Studied by 0 peopleoutline the levels of organisation in an ecosystem
individual
population
community
ecosystem
define population
all organisms of the same species living with one another in a habitat
define community
all of the populations of different species living together in a habitat
define ecosystem
the community of biotic and abiotic components of an area and their interactions
organisms with a community are described as being ‘interdependent’. What does this mean?
organisms are dependent upon each other
a change in the population of one species can affect other populations within a community
give some examples of interdependence in a community
plants depend on pollinators e.g. bees
herbivores are dependent on plants
animals are dependent on mates
describe mutualism
the interaction between two organisms where both benefit as a result of their relationship
describe parasitism
the interaction between two organisms where only one organism, the parasite, benefits whilst the host does not
what are abiotic factors? give some examples
the non- living aspects of an ecosystem e.g. light intensity temperature, moisture levels, carbon dioxide levels
describe how communities are affected by environmental conditions
environmental conditions (e.g. temperature, light intesity, carbon dioxide levels) affect the abundance and distribution of organisms within communities
e.g. light intensity affects the rate of photosynthesis in producers which serve as a source of food and shelter for other organisms
describe how communities are affected by pollutants
toxic chemicals (e.g. pesticides) bioaccumulate in food chains to deadly concentrations at higher trophich levels, killing tertiary and quaternary consumers
fertilisers that contaminate water sources can cause eutrophication, killing multiple populations within a community
air pollution can affect the ability of some plant species to survive
what are biotic factors? give some examples
the living components of an ecosystem e.g. competiton, predation
describe how competition affects communities
the presence of competittors affects population distribution and size
if one species is better adapted to survive in a certain environment, it will outcompete other species, causing their populations to decline
describe how predation affects communities
predation affects prey populations within a community
e.g. if the number of predators decreases, the number of prey will increase as fewer are killed
populations of all other organisms within the food chain will also be affected
what piece of apparatus is used to measure the abundance and distribution of organisms in an area?
quadrat
what piece of apparatus is used to study the distribution of organisms across a gradient
belt transect
what does a food chain show
it describes the feeding relationships between organisms and the resultant stages of biomass transfer
define biomass
the total mass of living material
what are trophic levels
the stages in a food chain
what do arrows in a food chain represent
the direction of biomass transfer
describe a simple food chain
producer —> primary consumer —> secondary consumer —> tertiary consumer
why are the producers the first trophic level
producers provide all biomass for the food chain (via photosynthesis)
the rest of the food chain involves the transfer of this biomass
what does a pyramid of biomass represent
it represents the dry mass of living material at each trophic level of a food chain
why is a pyramid of biomass almost always pyramid-shaped
producers (at the bottom of the pyramid) have the greatest biomass so have the longest bar
as you move along the food chain (and up the pyramid) biomass is lost so the bars decrease in length
why is biomass lost between each trophic level in a food chain
glucose is immediately used for respiration in plants
respiration to generate heat energy, energy for metabollic processes
some parts of organisms are indigestible
egestion, excretion
why are there rarely more than four or five trophic levels in a food chain
above this, there is insufficient energy to support another breeding population
what is the equation for calculating the efficiency of biomass transfer between trophic levels
efficiency = biomass available after transfer / biomass available before transfer X 100
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