Biological Diversity Exam 2 Book Studyguide
Biological Diversity Exam 2 Book Studyguide BSCI 10110
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This 6 page Study Guide was uploaded by Brittany Yee on Saturday March 12, 2016. The Study Guide belongs to BSCI 10110 at Kent State University taught by Dr. Mark W. Kershner in Spring 2016. Since its upload, it has received 51 views. For similar materials see Biological Diversity in Biological Sciences at Kent State University.
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Date Created: 03/12/16
CH 22 BOOK HIGHLIGHTS 22.2 Natural selection and reproductive isolation Speciation is a continuous process and can potentially result in two populations being only partially reproductively isolated o Individuals of 2 populations may be behaviorally and ecologically isolated but between-population mating is still possible and may produce some viable offspring What happens when individuals of 2 populations come in contact depends on the extent of which isolating mechanisms have already evolved. o There may be an intermediate state, in which reproductive isolation is only partial. This could result in partially sterile hybrids. (these hybrids are at a disadvantage with regards to natural selection) Natural selection will favor the allele frequencies that prevented hybridization because the parents who do not produce hybrids have more successful offspring This results in changes in prezygotic isolating mechanisms until reproductive isolation is complete between populations. o This is the process of reinforcement, and what used to be incomplete reproductive isolation is now reinforced by natural selection to cause the populations to be completely reproductively isolated from each other, which completes the speciation process EX of reinforcement: Pied and collared flycatcher birds (pg 442) o The two species are geographically separated (allopatric), but there is a section where the two species live together and sometimes hybridize to produce a few fertile hybrids o In these areas, the new species evolved to have different coloration, and birds want to mate with their own species’ colors o Birds from allopatric pops prefer their allopatric colors to mate with. This means that in areas where the color differences are sympatric due to hybridization, the rate of hybridization is very low, with only a few successful offspring. o *Key point is that when the pops of 2 different species come into contact, natural selection leads to the differences in color patterns which then allows the birds to distinguish individuals from their own species from those of other species which leads to behavioral isolation (prezygotic) Allopatric speciation- the differentiation of populations that are geographically isolated into distinct species Sympartic speciation- differentiation of populations that are in the same geographic location into species Reinforcement- a process that is specific to reproductive isolation that occurs when natural selection favors non-hybrids because of their lack of fertility success. This causes partial reproductive isolation to become complete reproductive isolation *key point- if two populations are already somewhat reproductively isolated due to either prezygotic isolation, postzygotic isolation, or both, then natural selection will increase the fitness of the nonhybrid offspring, which results in speciation *There must be reproductive barriers already existing for speciation to occur. If not, then there would be rapid gene flow because incompletely isolated populations result in immediate gene flow between them, and gene flow will erase differences between populations and preventing speciation 22.3- Role of Genetic Drift and N.S. in speciation We now know reinforcement is driven by natural selection Genetic drift, founder effect, and bottleneck effect can also cause traits that lead to reproductive isolation and speciation EX: Drosophila in Hawaii have closely related species that have different behavioral isolation mechanisms (courtship behavior). Weather phenomenon such as wind caused the flies to drift and experience a founder effect in a new area. Changes in the courtship behavior from the previous species and the new species leads to founder effects Random divergence from genetic drift can cause changes in things that are responsible for reproductive isolation, which can lead to speciation Natural selection’s role in speciation is different from reinforcement because reproductive isolation that occurs because of different environments is part of natural selection. Populations begin to become separate because of environmental pressures, and the natural selection that takes place so that the populations in each environment can adapt*/have improved fitness causes complete reproductive isolation 22.4- Geography of Speciation Speciation is a two part process o 1.) initially identical populations diverge o 2.) reproductive isolation evolves to maintain differences and lead to speciation Issue is that gene flow between populations from either natural selection or genetic drift can stop speciation and erase the differences that each species has specifically developed *speciation is much more likely in geographically isolated populations because they are not in contact with each other (which, if they were, the potential for hybrids arises). o These populations are called allopatric populations, an Ernst Mayr called allopatric speciation the main cause of speciation Sympartic speciation is speciation that occurs without geographic isolation, and is where one initially identical species splits into 2 at a single location. This is not that common 22.5- Adaptive Radiation and biological diversity Adaptive radiation- evolution of closely related species that evolve from a common ancestor by adapting to different parts of the environment Common in environments that have few other species habituating the area and a lot of available resources o Can be caused by extinction of species which leaves a niche open for another population to come and take over *Adaptive radiation requires speciation and adaptation o Speciation occurs, and the new species can go colonize other environments, producing many species per area Adaptive radiation occurs during the allopatric phase or after two species become sympatric and occurs to lessen the competition for resources o This leads to natural selection that would favor species that can use resources available that aren’t already being