Ecosystems

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What is an ecosystem? What two types of factor affect ecosystems?
An ecosystem is made-up of all the living organisms that interact with one another in a defined area, and also physical factors present in the region. The two types of factor are biotic/living factors biotic/ non-living
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Give examples of biotic abiotic factors
Biotic: organisms present, competition (e.g. for food space and territory). Abiotic: light, temperature, water availability, oxygen availability and EDAPHIC (soil factors).
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Explain how the abiotic factor light may affect an ecosystem.
Light: needed for photosynthesis (generally higher intensity= more photosynthesis)-plants = developed to cope with low light= have larger leaves/ photosynthetic pigments which require less light/ reproductive systems only operating at optimum light.
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Explain how the abiotic factor temperature may affect an ecosystem. Explain why this affects endotherms to a lesser degree.
Effects enzymes controlling metabolic reactions- plans + ectotherms = grow faster if temperature is higher as enzymes can work faster (endotherms= control internal body temperature= less effected) . Also cause migration/ hibernation/ dormancy...
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Explain how the abiotic factor water availability may affect an ecosystem.
All animals and plants need water, lack of= water stress, severe= death. Plants= wilt (water= needed for turgor to maintain hydrostatic skeleton). Needed for photosynthesis.
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Explain how the abiotic factor oxygen availability may affect an ecosystem.
Esp. needed in aquatic ecosystems. Need fast-flowing cold water= high levels of oxygen. If water= too warm/ slow= less O2 = suffocation of aquatic organisms. E.g. waterlogged soil, airspaces= filled with water= less 02 for plants
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Explain how the abiotic factor edaphic (soil) factors may affect an ecosystem. What are the 3 types of soil particle and what is their composition.
Different types of soil= different particle sizes= effects the organisms which can survive there.Clay= fine, easily waterlogged, clumps when wet. Loam= different sized particles, retains water but NOT waterlogged. Sandy= coarse, free-draining, eroded
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What is the ultimate source of energy?
The sun.
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Why is the sun the ultimate source if energy?
Light energy from the sun is transferred into stored chemical energy in photosynthetic organisms.
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What is each stage in a food chain referred to as? What are the first 4 of these? What in this chain break down dead organism and recycle's nutrients?
A trophic level. Producer (light > chemical energy by photosynthesis), primary consumer, secondary consumer and tertiary consumer. Decomposers.
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Why is there rarely more than 5 trophic levels?
Not enough biomass or energy to support further organisms.
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What is biomass? Why is it important in food chains and how do we know this?
The mass of living material present in a particular place/ in particular organisms . Important in food chains= can be equated to energy content because the biomass consists of cells, tissues, carbohydrates, carbon compounds which= store of energy.
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How do you know how much biomass is present in an organism? How do you calculate biomass at a trophic level?
Measure the mass of fresh material present discounting water content- kill organism, place in oven at degrees until all water is evaporated ( no change in mass) = THE DRY MASS. Multiply biomass x no. of organisms in that trophic level
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What is biomass measured in (land and water)?
gm^-2 (land) gm^-3 (water)
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What is energy at each trophic level measured in? What is the reason for it being given this long a period?
KJ m^-2 yr^-1. Allows for changes in photosynthetic production and consumer breeding patterns.
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What is the efficiency of biomass of energy transfer called?
Ecological efficiency
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Producers can only convert 1-3% of sunlight into chemical energy and therefore biomass, why is this?
Not all solar energy is used for photosynthesis- 90%= reflected, some = transmitted through leaf + some= unusable wavelength. Other limiting factors may occur regarding photosynthesis e.g. water. Portion of energy= lost for photosynthetic reactions.
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What is the total energy plants convert to organic matter called? And what is the energy available to the next trophic level called?
Gross production and net production.
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What is the equation for net production for plants?
Net production = gross production- respiratory losses
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What is the equation for net production in consumers?
Net production= gross production- respiratory losses
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At most, what percentage of biomass in their food to consumers convert to their own organic tissue?
At most 10%
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Why is at most X% of food converted to own organic matter in each trophic level?
Not all biomass is consumed (e.g. bones + roots), energy= lost as metabolic heat due to movement/ respiration. Some parts= indigestible= excreted as faeces. Energy= lost in excretory materials e.g. urine.
