BIOL 1307 Exam 1 Review
Gradual speciation: model that shows how species diverge gradually over time in small steps (large populations)
Punctuated Equilibrium: model for rapid speciation that can occur when an event causes a small portion of a population to be cut off from the rest of the population (tiny populations)
5 fingers or events that led to evolution
genetic drift: effect of chance (small population)
“ring finger” non-random mating
“middle finger” for mutation
movement (gene flow: flow of alleles in & out of a population due to migration of individuals or gametes)
adaptations
Hardy-Weinberg
states that a population’s allele and genotype frequencies are inherently stable— unless some kind of evolutionary force is acting upon the population, neither the allele nor the genotypic frequencies would change. Assumes conditions with no mutations, migration, emigration, or selective pressure for or against genotype, plus an infinite population.
Natural selection: reproduction of individuals with favorable genetic traits that survive environmental change because of those traits, leading to evolutionary change
Ex: tortoises with long necks were more common on dry lands than short necked tortoises. The long necked tortoises were selected because they could reach more leaves & access X2 food than short-neck tortoises. In times of drought, long necked tortoises had an advantage of obtaining food sources due to this trait. Eventually, long necked tortoises were reproductively successful & passed the long neck trait to their offspring. Over time, only long-necked tortoises were present in the population.
Genetic drift: effect of chance on a population’s gene pool Ex: By chance, some individuals will have more offspring than others—not due to an advantage conferred by some genetically-encoded trait, but just because one male happened to be in the right place at the right time (when the receptive female walked by). It is more frequent in small populations
Founder effect: event that initiates an allele frequency change in part of the population, which is not typical of the original population Ex: a mexican travels to SK, marries a south korean, & have children
Convergent evolution: process by which groups of organisms independently evolve to similar forms Ex: For example, flight has evolved in both bats and insects, and they both have structures we refer to as wings, which are adaptations to flight. However, bat and insect wings have evolved from very different original structures. We call this phenomenon convergent evolution, where similar traits evolve independently in species that do not share a common ancestry. The two species came to the same function, flying, but did so separately from each other.
Know allopatric speciation and events that can lead to it
Allopatric speciation: involves geographic separation of populations from a parent species and subsequent evolution
Ex: environmental conditions, such as climate, resources, predators, and competitors for the two populations will differ causing natural selection to favor divergent adaptations in each group. Isolation of populations leading to allopatric speciation can occur in a variety of ways: a river forming a new branch, erosion creating a new valley, a group of organisms traveling to a new location without the ability to return, or seeds floating over the ocean to an island. The nature of the geographic separation necessary to isolate populations depends entirely on the organism's biology and its potential for dispersal.
stabilizing selection: If natural selection favors an average phenotype, selecting against extreme variation, the population will undergo — —. In a mouse population that lives in the woods, for example, natural selection is likely to favor mice that best blend in with the forest floor and are less likely for predators to spot.
Directional selection
When the environment changes, populations will often undergo — — which selects for phenotypes at one end of the spectrum of existing variation. A classic example of this type of selection is the evolution of the peppered moth in eighteenth- and nineteenth-century England.
Diversifying selection:
Selection that favors 2 or more distinct phenotypes. Sometimes two or more distinct phenotypes can each have their advantages for natural selection, while the intermediate phenotypes are, on average, less fit. Scientists call this — —.
What does it mean when a species is reproductively isolated? Reproductive Isolation: Situation that occurs when a species is reproductively independent from other species; behavior, location, or reproductive barriers may cause this to happen. Ex: Given enough time, the genetic and phenotypic divergence between populations will affect characters that influence reproduction: if individuals of the two populations were brought together, mating would be less likely, but if mating occurred, offspring would be nonviable or infertile. Many types of diverging characters may affect the reproductive isolation, the ability to interbreed, of the two populations.
A prezygotic barrier is a mechanism that blocks reproduction from taking place. This includes barriers that prevent fertilization when organisms attempt reproduction.
A postzygotic barrier occurs after zygote formation. This includes organisms that don’t survive the embryonic stage and those that are born sterile.
