Ecosystems Flashcards
What is ecology?
The name given to the study of relationships between organisms and the environment
What is the study of ecology important?
So scientists can understand interdependence between living organisms and therefore help the survival of earths biodiversity
What is an ecosystem?
The interaction between all the biotic and abiotic element living in a defined area
Ecosystems are dynamic.
What does this mean?
They are constantly changing
What are the two factors that affect an ecosystem?
- Biotic factors (living)
- Abiotic factors (non-living)
What do animals compete for?
- Food
- Space
- Partners
What are the 3 main types of soil?
- Clay
- Loam
- Sandy
What is an edaphic factor?
Soil
What are the 5 main abiotic factors affecting an environment?
- Light
- Temperature
- Water availability
- Oxygen availability
What 2 adaptations do plants have to cope with low light levels?
- Larger leaves
- Photosynthetic pigments requiring less light
What is the source of energy for most ecosystems on earth?
The suns light energy
What do food webs and food chains show?
The transfer of biomass
What is each stage in a food chain known as?
A trophic level
What does the first trophic level always consist of?
A producer
What does a producer do?
It is an organism that converts light energy into chemical energy by photosynthesis
What are the subsequent levels of a food chain called after the producer?
Consumers
What are consumers?
Organisms that gain their energy by feeding on other organisms
What is the second trophic level occupied by?
A primary consumer - an animal that eats the producer
What is the role of decomposers?
They breakdown dead organisms releasing nutrients back into the ecosystem
What does a pyramid of numbers depict?
The number of individuals at each trophic level
What is biomass?
The mass of living material present in a particular place or in particular organisms
Why is biomass an important measurement in food chains?
It can be equated to energy content
How can biomass be presented?
Pyramid of biomass
How do scientist calculate the ‘dry mass’ of an organism to calculate biomass?
Kill the organic and good at 80 degrees until all water is evaporated
What tends to happen to biomass as you move up the pyramid?
It usually decreases
What is ecological efficiency?
The efficiency in which biomass is transferred through trophic levels
Producers only convert 1-3% of sunlight into biomass, why? [3]
- Not all energy can be used in photosynthesis
- Limiting factors of photosynthesis
- Energy is lost as it is used for photosynthetic reactions
What is the calculation of energy transferred to the next trophic level?
Net production = gross production - respiratory loss
Consumers at each trophic level convert around 10% of the biomass in their food.
Why? [3]
- Not all matter is eaten (bones, plant roots)
- Movement and respiration will cause energy loss
- Some parts of the organism are indigestable
How do we calculate ecological efficiency of the energy transfer between trophic levels?
Ecological efficiency = energy after transfer / X100 energy before transfer
How are food chains affected by agriculture?
They become very simple as competition and predators are removed
Producer > primary consumer > secondary consumer
Animal feed > cow > human
What does the simplified agricultural food chain mean?
Minimum energy is lost and as much energy as possible is transferred for humans to eat
What are the main decomposers?
Fungi and bacteria
What is a saprotroph?
An organism obtaining their energy from dead waste material e.g a decomposer
What is a detrtivore?
An organism that speed up decay by feeding on dead and decaying material e.g wood lice
What are two forms of nitrogen fixing bacteria?
Azotobacter (free in soil) and rhizobium (inside root nodules)
What is nitrogen fixation?
The process in which nitrogen fixing bacteria use the enzyme nitrogenase to combine atmospheric nitrogen N2 with H2 to produce NH3 that can be used by plants
What are root nodules?
Growths that grow in leguminous plants
How does rhizobium bacteria have a symbiotic mutualistic relationship with the plant?
Both organisms benefit:
- plant gains amino acids from Rhizobium
- bacteria gain carbohydrates from plants to use as an energy source
What is nitrification?
The process in which ammonium compounds in the soil are converted into nitrogen containing molecules that be used by plants
What type of reaction is nitrification, and therefore what conditions are needed?
It is an oxidation reaction so soil needs to be aerated
What are the 2 stages of nitrification?
- Nitrosomas oxidise ammonium compounds to nitrites NO2-
- Nitrobacter oxidises nitrites into nitrates NO3-
What is denitrification and what conditions are needed?
Denitrification is the conversion of nitrates back to nitrogen gas
This only happens in anaerobic conditions
How do atmospheric levels of carbon dioxide fluctuate?
Levels are higher at night than in the day as plants do not photosynthesise at night but still respire
How do carbon dioxide levels fluctuate seasonally?
As days are longer and photosynthesis rates are higher in summer carbon dioxide levels will be lower
Why have global atmospheric carbon dioxide levels increase in the last 200 years?
- Combustion of fossil fuels
- Deforestation
How does the atmospheric temperature affect the absorption of carbon dioxide in the ocean?
The higher the temperature of water the less gas can dissolve
what us succession?
The process by which ecosystems change over time
What is primary succession?
This occurs on a newly formed area of of land, no soil or organic matter present
What is secondary succession?
Occurs on an area of land where soil is present but no animal o plant species
E.g after a forest fire
When does primary succession occur?
- Volcanoes erupt
- Sand is deposited to make new dunes
- Mud is deposited at river estuaries
- Glaciers retreating
What is each stage of succession known as?
Seral stage
What are the main 3 stages of succession?
- Pioneer community
- Intermediate community
- Climax community
What is a pioneer species?
The species that colonise an inhospitable environment
What are the adaptations of pioneer species?
- Produce large quantities of seeds or spores
- Germinate rapidly
- Photosynthesise
- Tolerance to environment
- Can fix nitrogen form environment
What is humus?
Organic component of soil
What is a climax community?
The stable community that will show little change over time
Why is biodiversity levels higher in the intermediate stage than the climax stage of succession?
Dominant species will out compete other species
What is plagioclimax?
When succession is stopped artificially (usually by humans)
Why does agriculture cause deflected succession?
- Grazing and trampling of vegetation 2. Removing vegetation to plant crops 3. Burning to clear Forrest’s
What is distribution of organisms? And what is it like in an ecosystem?
Distribution of organism is where organisms are fond within an ecosystem They are usually uneven
Where are organisms usually found within an ecosystem?
Where abiotic and biotic factors favour their survival
Why may abundance of organism fluctuate?
Immigration and birth will increase individual numbers and emigration and death will decrease individual numbers
What is abundance of organisms?
The number of individuals of a species present in an area at a given time
What is used to measure distribution of organisms in an environment?
Line or belt transect
What is the calculation for measuring plant abundance?
Estimated population (m2)= number of individuals in sample / area of sample
How do we measure abundance of plants?
Using random placement of quadrants in an area
What technique is used to measure animal abundance?
Capture, mark, release, recapture
What is the calculation for Animal abundance?
Estimated population = individuals in first sample x individuals in second sample / number of recaptured marked individuals
What Do we use to calculate biodiversity in a habitat?
Simpsons index of diversity (D) D = 1 - (sum of) (n/N)2 N = total number of organisms in ecosystem, n = total number of species
