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BIO-203: Ecology, Evolution, and Diversity > Exam 2 > Flashcards

Exam 2 Flashcards

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1
Q

What is Evolution?

A

change in the genetic composition (allele frequencies) of a population from GENERATION TO GENERATION

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2
Q

What is Biodiversity?

A

variation of life at ALL LEVELS of biological organization

referring to the SUM TOTAL of life forms across an area as well as the range of DIFFERENCES between these forms

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3
Q

Why is Biodiversity important?

A

-Rich biodiversity in nature
-Pattern of SHARED characteristics
-Organisms suited for life in their local environments
-It provides ecosystem services (food, fiber, medicine, clean water, air, pollination)
-the potential loss of medicines and other products yet undiscovered from threatened species
-potential loss of genes, some of which may code for proteins useful to humans
-risk to global ecological stability

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4
Q

What are some examples of what Biodiversity can encompass?

A

Variations:

e.g. in birds:
-body size
-bill size
-bill shape
-diet
-vocalizations

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5
Q

If there is no change in the allele frequency of a population from generation to generation, is evolution occurring?

A

No - we would then be in HW Equilibrium

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6
Q

Can Individuals evolve? Why or why not?

A

NO - individuals do not evolve! Evolution is from generation to generation as it changes in GENETIC COMPOSITION.

Individuals DO NOT decide to evolve to “get stronger” or “reproduce more!”

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7
Q

Are humans more evolved than other species?

A

Not exactly - we have all had the same amount of time to evolve since the Earth began as other organisms

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8
Q

If you look at the layers of sediment at the Grand Canyon, why is it that younger fossils are located closer to the top of the sediment layers and older fossils are located lower in the sediment layers?

A

slow, consistent geologic processes

fossils of extinct taxa are in a consistent order in Earth’s strata, with older (dissimilar) species being found in lower as sediment layers accumulate

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9
Q

What is the difference between an extinct species and an extant species?

A

Extinct = species that no longer exists (lost genetic heritage)

Extant = species that have lived until the present day

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10
Q

How does Lamarck’s inheritance of acquired characteristics differ from Darwin’s proposal of natural selection?

A

Lamarck: “Individuals match their environment”
-traits change due to USE and DISUSE
-characteristics acquired during lifetime are PASSED to offspring

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11
Q

You find a section of sedimentary rock in which the strata and some fossils have been exposed. You notice that a clam fossil is in a deeper strata than a fish fossil.

Using relative dating, which fossil is most likely older?

A

Clam - deeper strata = older fossil

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12
Q

What is an example of Lamarck’s “use and disuse” concept? Why is this concept not
supported by scientific inquiry?

A

If a giraffe stretched its neck for leaves, for example, a “nervous fluid” would flow into its neck and make it longer. Its offspring would inherit the longer neck, and continued stretching would make it longer still over several generations

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13
Q

What are some ways Galápagos finches differ? Why do they differ?

A
  1. Beak Shape (match food source, small/big seeds)
  2. Plumage (black is thought of as more mature)
  3. Body Size
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14
Q

Why is it that an individual who dies earlier in life can have higher individual fitness than an individual who lives a long life?

A

Fitness depends on the contribution an individual makes to the gene pool for the next generation relative to the contribution of others

So, if an individual leaves a lot of offspring, it could have a higher fitness even if it died young!

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15
Q

What is an Adaptation?

A

inherited traits that help an individual SURVIVE and REPRODUCE (enhance fitness)

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16
Q

Do individuals acquire an adaptation because of need? What about through individual behavior (e.g. diet choices, activity levels, levels of risk taken)?

A

Not always based on need.

Individuals who inherit traits that increase likelihood of survival and reproduction in a given environment leave MORE offspring than other individuals

e.g., peppered moth based on environment.

e.g., fish in cave with no natural light - evolved to have no eyes (just sockets) as it was not advantageous.

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17
Q

Explain the process of natural selection. What three conditions are required for natural selection to occur?

A

Natural Selection = differential survival and reproduction by individuals possessing differing heritable characteristics

  1. Traits VARY among individuals in a population
  2. Traits are INHERITED by offspring from parents
  3. More offspring produced than the environment can support (i.e., resources become limited) = UNEQUAL ability to survive and reproduce (individuals differ in reproductive output, “fitness”)
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18
Q

What is fitness and how is fitness related to natural selection?

