6.3.1 Flashcards
Ecology
Study of the relationships between organisms and their environment ; interdependence of living organisms and to help ensure survival of as much of earth’s biodiversity as possible
Ecosystem
All living organisms that interact with one another in a defined area and the physical factors present in that region ; they can vary from a tiny bacterial colony to the entire biosphere of Earth
Boundaries of an ecosystem?
Defined by the person or team carrying out the study ; may be a rock pool or small areas of land
Describe ecosystems?
They are dynamic - constantly changing due to the living organisms present and their environmental conditions
Types of factors
Biotic and abiotic factors
Biotic factors
Living factors ; size of their populations - competition for food source
Abiotic factors
Non-living or physical factors ; amount of rainfall received/yearly temperature range of the ecosystem
What do animals compete for?
Food, space and breeding partners
Abiotic factors
Light Temperature Water availability Oxygen availability Edaphic (soil) factors
Light (abiotic factors)
Light is required for photosynthesis and the greater the availability of light, the greater the success of a plant species
Plants develop strategies to cope with different light intensities ; in areas of low light, they may have larger leaves and they may also develop photosynthetic pigments that require less light/reproductive system when light availability is at an optimum
Temperature
Enzymes controlling metabolic reactions ; plants develop more rapidly in warmer temperatures as well as ectothermic animals (those whose internal temperature is affected by external environment)
What can changes in temperature cause?
Trigger migration in some animal species and hibernation in others ; in plants it can trigger leaf fall, dormancy and flowering
Water availability
Lack of water leads to water stress which could lead to death ; also causes many plants to wilt (needed to keep them turgid) and required for photosynthesis ; cacti are xerophytes, plants which have developed successful strategies to cope with water stress
Oxygen availability
In aquatic ecosystems it is beneficial to have fast flowing cold water as it contains high concentrations of oxygen ; if water becomes too warm/slow then this can lead to suffocation of organisms due to drop in O2 levels
In waterlogged soil
Air spaces between the soil particles are filled with water ; reduced oxygen availability
Edaphic factors?
Different soil types have different particle sizes that has an effect on the organisms that are able to survive in them
Clay
Loam
Sandy
Clay
Fine particles - easily waterlogged - forms clumps when wet
Loam
Different sized particles - retains water but does not become waterlogged
Sandy
Coarse, well separated particles that allow free draining ; Sandy does not retain water and are easily eroded
Biotic factors
Disease Predation Parasitism Competition Producers Consumers Decomposers
What are food chains/webs?
Diagrams used to show the transfer of biomass (and thus energy) through the organisms in an ecosystem ; each stage is known as a trophic level
First trophic level
Producer - organism that converts light energy into chemical energy via photosynthesis
Subsequent trophic levels
All consumers ; organisms that obtain their energy by feeding on other organisms
Second trophic level
Primary consumer
Trophic levels
Producers -> primary consumers -> secondary consumers -> tertiary consumers -> quaternary consumers
How many trophic levels do food chains have?
Rarely have more than 4/5 as there is not sufficient biomass and stored energy left to support any further organisms
Pyramid of numbers food web
Gets smaller and smaller - fewest quaternary consumers compared to a much larger base of producers
Decomposers?
Break down dead organisms releasing nutrients back into the ecosystem
Biomass
Mass of living material present in a particular place or in particular organisms ; can be equated to ENERGY CONTENT
How to calculate biomass at each trophic level?
Multiply the biomass present in each organism by the total number of organisms in that trophic level ; often presented diagrammatically like a pyramid of biomass - DOES NOT TAKE INTO ACCOUNT SEASONAL CHANGES JUST PRESENTS IT AT A PARTICULAR MOMENT IN TIME
How do scientists measure biomass?
Water material must be discounted as the presence of varying amounts of water in different organisms makes this technique unreliable unless very large samples are used ; thus only calculate dry mass
Problems with calculating the dry mass?
Organisms must be killed and placed in an oven until all the water is evaporated ; this point is indicated by “heating to a constant mass” - only a small sample is taken but this MAY NOT BE REPRESENTATIVE
Biomass for areas?
Grams/square metre - area of land
Grams/cubic metre - for areas of water
When is pyramid of biomass not a pyramid?
When in an aquatic environment the phytoplankton mass is very small at any given time but they reproduce very quickly so over a period of time there is always more phytoplankton than zooplankton
Why is biomass at trophic level always less than one below?
