3.5 population size and ecosystems Flashcards
Define population
an interbreeding group of organisms of the same species occupying a particular habitat.
Define birth rate
the reproductive capacity of a population; the number of new individuals derived from reproduction per unit time.
Define immigration
The movement of individuals into a population of the same species.
Define equilibrium species
Species that control their population by competition rather than by reproduction and dispersal
Define death rate
the number of deaths over a given period, usually a year, divided by the number of adults in a population.
Define carrying capacity
the maximum number around which a population fluctuates in a given environment
Define environmental resistance
Limiting factors cause environmental resistance preventing population growth
Define abiotic
a part of the environment of an organism that is non living e.g air (usually dencity independent)
Define biotic
A part of the environment that is living e.g pathogens, predators. (usually density dependent )
Define density dependent
their effect increases as the density of the population increases e.g depletion of food supply
Define density independent
the effect of these factors does not depend on the population density. the effect is the same regardless of the size of the population
Define intraspecific competition
between individuals of the same species
Define interspecific competition
between individuals of different species
Calculation of rate of growth is…
antilog5-antilog2 / no of days
Describe the carbon cycle:
- carbon found as co2 in atmosphere and dissolved in water
- co2 from atmosphere absorbed by green plants in photosynthesis
- enters consumers when they feed on plants and each other
How does co2 get into atmosphere?
- when organisms respire
- burning fossil fuels
- decomposers
carbons recycling pathway in the sea:
- marine organisms use carbonates to make shells
- when they die shells fall to ground forming limestone rocks
- carbon in these rocks return to atmosphere as co2 during volcanic eruptions or weathering
human impacts on the carbon cycle:
- combustion of fossil fuels
- deforestation as photosynthesis is reduced and the trees may be burned or left to decay which release co2
rising co2 levels leads to:
- global warming which is an increase of average global temp believe to be a consequence of the greenhouse effect
e.g polar ice melting and forest fires - climate change which is a consequence of global warming. Changes in climate patterns and extreme weather conditions- drought
people suffer from crop yield reductions and failed harvests, there is a use of drought tolerant crops
what is carbon footprint?
- the equivalent amount of co2 generated by an individual, product or service in one year.
we must reduce reuse recycle
Human impact on nitrogen cycle:
-farmers use pesticides to reduce damage to crops
-use nitrogen based fertilisers such as ammonium nitrate to increase plant growth
-plough and drain soil to improve soil aeration, favours aerobic processes of N-fixation and nitrification and inhibiting dentrification which is anaerobic, allowing air to reach plant roots as nitrates taken up by active transport requiring atp.
-manure + slurry- contains nitrogen and improves soil structure
consequence of using water- soluble nitrate fertilisers
- washed off into rivers increasing the ion content (eutrophication- artificial enrichment of aquatic habitats caused by run off fertilisers)
-increase in nitrates leads to algal bloom blocking light to aquatic plants - as plants die they form detritus which is decomposed aerobically using dissolved o2 in the water
- causing other aerobic organisms/ fish to die
- only anaerobic bacteria survive releasing ammonium into the water- toxic
to reduce fertiliser run off:
- apply when plants are actively growing so it’s readily used and doesn’t build up in soil
- not apply within 10m of watercourses
- dig drainage ditches to collect any run off
