Midterm 1 Flashcards
Who does evolution work in and when does it not occur?
Works on a population of individuals
If the alleles are the same as the original population then evolution doesn’t occur
Define macroevolution
Change of allelic frequencies from one generation to the next that ultimately leads to reproductive isolation
When does a new species occur?
When two populations are sufficiently different that they can no longer reproduce
What is evolution impossible without genetic variation?
Without genetic variation, allelic frequencies will be constant and therefore no microevolution occurs
What are the two types of genetic variation?
Discrete (polymorphism)
Quantitative
Define heterozygosity
A population measure of genetic diversity at a single locus (2pq)
What is the problem with looking at heterozygosity in a single allele?
Does not accurately represent genetic diversity for all loci in a species
Define species heterozygosity
Estimate of the genetic diversity across all the loci in a genome
What is the average heterozygosity?
Heterozygosity averaged over a random sample of many loci
What is the allelic diversity?
A population measure average number of alleles per locus
Where does genetic variation come from?
Mutations
Chromosomal changes
Sexual reproduction
How do mutations affect genetic variation?
Mutations create new genetic variation creating heritable changes in the DNA if occurring in the gametes
Can be lethal, neutral, deleterious, or advantageous
Describe chromosomal changes
Includes inversions, translocations, deletions, fusions, and duplications
Give an example of fusion
Chromosome 2 in humans is remarkable similar to chromosomes 12 and 13 in chimps and gorillas, suggesting that it arised from the fusion of the two
How does sexual reproduction effect genetic variation?
Meiosis recombination/crossing over
Independent assortment
Fertilization
What is assumed in the hardy-Weinberg equilibrium?
- No mutations
- No immigration
- Large population size
- All genotypes have equal fitness
- Random mating occurs
What occurs when mating is random with no evolutionary forces?
Allele frequencies (p&q) stay the same from one generation to the next
What is the hardy-Weinberg equation?
(p+q)^2 = p^2 + 2pq + q^2
What is the fitness of a genotype?
The ability of a genotype to be passed on during reproduction
What are the mechanisms that cause evolution?
Mutations Gene flow Genetic drift Natural selection Non random mating/inbreeding
What is gene flow?
New things entering a population
Individuals entering a population with new genes
Why is gene flow important?
The idea of managing gene flow is critical to endangered species and fragmented habituated
Fragmented habitats stop gene flow and cause extinction to occur faster
What does genetic drift do?
Reduces the genetic variability
In small populations random selection leads to genetic drift which leads to a loss of genetic diversity and fixation of alleles
Causes the loss of alleles from generation to generation
What is the founder effect?
A small number of individuals leave and begin a new population
There founding populations are small and result in the loss of genetics
What is a population bottleneck?
A large portion of the population is killed off resulting in lower genetic diversity
What is currently happening to genetic frequencies?
Genetic frequencies are drifting to dominance and loss of alleles resulting in homozygousity
Describe natural selection
The favouring of some phenotypes over others
Describe how coral reproduces
Sperm and eggs float to surface and are swept out to the ocean and settle down
What causes natural selection?
Changing environmental pressures
The phenotype that is more relatively fit leave more offspring
Causes a gradual change in population phenotypes from one generation to the next
Give an example of natural selection
The lion fish was accidentally introduced into the carribian by aquariums and devestated the fish population
Those fish with a more cryptic phenotype will have higher reproductive success
Give an example of non random breeding/inbreeding
In 1987 there was 27 condors remaining so serious captive breeding programs were initiated
Today there is 425 condors
However one condor had a mutation that caused chicks to die leading to serious effects on the breeding program
This caused a lose of herterozygosity
How do you measure the inbreeding coefficient?
F = 1- H(observed)/H(expected)
What is the equation of the pedigree path analysis?
F = E(1/2)^n(1 + F)
Is evolution by natural selection random?
No it is not random but a consequence of differential survival and reproductive success of individuals within a population - relative fitness
Describe adaptive evolution
Acts on the phenotype Reduces genetic variation but seldom seen because of diploidy and balancing selection Three types: 1. Directional 2. Stabilizing 3. Disruptive
Define microevolution
Change of allelic frequencies from one generation to the next
What is directional evolution? Give an example
Gradual shift of a phenotype in one direction
The average age of maturity in cod in Newfoundland had shifted as they need to reproduce earlier in order to keep up with the fishing
What is stabilizing evolution? Give an example
Gradual lose of an outside phenotype
Wild beast in Africa all give birth in the same week. This allows a larger number to survive as the predators are full
What is disruptive evolution?