used by another species 4 examples of adaptive radiation starting on pg 448 22.6- speciation based on how fast it occurs 2 types o 1.) gradualism- the accumulation of small changes Changes that happen slowly and has intermediate forms eventually results in major differences o 2.) Punctuated Equilibrium- long periods of little to no evolutionary change are interrupted by bursts of rapid evolutionary change that occur during speciation CH 23- SYSTEMICS, PHYLOGENIES, COMPARATIVE BIOLOGY 23.1- Systematics Systematics- the study of evolutionary relationships Phylogeny- an evolutionary tree that is constructed by looking at the similarities and differences between species. It represents a hypothesis about patterns of relationship within different species *phylogeny should be looked at by noticing how recently different species share a common ancestor to see how closely related the species are Don’t look at similarity because it doesn’t necessarily correlate with relatedness because evolutionary change isn’t constant 23.2- Cladistics Cladistics- using shared derived characteristics to determine evolutionary relationships Cladogram – a tree diagram that shows relationships of species based on the presence in each species of the derived characteristic. o The derived characteristics are between branch points and are present in all the species ABOVE the mark. Any species below the mark does not have that characteristic. o There can be an outgroup that doesn’t have any of the derived characteristics. Youll be able to find the outgroup by looking at which species is underneath all of the derived characteristic markers. CH 27 VIRUSES 27.1 Nature of viruses All viruses are made of a core of nucleic acid surrounded by a protein. It does not have a cytoplasm and it isn’t a cell o Nucleic acid can be either DNA or RNA Viruses are classified by their genomes- RNA viruses, DNA viruses, or retroviruses o Each type of virus can only replicate in a limited number of cell types/host cells o Suitable cells for a particular virus are called the host range Capsid- a protein sheath that surrounds the nucleic acid core Envelope- REPLICATION Viruses replicated by taking over host cell’s machinery It takes over the host cell’s replication machinery and tricks it into replicating and making more copies of the virus Virions- viral particles that are outside of the cell o they lack ribosomes and the enzymes that are necessary for protein synthesis and nucleic acid replication o virion enters the host cell and takes over the transcription and translation process to make the cell replicate the viral nucleic acid SHAPES 2 main shapes: o 1.) Helical- have a rodlike or threadlike appearance o 2.) Icosahedral- has a soccer ball shape Most animal viruses are this shape 27.2 Bacteriophages Bacteriophage- viruses that infect bacteria o Large amounts of DNA and proteins Ex: E. Coli LYTIC CYCLE - The viral DNA directs the production of new viral particles by the host cell until the virus kills the cell by lysis 1. Attachment phase- virus attaches to the cell wall 2. Penetration- viral DNA injected into cell wall -Lysogenic cycle 3. synthesis- protein and nucleic acid 4. Assembly- involves spontaneous assembly of capsid and enzyme to insert DNA 5. Release- lysis of the cell Viral infections lead to production of new virus particles, which are released by killing the cell (causing it to lyse) when the virus is released, it leads to infection of new cells by the virus LYSOGENIC CYCLE- a latent phase 1.) bacteriophage DNA is inserted into the host chromosome o integration of the bacteriophage into the genome leads to prophage 2.) both the prophage and the host cell DNA is replicated o reproduction of lysogenic bacteria 3.) the prophage exits the bacterial chromosome and the viral genes are expressed in the lysogenic cycle, the DNA segment that is inserted into the host cell is called a prophage. The prophage is replicated with the hosts DNA as the bacteria divides. After replication, it can exist as a prophage or it can enter the lytic cycle and kill the host cell. FLU VIRUS flu viruses are enveloped segmented RNA viruses different strains of viruses differ in their protein spikes o H protein spikes work to allow the virus to obtain access to the host cell’s interior o N protein spikes help daughter cells of the virus break free from the host cell after replication New viruses emerge by infecting new hosts o Viruses are able to jump from species to species. Examples from class are the hantavirus, ebola, and SARS Hantavirus- a single stranded envelope RNA virus that is associated with rodents o Controlling the mouse population has limited the disease Ebola- Hemorrhagic fever- is a filovirus, which means it has an extremely high mortality rate associated with the virus SARS- severe acute respiratory syndrome that is fatal in over 8% of cases. o The mutation of this virus is slow (like with HIV) o It is suspected to have come from civets, which are weasel like mammals HIV HIV (human immunodeficiency virus) causes AIDS (acquired immunodeficiency syndrome) HIV targets t-cells in humans and destroys them. Without t-cells, the body cant fight off infections , which results in death eventually Gp120 is a viral glycoprotein that fits into t-cells. After it is fit into the t-cell, it attaches to the CCR5 receptor and the HIV particle is now brought into the cell Once HIV is inside the cell, viral RNA and reverse transcriptase is released into the cytoplasm, and reverse transcriptase makes DNA complimentary to the viral RNA. The now infected DNA is incorporated in the host’s DNA as a provirus HIV has a high mutation rat because of the reverse transcriptase. It is much less accurate than DNA polymerases. The mutations lead to a mutated gp120 glycoprotein o This altered/mutated HIV particle kills t-cells and ultimately leads to a major decline in the immune system response There are four major approaches to treating HIV virus o 1. Entry inhibitors- blocks virus from getting into the cell by blocking th ability of gp120 spikes to bind to t-cell receptors o 2. Gene therapy- mutating the CCR5 receptor, which prevents gp120 from binding to the receptor and bringing the particle into the cell o 3. Reverse transcriptase inhibitors- blocking replication of the virion inside the host cell. Uses NRTI and NNRTI o 4. Protease inhibitors- blocks new virions from getting into the cell by targeting the capsids in the synthesis stage
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