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A2 BIO UNIT3 > 3.5 Populations & Ecosystems > Flashcards

3.5 Populations & Ecosystems Flashcards

1
Q

Population

A

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

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2
Q

Community

A

The interacting populations of two or more species in the same habitat at one time

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3
Q

Biotic factors

A

A part of the environment of an organism that is living ie pathogens or predators

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4
Q

Abiotic factors

A

A part of the environment of an organism that is non-living eg air, temp, oxygen etc

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5
Q

Habitat

A

Place in which an organism lives which is part of an ecosystem

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6
Q

Niche

A

Role and position a species has in its environment including all interactions with the biotic and abiotic factors of its environment

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7
Q

Ecosystem

A

A characteristic community of interdependent species reacting with the abiotic components of their habitat that are fairly inform

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8
Q

What is an exclusion principle and how can it be overcome?

A
  • when 2 species try to occupy the same niche and one outcompetes the other
    —> resource partitioning is the only way this can happen as enables the same habitat with a different niche ie Darwins finches
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9
Q

Factors that increase and decrease population

A

+: birth and immigration
-: death and emigration

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10
Q

Intraspecific and interspecific competition

A

Intra: 2 or more organisms of same species compete
Inter: 2 or more organisms of different species compete

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11
Q

Carrying capacity

A

Max number of species a habitat can support in the most unfavourable conditions without harming the habitat or organisms

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12
Q

Exponential graph

A
  • increasing at increasing rate
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13
Q

Log graph

A
  • period of rapid growth and stability
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14
Q

Density independant factors

A
  • reduce population numbers independently of the population density
  • ie forest fires, floods
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15
Q

Density dependant factors

A
  • biotic factors that cause population to decrease when high and increase when low
  • ie predation, competition, disease
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16
Q

Factors that determine size of population

A
  • birth rate
  • death rate
  • immigration
  • emigration
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17
Q

What is the difference between fugitive species and equilibrium species?

A
  • fugitive species are poor at competition - they rely on a large capacity for reproduction and dispersal to increase their numbers. They can invade a new enviro rapidly
  • equilibrium species control their population by competition within a stable habitat. S shaped curve called one step growth curve
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18
Q

Draw and label the one-step growth curve

A
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19
Q

Explain predator-prey relationships

A
  • abundance of prey limits predators and number of predators controls the number of prey
  • predator-prey relationship causes both populations to oscillate and these oscillations are regulated by negative feedback
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20
Q

Define distribution

A

The area or volume in which the organisms of a species are found

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21
Q

Describe the possible energy sources on earth

A
  • energy derived from an unequal distribution of protons allowed the non-living systems in the cavities of alkaline hydrothermal vents to make the transition to living systems
  • early organisms used energy released by chemical reactions to make carbohydrates by chemosynthesis. Electrons they need to reduce carbon dioxide or methane to sugar are derived from oxidation of inorganic molecules such as hydrogen or hydrogen sulphide
  • light energy radiating from sun is source for photosynthesis
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22
Q

Define trophic level

A
  • feeding level
  • the number of times that energy has been transferred between the sun and successive organisms along the food chain
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23
Q

Explain the order of the food chain

A
  • green plants and some protoctista are called producers because they incorporate the suns energy into carbs and are therefore the energy source for successive organisms
  • herbivores are primary consumers
  • carnivores are secondary, tertiary and higher consumers
  • there is a loss of energy at each trophic level
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24
Q

Define a saprobiont

A
  • organism that derives energy and raw materials for growth from extracellular digestion of dead or decaying material
  • detrtiivores feed on remains of dead organisms and decomposes complete the process of decomposition
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25
Q

What impacts the length of food chains?

A
  • the more energy that enters a food chain through photosynthesis, the longer the food chain
    —> ie tropical longer than arctic
  • if energy is transferred efficiently between trophic levels the food chain is longer
  • predators and prey fluctuate and their relative abundance affects food chain length
  • larger ecosystems support longer food chains
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26
Q

Why does about 60% of the light energy that falls on a plant not get absorbed by photosynthetic pigments?

