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A-Level EDUQUAS Biology > Component 1: Populations > Flashcards

Component 1: Populations Flashcards

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1
Q

Define ‘Population’

A

All the organisms, of a particular species, in a particular location at one time

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2
Q

Define ‘community’

A

All the organisms, of all species, living in one location at one time

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3
Q

Define ‘ecosystem’

A

A characteristic community of interdependent species ad their habitat

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4
Q

Define ‘habitat’

A

The location in which an organism lives

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5
Q

Define ‘niche’

A

The role of a particular species in its ecosystem, including its microhabitat, feeding and breeding behaviour etc

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6
Q

Define ‘ecology’

A

The study of how living organisms interact with each other and their environment

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7
Q

Define ‘environment’

A

The physical and biological conditions under which an organism lives

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8
Q

Define ‘biotic’

A

The biological components of an ecosystem

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9
Q

Define ‘abiotic’

A

The non-biological components in an ecosystem

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10
Q

What are some characteristics of ecosystems?

A
  • they are dynamic (constantly changing)
  • they vary in size
  • energy flow, biological cycles, succession, species composition and population size are all subject to change within an ecosystem
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11
Q

What does the population number depend on?

A
  • they fluctuate depending on birth rate, death rate, immigration into population and emigration from population
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12
Q

Population numbers will increase if…?

A

Birth rate + Immigration > Death rate + emigration

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13
Q

What is the birth rate term for when talking about yeast or bacteria?

A

REPRODUCTIVE RATE

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14
Q

What 2 factors influence the size of population in ecosystems?

A
  1. Availability of Light - more light will lead to an increase in population as there is more energy available
  2. Availability of Nutrients - increase the population as there is more energy available
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15
Q

Draw a population growth graph and label the 4 phases?

A 
1 = lag phase
2 = log phase
3 = stationary phase
4 = death phase
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16
Q

Describe what is happening in the lag phase for animals?

A
  • slow increase in population
  • birth rate is only slightly greater than death rate
  • there are very few organisms
  • sexually reproducing organisms may be reaching sexual maturity and find a mate
  • organisms are adapting to the environment
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17
Q

Describe what is happening in the lag phase for bacterium?

A
  • slow increase in population
  • reproductive rate is only slightly greater than death rate
  • very few bacteria
  • bacteria are adapting to the new culture/medium
  • bacteria are synthesising enzymes and proteins
  • replication of DNA and cells increase in size in bacteria
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18
Q

Describe what is happening in the log phase?

A
  • rapid increase as reproductive rate is greater than the death rate
  • resources are plentiful so there are very few limiting factors
  • environmental resistance is low, food availability is high and nutrients are high
  • bacterium: toxins are low
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19
Q

Describe what is happening in the stationary phase?

A
  • rate of growth slows as organisms start to compete for resources (limiting factors)
  • organisms are dying in equal numbers to those being reproduced (birth/reproductive rate = death rate)
  • population has reached the carrying capacity
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20
Q

Describe what is happening in the death phase?

A
  • death rate exceeds the reproductive rate
  • population crash
  • animals: caused by a natural disaster (floods/fires), disease or shortage of food
  • bacteria: caused by competition for nutrients or accumulation of toxins
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21
Q

What is meant by limiting factors?

A

Aspects of the environment, either physical or biotic, which restricts population size (causes environmental resistance to population growth

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22
Q

What are some limiting factors?

A

predation, parasitism, disease, overcrowding, competition from other species for food, accumulation of toxic waste (bacteria) and climate

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23
Q

What are density dependent factors?

A
  • the effect of these factors increases as the population density increases
  • these lead to a slow down in population growth
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24
Q

What are some example of density dependent factors?

A

parasitism, food availability, nesting site availability, predation, disease, territory availability and shelter
- toxin accumulation for bacterium

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25
Q

What are density independent factors?

A
  • the effects of these factors does not depend on population density
  • all living organisms are affected regardless of the population size
  • these can lead to a population crash
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26
Q

What are some examples of density independent factors?

A

soil pH, light, temperature, water pH, mineral nutrients, oxygen and any sudden/violent change in an abiotic factor (e.g. flood, fires, etc)

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27
Q

How does disease affect the population?

A
  • biotic factor
  • decreases the population
  • the denser the population the more rapidly disease spreads and therefore the greater impact of disease
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28
Q

How does light intensity affect the population?

A
  • abiotic factor
  • increasing light intensity increases the population as more energy is available for producers and this makes more food available for consumers
  • effect not dependent on population density
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29
Q

How does competition for food affect the population?

A
  • biotic factor
  • increasing the competition decreases the population
  • the greater the population the greater the impact as there are more individuals competing for the same resources
30
Q

How does the production of toxins affect the population?

A
  • biotic factor
  • population decreases as toxin concentration increases
  • the greater the population the more rapidly toxins accumulate
31
Q

How does predation affect the population?

A
  • biotic factor
  • as predation increases, the population decreases
  • also density dependent
32
Q

What is meant by ‘carrying capacity’?

A

The maximum population size that can be maintained over a period of time in a particular habitat/environment (or the maximum number around which a population fluctuates in a given environment)

33
Q

Why does population size fluctuate?

A
  • limiting factors change
  • when food supply or predation changes the population changes
  • if a herbivore population goes above the carrying capacity then it leads to overgrazing which would then lead to a population crash
  • carrying capacity is theoretical
  • a change in weather can result in a change in the numbers of a species that the environment can support
34
Q

What do plants compete for?

A

Light, water, space and mineral ions

35
Q

What do animals compete for?

A

Food, water, shelter, space and reproductive partners

36
Q

What are the two type of competition?

A

Intraspecific and interspecific

37
Q

What is intraspecific competition?

