Module 1 LC Overview

True or false: according to Platt (1964), the purpose of designing and performing an experiment is to prove a hypothesis.

True

False

I haven't done the reading yet!

False

What are the general requirement or characteristic for life on Earth?

Requires energy source, has genetic information, Individuals change over time

What are the 3 domains of life?

bacteria, archaea, and eukaryotes

What factor is required for biological evolution to occur?

genetic variation in the population

What did Darwin propose in his theory of evolution?

Species evolve by natural selection and currently existing species share a common ancestor

How does a scientific theory differ from a scientific hypothesis?

A theory is an overall explanation for a major phenomenon or observation and includes hypotheses; hypotheses treat more specific observations.

What is true about evolution?

Only populations can evolve; individual organisms cannot evolve, and Natural selection does not always result in an ideal fit between an organism and its environment

Which of the following is/are NOT alive?

A. A molecule of DNA

B. A virus

C. A bacterium

D. A human skin cell

E. A human sperm cell

F. A pollen grain

G. A seed

H. A robot which can build nearly identical replicates of itself

A, B, and H

Tardigrades (water bears) are small segmented animals with eight legs. They can survive extreme dehydration (from ~70% to ~10% body water) for decades. How could you demonstrate that dehydrated tardigrades are alive?

A. Record their movement, because movement is characteristic of all life.

B. Record their temperature, because all living organisms maintain body temperatures different from their environment.

C. Record their energy use, because all living organisms acquire and use energy.

D. Wait for 10 years or more to see if they reproduce.

E. None of the options listed demonstrate that the dehydrated tardigrades are alive.

C

What conditions are always necessary for biological evolution?

For biological evolution to occur, the only condition that is needed is heritable variation in a population.

Biological evolution, defined as change in the frequency of heritable variants in a population, can occur in a single generation.

Both selection and random fluctuations can and often do cause differences in the pool of heritable variants in the parent versus progeny generations.

Which of these is/are an example of biological evolution? Select all that fit the definition of biological evolution.

A. After several years of applying the same herbicide to a field, weeds grow that are resistant to the herbicide. The offspring of these weeds are also resistant to the herbicide.

B. An individual goes on an intermittent fasting diet and loses 10% of his body weight over two months.

C. Members of a town population increase in average body mass within a few years after fast-food restaurants open in the town and the primary source of fresh foods are lost after several grocery stores close

D. The global average human height has increased by about 5% (10 cm, or almost 4 inches) over the last century.

A

Some insects are now resistant to all commonly used pesticides. Which is the better explanation for this observation?

A. Frequent contact with pesticides caused mutations that allowed the insects to become resistant so resistant insects became more and more common.

B. Some insects carried alleles for resistance to the pesticide before contact with the pesticides and their numbers increased after pesticides became common.

B

What will happen to a population of snakes if the small mice they normally eat are no longer available and all that is left are larger rats that are more difficult to swallow?

A. Mutations would be induced in the population to allow the snakes to eat rats. The snakes with these mutations would be more likely to survive and reproduce.

B. The snakes would develop wider jaws as they continued to try to eat large rats. The successful snakes would survive and reproduce.

C. The individual snakes that already have slightly wider jaws that allow them to eat rats would be more likely to survive and reproduce.

D. Because the population of snakes is all the same species, they all have the same physical traits. No individual snakes would have an advantage in swallowing rats, and all of the snakes would die.

C

Mammals in Australia are called marsupials, and diverged from the placental mammals very early in mammalian evolution. Australian sugar gliders and North American flying squirrels (see picture) have membranes of skin between their forelimbs and hindlimbs that allow them to glide between tree branches.

What information do you need to determine whether these membranes are homologous or analogous?

Did the common ancestor of these animals have these membranes? If so, then they are homologous; if not, then they are analogous.

These are analogous traits. These membranes in these two distantly-related organisms evolved separately. If they were homologous, we would expect many more mammals would also have these membranes given how long ago these two animals share a common ancestor and how many other mammal species have evolved from that common ancestor.

How might the fossil record test (remember: "test" means FALSIFY) the hypothesis that tetrapod limb bone structures are homologous?