Biomass consists of all the cells and tissues of the organisms present including carbs etc ; as carbon compounds are a store of energy, biomass can be equated to energy content and when animals eat only a small proportion of the food they ingest is converted to new tissue - ONLY THIS PART OF BIOMASS IS AVAILABLE FOR NEXT TROPHIC LEVEL TO EAT
Energy available at each trophic level?
Kilojoules/m^2/year to allow for changes in photosynthetic production and consumer feeding patterns throughout the year
What is ecological efficiency?
Efficiency with which biomass is transferred from one trophic level to the next ; amount of biomass converted to new biomass by each trophic level can be represented by a pyramid of energy
What percentage of sunlight do producers convert?
Only 1-3% into chemical energy and hence biomass
Why do producers only convert that much of the sunlight?
Not all of the solar energy available is used for photosynthesis ; approximately 90% is reflected and a lot is transmitted/wave length is unusable
Water availability may limit photosynthesis (other factors)
Proportion of energy is “lost” as it is used for photosynthetic reactions
What is gross production?
Total solar energy that plants convert to organic matter
Why is gross production not accurate?
Because 20-50% of gross production is used in respiration and the remaining energy is converted into biomass ; this is the energy available to the next trophic level and is known as the net production
Energy available to the next trophic level formula?
Net production = gross production - respiratory losses
Calculation can be all,Jed to biomass/energy production too
Generation of biomass in a producer?
Primary production
Generation of biomass in a consumer
Secondary production
Why is efficiency only 10% for consumers?
Not all biomass is eaten (hairs, bones etc)
Energy transferred to environment as metabolic heat as a result of movement and respiration
Some parts of an organism are eaten but indigestible ; they are egested as faeces
Energy is lost from the animal in excretory materials such as urine
How much of the total energy present in sunlight is embodied as biomass in the tertiary consumer?
0.001%
Efficiency of energy transfer (biomass transfer equivalent) between each level
Ecological efficiency = (energy available after the transfer) / (energy available before the transfer) * 100
What does agriculture involve?
Manipulating the environment to favour plant species that we can eat (crops) and to rear animals for food/their produce ; plants and animals are provided with the abiotic conditions they need to thrive such as adequate watering and warmth (greenhouse etc) and competition too is removed (pesticides) as well as threat of predators
Humans in natural ecosystems?
Occupy 2/3/4 trophic levels and at each one there are considerable energy losses ; only a tiny proportion of energy available at the start of the food chain is turned into biomass for consumption at 3/4 levels
What does agriculture do that’s very clever?
CREATE VERY SIMPLE FOOD CHAINS TO MINIMISE ENEGY LOSS AS THERE ARE FEWER TROPHIC LEVELS THAN IN THE NATURAL WORLD
LIVESTOCK ; FEED -> LIVESTOCK -> HUMANS
PLANTS : PLANTS -> HUMANS
Ensures as much energy as possible is transferred into biomass that can be eaten by humans
How are animals optimised?
Intensively farmed animals are kept in strictly controlled environments where they have high temperatures and small spaces to restrict heat dissipation ; don’t need to maintain body temperature etc
How else can humans manipulate biomass transfer?
Increasing productivity of producers using fertilisers/soil improvement
Fungicides and insecticides are also used + herbicides to reduce competition from weeds etc
Animals given feed that’s higher in energy than their natural food ; increases energy input
ETHICAL doubts - pain etc
Difference between sun and nutrients?
Sun is a linear flow of energy transferred from one source and continually being replenished ; nutrients are recycled as they are used up by living organisms and there is no large external source constantly replenishing nutrients in the way the Sun supplies energy
Decomposition?
Chemical process in which a compound is broken down into smaller molecules ; often essential elements such as nitrogen or carbon cannot be used directly by an organism in the organic form it used in ; it must be processed into inorganic elements and compounds which are a more usable form
Decomposer
Feeds on and breaks down dead plant or animal matter ; TURNS ORGANIC COMPOUND INTO INORGANIC ONES available to producers in the ecosystem - they are primarily fungi/bacteria ; SAPOTROPHS
What are decomposers?
SAPOTROPHS ; they obtain their energy from dead/waste organic material - digest their food externally by secreting enzymes onto dead organisms or organic waste matter and the enzymes break this down into simpler soluble molecules ; they then absorb these molecules and through this they release stored inorganic compounds and elements back into the environment
Detritivores?
Another class of organism involved in decomposition ; help to speed up the decay process by feeding on detritus - dead/decaying material ; they break it down into smaller pieces of organic material which increases the SA for decomposers to work on
Examples of detritivores
Woodlice/earthworms - they PERFORM INTERNAL DIGESTION
What is nitrogen used for?
