• Mineral ions: affects plants only
• Water availability: affects both plants and animals
• Temperature: affects both plants and animals

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9
Q

What are biotic factors?

A

A living factor that affects a population or a process (predation, competition, parasitism, disease)

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10
Q

What is the carrying capacity?

A

The highest population that can be maintained for an indefinite period of time by a particular environment

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11
Q

What is the climax community?

A

The final community in succession

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12
Q

What is the competitive exclusion principle?

A

Competitive exclusion principle: when two species are competing for limited resources the one using the resources most effectively will eliminate the other. Two species can’t occupy same niche indefinitely when resources are limiting

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13
Q

What do detritivores live on?

A

Detritivores: organisms that feed on dead or decaying organic matter

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14
Q

What is an Ecosystem?

A

A self-supporting system within which the organisms interact with each other and their physical environment
It is made up from all the interacting biotic and abiotic features in a specific area.

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15
Q

What is detritus?

A

Detritus: dead or decaying matter

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16
Q

What is a food web?

A

Food webs: a diagram showing all the feeding relationships in a single ecosystem or community

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17
Q

What is Gross primary production? / GPP

A

the rate at which chemical energy is stored in plants

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18
Q

What is Inorganic fertiliser?

A

A fertiliser containing inorganic ions such as, nitrate, ammonium, potassium and phosphate ions.

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19
Q

What is intraspecific competition?

A

Intraspecific competition: between members of the same species

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20
Q

What is Interspecific competition?

A

Interspecific competition: between members of different species

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21
Q

What is a limiting factor?

A

Limiting factor: the one factor of many that affect a process, that is nearest its lowest value and hence is rate-limiting.

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22
Q

What is Net Primary Production?

A

Net primary production: the energy that remains after the energy used in respiration has been subtracted from the gross primary production

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23
Q

What are pioneer species?

A

Pioneers species: species which are first to colonise cleared or disturbed ground.

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24
Q

What is primary succession?

A

Primary succession: succession that occurs on previously uninhabited ground

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25
Q

What is a pyramid of numbers?

A

Pyramid of numbers: A diagram that shows the number of organisms at each trophic level in an ecosystem/food chain at a given moment irrespective of size.

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26
Q

What is a pyramid of biomass?

A

Pyramid of biomass: A diagram that shows the total biomass at each trophic level in an ecosystem/food chain, at a given moment, irrespective of the numbers

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27
Q

What is a pyramid of energy?

A

Pyramid of energy: A diagram that shows the energy transferred to each trophic level of an ecosystem/food chain in a period of time irrespective of the numbers and biomass.

28
Q

What are saprophytes/saprobionts?

A

Saprophytes/saprobionts: microorganisms (fungi and bacteria) that feed through extracellular digestion, secreting enzymes onto organic matter and absorbing the soluble products into their body to use in respiration (releases carbon dioxide to the environment again for use in photosynthesis) or to use in assimilation building new cells (biomass)

29
Q

What is secondary succession?

A

Secondary succession: succession that occurs on in a place where there was some vegetation already present and the area has been disturbed by natural disaster or by deforestation etc.

30
Q

What is succession?

A

Succession: the process by which a community changes over time, a directional process where organisms affect the environment making it less suitable for themselves and more suitable for the next dominating species.

31
Q

What is a trophic level?

A

Trophic level: the position in a food chain at which an organism feeds

32
Q

What is random sampling, and how and why do you do it? (4)

A

Random sampling: to get a representative sample of the whole area. Area is divided into a grid using measuring tapes; random numbers are generated (from tables, calculator, computer) and used as co-ordinated to place quadrats.
There should be a large number of samples to be representative, allow for anomalies, and improve reliability and to allow statistical analysis. One should aim to sample 2% of the total area.

33
Q

What is systematic sampling, and how and why do you do it? (4)

A

Systematic sampling: used when you wish to investigate an environmental gradient (change across a habitat). Commonly this uses a transect. In the line transect the organisms touching the string are recorded. In a belt transect quadrats are placed at along the transect (it can be continuous, or interrupted, where quadrats are placed at regular intervals).

34
Q

What is the ACFOR scale?

A

Abundance scale: ACFOR, Abundant, Common, Frequent, Occasional, rare. Not quantitative, but can be made semi quantitative by making each point (ACFOR) correspond to a % cover range

35
Q

Why is it more difficult to sample animals than plants?

A

Sampling animals is made more difficult by the fact they move

36
Q

Give some examples of equipment you might use to sample animals? (4)

A

Sweep nets in long grass and crops to catch insects, standardise the sweeping time height to allow comparisons
Beating trays: used to get invertebrates from trees. Tree is hit with a stick and invertebrates fall into a tray
Pitfall traps: smooth sided cup buried in ground, a raised cover keeps out predators and rain. Used to catch invertebrates
Longworth traps: To catch small mammals: prepared with dry bedding and food; placed randomly in the area. Animals enter and trigger the door to close, they are safe from predators

37
Q

How might you assess the size of an animal population using mark recapture?