A
  • wrong wavelength
  • reflected
  • transmitted straight through leaf
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27
Q

Define photosynthetic efficiency, including formula

A
  • measure of the ability of a plant to trap light energy

Quantity of light energy incorporated into product
———————————————————————- x100
Quantity of energy falling on the plant

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28
Q

What determines photosynthetic efficiency?

A
  • plants genotype
  • environmental factors such as light intensity and temp
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29
Q

Define gross primary productivity

A
  • rate of production of chemical energy in organic molecules by photosynthesis in a given area in a given time, measured in kJ m^-2 y^-1
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30
Q

Define net primary productivity

A
  • energy in the plants biomass which is available to primary consumers, measured in kJ m^-2 y^-1
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31
Q

Link between photosynthetic efficiency and GPP and NPP

A
  • GPP and NPP are higher if plants have high photosynthetic efficiency

GPP - respiration = NPP

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32
Q

Define primary and secondary productivity

A

Primary: the rate at which energy is converted by producers to biomass

Secondary: the rate at which consumers convert the chemical energy of their food into biomass
—> accumulate energy from assimilated food

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33
Q

Why is there an energy loss from the food chain at each level?

A
  • there is energy in molecules egested
  • energy lost as heat in processes fuelled by energy generated in respiration
  • energy remains in molecules in parts of an animal that may not be eaten
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34
Q

Equation for efficiency of energy transfer

A

Energy incorporated into biomass after transfer
——————————————————————- x100
Energy available in biomass before transfer

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35
Q

Disadvantages of pyramid of numbers

A
  • does not take into account size of organisms
  • does not recognise the difference between juvenile and adult forms
  • range of numbers can be v large so difficult to draw to scale
  • pyramid may be inverted if one trophic level has more organisms than the previous
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36
Q

Pyramid of energy

A
  • most accurate representation of
  • never inverted
  • easy to compare efficiency of energy transfer between trophic levels in different communities
37
Q

Pyramid of biomass

A
  • closely related to energy passing through ecosystem
  • difficult to measure accurately
  • do not indicate productivity or amount of energy flowing through ecosystem
  • may be inverted
  • trophic levels may appear to contribute more to the next level than they actually do
  • species with similar biomass may have diff lifespans so direct comparison is misleading
38
Q

Succession

A

A directional change in a community and the species it contains over time due to a change in environment

39
Q

Climax community

A

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

40
Q

What is the difference between detritivores and decomposes?

A

Detritivores: eat remains of dead plants and animals
Decomposers: breakdown matter and feed on it (saprotrophs)

41
Q

Stages of the carbon cycle

A
  1. Photosynthesis - carbon dioxide added to aid
  2. Respiration - reuses almost as much CO2 as is released into atmosphere
  3. Decomposition - production of carbohydrates, proteins and fats contributes to plant growth and subsequently to animal growth through complex food webs
42
Q

What factor has the most influence on carrying capacity?

A

Biotic factors

43
Q

Difference between peat and coal

A
  • peat: partly decayed dead plants
  • coal: fully decayed plant material squished over millions of years
44
Q

2 main causes of increased CO2 levels

A
  • burning fossil fuels released locked CO2
  • deforestation removes photosynthesis biomass so less CO2 absorbed
45
Q

Explain how deforestation impacts carbon cycle

A
  • cut down trees means less CO2 is absorbed by stomata in leaves
  • more CO2 remains in atmosphere
  • less photosynthesis occurs
  • CO2 released by respiration cannot be absorbed so alters net CO2
46
Q

Explain how combustion of fossil fuels impacts carbon cycle

A
  • burning of coal, oil and gas released CO2 and other gases
  • too much in atmosphere to be continually reabsorbed which means more remains in atmosphere
  • burning fossil fuels releases CO2 from carbon in plants and animals from millions of years ago
47
Q

