MSB Final Exam Review

Genotype

The collection of list of genes that an organism has. More specifically, an organism's genotype is the collection or list of all its alleles. 

Sister Chromatids

Parents pass on half their chromosomes to their children through cells called gametes, which are haploid cells (half the # of chromosomes). During meiosis, and during interphase of meiosis, the cell creates an identical copy of every one of the chromosomes, and these identical copies are called sister chromatids. 

While each chromosome is separated from its homologous partner in meiosis I, the sister chromatids are separated in meiosis 2. 

Alleles

There are different version of each gene, which generate the different versions of each trait. Each version is called an "allele" of that gene -- every gene in your genotype is an allele. You also always have two alleles for every one of your genes. 

Homologous Chromosomes

Having the same structure.

Organisms usually have several chromosomes in their cells. (Humans have 46, or 23 pairs). Half comes from one parent, half comes from the other. Each chromosome you get from one parents has a "partner" or "match" among the chromosomes you got from your other parent. Each pair is homologous only with the other, and none of the other chromosomes. 

They "match" if they contain the same genes, but the alleles themselves might be different (i.e. one codes for red hair and the other brown hair). These are matching but not identical.

Phenotype

The way an organism actually looks or the trait that it truly expresses (as compared to its genetic makeup). 

Chromosome

A long strand of DNA. The sections of that strand that "code for" proteins are genes (or, rather, alleles of genes). The sections that don't code for proteins are often called "junk". 

Each chromosome has the genes for multiple traits in your phenotype.

Gene

A gene generates a part of an organism's phenotype. 

For example, every penguin has the gene necessary for generating (the proteins that make up) their feathers. Every penguin also has the gene necessary for generating (the proteins that make up) their beak.

Genes are located at specific spots on chromosomes, and are made of DNA. The genes' primary job is to generate proteins. 

Disruptive Selection

Towards both extremes (graph moves from centralized to having two peaks).

Stabilizing Selection

Removes extreme variants from population, the graph is more centralized and sharper.

Founder Effect

When a few individuals are isolated and start a new population where the gene pool differs from the source population.

Directional Selection

Towards an extreme trait (or selecting against an entire half of a spectrum). Graph's peak moves to right or left.

Hardy-Weinberg Principle

Describes the gene pool of a population that is NOT evolving. It stats that the frequencies of alleles and genotypes in a population will remain constant from generation to generation. 

Equilibrium:

1. No mutations
2. Random mating
3. No natural selection
4. Extremely large population size
5. No gene flow

Gene Pool

A population's genetic makeup. It consists of all copies of every type of allele at every locus in all members of the population. 

Microevolution

Focusing on evolutionary change in populations, on its smallest scale.

Cline

A graded change in a character along a geographic axis. Some clines are produced by a gradation in an environmental variable.

Genetic Drift

When allele frequencies fluctuate unpredictably from one generation to the next (especially in small populations). 

Bottleneck Effect

Cause by a severe drop in population size. By chance alone, certain alleles may be overrepresented, and other might even have disappeared!

Macroevolution

The broad pattern of evolution above the species level.

Speciation

The process by which one species splits into two or more species. (Chapter 24 of Campbell Biology)

Sympatric Speciation

When speciation occurs in populations that live in the same geographic area. This can occur if gene flow is reduced by factors like polyploidy, habitat differentiation, and sexual selection. Aka "same country" speciation.

Polyploidy is when an accident during cell division causes extra sets of chromosomes -- can be common in animals. 

Sources of Genetic Variation

• Formation of New Alleles
• Altering Gene Number or Position
• Rapid Reproduction (mutations quickly generate)
• Sexual Reproduction (crossing over causes changes)

Natural Selection ISN'T PERFECT

1. Selection can only act on existing variations.
2. Evolution is limited by historical constraints. (Previously existing limbs or adaptations prevent new things from happening)
3. Adaptations are often compromises (Seals might walk better if it had legs, but it wouldn't swim as well, so it has flippers, which kind of helps both)
4. Chance, natural selection, and the environment interact.

Allopatric Speciation

Gene flow is interrupted when a population is dividing into geographically isolated subpopulations. Aka "other country" speciation. The gene pools may diverge, different mutations arise, and the allele frequences start to differ. 

Phylogeny

The evolutionary history of a species or a group of species.

Phylogeny Inferences

Phylogenies are inferred from morphological and molecular data. Similar structures, homologies, and analogies are all related. 

Parsimony

We should investigate and accept the simplest explanation that is consistent with the facts.