biodiversity and farming Flashcards
what is biodiversity?
variety of living organisms (variety in the living world)
what are the three main components of biodiversity?
genetic diversity
ecosystem diversity
species diversity
what is a community?
all populations of different species that live in an area.
what is species richness?
the number of different species in a community.
what does an index of diversity do?
describes the relationships between:
- the number of species in a community
- the number of individuals in each species
suggest why index diversity is more useful than species richness.
also takes into account the number of individuals in each species so takes into account that same species may be present in small or high numbers.
what does the N represent in the index of diversity formula?
total number of organisms of all species.
what does the n represent in the index of diversity formula?
total number of organisms of each species.
list the steps involved in calculating index of diversity.
calculate total number of organisms (N) if not given.
multiply N by (N-1)
for each species multiply the number of organisms (n) by (n-1)
add up all the values of n(n-1) to get the sum of n(n-1)
divide N(N-1) by sum of n(n-1)
describe how index of diversity values can be interpreted.
high - many species so more diverse (high species richness)
low - habitat dominated by a few species.
what is species diversity?
the number of different species and number of individuals of each species within one community.
what is the main threat of biodiversity and what causes this?
habitat loss - due to agriculture, urban development, forestry, mining, pollution, over fishing.
why maintain biodiversity?
- species provide crops, fibres and medicines.
- we should protect out environment.
- loss of species and genes affects the survival of others in the ecosystem.
explain how some farming techniques reduce biodiversity.
removal of hedgerows and woodland, monoculture, use of herbicides to kill weeds - reduces variety of plant species, so fewer habitats, and less variety of food sources.
use of pesticides to kill pests - predator population of pest decreases.
what is standard deviation?
a measure of the spread of data around the mean (variation around the mean)
what does a narrow spread (curve) of measurements show/mean?
if graph/curve has a narrow spread of measurements it means the measurements in the sample are very similar, whereas in a much broader spread of measurements it means there was more variation in the measurements of the sample
- as a result, the greater the variation within the sample, the larger the standard deviation.
what does it mean if standard deviations overlap?
any difference between the two are not significant (could be due to chance)
