Topic 7 - Ecology and Material Cycles Flashcards
population
total number of organisms of one species living in habitat
community
total number of organisms of all species living in a habitat
ecosystem
a community of organisms along with abiotic parts of their environment
what is interdependence?
when species in an ecosystem depend on each other for resources
- a change in population of one species can have a big effect on another species
mutualism
a relationship between two organisms from which both benefit
parasitism
a relationship between two organisms from which the parasite takes what it needs but host doesn’t benefit
abiotic factor
- a non living factor that affects the population of species and therefore the ecosystem
biotic factor
- a living factor that affects the population of species and therefore the ecosystem
4 examples of abiotic factors
- temp
- light intensity
- amount of water
- level of pollution
competition
when organisms within a community are in competition for limited resources so they can reproduce and survive
predation
as the population of prey increase the population of predators increase
as population of predators increase the population of prey will decrease
what is meant by the distribution of organisms?
where in the ecosystem that organism is mostly found ( which habitat )
2 main ways to study distribution of organisms
- quadrats ( random block sampling )
- transects
what are quadrats?
- a square frame enclosing a known area
- divided into smaller sub-squares making it easier to count organisms
Method 1 : Quadrats
- divide area into grid and use RNG to pick random co-ordinates
- place a quadrat down on that co-ordinate within first sample space
- count abundance of species within the quadrat
- repeat steps 1- 3 for that sample space and record mean for the s.s
- repeat above steps for other sample spaces
when do you use transects?
when abiotic factors change gradually across a habitat which is an environmental gradient
Method 2 : Transects
- mark out a line ( environmental gradient ) in the sample space using a tape measure
- place quadrats along the line and count abundances of organism as you go along
- record other relevant abiotic factors
- repeat above steps placing quadrats next to each other in a line
energy transfer in food chains
energy is transferred through food chains when organisms eat the biomass of other organisms.
how is energy lost from food chains?
- at each trophic level, animals need to respire to transfer energy to life processes
- energy transferred to surroundings by heat
- undigested material lost in faeces
- not all of the organism is eaten like bones
why are shorter food chains better?
- more efficient for top consumers
- less energy is lost/wasted at each trophic level
- fewer t.l better
what is biodiversity? Why is it so important?
- variety of living organisms in an ecosystem
- ecosystems with a higher biodiversity can adapt to changes more easily
- biodiverse ecosystems have fewer species that rely on just 1 organism
3 ways humans reduce biodiversity
- eutrophication
- fish farming
- introduction of non indigenous species
explain why the sun is needed at the start of all food chains?
- it provides energy needed for producers / green plants
- (which are at the start of the food chain), to photosynthesise
- the plant produces biomass
- which is passed on through the food chain by animals eating each other
eutrophication (part 1: algal blooms )
- farmers put fertilisers which are rich in nitrates on their fields
- heavy rain can wash excess nitrate ions into rivers. this process is called leaching and causes eutrophication
- excess nitrates encourage algae to reproduce rapidly
- forms algal blooms which prevent light from reaching underwater plants
eutrophication (part 2: effects )
- without light, the underwater plants cannot photosynthesise and die and decompose
- microorganisms that feed on decomposing plants increase in no. and use up O2 in water
- organisms that need O2 for respiration ( e.g: fish) die
fish farming
breeding fish in holding nets in open water
how does fish farming decrease biodiversity?
- waste produced by fish can leak into open water causing eutrophication and death of wild species
- parasites spread quickly amongst the high population of fish and infect wild life
- predators are attracted to nets, trapped in them and die
introduction of non indigenous species
- non indigenous species compete with indigenous species for resources
- sometimes they are better and out-compete the indigenous species
- the indigenous species decrease in number and die out which reduces biodiversity
how can humans maintain biodiversity?
- reforestation
- conservation schemes
4 advantages of maintaining biodiversity
- protecting human food supply
- minimal damage to food chains
- providing future medicines
- ecotourism
what is food security?
- having sufficient nutritious and safe food to eat for everybody
4 factors that affect food security?
- increasing meat consumption/animal farming
- environmental change
- lack of sustainability
- new pests/pathogens
increasing meat consumption and animal farming
- people becoming wealthier so diets likely to change including more meat demand
- less energy + biomass every time you move up a stage in food chain
- for given m2 you cam produce lot more food by crowing crops rather than grazing animals
- risk of over-fishing wild fish so there won’t be enough in future
environmental changes caused by human activity
- burning fossil fuels releases CO2 which is greenhouse gas
- increasing levels of g.g causes global temp to rise causing global warming
- other human activity such as soil pollution
- may affect our ability to grow crops
new pests and pathogens
- pests and pathogens can cause damage to crops and livestock
- this reduces the yield and amount that can be sold as food
indicator species
- biological indicators that can tell us the effect of human activities on environment
- organisms very sensitive to their environment
indicator species used to assess water pollution
- some invertebrate species are very sensitive to concentration of oxygen in water
- stonefly larvae and freshwater shrimps indicators of clean water > O2
-bloodworms and sludge worms adapted to living in polluted environment so indicators of polluted water
indicator species used to assess air pollution
- can analyse type of lichen growing in environment
- sensitive to levels of sulphur dioxide in atmosphere
pros of indicator species
- simple and cost effective way of saying if area is polluted
cons of indicator species
- can’t give accurate figures for HOW polluted
- may be other factors other than pollution that affect their population
what three factors affect rate of decomposition
- temperature
- water availability
- oxygen
temperature
- warmer temp increases decomposition rate
- increase rate of microbial enzymes involved
- if it’s too hot decomposition slows down or stops because enzymes denatured
water availability
- decay takes place faster in moist environments ( > water availability )
- decomposers need water to survive and carry out biological processes
oxygen availability
- decay takes place faster when oxygen supply is plentiful
- micro-organisms need oxygen to respire aerobically
compost
decomposed organic matter that is used as natural fertilizer
- recycles nutrients back into soil
food preservation methods
- airtight cans
- storing food in fridge or freezer
- drying food
- vacuum packing
