7.4 POPULATIONS IN ECOSYSTEMS Flashcards
define
community
all the different species that live in one area and interact with each other
define
ecosystem
all living organisms found in one area, combined with non-living aspects of their environment
describe
biotic and abiotic factors
biotic = living features of an ecosystem e.g. predators, disease
abiotic = non-living features of an ecosystem e.g. light, temperature
define
habitat
the place where an organism lives within an ecosystem
define
niche
the role of a species within its habitat, consisting of both its biotic interactions e.g. what it eats, and abiotic interactions e.g. time of day it is active
define
carrying capacity
the maximum size of population an ecosystem can support
name
4 abiotic factors affecting population growth
- temperature
- light
- pH
- water/humidity
contrast
intra- and inter- specific competition
intra = competition between organisms of the same species
inter = competition between organisms of different species
state
resources organisms compete for
food, water, shelter, minerals, light, mates (intra)
describe
pattern of typical predator-prey relationship
in terms of population change
- prey is eaten by predator, resulting in predator population increasing and prey population decreasing
- fewer prey means increased competition for food, so predator population decreases
- fewer predators means more prey survives, and the cycle begins again
explain
use of quadrats for estimating population size
- placed on grid coordintes or at intervals along a transect
- results reported as either percentage cover or frequency
- for slow-moving or non-motile organisms
explain
use of mark-release-recapture for estimating population size
- sample of species captured, counted, marked and released back into the same area they were caught
- after a specified period of time, another sample is captured and counted for marked and unmarked organisms
- for motile organsims
state
equation for mark-release-recapture
estimated population size = (t1 x t2)/r
t = total captured
r = recaptured
state
assumptions made by mark-release-recapture
- few births
- marked individuals distribute evenly
- few immigrations
- method of marking does not affect survival
- mark doesn’t come off
explain
why ecosystems are descibed as dynamic
- populations constantly rise and fall
- any small change can have a large effect
- biotic and abiotic factors may alter the conditions of the ecosystem
define
primary succession
where an area previously devoid of life is colonised by a community of organisms
summarise
process of primary succession
- pioneer species can survive harsh conditions & colonise the area
- pioneer species change abiotic factors in the environment e.g. decomposition adds nutrients to ground
- overtime, allows complex organisms to survive
define and explain
climax community and how its reached
the final stage of succession where the ecosystem is balanced and stable
* reached when the soil is rich enough to support large trees or shrubs and the environment is no longer changing
describe
alterations a species may have to their environment in succession
- may impove the environment to make it more suitable for other species
e.g. large root systems keeping dunes immobile - may worsen the environemnt to make it less suitable
define
conservation
protection and management of species and habitats, in order to maintain biodiversity
explain
how succession is managed to aid conservation
- succession prevented to preserve an ecosystem at a certain point ( plagioclimax )
