Ecosystems, 6.5 Flashcards
What is an ecosystem?
Group of living and non-living things and the interrelationships between them
What is a habitat?
Place where an organism lives
What is a population?
Organisms of one species who live in the same place at the same time and can interbreed
What is a community?
Populations of different species who live in the same place at the same time and can interact
What is a niche?
The role of an organism within its habitat
What are biotic factors?
Living organisms in an ecosystem that affect each other
Who are the producers?
Plants, supply chemical energy
Who are the consumers?
Primary consumers - herbivores. Secondary consumers - carnivores
What is the role of decomposers?
Feed on waste material and dead organisms
What are abiotic factors?
Non-;living components of an ecosystem
What are some examples of abiotic factors?
pH. Relative Humidity. Temperatures. Concentration of pollutants. Weather eg storms.
Why are ecosystems described as dynamic?
Because they change
What are cyclic changes?
Changes that repeat themselves in a rhythm eg waves, the tide
What are directional changes?
Change goes in one direction and lasts longer than the lifetimes of the organisms in the ecosystems
What are unpredictable/erratic changes?
No rhythm or direction eg effects of a hurrican
In what ways might organisms respond to changes?
Some animals change their fur colour in the winter. Trees shed their leaves.
What is biomass transfer?
Transfer of biomass from one trophic level to another
What is the trophic level?
The level at which an organism feeds in a food chain
What is the role of plants ?
- Capture energy
- Produce glucose
- Products of photosynthesis incorporated into tissues and organs
- Mineral ions taken up through the roots
- When a plant is eaten its biomass is consumed by a primary consumer
Why is some biomass lost at each stage of a food chain?
- Organisms need energy to carry out life processes
- Some energy converted to heat
- Materials lost in CO2 and water
- Biomass also lost in dead organisms or waste material
- Also include bones and hair which cant be digested.
In a pyramid of biomass what is does each bar represent?
The area of each bar is proportional to the number of individuals
How does an ecologist calculate the efficiency of biomass transfer?
- Ecologist collects all the organisms and outs them in an oven at 80degrees
- Until all the water has been evaporated
- once the mass stops reducing the water has been removed
- Destructive to the ecosystem being studied
- Ecologists often just measure wet mass
What is meant by productivity?
Rate of production of new biomass by producers
What is gross primary productivity?
Rate at which plants convert light energy to chemical energy
Why is gross primary productivity inefficient?
Energy is lost when the plant respires. Only a small proportion of energy from the sun remains to enter the food chain
What can be done to help plants grow and make energy conversion more efficient?
- Light levels maintained under light banks
- Irrigating crops and drought resisting strains
- Grow plants in a greenhouse
- Crop rotation, more nutrients available
- Pesticides, stop insects
Why don’t primary consumers make full use plants biomass?
Much of it is respired so only a small amount contributing to increase biomass
What methods are there of increasing the amount of energy from primary consumers?
- Young animals use more energy in growth so harvest just before adulthood
- Selective breeding produces breeds with high growth rates
- Animals may be treated with antibiotics
- Mammals lose energy by finding food but none is lost by allowing them to graze
How are dead and waste organic materials decomposed?
By decomposers such as bacteria and fungi. They feed saprotrophically.
How do decomposers feed on waste material?
- Secrete enzymes onto dead and waste material
- Enzymes digest material into small molecules which are then absorbed into the saprotrophs
- Molecules are stored or respired
What are the 3 different stages of recycling nitrogen?
Nitrogen fixation. Ammonification and nitrification. Denitrification.
What is Nitrogen Fixation?
- Makes up 79% of the atmosphere
- Impossible for plants to use directly
- Need a supply of fixed nitrogen
- Occur during lightning strikes, haber process or nitrogen fixing bacter
What can the the bacteria Rhizobium do?
Provide the plant with nitrogen and receive carbon compounds - mutualistic relationship
What is ammonification and nitrification?
- Ammonium ions are release through ammonification by bacteria involved in purtrefaction of proteins found dead organic matter
- Some chemoautrophic bacteria obtain energy by oxidising ammonium ions to nitrites
- Others obtain energy by oxidising nitrites to nitrates
- Nitrates can be absorbed by plants to make nucleotide bases and amino acids
What is denitrification?
- Bacteria can convert nitrates back into nitrogen gas
- When bacteria are involved growing under anaerobic conditions eg water logged soils
- Uses nitrates as a source of oxygen
- So produces nitrogen gas and nitrous oxide
Draw a diagram of the carbon cycle
- Animals: feed respire, death, excretion, fossils
- Detritus and waste: death, decomposition, produced CO2
- Fossil fuels: fossilization, combustion
- Plants: photosynthesis, respiration, eaten, death
What is succession?
Progressive change in a community over time
What is primary succession?
Development of communities from bare rock
What are the stages of primary succession?
- Algae and lichens begin to live on bare rock - pioneer community
- Erosion of the rock and the build up of dead organic material produce nutrients and soil for larger plants to grow - these replace the algae and lichen
- Larger plants continue to succeed smaller plants until a final stable community is reached
What is the climax community?
A stable final community often woodland
What is secondary succession?
Takes place on a previously colonized but damaged habitat
Describe succession on sand dunes.
- Embryo dune -pioneer species eg sea rocket, prickly saltwort - just above the high water mark, harsh, salty
- Wind lows sand to form mobile dune - pioneer species eg marram grass, plants die and decay providing nutrients
- Semi-fixed dune - intermediate colonies, restharrow, dne moss, grasses - stabilises the sand
- Fixed Dune - sea purge and marram grass grow, traps more sand, stability and nutrients
- Sand dune and nutrients build up and other plants colonise
- Scrub
- Climax community (forest) - Final endpoint of succession, stable self-replication community, oak ash, woodland, trees
Why are sandunes conserved?
Multitude of habitats supporting specialised plant species
What are they doing to conserve the sand dunes?
- Prevent beach cleaning of seaweed
- Scrub clearance
- Removal of forestry plantation
- Grazing
- Fencing to stop cattle
- Beach nourishment
What is zonation?
Change in plant and animal communities over space
What is deflected succession?
Happens when succession is stopped or interfered with for example agriculture
What is sampling?
- Small portions from a habitat
- Representative of the larger habitat
What are quadrats?
Small sampling square
How can we use quadrats for sampling?
- Distribution (presence of absense), 50% of the plant in the quadrat to count
- Abundance (number of individuals) of each species estimated or counted
How can we place quadrats?
- Randomly, random numbers
- At regular intervals across the habitat
How many samples should you take?
- Plot a cumulative frequency against quadrat number
- When curve levels off tells you how many quadrats to use
What does a transect measure?
Changes across a habitat
What is a line transect?
At regular intervals make a note of the species touching the tape
What is a belt transect?
At regular intervals place a quadrat