One way would be if fossils of a common ancestor had a different bone structure, or if fossils of the earliest species of each of these groups had different bone structures. Such fossil evidence would support the alternative hypothesis that these groups of animals somehow converged on a common bone structure in their evolutionary history.

How does natural selection explain how bacterial populations evolve resistance to antibiotics?

rare, resistant mutant bacteria in the population survive antibiotic treatment

What conditions lead to evolution by natural selection?

competition for limiting resources, heritable variation in the population

Natural selection works on ____________ already present in a population.

variation

Selection that results in a shift in the population toward one extreme phenotype is best described as:

Directional

Selection that results in elimination of extreme phenotypes and enrichment for the 'average' phenotype in the population is best described as:

Stabilizing

What is the smallest unit that natural selection can change?

a population's allele frequency

What is the smallest unit upon which natural selection directly acts?

an individual's phenotype

Biological fitness is based on:

How many surviving offspring an individual has, relative to others in the population

According to Platt, the author of "Strong Inference," scientists should design experiments in order to ___

disprove as many hypotheses as possible

What are the general characteristics for cellular life on Earth?

All cells require and use energy, have hereditary information, reproduce, and grow.

But not all cells have a nucleus - prokaryotes (bacteria and archaea do not)

Which answer choice does NOT include an evolutionary misconception?

A. Once organisms invaded onto land, they had to evolve effective methods of support against gravity in order to survive

B. Giraffes that can reach leaves higher on the tree have more food, so giraffes stretch to grow longer necks.

C. Frogs that die younger but have more surviving babies than other frogs have higher biological fitness.

D. Viruses mutate so they can be more virulent and infect more hosts.

E. All of these have misconceptions.

C

Explain the misconception(s) about evolution in the statements below:

Life arose in the aquatic environment and later invaded land. Once organisms came onto land, they had to evolve effective methods of support against gravity in order to survive

There are multiple possible logical errors in this statement. Organisms to not evolve because they 'need' to; they evolve because there is heritable variation in the population: any individuals who have a particular trait that causes them to be more reproductively successful will leave more offspring than others, and thus that particular trait will be present in more individuals in the next generation, and so on. There is no 'intention' or foresight in evolution; it only works based on variations in traits already present in the population. New variation arises by mutation, and that mutation can be selected for or against by the environment. In order for organisms to 'invade' land, they had to already be able to withstand the effects of gravity; however, they would become better adapted due to selection on existing and new (due to mutation) variation in the population.

What is required for biological evolution by natural selection to occur?

genetic variation in the population, a selective agent, differences in reproductive success among individuals based on fitness

Myxoma virus infects only rabbits. It spreads by direct contact with infected rabbits, or via fleas or mosquitos that have bitten infected rabbits. Which of these myxoma virus strains have greater evolutionary fitness?

A. a strain that reproduces quickly, producing many progeny in a short period of time, and is nearly 100% lethal (deadly) to the host rabbit in a very short time.

B. a strain that reproduces slowly, producing fewer progeny at a time but over a longer time period, and sickens but does not kill the host rabbit.

B

The non-lethal strain has greater fitness. Although it produces fewer offspring in the short run, by keeping the host alive it can infect other animals the host comes into contact with. The more virulent strain, by killing its host quickly, limits its chances to spread to other animals. This means that while the virulent strain producs more offspring, fewer of those offspring are likely to be successful themselves.

Suppose that we have a scrub desert with light colored sand, and numerous patches of dark-colored rocks. Mice with two copies of a dark fur color allele are dark-colored and blend well with dark-colored rocks. Mice with two copies of a light color allele are light-colored and blend well with the sand. Mice with one copy of each (heterozygotes) are a brown color that does not blend well with either the sand or the dark-colored rocks. As a result, the brown mice are more susceptible to predators. Which type of selection is most likely to operate in this situation?

disruptive selection

A large portion of the corn crop has been genetically engineered to produce a protein that toxic to corn borers, an insect pest of corn (the protein has no effect on mammals). What conditionswould be necessary for the corn borer to evolve resistance to the toxic protein?