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What is the formula for ecological efficiency (biomass transferred to next trophic level)?
(energy or biomass available after transfer/ biomass or energy available before transfer) x100
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Give reasons why human activities can manipulate biomass through ecosystems.
E.g. in agriculture- plants= given optimum abiotic factors (minimises limiting factors). Animals- competition= removed + predators. Agriculture= simple food chains with minimal trophic levels= more energy as biomass transferred to humans.
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What is decomposition?
A chemical process in which a compound is broken down into smaller molecules or its constituent elements.
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What is a decomposer?
An organism thats feeds on and breaks down dead plant or animal matter, turning organic matter into inorganic matter available to photosynthetic producers.
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Give examples of decomposers.
Microscopic fungi, bacteria, larger fungi (toadstools)
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What kind of feeder are decomposers?
SAPROTROPHS- they obtain energy from dead waste or inorganic material (saprobiotic nutrition).
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How do decomposers digest their food?
Externally by secreting enzymes which breaker down large, complex molecules into smaller ones
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Other than decomposers name another type of organism involved in decomposition and how these help. Give an example of one of these.
Detritivores feed on detritus, these break decaying/ material into smaller pieces increasing the surface area for decomposers to work on. Woodlice/ earthworms (internal digestion).
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What percentage of the air is Nitrogen?
78%
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Can nitrogen in the air be used by plants?
No, it needs to be combined with other elements such as oxygen and hydrogen to be usable.
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What type of organism helps turn Nitrogen into a usable form, preventing it from becoming a limiting factor in ecosystems?
Bateria
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Nitrogen fixation is the process by which Nitrogen (N2) is combined with hydrogen (H2) to form ammonia NH3 which can be used by plants. What 2 types of bacteria are involved in this, where are they found and what enzyme is used?
Azotobacter (free-living in soil), Rhizobium (root nodules-growths on roots of legumous plants) and nitrogenase.
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Why do the bacteria and plant have a SYMBIOTIC MUTUALISTIC RELATIONSHIP (both gaining)?
Plant gains amino acids from Rhizobium produced in nitrogen fixation of N2 to NH3. Bacteria gain carbohydrates from photosynthesis= energy source for the bacteria.
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What is nitrification?
The process by which ammonium compounds in the soil= converted into nitrogen-containing molecules which can be used by plants. Free-living bacteria in the soil are used (nitrifying bacteria)
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What type of reaction is nitrification? What are the steps?
Nitrification is an oxidation reaction. 1.Nitrifying bacteria (Nitrosomonas) oxidised ammonium compounds to nitrites (NO2-) 2. Nitrobacter oxidises nitrites to nitrates (NO3-).
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Why is nitrification beneficial to the plant?
Because the nitrates (NO3-) produced are highly soluble and is therefore nitrogen in the form where the greatest amount will enter the plant.
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What is denitrification?
The process by which denitrifying bacteria convert nitrates in the soil back into N2 gas (removing O2). This is because bacteria use nitrates as a source of energy for respiration and so N2 is released- only happens in ANAEROBIC conditions
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What is ammonification?
Name given to the process by which decomposers convert nitrogen- containing molecules in dead organisms, faeces and urine into ammonium compounds.
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Name the 4 processes involved in the nitrogen cycle.
NITROGEN FIXATION, NITRIFICATION, DENITRIFICATION AND AMMONIFICATION.
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Draw the Nitrogen cycle.
In books, page 618 if stuck.
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What percentage of the atmosphere to carbon dioxide make up?
0.04%
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What causes atmospheric carbon dioxide levels to fluctuate? When are they at their highest?
Photosynthesis causes CO2 levels to fluctuate as plants photosynthesise most during the day removing CO2 from the atmosphere. However, respiration causes vitally no fluctuation as it is constant night and do. C02 levels are highest at night in winter
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Main reasons for increasing levels of atmospheric carbon dioxide.
Combustion of fossil fuels- releasing CO2 trapped for millions of years below earths surface. Deforestation- removed large quantities of photosynthesising biomass.Therefore, less CO2= removed + when trees are burnt= produces CO2.
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Why is CO2 called a greenhouse gas?
Causes thermal heat top become trapped in earths atmosphere.
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How does increasing temperature affect the levels of CO2? What kind of feedback is this?
Temperature increases, the less CO2 gas is dissolved in the sea, reducing this carbon bank= more in atmosphere ( a positive feedback loop)
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How can scientists see how CO2 levels have changed over time?
