3.5 a 4.2 Flashcards
(101 cards)
1
Q
Factors which control population size
A
Birth rate, death rate, immigration, emigration
2
Q
Strategies used for population growth by FUGITIVE species
A
Poor at competition so rely on large capacity for reproduction. Invade new environment rapidly e.g. algae colonising bare rock.
3
Q
Strategies used for population growth by EQUILIBRIUM species
A
Control population by competition in stable environment e.g. bacteria put into fresh nutrient solution or when rabbits newly introduced to island.
4
Q
What is the lag phase
A
Period of adaptation or preparation for growth with rehydration or metabolic activity.
5
Q
What is the lag phase in sexually reproducing organisms?
A
The time taken to reach sexual maturity and age
6
Q
What is the exponential phase
A
As numbers increase if no limiting factors, more individuals are available for reproduction.
7
Q
Why can’t the exponential phase be maintained
A
Environmental resistance: less food, waste products reach toxic levels, less habitats.
Biotic factors like parasitism, predation.
Abiotic factors: temperature, light intensity.
8
Q
What is the stationary phase?
A
Birth rate = death rate. Population is at max size at the carrying capacity.
9
Q
What is the death phase?
A
Factors that slow population growth at the log phase become more significant. Population size decreases until death rate greater than birth rate.
10
Q
What does a predator-prey relationship do?
A
Causes both populations to oscillate which are regulated by negative feedback
11
Q
What is a population crash
A
A sudden dramatic decrease in population number when the population succeeds the carrying capactiy.
12
Q
Growth curve for more complex organisms (the formula)
A
(births+immigration) - (death+emigration)
13
Q
Factors that regulate population increase
A
Density dependent and independent factors
14
Q
What are density dependent factors
A
More effect if the population in an area is larger because they affect a greater proportion if the population is denser. BIOTIC like parasitism, disease, no food.
15
Q
What are density independent factors
A
ABIOTIC factors e.g. floods. Don’t depend on population density. Effect is the same regardless of population size
16
Q
What happens if population rises above set point?
A
Density dependent factor increases mortality or reduces breeding.
17
Q
What happens if population falls below set point?
A
Environmental resistance is temporarily relieved,
18
Q
What is abundance?
A
Number of individuals of the same species in a given area or volume.
19
Q
How is animal abundance assessed?
A
-Capture-mark-recapture experiments with Lincoln Index Calculation.
- kick sampling in a stream to count aquatic invertebrates.
20
Q
How is plant abundance assessed?
A
- Random sampling using a quadrat to find mean or density.
- Systematic sampling with transect to determine changes in percentage cover of a plant
21
Q
Capture-mark-recapture formula
A
Sample 1 x sample 2 / how many marked in sample 2
22
Q
Assumptions made with capure-mark-recapture
A
- Assuming sample tag doesn’t confer a disadvantage.
- Assume when reintroduced they mix randomly.
- No predation or migration.
23
Q
What is the distribution of a species
A
describes area or volume in which it’s found
24
Q
What does it mean if a habitat is uniform?
A
The positions of the outermost plants can be marked on a map and the area they surround can be measured.
25
What do kite maps show
Show the abundance and distribution of species along a transect - show percentage area cover
26
What is an ecosystem
A characteristic community of interdependent species and their habitat. Comprised of biotic and abiotic elements.
27
Why are ecosystems dynamic (subject to change)
Because of energy transfer, species competition and population size, succession, and biological cycles.
28
What is ecological energetics
The study of the flow of energy through the ecosystem
29
What are producers?
Autotrophs like green plants which absorb light energy and manufacture complex organic molecules from simple inorganic raw materials by photosynthesis.
30
What are consumers?
Organisms which can't produce their own complex organic materials so must eat them
31
What are herbivores?
Primary consumers. Animals which feed on plants/producers
32
What are carnivores?
Animals which feed on other animals
33
What is a trophic level?
An organism's position in a food chain or its feeding level
34
How does energy pass through trophic levels?
Energy passes from the producers at trophic level 1 to herbivores at level 2, then on to carnivores at trophic levels 3 to 5. Energy leaves the system as heat
35
Why is there a large loss of energy at each level as its passed along the food chain
Because energy is lost through respiration and excretion of waste products.
36
What is a food chain
The sequence of energy transfers from plant to herbivore to carnivore
37
What are detritivores
Organisms which feed on dead remains and waste like woodlice, maggots and earthworms
38
How do detritivores work?
Feed on remains and release energy trapped in the organic compounds of body tissues (proteins and fats). By feeding, digesting and excreting, the detritivores break up the organisms into tiny pieces which increases S.A
39
What are decomposers
Bacteria and fungi which complete the organic breakdown process which releases essential nutrients back into the soil.
