3.4.7 investigating diversity Flashcards
Variation
Differences between individuals within a species (intraspecific variation) or between different species (interspecific variation)
Result of:
- genetic factors e.g. different alleles
- environmental factors
Combination of both
Continuous variation
No distinct categories
Data tends to be quantitative
Controlled by many genes
Strongly influenced by environment
E.g height
Discontinuous variation
Distinct, discrete categories
Data tends to be qualitative
Controlled by a signed gene or a few genes
Unaffected/not strongly influenced by environment
E.g. blood groups
Genetic diversity can b made by comparing
Frequency of measurable/observable characteristics
- indicates genetic diversity as it’s based on the fact that different alleles determine different characteristics
- the higher the variety of characteristics, the higher the variety of alleles of that gene and hence the higher the genetic diversity
Base sequence of DNA and mRNA
Amino acids sequence of proteins encoded by DNA and mRNA
Early estimates of genetic diversity
Made by looking at frequency of measurable/observable characteristics in a population
Limitations:
many observable characteristics coded for by more than one gene (polygenic)> vary continuously > difficult to distinguish one from another
Characteristics could be modified by environmental conditions rather than different alleles
Gene technologies
Made it possible to directly obtain DNA sequences
Can be used to give more accurate estimates of genetic diversity within a population as:
- different alleles of the same gene have slightly different base sequences
= comparing DNA base sequences of same gene in different organisms in a population > finding out how many alleles of that gene in a population - different alleles transcribed into slightly different mRNA base sequences and may produce polypeptides with slightly different amino acid sequences which can also be compared
Taking a representative sample
Large sample size
- minimise effects of chance
- anomalies have less influence and can be identified
Analyse results with a named statistical test
- see if variation observed is or isn’t due to chance
Quantitative investigations
Taking a representative sample
Calculating a mean
Interpreting the mean values and their standard deviations
Calculating a mean of the collected data and their SD
Mean = sum/total
SD
- shows spread of values around the mean
Interpreting the mean value and their SD
Mean > can show if there is variation/differences between samples
- useful for comparison, but provides no info about the range
SD
- the higher the value, the higher the variation
- if standard deviation overlaps, any difference between 2 may be due to chance
Random sampling exam q
Create a grid by laying out 2 tape measures at right angle
Use a random number generator to generate coordinates
Place quadrant at coordinates and count organism in quadrat
Repeat at least 30 times, calculate mean
Work out density - mean no organism/size of quadrat
Belt transect systematic sampling method
Place tape measure along light gradient
Place a quadrat down at regular intervals and measure light intensity each time
Estimate percentage cover of organism in each quadrat
Do repeats at each interval and calculate mean
See how mean percentage cover and light intensity relate
Mark release recapture method
Capture organism by () in controlled manner
Count number captured
Mark them with discrete non-toxic material
Release them
Allow time for them to evenly distribute back into population
Recapture organism with same method
Count how many are marked and captured
Estimate population - (total in 1st sample x total in 2nd sample) / total marked in 2nd
Mark release assumptions
Marked organisms distributed evenly back into population
Population constant (no immigration/emigration)
Population constant (no deaths/births)
Mark is non-toxic and doesnt change vulnerability
Mark is not rubbed off
