Terminology
Evolution: A change in a gene frequency across generations
Theory: hypothesis: a tentative insight into the natural world;
is an analytic structure designed to explain a set of observations, An unproven conjecture; An
expectation of what should happen, barring unforeseen circumstances;
scientific method: a method of investigation involving observation and theory to test scientific
hypotheses
natural selection: Natural selection is the process where heritable traits that make it more likely for an
organism to survive long enough to reproduce become more common over successive generations of a
population. It is a key mechanism of evolution.
mutation: an organism that has characteristics resulting from chromosomal alteration
gene flow: is the transfer of alleles of genes from one population to another.
genetic drift: An overall shift of allele distribution in an isolated population, due to random fluctuations
in the frequencies of individual alleles of the genes
founder effect: changes in allele frequencies that occur when a subpopulation is formed from a larger
one. Typically many rare and usually undesirable alleles are excluded while a few carried by the
founders get a big boost in frequency.
bottleneck: A special case of strong genetic drift where a population experiences a loss of genetic
variation by temporarily going through a marked reduction in effective population size. In demography,
a severe transient reduction in population size.
alleles: One of two or more variants of a gene or other DNA sequences. Different alleles of a gene
generally serve the same function (eg, code for a protein that affects eye color) but may produce
different phenotypes (eg, blue eyes or brown eyes).
genotype: refers to the particular combination of genes or alleles that an individual carries
heterozygous/homozygous: Individuals with two copies of the same allele (homo)
dominant/recessive: Dom always takes precedence only if two recessive genes then appears
codon/anti-codon: letters combined into three-letter words which specifies a particular aminoacid; A
sequence of three nucleotides in transfer RNA that binds to the complementary triplet (codon) in
messenger RNA to specify an amino acid during protein synthesis
redundancy: a term that is typically used to describe situations where a given biochemical function is
redundantly encoded by two or more genes. In these cases, mutations (or defects) in one of these genes
will have a smaller affect on the fitness of the organism than expected from the genes’ function.
recombination: the process by which a strand of genetic material (usually DNA; but can also be RNA) is
broken and then joined to a different DNA molecule
polygenic: Affected by more than one gene.
phenotype: refers to the observable characteristics of the organism
adaptation: Adaptation is the evolutionary process whereby a population becomes better suited to its
habitat. This process takes place over many generations, and is one of the basic phenomena of biology.
species: a dynamic population of individuals
cladogram: a tree diagram used to illustrate phylogenetic relationships
phylogeny: The evolutionary history of an organism
homology: is a type of analogy whereby two human beliefs, practices or artifacts are separated by time
but share similarities due to genetic or historical connections. Specifically in anthropology, a homology
is a structure that is shared through descent from a common ancestor.
analogy: analogous if they perform the same or similar function by a similar mechanism but evolved
separately. Similar structures may have evolved through different pathways, a process known as
convergent evolution, or may be homologous.
convergence: Convergent evolution describes the acquisition of the same biological trait in unrelated
lineages.
symplesiomorphy: persistence of ancestral (primitive) traits in different clades.
synapomorphy: derived (new) character shared by groups. A synapomorphy can be used to infer
common ancestry. diploid/haploid:
p + q = 1: p is dominant gene; q is recessive gene (alleles)
p2+2pq +q2 =1: Hardy Weinberg equilibrium equation (all possible combinations of alleles occurring
randomly) expected genotypes/mating probability
Short-Answers
What contributions did Malthus and Lyell make to evolutionary theory?
Malthus -
Populations increase geometrically (exponential)
Food supply increases arithmetically (linear)
When resources are scarce = confrontation among consumers ensue
Lyell -
Geological process occurs over long periods of time
What is natural selection? How do complex adaptations evolve?
Natural selection is the process where heritable traits that make it more likely for an organism to survive
long enough to reproduce become more common over successive generations of a population. It is a key
mechanism of evolution. Complex adaptations can arise from the accumulation of small random
variations. The evolution of complex adaptations requires all of the intermediate steps to be
favored by selection.
What are the necessary conditions for natural selection?
Acts of individual phenotypes
Traits vary within a population
Differential reproductive success
1. Struggle for existence
2. Variation in fitness
3. The inheritance of variation
Be able to identify the three modes of selection? For each one, what traits (e.g. one extreme, both
extremes or intermediate ones) are favored?
Directional (One extreme)
Bimodal/Disruptive (Both extremes)
Stabilizing (average of the extremes)
Why is mutation unique among evolutionary mechanisms?
Mutation is an organism that has characteristics resulting from chromosomal alteration. And mutation
is unique because the when genes are encoded from DNA to RNA mutation can occur in different
organisms but since the genes of every organism is different mutation will be exclusive to that species
upon evolution of that species.
How/Why does population size influence genetic drift?
An overall shift of allele distribution in an isolated population, due to random fluctuations in the
frequencies of individual alleles of the genes. This is can easily happen to small situations because a
certain type of allele will be favored because of nature whether it be due to the environment,
individuals or resources.
What are the units of evolution and selection? [i.e. who/what evolves, and who/what is selected?]
Natural Selection
Natural Selection may lead to an evolutionary equilibrium at which the most common
place is not the best possible phenotype.
Speciation
Describe 2 differences between mitosis and meiosis.
In Meiosis the special cell division process that produces gametes, only half of the
chromosomes are transmitted from the parent cell to the gamete.
