2. distribution of organisms Flashcards
what is a biotic factor
living things that affect the distribution of organisms (e.g. competition for resources, grazing, predation, food availability and disease
what is an abiotic factor
non-living things which affect the distribution of organisms e.g. temperature, humidity, pH and light intensity.
what is competition
the struggle between individuals when resources are in short supply e.g. food, light, water etc…
describe low levels of grazing
slower growing plant species die as they are out-competed by vigorous grass species which will dominate the habitat (interspecific competition)
describe intermediate levels of grazing
vigorous growing plants are eaten resulting in slower-growing species gaining resources to survive. results in fast and slow growing plants which will increase biodiversity
describe high levels of grazing (overgrazing)
all plants are damaged - only vigorous growing plants (grass) will survive
what is a source of error and way of overcoming this error for light intensity
a source of error would be casting a shadow over the light meter
to overcome this error, do not stand between the sun and the light meter
what is a source of error and way of overcoming this error for soil moisture content and pH
for both of these abiotic factors a source of error would be moisture from previous reading left on the probe
to overcome this error, wipe the probe dry between measurements
what are indicator species
they indicate the quality of the environment/level of pollution by their presence or absence
examples of sampling traps
- pitfall trap
- tullgren funnel
- branch beating
- quadrat
when taking samples…
the samples must be representative of the ecosystem therefore an appropriate number of samples should be taken. this should provide more reliable results