Over time, the hybrid zone may change depending on the fitness of the hybrids and the reproductive barriers. If the hybrids are less fit than the parents, speciation reinforcement occurs, and the species continue to diverge until they can no longer mate and produce viable offspring. If reproductive barriers weaken, fusion occurs and the two species become one. Barriers remain the same if hybrids are fit and reproductive: stability may occur and hybridization continues.
reinforcement: continued speciation divergence between two related species due to low fitness of hybrids between them/hybrids are less fit than either purebred species. The species continue to diverge until hybridization can no longer occur.
fusion: reproductive barriers weaken until the 2 species become one
stability: fit hybrids continue to be produced
Darwin proposed that natural selection occurs in an environment by __________.
heritable features that make the organism better suited to survive & reproduce
What are the good genes hypothesis? states that males develop these impressive ornaments to show off their efficient metabolism or their ability to fight disease. Females then choose males with the most impressive traits because it signals their genetic superiority, which they will then pass on to their offspring. (peacock example)
macroevolution: broader scale evolutionary changes that scientists see over paleontological time (processes that gave rise to new species and higher taxonomic groups with widely divergent characters) (speciation)
microevolution: changes in a population’s genetic structure (connects population change over time) (small change)
population genetics: study of how selective forces change the allele and genotypic frequencies in a population over time
What is a cline: gradual geographic variation across an ecological gradient Ex: (eggs of alligators)
systematics: field of organizing and classifying organisms based on evolutionary relationships (researchers/scientists use data)
phylogeny: evolutionary history and relationship of an organism or group of organisms (it’s just a hypothesis)
What is used to build phylogenies? Scientists use a tool called a phylogenetic tree (diagram) to show the evolutionary pathways and connections among organisms
Order of taxonomic classification
Domain, Kingdom, Phylum, Class, Order, Family, Genus, species
Know what analogous characters are and examples look different but have a similar function (also, homoplasy) characteristic that is similar between organisms by convergent evolution, not due to the same evolutionary path Ex: wings of dragonfly and wings of bats
Why is parsimony important? is basic to all science & tells us to choose the simplest scientific explanation that fits the evidence. In terms of tree building that means that all other things being equal, the best hypothesis is the one that requires the fewest evolutionary changes. (events occurred in the most simplest yet obvious way)
What is horizontal gene transfer? the transfer of genes between unrelated species
Rooted Phylogeny: there is a single ancestral lineage (typically drawn from the bottom or left) to which all organisms represented in the diagram relate
Unrooted Phylogeny: DO NOT show a common ancestor but do show relationships among species
Biological species: the ability of 2 individuals to successfully reproduce viable, fertile offspring
phylogenetic species concept: how closely related individuals are evolutionary. They possess of certain defining or derived traits.
Gradual speciation: model that shows how species diverge gradually over time in small steps (large populations)
Punctuated Equilibrium: model for rapid speciation that can occur when an event causes a small portion of a population to be cut off from the rest of the population (tiny populations)
5 fingers or events that led to evolution
genetic drift: effect of chance (small population)
“ring finger” non-random mating
“middle finger” for mutation
movement (gene flow: flow of alleles in & out of a population due to migration of individuals or gametes)
adaptations
Hardy-Weinberg
states that a population’s allele and genotype frequencies are inherently stable— unless some kind of evolutionary force is acting upon the population, neither the allele nor the genotypic frequencies would change. Assumes conditions with no mutations, migration, emigration, or selective pressure for or against genotype, plus an infinite population.
Natural selection: reproduction of individuals with favorable genetic traits that survive environmental change because of those traits, leading to evolutionary change
Ex: tortoises with long necks were more common on dry lands than short necked tortoises. The long necked tortoises were selected because they could reach more leaves & access X2 food than short-neck tortoises. In times of drought, long necked tortoises had an advantage of obtaining food sources due to this trait. Eventually, long necked tortoises were reproductively successful & passed the long neck trait to their offspring. Over time, only long-necked tortoises were present in the population.
Genetic drift: effect of chance on a population’s gene pool Ex: By chance, some individuals will have more offspring than others—not due to an advantage conferred by some genetically-encoded trait, but just because one male happened to be in the right place at the right time (when the receptive female walked by). It is more frequent in small populations
Founder effect: event that initiates an allele frequency change in part of the population, which is not typical of the original population Ex: a mexican travels to SK, marries a south korean, & have children
Convergent evolution: process by which groups of organisms independently evolve to similar forms Ex: For example, flight has evolved in both bats and insects, and they both have structures we refer to as wings, which are adaptations to flight. However, bat and insect wings have evolved from very different original structures. We call this phenomenon convergent evolution, where similar traits evolve independently in species that do not share a common ancestry. The two species came to the same function, flying, but did so separately from each other.
