Unit 3 (final 12/11) Flashcards
Quantitative Genetics
The study of genetic basis underlying phenotypic variation among individuals
- continuous
- polygenic: one trait controlled by MANY genes
- effected by environmental factors
In a population of clones, how would their heights look?
Human height is controlled by 180 different genes, each with fairly small effects. Genotypes can yield a range of different phenotypes depending on the environment
To measure variation between phenotypes (Vp)
Subtract the smallest (height, weight, etc.) from the largest
Vp = Vg + Ve + C
- Vg: variation because of genes
- Ve: variation due to the environment
- C: unknowns (variation due to random events)
FORMULA PHENOTYPIC VARIATION
What is genetic heritability determined by?
The slope of the line
- no slope = no heritability
When is a trait heritable vs. non-heritable?
- non: when there is no GENETIC affect
- heritable when there’s no environment affect
- SLIGHTLY heritable: an environmental affect
VA = 1, VP = 1
Trait is heritable
- no environmental affect
VA = 0, VP = 1
Non-heritable
- no genetic effect
VA = 1, VP = 2
Slightly heritable
- environmental effect
Mid-offspring
Offspring average
Mid-parent
Parent average
If we KNOW the heritable of a trait, we can predict….?
How natural selection will affect it
R = h^2xs
Breeder’s equation
- R: the response to selection in the offspring generation (how the population will change in the future)
- S: the selection differential in the parent generation
- used to predict the response to a particular strength
How can we identify the genes/alleles that determine certain traits?
- experiment-based
- data-based
Experiment-based
Can only be done with species that can interbreed and have short lifespans
- inbreed, cross species, select specific phenotype you want, inbreed again, genome sequence
Data-based
Can only be done with hundreds of thousands of points (manhattan plot)
- because every change in DNA is technically a different allele, we can do this analysis for each nucleotide position in a genome
Can genetic drift, by itself, change the behavior of animals over time?
Drift, by itself, without natural selection, might fix one allele over the other. So, yes.
- more evident in smaller populations, though
What are the three major categories organisms invest their resources into?
1) growth
2) defense
3) reproduction
What three things determines fitness?
1) Survival to mating age
2) Fecundity
3) mating success
- if there’s lacking in any one area, but the other two are strong, fitness is still good
Higher investment in growth and defense leads to lower what?
Reproduction rates
Physiological senescence
A by-product of life: “rate-of-living” theory
- only true within species, not when comparing species
- faster metabolic rates = faster aging
- if lifespan is set by psychological constraints, we should expect no genetic variance in populations (for lifespans)
Evolutionary senescence: forged by evolutionary processes
In a long enough time line, everyone’s survival rate drops to 0
- mutation accumulation
- The process of the decline in fertility and decline in probability of survival with age.
Antagonistic pleiotropy
Occurs when the fitness consequence of the affected traits run in the opposite direction
- poses a major strain on evolution
Pleiotropy
Alleleic variation influencing more than one phenotype
How does lifespan evolve in nature?
Higher mortality rates leads to bigger litters
- low defense, low growth, high in reproduction
Extrinsic mortality
mortality that is assumed to be a result of environmental hazards and be constant over age.
Intrinsic mortality
mortality that is assumed to be a result of aging and to increase over age,
Microevolution
Consisting of changes in allele frequency in a population over time
Macroevolution
Refers to broad patterns of evolutionary change above the species level
Biological species concept
Groups of organisms that can interbreed to produce viable, fertile offspring
Morphological species concept
NOT really useful
Good for: fossils, asexual, traditional classifications (when nothing else to work with ONLY)
- things that look the same and are hard to distinguish against each other
Cryptic species
Two species that look alike but cannot interbreed
Ecological species
Species that are co-occurring organisms that occupy different niches (or “adaptive zones”)
What are niches?
Adaptations to particular combinations or resource bases
- predators/parsites
- environmental factors in a particular place
Phylogenetic species concept
Smallest possible CLADE
Problems with ecological species concept
- its impossible to define a niche extrinsically of the population occupying it
- niches aren’t like parking spaces; species DO drive each other to extinction, but does that mean they weren’t species to begin with?
Problems with the biological species concept
Prokaryotes, amoeba, some animals, plants, fungi, isolated populations (because they’re too far to breed)
- all of these things may be apart of the same species but they are unable to breed with each other
Geographic modes of speciation
- allopatry
- vicariance
- peripatetic divergence
- parapatry
- sympatry
- species rings
Vicariance
Separation of large populations in two parts (ex. A random mountain forms)
Peripatetic divergence
Allopatry caused by the colonization of a distant habitat from a larger population
In both types of allopatry (vicariance and peripatetic divergence) what is the geneflow)
Geneflow = 0
- because geography results in an ABSOLUTE barrier to any gene flow between diverging populations
Can drift play a role in both variations of allopatry?
Drift may play a role in peripatetic divergence
-
Parapatry
Geographic separation, but not complete isolation
- often occurring in adjoins habitats (ex. Amazonia and Andes butterflies, moving elevations across mountains, depths in the ocean, etc.)