Separates phenotypes
Polar bears and grizzly bears are the same species with different phenotypes
Can produce fertile pizzly bears
Give an example of diploidy
HFE gene chromosome 6
A single point mutation causes the autosomal recessive disorder, haemochromatosis
Accelerates the rate of intestinal iron absorption and progressive iron deposition
Cirrhosis of liver, diabetes, testicular failure, cardiomyopathy
10% of Celtic British and scandanavian are carriers, 1% suffer
Describe balancing selection
Natural selection favouring balanced polymorphism
What is balanced polymorphism?
Two or more phenotypes maintained in stable proportions over many generations
Generally occurs when natural selection favours heterozygotes (sickle cell), different alleles favoured in different environments (snails), frequency dependent selection (fish eating bugs)
Why is no organism perfectly adapted to it’s environment?
- Natural selection can only act on existing variations
- Evolution is limited by historical constraints
- Adaptations are often compromised
- Chance, natural selection, and environment interact
What are the 4 different definitions of a species?
Morphological
Ecological
Biological
Phylogenetic
Define a morphological species and give an example
Are distinct in structure and form from other groups
Practical for fossil record, and popular field guides
Ex. Pillar, maze, and boulder brain coral
Define ecologic species and give an example
Share distinct resources, share the same niche
Relevant towards ecosystem modelling
Play same ecological role
Ex. Lions and tigers
Define biological species and give an example
Actually or potentially interbreed in nature, producing fertile offspring
Ex. W and E meadowlarks are separated by the Mississippi River and have different songs
Define a phylogenetic species
Share the tip of a phylogeny, that is, the smallest set of organisms that share an ancestor and can be distinguished from other such sets
What is reproductive isolation?
An accumulation of genetic differences that ultimately prevent gene pools from two species from mixing
Prezygotic mechanisms
Postzygotic mechanisms
What are the Prezygotic mechanisms of reproductive isolation?
- Habitat/ecological - species live in different ecological niches
- Temporal - species breed at different times
- Behavioural - species differ in their communications
- Mechanical - species differ in their copulatory mechanics
- Gamete - species have different receptor proteins
What are the postzygotic mechanisms?
- Reduced hybrid viability - developing fetus aborted
- Reduced hybrid fertility - do not produce fertile offspring
- Hybrid breakdown - reduced viability
What are some problems with the biological species concept?
Androdioecous populations
Gynogenetic populations
Hybrid populations
Ring populations
What is an androdioecous population?
Almost every individual is a hemaphrodyte and can self fertilize
Advantageous when living in an environment when interactions with your own species is low
Ex. Mangrove killifish
What is a gynogenetic population?
All females
Produce 2N diploid eggs
Require sperm from a different species to stimulate egg development
Ex. Amazon Molly
What is a hybrid population?
Two species interbreed producing fertile offspring
Ex. Red wolf
What is a ring population?
Can interbreed with neighbours but not at extreme ends
Ex. Salamanders in California came down from the north and split and therefore can’t reproduce at the southern end
What is a subspecies?
Population groups within a species
Share unique geographic range/habitat
Distinguishable from other subdivisions in genetically based traits
Do not exhibit marked reproductive isolation
Considered populations partway through evolutionary process of divergence towards full speciation
Ex. Rock wallabies
What is speciation?
Bifurcation of an ancestral species into two species
Allopatric, parapatric and sympatic
What is Allopatric speciation?
A) two populations become geographically separated preventing gene flow between them
B) small population becomes isolated at edge of species geographical range (peripatric)
Both undergo their own mutations, natural selection, and genetic drift
What is an example of Allopatric speciation?
Reed butterfly and lined butterfly fishes
Explain an example of secondary contact
Reed and lined butterfly fish in the Panama Canal
If it had been built as a trench like the French the fish would have created a hybrid zone and be able to travel across to either ocean
What is parapatric speciation?
Population spread over discontinuity of environmental conditions
Natural selection may select different asks on either side
Ex polar bear and grizzly bears
What is sympatic speciation?