Name greenhouse gases and briefly explain the concept

A
  • CO2, CH4, NO, fluoridated gases
  • solar radiation hits earths surface, reflects back into space, gases prevent reflection, heat is trapped
48
Q

Impacts of GW

A
  • melting ice caps
  • extreme weather
  • forest fires
  • desertification
  • migration of species to exploit better enviro
  • increased pests
49
Q

Impacts of GW on agriculture practise

A
  • improve soil by crop rotation to increase fertility
  • reduce meat rich diets
  • cover soil in clover between crops
  • improve drainage to avoid waterlogged soil
  • salt tolerant crops via GE
50
Q

Impacts of GW on agriculture practise

A
  • improve soil by crop rotation to increase fertility
  • reduce meat rich diets
  • cover soil in clover between crops
  • improve drainage to avoid waterlogged soil
  • salt tolerant crops via GE
51
Q

Define carbon footprint

A
  • total amount of carbon dioxide attributable to a person/product/company over one year
52
Q

How does global warming impact the ocean?

A
  • decreases pH - CaCO3 is external skeleton of corals and molluscs and is dissolved by acidity
  • increases temp - corals expel mutualistic algae and lose colour and carbohydrate source as a result
53
Q

What is the nitrogen cycle?

A

The flow of nitrogen atoms between organic and inorganic nitrogen compounds and atmospheric nitrogen gas in an ecosystem

54
Q

What is the importance if nitrogen and why can’t it remain as N2?

A
  • amino acids, nucleic acids, chlorophyll, protein
  • has a triple bond which requires a lot of energy to break and a certain enzyme that plants do not have
55
Q

Ammonia

A

NH3

56
Q

Nitrite

A

NO2-

57
Q

Ammonium

A

NH4+

58
Q

Nitrate

A

NO3-

59
Q

Stages of the nitrogen cycle

A

1A. Nitrogen fixation
1B. Ammonification
2. Nitrification
3. Dentrification

60
Q

Explain nitrogen fixation

A
  • biosphere relies on several prokaryotic species which possess enzymes that can reduce nitrogen (N2) to ammonium ions (NH4+)
    —> nitrogenase enzymes break triple bond
    —> azotobacter and rhizobium
  • nitrogen gas diffuses into root nodule and nitrogenase catalyses N2 —> NH4+
  • very energy intensive so lots of mitochondria in root nodule
  • reduction reaction so needs anaerobic conditions
    —> nitrogenase is poisoned by O2
61
Q

Describe azotobacter

A
  • free living in soil
  • accounts for conversion of N2 —> NH4+
  • high respiratory rate which leaves anaerobic conditions for nitrogenase
62
Q

Describe rhizobium

A
  • symbiotic
  • root nodules of legumes
  • break triple bond for conversion of N2 —> NH4+
  • benefits from symbiosis by utilising carbohydrates from photosynthesis
63
Q

What do the genes in nodules code for?

A
  • leg-haemoglobin which prevents O2 entering root nodules, maintaining efficiency
  • makes nodules go pink
64
Q

Describe ammonification

A
  • decomposition of dead organic matter to release NH4+ into soil

1) proteases digest protein into amino acids
2) deaminases remove amine groups from AAs and reduce them to NH4+
3) digestion products are absorbed by decomposers

65
Q

Describe nitrification

A
  • oxidation of ammonium ions and intermediate products (NO2-/NO3-)
  • facilitated by aerobic bacterial species
    —> chemotrophic bacteria

NH4+ ———> NO2- ———> NO3-
Nitrosomonas Nitrobacter

66
Q

Describe dentrification

A
  • loss of nitrate from soil
  • anaerobic bacteria convert NO3- to N2 (released back to atmosphere)

NO3- ———> N2
Pseudomonas

67
Q

Non-biological process that effect the nitrogen cycle

A
  • addition of fertilisers that add nitrogen to soil
  • lightning adds small amount of nitrogen to soil
  • leaching of minerals removes nitrogen from soil
68
Q

How does ploughing fields impact the nitrogen cycle?

