Exam 1 Flashcards
What is not in Darwin’s theory?
- Evolution creates a new form of life by dramatic mutations
- An organism can evolve during its lifetime
- An organism can influence the evolution of its own structures in response to its environment
- Evolution is a completely random process
What is evolution?
Evolution is the change organisms go throughout earth’s history.
Aristotle’s theory
Fixed ideal species & the ladder of nature
Linnaeus
“father of taxonomy” who made an orderly classification system by grouping similar species into general categories. Also created binomial naming
Theory of Gradualism
Proposed by geologist James Hutton who believed that earth’s geological features are a result from gradual processes
Uniformitarianism
Charles Lyell expanded on Hutton’s idea; the same geological processes in the past as today. Rate of change today = rate of change in past
Erasmus Darwin
(grandfather) first person to formally propose the theory of evolution in his book. He however was not the one to propose natural selection
Lamarck
Linked evolution to adaptations (extinct species could not adapt and therefore went extinct)
Theory of Inheritance of Acquired traits
Proposed by Lamarck; if an organism changes during its life in order to adapt to its environment then those changes are passed onto its offspring (wrong concept, darwin rejected these ideas)
Darwin’s book
Origin of species - 1859
Natural Selection
Survival of the fittest is the reproduction of individuals with favorable genetic traits that survive environmental change bc of those traits. Leading to evolutionary change.
Descent with modification
Darwin proposed that many species on earth are descendants of ancestral past species that were different from today’s species.
Theory of evolution by natural selection
genetic variation is essential for evolution by natural selection. no variation = no adaptations
Fossil records
fossil intermediates seem to be an evolutionary transition between two groups of organisms
Tiktaalik
Represented the transition of organisms from water to land
Archaeopteryx
evolution of bird from reptile
Homology
forms/limbs related by common ancestry and are a result of divergent evolution
Homologous structures
Structures between groups of organisms that have same overall layout and structure. Result of their common ancestor (do not all have the same function)
ex: mammal forelimbs
Vestigial Structures
Fully functional in ancestors but no longer functional to us/present organisms.
ex: wings on flightless birds
Analogous structures
Same function of limb but are not a result of a common ancestor. (no common ancestor but have similar structure with similar function.)
Biogeography
distribution of species which corresponds to geographical history.
Wallace’s line
an imaginary line that explains the variation between organisms in islands a couple miles apart.
Endemic
not found elsewhere
Molecular Biology
- DNA analysis supports evolution
- Closely related organisms have similar DNA
- Evolution of new functions for proteins after mutations. Similar DNA sequences are the strongest evidence for evolution from a common ancestor.
Convergence Evolution
Natural selection acted in the same way under the same conditions. (their similar environmental conditions caused animals to have similar adaptations)
Species
A group of organism that can interbreed and produce viable, fertile offspring (not based on similar appearance)
Speciation
Formation of two species from one original species
Gene Flow
the movement of alleles across a species range. (if gene flow occurs they are same species)
Allele
One of a number of altering forms of a DNA sequence at a particular genetic locus
Biological Species Concept
Members of the same biological species share the same gene pool because there is gene flow between two populations and they are reproductively isolated from other species by natural biological barriers.
Morphological Species Concept
Organisms that have significant morphological and anatomical differences are different species
Temporal Isolation
Species have different breeding schedules
Habitual Isolation
Members of species move or are otherwise separated
Behavior isolation
Certain actions or behaviors (or the lack of them) impacts reproduction
Gametic Isolation
differences in gamete cells prevents fertilization
Mechanical isolation
When mating is impossible between different animal species because of incompatibility
Prezygotic
Before reproduction
Postzygotic
After reproduction
Hybrid inviability
an embryo is produced, but cannot survive development (nonviable)
ex: hybrid salamander
Hybrid Sterility / Reduced Hybrid Fertility
Different species can produce a viable offspring, but that offspring cannot reproduce
ex: mules
Hybrid breakdown
2nd generation hybrids are feeble or sterile
ex: 2nd generation rice plant
Allopatric Speciation
speciation that occurred because of geographical isolation
Sympatric Speciation
Speciation that occurs in the same geographical area. (rarely occurs in animals)
Dispersal
When a few members of a species move to new geographical areas (allopatric speciation)
Vicariance
When a natural situation physically divides organisms (allopatric speciation)
Adaptive Radiation
When organisms diversify rapidly from ancestral species due to multiple speciation events. (many adaptation evolve from a single point of origin, thus causing the species to radiate into several new ones.