Looking in glaciers, certain depths of glaciers correspond to a time period i.e. deeper= older. When ice forms air bubbles are created, therefore analysis of these air bubbles reflect the composition of the air at the time.
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Define succession.
The PROGRESSIVE REPLACEMENT of one dominant type of species or a community by another until a stable climax is reached.
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Succession is a process which occurs due to environmental changes. What are the two types of succession.
Primary succession (slow)- an area of land that has been newly exposed e.g. rock. No soil or organic material present. Secondary succession (rapid) where soil. is present but there are no animal or plant species e.g. after a forest fire.
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Give examples of when primary succession may occur.
Volcanoes erupt depositing lava- lava cools and solidifies= igneous rock, sand is blown creating new sand dunes, silt and mud are deposited in river estuaries, glaciers retreat depositing rubble and exposing rock.
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What are the stages of succession and what are these collectively known as?
Each stage is called a seral stage- pioneer community (e.g.lichen) , intermediate community (mosses, grasses, small shrubs and trees)and climax community(e.g.woodland).
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How do pioneer species get to the barren location. Give an example of a pioneer species (first colonisation in primary succession)
Species arrive as spores or seeds carried in the wind/ sometimes by bird droppings.
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What are the general adaptations of pioneer species.
Produce large quantities of seeds/spores. Seeds that germinate rapidly. Photosynthesise to produce their own energy (light, rainfall and air/CO2 only abiotic present). Tolerance-extreme environments. Ability to fix nitrogen= adds to minerals in soil.
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Notes on intermediate community.
Pioneer species die= organic products released into the soil= HUMUS. Soil can now support secondary colonisers, as it contains nitrates + can hold water. Mosses= 2ndary colonisers arriving as spores/seeds. Pioneer species= food for consumers= animal
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Notes on intermediate community continued.
Environmental conditions improve, new species arrive (tertiary colonisers). Waxy cuticles= help with water loss. More rock eroded= mass of organic matter increases. Organisms decompose= deeper, ^nutrient soil.
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Notes on intermediate community continued 2.
At each seral stage= some organisms better adapted to current ecosystem conditions.
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Notes on climax community.
Final seral stage. Community is in a stable state (will show little change over time). Few dominant plant and animal species. Animals which make up climax species= dependent on climate e.g. lots of water= trees.
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Notes on climax community continued.
Biodiversity= initially increases with succession, when it reaches climax=decreases. Biodiversity decreases as dominant species out-compete pioneer species.
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Is animal succession slower or faster than plant succession? Explain why.
Animal succession= slower, animals have to travel from neighbouring areas. Primary consumers e.g. worms will feed on the lichen so these need to be established first. Also harder for animals to reach if area of land has been geographically isolated
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What is it called when humans inhibit the natural flow of succession and prevent the community reaching a climax?
Deflected succession
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When succession is stopped artificially what is the final stage formed known as?
PLAGIOCLIMAX
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Agriculture is on of the main reasons why a PLAGIOCLIMAX may be reached. Explain.
Grazing + trampling of animals= large areas of remaining grassland. Removing vegetation for monoculture. Burning for forest clearance= leads eventually to an increase in biodiversity as nutrient-rich ash= allows other species to grow.
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How can deflected succession be useful?
It can be used for conservation, helping maintain the species currently in the area.
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What is meant by distribution of organisms?
Where individual organisms are found within an ecosystem. (Organisms are normally found where the biotic and abiotic factors favour them, thus they have the resources they need and predation ism low).
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Which two types of transect can be used to measure the distribution of organisms within an ecosystem? Explain how to carry out these two methods.
Line and Belt. Line: lay a surveyor's tape along the ground and take sample's at regular intervals. Belt: 2 parallel lines are marked and samples are taken from the area between these specified points.
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What type of sampling do belt and line transects come under?
Systematic
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Briefly describe systematic sampling. What is an advantage of this over random sampling.
In systematic sampling different areas within a habitat are identified and sampled separately for a comparison. It mean scientist can see how different abiotic factors in different areas of the habitat effects species distribution. e.g. succession
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What is meant by the abundance of organisms?
The number of organisms in an area at any given time.
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What may increase and decrease the abundance of organisms?
Death, birth, immigration and emigration