A
  • aerates the soil which favours:
    —> aerobic organisms enhancing the formation of ammonium ions in the soil
    —> nitrifying bacteria and therefore enhances the conversion of ammonium into nitrites and nitrates
    —> mineral uptake because plant roots respire aerobically to produce ATP
69
Q

How does draining land impact the nitrogen cycle?

A
  • allows air to enter soil and so reduces the anaerobic conditions which favour denitrifying bacteria
70
Q

Primary succession vs secondary succession

A

Primary: change in structure and species composition of a community over time in an area that has not been previously colonised
Secondary: change in structure and species of a community over time in an area that has been previously colonised
—> starts from soil
—> previous community wiped out naturally ie fire

71
Q

What is meant by the pioneer species?

A
  • the first organisms to colonise a barren area
    —> able to withstand harsh conditions
    —> release minerals to form primitive soil (humus)
72
Q

What happens to biodiversity and plant diversity at the end of succession?

A

Biodiversity increases
Plant diversity decreases

73
Q

Features of a climax community

A
  • equilibrium between GPP and respiration
  • equilibrium of energy incorporated from sunlight and energy released by decomposition
  • equilibrium in uptake of nutrients from soil and their return to decay
  • humus is constant
74
Q

Factors affecting succession

A
  • immigration of new species
  • interspecific and intraspecific competition
  • facilitation/symbiosis
    —> mutualism
    —> commensualism
75
Q

How could deforestation lead to a decrease in the conc of CO2?

A

Less respiration by plants

76
Q

Why does a food chain usually sustain no more than 6 energy transfers?

A
  • insufficient energy to support further trophic levels
  • energy lost through metabolic heat when organisms are consumed by others
  • fewer trophic levels = more energy available for humans
77
Q

Why do warm-blooded organisms have to eat more than cold-blooded?

A
  • maintain higher body temp
  • more food needed in respiration to produce heat
78
Q

How could farmers increase nitrogen levels in soil?

A
  • plant leguminous plants
    —> contain nitrogen fixing bacteria which convert N2 to NH4+
79
Q

What effect does an increase in temp have on the NPP?

A
  • decrease
  • more carbs broken down in R than produced in P
80
Q

How can dentrification be reduced?

A
  • ploughing fields
  • enhance aerobic conditions
  • denitrifying bacteria need anaerobic
81
Q

Conditions for nitrification and dentrification

A
  • aerobic
  • anaerobic
82
Q

Conditions for nitrification and dentrification

A
  • aerobic
  • anaerobic
83
Q

Distinguish between GPP and NPP

A

GPP: total energy fixed by plant

NPP = GPP - R

84
Q

Why is keeping cattle less efficient than growing crops?

A
  • energy lost in transfer to next trophic levels
    —> plant eaten by cow
  • energy lost in respiration of herbivores
85
Q

Why can growing sugar cane to produce biofuels be considered carbon neutral?

A
  • burning biofuels increases CO2
  • photosynthesis whilst growing decreases CO2
86
Q

Describe a difference in the growth phases in humans and yeast cells

A
  • yeast don’t have stationary phase or a death phase
87
Q

Explain why farmers apply fertiliser to soil after harvesting

A
  • crops absorb nitrate
  • less decay
  • less nitrifcstion
88
Q

Explain why trees are unable to survive in waterlogged soil

A
  • decreases aerobic conditions which stops aerobic respiration
  • nitrates can’t be taken up by tree roots as no active transport for mineral uptake
89
Q

Suggest why insectivorous plants rely on catching prey

A
  • nitrates are in low supply
  • lots of ATP is required both to fix nitrogen and for uptake of minerals by active transport
  • more energy efficient to digest insects than to fix nitrates

A2 BIO UNIT3 (8 decks)

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