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Wjec A Level Biology > 3.5 Population Size And Ecosystems > Flashcards

3.5 Population Size And Ecosystems Flashcards

1
Q

Ecology

A

The study of living things and their interactions with each other and their environment

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2
Q

Ecosystem

A

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

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3
Q

Population

A

All the members of one species in an area

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4
Q

Habitat

A

The place in an ecosystem where an organism lives

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5
Q

Niche

A

The role of an organism in an ecosystem, generally a feeding role

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6
Q

Biotic

A

All the living and organic component of an ecosystem

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7
Q

Abiotic

A

All the non-living parts of an ecosystem

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8
Q

Is an ecosystem static

A

No
Ut is dynamic

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9
Q

What is the source of energy for an ecosystem

A

The sun

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10
Q

How does the sun being the source of energy for an ecosystem mean an ecosystem is subject to change

A

The duration and intensity of sunlight changes which effects the energy flow

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11
Q

What does population size depend on

A

Reproduction rate
Death rate
Immigration rate
Emigration rate

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12
Q

Population size will increase when

A

Reproduction and immigration rates are higher than death and emigration rates

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13
Q

Population size will decrease when

A

Reproduction and immigration rates are less than death and emigration rates

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14
Q

lag phase of animal growth curve

A

Animals first arrives in an area
Population increases slowly
Time is needed for enough individuals to reach sexual maturity

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15
Q

Log phase of animal growth curve

A

Plenty of food
Population increases exponentially
Competition for food, territory and habitats are low

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16
Q

Stationary phase of animal growth curve

A

Carrying capacity is reached
Numbers will fluctuate around this in response to environmental changes such as predator-prey negative feedback.
If an overshoot occurs when growth exceeds carrying capacity there may be a degraded carrying capacity due to resource destruction

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17
Q

What are density dependent factors

A

Biotic factors such as competition, predation and disease
The effect of the factor is bigger when the population is higher

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18
Q

What are density independent factors

A

Abiotic factors eg light intensity, temperature, wildfires
Effects the population whether it is large, small or just the same

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19
Q

Why does sampling need to be random

A

Each individual has an equal chance of being included
It ensures the sample is representative of the whole population of each species
It reduces subjectivity and removes bias

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20
Q

Examples of ecosystems

A

Tropical rainforest
Tundra
Desert

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21
Q

What is the first energy transfer in an ecosystem

A

From sunlight to plants

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22
Q

Why is not all of the light hitting the leaf used in photosynthesis

A

• some is reflected by the waxy cuticle
• some is of the wrong wavelength to be absorbed
• some is transmitted through the leaf as it doesn’t hit a chloroplast

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23
Q

What are producers

A

Autotrophic organisms at the start of a food chain that convert light energy into chemical energy

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24
Q

Why is less than 10% of energy incorporated into biomass and is available to the next trophic level

A

Most energy is released in respiration and incorporated into other molecules or into electrochemical gradients

