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91 terms

Bio 2 Evolution

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Biological Species concept
Proposed by Ernst Mayr
Most widely used and taught concept
Important points
A species is a group of populations whose members have the potential to interbreed in nature and produce viable, fertile offspring; they do not breed successfully with other populations.
Gene flow between populations holds the phenotype of a population together
problems with biological species concept
Tions and Ligers and Grolar Bears!?
1/3 of known mammalian hybrids are fertile
Science (02.11.05) - Trent Holliday
Self-pollinating plants
Breeding criteria is impractical in many cases
Asexual species
Fossils
Morphological Species concept
a classification system based on observable and measurable phenotypic traits
morphology
the branch of biology that deals with the structure of animals and plants
Phylospecies
terminal node in a cladogram (phylogenetic tree)
ecological species concept
views a species in terms of its ecological niche
It applies to sexual and asexual species and emphasizes the role of disruptive selection
Microevolution
leads to subspecific differences
Change in frequency of alleles
Antibiotic Resistance
Sympatric speciation
occurs as individuals from the two evolving species are in contact with one another
Allopatric speciation
occurs as individuals are physically separated somehow
reproductive isolation
separation of species or populations so that they cannot interbreed and produce fertile offspring
Sympatric Speciation
Disruptive selection may lead to sympatric speciation
Hybridization can lead to sympatric speciation
Polyploids
individual organisms that have more than two chromosome sets
High Speciation rates
species from large taxa (rich get richer)
species with low dispersal rates
species with specialized diets
animals influenced by sexual selection
plant species that are animal-pollinated vs. wind-pollinated
speciation
The process by which a new species evolves from a prior species, the most basic process in macroevolution.
Directional selection
form of natural selection in which the entire curve moves; occurs when individuals at one end of a distribution curve have higher fitness than individuals in the middle or at the other end of the curve
Disruptive selection
form of natural selection in which a single curve splits into two; occurs when individuals at the upper and lower ends of a distribution curve have higher fitness than individuals near the middle
stabilizing selection
form of natural selection by which the center of the curve remains in its current position; occurs when individuals near the center of a distribution curve have higher fitness than individuals at either end
Natural Selection
The nonrandom and differential reproduction for different genotypes
Fitness
contribution of a phenotype to the genetic composition of subsequent
Mechanisms of Evolution
Mutations
Gene Flow
Genetic Drift
Nonrandom Mating
Natural Selection
bottle-necking effect
Something knocks out many alleles leaving only a few for the population to repopulate
Founder effect
change in allele frequencies as a result of the migration of a small subgroup of a population
Genetic drift
The gradual changes in gene frequencies in a population due to random events
Gene flow
the transfer of alleles into and out of the population due to the movement of fertile individuals or their gametes
Nonrandom
Nonrandom mating occurs when the probability that two individuals in a population will mate is not the same for all possible pairs of individuals.
E.g. Homozygous recessives choose other homozygous recessive
Often falls into category of natural selection
Descriptive Evidence for Evolution
Fossil Record
Homologous Structures
Developmental Similarities
Vestigial Structures
Biogeography - Galapagos and South America
Molecular Record
Homology
similarity between two structures due to inheritance from a common ancestor
Analogy
resemblance in function and/or appearance that is due to convergent evolution, not common descent
evolution
Biological definition- any genetic or the resulting phenotypic change in organisms from generation to generation
Evolution
A change in allele frequencies in a population over time
A population
the smallest unit that can evolve
Adaptation
the process by which adaptive traits evolve, traits that enhance the survival and reproductive success of their bearers and to the characteristics themselves
natural selection
the non-random and differential reproduction for different genotypes
Uniformitarianism
the mechanisms of change are constant over time, the same geologic processes that operated in the past are still operating today and at the same rate. example: grand canyon has always been there
gradualism
the slow changes over time. example: erosion caused the creation of the grand canyon
types of evidence used to explain the theory of evolution
fossil record, homologous structures, developmental similarities, vesigial structures, biogeography, molecular record
fossil record
the fossil evidence that we have that allows us to trace various species
homologous structures
structures in different species that are similar because of common ancestry
vestigial structures
a feature of an organism that is a historical remnant of a structure that served a function in the organism's ancestors