A

1 Capture a sample of animals using one of the trapping techniques described above. The larger the sample the better the estimate works.
2 Count all the animals in this sample (S1) and mark (using one of methods below) then so that they can be recognised later. Typical marks include: a spot of paint for invertebrates, leg-rings for birds, a shaved patch of hair for mammals, small metal disks for fish, etc. Larger animals can also be “marked” by collecting a small blood sample and making a DNA fingerprint. Ensure marking is not harmful to animals, or prevents reintegration to the population or that it will wash off, or that it makes them more susceptible to predators.
3 Release all the animals where they were caught and give them time to mix with the rest of the population (typically one day).
4 Capture a second sample of animals using the same trapping technique.
5 Count the animals in the second sample (S2), and the number of marked (i.e. recaptured) animals in the second sample (R).
6 Calculate the population estimate (N, the Lincoln-Petersen Index)

38
Q

What equation would you use for mark recapture?

A

N = S1 x S2
__________
R

39
Q

What assumptions do you make when carrying out Mark recapture?

A

Marking does not affect their survival
Capture of marked and unmarked animals is random
Marks are not lost
Animals mix with population again randomly and completely
There are no massive changes in population size between sampling s1 and s2 due to reproduction or migration/immigration, population thus remains stable between samples
Animals are not trap happy or trap shy

40
Q

What are the limitations of Mark recapture?

A

Animals must be captured which can harm them or alter behaviour steps taken to minimise this.
Marks can be lost
Marking could affect interaction with population after capture
‘Catchability’ of animals can vary with season, time of day, life stage, but assumes equal ‘catachability’.
Immigration/emigration/migration/birth and death issues can be overcome by having a small delay between sampling

41
Q

How does succession occur?

A

Colonisation of area by pioneer species; these organisms changes the environment; this enables new species to colonise;
Repetition of this process results in the environment becoming less hostile, biodiversity increases, providing food, habitat, nesting sites and niches,
Eventually a climax community is reached

42
Q

What is conservation?

A

Conservation: the concept of preservation/maintenance of biodiversity, through sustainable management of resources to maintain forests and the habitats/niches and food they supply that ultimately maintains biodiversity.

43
Q

What are the aims of conservation?

A

1) maintain diversity 2) maintain organisms’ habitats

44
Q

Give examples of sustainable management and reasons to preserve the indigenous species of a habitat…. (10)

A
  1. Protection of habitat: maintains food sources, nesting sites
  2. Legal measures like e.g. quotas, hunting bans: prevents populations falling to dangerously low numbers
  3. Capture/culling of non-native species: these can often replace/kill off indigenous species
  4. Captive breeding: to boost numbers of populations and ensure members of species are together at most fertile time
  5. Surrogacy / artificial insemination / genetic manipulation techniques;
  6. There may be cultural and aesthetic reasons for conservation and a link to tourism and the economic benefits to economy.
  7. Possible undiscovered benefits where some genes may provide medicinal products or characteristics for biotechnology.
  8. Maintaining genetic diversity for future breeding programmes.
  9. Avoid damage to food webs and it helps control local pests.
  10. Ethical reasons, taking into consideration other organisms have occupied the earth longer than man and should be respected
45
Q

One key area of controversy is deforestation. This is essential for building material, paper, farmland, urbanisation, fuel. However, it leads to many problems. What are they? (5)

A
  1. Soil erosion/ mud slides / flooding / leaching of minerals – trees no longer protect soil from rain / from wind / roots no longer hold soil;
  2. Increased CO2 (in air) OR “greenhouse effect” – trees remove
    CO2 in photosynthesise, the large scale felling of trees and subsequent decay or burning releases CO2.
  3. Less diversity– loss of food / loss of habitat / niches
  4. Changed rainfall patterns / drought – less transpiration from trees;
  5. Loss of pharmaceuticals / ‘medicines’ / timber / ‘wood’;
46
Q

So why conserve a forest ecosystem? (5)

A

5 from :
Trees available as a sustainable resource;
Maintain habitats / niches / shelter;
Maintain diversity / avoid loss of species / protect endangered species.
Maintain stability (of ecosystem);
Maintain food chains / webs / supply of food;
Reduced loss of soil / erosion;
Reduced flooding;
Act as carbon sink / maintain O2 and C02 balance reduce greenhouse effect
Reduce global warming;
Source of medicines;

47
Q

Decay/decomposition/rotting/putrefaction: is the breakdown of detritus by organisms collectively known as decomposers. There are two groups of decomposers? Name them….

A

1) Saprobionts (previously called saprophytes): these are microbes (bacteria and fungi)
2) Detritivores: small invertebrates that eat detritus

48
Q

Tell me about saprobionts…. (5)

A
  • Use saprobiotic nutrition, extracellular digestion
  • They secrete digestive enzymes
  • Absorb the soluble products
  • Use these in aerobic respiration
  • Release carbon dioxide

Some of the bacteria have cellulose to break down plant fibres. Herbivores depend on these in their guts. Other enzymes like deaminase help with the ammonification process in N cycle.