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25
What are trophic levels
The feeding level within a food chain and shows the number of times that energy has been transferred to successive organisms along a food chain
26
What is biomass
The mass of biological material in living or recently living organisms
27
What are primary consumers
Herbivores They feed on producers
28
What are secondary and tertiary consumers
Include carnivores Feed on trophic levels below Some feed at more than 1 trophic levels
29
What kind of organisms does decomposition involve
Detritivores and decomposera
30
Detritivores
Earth worms and woodlice They feed on detritus
31
What is detritus
Remnants of dead organisms and leaves
32
Decomposers
Bacteria and fungi Feed via external digestion Complete process started by detrivores
33
What trophic level do decomposers feed on
All
34
How to calculate photosynthetic efficiency?
Quantify of light energy fixed by plants/Quantity of light energy falling on plant X 100
35
What is Gross primary production
Rate of production of chemical energy in organic molecules by photosynthesis in a given area, in a given time Unit = kJm-2y-1
36
What is net primary production
Energy in the plant's biomass which is available to primary consumers Units= kJm-2y-1
37
How to calculate NPP
NPP= GPP-R
38
Why is the true value of biomass even lower than predicted
Some of the biomass is used to form inedible materials such as bark or its biomass in roots which is out of reach of primary consumers
39
What kind of NPP does a tropical rainforests have?
High Plentiful rainfall, high light intensity and high temperatures
40
What kind of NPP does a tundra have and why?
Low Cold, low light intensity
41
How to calculate % efficiency
Energy fixed as biomass/energy available to next trophic level X 100
42
Pyramid of numbers
Easy to construct Shows the energy flow through a food chain Doesn't consider the size of the organisms
43
Pyramid of biomass
More accurate than pyramid of numbers Is difficult to measure and calculate May be inverted
44
Pyramid of energy
• most accurate way of representing feeding relationships • shows the energy flow through an ecosystem • Shows clearly the energy lost at each level • is difficult to calculate
45
What can pyramids not show
Organisms operating at several trophic levels
46
What is succession
Change in structure and species composition of a community over time
47
What is a seral stage
Each stage in succession where different communities dominate
48
What is primary succession
Organisms invade spaces that did not previously support life
49
What is secondary succession
The reintroduction of organisms into a habitat previously occupied by plants/animals
50
Surface of primary and secondary succession
Primary - bare surface Secondary - soil
51
What are the pioneer species of primary and secondary succession?
Primary - mosses and lichens Secondary - small weedy plants
52
What is pioneer species?
The first species to colonise a new area in an ecological succession
53
What is a climax community
A stable community that undergoes no further change
54
What is a sere
Entire sequence of communities that changes successively in a given area
55
What changes as succession progresses
• soil depth increases • nutrient content increases • humus content increases • water content increases • diversity increases • stability increases
56
What is it called when a climax community is not reached and what would cause this
Deflected or disclimax Human intervention eg Monoculture and grazing
57
Interspecific competition
Different species
58
Intraspecific competition
Same species
59
Term for species that exist in a relationship that is beneficial to both
Mutualism
60
Term for when a species is able to obtain benefit from one species whilst other is unaffected
Commensalism
61
What does the carbon cycle involve
Photosynthesis Respiration Combustion of fossil fuels
62
Effect of photosynthesis on carbon cycle
Photo autotrophs remove CO2 from the atmosphere and fix it into organic molecules
63
Effect of respiration on carbon cycle
Done by all organisms Returns CO2 to the atmosphere
64
Effect of combustion of fossil fuels on carbon cycle
• fossil fuels formed millions of years ago and derived from partially decayed remains of plants • combustion releases CO2 into the atmosphere
65
Human activities that affect the carbon cycle
Deforestation and combustion
66
What is deforestation
Removal of trees and subsequent use of land for another purpose
67
Effect of deforestation on carbon cycle
Significantly reduces the volume of CO2 removed from the atmosphere through photosynthesis
68
How does increased atmospheric CO2 leads to global warming
CO2 is a greenhouse gas so it re-radiates infra-red back towards the Earth's surface rather than allowing it to escape to space Increase in CO2 emissions over recent decades are leading to an enhanced greenhouse effect
69
What is the effect of global warming on species?
• global temperatures rise so polar ice melts so sea levels rise and coastal flooding occurs • increases incidence of forest fires leading to desertification • changes to climate patterns, temperature, wind patterns, rainfall, extreme weather conditions • acidification of oceans due to increasing dissolved CO2 Species may not be able to adapt or migrate and many will become extinct