The corn borer must have heritable variation in resistance to the toxin (toxic protein).

Ground finches on an island in the Galapagos suffered a population loss during the 1977 drought. Before the drought, finches had an average beak depth of 9.4 mm and ate seeds of various sizes. The drought reduced the number of small seeds on the island, leaving only larger seeds. After the drought few birds survived, and their average beak depth was 10.2 mm (see figure). The average beak size increased during this drought because

larger-beaked birds were already in the population, and they survived better during the drought.

Ground finches on an island in the Galapagos suffered a population loss during the 1977 drought. Before the drought, finches had an average beak depth of 9.4 mm and ate seeds of various sizes. The drought reduced the number of small seeds on the island, leaving only larger seeds. After the drought few birds survived, and their average beak depth was 10.2 mm (see figure). The average beak size increased during this drought, indicating that _________ selection had occurred.

directional

The HLA proteins play an important role in the immune system's ability to recognize different pathogens (infections bacteria and other organisms that cause disease). Therefore the HLA proteins play a fundamental role in the ability of the immune system to detect and fight infections.

There are multiple HLA genes in the human genome, and there are hundreds to thousands of different HLA alleles present in the population for each different HLA gene. Each allele encodes a slightly different version of the HLA protein, and these slight differences mean that each different HLA protein has a slightly different ability to detect different pathogens. Most individuals have different alleles at each of their HLA genes, resulting in ability to dect more types of pathogens.

Balancing selection because no single allele has a consistent fitness advantage over any other allele

Song thrushes, like many birds, hunt by sight. They commonly prey on a species of snail that has many different shell colors. Shell color is genetically controlled. The song thrushes tend to hunt whichever color snail is most common, because it is easiest for the birds to quickly identify this color since it is most common. Over time, this high level of predation on the most common shell color results in fewer of these snails remaining to reproduce and thus most commonly-hunted color becomes less common. This is an example of:

Balancing selection, because no single color allele has a consistent fitness advantage over any other

Song thrushes, like many birds, hunt by sight. They commonly prey on a species of snail that has many different shell colors. Shell color is genetically controlled. The song thrushes tend to hunt whichever color snail is most common, because it is easiest for the birds to quickly identify this color since it is most common. With high levels of predation on the most common shell color, there are fewer of these snails to reproduce and thus most commonly-hunted color becomes less common. The individual song thrushes then switch to hunting a whatever is the new most-common color. These switches can happen many times in a single season.

What is true of the song thrushes in this case?

The individual song thrushes have adjusted their behavior to hunt the new most-common colored snails; this change does not demonstrate evolution

What is the difference between natural selection and genetic drift?

Drift generates a random shift in phenotypic frequencies, while selection generates a shift toward the environmentally favored phenotype.

What mechanism of evolution always increases fitness and leads to adaptation?

natural selection

Acting alone, what mechanism of evolution has the least impact on allele frequencies?

Mutation

What mechanism of evolution results from interbreeding after migration of one population into an area containing another population?

Gene flow

Yes, No, Sometimes: Evolution results in a better match of an organism and the environment.

sometimes

Blind Mexican cavefish (Astyanax mexicanus) live in caves and do not have eyes as adults (though they do form eyes during development). The cave fish diverged from a surface-dwelling population which does have eyes, after small numbers of random surface-dwellling individuals became trapped in cave streams. The cave fish have extremely low genetic diversity compared to their surface-dwelling close relatives (pictured below). This observation is best explained by:

Genetic drift due to founder effect

Which of the following statements about gene flow is/are true?

A. Gene flow can increase genetic diversity in a population

B. Gene flow can prevent a population from adapting to its local environment

C. Gene flow can make two populations more similar to each other

D. None of these statements are true

A, B, and C

Inbreeding can cause increased homozygosity (more homozygous individuals) in the population. What also likely results in increased homozygosity?

Positive assortative mating

Which is an example of random mating (ie, is NOT non-random mating)?

