3.5 Population and Ecosystems

ecology

study of interactions between living organisms and their environment

ecosystem

interactions between the living and non living factors in an area

environment

the habitat and all the external conditions that affect the development and survival of an organism

habitat

the area an organism occupies

niche

the role and position a species has within its environment

population

the total number of a single species within a given area at a given time

abiotic environment

effects of the non living parts of the environment

light, temperature, water availability

climatic factors

effects of the weather

biotic environment

effects of the living community

predation, disease, competition

topographic factors

angle and aspect of slope

edaphic factors

associated with soil

texture, pH, temperature

natality

ways organisms increase their numbers

density dependent factor

affects the population more if the population is greater

density independent factor

factor doesnt depend on the size of the population

carrying capacity

maximum population of a species in a given area

estimating percentage cover in a quadrat

count the square if the plant covers half or more of the sqaure

percentage frequency in a quadrat

count the squares that contain the plant being sampled

plant density in a quadrat

count how many individual plants are present within the quadrat

work out a mean

work out mean number of individual plants per metre squared

conditions needed for a t test

results should show a normal distribution

null hypothesis

there is no significant difference between the two means

gross ecological efficiency

the rate at which energy passes into animals at each trophic level

how to calculate gross ecological efficiency

energy entering next trophic level/ energy entering previous trophic level X 100

reasons why energy is not converted to plant organic material

unsuitable wavelength for photosynthesis

reflected

travels through the leaf

gross primary production GPP

rate at which autotrophs synthesise organic material

net primary production NPP

organic material available to consumers

NPP = GPP - Respiration

net secondary production

the rate at which consumers convert food into their own biomass after accounting for energy lost through respiration

pyramid of energy

shows energy entering each trophic level

shows that the rate of energy flow decreases at each trophic level

succession

change in structure and species composition of a community over time

seral stage

each seral stage changes the environment to make it more suitable for other species

climax community

a stable community that has reached an equlibrium with its environment so no further changes occur

primary succession

the change in structure and species composition of a community that has not previously been colonised

secondary succession

the changes in a community following disturbance or damage to a habitat

intraspecific competition

competition between individuals of the same species

interspecific competition

competition between individuals of different species

saprophytes

bacteria and fungi

cause decay by relasing enzymes onto the dead animal or plant

detritivores

speed up decay by feeding on dead or decaying material

e.g earthworms, maggots and woodlice

carbon sinks

places in the environment where carbon can build up

carbon processes

move carbon from one sink to another

putrefaction

saprophytic bacteria metabolise nitrogen containing organic matter in dead organisms, faeces and urine to release NH4+

Nitrification

Nitrosomonas under aerobic conditions convert ammonia to nitrites

Nitrobacter convert nitrites to nitrates

nitrogen fixation

Nitrogen fixing bacteria (azobacter and rhizobium) convert atmospheric nitrogen into ammounium ions

denitrification

Anaerobic denitrifying bacteria (pseudomonas) convert nitrates and ammounium ions to atmospheric nitrogen

2 human activites that increase CO2 levels

deforestation
burning fossil fuels

consequences of global warming

melting of polar ice caps

extinction

extreme weather

ways to reduce carbon footprint

recycling

using less fossil fuels

planting trees