populations and ecosystems content Flashcards
population
group of organisms of the same species in the same habitat.
habitat
part of ecosystem where certain organisms live
community
all populations of all species living in the same area at the same time.
ecosystems
can range in size from very small to very large.
community and non living aspects of environment (biotic and abiotic factors)
niche
an organisms role within the ecosystem including their position in the food web and habitat.
each species has its own niche governed by adaptations to biotic and abiotic factors.
carrying capacity
maximum population size that an ecosystem can support.
abiotic factors
non living conditions of an ecosystem
biotic factors
impact of interaction between organisms.
factors influencing population size
biotic and abiotic factors
inter and intraspecific competition
abiotic factors
e.g. light intensity, carbon dioxide and oxygen concentration, temperature, pH, soil conditions.
plants and animals are adapted to the abiotic factors in their ecosystem due to natural selection over many generations.
the less harsh the abiotic conditions e.g. plenty of light and water, the larger the population size and range of species.
interspecific competition
competition between different species for resources in short supply e.g. a habitat, food and water.
organisms that are better adapted to their environment are more likely to survive.
intraspecific competition
competition between organisms of the same species for resources and a mate.
fitter individuals have more energy to perform impressive courtship ritual
fur or feathers to attract mate.
competition for a mate is due to courtship rituals being similar/ the same
predator prey relationship
graph shows relationship between predators and prey in a food web.
regardless of species- same pattern-
decrease in prey population first, lag time and then decrease in predator population
there is always more prey than predators
size of predator and prey population fluctuate.
what is succession?
changes in ecological community over time
seral stage
final seral stage
eaech stage is called a seral stage.
the final seral stage is the climax community.
primary succession
pioneer species colonises bare rock/sand
e.g. lichen are adapted to survive in harsh abiotic conditions and when they die and decompose, there is a thin layer of soil, hummus added.
this makes the abiotic factors less harsh, enabling moss and other small plants to colonise- further increases depth and nutrient content of the soil.
the pattern repeats and the environmental conditions continue to change.
smaller plants colonise.
-organisms make changes to abiotic environment- less harsh and greater biodiversity.
final seral stage- climax community- dominated by trees.
secondary succession
succession is disrupted and plants are destroyed
succession starts again but as soil is already created, it does not start from bare rock seral stage.
conservation of habitats
destruction of habitat, especially due to human activity
species do not have enough food or resources- may become extinct
to conserve habitats, succession is often managed.
conservation of habitats
habitats are being destroyed, especially due to human activity so management of succession is needed to conserve habitats.
by maintaing each seral stage and preventing the climax community- this conserves a wide range of habitats and hence wide range of species
conflict between balancing human needs and conservation for sustainable use of resources e.g. coppicing from forests for furtniture/timber for fuel, while still allowing the tree to survive.
how can we ensure that the sample is representative?
large sample
random sampling e.g. using random number generator to generate coordinates
what is a transect line used for?
to look at change over an area
what are the advantages of sampling?
time efficient
if conducted correctly, more efficient.
what type of sampling should be used?
for slow/non moving organisms- quadrat
moving organisms- mark, release, recapture method.
unequal distribution
equal distribution
unequal distribution- transect line
equal distribution- random sampling
how to measure frequency for equal distribution
-use a grid sytem
-use random number generator to generate coordinates
-place quadrats at coordinates and measure frequency
-multiply by e.g. area of field
-large sample/repeat and calculate average.
types of transects
belt transect- quadrats placed at every position along tape measure
interuppted belt transect- quadrats placed at regular intervalas along tape measure.
methods to estimate abundance of species.
local frequency- % of squares in quadrat where species is present
density- number of species in a given area
-percentage cover- % of ground surface occupied by species.
things that need to be considered when marking organisms during mark, release, recapture method
-not toxic
-must not increase predation chances
-must not reduce reproduction chances.
why may the estimate not be accurate?
the esimate of population size may not be accurate in mark, release, recapture as it makes the following assumptions:
-population size is constant (no birth, death or migration)
-animals redistribute evenly.
