BIOLOGY 171 UMICH EXAM 3 LEARNING OBJECTIVES

Explain what the "Cambrian explosion" represents, when it occurred, and how it is an example of adaptive radiation.

The rapid diversification of multicellular animal life around the beginning of the Cambrian Period, resulting in the appearance of almost all modern animal phyla.

Explain how fossils form and the limitations of the fossil record

Most form when an organism is quickly buried in sediments before decomposition occurs.

Limitations: habitat bias, taxonomic bias, temporal bias, abundance bias

Habitat bias: better record for aquatic organisms

Taxonomic bias: better record for organisms with hard parts

Temporal bias: better record for more recent organisms

Abundance bias: better record of common organisms

Describe the two main types of fossils

Body fossils: direct evidence, fossil bones or shells, organisms preserved in ice, insects trapped in amber, petrified wood

Trace fossils: indirect evidence, footprints, coprolites (feces), burrows, tracks, chemical signatures

Explain how paleontologists and geologists can estimate dates of important events in Earth's geological history using radioactive decay of different isotopes (such as C14 and U238); be able to apply these principles to understand the age of a fossil if given information on radioisotopes and their decay rates.

Archaeologists commonly use the radioactive decay of the isotope carbon-14, or 14C, to date wood and bone. After death, the unstable 14C in these materials begins to break down, losing an electron to form 14N, a stable isotope of nitrogen. Laboratory measurements indicate that half of the 14C in a given sample will decay to nitrogen in 5730 years, a period called its half-life (Fig. 23.17). Armed with this information, scientists can measure the amount of 14C in an archaeological sample and, by comparing it to the amount of 14C in a sample of known age—annual rings in trees, for example, or yearly growth coral skeletons—determine the age of the sample.

Describe the main events that occurred in the Hadean, Archaean, Proterozoic and Phanerozoic eons.

Hadean (4.5BYA): Bombarded by meteors, high volcanism, no life, no oxygen, after cooling there was liquid water 4.3BYA

Archaean (4 to 2.5BYA): Oceans, volcanism, no oxygen, first cells (prokaryotes, chemical signs, bacteria), origin of oxygenic photosynthesis (cyanobacteria, 3.5BYA)

Proterozoic (2.5BYA to 542MYA): stromatolites, atmosphere and ocean surface oxygenated 2.4BYA, oxygen catastrophe (mass extinction event), first eukaryotic cells 1.8BYA, first animals (sponges) ~600MYA

Phanerozoic (540MYA): Cambrian animal radiation 540MYA, plants & fungi on land 475MYA, arthropods on land 420MYA, vertebrates on land 365MYA, End-Cretaceous extinction 65.5MYA, first primates 65MYA, 200,000YBP first homo sapiens, 60,000 Homo sapiens out of Africa

Describe the relative order and approximate timing of the following events: formation of Earth, first molecular & fossil evidence of cells, evolution of photosynthesis, development of oxygen-rich environments, first eukaryotic cells, first animals, Cambrian explosion, colonization of land first by arthropods then vertebrates, End-Cretaceous extinction, diversification of birds & mammals.

1.formation of Earth (4.5 BYA, Hadean Eon)

2. first evidence of prokaryotic cells (~3.5 BYA, Archean Eon)

3. evolution of photosynthesis (3.5 BYA, Archean Eon)

4. development of oxygen-rich environments (2.4 BYA, Proterozoic Eon)

5. first eukaryotic cells (~1.8 BYA, Proterozoic Eon)

6. first animals (600 MYA, Proterozoic Eon)

7. Cambrian explosion (540 MYA, Phanerozoic Eon)

8. colonization of land by plants (475 MYA, Paleozoic Era)

9. colonization of land first by arthropods (420 MYA, Paleozoic Era)

10. and then tetrapods (365 MYA, Paleozoic Era)

11. first flowering plants (~125 MYA, Mesozoic Era)

12. first primates (~65 MYA, Cenozoic Era)

13. first hominins (~7 to 5 MYA, Cenozoic Era)

14. first Homo sapiens (Cenozoic Era, Neogene Period, 200,000 years ago)

Explain how mass extinctions differ from background extinctions and how they provide opportunities for adaptive radiations to occur.

