Ecological and Evolutionary systems study guide 3
What is the red queen hypothesis?
explains that a species must adapt and evolve not just for reproductive advantage, but also for survival because competing organisms also are evolving.
What would be the frequency of pink flowers in a population where the allele frequency of R is 0.4 and the population is in Hardy-Wein equilibrium.? Assume that R and r are the only two alleles.
frequency of RR: (0.4)^2= 0.16 -frequency of Rr: (0.4)(0.6)2= 0.48 -frequency of rr: (0.6)^2= 0.36
What is diversifying selection
-Favors the survival of two or more different genotypes that produce different phenotypes. -The fitness values of a particular genotype are higher in one environment and lower in a different one, whereas the fitness values of the second genotype vary in an opposite manner. -Diversifying selection is likely to occur in populations that occupy heterogeneous environments, so some members of the species are more likely to survive in each type of environmental condition.
What is the difference between Batesian and Müllerian mimicry? Know examples.
-Batesian: mimicry between unpalatable species (the model) by the palatable one (the mimic). A phenomenon in which non-harmful species have evolved to mimic the appearance of a species that is harmful to potential predators. - the hover-flies of the syrphidae family looking lie bees or wasps. -Mullerian: two or more toxic species converge to look the same, thus reinforcing a basic distasteful design. Mullerian, two both toxic, converge designs batesian, one toxic species on nontoxic, converge so the nontoxic species has better chances of survival.
What is stabilizing selection?
-Favors the survival of individuals with intermediate phenotypes and selects against those with extreme phenotypes. -Stabilizing selection tends to decrease genetic diversity because it eliminates alleles that cause extreme phenotypes
What is directional selection?
-Individuals at one extreme of a phenotypic range have greater reproductive success in a particular environment. -A common reason for directional selection is that a population may be exposed to a prolonged change in its living environment. -Under the new environmental conditions, the relative fitness values may change to favor one genotype, which will promote the elimination of other genotypes.
what is balancing selection
-Natural selection does not always cause the elimination of "weaker" or less fit alleles. Balancing selection is a type of natural selection that maintains genetic diversity in a population. -Over many generations, balancing selection results in a balanced polymorphism, in which two or more alleles are kept in balance and therefore are maintained in a population over many generations. -For genetic variation involving a single gene, balancing selection can favor the heterozygote over either corresponding homozygote. This phenomenon is called the heterozygote advantage. Heterozygote advantage sometimes explains the persistence of alleles that are deleterious in a homozygous condition. -Negative frequency-dependent selection is a second way that natural selection produces balanced polymorphism. In this pattern of natural selection, the fitness of a genotype decreases when its frequency becomes higher. Common individuals have lower fitness and rare individuals have higher fitness, meaning that common individuals are less likely to reproduce, whereas rare individuals are more likely to, thereby producing a balanced polymorphism in which no genotype becomes too rare or too common.
What are the four sources of new genetic variation?
-New mutations within genes that produce new alleles -Random mutations within pre-existing genes introduce new alleles into populations at a very low rate. -Because mutations are rare, the change from one generation to the next is very small. -For new alleles to rise to a specific percentage in a population, evolutionary mechanisms such as natural selection, genetic drift, and migration must operate on them. - Gene duplication - Abnormal crossover events and transposable elements may increase the number of copies of a gene. - Over time the additional copies accumulate random mutations and constitute a gene family. - Horizontal gene transfer - A gene from one species may be introduced into another species. - The transferred gene may be acted on by evolutionary mechanisms.
How does the Hardy Weinberg equation relate to allele and genotype frequencies?
-The Hardy-Weinberg equation describes the relationship between allele and genotype frequencies within a population. -p^2 represents the frequency of the homozygous genotype AA -q^2 represents the frequency of the homozygous genotype aa -2pq represents the frequency of the heterozygous genotype Aa.
What is the difference between assortative mating and disassortative mating?
-assortative mating similar phenotypes mate -disassortive mating dissimilar phenotypes mate
What does it mean for a population to be in H.W. equilibrium? What are the H. W. eq conditions?
A population that is not evolving (the genotypes and genotype frequencies arent changing) No new mutations occur to alter allele frequencies No natural selection occurs: that is no reproductive advantage exists for any of the genotypes Population is so large that allele frequencies do not change due to chance No migration occurs between different populations Random mating occurs
What is an evolutionary arms race?
An evolutionary arms race is a struggle between competing sets of co-evolving genes, traits, or species, that develop adaptations and counter-adaptations against each other
Review Gause's experiments (ch 43.4)
Influence of competition on population growth, studied the competition between protist species, Paramecium aurelia, P. Bursaria, and P. caudatum which feed on bacteria and yeast. Concluded that the two species with exactly the samw requirements can not live together in the same place and use the same resources-- that is occupy the same nice. His conclusion was known as competitive exclusion principle.
Why do populations that went through a bottleneck effect in the past have less genetic variation?
Because a majority of the population died off (the population went through a bottleneck) because of an event or a predator or parasite, so only a small percent of the population is left (usually with the most conducive traits which helped them survive.)
Why does random genetic drift occur faster in small populations?
Because there are less individuals so a change can take less generations causing it to occur faster than it would in a large population. A small population gets to the point of fixation or elimination faster
How can disruptive selection lead to cladogenesis?
It favors more than one genotype that leads to two different phenotypes.