A. A male coyote mates with the available females it encounters as it travels across the coyote-population range

B. A brown beetle mates with other brown beetles, as opposed to beetles that are green

C. A female bird mates with male birds that are more brightly colored than others

D. A mouse mates with other mice that live in the basement of the same building

E. All of these are examples of non-random mating

A

mutation is _________, but evolution can be directed by natural selection

random

A researcher wants to know if gene flow is contributing to evolution of drought tolerance of pitcher plants in a specific bog. To detect whether evolution is naturally occurring in the bog, she could

Determine if the population is in Hardy-Weinberg equilibrium or not.

A population in H-W equilibrium is not evolving; the conditions that establish H-W equilibrium include lack of gene flow into or out of the population. This is a valid question, because although pitcher plants do not migrate, their pollinators may bring in alleles from nearby populations.

An opossum population has a gene with two alleles, A1 and A2. If 80% of the gametes produced in the population contain the A1 allele (the A1 allele frequency is 0.8) and the population is in Hardy-Weinberg Equilibrium, what proportion of the offspring flies will carry both A1 and A2?

0

How can you tell if a population is in HWE?

The population is in HWE if the observed genotype frequencies in the population are p^2, 2pq, and q^2

A mating population contains two alleles, A1 and A2 with the following frequencies: f(A1) = p = 0.7 f(A2) = q = 0.3

And you observed that the actual genotype frequency of the heterozygote was 0.21, you would then conclude:

that evolution is occurring in this population

Why does HW assume an extremely large population size?

large population minimizes the likelihood of genetic drift

In a Mediterranean population of humans, 30% of gametes contain the sickle cell allele, s. If this population is in HWE, then what approximate percentage of the population will be heterozygous at the sickle-cell gene (Ss) and therefore resistant to malaria?

42%

In a Mediterranean population of humans, you observe that 5% of the population has sickle-cell anemia, 50% of the population is heterozygous at the sickle-cell gene, and 45% of the population is homozygous for the normal allele. If q is frequency of the sickle-cell allele in the population, then what is q?

0

In a Mediterranean population of humans, you observe that 5% of the population has sickle-cell anemia, 50% of the population is heterozygous at the sickle-cell gene, and 45% of the population is homozygous for the normal allele. Is this population in HWE?

No

In short-horned cattle, red cattle are homozygous for the red allele, white cattle are homozygous for the white allele, and roan cattle are heterozygotes. Population A consists of 36% red, 16% white, and 48% roan cattle. What are the allele frequencies?

red = 0.6, white = 0.4

Speciation that can occur in a sexually reproducing species split into two populations by a geographic barrier to gene flow is best described as

allopatric

You examine fossils of extinct trilobites. All the specimens look identical and were collected from the same fossil bed. You can assert that they are members of the same

morphological species.

Hybrids occur when:

two species interbreed

Donkeys have 62 chromosomes and horses have 64 chromosomes. When a male donkey mates with a female horse, the hybrid offspring is an infertile mule. Horses and donkeys are (select all that apply):

A. pre-zygotically isolated because they have mismatched chromosome numbers

B. post-zygotically isolated because they have mismatched chromosome numbers

C. not the same biological species because mules are not fertile

D. the same biological species because they can interbreed

B and C

The antennae of male moths can only detect sex pheromones released by a female of his same species. This reproductive barrier is:

Prezygotic

True or False: Speciation always occurs in allopatry because there's no mechanisms for two species to evolve in sympatry.

False

prezygotic reproductive isolation

Pre-zygotic reproductive isolation reduces gene flow between populations by preventing fertilization from occurring via mechanisms such as incompatible mating behaviours, differential mating timing and/or location, or incompatibility between the egg and sperm

Which of the following is a limitation of the biological species concept?

A. it cannot be applied to prokaryotes and other organisms that reproduce asexually

B. it cannot accurately distinguish between species that are capable of interbreeding (for example, in the captivity) but never do in the wild

C. it cannot be applied to extinct species

D. all of these are limitations of the biological species concept

E. none of these are limitations of the biological species concept

D

What mechanism of evolution is central to the Biological Species concept?