(i.e the finches Darwin observed in the Galapagos)
Hybrid Zones
Exist during allopatric speciation; these are areas where two closely related species interact and interbreed.
Reinforcement
Hybrids are less fit than either purebred species. The species continue to diverge until hybridization can not occur. Reproductive barriers are strengthened/reinforced.
Fusion
Reproductive barriers weaken until the two species become one.
Weak reproductive barriers that allow for increased gene flow.
Stability
Fit hybrids continue to be produced. Barriers remain the same so hybridization continues.
Chromosomal errors
Accident during meiosis can result in sympatric speciation. Examples include Aneuploidy where nondisconjunction causes too many or too few chromosomes.
Autoplodity
“self”; the extra set of chromosomes is of the same species.
Alloplodity
Source of the extra pair of chromosomes is a different species. It takes two generations before the offspring will be fertile and viable.
Gradual Speciation
Species diverge gradually through time with small steps (hard to determine the exact point where divergence occured)
Population
A group of individuals of the same species that live in the same area and interbreed producing fertile.
What makes evolution possible?
Genetic variation
“Fixed” Alleles
an allele that is the only variant that exist for a gene in a population.
Genotypic Frequency
% portion of each genotype in the population
Allelic Frequency
% of each allele in the population
Microevolution
an evolving population that is showing genetic changes in alleles over generations.
Population genetic
the study of what changes the allele frequencies in populations.
What three mechanisms cause allele frequency to change?
Natural Selection
Genetic Drift
Gene flow
Hardy-Weinberg
If a large population reproduces sexually at random, then genetic frequencies should not change in the next generation.
Hardy-Weinberg Condition
- mutations
- mating at random
- no natural selection
- super huge population size
- no gene flow in or out
Genetic Drift
change in frequency of a genetic variant in the population due to random chance.
Hardy-Weinberg Equation
p^2 + 2pq + q^2 = 1
Natural selection (microevolution)
- Acts non-randomly on phenotypes of individuals.
- Changes allelic & genotypic frequencies of populations non-randomly
- always leads to adaptation of population to current enviornment
ex: pest resistance to DDT
Genetic Drift (microevolution)
genetic frequency changes due to random events.
-often occurs in small populations
Outcomes of genetic drift
Random changes in allele frequency in either direction. Which reduced genetic diversity as one allele may becomes “fixed” and all other alleles are lost.
Founder Effect
A few founders start a new isolated populations. The founders gene pool differs from original source and their small population size leads to more drift aka alleles are lost.
Bottleneck effect
An event drastically reduces the size of a population.
Gene flow (microevolution)
Alleles move in/out of population. This includes the migration of adults and dispersal of gametes, seeds, larvae.
Result of gene flow
-tends to add genetic diversity to population
-tends to reduce genetic differences between populations.
Relative fittness
Fitness is relative to other individuals in the population
(“fittest” = best reproductive success)
Directional Selection
Populations genetic variance shifts towards a new phenotype when exposed to enviormental changes. (line for population after natural selection is shifted right from the original population line)
Diversifying/Distruptive selection
intermediates are less fit than extremes. This maintains diversity and increases genetic variance.
Stabilizing selection
intermediates types more fit than extremes. Decreases genetic variance. (line with population after natural selection is higher in the middle than original population line)
Frequency dependent selection
The fitness of a phenotype depends on how common it is in the population.
Sexual Selection
success is based on traits related to obtaining mates (note directly related to environment)
intrasexual selection
individuals of one sex compete directly for mates of the opposite sex.
intersexual selection
in intersexual selection, also called mate choice, individuals of one sex (usually the females) are choosy in selecting their mates from the other sex.
Divergent Evolution
The process in which genetic variation occurred in the same/similar species that leads to two distinct species.
Phylogeny
The tree looking diagram that demonstrates the evolutionary history of a species and its relation to other species.
Rooted
Single lineage (at base) represents a common ancestor (tree)
Unrooted
Shows relationship but not a common ancestor. (circle)
Root
The base of the “tree”; indicates the ancestral lineage that gave rise to the organisms in the tree.
Branch Point
Indicates where two lineages diverged
Basal Taxon
Lineage that evolved early and remains unbranched
Sister Taxa
Two lineages stem from the same point
Polytomy
A branch with two or more lineages
Monophyletic group
Consist of ancestral species and its descendants.
Clade
A grouping that includes common ancestor and descendants of that ancestor.
Paraphyletic group
consist of an ancestral species and some (but not all) its descendants
Polyphyletic group
includes distantly related species but does not include their most recent common ancestor.
