Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Dual inheritance theory wikipedia , lookup
Dominance (genetics) wikipedia , lookup
History of genetic engineering wikipedia , lookup
Koinophilia wikipedia , lookup
Polymorphism (biology) wikipedia , lookup
Hardy–Weinberg principle wikipedia , lookup
Adaptive evolution in the human genome wikipedia , lookup
Genetic drift wikipedia , lookup
Group selection wikipedia , lookup
The Smallest Unit of Evolution • One misconception is that organisms evolve during their lifetimes • Natural selection acts on individuals, but only populations evolve • Consider, for example, a population of medium ground finches on Daphne Major Island © 2011 Pearson Education, Inc. Average beak depth (mm) Figure 23.2 10 9 8 0 1978 1976 (similar to the (after prior 3 years) drought) • Microevolution is a change in allele frequencies in a population over generations • Three mechanisms cause allele frequency change: – Natural selection – Genetic drift – Gene flow • Only natural selection causes adaptive evolution © 2011 Pearson Education, Inc. Natural Selection • Differential success in reproduction results in certain alleles being passed to the next generation in greater proportions • For example, an allele that confers resistance to DDT increased in frequency after DDT was used widely in agriculture © 2011 Pearson Education, Inc. Figure 23.9-1 CRCR CRCR CRCW CWCW CRCR CRCW CRCR CRCR CRCW CRCW Generation 1 p (frequency of CR) = 0.7 q (frequency of CW) = 0.3 Figure 23.9-2 CRCR CRCR CRCW CWCW 5 plants leave offspring CRCR CWCW CRCW CRCR CWCW CRCR CRCW CRCW CRCR CRCR CRCW CRCW Generation 1 p (frequency of CR) = 0.7 q (frequency of CW) = 0.3 CWCW CRCW CRCR CRCW Generation 2 p = 0.5 q = 0.5 Figure 23.9-3 CRCR CRCR CRCW CWCW 5 plants leave offspring CRCR CWCW CRCW CRCR CWCW CRCR CRCW CRCW CRCR CRCR CRCW CRCW Generation 1 p (frequency of CR) = 0.7 q (frequency of CW) = 0.3 CWCW CRCW 2 plants leave offspring CRCR CRCR CRCR CRCR CRCR CRCR CRCR CRCW Generation 2 p = 0.5 q = 0.5 CRCR CRCR CRCR CRCR Generation 3 p = 1.0 q = 0.0 Figure 23.11c Pre-bottleneck (Illinois, 1820) Greater prairie chicken Range of greater prairie chicken Post-bottleneck (Illinois, 1993) A Closer Look at Natural Selection • Natural selection brings about adaptive evolution by acting on an organism’s phenotype © 2011 Pearson Education, Inc. Relative Fitness • The phrases “struggle for existence” and “survival of the fittest” are misleading as they imply direct competition among individuals • Reproductive success is generally more subtle and depends on many factors © 2011 Pearson Education, Inc. • Relative fitness is the contribution an individual makes to the gene pool of the next generation, relative to the contributions of other individuals • Selection favors certain genotypes by acting on the phenotypes of certain organisms © 2011 Pearson Education, Inc. • Natural selection increases the frequencies of alleles that enhance survival and reproduction • Adaptive evolution occurs as the match between an organism and its environment increases • Because the environment can change, adaptive evolution is a continuous process © 2011 Pearson Education, Inc. Why Natural Selection Cannot Fashion Perfect Organisms 1. 2. 3. 4. Selection can act only on existing variations Evolution is limited by historical constraints Adaptations are often compromises Chance, natural selection, and the environment interact © 2011 Pearson Education, Inc. Storytelling! Character + Predicament + Attempted Extrication Edward Bloom (aka current Homo sapiens) • Practice and rehearsal of ideas • Pleasure • Escape from ‘life’ • Nostalgic memories • His son finishes his (life) story Early Homo sapiens • Survival communication • Purpose • Escape from death • Building “mental muscle,” enhancing neural pathways • ‘Fitness’ is transmitting information (including genes) to the next generation Write your own Fiction Using the story equation – the adaptive evolutionary model