New species formed from within range of a population, independent of geographic or environmental gradient
Ex. Hawthorn flies and apple flies
How does sympatic speciation occur?
Habitat differentiation
Polyploidy
Sexual selection
What is polyploidy and what are the types?
2N sets of chromosomes
Autopolyploidy (self) - errors in mitosis/meiosis lead to gametes with same number of chromosomes as somatic cells
Allopoluploidy (closely related species hybridize) - initially sterile but may be able to propogate asexually. Later generations can change into fertile polyploidy. Fertile with each other but cannot breed with either parent
Why is hybridiAtion bad?
Competition between different genotypes within an organism compromises cell cooperation and decreases overall fitness
Highly differentiated unitary animals depend on the full functioning of all their body parts
Any loss of function in a limb or organ will always lead to decreased fitness if not death
When is hybridization a good thing?
A) colonial/modular organisms where intra-individual genetic variability may be beneficial
B) reticulate evolution
Give an example of colonial/modular organisms
Coral chimera - a single organism that contains two or more distinct cell lineages from different genetic origins, in short intracolonial genetic variability
Fusion of closely settling larvae
Increase competitive strength of early developmental stages
Or come into contact through growth providing better adaptive abilities to stresses and diversifies gene pool of consecutive generation
What is reticulate evolution?
Formation of new lineage through partial merging of two ancestor lineages
Not reproductively isolated but may appear morphological my distinct of seperated depending on the packaged genes
Genetic info is repackages into differenent species at different times
What is syngameon?
All members able to share genetic flow according to reticulate evolution
What are the steps to biological research?
- Objective and research hypothesis
- Data collection: experimental design and sampling strategy, relevant to null hypothesis
- Analysis: statistic (test null hypothesis), generate meaningful results
- Interpretation and synthesis: context of current literature, present efforts in a meaningful way
What’s involved in analysis?
Types of data, graphing, statistics
What are the different types of data?
- A) groups (nominal) and counts
B) groups (ordinal) and counts - Groups and measures
- Measures and measures
What are the different types of graphs?
- T-test: Comparing averages
- Correlation, regression: Comparing correlation between variables
- Chi-squared: Associations between groups
- Logistical regression
What is a null hypothesis?
A hypothesis of essentially no difference (no correlation, relationship, or association)
What is the signal and variation for the first 3 graphs?
- T-test: s - difference between the means
V - scatter around these means - Correlation, regression: s - sims of squares regression
V - sum of squares residual - Chi-squared: s - difference between observed and expected
V- expected values
When do you reject the null hypothesis?
When the chance of making a mistake is less than 5%
What did galenus do?
Combined philosophical work of Aristotle with own experience of animal dissection
Explain structure and function of human body
Who discovered galenus was wrong?
Vesalius
Realized he was wrong on many anatomical issues
Introduced comparative anatomy
Realized humans are one species among many, with a few unique traits with many shared in common
What did Lamarck do?
Suggested life was not fixed
Principle of use and disuse: body parts grow in proportion to amount used
Inheritance of acquired characteristics: changes acquired during life passed in to next generation
What did Cuvier do?
Studied elephant fossils near Paris
Declared separate species that had vanished
Challenged idea that all gods creatures are alive
What did Hutton and Lyell do?
Proposed earth was much older than previously believed due to erosion and seabed movement
What did Malthus do?
Realized that populations can increase geometrically, are capable of unlimited growh, but constrained due to lack of food
What did Darwin propose?
Individuals within population naturally vary
Artificial selection
In a limited situation those with better suited traits are more likely to leave offspring
If hereditary, becomes more dominant in next generations (natural selection)
What was good in one situation might not be in another
What are some misconceptions about evolution?
- Theory of the origin of life
- Like climbing a ladder of progress, organisms are always getting better
- Evolution means that life changes randomly
- Natural selection involves organisms trying to adapt
- Natural selection gives organisms what they need
- Evolution is just a theory
What are the different types of lines of evidence?
Direct observation Homology Fossil record Biogeography Pre-adaptations Allometric growth Hererochrony Evo-Devo
What is direct observations? Give an example.