What are the various patterns of natural selection that lead to environmental adaptation?
DIRECTIONAL SELECTION STABILIZING SELECTION DIVERSIFYING SELECTION BALANCING SELECTION
Over the short and long run, does directional selection favor the preservation of genetic diversity? Does stabilizing selection? Does diversifying selection?
Directional selection: favors 1 genotype, so it does not favor preservation of genetic selection Stabilizing selection:tends to decrease genetic diversity because it eliminates alleles that cause extreme phenotypes. Diversifying selection: favors survival of two or more individuals
What's the difference between gene flow and gene pool?
Gene pool: every gene in a given population make up the gene pool Gene Flow: transfer of genetic material from one population to another
If there are 49 red-flowered plants (RR), 42 pink (Rr), and 9 white (rr), what are the genotype frequencies in this population? The allele frequencies?
Genotype frequencies (100 total plants) RED: 0.49 PINK: 0.42 WHITE: 0.09 Allele Frequencies: RED:(0.49)^2= 0.2401 PINK:(0.49)(0.09)(2)= 0.0882 WHITE:(0.09)^2= 0.0081
How does sexual selection explain the evolution of huge peacock tail feathers in the males
Individuals with certain traits are more likely to engage in successful reproduction than other individuals, so peacocks with big pretty tails are more desired by their traits because they seem like more fit mates.
r and k selected species:
K-selected species: These species are characterized by having only a few offspring but investing high amounts of parental care. R- selected species: r-selected species are defined as those present in fluctuating environments that have large numbers of offspring and do not provide long-term care after birth.
Know what Life Tables are for and the important characteristics they track
Life tables follow the fate of a group of individuals all born within the same population in the same year. Of this group, or cohort, only a certain number of individuals will reach each age, and there is an age above which no individuals ever survive.
What is the difference between microevolution and macroevolution?
Microevolution: changes in a single gene or allele frequencies over time - Macroevolution: refers to the formation of new species
Often the fossil itself is not used to determine its age, so what is used instead?
Their location in the sedimentary rock formations Radiometric dating: estimating age by analyzing the decay of radioisotopes within the accompanying rock
What is coevolution?
Occurs when two or more species reciprocally affect each other's evolution through the process of natural selection.
How can sexual selection lead to an increase in the chance of reproducing but a decrease in the chance of surviving?
Sexual selection results in the prevalence of traits, called secondary sex characteristics, that favor reproductive success. The process can result in sexual dimorphism -a significant difference between the morphologies of the two sexes within a species.
How do fossils form?
They are formed during the process of sedimentary rock formation, their hard parts are gradually replaced by minerals over millions of years, producing a recognizable representation of their original organism.
survivability curves
TYPE 1: most individuals die late in life (k-selection) TYPE 2 :uniform death rate TYPE 3:huge decline in young (r-selection)
What is the Darwinian fitness? Does it relate to the size or strength of an organism?
The relative likelihood that one genotype will contribute to the gene pool of the next generation compared with other genotypes.
In what ways might a population change from one generation to the next?
Their inheritable traits/ genes through natural selection - Change in size - Change in geographic location
What is cladogenesis?
a species diverges into two or more species
Know and understand all of the types of species interactions
amensalism, mutualism, commensalism, predation, parasitism, herbivority, and parasitoidism.
Mutualism
an interaction where both species benefit (+/+)
Amensalism
an interaction which is detrimental to one species and neutral to another. (-/0)
commensalism
benefits one species and is neutral to the other (+/0)
What is the difference between the bottleneck effect and the founder effect?
bottleneck effect: change in allele frequencies of the resulting population due to genetic drift. -founder effect: Occurs when a small group of individuals separates from a larger population and establishes a colony in a new location - the difference between the founder and bottleneck effect is that the bottleneck effect usually occurs when the population of a species drops dramatically due to some kind of event and the survivors pass on their conducive genes that helped them survive to the next gen while founder occurs when a small piece of a population leaves its original environment for a new one and establishes a new population in a new environment.
27.) Density dependent and independent factors that affect populations
density-dependent factor: a mortality factor whose influence increases with the density of the population -density-independent factor: a mortality factor whose influence is not changed by changes in population size or density.
Parasitism
in which a parasite establishes a relatively long term relationship with its host, which may or may not lead to the hosts death
Predation
in which a predator feeds on prey and causes rapid death (+/-)
Herbivority
in which an animal feeds on a plant (-/+)
Parasoitoidism
in which an organism lays eggs in a host resulting in larvae remaining in host and usually killing it. (+/-)
What are the effects of genetic drift?
it favors the fixation or elimination of a frequency of an allele. -it alters allele frequencies (two examples of genetic drift are the bottleneck and the founder effect)
Understand how plants and pollinators co-evolve.
it is a mutual relationship where the bee is provided with food (nectar or pollen) and the stationary plant gets to disperse its pollen (sperm cells) to other plants of the same species. ... This is an example of a co-evolutionary relationship. The two species are constantly co-evolving, or in other words, locked in an arms race trying to keep up with eachother. Thus, they remain in the same position relative to each other.
Why sex? How is sexual reproduction related to red queen hypothesis?
sex allows populations to keep giving the next population the most conducive traits. Without this species populations would stay stagnant, which would make them an easier prey for parasites and predators. It allows populations to evolve.