A

Fitness = contribution an individual makes to the gene pool of the next generation relative to the contributions of other individuals

those who acquire traits that are favorable may do better in reproductive output, so fitness increases (e.g., peppered moth)

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19
Q

Overall, the traits of an organism suit the organism’s environment. Why?

When would the traits of an organism not suit its environment?

A

Environmental conditions vary spatially and temporally, so “favorable traits” are “unfavorable” in another location/time
-e.g., the white fur of a polar bear

A change in environment (say no more snow for a polar bear) would make a trait not suitable for its environment

Certain traits in an environment are more advantageous than others, which increase fitness and thus become “favorable” and suited for the environment

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20
Q

Dark moths on a dark background are more likely to survive (and reproduce) than light moths on a dark background. If the background were to change to a light background, what would you expect would happen over multiple generations to the percent of the population that consists of dark moths vs. the percent of the population that consists of light moths? Why?

A

The opposite…

More dark moths would be eaten than light moths, so the differential survival and reproduction of the light moths over time would lead to the accumulation of this trait to the light environment in the population (leading to all light moths, no dark moths)

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21
Q

What is the difference between natural selection and artificial selection? How are these two processes similar?

A

We choose/shape the reproductive output and “fitness” in Artificial Selection…Natural Selection occurs in nature without human input

Similar in respect to:
1) traits are inherited from parents
2) They both result in changes in genetic traits of organisms
3) Both of these changes can occur and take place over many generations.

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22
Q

There is a hypothesis that is widely supported by scientific data that the gray wolf and the domestic dog share the same common ancestor that is now extinct. Based on this hypothesis, is it correct to state that your family dog evolved from a gray wolf? Why
or why not?

A

No - they both share the same common ancestor, but it is incorrect to say that the family dog evolved from the gray wolf - they are only related by the common ancestor

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23
Q

When you select for a trait in artificial selection, what are you doing?

A

non-naturally choosing favorable traits of the organism and shaping their reproductive output to select more for these traits (e.g., smaller body size for dogs)

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24
Q

When selection occurs in natural selection, what is happening?

A

Favorable heritable traits of organisms in the environment are more likely to let them survive and reproduce - passing these to generation and generation which diverges and changes the species over time

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25
Q

What is the smallest unit of evolution?

A

Populations

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26
Q

T/F: Only heritable traits respond to evolution by natural selection.

A

TRUE - characteristics acquired during an individual’s lifetime are NOT heritable

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27
Q

In evolutionary terms, an individual’s fitness is measured by its __________

A

contribution to the gene pool of the next generation (offspring)

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28
Q

What is the difference between a hypothesis and a theory?

A

Hypothesis: proposed explanation made on the basis of limited evidence as a starting point for further investigation

Theory: patterns and evidence consistent with tested hypotheses support a theory

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29
Q

Are phylogenetic trees (phylogenies) hypotheses or theories?

A

Hypotheses

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30
Q

Why is it so important that people understand evolution?

A

It is the unifying theory of all of biology and can help humans solve real-world problems on a biological basis
-e.g., antibiotics, genetic diseases (sickle-cell)

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31
Q

What is a population? How does a population differ from a species?

A

Population = a group of individuals of the same species living in the same area that interbreed and produce fertile offspring

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32
Q

How does understanding evolution help health professionals address human health issues?

A

Evolutionary Medicine is becoming a greater field…helps to understand topics like:

-Lactose Tolerance/Intolerance
-Sickle-cell Anemia
-MRSA
-Human Bidpedalism
-Narrow Birth Canal = constraints on giving birth
-Allergies
-Auto-immune Disorders
-Morning Sickness during Pregnancy

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33
Q

Explain how drug-resistant viruses evolve. Is this a similar process to how antibiotic-resistant bacteria evolve?

A

Yes - it is similar to the process of bacteria resistant to antibiotics

You are advised to take the entire amount of an antibiotic, even if you feel better. This is because by stopping, there may still be bacteria alive, which reproduce and adapt to the effects of the antibiotic.

This means that, when affected again, these bacteria will become resistant to the antibiotics before, allowing for their reproduction and evolution - and a new treatment option will need to be crafted

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34
Q

How is fitness maximized?

