Organisms evolve in order to better suit an environment. Evolution involves mutations in the genetic information of organisms that lead to changes in the appearance or phenotype of organisms. Factors from the environment that influence survival, such as availability of food, water and shelter, generate random mutations in organisms. Many mutations are neutral; they have no effect on the organism’s phenotype. Some mutations are detrimental and make the organism less likely to survive. If an organism develops a detrimental mutation, it will not have offspring and so the detrimental mutation will not be passed down. If an organism has a beneficial mutation, its offspring will have that beneficial mutation and will be better able to survive and reproduce. This process of random mutation and selection from the environment insures that organisms advance to more and more complex levels of biological structure.
Fig. 22-19 Hawks and other birds Ostriches Crocodiles Lizards and snakes Amphibians Mammals Lungfishes Tetrapod limbs Amnion Feathers Homologous characteristic Branch point (common ancestor) Tetrapods Amniotes Birds 6 5 4 3 2 1
Two Opposing Theories
Out of Africa theory
Dr. Svante Pääbo, Director of the Department of Evolutionary Genetics, Max Planck Institute.
Two Factors Effecting Haplotypes
Ms. Famili Mr. Edgar
My mtDNA Haplotype
Ms. Famili’s mtDNA Haplotype
Haplogroup U U5 U6
Evolution of Populations
Fig. 23-5 Porcupine herd Porcupine herd range Beaufort Sea NORTHWEST TERRITORIES MAP AREA ALASKA CANADA Fortymile herd range Fortymile herd ALASKA YUKON
Fig. 23-6 Frequencies of alleles Alleles in the population Gametes produced Each egg: Each sperm: 80% chance 80% chance 20% chance 20% chance q = frequency of p = frequency of C R allele = 0.8 C W allele = 0.2
No natural selection
Extremely Large Populations
No gene flow
Fig. 23-9 Original population Bottlenecking event Surviving population
Fig. 23-10a Range of greater prairie chicken Pre-bottleneck (Illinois, 1820) Post-bottleneck (Illinois, 1993) (a)
Fig. 23-10b Number of alleles per locus Minnesota, 1998 (no bottleneck) Nebraska, 1998 (no bottleneck) Kansas, 1998 (no bottleneck) Illinois 1930–1960s 1993 Location Population size Percentage of eggs hatched 1,000–25,000 <50 750,000 75,000– 200,000 4,000 5.2 3.7 93 <50 5.8 5.8 5.3 85 96 99 (b)
Fig. 24-2 (a) Similarity between different species (b) Diversity within a species
SNP For each individual they analysed half a million SNPs, and then amalgamated the results mathematically to produce two numbers representing that person. This allowed each individual's genome to be shown as a point on a two-dimensional plot: the bigger the differences in the genomes, the greater the distance between them on the plot.