Exam 1: Evolution Flashcards
Extant Species
a species that is still living; surviving
Extinct Species
a species no longer in existence
Archipelago
a group of islands; this is important because Darwin and Wallace both discovered the theory of natural selection studying unique species between islands in an archipelago
Wallace Line
a boundary that separates animals between Asia and Australia, based upon their appearance; this supports the theory of natural selection
Natural Selection
the term coined by Darwin that proves how species change and adapt to their environment to survive
Variation
the differing physical characteristics within on species
Competition
the factor that determines what species has better adaptations
Intertidal Zone
an area in marine aquatic environments that is covered w/ water at high tide, but exposed when water retreats at low tide
Evolution
the change in the genetic composition of a POPULATION across generations; DESCENT WITH MODIFICATION
Differential Survival
when some individuals in a population are more likely to survive than others due to differences in trait values
Genetic Drift
when survival is NOT differential, but heritable variation exists, the population may evolve but the mechanism of evolution is NOT natural selection
Common Garden Experiment
individuals from different populations or species are raised together in a controlled setting
Population
a group of individuals that live in the same place at the same time
Common Ancestors
ancestors that two individuals share
Most Recent Common Ancestors
the ancestor that two individuals share most recently; ex is my sister and I’s most recent common ancestor is our mom
Particulate Inheritance
genes are passed down across generations as separate entities and they can persist across generations even when they are not visibly expressed; ex is two purple flowers making a white flower
Blending Inheritance
the characteristics of the parents are averaged in some way to determine the characteristics of each offspring; ex of this is when two different dog breeds mate to have a mixed breed
What are Mendels two laws?
Law of Segregation and Law of Independent Assortment
Law of Segregation
Mendels 1st law; each individual has 2 gene copies at each locus and these gene copies segregate during gamete production, so that only one copy goes into each gamete
Law of Independent Assortment
Mendels 2nd law; the allele that is passed down to the next generation at one locus is independent of the allele that is passed down to the next generation at another locus; ex of this is seed shape and flower color being two separate alleles
Phenotype
the observable physical, developmental, and behavioral characteristics; ex is blond hair or blue eyes
Genotype
the combination of alleles that an individual has at a given locus; ex is AA, Aa, aa
Allele
different variants of the same gene; A or a
Locus
the physical location of gene copies on the chromosome
Gene
a sequence of DNA that specifies a functional product
Homozygote
containing alleles for ONLY ONE TRAIT for any given character / two copies of same allele; AA or aa
Heterozygote
containing alleles for TWO TRAITS for a given character / two different alleles; Aa
Dominant
a trait that is physically observed both when it is homozygous and heterozygous; AA or Aa
Recessive
a trait that is observed only when it is homozygous; aa
Genotype Frequency
the amount of a specific genotype in a population divided by the total number of individuals in the population
Allele Frequency
the amount of a specific allele in a population divided by the total number of alleles in the population (individuals * 2)
Equilibrium
a state of the population such that genotype frequencies DO NOT change from generation to generation
Hardy-Weinberg Model
a null model for how genotype frequencies relate to allele frequencies in large populations and how they change over time in the absence of evolutionary forces (natural selection, mutation, migration, random mating, genetic drift)
Null Model
a model that provides a baseline for comparison
Fitness
a measure of the relative lifetime reproductive success of a specific genotype/phenotype; how evolutionarily successful an individual is within a certain environment, relative to other individuals
Null Hypothesis
there is NO difference between prediction and observation
Alternative Hypothesis
there will be an expected difference between prediction and observation
What characterizes a statistically significant difference?
a number greater than 0.05
Selection Coefficent
”s”; a measure of the strength of natural selection for or against a specific phenotype or genotype
***the larger the selection coefficient, the stronger the action of natural selection
Fixation
when an allele replaces all other alternative alleles in a population and the frequency of that allele goes to 1; f(allele) = 1
Directional Selection
when selection drives a phenotype in a single direction towards fixation of a single, favored allele
Overdominance/Heterozygote Advantage
a form of frequency independent selection in which heterozygote genotypes have higher fitness than the corresponding homozygote genotypes
Polymorphism
two or more different phenotypes
Underdominance/Homozygote Advantage
a form of frequency independent selection in which the heterozygote genotype has a lower fitness than either homozygote genotype
Frequency Dependent Selection
a form of selection in which the fitness associated with a trait or genotype depends on the frequency of that trait in a population
Survival
the existence of organisms which are best adapted to their environment
Fecundity
a measure of the ability to produce offspring
Polygyny
a mating system in which a male mates with more than one female, but each female mates with only one male during mating season
Monogamy
a mating system in which a male only mates with a single female and vise versa during a mating season
Anisogamy
form of sexual reproduction in which the zygote is formed from the union of two gametes of unequal size and unlike form; by convention, the sex producing the larger gamete is female (egg) and the smaller gamete is male (sperm)
Sexual Selection
form of evolution by natural selection that acts on traits affecting mating success; two types (male-male competition or female choice)
Male-Male Competition
a form of sexual selection in which males compete for access to mates
Female Choice
a form of sexual selection in which females choose their mates
Intrasexual Selection
when one sex directly competes with members of the same sex for mating opportunities; this drives the evolution of secondary sex characteristics that improve fighting ability (Male-Male competition)
Intersexual Selection
when one sex chooses a mate from members of the opposite sex; this drives evolution of secondary sex characteristics that highlight ornaments to make members of the chosen sex more attractive to the choosing sex (Female Choice)
Direct Benefits
parental care, resources, protection
Indirect Benefits
attractiveness leading to more mating
What are the 2 Hypotheses about Indirect Benefits?