Mass extinctions differ from background extinctions because they involve the destruction of over 50% of species. Adaptive radiations occur when a single ancestral species rapidly diversifies into a large number of descendant species; these descendants are genetically diverse and have different morphologies that occupy distinct habitats. Adaptive radiations are a major pattern in the history of life and occur when new ecological opportunities arise and/or when new morphological innovations arise. In the fossil record, we often see adaptive radiations following mass extinction events because they provide new ecological opportunities, after resources become available.

Describe the likely cause of the End-Cretaceous mass extinction.

The cause of the End-Cretaceous mass extinction was an asteroid impact. This created a massive dust cloud which blocked out the sun, leading to an "impact winter", with a 7 degree decrease in temperature and a decrease in photosynthesis for greater than a year. The asteroid also hit sulfur-rich rock which led to sulfuric acid "rain".

Provide evidence that birds are dinosaurs, including their shared, derived traits.

-Theropod dinosaurs and birds both have hollow bones

-Feathers (even though the structure and function has changed over time)

-Phylogenetic analysis of collagen protein extracted from theropod fossils and modern birds shows they are closely related

-Homologous bone structures including furcula, semilunate carpal, and hollow pneumatic bones

Shared derived traits: Furcula (wishbone), semilunate carpal (pinky can touch wrist), hollow pneumatic bones (SDT of dinosaurs)

Explain how plastics enter food webs, what potential impacts they can have on food webs, and give evidence for the relative sizes of different plastics found in the Great Lakes.

Plastics enter food webs from pollution and they can cause animals to build up plastic in their stomachs and make them feel full, which can actually lead them to starvation. 1 in 4 fish and 1 in 3 bivalves collected in the Great Lakes contained plastic fibers in their guts.

Describe how birth, death, immigration, and emigration influence population growth rate and population size

Emigration and death rates decrease/subtract from population growth rate and population size, while immigration and birth rate add to it.

Growth rate= (birth rate +immigration)-(death rate+emigration)

Describe how absolute numbers of births, deaths, immigrants, and emigrants relate to birth, death, immigration, and emigration rates respectively.

B=number of births (b)between times 0 and 1

D=number of deaths(d) between time 0 and 1

I=number of immigrants (i) between times 0 and 1

E=number of emigrants (e) between times 0 and 1

Define the geometric rate of increase, λ, and per capita growth rate, r, and describe how they can be used to understand how populations change over time.

λ expresses a population's growth rate over a discrete interval of time (e.g. 1 year),The analogous measure for a population at any particular instant in time is r, which is known as the instantaneous per capita growth rate.

Explain the relationship between lambda (λ) and r.

λ=e*r

r= ln(λ)

Recognize that population growth rate is constant under exponential growth, but that population growth slows as population size increases under logistic growth.

Ok

Explain why populations do not grow exponentially forever

Population growth cannot occur indefinitely due to resource limitation. Possible limiting resources include food, space, nutrients, nesting sites, etc. These are called density-dependent factors.

Identify exponential vs. logistic growth curves.

Ok

Explain the factors that influence the per capita growth rate (r) of populations undergoing logistic growth.

Many factors can keep a population below K. Predation and parasitism are two of them, as well as population density. For example, a high population density of fish in a pond increases the likelihood of infection by viruses, bacteria, and fungi because these agents are transmitted from fish to fish. Predation and parasitism can reduce the population size below K, but they do not change K itself.

Compare and contrast density-dependent and density-independent factors.

Density-dependent: At low density, food and other resources do not limit growth, but as density increases, they exert more and more influence on population growth, spurring competition for available resources. for example, food availability

Density-independent: influence population size without regard for the population's density. They include events like severe drought or a prolonged cold period, either of which can cause widespread mortality independent of population density. for example natural disasters.

Define population regulation and summarize the factors that regulate population growth.

Population regulation: attract to equilibrium density

Only biotic factors can "regulate" a population - and, of the biotic factors, only those that add a negative feedback (NOT mutualism)

Predation, competition, herbivory, and parasitism can regulate a population.