A

Competition between individuals of the same species

  • it can be an important factor in limiting the size of a population
  • it is a key factor in the evolution of a species by natural selection
38
Q

What is interspecific competition?

A

Competition between individuals of different species as 2 species cannot occupy the same niche in a specific habitat

  • niche overlap
  • the more overlap the more competition will happen
39
Q

When the niche overlaps the organisms may be competing for…?

A

food, oxygen, CO2, light, nutrient, nesting/dwelling sites

40
Q

What happens to the numbers of 2 different bacteria when placed in the same culture?

A
  • population will increase less rapidly than if they were grown alone as they compete for nutrients
  • one bacterium will outcompete the other as they may be better adapted for this niche
  • hence reproduces more rapidly and takes bulk of nutrients
  • therefore no 2 species can occupy the same niche
41
Q

Describe the snowshoe hare and lynx predator-prey cycle

A
  • in seasons where there is favourable weather, lots of plant growth, increased food for hare, pop increases as many young survive
  • the larger prey pop provides more food for the predators, more young predators survive, predator pop increases
  • as predator pop increases, prey pop decreases as more are eaten
  • later less prey is available as food, predator pop declined as intraspecific competition food (starvation)
42
Q

Why will the prey population rise before the predator?

A
  • prey may breed quickly (e.g. hares), food for predator increases, more survive and its pop can build
43
Q

As the predator population rises, why does the prey population fall?

A
  • a larger predator population, the greater predation pressure on the prey
  • loss exceeds the ability to replace (mortality > natality)
44
Q

What are some general points about predator-prey cycles?

A
  • fluctuations in predator numbers are smaller than those numbers in prey
  • fluctuations in predator numbers lag behind the fluctuations in numbers of prey
45
Q

What is ‘measuring abundance’?

A

A measure of how many individuals exist in a habitat

46
Q

How can plant abundance be measured?

A

Using a quadrat

47
Q

How can animal abundance be measured?

A
  • assessed by capture-mark-recapture experiments

- kick sampling in a stream and counting aquatic invertebrates

48
Q

What is meant by ‘measuring distribution’?

A

distribution of a species describes the are in which its found

49
Q

How do you measure the distribution of plants?

A

transect line with quadrats

50
Q

How do you measure the distribution of animals?

A
  • direct observation of nests or individuals
  • faecal deposits
  • marking on vegetation
51
Q

What is the food chain?

A
  • a diagram which shows a simple, unbranced, feeding relationship, usually with only one organism at each trophic level
  • the source of energy for most food chains is sunlight
52
Q

What do food chains not show?

A
  • all the species at each trophic level, calculated efficiency will be low
  • detritivores and decomposers which are often a greater biomass than other consumers
  • omnivores or organisms feeding at several trophic levels
  • food webs show all of these things
53
Q

What are some sources of energy in ecosystems?

A
  • the Sun is the source of energy for most ecosystems
  • light is trapped as chemical energy by photosynthesis
  • some ecosystems where energy comes from chemosynthesis (hydrothermal vents)
54
Q

What factors contribute to environmental resistance?

A

Predation, competition for food, disease, food availability and climate

55
Q

If environmental resistance increases, how would this affect the carrying capacity?

A
  • increasing resistance, decreases the carrying capacity
  • becomes more difficult for organisms to survive and breed
  • therefore fewer organisms can be supported by the environment
56
Q

Explain the lag phase for bacterium?

A
  • Genes are being switched on for synthesis of enzymes/proteins
  • Getting used to new medium
  • Replication of DNA
  • Cells increase in size
57
Q

What is meant by exponential growth?

A

Population grows at an increasing rate

58
Q

Reasons for decline phase in bacterium cultures?

A
  • competition for nutrients
  • accumulation of toxins
  • carrying capacity has been exceeded
59
Q

What does GPP stand for?

A

Gross Primary Prodcutivity

60
Q

What is GPP?

A
  • the rate of production of chemical energy in organic molecules by photosynthesis in a give area in a give time (kJ m^-2 y^-1)
  • most gross production is released by the respiration of the plant
  • on average GPP = 0.2% of the energy from the Sun hitting the Earth
61
Q

What does NPP stand for?

A

Net Primary Production

62
Q

What is NPP?

A
  • Energy in the plant’s biomass which is available to primary consumers (kJ m^-2 y^-1)
  • is the GPP minus the chemical energy generated in respiration nd used up by the metabolism of producers
63
Q

How is NPP calculated?

A

NPP = GPP - R

  • NPP represents the chemical energy available to heterotrophs in an ecosystem
  • GPP = 1% and NPP = 0.5% (would be higher if plants have a high photosynthetic effciency
64
Q

Difference between production and productivity?

A

Production (NPP) = quantity made

Productivity (GPP) = rate of production

65
Q

What is biomass?

A

The mass of biological material living, or recently living, organisms

66
Q

What is a trophic level?

A

Feeding level; the number of times that energy has been transferred between the Sun and successive organisms along a food chain

67
Q

What is a saprobiont?

A

A micro-organism that obtains its food from the dead or decaying remains of other organisms

68
Q

What do food chains show?

A
  • energy in the food consumed is incorporated into the molecules of the consumer (energy passes to higher trophic levels as material is eaten)
  • loss of energy from the ecosystem as it moves up
69
Q

What is decomposition?

A

detritivores and decomposers recycle nutrients and energy remaining in organic compounds

70
Q

What are detritivores?

A
  • E.g. worms
  • organisms that feed on small fragments of organic debris
  • a saprobiont
71
Q

What is a decomposer?

A

Microbes (bacteria and fungi) that obtain nutrients from dead organisms and animal waste (are saprobionts)

72
Q

What is the general order of a food chain?

A

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A-Level EDUQUAS Biology (24 decks)

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