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A level biology > Populations And Ecosystems > Flashcards

Populations And Ecosystems Flashcards

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1
Q

What are the factors controlling population size

A

Intensity of energy flowing through the ecosystem varying
Biological cycles e.g nitrogen cycle causing mineral availability to vary
Succession causing habitats to change
Arrival /removal of new species
Climate change altering habitats

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2
Q

What factors determine the population size in a particular time of a habitat

A

Birth rate or natality
Death rate /mortality
Immigration
Emigration

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3
Q

What are fugitive species

A

Species that are poor at competition so rely on a large capacity for reproduction and dispersal to increase numbers they invade new environments rapidly e.g algae colonising rock

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4
Q

How do equilibrium species control their populations

A

Through competition within a stable habitat
Usual pattern of growth is an s shaped curve (one step growth curve )

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5
Q

What is a population

A

An interbreeding group of organisms of the same species occupying a particular habitat

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6
Q

What is a birth rate

A

Reproductive capacity of a population ; number of new individuals derived from reproduction per unit time

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7
Q

What is immigration

A

Movement of individuals into a population of the same species

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8
Q

What is an equilibrium species

A

Species that control their population by competition rather than reproduction and dispersal

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9
Q

What are the four phases in the one step growth curve

A

Lag phase
Exponential phase
Stationary phase
Death phase

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10
Q

What happens during the lag phase

A

Initially there is no growth which then turns to slow growth
Adaptation or preparation for growth intense metabolic activity e.g enzyme synthesis
In sexually reproducing animals it is the time taken to reach sexual maturity

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11
Q

What happens in the exponential /log phase

A

Numbers increase and more individuals become available for reproduction

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12
Q

What factors can affect rate of increase the exponential phase

A

Environmental resistance eg
Less food available
Conc of waste product becomes toxic not enough space / nesting sites
Biotic factors e.g predation , disease and parasitism and competition
For bacteria : accumulation of toxic waste , available food , overcrowding

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13
Q

What is the stationary phase

A

Occurs when birth rate is equal to death rate , population has reached its carrying capacity
Population not absolutely constant and fluctuates around environmental factors

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14
Q

What is the death phase

A

Factors that slow population growth at the end of the log phase become more significant and population size decreases until death rate is greater than birth rate and graph has negative gradient

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15
Q

How would you measure abundance of plants

A

Estimating percentage cover
Estimating percentage frequency
Using quadrat to calculate mean

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16
Q

What is a habitat

A

The place where an organism lives

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17
Q

What is a community

A

Interacting populations of two or more species in the same habitat at the time

18
Q

What is a trophic level

A

Feeding level at which the number of times that energy has been transferred between the sun and successive organisms along the food chain

19
Q

What is biomass

A

The mass off biological material In living or recently living organisms

20
Q

What is gross primary productivity

A

The rate of production of chemical energy in organic molecules by photosynthesis in a given area at a given time

21
Q

What is net primary productivity

A

Energy in the plants biomass that is available to primary consumers

22
Q

What is primary productivity

A

The rate at which energy is converted by producers into biomass

23
Q

What is secondary productivity

A

The rate at which consumers convert the chemical energy of their food into biomass

24
Q

What is the issues with pyramid of numbers

A

Doesn’t take into account size of organisms
May be so large it might have hard to draw to scale

25
Q

What is the issues with pyramid of numbers

A

Doesn’t take into account size of organisms
May be so large it might have hard to draw to scale

26
Q

What is the pyramid of energy

A

Represents feeding relationships
Showing the energy transferred from one trophic level to another

27
Q

What is the issue with pyramids of biomass

A

They do not indicate productivity or amount of energy flowing through the ecosystem
Species with similar biomass may have different lifespans so a direct comparisons of the total biomass may be misleading

28
Q

What do ecological pyramids show

A

A diagram that shows a particular feature of each trophic level in an ecosystem

29
Q

What are the issues with ecological pyramids

A

They do not take account of the fact that some organisms operate at more than one trophic level at the same time

30
Q

What is succession

A

The change in structure and species composition of a community over time

31
Q

What is a climax community

A

A stable self perpetuating community that has reached equilibrium with its environment and no further change occurs

32
Q

What is primary succession

A

The change in structure and species composition of a community over time in an area that has not previously been colonised

33
Q

What is a pioneer species

A

The first species to colonise a new area in ecological succession e.g algae

34
Q

What is a sere

A

The sequence of communities with the different species and structure

35
Q

What converts NH4+ to NO2- in nitrogen cycle

A

Nitrosomona

36
Q

What converts NO2- to No3- in nitrogen cycle

A

Nitrobacter

37
Q

What converts NO2- to No3- in nitrogen cycle

A

Nitrobacter

38
Q

What bacteria converts No3- to N2

A

Pseudomonas

39
Q

What bacteria converts N2 to NH4+ molecules in nitrogen cycle

A

Azotobacter

40
Q

What factors can cause dis climax

A

Human interference e.g
Sheep and cattle grazing maintains grassland and prevents shrubs and trees growing through normal succession
Deforestation removes larger trees which may be replaced with smaller ones

A level biology (10 decks)

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