Compare and contrast herbivory, predation, and parasitism; also be able to compare these with mutualism, competition, commensalism and symbiosis, and understand what the term "enemy-victim" means.

Predation (+/-): consumption of a consumer

Herbivory (+/-): consumption of a primary producer

Parasitism (+/-): feeding off any consumer

Mutualism (+/+): benefits both organisms

Competition (-/-): loss for both organisms

Commensalism (+/_ ): benefit for one organism and the other in unaffected

Symbiosis: the interaction between two different animals

Energy-victim interactions (+/-): include predation, parasitism, and herbivory

Compare and contrast inducible and constitutive defenses.

Constitutive defenses: always present at the same concentration

Inducible defenses: produced more when the plant is damaged (present at low levels then induced to higher levels or not present at all then made)

Explain how plant defenses can be co-opted by their herbivores.

For example, the monarch butterfly feeds off of milkweed. Milkweed produce toxins and a quick setting glue. Monarch butterflies have evolved to be able to feed on milkweed despite their defenses. They also "steal" the plant's defenses and use them to defend themselves.

Describe how predators and parasites can regulate prey/host population sizes.

Hare experiment where predation and food availability control population size when lynx are present

Explain how predators can change prey behavior and influence all vital, and how they can exert strong selection on prey

-Predators and parasites affect per capita rates; Emigration is high because prey leave habitats when predators are present

Immigration is low bc prey don't come into an area where predators are present

Birth is low bc prey have reduced feeding rates when predators are nearby since they are stressed

Death is high from being killed

Puts prey under strong selection to avoid predation by being cryptic, higher speed and agility, being poisonous, or mimicking something dangerous

PARASITES: alter host behavior by promoting the transmission of the parasite

Explain why plants must have colonized land before animals.

Because most terrestrial animals feed off of plants. Plants came about in 475 MYA.

Explain the distinction between obligate versus facultative parasites and describe the ways biologists categorize parasites.

Obligate parasites need one or a few types of host in order to thrive, so if they are unable to reach this species their life cycle ends.

Facultative parasites can survive in many different host species in order to complete its life cycle.

Explain how parasites change host behavior and influence host population size; also explain their importance in food webs and how they can dominate biomass in ecosystems.

Parasites can change host behavior if they need different kinds of hosts to continue their life cycle. For example, one kind of parasite needs a mammal for its asexual life cycle and then a cat for its sexual life cycle. If the parasite starts in a mammal like a rodent, it will alter the rodent's behavior in order to increase the chances of being transmitted to a cat. So, rather than making the rodent scared of cats, it will make the rodent want to be near cats, increasing the changes of being transmitted to its next life cycle. EX. Mice being attracted to bobcat urine when infected with Toxoplasma.

Explain how the nature of interactions between species can change as environmental conditions change.

A mutualism can quickly become a commensalism or parasitism when an individual stops benefiting or is negatively affected. As resources available change, the interactions evolve.

Arthropods

420 MYA

Exoskeleton made of chitin

Joined appendages

Molting

Metamorphosis

Dominant herbivores

MOST are insects

Responsible for 80% of vegetation consumed

Describe how monarch butterflies co-evolved to be a main herbivore of milkweed.

The milkweed developed a toxic substance to prevent monarch caterpillars from eating it and then the butterfly adapted the ability to eat the milkweed and not be affected by the toxin.

Hexapods

Have a body with 3 segments (head, thorax, abdomen)

6 legs attached to thorax

Describe the set up and results of the lynx and hare predator-prey experiment and the experiment that demonstrated the effects of Toxoplasma on host behavior.

Lynx & Hare: Predators, food availability, or a combination of both these factors drive the hare population cycles.

Toxoplasma: The presence of toxoplasma can cause the rats to be sexually attracted to the cats.

Explain how competition reduces organismal growth rates, survival, fitness, and/or population growth rates for both species involved.

an interaction that results in each species having reduced fitness; occurs over limited resources; can be intra or interspecific, direct or subtle; asymmetric

Compare and contrast fundamental and realized niches.

Fundamental niche: is all the habitats and interactions a species can have

Realized niche: the niche in presence of enemy-victim interactions. usually smaller than fundamental niche, but can be larger with mutualisms.

