Module 6 Section 6: Ecosystems Flashcards
What is a habitat
The place where an organism lives, e.g. a rocky shore or a field.
What is a population
All the organisms of one species in a habitat.
What is a producer
An organism that produces organic molecules using sunlight energy, e.g. plants
What is a consumer
An organism that eats other organisms, e.g. animals and birds.
What is a decomposer
An organism that breaks down dead or undigested organic material, e.g. bacteria and fungi.
What is a trophic level
A stage in a food chain occupied by a particular group of organisms, e.g. producers are the first trophic level in a food chain.
What is an ecosystem
All the biotic (living factors) and abiotic factors (non living factors) in a certain area
Examples of biotic factors
Food
Space (territory)
Breeding partners
Examples of abiotic factors
Light
Affects plants as light is needed for photosynthesis
Greater availability of light the greater the success of plant species
Temperature
Effects enzymes controlling metabolic reactions
Plants and ectothermic animals develop rapidly in warmer temperatures
Changing temperature (from seasons) can trigger migration or hibernation
Water availability
Lack of water leads to water stress which can cause death
Water stress will cause plants to wilt and reduce photosynthesis levels
Oxygen availability
Warm, slow flowing water leads to a drop in oxygen concentration
Lack of oxygen leads to suffocation of aquatic organism
Water logging also decrease amount of oxygen in soil leading to plant suffocation
Edaphic (soil)
Different soil types with different sized particles
Clay (small fine particles which are easily waterlogged), loam (mixed of sizes of particles which retains water but doesn’t waterlog), sandy (coarse, spaced out particles which doesn’t retain water but is easily eroded)
How can population size be affected by changes in an ecosystem
Cyclic changes: predator prey relationships, seasonal changes, day and night cycle, tides
Directional changes: climate change, deposition in rivers, erosion of a coastline
Unpredictable/erratic changes: natural disasters, lightning
Pattern of how species performance and intensity of abiotic factors
Includes factors such as temperature and pH
When may the pattern of abiotic factors and species performance not follow the bell curve
What is biomass
Mass of living material in a particular place
What is living material
Carbon containing material
How does energy mainly enter an ecosystem
Enters by photosynthesis where plants convert sunlight energy into a form that can be used by other organisms
Plants are called producers and store energy as biomass
Another word for energy transfer in ecosystems
Can also be called biomass transfer in ecosystems
How is energy transferred in ecosystems
When organisms eat other organisms
Producers are eaten by primary consumers, primary consumers are then eaten by secondary consumers and secondary consumers are eaten by tertiary consumers.
How can energy transfer be shown with diagrams
Food chains show simple lines of energy transfer
Food webs show lots of food chains in an ecosystem and how they overlap
When may energy be unable to be transferred and how is energy recycled back into the ecosystem
Energy can be locked up in the things that can’t be eaten (e.g. bones, faeces)
Gets recycled back into the ecosystem by decomposers.
How much energy is lost through tropic levels
About 90%
Why may large amounts of energy not be taken into producers or consumers in the first place
Around 60% is never taken in by organisms
Plants can’t use all the light energy that reaches their leaves
e.g. some is the wrong wavelength, some is reflected, and some passes straight through the leaves.
Some sunlight can’t be used because it hits parts of the plant that can’t photosynthesise
e.g. the bark of a tree.
Some parts of food, e.g. roots or bones, aren’t eaten by organisms so the energy isn’t taken in
Some parts of tood are indigestible so pass through organisms and come out as waste, e.g. faeces
These pass to decomposers
What is gross productivity
This is the rest of the available energy (40%) which is absorbed by plants
Describe the transfer of energy between organisms of different trophic levels and explain how energy can be lost between trophic levels
40% passed on from plants (gross productivity)
30% of total energy available (75% of gross productivity) is lost to the environment when organisms use energy produced from respiration for movement or body heat.
This is called respiratory loss.
10% of the total energy available (25% of the gross productivity) becomes biomass (e.g. it’s stored or used for growth)
This is called the net productivity.
This 10% is then passed onto the next consumer and repeats the process of respiratory loss
What is net productivity
This is the amount of energy that’s available to the next trophic level.
