Evolution Exam (Final)
Paralogs
Two genes that continue to be expressed after duplication
Pseudogenization
Loss of function after duplication (duplication fate)
Neofunctionalization
After duplication, one gene mutates (increases diversity)
Subfunctionalization
After duplication, both genes partition original functions of parent gene (split, reduces pleiotropy, increases specialization)
Speciation
When new species arise from already existing ones (lineage split)
Species
Group of organisms w/ common evolutionary history
Background extinction
Gradual loss of species due to predation, competition, disease
Mass extinction
Events that lead to large scale loss (asteroid, volcanic eruption)
Give an example of background extinction predation
Inoceramid clam slowly showing more signs of predation before going extinct.
Background extinction - Competition
When a new taxon arrives, it increases in frequency, causing other taxa to decline.
Background extinction disease example
amphibian population declining in 12 months in Eastern Australia
Describe the "Dead Clades Walking" idea
After a mass extinction, species don't usually fully recover (shown in graphs)
Law of Constant Extinction/Van Valens Law
The probability of species going extinct is constant over time.
Geographic Range and Extinction Rates
Species with larger geographical ranges are associated with lower rates of extinction.
Phyletic gradualism vs Punctuated equilibrium
Phyletic gradualism = gradual change
Punctuated equilibrium = rapid divergence (accounted for by natural selection)
What is Cope's Rule
Mammalian species tend to increase in body size over time (active trend). Example: horses
Fossil Trends (3)
No trend: no body size direction
Passive: no directional change, but minimum size precursor beyond which evolution can't take subsequent lineages (once it gets small enough, it can't get smaller)
Active: Each lineage increases in body size
Active trend, how it arises
Active trend: Each lineage increases in size
Appears as a general directional shift in trait values within a clade.
Under species selection: sublclades with smaller sizes = go extinct
Species selection
Result from different rates of extinction or speciation
How body size and speciation are connected
Larger body size = more speciation.
This also results in larger branches (less extinctions!)
Body size and fitness
Positive correlation; larger body = more fitness
Brachiopod vs crayfish
Brachiopod is less compless than the modern crayfish, example of an ACTIVE TREND
3 Elements of Sex
1. Syngamy: fusion of 2 gametes
2. Genetic Recombination: crossing over b/w homologous chromosomes during meiosis
3. Gamete Production: Haploid gametes produced by meiotic division
Explain meiosis briefly
Diploid individuals producing haploid gametes thru 2 rounds of meiosis
Meiosis I: Chromosomes separate and cross over
Meiosis II: Sister chromatids separate and independently assort
Isogamy vs Anisogamy
Isogamy is ONE kind of gamete; fusion of morphologically similar cells, only compatible with right mating types.
Anisogamy is TWO kinds of gametes; large and small gametes (aka oogamy)
Hermaphrodite
Produces egg AND sperm (potential to be mom or dad). Ancestral to male + female species.
Protandrous (Nemo)
First sexual maturity = male, produces sperm. As they get older, they lose the ability to make sperm and instead produce eggs.
Hermaphroditism, Dioecy, Gynodiecy, Androdiecy
In order to evolve from a hermaphrodite to a dioecy, more than one step is required. Most common method is male sterility -> gynodiecy, and then female sterility -> dioecy.
Costs of sexual reproduction (2 main points)
1. Rate of gene transmission to the next gen (fitness)
2. 'Twofold': asexual parents produce more, with more gene transmission.
Cons of asexual organisms
Asexual lineages die out fast, deleterious mutations can be fatal.
Benefits of Sex
Muller's Ratchet: purges deleterious mutations through recombination.
Accelerates adaptive evolution
Development is mainly regulated by ____ ________
Gene expression
Cellular function is determined by ________ __________
Developmental processes
Homeotic Genes
Encode proteins that act like switches and regulate development; HELP DETERMINE PHENOTYPE (size, shape, division, position)
They also create transcription proteins by binding to regulatory enhancer and triggers RNA to begin transcribing gene copies
Mutated homeotic genes (early/late)
Early: Lethal
Later: Species Divergence
Homeotic genes conserved over evolutionary time and _______ on _______, is called ______
ordered on chromosomes, collinearity
Biological Species Concept
Species are identified based on whether they exchange genes; uses gene flow from reproductively isolated locations to draw boundaries
Phenetic Species Concept
Species grouped on phenotypic characteristics; uses clustering of individuals in phenotypic space to draw boundaries
Allopatric Speciation + example
Species isolated due to geographical barrier, prevents gene flow. Example: snapping shrimp (Isthmus of Panama)
Sympatric Speciation with examples
When species have a common ancestor and inhibit the same geographical area
Example: Nicaraguan cichlids (sister species) + Apple Maggot Fly being separated reproductively because of their food source preference (also breeding ground). Apple and hawthorne races.
Prezygotic Isolating Mechanism
1. Mates don't meet (habitat barrier etc)
2. They encounter but don't mate (behavioural)
3. They mate but gametes are incompatible
Postzygotic isolating mechanism
Zygote dies early, or sterile hybrids are produced
Dobzhansky-Muller Incompatibilities
When hybrids have less fitness due to their genotype
Co-evolution interactions
Mutualistic: beneficial
Antagonist: negative
Mosaic: same species have positive in some communities, negative in others
Co-evolution
Most important driver of evolutionary change
Mutualism Exploitation and example
Each species is a consumer of a resource provided by the other species. Becomes exploitative when one species no longer provides a resource (evolution of cheating)
Ex. Soybean legumes and rhizobial bacteria
Cospeciation
When speciation occurs in tandem (speciation in one leads to speciation in another)
Gene-culture evolution
Only for organisms capable of learning, changes in frequency of behaviour = cultural evolution
Artificial Selection
When humans are the selection pressure
Microevolution
Change in allele frequency from one generation to the next
Germ line vs somatic mutations
germ line = in reproductive cells, heritable
somatic = often leads to cancer, not heritable
Nonsense, Synonymous, and Nonsynonymous mutations
Nonsense: Creates a new stop codon
Synonymous: Does not alter the encoded amino acid
Nonsynonymous: Leads to different encoded amino acid
Phenotypic plasticity
One genotype can develop into different phenotypes depending on the environment
Genetic drift
Random fluctuations in allele frequencies
Origins of life
1. Earth forms
2. Earth cools (oceans form)
3. Cell building blocks
4. RNA world
5. Cellular life
6. Diversification
Sexual Selection
non random variation in mating success (not reproductive success)
The handicap principle
Females choose males that signal(higher quality, higher chance of male being chosen)
7 Major Transistions
1. Replication -> compartmentalization
2. RNA -> DNA
3. Prokaryotes -> Eukaryotes
4. Asexual -> Sexual reproduction
5. Unicellular -> Multicellular
6. Individual -> group living
7. Primate -> human societes