biogeography
the study of the past and present geographic distribution of a species
molecular record
suggests that a series of evolutionary changes is tied to a progressive accumulation of alterations in the DNA sequences
homology
the similarity between two structures due to inheritance from a common ancestor
anology
resemblance in function and/or appearance that is due to convergent evolution NOT common decent
five assumptions of Hardy-Weinberg Equilibrium
random mating, large population size, no migration between populations, no mutations, natural selection does not affect the alleles under consideration
Hardy-Weinberg meaning
The population would NOT be evolving
required for a population to evolve
mutations that lead to evolutionary growth
mechanisms of evolutionary change
mutations, gene flow, genetic drift, non random mating, natural selection
mutations
a change in the Nucleotide sequence of an organism's DNA
gene flow
the transfer of alleles from one population to another, resulting from the movement of fertile individuals or their gametes
genetic drift
a process in which chance events cause unpredictable fluctuations in allele frequencies from one generation to the next. the effects are most pronounced in small populations
non random mating
occurs when the probability that two individuals in a population will mate is not the same for all possible pairs of individuals
natural selection
a process in which individuals that have certain inherited traits tend to survive and reproduce at higher rates than other individuals because of those traits
bottleneck effect
a random occurrence that causes a struggle in the survival of a population. example: weed killer
fitness
describes the ability to both survive and reproduce, and is equal to the average contribution to the gene pool of the next generation that is made by an average individual of the specified genotype or phenotype
mechanisms of genetic variation
mutations, genetic variation, sexual recombination/diploidy, balancing selection
diploidy
the state of being a diploid cell
evolutionary constraints
selection can only exist on existing variation, historical/developmental processes, trade-offs
convergent evolution
the evolution of similar features in independent evolutionary lineages
writing scientific names
italicized Genus=capitalized, then species
Biological Species Concept
says that a species is a group of populations whose members have the potential to interbreed nn nature and produce viable, fertile offspring, they do not breed successfully with other populations
however: gene flow between populations holds the phenotype of a population together and 1/3 of known mammalian hybrids are fertile
however: gene flow between populations holds the phenotype of a population together and 1/3 of known mammalian hybrids are fertile
phylospecies concept
based on having a common evolutionary history and/or ancestor
Habitat Isolation
populations live in different habitats and do not meet
Behavioral Isolation
little or no sexual attraction between males and females
Temporal Isolation
mating or flowering occurs at different seasons or times of the day
Mechanical isolation
structural differences in genitalia or flowers prevent co-population or pollen transfer
gametic isolation
- male and female gametes fail to attract each other or are inviable
reduced hybrid viability
hybrid zygotes fail to develop or fail to reach sexual maturity
reduced hybrid fertility
hybrids fail to produce functional gametes
reduced hybrid fertility
offspring of hybrids have reduced viability or fertility
microevolution
leads to subspeific differences, changes in frequencies of alleles, antibiotic resistence
macroevolution
speciation
speciation
an evolutionary process in which one species splits into two or more species
allopatric speciation
occurs when species become physically separated (this is the most common)
sympatric speciation
occurs as individuals from the two evolving species are in contact with one another
mechanisms of speciation
natural selection, genetic drift, mutation, hybridization, polyploidy
hybridization
in genetics, the mating, or crossing of two true-breeding varieties
polyploidy
a chromosomal alteration in which the organism possesses more than two complete chromosome sets. it is the result of an accident in cell division
divergence
it is the pattern that evolution most often takes when new species evolve
the tree of life
goal is to find phylogeny of all living things, produced in the 3 domain system
synapomorphy
The possession by two organisms of a characteristic (not necessarily the same in each) that is derived from one characteristic in an organism from which they both evolved
node in phylogenetic tree
a hypothesis of the evolutionary history of a species or groups of related species
homoplasy
a structure formed through convergent evolution, phylogenetic trees does not represent convergent evolution well
monophyletic
one single ancestor
polyphyletic
group has multiple ancestors
paraphyletic
group includes only some of the descendants from an ancestor
parsimony
the simpest answer is likely to be correct
scientific explanations
must be testable and rejectable
natural selection acts
directly on the phenotype and indirectly on the genotype
race
a person's appearance, determined biologically with genetic traits
ancestry
the evolutionary or genetic line of descent of an animal or plant