Know allopatric speciation and events that can lead to it
Allopatric speciation: involves geographic separation of populations from a parent species and subsequent evolution
Ex: environmental conditions, such as climate, resources, predators, and competitors for the two populations will differ causing natural selection to favor divergent adaptations in each group. Isolation of populations leading to allopatric speciation can occur in a variety of ways: a river forming a new branch, erosion creating a new valley, a group of organisms traveling to a new location without the ability to return, or seeds floating over the ocean to an island. The nature of the geographic separation necessary to isolate populations depends entirely on the organism's biology and its potential for dispersal.
stabilizing selection: If natural selection favors an average phenotype, selecting against extreme variation, the population will undergo — —. In a mouse population that lives in the woods, for example, natural selection is likely to favor mice that best blend in with the forest floor and are less likely for predators to spot.
Directional selection
When the environment changes, populations will often undergo — — which selects for phenotypes at one end of the spectrum of existing variation. A classic example of this type of selection is the evolution of the peppered moth in eighteenth- and nineteenth-century England.
Diversifying selection:
Selection that favors 2 or more distinct phenotypes. Sometimes two or more distinct phenotypes can each have their advantages for natural selection, while the intermediate phenotypes are, on average, less fit. Scientists call this — —.
What does it mean when a species is reproductively isolated? Reproductive Isolation: Situation that occurs when a species is reproductively independent from other species; behavior, location, or reproductive barriers may cause this to happen. Ex: Given enough time, the genetic and phenotypic divergence between populations will affect characters that influence reproduction: if individuals of the two populations were brought together, mating would be less likely, but if mating occurred, offspring would be nonviable or infertile. Many types of diverging characters may affect the reproductive isolation, the ability to interbreed, of the two populations.
A prezygotic barrier is a mechanism that blocks reproduction from taking place. This includes barriers that prevent fertilization when organisms attempt reproduction.
A postzygotic barrier occurs after zygote formation. This includes organisms that don’t survive the embryonic stage and those that are born sterile.
Over time, the hybrid zone may change depending on the fitness of the hybrids and the reproductive barriers. If the hybrids are less fit than the parents, speciation reinforcement occurs, and the species continue to diverge until they can no longer mate and produce viable offspring. If reproductive barriers weaken, fusion occurs and the two species become one. Barriers remain the same if hybrids are fit and reproductive: stability may occur and hybridization continues.
reinforcement: continued speciation divergence between two related species due to low fitness of hybrids between them/hybrids are less fit than either purebred species. The species continue to diverge until hybridization can no longer occur.
fusion: reproductive barriers weaken until the 2 species become one
stability: fit hybrids continue to be produced
Darwin proposed that natural selection occurs in an environment by __________.
heritable features that make the organism better suited to survive & reproduce
What are the good genes hypothesis? states that males develop these impressive ornaments to show off their efficient metabolism or their ability to fight disease. Females then choose males with the most impressive traits because it signals their genetic superiority, which they will then pass on to their offspring. (peacock example)
macroevolution: broader scale evolutionary changes that scientists see over paleontological time (processes that gave rise to new species and higher taxonomic groups with widely divergent characters) (speciation)
microevolution: changes in a population’s genetic structure (connects population change over time) (small change)
population genetics: study of how selective forces change the allele and genotypic frequencies in a population over time
What is a cline: gradual geographic variation across an ecological gradient Ex: (eggs of alligators)
systematics: field of organizing and classifying organisms based on evolutionary relationships (researchers/scientists use data)
phylogeny: evolutionary history and relationship of an organism or group of organisms (it’s just a hypothesis)
What is used to build phylogenies? Scientists use a tool called a phylogenetic tree (diagram) to show the evolutionary pathways and connections among organisms
Order of taxonomic classification
Domain, Kingdom, Phylum, Class, Order, Family, Genus, species
Know what analogous characters are and examples look different but have a similar function (also, homoplasy) characteristic that is similar between organisms by convergent evolution, not due to the same evolutionary path Ex: wings of dragonfly and wings of bats
Why is parsimony important? is basic to all science & tells us to choose the simplest scientific explanation that fits the evidence. In terms of tree building that means that all other things being equal, the best hypothesis is the one that requires the fewest evolutionary changes. (events occurred in the most simplest yet obvious way)
What is horizontal gene transfer? the transfer of genes between unrelated species
Rooted Phylogeny: there is a single ancestral lineage (typically drawn from the bottom or left) to which all organisms represented in the diagram relate
Unrooted Phylogeny: DO NOT show a common ancestor but do show relationships among species
Biological species: the ability of 2 individuals to successfully reproduce viable, fertile offspring
phylogenetic species concept: how closely related individuals are evolutionary. They possess of certain defining or derived traits.
