Population controlling etc. Flashcards
what is the definition of species
a group of similar organisms that can interbreed to produce fertile offspring using homologous pairs at meiosis
what is the definition of population
a group of organisms of a single species interbreeding and occupying a particular area (habitat)
what are population numbers dependent on?
birth rate
death rate
immigration (moving in)
emigration (moving out)
population will increase if…
birth rate + immigration is more than death rate + emigration
what is the definition of carrying capacity
the maximum population size that can be maintained over a period of time in a particular habitat
what types of infectious diseases can affect population growth
malaria, Aids/HIV, cholera, TB can be a factor in preventing population growth
how do humans change the environment for their benefit
deforestation - clear land for farming, buildings etc. increasing CO2 which results to global warming
fertiliser and pesticide use - reduces biodiversity
burning of fossil fuels - increase pollution
sewage use - pollution e.g eutrophication
hunting and fishing - increases endangered species and lowers fish stocks
increased industrialisation - greenhouse gases = global warming
what are organic molecules
molecules that contain carbon
examples of organic molecules in plants
cellulose, phospholipid bilayer, DNA, RNA, glucose, sucrose
what is a saprobiont
a decomposer of carbon molecules e.g. fungi/bacteria
how do fungi breakdown trees
through enzymes (lignin) which causes extracellular digestion
how do humans influence the carbon cycle?
respiration (take in oxygen, give out carbon dioxide)
burning fossil fuels - CO2
deforestation - CO2
what is a carbon store
rocks such as chalk, marble and limestone which is the build up of planktons that can’t be broken down and respired.
how does deforestation affect the carbon cycle
less photosynthesis meaning less oxygen
what could happen to the carbon in organic molecules in plants
they could be ingested, digested or absorbed or the plant could die.
what does decomposition mean
release nitrogen compounds/ammonia from dead bodies/faeces/urine
what does nitrogen fixing mean
converting nitrogen gas into soluble nitrogen containing compounds
what does denitrifying mean
convert nitrates into nitrogen gas, often found in anaerobic soils
what does nitrifying mean
converting ammonium compounds into nitrites then into nitrates
what bacterias are found in the nitrogen cycle?
nitrosomonas
nitrobacter
azotobacter
rhizobium
what does nitrosomonas do?
converts ammonium ions to nitrites (a nitrifying bacteria)
what does the nitrobacter do
converts nitrites to nitrates (a nitrifying bacteria)
what does azotobacter do
a nitrogen fixing bacteria that lives free in the soil
what does rhizobium do
a nitrogen fixing bacteria found in lumps on the roots of legume plants called root nodules