Good Genes and Runaway Sexual Selection (or “Sexy Sons”)
Good Genes Hypothesis
showy males offer genes that increase fitness of a females offspring by ensuring heterozygosity or conferring advantages such as disease resistance
Runaway Sexual Selection (“Sexy Sons”) Hypothesis
constant evolutionary feedback loop that produces sons with a desirable/attractive trait, and daughters that desire those traits until that trait reaches a point of no further evolutionary benefit
Actor
an animal performing behavior
Recipient
an animal affected by the actors behavior
Mutual Benefit
actor and recipient both benefit because they both directly increase their fitness; ex is pack hunting
Selfishness
only benefits the actor; ex is lions battling for mates
Altruism
only benefits recipient; ex is blood-bat meal regurgitation
Spite
neither the actor nor recipient gain anything; ex is humans
Group-Selectionist
a debunked theory that thought individuals were willing to engage in altruistic behaviors to benefit the group
When is Reciprocity favored?
- benefit for recipient is greater than cost to actor
- frequent opportunities for repayment
- individuals can recognize each other and remember past behavior
Relatedness
how many alleles, on average, two individuals have in common
Coefficient of Relatedness
“r”; proportion of individual total genotypes identical to others; 0 is unrelated —> 1 is twins
ex is I have 1/2 of my moms alleles, so my “r” with my mom is 0.5
When is Cooperation favored?
- actor and recipient are closely related
- benefits to the recipient are relatively large and/or
- costs of behavior are relatively small
Kin Selection
indirect benefits are greatest when helping a close relative
Haplodiploidy
sisters are more closely related than any other relatives; “r” = 0.75
Eusocial Species
“truly social” species that have 3 attributes…
- strict division of reproductive labor
- cooperative care of young
- overlapping generations
Transition
when a purine (A or G) is replaced by a purine, or a pyrimidine (T or C) is replaced by a pyrimidine
Transversion
when a purine replaces a pyrimidine and vise versa
Synonymous Mutation
when a base change does not change the codon it specifies for
Nonsynonymous Mutation
when a base change alters the codon it specifies for
Nonsense Mutation
when a base substitution creates a stop codon where there was not one previously
Frameshift Mutation
when an insertion or deletion of bases does not happen in a multiple of 3, disrupting the translation of amino acids
Inversion
form of chromosomal rearrangement in which the orientation of a stretch of a chromosome is reversed
Translocation
a form of chromosomal rearrangement in which a section of a chromosome is moved to a non-homologous chromosome
Meiosis
the process of cell division that reduces chromosome number in half and leads to the production of 4 gamete cells
Crossing-Over
a type of recombination during Meiosis where segments of DNA are physically exchanged on homologous chromosomes
Directed Mutations
mutations that are not randomly selected with respect to effects on fitness
Undirected Mutations
mutations that are generated at random with respect to their effects on fitness
Poisson Distribution
when the variance is equal to the mean
Beneficial Mutations
mutations that have a positive effect on an organisms fitness
Deleterious Mutations
*most common; mutations that have a negative effect on an organisms fitness
Neutral Mutations
mutations that have neither a positive nor negative effect on an organisms fitness
Mutation Selection Balance
An equilibrium frequency of deleterious mutations in which these deleterious mutations are maintained at a positive frequency in a population because of a balance between ongoing deleterious mutation and the purging effect of natural selection
Why do people struggle to accept the fact of evolution? (Lecture 2)
Usually it is due to religious beliefs or lack of education on the subject
Why is it critical to tackle acceptance of evolution in our society? (Lecture 2)
It could help prevent disease outbreaks
Young Earth Creationism (Lecture 2)
the original theory that species are young and the earth is not old, that species are completely independent of one another or unrelated, and that they were created in their present form and have not changed over time; this is the religious viewpoint
Lamarck’s Theory (Lecture 2)
evolution occured through the inheritance of acquired characteristics; believed that change is happening through INDIVIDUALS in ONE GENERATION and that they changed in response to the environment and passed those changes to offspring; similar to Darwins theory
Darwins Theory (Lecture 2)
descent with modification by means of natural selection in a POPULATION over MANY GENERATIONS; his example was using pigeon offspring and comparing fanciness of tails over generations; an example from our lifetime is covid
Analogous Traits
organs that have similar functions; ex is bird and butterfly wings
Homologous Traits
structures that share similar embryonic origins relative to their functions, so human hands, bird wings, dog paws, horse hooves all have relatively same structures but different functions
Can something be analogous and homologus?
