Natural Selection Mr Blue What is Natural Selection

Natural Selection Mr. Blue

What is Natural Selection? • The process whereby organisms better adapted to their environment tend to survive and produce more offspring. The theory of its action was first fully expounded by Charles Darwin and is now believed to be the main process that brings about evolution.

Fitness • Having a high evolutionary fitness is crucial to providing beneficial genetic traits to the gene pool. Natural Selection is driven by genetic variation. • Fitness (also called Darwinian Fitness) means that an organism is able to find a mate, produce viable offspring and those offspring live to reproduce. The more viable offspring, the better the fitness.

Who founded Natural Selection? • Charles Darwin…and another scientist who doesn’t get as much credit, his name is Alfred Russel Wallace. It turns out they were studying the same concept at the same time. Darwin just published first (this happens a lot in science actually). • Darwin sailed the world on the HMS Beagle. • On the Origin of Species was the book Darwin wrote. • Remember Darwin’s finches!!!

What is a Phenotype? • The set of observable characteristics of an individual resulting from the interaction of its genotype with the environment. • What is a Genotype? • The genetic makeup of an organism. This is coded for by DNA. • An example of a phenotype we learned about in class and the video is the color of the moth/the beak size and shape of the finches.

Genetic Drift • Variation in the relative frequency of different genotypes in a small population, owing to the chance disappearance of particular genes as individuals die or do not reproduce. • An example of genetic drift: The bottleneck effect.

Adaptation(s) • Adaptation is both an evolutionary process and a product of natural selection: adaptation is a process in which traits are modified by natural selection; an adaptation is a phenotypic trait moulded by natural selection. Both cases drive natural selection. • An example of this is the colored moths.

Heritable • Heritability, amount of phenotypic (observable) variation in a population that is attributable to individual genetic differences. Heritability, in a general sense, is the ratio of variation due to differences between genotypes to the total phenotypic variation for a character or trait in a population. • This will be explained more next week when we cover genetics.

Variation • Variation, in biology, any difference between cells, individual organisms, or groups of organisms of any species caused either by genetic differences (genotypic variation) or by the effect of environmental factors on the expression of the genetic potentials (phenotypic variation).

Modes of Selection • A. Directional Selection- In population genetics, directional selection is a mode of natural selection in which an extreme phenotype is favored over other phenotypes, causing the allele frequency to shift over time in the direction of that phenotype. • B. Stabilizing Selection- Is the opposite of Disruptive Selection. This form of selection tends to favor the non-extreme traits and favors more of an intermediate (in-between) trait. • C. Disruptive Selection- This is a form of selection that favors the extreme traits at each end of the spectrum.

Sexual and Artificial Selection • Sexual Selection- Natural selection arising through preference by one sex for certain characteristics in individuals of the other sex. The mates will choose who to breed with due to some form of phenotypic trait. For instance, the peacocks we learned about in the video. • Artificial Selection- Is when humans will select two organisms (or plants) to breed. This is due to their traits being “desired”. We can see this type of selection with livestock or dogs.

References • A great place to find information is Google. I used Google to help put together this slideshow. Do not be afraid to Google something if you do not understand it.