Compare and contrast the conditions that favor species coexistence with those that lead to competitive exclusion

competitive exclusion occurs when competition is asymmetric and niches overlap causing the stronger species to win causing the other species to go extinct; coexistence occurs when the competing species have the same fitness

Explain the long-term consequences of competition; be able to describe and identify resource partitioning and character displacement

character displacement and resource partitioning are long-term consequences of competition

character displacement: evolutionary change in species traits which allows co-occurring species to use different resources

resource partitioning: evolutionary change in resource use by coexisting species

Describe and explain the setup, results and conclusions of Connell's field experiment on competition between two barnacle species.

Joe Connell on factors controlling distribution of two barnacles species on rocky shores of atlantic coast. The smaller species(chthamalus) was on the top in the upper inertidal level. and the bigger one(semibalanus) was submerged. He removed the half of the semibalanus of each rock and measured the survival of the chthamalus. He moved rock to lower levels. The semibalnus does not excluded chthamalus from the upper tidal is aboitic factors.Barnacles can only feed while summered the higher in the shore the less food and growth. the different hypothesis1)adult chtamalus are competitively excluded from lower interidal by the semibalanus2)adult chthamalus do not thrive in the physical condition of the lower interidal.

Explain how mutualism increases organismal growth rates, survival, fitness, and/or population growth rates for both species involved.

mutualism is a interaction that benefits both organisms involved; all mutualism have costs for each species but benefits outweigh the costs; interactions are dynamic and can be parasitism when the cost outweigh the benefits

Explain how mutualisms between mycorrhizal fungi and land plants work and how the interaction improves fitness for both the bacteria and the plant species. Be able to compare and contrast mycorrhizal fungi-plant and Rhizobium bacteria-legume mutualisms.

the fungi help plants take up phosphate and other nutrients; the plants supply the fungi with carbohydrates and other sugars; more than 90% of land plants have this fungi on their roots Rhizobium bacteria-legume: fixes nitrogen for the atmosphere, ammonia turns into proteins for the plants, plant provides shelter for the bacteria

Describe some of the organisms that can fix nitrogen

Rhizobium bacteria, Trichodesmium at the bottom of the ocean fixes nitrogen, phytoplankton

Describe the basics of plant reproduction and explain how plants and pollinators are adapted to each other as part of plant-pollinator mutualisms

plant reproduction:

pollination: movement of pollen grains to stigma of another flower

fertilization: sperm fertilizes egg and plant embryo forms

Explain how mutualisms between angiosperms and pollinators work and how the interaction improves fitness for both interacting species

plant is fertilized and insect gets pollen/food

Describe how mutualisms are vulnerable to cheating, and be able to give an example of cheating in an actual mutualism.

Associations are not fixed—they can change over time. A mutualism can in some cases become antagonistic if one of the partners "cheats" by imposing a larger cost than benefit on the other. In fact, mutualisms that are loose associations among changing partners can become one sided rather quickly. For example, many plants have evolved tubular flowers that guide bees past their anthers or stigma on the way to the nectar at the base, taking just a little more time from bees who try to visit as many flowers as possible. Some bees have short-circuited this plant mechanism by nipping the flower base from the outside and then drinking the nectar without pollinating the flower. Most plants have enough successful pollination to ensure seed production, but losses from cheating can still be costly.

Explain how the nature of interactions between two interacting species can change as experimental conditions change

each species involved in an interaction exerts selective pressure on the other so that they evolve together

Explain the evidence for the theory of endosymbiosis, which explains the origin of chloroplasts and mitochondria in eukaryotes

- Mitochondria and Chloroplasts are the same size as alpha-proteobacterium and cyanobacteria

- DNA of chloroplasts is closely related to cyanobacteria

- DNA of mitochondria is closely related to alpha-proteobacterium

- Mitochondria and Chloroplasts have double membranes, which is consistent with engulfing mechanism.

- Mitochondria and chloroplasts divide by binary fission like bacteria

- Mitochondria and chloroplasts contain their genome in a circular DNA molecule like cyanobacteria and alpha-proteobacterium

Explain what the arrows represent in food chains and food webs and why the arrows go from the organism being consumed to the consumer

It represents energy flow between organisms

Define how ecologists use the term "omnivory"

- Trophic Omnivore: organism that feeds on multiple levels on the food web.

