Anth 260 Midterm Review

natural selection

• reproduction of the fittest

• certain traits favored over others

• advantageous traits selected for

Is variation important for natural selection?

Yes. If all individuals are the same, then if a drastic change happens, the entire species will go extinct.

adaptive radiation

a species with no predators in a specific environment separating into different environments in the area to avoid competition and eventually changing so much as a result of the separation that they become different species

Darwin’s Three Postulates

• variation in the features/traits related to survival and reproduction

• heritability, features/traits that are inherited through reproduction

• competition, more organisms than can survive because of a limited number of resources and organisms compete for these resources

fitness

measure of relative reproductive success of individuals

• varies with the environment

reproductive success

how many offspring an individual has that survives to reproduce themselves

adaptation

features/traits that increase the fitness of an organism

• produced by natural selection within the context of a particular environment

directional selection

favors individuals exhibiting one extreme of a phenotype range

stabilizing selection

extreme case of balancing selection

balancing selection

production of equilibrium where both extreme forms are selected against

disruptive selection

favors the two extremes and against moderate traits

Birds whose wings are about average length are rare among birds found dead after a severe ice storm. What kind of selection is this?

disruptive selection

Birds whose wings are about average length are most common among birds found dead after a severe ice storm. What kind of selection is this?

stabilizing selection

What kind of mutation is Duchenne Muscular Dystrophy?

Frame Shift Mutation

macroevolution

process by which a new species evolves from an earlier species

microevolution

change in allele frequencies in a population over time

fixation

the probability and the expected time for it to increase to a significant frequency within a population

protein

one or more polypeptide (amino acid) chains folded into a complex 3D structure

protein synthesis

production of proteins using a DNA template

transcription

process of using DNA template to create strand of RNA

• DNA —> mRNA

• within the nucleus

translation

process of making a protein at the ribosome

• outside the nucleus

What base of RNA differs from DNA?

Uracil (instead of Thymine)

three RNA types

mRNA, tRNA, rRNA

mRNA

carries message of DNA base sequence from nucleus to cytoplasm

tRNA

transports amino acids to ribosome

structure of DNA

base, sugar and phosphate

What are the base pairing rules for DNA?

A —> T

G —> C

What are the base pairing rules from DNA to RNA?

A —> U

G —> C

enzyme proteins

responsible for building and breaking down molecules

• critical for growth, digestion

structural proteins

responsible for strengthening cells, tissues, organs

signaling proteins

responsible for cell communication - signals, receptors, relay proteins

regulatory proteins

responsible for binding DNA to turn genes on and off

transport proteins

responsible for moving molecules and nutrients through the body

sensory proteins

responsible for detection of light, sound, touch, smell, taste, pain, heat, other senses

motor proteins

responsible for keeping cells moving and changing shape

• helps to transport components inside cells

defense proteins

responsible for fighting infections, healing, evading predators

storage proteins

responsible for storing nutrients and energy-rich molecules for later use

mutation

inherited or acquired change in DNA

What are the different types of mutations?

wild type, point mutation, silent (synonymous) mutation

wild type mutation

allele that encodes the phenotype most common in a particular natural population

point mutation

change at a single base position

silent (synonymous) mutation

codes for the same amino acid

missense (non-synonymous) mutation and nonsense (non-synonymous) mutation

codes for a different amino acid

frame-shift mutation

left-over introns or deletion of exons resulting in misreading of codons

gene

segment of DNA that produces a recognizable effect on phenotype

regulatory genes (homeobox genes)

highly conserved type of genes that have been maintained in the genome throughout evolutionary history

• regulate the entire process of morphogenesis

hox genes

regulate body segmentation and development of appendages

• subset of homeobox genes

chromosome

DNA sequences bound by proteins in long strands

genotype

combination of alleles

mitosis

somatic cell division

meisos

production of gametes (sex cells)

What happens in meiosis?

parent cells split and form haploid (n) daughter cells with random genetic arrangements

What happens in mitosis?

parent cells split and form diploid (2n) daughter cells that are genetically identical to the parent cell

recombination (crossing over)

reshuffling of genetic material only during meiosis

Why is recombination important?