Amino acids and nuclei acids in plants and animals ; plants have to take it in from their environment while animals obtain the nitrogen from the food they eat
Why can nitrogen not be taken in its natural form?
Too stable ; triple bond in N2 ; must be combined with oxygen or hydrogen to be used by living organisms - 78% of air is N2 ; bacteria play a very important role in converting N2 into a useable form and without them N2 would become a limiting factor pretty quickly
Ammonia, nitrates, nitrites
Nitrogen-contains molecules
Nitrogen fixation?
Nitrogen-fixing bacteria ; azotobacter and Rhizobium contain the enzyme nitrogenase which combines N2 with H2 to produce Ammonia ; a form of nitrogen that can be absorbed and used by plants
Rhizobium
Live inside root nodules which are growths on the roots of leguminous plants ; symbiotic relationship
Symbiotic mutual is tic relationship nitrogen-fixing bacteria
Plant gains amino acids from Rhizobium through fixing N2 into NH3
Bacteria gain carbohydrates produced by the plant during photosynthesis ; which they use as an energy source
Other bacteria then convert the NH3 into other organic compounds that can be absorbed by plants
Azotobacter
Free-living soil bacteria
N2
Nitrogen gas in atmosphere - cannot be used directly by plants
Ammonia/ammonium ions
Produced by nitrogen fixing bacteria and decomposers
Nitrites
Formed from nitrifying bacteria from ammonia ; CANNOT BE ABSORBED BY PLANTS
Nitrates
Produced by nitrites by nitrifying bacteria ; PLANTS CAN ABSORB
Nitrifcation
Process by which ammonium compounds in the soil are converted into nitrogen contains molecules that can be used by plants
Nitrifying bacteria
Free-living bacteria in the soil
Nitrification steps?
Oxidation - only occurs in well-aerated soil
1) Nitrifying bacteria (Nitrosomonas) oxidise ammonium compounds into nitrites
2) Nitrobacter (another genus of nitrifying bacteria) oxidise nitrites (No2-) into Nitrates
Nitrate ions
HIGHLY SOLUBLE and thus the form in which most nitrogen enters a plant
Denitrification
Absence of oxygen (waterlogged soils) ; they convert nitrates in the soil back to nitrogen gas ; ONLY HAPPENS under anaerobic conditions ; bacteria use the nitrates as a source of energy for respiration and nitrogen gas is released
Ammonification
Process by which decomposers convert nitrogen contains molecules in dead organisms/faeces/urine into ammonium compounds
What artificial processes have an affect on the Nitrogen cycle?
Haber process ; used to make ammonia for fertiliser
Lightning?
Nitrogen fixing by non-living processes (and Haber process)
Carbon?
Although only makes up 0.04% of the atmosphere, there is a constant cycling of carbon between the atmosphere, the land and living organisms ; makes up all major organic molecules
Major source of inorganic carbon for plants?
Carbon dioxide in the atmosphere and dissolved in the seas and oceans
Fossil fuels
Combustion occurs and CO2 released into the atmosphere
Carbon contains compounds in producers
Converted into small organic molecules by photosynthesis in plants and other photosynthesis organisms ; carbon is then used in the production of macromolecules such as carbohydrates, proteins and lipids in producers
Carbon contains compounds in consumers
Carbon macromolecules are passed from producers into primary consumers when they are eaten ; subsequently passed up the food chain
Carbon contains compounds in decomposers
Carbon compounds are released through decomposition ; carbon is released into atmosphere when DECOMPOSERS RESPIRE as CO2
If dead organic matter accumulates where decomposers are not present (lack of O2) ; carbon they contain may become trapped and these remains form fossil fuels over millions of years
How do CO2 levels fluctuate?
Photosynthesis only takes place during the day (light) and so it removes CO2 from the atmosphere ; respiration however is carried out by all living organisms throughout the day and night thus releasing co2 at a relatively constant rate into the atmosphere thus CO2 levels are higher at night
Localised CO2 levels?
Fluctuate seasonally ; lower in summer as photosynthesis rates are higher then
Why have CO2 levels differed significantly globally over the past 200 years?
1) combustion of fossil fuels ; released CO2 back into the atmosphere from carbon that had been trapped below the earth’s surface
2) deforestation : removed significant quantities of photosynthesising biomass from the Earth ; less CO2 removed from the atmosphere and when clear forest is burnt this releases more CO2 into the atmosphere
High levels of CO2?
