7c (populations in ecosystems) Flashcards
what is an ecosystem?
all the organisms living in a community plus all the abiotic conditions in the area which they live
biotic factors
living features of an ecosystem eg presence of predators/ food
abiotic factors
non-living features of an ecosystem eg temperature and soil
what is a habitat?
the place where an organism lives within an ecosystem
what is a niche?
the role of a species within a habitat eg what it eats, where and when it feeds
what does the niche that a species occupies include?
biotic interactions- eg organisms it eats and is eaten by
abiotic interactions- eg temp range an organism can live in, time of day its active
how many species can occupy a niche?
only one
may look like 2 occupy the same but therell be slight differences
what happens if 2 species try to occupy the same niche?
compete each other
one will be more successful until only 1 species is left
what is an adaptation?
feature that a member of a species has that increases chance of survival and reproduction
can be behavioural, physiological, anatomical
what is natural selection?
organisms with better adaptations are more likely to survive, reproduce, pass on advantageous allele so freq of this allele increases in the population
examples of adaptions to abiotic factors
examples of adaptations to biotic factors
what is a population?
all the organisms of one species in a habitat
what is a communtiy?
populations of diff species in a habitat
what is population size?
total number of organisms of one species in a habitat. number changes over times because of effect of various factors
what is carrying capacity?
max stable population size of a species that an ecosystem can support
varies as a result of biotic/abiotic factors
what abiotic features affect population size?
amount of light, water, space available, temp, chemical composition of surroundings
when abiotic factors are ideal, organisms grows quicker and reproduces more successfully
what are biotic factors that affect population size?
interspecific competition- organisms of diff species competing for same resources so availability reduces so less energy for reproduction. one may be better adapted
intraspecific competition- organisms of same species compete for resources. cyclical change in pop size around the carrying capacity. increases above, then more competition so decreases so plentiful resources etc
predation- organism kills and eats another. pop of predator and prey is interlinked
investigating population growth of bacteria
what is abundance?
how can it be estimated?
what are other measures of abundance?
number of individuals of one species in a particular area
count no of individuals in sample taken
frequency, % cover
what is distribution?
where a particular species is within the area youre investigating
how to take a random smaple?
choose area to sample
sample should be random to avoid bias (use random no generator to get a coordinate)
use appropriate technique to take sample of pop
repeat to reduce likelihood results are due to chance
take mean and multiply it by size of whole area to find mean no of individuals for whole area
what is a running mean?
find mean each time you collect a new sample. when it no longer changes, data should be realistic
when to use quadrats, transects, traps?
quadrat, transects for non-motile organisms
traps for motile organisms
transects- see how distribution changes
how to use a quadrat?
- Use a grid to divide the area into squares
- use a random number generator to find coordinates to place quadrat (removes bias)
- count the frequency in the quadrat
- use a large sample and calculate a mean
what are transects for?
what are the 2 types?
find distribution across an area
belt- quadrats placed next to each other along transect to work out species freq and % cover along transect
interrupted belt transect- place quadrat at reg intervals
what is mark-release-recapture?
how do you carry it out?
used to measure abundance of more mobile species
1) capture sample of species and count them
2) mark them in harmless way
3) release back into habitat
4) allow to reintegrate and take second sample
5) count how many of second sample are marked
6) use equation
population size= (no. in 1st sample x no. in 2nd sample) / no. marked in 2nd sample
assumptions of mark-release-recapture
- proportion of marked: unmarked in 2nd -sample is same as whole pop
- marked distribute themselves evenly
- definite boundary- no migration
- no changes in pop size due to births/deaths/migration
- method of marking isnt toxic/ doesnt make them more liable to predators by making them more visible/ ill
- mark/label is not rubbed off/lost
ethics of mark-release-recapture
treat organisms carefully
handle as little as poss
keep as short time as poss
dont paint bright colours (attract predators)
dont destroy habitat
dont use toxic markers
measuring pH
what is succession?
process by which an ecosystem changes over time
happens in stages at each of which, plant/animal communities slowly change environmental conditions
what is primary succession?
happens on land thats been newly formed/ exposed eg where a volcano has erupted or sea level has dropped
no soil/ organic material to start with
happens over hundreds of years
what is the pioneer stage of succession?
species colonise a new land surface
eg lichen, marram grass, shrubs of calligonum genus
seeds/ spores blown in by wind and begin to grow
abiotic conditions are hostile (limited H2O, few minerals/ nutrients, light intensity, wind, rain, fluctuating temp) so pioneer species only able to grow as theyre adapted to harsh conditions
what happens to pioneer species and after this?
they die and are decomposed which forms basic soil so conditions are less hostile (nutrients, soil can retain H2O) so new organisms w diff adaptations can grow
these die and abiotic factors change again
nitrogen-fixing bacteria turn nitrogen from air into ammonia to be used by plants
what happens in later stages of succession?
at each stage, diff plants/ animals that are better adapted to improved conditions move in and out-compete previous organisms so become dominant species (cause the most change to abiotic environ)
ecosystems become more complex, biodiversity increases, abiotic conditions become less hostile, biomass increases
what is a climax community?
when the ecosystem is supporting the largest and most complex community of plants and animals that it can. its in a steady state
what is secondary succession?
happens on land thats been cleared of plants but soil remains eg after forest fire/ deforestation
pioneer species are larger shrubs as soil is present
takes less time than primary succession
what is the human impact on succession?
can stop climax community from developing- plagioclimax is when succession is stopped artificially
what is the climactic climax?
the climax community for a particular climate
common features of succession
- abiotic environment becomes less hostile
- leads to greater no and variety of habitats/ niches
- leads to increased biodiversity (but decrease at climax as dominant species out-compete pioneer species)
- more complex food webs
- increased biomass
what is conservation?
protection and management of species and habitats in a sustainable way
it is a dynamic process as it needs to be adapted to constant changes in ecosystems
what does sustainable mean?
enough resources taken to meet needs to people today wo reducing ability of future gens to meet their own needs
why are there conflicts in conservation?
balance needs to be found between human needs and conservation
what are some examples of conservation methods?
management of succession- to preserve an ecosystem in its current stage. (done by allowing grazing, lighting managed fires)
seed banks- store of seeds from diff species in case it becomes extinct. can store seeds anywhere for long time but need to test if they can still grow into a plant- £, time consuming
captive breeding- breeding animals in controlled environments to increase numbers of endangered species
fishing quotas- limit amount of certain fish that can be caught- prevent extinction
protected areas- eg national parks/nature reserves- protect habitats/species by restricting urban development/ farming
evaluating evidence on conservation
conflicting evidence
belt transect
line transect
belt- place a quadrat down at reg intervals. finds density
line- organisms that touch the line
what is the competitive exclusion principle?
2 species cannot occupy the same niche in a habitat
