Presentation on theme: "Why did this happen?. LECTURE PRESENTATIONS For CAMPBELL BIOLOGY, NINTH EDITION Jane B. Reece, Lisa A. Urry, Michael L. Cain, Steven A. Wasserman, Peter."— Presentation transcript:
Evidence of selection by food source. Microevolution is a change in allele frequencies in a population over generations 1976 (similar to the prior 3 years) 1978 (after drought) Average beak depth (mm) 10 9 8 0
mummichog fish vary in a cold-adaptive allele along a temperature gradient 1.0 0.8 0.6 0.4 0.2 0 4644 4240 383634 32 Maine Cold (6°C) Latitude (ºN) Georgia Warm (21ºC) Ldh-B b allele frequency 30 HOW DID THIS COME TO BE?
Figure 23.10-2 Original population Bottlenecking event
The bottleneck effect is a sudden reduction in population size due to a change in the environment If the population remains small, it may be further affected by genetic drift Original population Bottlenecking event Surviving population
Gene flow and local adaptation Population in which the surviving females eventually bred Central Eastern Survival rate (%) Females born in central population Females born in eastern population Parus major 60 50 40 30 20 10 0 Central population NORTH SEA Eastern population Vlieland, the Netherlands 2 km
Figure 23.16 EXPERIMENT Recording of SC male’s call Recording of LC male’s call LC male gray tree frog SC male gray tree frog Female gray tree frog SC sperm Eggs LC sperm Offspring of SC father LC father Survival and growth of these half-sibling offspring compared RESULTS Time to metamorphosis Larval survival Larval growth NSD = no significant difference; LC better = offspring of LC males superior to offspring of SC males. Offspring Performance1995 1996 LC better NSD LC better (shorter) LC better (shorter) LC better
Figure 23.17 Distribution of malaria caused by Plasmodium falciparum (a parasitic unicellular eukaryote) Key Frequencies of the sickle-cell allele 0–2.5% 2.5–5.0% 5.0–7.5% 7.5–10.0% 10.0–12.5% >12.5%
Figure 23.8 80% C R (p = 0.8) (80%) (20%) Sperm 20% C W (q = 0.2) CRCR CWCW (80%) (20%) CRCR CWCW Eggs 64% (p 2 ) C R 16% (pq) C R C W 16% (qp) C R C W 4% (q 2 ) C W 64% C R C R, 32% C R C W, and 4% C W C W Gametes of this generation: 64% C R (from C R C R plants) 4% C W (from C W C W plants) 16% C R (from C R C W plants) + + Genotypes in the next generation: 16% C W (from C R C W plants) = = 80% C R = 0.8 = p 20% C W = 0.2 = q 64% C R C R, 32% C R C W, and 4% C W C W plants
Try this: A population of mice displays the recessive trait for loving the banjo. A survey says it is about 20% of them. What % dislike the banjo? What is the frequency of the dominant and recessive allele? What % is heterozygous for this trait?
Review quiz 1.What are the three mechanisms for altering allele frequency? 2.What is the type of selection reflecting the fact that really small wolves and really big wolves don’t survive as well as mediums? 3.Draw the curve. 4.In population of fruit flies, 70% of the gametes contain A1 alleles. If the pop in in H-W equilibrium, what proportion carry both A1 and A2? 0.09