evolution 4

Creationist opponents of evolution cite the complexity of the eye as a feature that would be impossible to have been produced by evolution. Even Darwin wrote, "That the eye, with all of its inimitable contrivances for adjusting the focus to different distances, for admitting different amounts of light, and for the correction of spherical and chromatic aberration, could have been formed by natural selection seems, I freely confess, absurd in the highest possible degree." Why are creationists wrong and how has this been resolved? Eyes are often lost through drift and natural selection, for example by cave fish and moles. It is still unresolved and is a major weakness of Darwin's evolutionary theory. Creationists call this "irreducible complexity." Numerous examples of intermediate forms have been found, indicating that complex eyes can evolve via gradual change. It is still unresolved and is a major weakness of Darwin's evolutionary theory. Creationists call this "irreducible complexity."

Numerous examples of intermediate forms have been found, indicating that complex eyes can evolve via gradual change.

Which of the following best defines "Hopeful monsters"? Organisms that evolve major genetic changes and hopefully be adapted to new life Organisms that evolve through major genetic and phenotypic changes by saltation and hopefully be adapted to new life Organisms that evolve in sudden bursts of major genetic changes Organisms that evolve through major genetic changes gradually

Organisms that evolve through major genetic and phenotypic changes by saltation and hopefully be adapted to new life

Punctuated Equilibrium refers to Type of natural selection that selects against the average individual in a population. Selection for an extreme phenotype in a population. Periods of rapid speciation that are followed by long periods of little or no change Slow and gradual changes that happen because of continuous processes that place evolutionary pressures on organisms.

Periods of rapid speciation that are followed by long periods of little or no change

Which of the following is NOT an example of macroevolution? The formation of complex traits Patterns in evolution Population genetics Evolution of higher taxa

Population genetics

What is biological homology? How is biological homology different from phylogenetic homology? Is it possible to have phylogenetic homology without biological homology? Why or why not?

Biological homology is when the ancestor had genes that code for a trait that may not necessarily be expressed, but is expressed in a more derived organism or group. Phylogenetic homology includes biological homology but biological homology does not always lead to phylogenetic homology. This is because the phylogeny of organisms can be backed up through genetics and help bring in more insight while biological homology is more of a hidden gene that is not always expressed. An example could be the hox genes. ANSWER: Biological homology homology of genetic sequences and pathways- when two taxa share a similar genetic pathway because of a shared ancestor with the same genetic pathway. This is different from phylogenetic homology which occurs when two taxa share a similar trait because of a shared ancestor with the same trait. These two ideas overlap in that biological homology is necessarily present when you have phylogenetic homology, because traits are a product of genes and genetic pathways. So, you cannot have phylogenetic homology without biological homology. However, you can have traits that appear to be analogous but are biologically homologous

Biological homology refers to Changes in behaviors that signal the first genetic changes that trigger natural selection to act. Characters that are derived from a common ancestor even if they differ in form and function. Similarities in the rate of evolution of different species. Characters that are derived from genetic pathways that are derived from a common ancestor

Characters that are derived from genetic pathways that are derived from a common ancestor

Which of the following is not an example of a reproductive barrier? For a certain species of walrus, males defend large groups of females called harems. Typically, one male's harem will consist of about 20 females, and he will mate with all of them. Some male walruses do not have harems. Two species of cicada live in the same area. Species A is sexually mature every 7 years. Species B is sexually mature every 2 years. Horses and donkeys are different species but can breed with each other to produce mules. However, mules are sterile. as developed an elaborate courtship dance. Species B has vibrant orange plumage and has no courtship dance. Females from species A choose mates based on their dance, and females from species B choose mates based on their plumage.

For a certain species of walrus, males defend large groups of females called harems. Typically, one male's harem will consist of about 20 females, and he will mate with all of them. Some male walruses do not have harems.

Briefly, what is the difference between postzygotic and prezygotic isolation? Be sure to use the terms "zygote" and "hybrid" in your description.