In terrestrial environments the main saprobionts are fungi. Fungi are composed of long thin hyphae that grow throughout the soil giving a large SA:VOL . In aquatic environments the main saprobionts are bacteria

49
Q

Tell me about detritivores…. (5)

A

Detritivores: Use holozoic nutrition
Ingest food, digest it in a gut, absorb soluble products and egest waste.
They speed up digestion by helping the activity of saprobionts by……
Increase surface area of detritus for saprobionts
Tunnelling activity: aerate soil, provides oxygen for saprobionts to respire aerobically
Excrete useful minerals (urea) which saprobionts can metabolise

50
Q

Explain how the predator prey relationship works (4)

A

The population sizes of the predator and prey are interdependent.
An increase in the prey population means more food and delayed increase in the predator population follows.
The increased number of predators kills more prey, so prey numbers fall
Lack of food means predators numbers fall

51
Q

Why is a predator prey graph not the full story?

A

Although the predator prey relationships are a significant contributor to the fluctuations they are not the only reasons as disease, arrival of new predators and climatic factors may also act. The changes in population are not always as severe as shown in many illustrations; this is because organisms usually have a number of food sources.

52
Q

Why do you get a lag phase initially in a population graph?

A

Lag phase: small numbers initially and the time needed to breed and for young to reach breeding age

53
Q

What happens in the exponential phase of population growth?

A

Exponential phase = rapidly increasing numbers in the population

54
Q

What happens in the stationary phase of population growth?

A

Stationary phase: carrying capacity is reached and the population remains relatively constant. Slight fluctuations in the population now affected by, food, predation, competition

55
Q

If we were looking at growth, in say, bacteria or wild animals and there was a 4th phase at the end, what might be happening?

A

A 4th phase (decline phase) of the population curve may exist (usually not in a natural environment) in certain circumstances and here there is a decline in the population due to depleting resources for numerous possible reasons
Human influence (hunting, deforestation, urbanisation)
Or in bacterial growth when nutrients run out

56
Q

Can populations grow indefinitely?

A

No population will grow indefinitely as the availability of resources and competition for these will limit growth. The factors that limit growth….Are called Environmental resistance and can be density-dependent or density-independent

57
Q

What is intraspecific competition and why can it be more intense than interspecific? (3)

A

Intraspecific competition: competition for resources between members of the same species, this is most intense as members have the same niche competing for exactly the same resources. This has a stabilising effect on a population, if population gets too big intraspecific competition increases and the population falls again. This is the driving force behind natural selection, as variants that are best competitors will survive and pass on their genes

58
Q

What limits population size in most animals?

A

The population of most animals has been kept in check by the availability of food, disease, climate, predators to name some of the limiting factors of the environment

59
Q

What advancements have made the human population explosion more extreme?

A

The development of agricultural practice, The industrial revolution, Recycling,
Medical advances, Understanding diets, Waste management, Improved quality of food

60
Q

What factors does population growth depend on? (4)

A

The increase in population, or growth rate, depends on four factors:
Growth rate = (birth rate – death rate) + (immigration rate – emigration rate)

61
Q

What has the staggering growth rate of the human population been mainly due to?

A

The equation shows that growth rate can increase by increasing the birth rate or decreasing the death rate (ignoring migration). The staggering human population growth over the last two centuries is entirely due to a massively decreased death rate caused by the improvements in farming described earlier, and in medicine. The increased growth rate has therefore happened at different times for different countries.

62
Q

What factors affecting birth rates? (5)

A

Factors affecting birth rates
Economic conditions – usually lower income = higher birth
Religion – some religions encourage big families and are against birth control
Social pressure/conditions – a large family can improve social standing
Birth control – pills and abortion can affect
Political factors – governments influence by taxation and education

63
Q

What factors affecting death rates?

A

Age profile – greater proportion of elderly the higher the death rate
Life expectancy – longer in MEDNs
Food supply – adequate and balanced diet reduce death rate
Water supply and sanitation
Medical care
Natural disasters
War

64
Q

What are the stages in the demographic transition model? (4)

A

Stage 1
High birth and death rates: Limited food causes starvation. Disease causes high but fluctuating death rate. Young are very susceptible to disease and starvation so high infant mortality rate. Short life expectancy means populations remain low and stable
Stage 2
More reliable food supply, improving nutrition, and improved living conditions and reduced disease reduces death rates. Birth rates are high so population growth is rapid.
Stage 3
Significant fall in birth rate is linked to social change. The increase in industrialisation and urbanisation means that families are less dependent on having children to contribute to the household. Birth control is practised.
Stage 4
Stable population with low birth and death rates. Typically death rate is low and stable, birth rate is more variable. Proportion of elderly increases. In some countries death rate now exceeds birth rate a population declines (a possible 5th stage to this model)

65
Q

What doe the demographic transition model lead to? How can we illustrate what is happening?

A

The demographic transition model leads to a change in the age structure of a population. These changes can be illustrated in population pyramids or survival curves

66
Q

How do we calculate birth rate?

A

(number of births/ number of adults) X 1000

67
Q

How do we calculate death rate?

A

(number of deaths/number of adults) X 1000

A2 Biology 1 (9 decks)

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