Reduced gene flow

Would you expect natural selection to favor prezygotic or postzygotic isolating mechanisms between populations undergoing sympatric speciation, and why?

prezygotic favored

Typically, prezygotic isolation would be favored because selection will favor increased reproduction in individuals that specialize in the habitat (and decreased relative reproduction in those that are different). Specialization could be a preference for a certain scent, food type, egg-laying environment, mating locale, etc.

Some "purebred" dog breeds exhibit high frequencies of a number of genetic disorders including hip dysplasia, epilepsy, and immune-system dysfunction. These effects can be best explained by:

Inbreeding

Variation for traits within a population is a prerequisite for evolution by natural selection because

selective agents act on traits, differentially removing or retaining individuals with certain trait values.

An earthquake wipes out a mainland population of a small flowering herb with highly variable flower shapes. A small remnant contains the seven remaining plants in the population. The most likely outcome for the population as a result of this is

A reduction in floral trait variation

The evolutionary processes that influence population evolution from one generation to the next include

Behavior without an underlying genetic cause, Creation of new alleles in a population, and Random loss of genetic diversity in a population

After genetic drift has occurred:

The population is less genetically diverse than in the previous generation, and The allele frequencies have changed from the previous generation.

The effect of mutation on a population is that it ________ genetic diversity

increases

Suppose that rabbit fur color is controlled by one gene with two alleles. BB individuals are black, Bb individuals are gray, and bb individuals are white. A population has 15 black rabbits, 30 gray rabbits, and 55 white rabbits. If p = the frequency of the B allele, and q = the frequency of the b allele, what is p?

0.3

First determine the actual genotype frequences: 0.15, 0.3, and 0.55

Then determine the allele frequences: p = 0.15 + 1/2 (0.3) = 0.15 + 0.15 = 0.3; q = 0.55 + 1/2(0.3) = 0.55 + 0.15 = 0.7

Suppose that rabbit fur color is controlled by one gene with two alleles. BB individuals are black, Bb individuals are gray, and bb individuals are white. A population has 15 black rabbits, 30 gray rabbits, and 55 white rabbits. What does HWE predict for the genotype frequency of the heterozygote?

0.42

First determine the actual genotype frequences: 0.15, 0.3, and 0.55

Then determine the allele frequences: p = 0.15 + 1/2 (0.3) = 0.15 + 0.15 = 0.3; q = 0.55 + 1/2(0.3) = 0.55 + 0.15 = 0.7

Then use the allele frequences to determine the predicted genotype frequencies: p^2 = 0.3 x 0.3 = 0.09; 2pq = 2 x 0.3 x 0.7 = 0.42; q^2 = 0.7 * 0.7 = 0.49

Suppose that rabbit fur color is controlled by one gene with two alleles. BB individuals are black, Bb individuals are gray, and bb individuals are white. A population has 15 black rabbits, 30 gray rabbits, and 55 white rabbits. Is this population evolving at the fur color gene?

yes

Mutation on its own is unlikely to play an appreciable role in speciation, except when the mutation:

Significantly reduces gene flow

Archaea and Bacteria are both prokaryotic forms of life. Is the term "prokaryote" monophyletic or paraphyletic?

Paraphyletic; prokaryotes are paraphyletic because the group does not include the common ancestor of archaea and eukaryotes

a clade is also called a

monophyletic group

Which rock type contains fossils of once-living organisms?

sedimentary rocks

Dating and ordering the geological record is complicated by (select all that apply):

A. Sedimentation in lakes and seas.

B. Uplift

C. Unconformities

D. Radioactive isotopes in the rock

E. Erosion

B, C, and E

Carbon-14 decays to nitrogen-14 with a half-life of approximately 5700 years. After 57,000 years, approximately what fraction of the initial carbon-14 would be left in an organic sample?

1/1000

Put these events in Earth history in order. Oldest < second oldest < youngest

- production of oxygen by photosynthetic organisms

- origin of eukaryotic cells

- earliest evidence for life on Earth

- appearance of first tetrapods on land surfaces

- Cambrian "explosion"

earliest evidence for life on Earth < production of oxygen by photosynthetic organisms < origin of eukaryotic cells < Cambrian "explosion" < appearance of first tetrapods on land surfaces

Which free living cells were the earliest contributors to the formation of Earth's oxidizing atmosphere?