Prezygotic isolations includes all the different reproduction isolations factors what occur before mating and thus prevents mating or forming a zygote that way. This includes geographic isolation, behavioral and sexual isolation, and ecological isolation. Postzygotic isolation includes what happens after mating occurs; this can be separated into two categories: extrinsic and intrinsic. The hybrid is formed at this point but may have many issues in its ability to pass on its traits to other offspring. Answer: Prezygotic isolation is a type of genetic isolating mechanism that occurs before a zygote can be formed. If species experience prezygotic isolation, they are not going to form a hybrid zygote. Postzygotic isolation is a type of genetic isolating mechanism that occurs after the zygote is formed. Species can mate, gametes are fertilized, and a hybrid zygote is formed. Species that experience postzygotic isolating barriers will form hybrids, but hybrids will have reduced fertility, viability, and fitness.

Which of the following examples describe allopatric speciation? Cichlid fishes of Lake Tanganyika show relatively rapid speciation, through sexual and ecological isolation Pygmy nuthatch and brown-headed nuthatch are separated by hundreds of miles in which neither bird occurs Species of marine invertebrates reproduce by releasing their eggs and sperm into the water and allowing the current to move them toward each other. Different species' gamete are incapable of fertilizing each other. A creek connecting two ponds dries up permanently, separating those aquatic populations in those two ponds until they eventually speciate

Pygmy nuthatch and brown-headed nuthatch are separated by hundreds of miles in which neither bird occurs A creek connecting two ponds dries up permanently, separating those aquatic populations in those two ponds until they eventually speciate

What is the relationship between genetic isolation and reproductive isolation? How are they different?

Reproductive isolation is under BSC, and says that if they cannot breed and make fertile offspring then they are different species. Genetic isolation is an umbrella term that contains reproductive isolation, genetic isolation does not require reproductive isolation but reproductive isolation requires genetic isolation in order to occur. Basically, reproductive isolation is a specific circumstance of genetic isolation.

hybrid zone

a geographic area where genetically distinct populations meet and interbreed, but in which there exists partial barriers to gene flow

phylogenetic species

an irreducible group of organisms distinct from other groups that shows a pattern of ancestry and descent

Most models of sympatric speciation postulate the existence of disruptive selection based on resource use. geographical barriers between populations. high levels of recombination between loci. unequal numbers of males and females.

disruptive selection based on resource use.

sibling species

distinct species that are distantly related but almost identical in appearance

Which of the following does NOT tend to promote speciation? Polyploidy Disruptive selection Natural selection Gene flow

gene flow

What is absolutely necessary for speciation to occur

genetic divergence and genetic isolation

The "genetic toolkit" consists of highly conserved genes that encode transcription factors and regulatory genes that underlie development. highly expressed genes. . Taq polymerase, buffer, nucleotides, primers, template DNA, and a thermocycler. enzymes that maintain the structural integrity of the genome.

highly conserved genes that encode transcription factors and regulatory genes that underlie development.

Dobzhansky-Muller Incompatibilities

incompatible interactions between genes inherited from parents of different species

reproductive isolation

occurs when biological differences between populations greatly reduces gene flow/exchange

hybrid speciation

occurs when inbreeding between distinct species results in new species

Microevolution involves _______, whereas macroevolution involves _______. evolution above the species level (i.e., higher taxa); processes that occur within species e. organisms; ecosystems processes that occur within species; evolution above the species level (i.e., higher taxa) organisms; ecosystems genetic changes; phenotypic changes

processes that occur within species; evolution above the species level (i.e., higher taxa)

postzygotic barriers

reduce gene flow between populations after a hybrid zygote is produced

allopatric speciation

reproductive isolation resulting from geographic isolation

Which of the following is NOT a potential outcome of a hybrid zone? a hybrid species forms, creating three distinct species species overlap in space but do not interbreed (prezygotic isolation) the two species fuse into a single species there is reinforcement of postzygotic barriers

species overlap in space but do not interbreed (prezygotic isolation

Which scenario represents a case of a saltation resulting in a "hopeful monster"? A systemic mutation disrupts the genetic system of an organism so much that it results in a "monstrous" mutation. The individuals "hope" to encounter an environment where the change is beneficial. A "monstrous" population evolves following a driven trend; they "hope" to arrive at a new, high-fitness phenotype before their population goes extinct. After a long period of evolutionary stasis, a species undergoes relatively rapid morphological evolution. These "monsters" had "hoped" for a new adaptation to overcome a novel environmental challenge. A small population that has been isolated from a widely distributed species has new mutations fixed rapidly by genetic drift. These "monsters" "hope" that they are not absorbed by the larger population.

A systemic mutation disrupts the genetic system of an organism so much that it results in a "monstrous" mutation. The individuals "hope" to encounter an environment where the change is beneficial.

