3.4.7 Investigating Diversity

how can scientists determine evolutionary relationships between species?

comparing genetic diverisity dna determines proteins of an organism, including enzymes and proteins

what are the limitations of observable charactertistics?

• a large number of features are coded for by more than one genic - polygenic

• this means they are not discrete from one another but rather vary continuously

• differences may be the result of different environmental conditions rather than different alleles - eg diet influences height

what have the limitations of observable characteristics led to?

directly observing dna sequences rather than infering them uses gene technology

how is dna sequencing done?

routinely through automatic machnines data produced analysed by computers each nucleotide can be tagged with a different coloured fluorescent dye adenine is green thymine is red cytosine is blue guanine is yellow

how do we use base sequences of mRNA to measure genetic diversity?

the base sequence on mRNA are complementary to those of the strand of DNA from which they were made we can measure DNA diversity and therefore genetic diversity by comparing the base sequence of mRNA

how can comparing amino acid sequences be used to compare genetic diversity?

the sequence of amino acids in proteins is determined by mRNA which in turn is determined by DNA genetic diversity can be measured by comparing the amino acid sequences of their proteins

what is interspecific variation?

if one species differs from another

what is intraspecific variation?

variation between individuals of the same species

what is sampling?

taking measurements of individuals selected from the population of organisms being investigated

how can random sampling be carried out (to eliminate bias)?

divide the study area into a grid of numbered lines using random numbers from a table or generated by a computer obtain a series of coordinates take samples at the intersection of each pair of coordinates

how can the effect of chance be reduced?

using a large sample size - the more individuals that are selected, the smaller the probability that chance will influence the result and the less influence anomalies will have analysis of the data collected - by accepting that chance will play a part, the data collected can be analysed using statistical tests to determine the extent to which chance may have influenced the data

why may sampling measurements not be representative?

sampling bias - the selection process may be biased, unrepresentative choices may be made unwittingly or deliberately chance - individuals chose may be, by pure chance, not be representative

what is significant about the shape of all normal distribution curves?

have the same basic shape differ by two measurements - maximum height and its width

what is skewed distribution?

curve is shifted to one side

what is standard deviation?

a measure of the width of the curve it gives an indication of the range of values either side of the mean distance from the mean to the point where the curve changes from being convex to concave 68% = 1 S.D, 95% = 2 S.D

what is the normal distribution curve?

its bell shape is typical for a feature that shows continuous variation eg - height in humans the graph is symmetrical about a central value