So how did traits like THIS evolve?

Sexual Selection Acting on reproductive success attractiveness to potential mate fertility of gametes successful rearing of offspring Survival doesn’t matter if you don’t reproduce! Acts in all sexually reproducing species the traits that get you mates influences both morphology & behavior

Sexual selection It’s FEMALE CHOICE, baby!

The lion’s mane… Females are attracted to males with larger, dark manes Correlation with higher testosterone levels Better health more muscle Better fertility longer life But imposes a cost to male HOT! Is it worth it?? Even though it’s very hot to have a large mane the benefit of attracting mates and successfully producing & rearing young since you have that large mane outweighs the costs.  will be selected for because they advance reproductive success Females who chose these males were more “successful” (more, healthier young) and therefore had a greater opportunity to pass on the trait of being attracted to longer darker manes to their daughters and the trait of having longer, darker manes to their sons.

Sexual dimorphism and sexual selection

How does natural selection work? Select FOR Brown Color Select FOR White Color This means that natural selection acts on the phenotype, not the genotype

How does natural selection work? Since it acts on the phenotype, not the genotype.... Lethal alleles may be maintained in a population. Chinese Crested Dog Homozygous Dominant: Hair Heterozygous: Hairless Homozygous Recessive: Dead

Gene Pool: All the genes within a population

Evolutionary fitness is measured by a. reproductive potential b Evolutionary fitness is measured by a. reproductive potential b. physical fitness c. lifespan d. competition e. reproductive success

Evolutionary fitness is measured by a. reproductive potential b. physical fitness c. lifespan d. competition e. reproductive success

Which of the following organisms is most successful in evolutionary terms? a. the one that has the largest territory b. the one that has the greatest food supply c. the one that has the most mates d. the one that has the greatest biomass e. the one that leaves behind the greatest number of offspring

Which of the following organisms is most successful in evolutionary terms? a. the one that has the largest territory b. the one that has the greatest food supply c. the one that leaves behind the greatest number of offspring d. the one that has the greatest biomass e. the one that has the most mates

**NOT adaptation to the environment…it’s random! Force #2: Genetic Drift: Chance events changing frequency of traits in a population **NOT adaptation to the environment…it’s random! ** NOT always the most “fit” traits that prevail!

Two Ways Genetic Drift can Occur: Founder Effect Bottleneck

Founder effect: A few individuals from a population start a new population with a different allele frequency than the original population Small founder group, less genetic diversity than Africans All white people around the world are descended from a small group of ancestors 100,000 years ago (Chinese are white people!)

Founder effect: A few individuals from a population start a new population with a different allele frequency than the original population Small founder group, less genetic diversity than Africans All white people around the world are descended from a small group of ancestors 100,000 years ago (Chinese are white people!)

Bottleneck effect When large population is drastically reduced by a disaster, changing the allele frequency of the population loss of variation by chance event narrows the gene pool Examples: famine natural disaster loss of habitat…

Example: Cheetahs All cheetahs share a small number of alleles less than 1% diversity as if all cheetahs are identical twins 2 bottlenecks 10,000 years ago Ice Age last 100 years poaching & loss of habitat

The bottleneck effect… Eliminates traits whether they are beneficial or not. Increases the overall variability in the population. Amplifies the presence of traits that will eventually lead to extinction Increases the adaptability of a population Decreases the number weak organisms in the population.

The bottleneck effect… Eliminates traits whether they are beneficial or not. Increases the overall variability in the population. Amplifies the presence of traits that will eventually lead to extinction Increases the adaptability of a population Decreases the number weak organisms in the population.

the inheritance of acquired characteristics. mutations. A small group of humans leaves Earth and colonizes a new planet. After many generations, the population on this planet has an unusually high frequency for the incidence of retinitis pigmentosa, relative to Earth's population. This is most likely due to the founder effect. sexual selection. the inheritance of acquired characteristics. mutations. the bottleneck effect. Answer: 1 Source: Barstow - Test Bank for Biology, Seventh Edition, Question #16

the inheritance of acquired characteristics. mutations. A small group of humans leaves Earth and colonizes a new planet. After many generations, the population on this planet has an unusually high frequency for the incidence of retinitis pigmentosa, relative to Earth's population. This is most likely due to the founder effect. sexual selection. the inheritance of acquired characteristics. mutations. the bottleneck effect. Answer: 1 Source: Barstow - Test Bank for Biology, Seventh Edition, Question #16

Which of the following statements accurately describes genetic drift? It occurs when individuals in a population drift out due to emmigration It occurs when individuals drift in to a population due to immigration It refers to random changes in the gene frequencies in a population due to a drop in population size Mutations are the cause of genetic drift Natural selection is the cause of genetic drift.

Which of the following statements accurately describes genetic drift? It occurs when individuals in a population drift out due to emmigration It occurs when individuals drift in to a population due to immigration It refers to random changes in the gene frequencies in a population Mutations are the cause of genetic drift Natural selection is the cause of genetic drift.