Yes, bird and bat wings are an example because they share the same structure and function
Vestigial Traits
traits that had a purpose in ancestors but don’t have function anymore; ex is wings on flightless birds
Inherited Traits
traits that are directly passed down from parents to offspring; ex is both of my parents having blue eyes so I will have blue eyes
Heritable Traits
traits that we have a high likelihood of receiving but not guaranteed; ex is height, both of my parents can be tall and I have a high likelihood of being tall as well, but it is not guaranteed
***heritability is a characteristic of a population, not a family pedigree
What are the 3 requirements for Evolution by Natural Selection?
Variation, Heritability, Reproductive Success
If a trait was not heritable, what would happen?
Everybody would have the same trait; ex is if height was not heritable everyone would be the same height
Phylogeny
a model or hypothesis of the branching relationships of populations as one ancestral population gives rise to 2 descendant populations
Clade (monophyletic group)
a collection of branches and nodes that includes an ancestor and all of its descendants
Paraphyletic Group
groups that DO NOT contain all the descendants of the most recent common ancestor
Parsimony
model that requires the fewest number of evolutionary changes in the traits under consideration; this is the most likely explanation of evolution
Mendelian Genetics
describes how alleles are transmitted from INDIVIDUAL PARENTS TO INDIVIDUAL OFFSPRING; ex is sickle cell where AA is normal, AS is normal, and SS is anemic
Population Genetics
the transmission of alleles in a population from one generation to the next
What is “p” is HW Equilibrium?
it is the frequency of the “A” or dominant allele
What does “q” mean in HW Equilibrium?
it is the frequency of the “a” or recessive allele
How to solve the frequency of an allele, “p” or “q”, in a population
number of alleles in the population divided by total alleles in the population
P + Q = ?
1
How to solve the frequency of “AA” or homozygous dominant genotype in the population
p squared; p*p
How to solve the frequency of “Aa” or heterozygous genotype in the population
2pq; 2pq
How to solve the frequency of “aa” or homozygous recessive genotype in the population
q squared; q*q
What assumptions do we make with the HW Model?
- no mutation
- no selection
- no migration
- infinitely large population size
- random mating
Can Mendelian inheritance be considered an evolutionary force?
No because frequencies like ‘p’ and ‘q’ do not change
f(AA) + f(Aa) + f(aa) = ?
1
Which two conditions need to be met for a population to be in HW Equilibrium?
- genotype frequencies are p^2, 2pq, q^2
- genotype frequencies are not changing over time
How to solve for absolute fitness
take the number recaptured and divide that by the original number
How to solve for Relative Fitness
take the largest absolute fitness number and divide it by every other absolute fitness
How to solve for selection coefficient
1 - relative fitness
What does p’ stand for?
the frequency of the allele ‘A’ after one generation of selection
If selection is acting against recessive homozygotes, does p = f(A) always increase over time?
P always increases unless it is equal to 0 or 1 because that means its either not in the gene pool or is the whole gene pool
Is it more beneficial for an allele to have a higher selection coefficient or lower?
Lower; the higher the selection coefficient (s) the less the chance of survival
What happens when selection is acting against a rare dominant allele?
Natural selection drives its frequency down very fast because the phenotype is visible and very easy to eliminate
What happens when selection acts against a rare recessive allele?
Natural selection slowly drives down its frequency because it is able to remain hidden from selection in heterozygotes
Sexual Dimorphism
Sexes have different phenotypes
How do females and males differ in terms of reproduction?
- Females have few eggs that are expensive, whereas males have many sperm that are cheap
- women can be pregnant for months-years
- females engage in more parental care
What is the primary limit on male fitness?
The ability to attract mates
What is the primary limit on female fitness?
the ability to gain resources to produce eggs and rear young
The “Sexy Sons” hypothesis supports what idea?
females want offspring to be attractive like her mates to have a greater chance at attracting their own mates
Do monogamous species tend to be sexually dimorphic?
no, humans are but we are the exception
Why would animals like deer produce sons in resource-rich years and females in resource-poor years?
the data shows this phenomenon because female deer only want to make males if it means they are going to be large; in a resource-poor year she wants to make females because they will survive very easily with low resources, whereas males will be significantly smaller and become poor offspring
Why wouldn’t we expect individuals in large groups of species be altruistic and restrict their reproduction to avoid overpopulation?
We want our alleles to survive past our generation, therefore if we forego that then our alleles would not survive
Why is blood sharing between bat considered altruistic (reciprocal altruism)?
the benefits of the receiver outweigh the cost of the donor
Hamiltons Rule
individuals should be more willing to perform altruistic acts for kin than for non-kin
Hamiltons Rule Equation
Br - C > 0
- B: benefit to the recipient
- r: coefficient of relatedness
- C: cost to donor
5 Pieces of Evidence we have for evolution
- fossil geography / resemblance to fossils
- homology (similarities to anatomical structure among species but difference in function)
- Vestigial structures
- Genetics / change over time
- Geographic distribution
