Mr. Kecman Microevolution

Microevolution 5 types/ forces Mutation Gene Flow Non-random mating Genetic Drift Selection

Mutation Random change in the nucleotide sequence to create a new characteristic (eg. Hemoglobin)

Gene flow Migration of genes (alleles) between populations. The genes get into the other population and this levels the playing field (eg. Wolf pack)

Non-random mating Assortative mating by choosing a desired trait over a less desired trait (eg. Peacock)

Genetic Drift Changes due to either the environment, or separation. Doesn’t effect large populations as much, but in a small populations it has a drastic impact. Bottleneck effect/ founder effect

Natural Selection Four types: Stable Directional Diversifying Sexual

Video https://www.youtube.com/watch?v=lk4_aIocyHc

Wednesday Agenda: Take a look at Changes in gene pool handout Closer look at Genetic Drift (bottleneck/founder effect) Look at 4 types of Natural Selection Online homework posted Review package at back of room

Closer look at Genetic Drift (small sample size) Two types: Bottleneck effect and founder effect

Bottleneck effect: After a catastrophic event the population of the surviving population’s gene pool may no longer represent the original gene pools variation. By random chance a genes frequency may be drastically altered. If a particular gene’s frequency drops, then the other gene(s) frequency will increase. Thus the surviving population will have new ratios of genotypes and phenotypes. This type of event will diminish the genetic variety in the population and therefore diminish its genetic vigor.

Founder Effect A founder effect occurs when a new colony is started by a few members of the original population. This small population size means that the colony may have: reduced genetic variation from the original population. a non-random sample of the genes in the original population.

Founder Effect

Genetic Drift Vid https://www.youtube.com/watch?v=mjQ_yN5znyk

Four Types of Natural Selection

Stabilizing Selection Culls extreme variants from the population, in this case, eliminating individuals that are unusually light or dark. The trend is toward reduced phenotypic variation and maintenance of the status quo.

very light-colored or very dark-colored oysters might be more frequently preyed upon by shore birds, simply because they are more obvious on the oyster bar; as a result, the intermediate hues become more common.

Directional Selection Shifts the overall makeup of the population by favoring variants of one extreme. In this case, the trend is toward darker color, perhaps because the landscape has been blackened by lava.

If thicker-shelled oysters are more resistant to breakage than thinner-shelled oysters, crabs will be less able to prey upon them, and thicker- shelled oysters will be more likely to survive to reproduce.

Diversifying/disruptive Selection Favors variants of opposite extremes over intermediate individuals. Here, the relative frequency of very light and very dark snails have colonized a patchy habitat where background of white sand is studded with lava rocks.

This might happen in shallow water among rocks This might happen in shallow water among rocks. Light-colored oysters are more cryptic (less easy for a predator to see) because they match the rock color. Dark-colored oysters blend into the shadows cast by the rocks. In this case, intermediate-colored oysters would be most heavily preyed upon by the crabs, and very light and very dark oysters would survive to reproduce.

Sexual Selection Graph

Sexual Selection Draw on back of sheet The evolutionary fitness of an organism not only depends upon its ability to survive but also its ability to reproduce. To reproduce, an individual must obtain a mate and produce viable offspring. Natural selection favors traits that maximize the ability of an individual to compete for and attract mates, and/or the ability to produce offspring.

An example of sexual selection would be male to male competition, mating rituals, complex behaviors, appearance.

Selection Vid https://www.youtube.com/watch?v=W6eZ7zIIOas

Work Time Please pull out “Founder Effect” handout. Also online homework assignment is posted

Thursday Agenda: Go over founder effect handout Learn Hardy-Weinberg and try handout Review booklet work period. Answers posted around walls

Hardy-Weinberg Equation

Natural Selection Vid https://www.youtube.com/watch?v=R6La6_kIr9g&t=356s