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What is the definition of population?
A group of similar organisms living in a given area at a given time.
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How can you increase the accuracy of estimating a population and eliminate bias?
Use as large a sample as possible and use random sampling.
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How can you calculate an estimated no. of plants per m^2?
Number of individual organisms/ total sample area in m^2
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Name and describe a method for measuring animal abundance.
capture-mark-release-recapture, each time measuring the amount of unmarked and marked individuals. Must allow time for organisms to redistribute themselves.
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What is the equation for the Lincoln index for measuring animal population size?
(no. of individuals in 1st sample x no. of individuals in 2nd sample)/ no. of recaptured marked individuals.
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What index is used to calculate the biodiversity present in a habitat?
Simpson's index of Diversity (D).
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What is the formula for Simpson's Index of Diversity? What does each component stand for?
D= 1-Σ(n/N)^2 Σ=the sum of n= no. of individuals of each species N= total no. of organisms in an ecosystem
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Simpsons's index of diversity= always between 1 and 0. What does 1 mean and what does 0 mean?
0= no diversity 1= infinite diversity
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Draw the population growth curve. No. of organisms against time.
Include, phase 1 (slow growth, 2 (rapid growth) and 3 (stable state).
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Explain phase 1 (slow growth) of a population curve.
Small no.s of individuals present slowly increasing the total population. B.R. = higher than D.R. so population increases.
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Explain phase 2 (rapid growth) of a population curve.
An increase in breeding individuals= total population increases exponentially. No constraints= population explosion.
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Explain phase 3 (stable state) of a population curve.
Further population growth is prevented by external constraints, population size will slightly fluctuate as birth rates and death rates are approximately equal.
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The 2 types of limiting factors for population growth and examples of each.
Abiotic: temperature, light, pH, water availability, O2 availability, humidity. Biotic: predators, disease, competition.
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What is immigration and how does it effect population size?
The movement of individual organisms into an area, increases population size.
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What is emigration and how does it effect population size?
The movement of individual organisms away form a particular area, decreases the population size.
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What is a density independent factor? Give examples.
Factors that affect the whole population regardless of its size and dramatically change the population size. For example, earthquakes, fires, volcanic eruptions and storms
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What are the 2 types of competition? Give the definitions.
Interspecific competition: competition between different species for the same resource. Intraspcecific competition: competition within the same species.
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What might two species compete for in interspecific competition? What will happen if one of these species is less adapted to cope?
Food, there will then be less available for organisms of the two species= less energy for reproduction + growth. Species worse adapted will be outcompeted.
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What is the competitive exclusion principle?
2 species competing for limited resources, one that uses resources most effectively will eventually lead to elimination of the other.
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Give an example of interspecific competition.
Red + grey squirrels, UK. Grey= introduced in 1870s from North America + population increased rapidly + red squirrels disappeared from many areas because grey squirrel can eat a larger range of food= stores more fat= increases survival= reproduces
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Explaining using stage 1,2 and 3 why does population size fluctuate when intraspecific competition occurs.
1: resource= plentiful (e.g. food/space) = all organisms enough to survive= reproduce= increase pop. size. 2: Increased pop. = more individuals sharing= resources limi ted= pop. decreases. 3: Less comp. (smaller pop.) = ^ survival + reproduction
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Define predation. What type of competition is this?
When an organism kills and eats another organism. Interspecific.
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Other cards in this set

Card 2

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Give examples of biotic abiotic factors

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Biotic: organisms present, competition (e.g. for food space and territory). Abiotic: light, temperature, water availability, oxygen availability and EDAPHIC (soil factors).

Card 3

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Explain how the abiotic factor light may affect an ecosystem.

Back

Preview of the front of card 3

Card 4

Front

Explain how the abiotic factor temperature may affect an ecosystem. Explain why this affects endotherms to a lesser degree.

Back

Preview of the front of card 4

Card 5

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Explain how the abiotic factor water availability may affect an ecosystem.

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