Ordinary cell division called mitosis two copies of the chromosomes present in the nucleus.
Meiosis
Mitosis
1/2 chromosomes
4 haploid daughter cells
Sex Cells
Sexual reproduction
full replica
2 diploid daughter cells
Non-sexcells
asexual reproduction - growth and repair body
What are the components of DNA and RNA?
DNA: Adenine, guanine, cytosine and thymine A-T, C-G pairs
RNA Bases: Adenine, guanine, cytosine and uracil: A-U, C-G pairs
Briefly describe the two steps of protein synthesis: transcription and translation.
Transcription: Transcription is the first step leading to gene expression. The process of creating an
equivalent RNA copy of a sequence of DNA.
Translation: Translation is the production of proteins by decoding mRNA produced in transcription.
Translation occurs in the cytoplasm where the ribosomes are located
Transcription
DNA copied to messenger RNA (mRNA)
mRNA exits nucleus
Translation
mRNA binds with ribosomes
Transfer RNA (tRNA) adds amino acids
What are the differences between Mendelian and polygenic traits?
Mendelian inheritance only account for one gene affecting a trait. For example, there is only one gene
that determines if a pea plant's flower will be white or purple.
On the other hand, polygenic inheritance refers to more than one gene affecting a trait. For example,
there are dozens of individual traits in your DNA that collectively determine your hair color.
Polygenic inheritance explains why there are thousands of natural shades of hair color.
What is convergent (or parallel) evolution?
When both descendants are similar in a particular respect, evolution is defined as parallel if the
ancestors considered were also similar, and convergent if they were not.
Be familiar with explanations for observed patterns of inheritance in MN bloodgroups, albinism and
color-blindness (e.g Mendelian laws); Know how to use a Punnett Square
Mendels's two principles from the pea experiment
1. Genes - The observed characteristics of organisms are determined jointly by two particles,
one inherited from the mother and the one from the father
2. Independent assortment - Each of these two particles or genes is equally likely to be
transmitted when gametes are formed.
Be able to calculate allele and genotypic frequencies, including under Hardy-Weinberg conditions;
know the assumptions of the H-W model
No mutation, No selection, No migration
Inifinitely large population
Random mating
How is variation maintained in populations?
There is no blending of genes
Mutation slowly adds variation
A lot of (genotypic) variation is "protected" from selection
How can behaviors evolve?
Selective retention of benefitted genetic variants
the character must vary
the variation must affect reproductive success
the variation must be heritable
Describe three constraints on adaptation.
Correlated characters
positive/negative
Disequilibrium
"mismatch"
Genetic Drift
In populations, genetic drift may cause random changes in gene frequencies.
The rate of genetic drift depends on population size.
Genetic drift causes differentiation.
Bottleneck effect - drastic reduction in population - surviving individuals - next
generation (not as varied)
What are species? Be familiar with alternate species concepts
Microevolution - How populations change through natural selection
Macroevolution - How new species and higher taxa are formed
Species can usually by distinguished by their behavior and morphology.
The biological species concept defines a species as a group of interbreeding organisms that are
reproductively isolated from other organisms.
Reproductive isolation prevents species from genetically blending together
The ecological species concept emphasizes the role of selection in maintaining species
boundaries.
If geographic or environmental barriers isolate part of a population and selection favors
different phenotypes in these regions then a new species may evolve.
New species may form if there is strong selection that favors two different phenotypes.
What is speciation? Be familiar with three forms of speciation (i.e. allopatric, parapatric & sympatric)
Parapatric speciation - selection is not sufficient to produce a new species, but new species can
be formed if selection is combined with partial genetic isolation.
Sympatric speciation - strong selection favoring different phenotypes can lead to speciation
even when there is no geographic separation and therefore initially there is extensive gene flow
among individuals in the population.
Allopatric speciation occurs when a species is divided into two reproductively isolated
populations that subsequently diverge genetically.
Parapatric speciation occurs when a species experiences different environments in different
parts of its geographic range.
Sympatric speciation occurs when selection strongly favors diferent adaptations within a similar
environment.
How do researchers determine whether a trait is ancestral or derived?
Systematists distinguish ancestral from derived characters by the following criteria:
ancestral characters...
1. appear earlier in organism development
2. appear earlier in the fossil record
3. are seen in outgroups
What is the principle of parsimony and how is it applied in phylogenetic reconstruction(s)?
Parsimony -when competing hypotheses are equal in other respects, the principle recommends
selection of the hypothesis that introduces the fewest assumptions and postulates the fewest entities
while still sufficiently answering the question.
Parsimony is part of a class of character-based tree estimation methods which use a matrix of discrete
phylogenetic characters to infer one or more optimal phylogenetic trees for a set of taxa, commonly a
set of species or reproductively-isolated populations of a single species. These methods operate by
evaluating candidate phylogenetic trees according to an explicit optimality criterion; the tree with the
most favorable score is taken as the best estimate of the phylogenetic relationships of the included taxa.
(Maximum parsimony) is used with most kinds of phylogenetic data; until recently, it was the only
widely-used character-based tree estimation method used for morphological data.
What is the primary difference between cladistic and evolutionary classification/systematics?
Cladistic systematics - argue only descent should matter
Evolutionary systematics - classification should be both based upon descent and an overall
similarity.