Theory of evolution

Many ideas were out there to explain how species change over time but the first published was

Charles Darwin in the H.M.S. Beagle traveled the world for 5 years and made observations of living and fossilized plants and animals. Started to notice relationships among species Most significant stop- the Galapagos

Found many unique species similar but different then those of the mainland. IDEA

CAN SPECIES CHANGE OVER TIME?QuickTime™ and a

TIFF (Uncompressed) decompressorare needed to see this p icture.

Now that an idea was formed DARWIN had to collect evidence

For two decades Darwin worked and experimented and read and borrowed from Thomas Malthus. Malthus idea was that human population grows faster than food supply

Darwin idea was that individuals struggle to compete in changing environmental conditions. Which individuals survive?

Natural selection Mechanism for change in populations.

In Nature organisms produce more offspring than can survive

Due to independent assortment in any population individuals have variations

Individual with useful variations will survive

Over time offspring with certain variations make up most of the population and

may look nothing like their ancestors

In Indonesia Alfred Russell Wallace reached a similar conclusion but Darwin was the first to publish.

Interpreting evidence after Darwin

Much data has been gathered but as Humans have only been here a short time and what happened before us is subject to interpretation.

Evidence for Evolution Adaptation is variation that aids an organism’s chance of survival in its environment. Structural adaptations

Mimicry CamouflagePhysiological adaptations Fossils Anatomy

Homologous structure - Analogous structure

Vestigial structure Embryology- viruses Biochemistry- Modern approach

Mechanisms of Evolution

What was missing from Darwins theory? Genes

Who evolves Populations or individuals?

Natural selection acts on the range of phenotypes

Evolution occurs as a population genes and their frequencies change over time

Gene pool How much (percentage) of any specific allele in the gene pool is called Allelic frequency

Genetic equilibrium

When the frequency of alleles remains the same over generationsDoes it evolve?

Changes in genetic equilibrium

Mutation -most lethal but some……. Are useful

Genetic drift- change of allelic frequencies by chance events…can greatly affect small populations making recessive alleles more common than in the larger population,

Gene Flow- Can be affected by movement into and out of a population

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

                                                                                   

                                                                                                                                                         

Three types of natural selection that act on variation

Stabilizing-favors average individual in a population

Directional selection Occurs when Natural selection

favors on of the extreme variations of the trait

Disruptive selection

Individual with either extreme of a trait’s variation are selected for.

Physical barriers can prevent interbreeding rendering a new species (speciation) can no longer interbreed

Geographic isolation- When a physical barrier divides a population

Reproductive isolation Change in chromosome numbers and speciation

Speciation rates Gradualism-

slow change over time Punctuated equilibrium-

rapid change

Patterns of evolution

Adaptative radiation

Divergent evolution- become more dissimilar over time

Convergent evolutionUnrelated species occupy similar environments which have similar pressures which make them look similar

Review

http://www.ptpleasantbch.k12.nj.us/bridge/genbio/evolutiontaxon.html