Also called biomass
Net productivity equation
Net productivity = gross productivity-respiratory loss
How is biomass measured (units)
Mostly measured as energy kJm⁻² yr⁻¹
Or in area/volume g m⁻²/ g m⁻³
Why is biomass transfer so inefficient
Biomass relates to all carbon containing material in an organism
When animals eat, only a small proportion of the food they ingest is converted into new tissue
It is only this biomass that is available to the next trophic level
How to calculate the energy transfer between trophic levels
Calculate difference between the amount of energy in each level
This is done by measuring the dry mass (no water) of the organisms (biomass) which indicates how much energy is stored in them
Measure biomass in sample then multiply by size of population
Find difference in energy between trophic levels
Problems with measuring energy transfer between trophic levels
Consumers may have taken in energy from sources others than the producer measured
Means that difference between two figures calculated wouldn’t be accurate
Need to include all individual organisms at each trophic level
How to calculate ecological efficiency
How can human activities increase transfer of energy from primary productivity
This is the rate at which plants convert light energy into chemical energy through photosynthesis
Herbicides kill weeds to reduce competition so crops receive more energy
Fungicides and insecticides kill fungi and insects that damage crops and allow them to use more energy for growth and not fighting an infection
Can also breed resistant crops
Natural predators introduced to the ecosystem eat the pest species so crops lose less energy and biomass
Fertilisers supply minerals needed for growth so more energy from the ecosystem can be used to grow
Increase light by planting crops early in growing season
Increase water using irrigation systems or breed drought resistant crops
How can human activities increase transfer of energy from secondary productivity
This is the rate at which energy is transferred from one trophic level to the next
Animals kept in warm, indoor pens so less energy is wasted moving and keeping warm and more is used for growth
Animals given feed thats higher in energy than their natural food to increase energy input and therefore energy needed for growth
Given antibiotics so less energy is used fighting off disease
Can selectively breed animals which grow faster or have larger yields
Harvest animals just before adulthood as young animals invest more energy into growth
Positive and negatives of humans increase secondary productivity
Positives:
More food can be produced in a shorter space of time with lower cost
Negatives:
Animals can be kept in pain, distress and their natural behaviour is restricted
Process of carbon cycle
CO2 absorbed by plants to become carbon compounds in photosynthesis
Carbon passed from primary to secondary to tertiary consumers through food chains
Dead organisms are digested by decomposers (bacteria and fungi) this is called saprobiontic nutrition
Carbon is returned to atmosphere by respiration of living organisms
Dead organic matter than can’t be reached by decomposers (bogs or deep oceans) they can become fossil fuels over millions of years
The carbon in fossil fuels (e.g. oil and coal) is released when they’re combusted
As well as coal, other types of rock can be formed from dead organic matter deposited on the sea floor:
E.g. limestone and chalk are mainly composed of calcium carbonate (CaCO3) (from shells of crabs and mussels)
Carbon returned to environment by the rocks being taken down into Earth’s crust by tectonic movement, they then release CO2 after number chemical changes which is returned to atmosphere by volcanoes
Rocks can be weathered chemically by rainwater to release mineral ions and bicarbonate ions (HCO3-) which can then be entered into rivers and oceans to combine to form carbon containing compounds like CaCO3
Rocks can be physically weathered roots or animals
CO2 can dissolve in oceans and be transported in the oceans by underwater currents
CO2 can remain in these currents for 100s of years before returning to surface and being released back into the atmosphere
How is nitrogen useful for plants and animals
Nitrogen is needed to make proteins and nucleic acids
For animals and plants
What is the use of the nitrogen cycle for plants and animals
Nitrogen in the atmosphere must be converted into a useable form using bacteria to make it into nitrogen compounds which can be taken up by plants and passed onto animals
What does the nitrogen cycle show
Shows how nitrogen is converted into a useable form then passed on between different living organisms and the non-living environment
What is nitrogen fixation
When nitrogen gas in the atmosphere is turned into ammonia by bacteria like Rhizobium and Azotobacter
Ammonia can then be used by plants
Rhizobium is found inside root nodules of leguminous plants (peas, beans) and form a mutualistic relationship with plants by providing them with nitrogen while plant provides them with carbohydrates
Azotobacter are found living in the soil and don’t form mutualistic relationships with plants
What is ammonification
When nitrogen compounds from dead organisms are turned into ammonia by decomposers which forms ammonium ions
Animal waste containing nitrogen compounds are also turned into ammonia by decomposers and go on to form ammonium ions
What is nitrification
When ammonium ions in the soil are changed into nitrogen compounds that can then be used by plants (nitrates)
First nitrifying bacteria (nitrosomonas) change ammonium ions into nitrites
Then other nitrifying bacteria called nitrobacter change nitrites into nitrates
What is denitrification
When nitrates in the soil are converted into nitrogen gas by denitrifying bacteria
They use nitrates in the soil to carry out respiration and produce nitrogen gas
This happens under anaerobic conditions
e.g. in water logged soils
Draw the nitrogen cycle
What is primary succession
Primary succession is where a species colonise a new land surface
Starts with seeds and spores being blown in by wind which begin to grow into pioneer species
Why can only pioneer species grow on a new land surface
The abiotic conditions are hostile and there’s no soil to retain water
Pioneers species are specialised to cope with the harsh conditions
E.g:
Have seeds that germinate rapidly
Can photosynthesise to produce their own energy
Tolerant of extreme conditions
Can fix nitrogen from atmosphere to add to mineral content of soil
How does the intermediate community start to grow from the pioneer community
Pioneer species change the abiotic conditions
They die and microorganisms decompose the dead organic material (humus)
Rock is also eroded into smaller particles
This forms a basic soil
Conditions then become less hostile (basic soil can retain some water)
Means that secondary colonisers can move in and grow (mosses)
These then die and are decomposed which add more organic material and make the soil deeper and richer in minerals
This means that larger plants can grow (shrubs) in the deeper soil which can retain more water
These are the tertiary consumers
Rock continues to be eroded and mass of organic matter increases which improves soil quality
Where are each of the seral stages found
Pioneer community: first seral stage
Intermediate community: multiple seral stages
Climax community: final seral stage
How may the species diversity in the intermediate stage change relatively fast
At each seral stage the different plant and animal species are better adapted to the current conditions in the ecosystem
These new organisms outcompete the species that were previously present
They become the dominant species
What is the climax community
Final seral stage
Community in a stable state and shows very little change over time
Normally a few dominant plant and animal species
The species that make up the climax community depends on the climate
E.g. in a temperate climate trees will form the climax community
What is the biodiversity of the climax community like
Not the most biodiverse
Biodiversity tends to reach a peak mid-succession then decreases
Due to dominant species outcompeting pioneer and other species
The more successful the dominant species, the less the biodiversity in a given ecosystem
What is deflected succession
Where human activities can halt the natural flow of succession and prevent the ecosystem from reaching climax community
Agriculture can cause this the majority of the time
Forms plagioclimax
How can agriculture form plagioclimax
Grazing and trampling vegetation can result in large areas becoming grassland
Planting crops means removing existing vegetation so crop becomes final community
Burning a forest to clear it results in space and nutrient rich soil for new species to grow so increases biodiversity