- Primary Consumer: herbivores

- Primary Producers: plants

- Secondary Consumers: eat primary consumer; carnivores (meat-eaters) and omnivores (plants and meat eaters)

- Tertiary Consumers: organisms that eat secondary consumers and primary consumers

Explain what the trophic pyramids represent

Energy/carbon flow through various communities; as the pyramid goes from bottom to top, energy keeps on decreasing. Only about 10 percent of the energy of one trophic level is transferred to the next. Pyramids start with a wide base with the primary producers (most energy) and ends with a skinny top (least energy).

Explain how interactions among species can generate indirect effects

Indirect effect: impact of one species on another, mediated by a third species.

Trophic Cascades: type of indirect effect; when a top predator influences the density of species at all trophic levels below them.

Example: wolves eat herbivores, which decreases the population of the herbivores. The result of this is an increase of population of the primary produces, since there aren't a lot of herbivores.

Distinguish among keystone species, dominant species, and ecosystem engineers

- Keystone Species: not very common (low biomass) but has a high indirect impact on overall community.

- Dominant Species: very common species with a large impact on overall community.

- Ecosystem engineers: creates, maintains, destroys, or in some other way substantially alters a habitat.

Explain how keystone species impact community structure and composition

they impact the community structure and composition indirectly.

Example: wolves eat herbivores, which decreases the population of the herbivores. The result of this is an increase of population of the primary produces, since there aren't a lot of herbivores.

Explain how trophic cascades can affect community composition

- Influence energy flow at multiple trophic levels as well as population sizes of many trophic levels.

Explain how omnivory complicates our ability to make predictions about the effects of consumer removal on food web dynamics

In cases where omnivore is present, ecologists require data on the strength of direct and indirect effects, in order to predict the effect on community dynamic.

Explain how parasites can impact community structure

- Less complex food webs

- Parasites can affect host populations by influencing host mortality, fecundity, growth, nutritional status, energetic requirements, and behavior

Explain how consumption efficiency, assimilation efficiency, and production efficiency combine to determine trophic efficiency

Consumption efficiency: the fraction of production at one trophic level that is consumed by the next.

Assimilation efficiency: the fraction of food that is consumed that is assimilated.

Production Efficiency: the fraction of food that is assimilated that is turned into consumer biomass. Trophic Efficiency= CE AE PE

If given specific information on consumption efficiency, assimilation efficiency, and production efficiency , apply that information to calculate how much production there would be at a higher level

Trophic Efficiency= CE AE PE

If you are not given specific information on CE, AE, and PE, apply the rule of thumb regarding trophic efficiency to calculate how much production there would be at a higher trophic level.

If CE, AE, or PE is not provided, then only about 10 percent of the energy of one trophic level is transferred to the next.

Describe the basic structure of a virus

-DNA or RNA (but not both) surrounded by a protein coat

-Linear, circular, or segmented genome

-single stranded or double stranded

Explain how viral replication occurs

1. Virus attaches to receptor on cell surface

2. Virus breaches cell membrane; injects nucleic acid into cell

3. Viral nucleic acid replicates using host cell machinery

4. New viral genome and proteins are packaged into particles & released

Explain the factors that allow an infectious disease to (re)emerge

-high rates of travel

-increases in human population size and risky behaviors

-increased urbanization

-encroachment on wilderness areas (contact w/ animal reservoirs)

-evolution of pathogens (drug resistance)

-environmental change (weather, vectors)

-reduced vaccination rates

-health inequalities

Explain the factors that describe the spread of an emerging infectious disease

Infectious period: time in which the disease can be transmitted

Contact rate: frequency of contact between infected and susceptible

Transmission efficiency: Likelihood of transmission between infected and susceptible

Explain why R0 is important and how it can be used to inform vaccination programs

Important because the R0 value can tell us whether the # of cases of infection in a population is increasing, decreasing, or being maintained.

Can be used to inform vaccination programs because we can calculate how much of the population needs to be vaccinated in order for herd immunity to work (p=1-1/R0)

Explain how vaccination and herd immunity work, and how vaccination campaigns are used to try to eradicate some infectious diseases

Vaccination: an immune response is generated by receiving injections of a weakened pathogen or antigens.