40
What is a niche
Job/role of an organism within a habitat
41
What is a population
A group of organisms of a single species interbreeding and occupying a particular area or habitat
42
Why is a food chain limited to 4-5 trophic levels
Because when reaching the apex predator at 4/5 there's o energy left for another trophic level
43
What factors is the length of a food chain dependent on?
- The more energy that enters at trophic level 1. Tropical food chains are longer as there's more light for photosynthesis.
- If energy transfer is more efficient between trophic levels the food chain is longer.
44
What is photosynthetic efficiency?
Measure of how well a plant converts light energy to chemical energy.
45
Why does around 60% of the light energy that falls on a plant may not be absorbed by photosynthetic pigments?
- Wrong wavelength.
- Reflected.
- Transmitted straight through the leaf.
46
What is Gross Primary Productivity (GPP)
The rate of production of chemical energy in organic molecules by photosynthesis in a given area, in a given time. (KJ m-2 y-1)
47
How is the most substantial portion of GPP released
by the respiration of the plant to fuel, e.g. protein synthesis
48
What is Net primary productivity?
The remains of GPP after respiration. GPP-respiration=NPP
49
What is primary productivity?
The rate at which producers convert energy into biomass
50
What is secondary productivity
The rate at which heterotrophs accumulate energy in the form of new cells and tissues.
51
In which organisms does secondary production occur
Heterotrophs like animals, fungi, some bacteria, and some Protoctista.
52
Why must heterotrophs inject or absorb organic carbon from other organisms
They can't fix carbon from inorganic sources like the producers do.
53
Why do herbivores have a lower secondary productivity than carnivores
Carnivores more efficient at energy conversion than herbivores as their diet is protein rich and easily digested.
54
What is interspecific competition
Two DIFFERENT species competing for the same resource/food.
55
Why does P. Aurelia have a competitive advantage compared to P. Caudatum
P. Aurelia is smaller and multiplies faster
56
What happens to P. Caudatum as P. Aurelia has a competitive advantages
As P. Aurelia density increases then levels off, the P Caudatim population density decreases and eventually dies out competely
57
What is the Competitive Exclusion Principle
States that when two species occur in same habitat, one will outcompete the other since two species can't occupy the same niche
58
What does the base of the ecological pyramid represent
Primary producer at trophic level 1
59
What does the apex of the ecological pyramid represent
The consumer at the end of the food chain
60
Disadvantages of pyramids of numbers
-Don't take into account the size of the organisms and as a result are often inverted.
-Provide no information about amount of energy present at each trophic level
61
What is biomass
The mass of biological tissue
62
Why is biomass difficult to measure accurately
Rots may be difficult to harvest and not all biomass is available to the next trophic level (bones and beaks have mass but not eaten)
63
What does a pyramid of energy show
The quantity of energy transferred from one trophic level to the next per unit area or volume, per unit time
64
Why won't pyramids of energy ever be inverted
As energy is lost due to heat from respiration and excretion, so as you move from the base to apex each block will be smaller than one below
65
What do pyramids of energy allow
Allow comparison of the efficiency of energy transfer between trophic levels in different communities
66
What is succession
A sequence of changes in community structure and species over time. New species invade and replace existing ones until a stable community is formed
67
What is a climax community
A stable community from succession
68
Where does primary succession begin
Begins from bare rock or site of volcanic eruptions
69
What are the first organisms to colonise the rock (primary succession)
Pioneer species
70
Steps of primary succession
1. Pioneer species change rock surface by penetrating it which allows humus to accumulate and grasses and ferns to colonise area.
2. Grasses and ferns further change the rock surface as their roots penetrate further.
3. Death and decay over generations allows more soil to accumulate and higher plant species invade.
4. Plants become more diverse so other organisms take advantage of new habitat and food.
71
Where does secondary succession begin
Begins from bare soil usually after wildfire
72
Why is secondary succession quicker in achieving a climax community faster
As the soil is already present and may contain viable bulbs, seeds, and spores
73
How does human activity prevent a climax community being achieved
- Grazing sheep.
- Farming of land.
- Deforestation and soil erosion.
74
Why is carbon a key atom
An essential component of biological molecules like proteins, carbohydrates, lipids and nucleic acids.
75
What is symbiosis
The association between individuals of two species.
76
How does facilitation help an ecological community
- Provides better resource availability and refuge from physical stress, predation and competition
77
What is mutualism
An interaction between two species which is beneficial for both
78
What is commensalism
A loose interaction between organisms of two species in which one benefits and another is unaffected
79
Steps of carbon cycle
1. CO2 from atmosphere fixed into carbohydrate by the light independent stage.
2. Respiration in plants and animals releases CO2 into the atmosphere due to the action of decarboxylase in the link reaction and krebs cycle.