A
  1. Don’t die before reproducing
  2. Maximize output of viable and fertile offspring
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35
Q

How does the fossil record provide support for evolution?

A

In the different strata, and different depths, there were fossils of similar-looking “bug” organisms (Bristolia) that varied among each other, and it was found to be 4 separate species

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36
Q

How do homologous structures differ from analogous structures?

A

Homologous = structures similar in SHAPE and FUNCTION
-e.g., humerus in human vs cat

Analogous = structures similar in FUNCTION, but not shape
-wings of birds and butterflies (not same common ancestor)

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37
Q

How does convergent evolution occur?

A

similar characteristics independently evolved in two lineages (often in response to similar environmental or selective pressures)

e.g., Horned Lizards of N. America versus Thorny Devils of Australia…similar dry environment helped to develop and evolve into the special thorns (for collecting water)

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38
Q

How does the field of biogeography help us understand evolution?

A

Biogeographical patterns provide clues about how species, both alive and extinct, are related to each other

39
Q

What does endemic mean? Provide an example of an endemic species

A

Endemic = species are those found in only one region of the world. Their habitat is limited and restricted, and there are no other populations of the same species beyond those limits anywhere else in the world.

e.g. koala, green iguana, kangaroo

40
Q

What is a hypothesis? How does a hypothesis differ from a prediction?

A

A hypothesis is an idea about how something works that can be tested using experiments. A prediction says what will happen in an experiment if the hypothesis is correct

41
Q

What is the difference between microevolution and macroevolution?

A

Microevolution = individuals possess heritable genetic differences on which natural selection acts, resulting in evolution (small changes over short periods of time)
-e.g., peppered moths

Macroevolution = bigger evolutionary changes that result in new species, which can occur through repeated microevolution or major environmental changes (larger changes over longer period of time)
-e.g., non-functional eye of cave-dwelling fish

42
Q

What is the ultimate source of variation in a population?

What are five major ways in
which allele frequencies change over time in a population?

A

Ultimate source of variation = MUTATIONS

  1. Mutations
  2. Non-random Mating
  3. Gene Flow: movement IN and OUT of a population
  4. Genetic Drift: small populations more susceptible to RANDOM/CHANCE events
  5. Natural Selection
43
Q

Can mutations in somatic cells be passed from parent to offspring in animals? What
about mutations that are found in the sperm and/or egg?

A

Only mutation found in sperm and egg (Gametes) can be passed from parent to offspring

44
Q

What does it mean when a population is fixed for a trait?

A

There is no genetic variation in the population…they are all homozygous for one allele (“fixation”)

45
Q

If you were to look at a phylogeny, where would homologous structures typically be
found? What about analogous structures?

A

Homologous structures typically found near the bottom…“evolved ONCE in the common ancestor”

Analogous structures typically found near the top…“evolved multiple times”

46
Q

What is the Hardy-Weinberg Model? When does it occur?

A

describes a non-evolving population
-allele and genotype frequencies remain CONSTANT from generation to generation

47
Q

What are the assumptions for Hardy-Weinberg Equilibrium (HWE)?

Think about why HWE is rare in nature.

A
  1. NO mutations
  2. Random mating (with respect to locus)
  3. NO gene flow (closed population)
  4. Infinitely (or extremely) large population size
  5. NO natural selection

*All are RARELY true in nature!

48
Q

Natural selection causes evolution.

What are four other mechanisms that lead to evolution?

A
  1. Mutation
  2. Non-random Mating
  3. Gene Flow
  4. Genetic Drift
49
Q

In humans, mutation rates are low overall, but close to 200 mutations typically occur per individual human. How does this information indicate a low mutation rate?

A

Humans have LARGE genomes, all individuals are unique

50
Q

What is sexual selection? How does sexual selection differ from natural selection? Similar?

A

Form of natural selection in which individuals with certain inherited traits are MORE LIKELY to obtain mates than others

51
Q

T/F: Mutations are mostly bad, sometimes neutral, and rarely good

A

TRUE

52
Q

List four characteristics of mutations.

A
  1. They are a change in DNA (nucleotide sequence
  2. They are RANDOM
  3. They often occur in non-protein coding regions
  4. Mutation rates tend to be LOW but genomes are often LARGE
53
Q

How can a mutation impact an individual? A population? A species?