Herd immunity: The chain of transmission is broken because 1-1/R0 of people are vaccinated and protect those that are not vaccinated.

Explain why pathogens rarely evolve resistance to vaccines

Variation: vaccines are given preventatively (small population size)

Selection: vaccines induce immune responses against multiple targets.

Compare and contrast zoonotic diseases with vector-borne diseases

Zoonotic: a disease that moves between non-human animals and human populations. Example: Ebola

Vector-borne: one that is transmitted between hosts via a vector, most commonly an arthropod such as a mosquito or tick. Example: Lyme disease

Describe the structure of HIV's genome, explain how HIV enters its host cell, how it converts its RNA into DNA into the host cell's genome, the types of cells it infects and how it attacks the immune system

Genome: single-stranded RNA. Attaches and fuses to host cell gives some of membrane to host cells, the Reverse Transcriptase allows it to convert RNA into DNA which allows the DNA to be integrated into the host genome, new copies of the HIV leave infected cell and takes some membrane of the host cell for itself and infects other cells. It attacks the immune system by Infecting and destroying helper T-cells and macrophages which are two key components of the human immune system. When the helper T-Cell count drops, the body is less able to fight all infections. When there are less than 200 T-cells left is when the onset of AIDS occurs.

Explain the evolutionary origins of HIV; be able to state the organisms in which HIV originated

Does not belong in the domain of life because it is a virus. the chimpanzee version of the immunodeficiency virus (called simian immunodeficiency virus or SIV) most likely was transmitted to humans and mutated into HIV when humans hunted these chimpanzees for meat and came into contact with their infected blood. Common ancestor between SIV and HIV that became current SIV and HIV strains. Originated in chimps and sooty mangabey

Explain how evolutionary processes can help us explain why HIV is so hard to treat/cure as well as inform treatment strategies

-HIV has high genetic variability (high mutation rate)

-It integrates its genome into host's DNA

-HIV attacks the immune system directly and destroys helper T cells

Treatment strategies: Can be expensive and HIV strains become resistant,Block entry/Prevent fusion, Block reverse transcriptase, Block integrase (prevent HIV's DNA into host DNA), Block Protease (prevent virus from assembling functional proteins), Combination drug cocktails of reverse transcriptase, protease, and integrase inhibitors are used to stop/slow viral replication, ART= anti-retroviral therapy, HIV PrEP: combo of 2 drugs and prevents HIV transmission

Describe the processes by which viral DNA can become part of the human genome

By injecting its DNA into the host cell

For measles, understand what has allowed it to reemerge in recent years, its effects on other infectious diseases, and the benefits of vaccination.

Measles has reemerged in recent years because of reduced vaccination rates and it has a high R0. Children who survive measles are more vulnerable to other diseases for 2.5 years after recovery because measles suppresses the immune system. Therefore, there is a positive (slope) relationship between measles and death from other diseases. The benefits of vaccination is that there can be eradication of this disease can allow for immunity in a population.

For Ebola, describe the timing and location of outbreaks, the likely reservoir host, modes of transmission, the biology of the virus, the source of the 2014 outbreak

Ebola:

-first discovered in 1976

-Filoviridae virus family; 5 ebola species

-Early outbreaks in Central Africa, near rainforests

-Death rates 50-90%

-Previously rare disease

-ssRNA virus, but NOT a retrovirus

-only codes for 7 proteins

-For sure ZOONOTIC DISEASE FROM BATS, MICE, CHIMPS, ANTELOPES; occasional spillover events-in Guinea, Sierra Leone, and Liberia in 2014

Explain what ring vaccination is and how it has been used to combat Ebola

In 2018, health authorities used a ring vaccination strategy to try to suppress the 2018 Équateur province Ebola outbreak. This involved vaccinating only those most likely to be infected; direct contacts of infected individuals, and contacts of those contacts.

Explain how effective reproductive number, R, differs from R0, and how R changes over the course of an epidemic.