It increases genetic variation within a sexually reproducing species.

locus (loci)

location of gene

allele

variants of a gene

Blending Inheritance

a perfect mixture of both parent traits

Discrete Inheritance

a mixture of parent alleles, not traits (not perfect)

codominance

both alleles are expressed

dominant allele

overrides other alleles

recessive allele

overridden by dominant allele

phenotypes

physical expression of genes

polygenic inheritance (multi-gene)

two or more genes contributing to a single effect

monogenic inheritance (single-gene)

one gene has a distinct biological effect

pleiotypy

one gene has multiple biological effects on phenotype

What is the problem with genetic determinism?

genetics are inherently probability and not fixed, meaning it can’t be estimated

population

group of randomly mating individuals relatively isolated from other members of the same species

sexual selection

special type of Natural Selection that favors traits that increase success in competition for mates

sexual dimorphism

physical differences between male and female individuals of the same species

non-disjunction error

error in the separation of chromosomes during meiosis

• leads to aneuploidy

aneuploidy

presence of one or more extra chromosomes or absence of one or more chromosomes

monosomy

one copy of a particular chromosome instead of two

trisomy

three copies of a particular chromosome instead of two

sexual dimorphism

the difference in phenotypes between males and females of a species

Population Bottleneck (genetic drift)

a random major event that causes a large percentage of a species’ population to be wiped out, significantly decreasing genetic variation

Founder Effect (genetic drift)

loss of genetic variation when a new colony is established by a very small number of individuals

gene flow

migration with reproduction

• exchange of alleles between populations

• increases genetic variation within populations

• decreases variation within populations

• introduces mutations that occurred elsewhere

frequency

how often something occurs

Hardy-Weinberg Principle

hypothetical model for studying frequency of a particular allele or genotype within a population

What are the five conditions for the Hardy-Weinberg Principle?

• random mating

• no mutations

• infinite population size

• no migration in or out of the population

• natural selection is not acting on the trait being studied

What is one genotype composed of?

two alleles either heterozygous or homozygous

What does the Hardy-Weinberg Principle provide us?

a prediction of what genotype frequencies would look like in an equilibrium state

What happens to the frequencies of alleles and genotypes in a population under the Hardy-Weinberg Principle?

remain constant over time in the absence of other evolutionary influences

How do you find the frequency of a dominant allele?

f(W) = 2 x WW + Ww / 2 x Total

Why is the recessive hemoglobin allele that causes sickle cell maintained at such high levels in African populations?

suggests selective advantages of being heterozygous

• resistance against malaria

The Modern Evolutionary Synthesis

• source of variation and principles of inheritance

• selection of variation based on environmental pressures

What is the purpose of phylogenies?

helps us understand evolutionary history and relationships

clade

grouping that includes a common ancestor and all the descendants (living or extinct) of that ancestor

• monophyletic groups

node

last shared common ancestor for a clade

grade

grouping that includes a group of organisms united by morphological and physiological similarities that are not a clade

monophyletic groups

group that includes a common ancestor and all its descendants (living or extinct)

polyphyletic groups

group with two or more ancestors that don’t include the true common ancestor of its members

• based on convergent characters

paraphyletic groups

group that includes a common ancestor and some, but not all, of its descendants

Principle of Parsimony

a phylogeny with the least number of evolutionary changes is the preferred explanation

homoplasy

similarity in characters due to similar evolutionary pressures or reversal of character states

homology

similarity due to inheritance of a feature from a common ancestor

convergent evolution

adapting to the same or similar environment with the same or similar adaptation but with no biological relation to one another

plesiomorphy

an ancestral (primitive) character/trait

apomorphy

a derived character state

• traits modified from ancestral condition