Visible evolutionary changes and effects
Ex. Pesticide resistance
More people than food due to soil erosion, salinization, eutrophication
Challenge is to increase agricultural output, maintain soil coverage, and decrease agricultural loss from pest, disease, poor soil, and frost
Describe the evolution of pesticides
- Toxic heavy metals: 97% effective in early 1900s but only 3% by 1930. Also accumulates in soils, inhibits plant growth, and poisons stuff
- Organochlorines: Paul muller tested org-chemicals for effect on insects and identified chlorinated hydrocarbons. Needed 1kg in 1946 for 60000 bushels, 64kg in 1971
What is the pesticide treadmill?
Pest problem - broad spectrum and persistent organochlorines - does not eradicate all but increases resistance - resurgence and secondary outbreaks - new and large quantities of chemicals used - repeat from 3
What is homologous?
Parallels found in bone structure that are used for different functions
What is the fossil record used for?
Used to support predictions
Ex. Pakicetus described as an early ancestor of modern whales
What is biogeography?
Looking at plate movement and thrusts to determine where fossils might be
Ex. Horses originated in North America around 50 million years ago. No way to move to different continent. Eventually connected and horses could move to South America across panama and to Europe across ice
What is pre-adaption?
A character of an organism that takes on a function when none previously existed it that differs from its existing function which has been derived from evolution
Ex. Feathers for flight
What is allometric growth?
Evolutionary process when differences in rates of growth lead to divergent species groups
Reflect changes in one or a few genes that regulate patterns of growth
Ex. Homologous structures
What is heterochromy?
Evolutionary processes where differences in timing of developmental events leads to divergent species groups
Ex. Pedomophorsis
Define pedimorphosis
Adults retaining juvenile characteristics
Ex. Axolotls
What is Evo-Devo?
Asks how evolutionary changes in genes regulating embryonic development can lead to changes in body shape and form
Ex. Hox genes: different Hox genes regulate development in different areas of the developing embryo along the head to tail axis
Define taxonomy
Identification and naming species placing species in hierarchical classifications that reflect their morphological relatedness to each other
Define phylogenetics
Formal hypotheses identifying evolutionary relationship between species
Give the taxonomic classifications
Domain Kingdom Phylum Class Order Family Genus Species
What is the problem with taxonomic classification?
Mixes apples with oranges
Mixes morphological characteristics with some evolutionary characteristics
No bearing to evolutionary relationship between species
What are phylogenetic classifications based on?
Karyotypes, physiology, sub cellular structures, protein structures, nucleotide sequences, embryo logical histories, homologous characters vs analogous characteristics
What are cladistics?
Process to build a phylogenetic tree based on derived characteristics only
Length of tree branches relative only
What is the difference between a cladogram and a phylogram?
Cladogram doesn’t show timing
Give an example of when a phylogram was used to help a species
Norfolk Island boobook owl in 1986 was down to single female
Had to cross with most closely related sub-species
Constructed mitochondrial based phylogenetic tree because it is a direct measurement of phylogenetic relatedness
Found closest relative was New Zealand boobook
Have a hybrid population today
What are some goals of conservation genetics?
Use genetic and evolutionary theory to reduce risk of extinction in threatened species
Minimize loss of genetic diversity
Minimize deleterious effects of inbreeding depression
What are the 5 questions asked to determine if genetic management is required?
- How large is the effective(breeding) population?
- Has the population experienced a significant bottleneck?
- Has the population lost genetic diversity?
- Is the population suffering from inbreeding depression?
- Is the population genetically fragmented?
Give an example of a fragmented population
Red-cockaded woodpecker
Lives in long leaf pine forests
Builds nests in trees that we are now cutting down
Have to determine whether to manage seperately or together
How do you determine the answers to the five questions?
- Population census and basic ecology
- Historical records
- Direct: gel electrophoresis
Indirect: Ht/Ho = (1- (1/2Ne))^t - Direct: sperm count, basic ecol.
Indirect: Ft=1-(1-(1/2Ne))^t - Nei’s index of genetic distance
What is neis index of genetic similarity and distance?
In=(differenent allele frequencies multiplied)/((total squared allele frequencies pop. 1)(total squared allele frequencies pop.2)^-2)
Distance:
Dn = -ln(In)
How big do populations have to be for the 3 different goals?
Avoid inbreeding depression = 50
Retain single locus genetic diversity = 500-5000
Retain evolutionary potential = 10^5 - 10^6
