Topic 17: Selection and Evolution Flashcards
Definitions I:
(a) Variation
(b) Natural selection
(c) Speciation
(a) Variation: Differences in traits among individuals. (1 mark)
(b) Natural selection: Survival of best-adapted traits. (1 mark)
(c) Speciation: Formation of new species. (1 mark)
In humans, explain phenotypic variation with eye colour. [2 Marks]
Eye colour from genes (1 mark); Sun exposure alters shade (1 mark). (2 marks)
Define discontinuous and continuous variation in a dog population. [2 Marks]
Discontinuous: Distinct traits, e.g., coat type (1 mark); Continuous: Range, e.g., weight (1 mark). (2 marks)
In pea plants, explain the genetic basis of pod colour and height variation. [3 Marks]
Pod colour: Single gene, discontinuous (1 mark); Height: Multiple genes, continuous (1 mark); Alleles control both (1 mark). (3 marks)
Use a t-test to compare leaf sizes of two oak tree samples. [3 Marks]
t = (mean1 - mean2) / √(s²/n), compare sizes (1 mark); Calc shows difference (1 mark); Significant if t > critical (1 mark). (3 marks)
In a bird population, explain how natural selection affects beak size. [3 Marks]
Birds with optimal beaks survive (1 mark); Reproduce, pass alleles (1 mark); Beak size shifts (1 mark). (3 marks)
In fish, explain how temperature acts as a directional selection force. [2 Marks]
Warmer water favours smaller fish (1 mark); Larger die, alleles shift (1 mark). (2 marks)
Outline how antibiotic resistance evolves in E. coli. [2 Marks]
Resistant bacteria survive antibiotics (1 mark); Reproduce, increase resistance alleles (1 mark). (2 marks)
In a rabbit population, explain how genetic drift alters fur colour alleles. [3 Marks]
Random loss of alleles, e.g., bottleneck (1 mark); Founder effect shifts frequencies (1 mark); Fur colour changes (1 mark). (3 marks)
Use Hardy-Weinberg to calculate allele frequencies in a human population (p=0.7). [3 Marks]
p=0.7, q=0.3; p²+2pq+q²=1 (1 mark); 0.49 AA, 0.42 Aa, 0.09 aa (1 mark); Stable population (1 mark). (3 marks)
In maize, outline inbreeding and hybridisation for uniformity. [3 Marks]
Inbreed for purity (1 mark); Hybridise for vigour (1 mark); Uniform maize results (1 mark). (3 marks)
Describe selective breeding principles in a wheat field. [2 Marks]
Breed plants with desired traits (1 mark); Offspring inherit traits (1 mark). (2 marks)
Explain how selective breeding improves milk yield in dairy cows. [4 Marks]
Select high-yield cows (1 mark); Breed over generations (1 mark); Genes amplify yield (1 mark); Milk increases (1 mark). (4 marks)
In finches, outline Darwin’s evolution theory for beak diversity. [4 Marks]
Beak variation exists (1 mark); Food scarcity selects fit (1 mark); Survivors reproduce (1 mark); New species form (1 mark). (4 marks)
Discuss how DNA sequencing shows evolutionary links in primates. [2 Marks]
Similar DNA shows close relation (1 mark); Divergence tracks evolution (1 mark). (2 marks)
In butterflies, explain allopatric and sympatric speciation. [4 Marks]
Allopatric: Geography splits, genes diverge (1 mark); Sympatric: Behaviour isolates (1 mark); New species form (1 mark); Genetic isolation drives (1 mark). (4 marks)
