17 Selection and Evolution Flashcards
Outline how bacteria become resistant to antibiotics
1 Random mutation
2 Directional Selection
3 Antibiotic acts as selection pressure
4 Bacteria with mutation have selective advantage
5 Fitter bacteria reproduce
6 Using binary fission
7 Resistance alleles frequency increases
Explain why natural selection occurs in populations
1 (populations) can produce many offspring / AW;
2 genetic variation occurs (in populations) / described;
3 ref. mutations / sexual reproduction / gamete formation / random fertilisation ;
4 ref. competition qualified ; e.g. mates / food / resources
5 ref. selection pressure ;
6 some individuals have advantageous, adaptations / phenotype / traits / AW;
7 (so) they, survive / reproduce / have a selective advantage;
8 (so) pass on their advantageous allele(s) ;
9 (so) the (advantageous) allele frequency increases ;
Discuss how DNA sequence data can show evolutionary relationships between species
1 Compare and identify differences in DNA
2 Many DNA differences means that they have a distant common ancestor
Outline how vigorous, uniform varieties of maize were developed by selective breeding
1 breed/cross, plants with desired (named) characteristics;
2 breed, better /best, offspring, repeatedly / for many generations;
3 Inbreeding (similar genotypes are used as gametes) results in higher homozygosity and hence reduced growth and survivability
4 Outbreeding (breeding individuals that are not closely related) increases heterozygosity and hence improves growth and survivability
5 (gives) hybrid vigour / heterosis / outbreeding enhancement (in offspring) ;
6 Farmers must achieve both homozygosity and heterozygosity
7 Farmer must therefore inbreed to produce homozygous offsprings
8 Different varieties of homozygous can be bred together to produce different hybrids that serve different purposes;
9 F1 have, same genotype / uniform phenotype;
Explain how geographical isolation can lead to evolution
1 geographical isolation / barrier qualified ; Ignore separation
2 no, interbreeding / gene flow:
Ignore reproductive isolation here (needs to be late on in process)
3 different, environmental (conditions) / selection pressures ;
4 random / different, mutations ;
5 different, alleles selected for / gene pool/ changes in allele frequency;
6 populations have different, morphological/ physiological/behavioural, features;
7 after, a long time / many generations, reproductive isolation occurs / cannot interbreed to produce fertile offspring ;
8 allopatric (speciation) ;
Outline how practical techniques can be used to test hypothesis between two species in terms of evolutionary relations
1 obtain/ use, blood / cells / tissue / DNA ;
2 from, both species;
3 use PCR to, replicate / amplify, DNA ;
4 use, electrophoresis (described) / DNA profiling / DNA fingerprinting,
to see genetic differences / compare the banding (patterns) ;
5 sequence DNA and, count / identify, (percentage) difference / similarity
or
sequence DNA and compare the, nucleotide / base, sequence ;
6 use, genome / DNA, microarray; R for gene expression
7 ref. to bioinformatics / database / (computer) software;
8 similarity indicates, close relationship / more recent split;
if they can breed to produce (viable) offspring (they are closely related);
Explain how bottleneck effect may affect allele frequencies in populations
1 these features are controlled by, genes /alleles;
2 ref. to genetic drift ;
3 (population went through a) bottleneck;
4 low / reduced, number of alleles / genetic diversity / genetic variation / genetic polymorphism (in population) ;
A some alleles lost
5 inbreeding;
6 low/reduced, heterozygosity or high / increased, homozygosity ;
Describe the genetic basis of continuous variation
1 different alleles at a single gene locus have small effects (on the phenotype);
2 different genes may have an, additive / combined, effect (on the phenotype) ;
3 ref. to multiple genes / polygenes / description ;
Describe how selective breeding can be used to improve the milk yield of diary cattle
1 (humans) choose / cross / breed from, females / cows / cattle, with, good / high, milk yield;
2 (humans) choose / cross / breed from, males / bulls, with, mother / sisters / daughters, with, good / high, milk yield;
3 (humans) choose / cross / breed from, desirable offspring ;
4 continue / repeat, for (several) generations ;
5 allele(s) for, high milk yield / desired trait, passed on ;
6 increase in frequency of, good / best/ high yield, allele(s) ;
7 artificial insemination / A.. ;
Explain what is meant by disruptive selection
1 mean / mode / median / average / intermediate, selected against / not favoured / less fit/ die;
2 (both) extremes, selected for / favoured / more fit / survive / reproduce ;
3 bimodal distribution ;
4 diversifying selection
5 causes / maintains, polymorphism / genetic diversity ;
Explain what is meant by stabilising selection
1 individuals in a population with, intermediate phenotypes / AW, more likely to, survive / reproduce
or
individuals in a population with, intermediate phenotypes / AW, are selected for ;
2 individuals in a population with extreme phenotypes, die
or
individuals in a population with extreme phenotypes are selected against ;
3 no change in environment ;
Explain what is meant by genetic drift
1 Change in allele frequency by chance/random
or
description of alleles not passed onto the next generation ;
2 larger influence in smaller population / AW ;
State the conditions for Hardy-Weinberg principle to apply
1 no migration
or
no flow of, alleles / genes, into / out of, the population ;
2 population is isolated / described; e.g. separated by geographical barrier
I ref to island alone
3 random mating is occurring ;
4 organisms move around island / AW;
5 large population ;
6 high reproductive rate / no predators ;
7 organisms diploid;
8 have two different alleles (for the gene) / heterozygous ;
Explain what is meant by discontinuous variation
1 Discrete categories of phenotypes
2 No intermediates
3 Not affected by environment