70
What is desertification
The process by which fertile land becomes desert as it loses water, vegetation and wildlife
71
Effect of acidification of ocean on fish and crustaceans
Fish - gills produce mucus and so reduces gas exchange Crustaceans - lose CaCO3 from exoskeletons as it is soluble in acid
72
Effect of global warming on farming
• decreased crop yields and failed harvests
73
How to fix farming practices to help global warming
Use drought-tolerant crops
74
Why is farming having a negative effect on global warming?
Although it removes CO2 through photosynthesis energy is needed for • insecticides and fertilisers • powering farming machinery • transport of produce to market
75
What is carbon footprint
The total amount of CO2 attributable to the actions of an individual or a product or service over a period of one year
76
Effect of the 3Rs to reduce carbon footprint
Reduces energy consumption and so reduces carbon footprint
77
What is the nitrogen cycle
Flow of organic and inorganic nitrogen withon the abiotic and biotic components of an ecosystem where there is an interchange between certain nitrogenous compounds and atmospheric nitrogen
78
In what form do plants uptake nitrogen by plant roots
Ammonium and nitrate ions
79
What are the 4 main processes of nitrogen cycle
Nitrification Deniftrification Putrefaction Nitrogen fixation
80
Others words for ammonification
Putrefaction Decomposition Mineralisation
81
What happens during ammonification
• Decomposers feed on dead and organic matter and feaces saprophytically by secreting enzymes onto their food and absorbing small soluble products • proteases hydrolyse proteins to amino acids and deaminase reduce the amino group to ammonium ions
82
What happens during nitrification
• addition of nitrogen to the soil most commonly as nitrite and nitrate ions • ammonium is oxidised into nitrite by nitrosomonas bacteria • nitrite oxidised to nitrate by nitrobacter conditions • aerobic conditions required
83
Simply what happens in nitrification
NH4+ ---> NO2- ---> NO3-
84
What bacteria is used when ammonium is oxidised to nitrite
Nitrosomonas
85
What bacteria is used when nitrite is oxidised to nitrate
Nitrobacter
86
What is nitrogen fixation
The reduction of nitrogen atoms in nitrogen molecules to ammonium ions by prokaryotic organisms It is carried out by nitrogen fixing bacteria such as azotobacter and rhizobium
87
Azotobacter
Nitrogen fixing bacteria Free living in soul Accounts for most nitrogen fixation
88
Rhizobium
• mutualistic bacterium found in root nodules of leguminous plants • invades the roots of the legumes and the plant responds by forming a nodule where the bacteria will live • nitrogen gas diffuses into the nodule where nitrogenase enzyme produced by the bacteria redcluces N2 to ammonium ions in anaerobic conditions • the ammonium ions are converted to organic acids and amino acids for the bacteria • excess ammonium and amino acids are exported to the plant through the phloem for protein synthesis • this requires ATP
89
How are anaerobic conditions maintained for Rhizobium
The plant provides this by producing the pigment leghemoglobin which takes up oxygen in the root nodule, removing it from the bacterial environment
90
How does Rhizobium get ATP
Gains sugars from the plants photosynthetic product
91
What is denitrification
Loss of nitrate from the soul by anaerobic bacteria, Pseudomonas, to atmospheric nitrogen The denitrifying bacteria use the nitrate to provide oxygen for respiration and the remaining nitrogen atoms are converted into nitrogen gas
92
Simply, what happens during denitrification
Nitrate ---> nitrogen gas
93
How does ploughing and draining soil increase soil aeration
• allows air to reach the roots of plants as nitrates and other minerals are uptaken by active transport which requires ATP from aerobic respiration • favours the aerobic process of nitrogen fixation and nitrification • inhibits denitrification which is anaerobic
94
Effect of using excess fertilisers
• eutrophication occurs where the excess fertilisers runs off into aquatic habitats which increases the ion content of the water and forms an algal bloom • algal blooms block light to aquatic plants so plants and algae die and form detritus which is aerobically decompose which causes other aerobic organisms to die and further add to the detritus • eventually all the oxygen is used up and only anaerobic bacteria can survive - these release ammonia, methane, hydrogen sulphide into the water which causes a toxic environment for most organisms
95
How can farmers reduce fertiliser run-off
• apply fertilisers when plants are actively grow • not apply fertilisers within 10m of water courses • dig drainage ditches to collect run off
96
Pros and cons of draining land
• the soil doesn't get water logged so denitrification slows down and more oxygen means nitrification is sped up so more nitrate is added to the soil and more decomposition occurs • it means the loss of habitat and biodiversity for some wet-land ecosystems • plant rich habitats are more subject to wild-fires which release locked in carbon

Wjec A Level Biology (13 decks)

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