DIVERSITYChristia Swan

TO COME DIVERSITY RELATIONSHIP OF DIVERSITY &

STABILITY DIVERSITY INDEX MICROCLIMATES USING QUADRANTS

DIVERSITY DIVERSITY is all about how many

different species there are in an ecosystem.

Diversity is the number and variety of organisms found within a specified geographic region.

In total about 1.5 million species have been described

However, the total number of species on Earth may be as high as 10 million

DIVERSITY AND STABILITY ECOSYSTEMS with a large diversity of

species tend to be more stable than those that are less diverse

Stable ecosystem1. Resistant to change2. If disrupted, return to original state quickly

1. I.E. Climate extremes, pest and disease over a long period

LOW DIVERSITY Predator species don’t have much

choice of prey Prey species is reduced or wiped out

› Predator species will be at risk

MONOCULTURES Agricultural areas where only one crop

is grown› COTTON FIELDS

Artificially low diversities

EXTREME ENVIRONMENTS TUNDRA, DESERTS, SALT MARSHES,

AND ESTUARIES› Low diversities

AREAS OF LOW DIVERSITY Plant and animal populations are

mainly affected by abiotic factors ABIOTIC FACTORS:

› Nonliving components that effect the living organisms

› For examples: Radiation Temperature Water

HIGH DIVERISTY Predator species will have a large

selection of possible prey species One of the prey species is wiped out

› Still plenty of other species that predators can eat

MATURE, NATURAL ENVIRONMENTS

Old, oak woodlands Environmental conditions aren’t too

hostile Affected by biotic factors BIOTIC FACTORS:

› Of or relating to life› For example:

Plants, animals, fungi, bacteria

DIVERSITY INDEX How diversity is measured Could just count up the number of

species› This takes no account of the population

size of each species› Species that are in an ecosystem in very

small numbers shouldn’t be treated the same as those with bigger populations

DIVERSITY INDEX AN equation for diversity that takes

different population sizes into account. To calculate the diversity index of an

ecosystem› d = N(N-1) / ∑ n(n-1)› Where...

N= Total number of organisms of all species n= Total number of one species ∑= ‘Sum of’ (i.e. added together)

DIVERSITY INDEX Higher the number the more diverse

the area is› If all the individuals are of the same

species (i.e. no diversity) the diversity index 1

MICROCLIMATES Small areas where thee abiotic factor

are different from the surrounding area.› The underneath of a rock

Different microclimate than the top surface Cooler and more humid

Provides a slightly different habitat that will suit certain species

Variety of microclimates can support a high divesity

LET’S SEE IF YOU GET IT

•3 different species of flower•11 organisms altogether•3 red•5 yellow•3 purple•Diversity index•d=N(N-1) / ∑n(n-1)•d=11(11-1) / 3(3-1) + 5(5-1) + 3(3-1)•d=110/6+20+6•=3.44

When calculating the bottom half of the equation you need to work out the n(n-1) bit for each different species then add them all together.

MICROCLIMATES BASICALLY

› more microclimates = more species= higher diversity

YOU NEED TO KNOW HOW TO USE QUADRANTS

FACTORS TO CONSIDER ECOLOGISTS look at three key factors

when they’re working out diversities› Species frequency› Species richness› Percentage cover

SPECIES FREQUENCY

HOW ABUNDANT A SPECIES IS IN AN AREA

SPECIES FREQUENCY

TOTAL NUMBER OF DIFFERENT SPECIES IN AN AREA

PERCENTAGE COVER

HOW MUCH OF THE SURFACE IS COVERED BY A PARTICULAR PLANT

SPECIES› (NOT FOR ANIMALS THOUGH AS THEY MOVE AROUND TOO

MUCH)

USING QUADRANTS Measuring the three key factors use a

piece of equipment called a frame quadrant

FRAME QUADRANT› A square frame made from metal or wood

The area inside the square is the quadrant

QUADRANT FRAMES Laid on ground (or the river / sea/ pond

bed if it’s an aquatic environment) Total number of species in the quadrant

is recorded As well as the total number of

individuals of each species

RANDOM SAMPLING Not practical to collect data for a whole

area› Takes ages› Can be costly

Samples are taken instead Data samples are used to calculate the

figures for the entire area being studied

Random sampling avoids bias

AGAIN...SPECIES FREQUENCY

Measured by counting how many quadrants each species in and is given as a percentage

If a species was found in 5 out of 20 quadrant samples› The frequency would be 25%

PERCENTAGE COVER Measured by dividing the area inside

the quadrant frame into a 10x10 grid and counting how many squares each species takes up

Sometimes plants overlap so the percentage cover ends up being more than 100%

OH AND...SPECIES RICHNESS

Measured by counting up the total number of species found in all the samples

Assume that the number of different species in your sample is the same as the number in the whole area that you are studying

QUESTIONS FOR YOU What is meant by a ‘stable’

ecosystem? Give three examples of ecosystems

that are likely to be unstable? What is the difference between the

diversity index and species richness? Why do percentage cover

measurements sometimes add up to more that 100%?

QUESTIONS FOR ME

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