R0: the expected number of secondary cases one case produces on average in a completely susceptible population

R: the expected number of secondary cases one case produces on average in a population that need not be completely susceptible

During the course of the epidemic, R starts at R0, but decreases as the number of susceptible individuals decreases. At the peak of the infection, R=1, and R<1 thereafter.

Explain how humans affect the evolution of organisms including bacteria and pathogens

Human activities are changing environments and causing unintended natural selection because we overuse antibiotics which causes mutations in the bacteria which causes allele frequencies to change in one direction (directional selection). Discrete traits can become fixed in populations (resistant genotype). Many people don't complete their antibiotic treatments, which favors the resistance strains

Explain what antibiotics are, what organisms they target, and where they come from

Antibiotics: substances (originally) produced by microorganisms that kill bacteria or inhibit their growth by: blocking cell wall synthesis, blocking cell membrane synthesis, blocking protein synthesis(either transcription or translation step), block folic acid synthesis

Explain how bacteria can evolve resistance to antibiotics

-destroy it via antibiotic inactivating enzyme

-pump it out via efflux pump

-prevent it from entering cell

-change shape of drug's target molecule

Explain how natural selection allows resistance to spread quickly

When a mutation occurs that makes a pathogen resistant to antibiotics or treatments, that mutation is advantageous to the pathogen and more of the surviving pathogens will be the ones with the mutation and they will reproduce more pathogens with that mutation; because the mutation or resistance is advantageous it is more likely (naturally selected) to be passed onto the next generation. Bacteria reproduce by binary fission so if they have the resistance mutation then all of its offspring will as well; Fast reproduction, high mutation rates, horizontal gene transfer, strong selection pressure

Describe the general pattern that occurs in terms of the introduction of new antibiotics and antimalarials and the emergence of drug resistance in pathogens

High mutation rates; once resistance is developed to one antibiotic the more likely it is that they will develop resistance to another antibiotic. The stronger the antibiotic and selection pressure and combined with binary reproduction creates fast evolution.

Explain why tuberculosis is re-emerging as a major infectious disease; describe the biology of Mycobacterium tuberculosis

-Encapsulated bacteria are hard to kill and it requires long periods of antibiotic treatment to kill all the bacteria

-Many people stop taking antibiotics before the infection has cleared, thus favoring the resistant strains (selection)

-Cases can be asymptomatic, allowing spread by people who are unaware that they are carrying the disease (latent TB)

-Crowded conditions also foster spread

-Immune-compromised people are at particular risk (e.g. people suffering from AIDS)

Explain how understanding evolution informs treatments of tuberculosis

We understand the evolutionary process where TB needs to have a selective advantage to survive; Because we understand the frequency of mutation and natural selection we can better determine treatment plans with multiple drugs; also depending on if it is latent or active TB

Explain how humans change the selective environment for the malarial parasite, Plasmodium, and which part of the life cycle occurs in which hosts

Humans change the selective environment for Plasmodium by focusing on eliminating the vector (mosquitoes) via mosquito-repellant nets, insecticides, and genetic engineering. Sexual cycle occurs in mosquitoes. Asexual cycle occurs in humans.

Explain how humans have changed the selective environment for the malaria vector, Anopheles mosquitoes

Genetically engineered sterile mosquitoes

Insecticides, but that also causes stronger selection

Place Mycobacterium (TB pathogen), Plasmodium (malarial parasite), and mosquitoes on the tree of life

Mycobacterium: Bacteria

Plasmodium: Eukarya

Mosquitoes: Eukarya

Explain how the loss of antimicrobial drugs such as antibiotics would impact humans

-People could die from getting cut and having a bacterial infection

-Immune-compromised people would be more at risk

-Things like strep-throat and pneumonia could kill you normally

Explain how we can reduce/slow the spread of drug resistance in pathogens

-use antibiotics only for bacterial infections

-cycle antibiotics in hospitals

-don't use antibiotics or antimicrobials in meat production

Describe three ways that bacteria can transfer genetic material

Conjugation: DNA (usually a plasmid) from a donor cell is transferred through a pilus into the recipient cell

Transformation: DNA released into the environment by dead cells is taken up by a recipient cell

Transduction: DNA is transferred from a donor to a recipient cell by a virus