- become different enough to have 0 geneflow even though they can remain in contact
Species rings
When a species has moved around the globe so much that it went in a circle and came back to its original population
- HOWEVER, by the time it returns, there’s no possible geneflow
Sympatry
NO geographic separation among diverging populations
- hypothetical geneflow is pretty high
Reproductive isolation methods (pre-zyotic: before fertilization)
1) Geographic
2) temporal
3) mechanical
4) gametic
Reproductive isolation methods (post-zygotic)
1) hybrid invanility
2) hybrid sterility
3) hybrid depression
Pre-zygotic geographic isolation
the organisms are separated geographically so they never meet to mate
- this is pre-zygotic because the zygote wont be created at all
Pre-zygotic Temporal isolation
Different migration times make species reproductively isolated
- zygote wont ever be created
Mechanical pre-zygotic isolation
a type of prezygotic barrier, where no fertilization occurs and thus reproduction does not occur
- any physical barrier that prevents mating
- physical differences in genitalia prevents mating
Gametic pre-zygotic isolation
gametes (egg and sperm) come into contact, but no fertilization takes place
Post-zygotic hybrid inviability
a situation in which a mating between two individuals creates a hybrid that does not survive past the embryonic stages
- no viable offspring
Post-zygotic sterility
zygote is able to develop into healthy offspring. However, they are unable to produce offspring and, therefore, unable to pass on their genetic material
Post-zygotic hybrid depression
the loss of heterozygosity in a population leading to a decline in fitness
Evolutionary ecology
a field within in both ecology and evolution that examines how interaction between and within species evolve, and the interactions between species and their environment
- considers how the evolutionary effects of competition, mutualists, predators, prey, and pathogens (how species interact with their environment and how those interactions change their evolution)
Intra species
Competition between individuals within the same species
Inter species
Competition between individuals from different species
Evolutionary time
Generations
Ecological time
The right now
- day-to-day
What happens to the diversity and intensity of the species at a MACROevolutionary scale?
It increases
What effect does competition have on fitness?
Decreases it
When you have two positive interactions, what kind of overlap do you want?
Higher
- ex. Pollination. More pollination = more reproduction = higher fitness
When there’s more overlap, what does selection look like?
There’s greater pressure to REDUCE overlap
Where is limiting similarity expected to be strongest?
The tips of phylogenies
- as soon as a species slips, they are more similar than they ever will be again. The pressure to be different is at its highest point
- the older they become, the more different they become, so the pressure lessens
Convergent evolution
the independent evolution of similar features in species of different periods or epochs in time.
- creates analogous structures that have similar form or function but were not present in the last common ancestor of those groups.
What effects does limiting similarity via creation of new niches have?
1) maximizes differences between species
2) decreases competition
What does maximizing differences between species do?
Reduces their negative interactions
As new species emerge, what happens to niche availability?
It becomes smaller
- evolutionary of ecological niches is expected to create specialization as they become narrower
The specialization paradox
The interaction between diversity and competition is expected to reduce niche overlap and increase ecological specialization
- BUT, in diverse ecosystems, generalist species are common
Generalist species
A species able to thrive in a wide variety of environmental conditions and that can make use of a variety of different resources
Adaptive radiation
Something happens in time where a lineage explodes and diversifies like crazy because they have a key innovation (open market; no competition)
- explosion leads to speciation that competes with each other/occupies niches
Key innovations
novel phenotypic trait that allows subsequent radiation and success of a taxonomic group.
What do changes in niches do?
Allows species to jump to NEW niches which are empty of competition
What happens to niches when there’s no competition?
They become empty
Altruism
When a behavior of an organism benefits others at a cost of their own lives
Selfishness
A behavior which is beneficial to the actor and costly to the recipient
Spite
A behavior which is costly to both the actor and the recipient
Cooperation
A behavior which provides a benefit to another individual and which is selected for because of its beneficial effect on the recipient
Intra-sexual selection
Mating sexual selection determined by within-sex interactions
Inter-sexual selection
Mating success determined by between-sex interactions
Polygamy
Any system where individuals mate with multiple individuals in the population
Polygyny
When males mate with multiple females
Polyandry
When females mate with multiple males
When is polyandry favored? What is the consequence?
When males become limiting resources for reproduction
- when females are choosy
- when low offspring survival required male parental care, so that males have the greater reproductive effort and lower reproductive rate
Consequence: sexual selection is stronger
What is additive genetic variation?
Additive effect of individual genes in the phenotype
- three different genes affect height, one of them makes it one inch taller REGARDLESS OF WHAT OTHER ALLELES MAY DO
Epistatic (interaction) genetic variance
How different genes that effect the same trait interact with each other
Co-evolution
Reciprocal evolutionary change between interacting species driven by natural evolution
Can species exist in isolation?
No, they have to interact with each other and the environment to acquire resources
- must compete with each other resources, even if this may be indirectly
If selective pressures are likely to change the allele frequency of a species, what else changes?
The average phenotype of a species
Changes in genetics
Big, RANDOM, mutations in allele frequencies
Evolutionary arms race
One species is evolving their defense mechanisms (ie. plants) and the other one is evolving ways to overcome them (insects)
Escalation
Coadaptations become increasingly powerful/effective
What happens to a co-dependent species when one of them splits (becomes evolutionary independent)
The other splits at the exact same time
Mutualistic relationship
When two organisms of different species work together
- each benefit from the relationship
Parasitism
A non-mutualistic relationship where one species (parasite) benefits and from the other (host)
Symbiotic relationship
When two organisms are in a symbiotic relationship cause one cannot survive without the other
Commensalism
An association where one benefits and the other isn’t harmed, but doesn’t benefit either