Describe allopatric, parapatric, and sympatric speciation?

Allopatric is due to a geographic barrier, sympatric is due to a difference in sexual behaviors, temporal, and ecological isolation that leads to genetic isolation through disruptive selection or chromosomal anomalies. Parapatric is when there is speciation on opposite edges of a zone with a hybrid zone in the middle.

What is the difference between allopatric and sympatric speciation? Why does allopatry make determining species using BSC difficult? Why is it easier to use BSC when identifying species that exist in sympatry.

Allopatric is geographic isolation that can occur through vicariance or dispersal (founder effect) factors that lead to ecological speciation. Sympatric is disruptive selection due to differences in temporal and behavior to have speciation through sexual selection. BSC can easily explain and provide evidence for the reproductive isolations within the sympatric speciation (like prezygotic, postzygotic, ect...) but has more difficulty with allopatric because you cannot test gene flow on fossils. Answer: Allopatric speciation occurs when a geographic barrier separates a population, leading to genetic isolation and divergence. Sympatric speciation occurs without a geographic barrier; genetic isolation arises from other reproductive isolating barriers and the population diverges in the same geographic area. Allopatric species present difficulties for BSC because genetic isolation and divergence occurred without a physical barrier. Whether or not these species evolved reproductive isolating barriers is difficult to determine. Allopatric species have the physical barrier to stop gene flow and have never "needed" RIBs to keep them from interbreeding. On the other hand, sympatric species must evolve reproductive isolating barriers in order to diverge, making it easier to determine which RIB are defining species.

Why are fossil intermediates so important for understanding evolutionary history? Without fossil intermediates, what kind of conclusions can be drawn? How are living intermediates different from fossil intermediates? Why are living intermediates (not fossil) important for understanding complexity?

Fossil intermediates are important in understanding evolution over long periods of time. Fossil evidence that is left behind allows us to see how some clades evolved. Without fossil intermediates, some can conclude that the evolution may have been faster with saltations rather than gradual, like in the Cambrian explosion. Not everything is able to be fossilized and this can give rise to evolutionary explanations through living intermediates. They do not have fossil evidence but are helpful in understanding complex forms such as the eye. Eyes do not fossilize and therefore they do not have an evolutionary history that is known. It was believed that due to the complexity of the eye that the evolution happened quickly and all parts were necessary, like a clock. But in reality, there are different forms of the eye; a clam may only be able to sense light and darkness (seeing shadows) while our eyes have a much more complex function. ANSWER: Fossil intermediates are important because they can indicate the phenotypic evolution that has occurred in a lineage. Without fossil intermediates, dramatic changes in morphological evolution appear to have occurred through saltation. Living intermediates are intermediate structures that exist in extant taxa. These living intermediates help to illustrate how complex structures, like the eye, can evolve via less complex -but still functional and adaptive - intermediates.

What are the two steps of speciation?

Genetic isolation and genetic divergence

Speciation is described as a two-step process. Which step comes first? Why?

Genetic isolation because divergence can only happen after there has been the isolation of the species in order for them to be genetically different to the point of speciation.

How do most organisms evolve? Gradualism Stasis Punctuated equilibrium Saltation

Gradualism

Evaluate the following statement: Biological species concept (BSC) defines species based on the process of speciation, while phylogenetic species concept (PSC) defines species based on the evolutionary consequence of speciation.

I think it is useful to associate the phylogenetic species concept to an evolutionary consequence of speciation because that means it can be mapped out (in a phylogenetic tree) with the ancestors and clades. I think that for the biological species concept there should be a bit more detail besides just the process of speciation, perhaps embellishing it a bit more and saying that BSC is based on the process of speciation through reproductive isolation. BSC defines species based on reproductive isolation: two populations are different species if they cannot successfully interbreed. This reflects what we understand as the process of speciation: (1) genetic isolation, (2) genetic divergence. What makes BSC so popular and so useful (for sexually reproducing species) is that it does reflect the process of speciation. PSC defines species by examining evolutionary relationships: species are distinct if they are a basal monophyletic clade, consisting of specific synapomorphies defining the clade. PSC is, in a way, the inverse of BSC; instead of defining species by the process of speciation, PSC defines species as the evolutionary consequence of speciation. Though not as popular as the BSC, PSC can be useful in ways BSC isn't (asexual species, fossils).