More thermal energy trapped ; contributes to global warming (greenhouse gas)
What does global warming do?
Higher the temperature, the less CO2 dissolved in seas and oceans ; reduces the carbon Bank in oceans and releases more into the atmosphere - POSITIVE FEEDBACK LOOP
How to gain information about how atmosphere has changed?
Samples are taken from deep within glaciers ; air bubbles within the ice are analysed
Process by which ecosystems change over time?
Succession ; ecosystems are dynamic - constantly changing ; further away you move from the sea, more biodiverse the ecosystem becomes
Why does succession occur?
Result of the changes to the environment (abiotic factors) causing plant and animal species to change
Primary succession?
Area of land that has been newly formed/exposed such as bare rock ; no soil or organic material present to begin with
Secondary succession?
Areas of land where soil is present ; but it contains no plant or animal species - bare earth that remains after a forest fire
When does primary succession occur?
Volcanoes erupting ; deposit lava which cools and solidifies forming igneous rock
Sand is blown by the wind/deposited to create sand dunes
Silt and mud deposited at river estuaries
Glaciers retreat depositing rubble and exposing rock
How does succession take place?
In many steps ; called serial stages (seres) ; CHANGE THE ABIOTIC FACTORS FOR SUBSEQUENT EXISTENCE OF OTHER SPECIES
Main serial stages?
Barren land -> pioneer community -> intermediate community -> climax community
Hostile, low species diversity, instable TO less hostile, high species diversity and stable
Primary succession?
Slow process
Secondary succession?
Relatively rapid
How does primary succession begin?
Colonisation of an inhospitable environment by a pioneer species ; arrive as spores or seeds carried by wind from nearby land masses ; ALGAE AND LICHEN AND MARRAM GRASS
Adaptations of pioneer species?
Large quantities of seeds or spores (blown/deposited on the new land)
Seeds that germane rapidly
Ability to photosynthesise to produce their own energy ; autotrophic
Tolerance to extreme environments
Ability to fix nitrogen from the atmosphere/adding to the mineral content of the soil
Lichen features?
Able to survive without soil/take up rainwater and mineral salts through the whole of their body surface
Intermediate community?
Weathering of the bare rock produces particles that form the basis of a soil ; when pioneer species die and decompose small organic products are released ; THIS IS HUMUS ; now the soil can support the growth of new species of plant (secondary colonisers) as it contains minerals including nitrates ; now they arrive as spores/seeds
Secondary coloniser species?
MOSSES
Sometimes pioneer species are food to these consumers so animal species may begin to colonise
What happens next?
Environmental conditions improve ; tertiary colonisers like ferns arrive - these plants have a waxy cuticle that protects them from water loss and can survive in conditions without an abundance of water but they need to get most of their water from the soil
What happens at each stage?
Rock gets continually eroded and organic matter increases ; more nutrients rich deeper soil which retains more water - abiotic conditions now more favourable for flowering plants
What is this period of succession?
Intermediate community - multiple serial stages evolve during this period until climax conditions are attained ; at each stage they are better adapted to the current conditions in the ecosystem - they outcompete many of the species that were previously present and become the dominant species - most abundant species at a given time
Climax community
Final stage ; stable state - shows very little change - few dominant species ; which species depends on the climate (plenty of water + sunlight = trees while sub-arctic = herbs/shrubs due to low water availability)
When does biodiversity reach its peak?
Mid succession then tends to decrease as dominant species outcompete pioneer and other species ; more successful the dominant species the less biodiversity
Animal succession
Same as plants
Insects colonise an areas as they consume and she,fed in the mosses and lichens present
MUST MIGRATE SO MUCH SLOWER THAN PLANTS ESPECIALLY IF NEW LAND IS GEOGRAPHICALLY ISOLATED
When do secondary consumers (animals arrive)?
When suitable food source has been established and existing plant cover will provide suitable habitats - eventually larger organisms like mammals and reptiles will colonise the areas when biotic conditions are favourable
Plagioclimax
When succession is stopped artificially through human activities - this is the final stage ; same thing as deflected succession - cause is mainly agriculture
Deflected succession
Grazing/trampling of vegetation results in large areas remaining as grassland
Removing existing vegetation such as shrub land to plant crops - become final community
Burning as a means of forest clearance ; often leads to an increase in biodiversity as it provides space and nutrient rich ash for other species to grow (such as shrubs)
