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Biology - Year 2 (Eduqas) > Chapter 5 - Population Size & Ecosystems. > Flashcards

Chapter 5 - Population Size & Ecosystems. Flashcards

1
Q

What is a populations size determined by?

A
  • Birth rate (Or any other way that an organism increases their numbers).
  • Death rate.
  • Immigration.
  • Emigration.
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2
Q

What are the 4 phases of a growth curve?

A
  • Lag phase.
  • Log (Exponential) phase.
  • Stationary Phase (Birth rate = Death rate).
  • Death phase (Birth rate < Death rate).
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3
Q

Why can’t the rate of increase in the log phase be maintained?

A

Because environmental resistance sets in.

  • There is less food available.
  • Concentration of waste products become increasingly toxic.
  • Not enough space/nesting sites.
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4
Q

What is environmental resistance?

A

Refers to environmental factors that slow down population growth.

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5
Q

What are the two types of factors that will affect a population size?

A

Density-dependent factors and Density-independent factors.

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6
Q

What are examples of Density Dependent/Independent factors?

A

Density Dependent - Depletion of food supply, parasitism.

Density Independent - Flood, Fire.

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7
Q

What is an Ecosystem?

A

A characteristic community of interdependent species interacting with the abiotic components of their habitat.

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8
Q

What is the carrying capacity of a species?

A

The maximum population size that can be maintained over a period of time by an environment.

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9
Q

What is the abundance of a species?

A

The number of individuals in a species in a given area or volume.

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10
Q

How can animal/plant abundance be assessed?

A
  • Mark-Release-Recapture.
  • Kick sampling.
  • Using a quadrat (Mean number of individuals/%age cover/%age frequency).
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11
Q

What is the most significant energy source for ecosystems?

A

The sun.

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12
Q

What is a trophic level?

A

A feeding level; the number of times that energy has been transferred between the sun and successive organisms along a food chain.

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13
Q

What is the difference between a Detritivore and a Decomposer?

A

Detritivore - Organisms (worms, woodlice etc.) that feed on small fragments of organic debris (Detritus).
Decomposers - Microbes (Fungi, Bacteria etc.) that obtain nutrients from dead organisms and animal waste.

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14
Q

What is the difference between Primary productivity and Secondary productivity?

A

Primary - Rate at which energy is converted by producers into biomass.
Secondary - Rate at which consumers convert the chemical energy of their food into biomass.

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15
Q

Why is it that about 60% of the sunlight that falls on a plant isn’t absorbed by photosynthetic pigments?

A
  • The light may may be the wrong wavelength.
  • Reflected.
  • Absorbed by non-photosynthetic parts of the plant.
  • Transmitted through the leaf.
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16
Q

What is Gross Primary Productivity?

A

The rate of production of chemical energy in organic molecules by photosynthesis.

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17
Q

What is Net Primary Productivity?

A

What is left of GPP after some is released by the respiration of the plant.

18
Q

Why is energy lost at each trophic level of a food chain?

A
  • Energy in molecules that are egested.
  • Some energy lost as heat.
  • Energy remains in molecules in parts that aren’t eaten.
19
Q

Why are Carnivores more efficient at energy conversion compared to herbivores?

A

Carnivores food is more easily digested as they produce the correct enzymes to digest it. Herbivores need a separate gut bacteria in order to digest the cellulose cell wall in their food.

20
Q

What are the problems with a pyramid of numbers?

A
  • Doesn’t take into account size of the organism.
  • Doesn’t differentiate between Juvenile and adult forms.
  • Range of number may be so large, drawing to scale may be difficult.
  • Pyramid may be inverted.
21
Q

What Ecological Pyramid is the most accurate way of representing feeding relationships?

A

A pyramid of energy.

22
Q

When may a pyramid of biomass be inverted?

A

In an aquatic ecosystem when the standing crop of phytoplankton is larger than the zooplankton.

23
Q

What is the difference between primary succession and secondary succession?

A

Primary - Change in structure and species composition of a community over time in an area that has not been previously colonized.
Secondary - The changes follow the disturbance/damage to a colonised habitat.

24
Q

What is a climax community?

A

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

25
Q

What is the sequence of communities, with different species and structures called? and what can it be divided up into?

A

Sere.

Seral stage.

26
Q

What is a pioneer species?

A

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

27
Q

What factors will affect succession?

A
  • Migration.
  • Competition.
  • Inter-species relationships.
28
Q

What is the difference between Inter-specific Competition and Intra-specific competition?

A

Inter - Competition between individuals of different species.
Intra - Competition between individuals of the same species.

29
Q

What is a niche?

A

The role and position a species has in it’s environment, including all interactions with the biotic and abiotic factors of its environment.

30
Q

What is the difference between Commensalism and Mutualism?

A

Commensalism - An interaction between organisms of two species from which one benefits but the other is un-affected.
Mutualism - Interaction between organisms of two species from which both derive benefit.

31
Q

What human activities have caused the levels of CO2 in the atmosphere to rise?

A
  • Burning fossil fuels.

- Deforestation.

32
Q

What 3 main biological processes contribute to the Carbon cycle?

A
  • Respiration.
  • Photosynthesis.
  • Decomposition.
33
Q

What are the 2 ways that deforestation releases CO2 back into the atmosphere?

A
  • Trees remove CO2 from the atmosphere through photosynthesis.
  • Their burning/Decomposition releases CO2 into the atmosphere.
34
Q

What is Global Warming?

A

The increase of average global temperature, in excess of the greenhouse effect caused by the atmosphere’s historical concentration of CO2.

35
Q

What are some of the consequences of global warming?

A
  • Melting of polar ice/
  • Increased frequency of extreme weather conditions.
  • Increased frequency of forest fires.
  • Expansion of deserts.
  • Extinction of species.
  • World food production may decrease.
36
Q

What is a carbon footprint?

A

The equivalent amount of Carbon Dioxide generated by an individual, a product or a service in a year.

37
Q

How can we reduce the production of greenhouse gases?

A
  • Recycle.
  • Drive less.
  • Use less air conditioning/heating.
  • Reduce meat consumption (especially red).
  • Avoid food waste.
  • Plant trees (Afforestation).
38
Q

What are the 5 main bacteria involved in the Nitrogen cycle and what do they do?

A
  • Rhizobium (In root nodules of Legumes); Nitrogen Fixation.
  • Azozotobacter (Free in soil); Nitrogen fixation.
  • Nitrosomonas; Ammonium to Nitrites.
  • Nitrobacter; Nitrites to Nitrates.
  • Pseudomonas; Denitrifying bacteria.
39
Q

What is the process that converts Detritus into Ammonium?

A

Ammonification.

40
Q

What human activities can improve the circulation of nitrogen in agricultural soils?

A
  • Ploughing fields.
  • Draining land.
  • Artificial Nitrogen fixation (e.g. Haber process).
  • Using ‘brown’ manure.
  • planting field of legumes and then plough back into the soil as ‘green’ manure.
41
Q

What can excessive use of fertilizers cause in nearby streams?

A

Eutrophication - The artificial enrichment of aquatic habitats by excess nutrients, often caused by run-off fertilisers.

42
Q

What measures can be taken to reduce the likelihood of eutrophication?

A
  • Restrict the amount of fertilizer applied to the soil.
  • Only apply when crops are actively growing.
  • Leave at least 10m strip next to watercourses.
  • Dig draining ditches.

Biology - Year 2 (Eduqas) (14 decks)

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