Cyanobacteria

In the Cambrian 540 MYA, which of the following was true (select all that apply):

A. A major adaptive radiation occurred

B. Atmospheric oxygen reached levels similar to now

C. A mass extinction occurred

D. UV on the land surface increased

E. The earth's temperature was cooler than it is today

A and B

Due to plate tectonics, for the past 560 million years, the continents that we see today

have merged and split apart over millions of years

If two continents converge and are united, then the collision should cause

a net loss of coastal land and water habitats.

The Earth's climate for the past 10,000 years (the period of recorded human history), has been

cooler than for most of Earth's history

Sedimentary rocks form...

on top of older, existing rocks

A fossil is embedded in a rock layer which contains equal amounts of 40-Potassium and 40-Argon. 40-Potassium decays to 40-Argon with a half life of 1.25 billion years, and there is no Argon 40 initially present in igneous rock when it first solidifies. How old is the fossil?

1.25 billion years

There are equal amounts of parent and daughter isotope (1:1). This means that the ratio of the amount of original parent isotope remaining to total isotope (parent + daughter) is 1:2 or 1/2, so one half life has passed. K/Ar half lives are 1.25 BY.

If the half-life of carbon-14 is about 5,700 years (for the sake of ease of calculations, approximate this to 6,000 years), then a fossil that has one-sixteenth the normal proportion of carbon-14 to carbon-12 should be about how many years old?

24,000

First calculate the number of half-lives that have elapsed. 1/16 = 4 half lives (1/2, 1/4, 1/8, 1/16). Then multiple the number of half-lives by the amount of time required for 1 half-life to elapse. 4=5,700 = 22,800 years

Increasing concentrations of atmospheric oxygen:

A. Created ideal conditions for the spread of anaerobic organisms

B. Was caused by the evolution of oxygenic photosynthesis

C. Caused a major extinction event among obligate anaerobic organisms

D. May have ultimately allowed for evolution of larger body size and greater organismal mobility

E. Caused iron in ocean water and terrestrial rocks to rust (oxidize).

B, C, D, and E

On a species level, mass extinctions function most analogously to:

Genetic drift

Adaptive radiations:

A. Can occur as a result of new ecological niche opportunities

B. Can occur due to new adaptations such as limbs or wings

C. Have occurred multiple times throughout Earth's history

D. Often occur after major extinction events

A, B, C, and D

Archaea are most closely related to:

eukaryotes

At the beginning of the oxygenic revolution, you would predict that cyanobacteria populations were:

Increasing in size

The Cambrian explosion describes

an adaptive radiation

All eukaryotes have mitochondria, but only plants have chloroplasts, which enable the formation of chemical energy from light through the same mechanism as in cyanobacteria. The endosymbiosis theory would predict that:

A. mitochondria were engulfed in the ancestor of all eukaryotic life; chloroplasts were engulfed later.

B. chloroplasts were engulfed in the ancestor of all eukaryotic life; mitochondria were engulfed later.

C. Mitochondria and chloroplasts were engulfed by two separate and independent lineages and do not coexist.

D. Any of these is possible.

E. Either A or B but not C.

A

Tritium has a half-life of 12.3 years. What fraction of its original tritium content will remain 37 years after an organism's death?

1/8

The half-life of carbon-14 is approximately 5730 years (you can approximate this to 6000 years). For carbon-14/carbon-12 ratios, the practical limit of detection is about 0.1%, or 1/1000 of the original carbon-14/carbon-12 ratio. Approximately how many half-lives does this correspond to? What's the oldest fossil that carbon-dating can be used on?

10; 60,000

An early consequence of the release of oxygen gas by oxygenic photosynthesis was to

cause iron in ocean water and terrestrial rocks to rust (oxidize).

The oldest fossils of eukaryotic cells appeared

about 1.5-2 billion years ago, after the first small rise in atmospheric oxygen