3. Combustion of fossil fuels releases carbon in CO2.
4. Decomposers release CO2 into the atmosphere due to respiration.
5. Carbon fixed into organic molecules by producers pass from trophic levels along food chains during feeding.
6. Fossil fuels are formed from the remains of dead plants and animals.
80
How is human activity disruption the balance of carbon cycle
-Deforestation so less carbon.
-Burning fossil fuels so more carbon.
-Increase in decomposition so more carbon.
81
What is a carbon footprint
The total amount of CO2 produced directly due to actions of something.
82
How does agriculture have a carbon footprint
- Production of farm tools, insecticides, fertilisers, fungicides.
- Farm machinery powered by fossil fuels.
- Transport of produce
83
Why is nitrogen an essential atom
Component part of nucleotides (ATP, DNA, RNA) and amino acids, and found in chlorophyll.
84
What is the nitrogen cycle
The flow of inorganic and organic nitrogen within the abiotic and biotic elements of an ecosystem.
85
How is nitrogen passed along food chains
Plant roots absorb nitrogen as inorganic ammonium or nitrate ions (by active transport). The nitrogen then incorporated into the plants biological molecules and passed along food chains.
86
What is nitrogen fixing
Fixing atmospheric nitrogen gas into ammonia and ammonium ions
87
What is nitrification
Concerting the products of decay (ammonium ions) into nitrate ions.
88
What bacteria fixes atmospheric nitrogen into soluble inorganic compounds
- Azotobacter
- Rhizobium
89
Where is Azotobacter found and what does it do?
Free living bacterium in soil. Aerobic and fixes N gas into ammonium ions.
90
Where is Rhizobium found and what does it do?
- Found in root nodules of legumes and shares a symbiotic relationship with them.
- Uses enzyme nitrogenase to fix N gas into ammonium.
91
How do the root nodules help rhizobium work
Nitrogenase activity inhibited by oxygen so root nodules surround the bacteria with a layer of leghaemoglobin which combines with oxygen to prevent it reaching the anaerobic rhizobium bacteria
92
What kind of symbiotic relationship does the Rhizobium and root nodules of legumes have?
Ammonium fixed by Rhizobium is absorbed by the plant roots and in return the legumes share the products of photosynthesis with the rhizobium.
93
What microorganisms convert ammonium into nitrite then nitrate by NITRIFICATION
- Nitrosomonas convert ammonium to nitrite.
- Nitrobacter convert nitrite into nitrate which is then absorbed into plant root hair cells by active transport
94
What is denitrification
the loss of soluble nitrate compounds from the soil.
95
What happens when nitrate is converted back into atmospheric nitrogen and lost from soil under anaerobic conditions
Decreases soil fertility
96
How do farmers try to avoid decreasing soil fertility
By ploughing their fields - by mixing the soil with air as the oxygen from the air inhibits the pseudomonas (denitrifying bacteria) and encourages the growth of Nitrobacter and azotobacter
97
Steps of nitrogen cycle
1. Decomposers break down large organic molecules in the plant remains into inorganic ammonium (putrefaction/decay).
2. Nitrosomonas convert ammonia into nitrite, then Nitrobacter converts nitrite into nitrates (nitrification).
3. Inorganic nitrogen sources are converted into nitrogen gas by pseudomonas (denitrification)
4. Azotobacter and rhizobium fix free N gas into ammonium and nitrates (nitrogen fixing).
5. Nitrates absorbed by root hair cells by active transport which requires ATP from cell and has high oxygen demand
98
How can human activity improve the availability of soluble nitrate and therefore soil fertility
- Add chemical fertilisers.
- Add manure.
- Adding treated sewage.
- Planting legumes like clover.
- Ploughing or draining to improve aeration.
99
How can human activity cause nitrogen pollution and reduce biodiversity?
- Excess nitrates on grassland leads to increased growth of weeds which decreases biodiversity due to competition for resources.
- Draining wetlands destroys unique habitats
100
What is eutrophication
Process where water body becomes overly enriches with things like chemical fertilisers, manure and slurry.
101
What does eutrophication cause
- Increase in soluble nitrate content of the water so increases algal and plant growth.
- Algal bloom may form which blocks light at lower depths preventing photosynthesis.
- Aerobic bacteria decompose dead plants and algae and as they multiply, the dissolved oxygen conc of water drops killing other organisms.
- Water anaerobic which encourages denitrifying bacterial growth so nitrate levels fall.
