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39 Cards in this Set

  • Front
  • Back
Evolution
Change over time. Both the unity and diversity of life are explained by this process.
Natural Selection
Causes evolution. When there is variation within population of organisms, and what that variation can be inherited, the variants best suited for growth and reproduction in a given environment will contribute disproportionately to the next generation
Environmental Variation
Variation among individuals caused by differences in environment
Genetic Variation
Variation among individuals caused by differences in the genes that are transmitted from parents to their offspring. Genes are composed of DNA and contain coded information that instructs the cell to produce specific types of RNA and protein. Differences among the individuals' RNA and proteins will affect the molecular function of the cell and ultimately can lead to physical differences that we can observe.
This is ultimately caused by mutations. A few mutations rise in each generation as a result of errors in DNA replication and environmental factors. If this mutation is harmful to growth or reproduction, it will die out after a handful of generations. If it is beneficial, it will be incorporated into the genetic make up of every individual in the species.
Arrival of New Species
Evolutionary theory predicts that new species arise by the divergence of populations through time from a common ancestor. As a result, closely related species are likely to resemble each other more closely than they do more distantly related species.
Tree of Life
Full set of evolutionary relationships among all organisms.
Full set of evolutionary relationships among all organisms. Three major branches, representing the three domains and is made up of mostly microorganisms. The last common ancestor of all living organisms, which is the root to the tree, is thought to lie between the branch leading to Archaea and Eukarya.
Descent with Modification
Darwin idea. Evolutionary changes that have accumulated over time since the two lineages split.
Population Genetics
Study of patterns of genetic variation
Phenotype
Observable trait, caused by an individuals genotype (set of alleles they contain) and the environment they live in
Species
Individuals that can exchange genetic material through interbreeding.
Gene pool
all the alleles present in all individuals in a species
Populations
interbreeding groups of organisms of the same species living in the same geographical area.
Somatic Mutations
Occurring in the body's tissues, not passed on
Germ-line Mutations
Occurring in the reproductive cells and therefore passed on to the next generation. For evolution, what we are usually interested in.
Deleterious Mutation
A mutation that is harmful. Usually, random changes to the working parts of complex, organized systems end up being deleterious.
Neutral Mutation
Occur in regions of the genome that are not functionally important. Have neither a advantageous and deleterious affect
Advantageous Mutation
Mutation that is beneficial in terms of survival or reproduction. Can increase in frequency in a population until eventually they are carried by every member of a species. Allows the species to be better adapted to its environment
Allele Frequencies
Rates of occurrence of alleles in populations. It is simply the number of x's present for the allele x. When a population exhibits only one allele at a particular gene, we say that the population is fixed for that allele
Observable Traits
Until the 1960s, this is how traits were observed. You had to study the phenotypes that are only encoded by a single gene, like pea seed colour, height, etc. Provided many difficulties because many genes have more than two alleles, like human blood groups, which have three alleles and therefor six possible genotypes, which result in four different phenotypes.
Gel Electrophoresis
Facilitates the detection of genetic variation. It separates segments of DNA according to their size. If you were homozygous for an allele, it would produce a single band on the gel. Heterozygous would produce two bands.
DNA sequencing
What modern geneticists use today. By looking at the sequence of DNA, you can determine where things differ and then figure out what this causes to happen in the two different organisms.
Evolution at the Genetic Level
A change in the frequency of an allele or a genotype from one generation to the next. Therefore, it is a change in the genetic makeup of a population over time. Populations evolve, NOT individuals.
Hardy-Weinburg Equilibrium
situation in which evolution does not occur. Key conditions must be met.
Required Conditions:
1) There can be no differences in the survival and reproductive success of individuals.
2) Population must no the added to or subtracted from/by migration
3) There can be no mutation
4) The population must be sufficiently large to prevent sampling error.
5) Individuals must mate at random
This is the starting point for population genetic analysis. If we find a population whose allele or genotype frequencies are not in Hardy-Weinburg equilibrium, we can infer that evolution has occurred.
Non-random mating
When individuals do not mate randomly, the mate with the best mate they can find
Adaptations
Brought on by natural selection. Allowed the organisms to survive in their environments better.
Geometric Expansion of Populations
Accelerating increase in population size. Does not occur, populations remain relatively stable from one generation to the next, due to competition for resources.
Fitness
A measure of the extent to which the individuals genotype is represented in the next generation. Natural selection acts over generations to increase the overall fitness of a population.
Discrete traits
Traits that had clear alternative states, such as peas that were either yellow or green.
Continuous traits
Variation in traits across a spectrum, like height in humans.
Modern Synthesis
A synthesis between Darwin's theory of natural selection and Mendelian genetics. It is the current theory of evolution.
Fixation
Natural selection can promote the fixation of beneficial alleles, meaning the allele has a frequency of 1. When this happens, it is known as positive selection.
Negative selection
Natural selection that decreases the frequency of a harmful allele.
Balancing Selection
Form of natural selection. It maintains an allele at some intermediate frequency.
Heterozygote Advantage
When a heterozygote's fitness is higher than that of either of the homozygote's. An example of this is in hemoglobin, which has two alleles. A codes for normal hemoglobin, resulting in normal red blood cells, S for sickle shape of the red blood cells. People that are heterozygous for these two alleles are malaria resistant, and have normal red blood cells, which is better than both homozygous choices
Stabilizing selection
Maintains the status quo and acts against the extremes. An example of this is in fetal birth weight. If a baby is too small, it is unlikely to survive after birth, but if it is too large, it complicates the birthing process. This means that natural selection will work against the extremes, small or large, and choose for the mean, which is a normal sized fetus. Allows a trait to remain the same.
Directional Selection
Leads to a change in a trait over time. An example is provided by drug resistance in malaria parasite. Widespread use of the drug chloroquine has led to changes in the population of the malaria parasite in favour of parasites that are resistant to this drug. From the point of drug resistance, the population has moved in one direction since the 1960s toward increased resistance.
Artificial Selection
A form of directional selection and has been practiced by humans. It is analogous to natural selection, but the competitive element is removed. Successful genotypes are selected by the breeder, not through competition. It is efficient at generating genetic change.
Disruptive Selection
Operates in favour of extremes and against intermediate forms. We see disruptive selection operating on the size of seed-eating birds bills, with small and large bills favoured over intermediation.
Sexual Selection
Promotes traits that increase an individual's access to reproduction opportunities.