Unit 11 evolution of populations

10.5 Evolutionary Biology Today

KEY CONCEPT New technology is furthering our understanding of evolution.

10.5 Evolutionary Biology Today

Fossils provide a record of evolution.

• Paleontology is the study of fossils or extinct organisms.

10.5 Evolutionary Biology Today

• Paleontology provides evidence to support evolution.

10.5 Evolutionary Biology Today

Molecular and genetic evidence support fossil and anatomical evidence.

• Two closely-related organisms will have similar DNA sequences. What would you expect to find the differences code for?

10.5 Evolutionary Biology Today

• Pseudogenes are sequences providing evidence of evolution.– no longer function– carried along with functional DNA– can be clues to a common ancestor

10.5 Evolutionary Biology Today

• Hox genes indicate a very distant common ancestor.– control the development of specific structures– found in many organisms

• Protein comparisons, or molecular fingerprinting reveals similarities among cell types of different organisms.

10.5 Evolutionary Biology Today

• Scientists from many fields contribute to the understanding of evolution.

• The basic principles of evolution are used in many scientific fields. Some for good purposes and some for less ethical – give an example of each.

Evolution unites all fields of biology.

11.1 Genetic Variation Within Population

KEY CONCEPT A population shares a common gene pool.

11.1 Genetic Variation Within Population

Remember me?

• Genotypic• Phenotypic

11.1 Genetic Variation Within Population

Genetic variation in a population increases the chance that some individuals will survive.

• Genetic variation leads to phenotypic variation. Why?• Phenotypic variation is necessary for natural selection.

Why?• Genetic variation is stored in a population’s gene pool.

– made up of all alleles in a population– allele combinations form when organisms have offspring

– How?

11.1 Genetic Variation Within Population

• Allele frequencies measure genetic variation.

– measures how common an allele is in population– can be calculated for each allele in gene pool

11.1 Genetic Variation Within Population

Genetic variation comes from several sources.

• Mutation is a random change in the DNA of a gene.

• Recombination forms new combinations of alleles.

– can form new allele– can be passed on to

offspring if in reproductive cells – why not from body cells?

– usually occurs during meiosis – parents’ alleles

arranged in new ways in gametes

11.1 Genetic Variation Within Population

Genetic variation comes from several sources.

• Hybridization is the crossing of two different species.– occurs when individuals can’t find mate of own

species– topic of current scientific research

11.2 Natural Selection in Populations

KEY CONCEPT Populations, not individuals, evolve.

11.2 Natural Selection in Populations

Natural selection acts on distributions of traits.

• A normal distribution graphs as a bell-shaped curve.

• Traits not undergoing natural selection have a normal distribution.

• Give an example of a trait that could have a normal distribution.

– highest frequency near mean value

– frequencies decrease toward each extreme value

11.2 Natural Selection in Populations

Natural selection can change the distribution of a trait in one of three ways.

• Microevolution is evolution within a population.– observable change in the allele frequencies – can result from natural selection

11.2 Natural Selection in Populations

• Natural selection can take one of three paths.

– Directional selection favors phenotypes at one extreme. What’s happening in this graph?

11.2 Natural Selection in Populations

– Stabilizing selection favors the intermediate phenotype.

– What’s happening in this graph?

• Natural selection can take one of three paths.

11.2 Natural Selection in Populations

• Natural selection can take one of three paths.

– Disruptive selection favors both extreme phenotypes.

– What is happening in this graph?

11.2 Natural Selection in Populations

Where does genetic variation come from? • A. Mutation only • B. Both mutation and recombination • C. Recombination only • D. Mitosis only

11.2 Natural Selection in Populations

Where does genetic variation come from? • A. Mutation only • B. Both mutation and recombination • C. Recombination only • D. Mitosis only • Correct Answer = B

Where is the most common phenotype found in a normal distribution? • A. In the middle range • B. At the low range • C. At the high range • D. Equally across the distribution range

11.2 Natural Selection in Populations

Where does genetic variation come from? • A. Mutation only • B. Both mutation and recombination • C. Recombination only • D. Mitosis only • Correct Answer = B

Where is the most common phenotype found in a normal distribution? • A. In the middle range • B. At the low range • C. At the high range • D. Equally across the distribution range• Correct Answer = A

Review

• Paleontology is the study of fossils – it provides evidence for evolution in a predictable fashion

• Genetics gives evidence of evolution – similar gene sequences are found in related organisms

• Pseudogenes are segments of DNA that no longer function but give clues to evolutionary history

• Evolution unites the study of Biology in a similar way as Einstein’s famous E=mc2 unites Physics.

• Genetic variation increases the chances that some individuals will survive.

• Allele frequencies measure the variation in a species

Review

• Genetic variation comes from several sources– Mutations– Recombination– Hybridization

• Populations evolve – not individuals• Natural Selection can take one of three paths

– Directional – moving towards one extreme– Stabilizing – moving towards the mean value– Disruptive – moving towards both extremes