A

-harmful alleles may be “masked” in heterozygotes, if recessive, which could be passed on offspring
-can spread quickly in short-lived/asexually reproducing taxa (e.g., viruses, bacteria)

54
Q

How do directional, disruptive and stabilizing selection differ? Provide an example for each type of selection.

A
  1. Directional: selection for a relatively rare phenotype that differs from the mean of the population (“shift mean’
    -e.g., peppered moths
  2. Disruptive: selection against the common, intermediate phenotype and favoring rare, extreme phenotypes (“increase variance”)
    -e.g., Darwin’s finches (small vs large beaks)
  3. Stabilizing: selection against extreme phenotypes, favoring a common, intermediate phenotype (“decrease variance”)
    -e.g., birth weight (too small and too big are not ideal)
55
Q

How does sexual reproduction contribute to variations in a population?

A

Sexual reproduction results in genetic variation, or genetic differences, between parents and offspring.

56
Q

What’s an example of a sexually selected trait that may confer the highest relative
fitness but may shorten the individual’s lifespan? Would this trait be adaptive in this scenario?

A

Examples could include: Trinidadian guppies; Peacocks

In the case of the guppies, the colorful bodies attract mates, but they also attract predators. Likely, with less predators around, this will adapt to show in a greater array; and with more predators around this color may fade to help survival

57
Q

How does intrasexual selection and intersexual selection relate to fitness?

A

Intersexual selection occurs when one sex chooses which members of the opposite sex to mate with, while intrasexual selection occurs when members of the same sex compete for mates (could be competition or a ritual)

*Intersexual selection creates genetic variation, which leads to higher fitness and more fit generations

58
Q

What are examples of sexual dimorphism?

A

Sexual Dimorphism = marked differences between males and females in a population

e.g., deer and antlers; guppies with colored fins

59
Q

What are the mechanisms that preserve genetic diversity in a population or a species?

A
  1. Heterzygote Advantage (e.g., sickle-cell anemia)
  2. Frequency-Dependent Selection: fitness of a phenotype declines when it is too common (e.g., right- and left-mouthed fish)
60
Q

How could a recessive allele that is currently uncommon in a population be useful if the environment changes?

A

“Diploidy” = recessive alleles “hidden” in a large population where they rarely pair up

61
Q

What evolutionary mechanism increases the amount of genetic variation in a population?

A

Mutation

62
Q

Sickle-cell anemia is a disease that is often accompanied by serious health
complications.

Explain sickle-cell anemia using natural selection.

A

SCA affects homozygous individuals, where those who are homozygous dominant will have the disease, which is a deformation of the RBCs, which can clog vessels and lead to the early death of the individual - or low fitness.

This is an example of a heterozygote advantage, for heterozygotes for SCA have some sickled cells, but not enough for the disease. The presence of these also triggers a rapid turnover of RBCs, which kill malaria parasites.

What this leads to is individuals that contain higher fitness compared to those that are homozygous - an important consideration in natural selection

63
Q

In frequency-dependent selection, the frequency of a phenotype varies over time.

Why isn’t one phenotype selected for to the extent that it becomes fixed in the population?

A

This is because the fitness of a phenotype declines when it is too common - which leads to frequent oscillations as it is rare that one phenotype is “always” more successful than the other. When it becomes too common, it is at a disadvantage, and thus fitness declines and keeps from becoming fixed

64
Q

What is a species? What are the different ways in which species are defined?

A

“Kind” or “Appearance”

Often distinguished on the basis of morphology, physiology, biochemistry, behavior, and/or genetic sequence
-e.g., Western vs Eastern Meadowlark (different songs, behaviors prevent interbreeding)

65
Q

Humans are Homo sapiens. Like other species, there is variation in traits in humans.

How do some human traits correspond to the premise of natural selection that
individuals are suited to their environments?

A

A great example could be skin color with the amount of melanin that is produced to prevent the skin from becoming damaged…where darker skin is associated with more melanin and melanocytes because of the adaptation of the amount of sunlight they receive in comparison to those with lighter skin tones

66
Q

Why is there disagreement among scientists as to whether or not a group of individuals represent the same species, or perhaps two, four, or ten species?

A

There are various definitions of species that can make it confusing and cause disagreements in the number of species actually present, depending on how scientists look:

  1. Morphological species concept (they look different)
  2. Ecological species concept (unique environmental niche)
  3. Phylogenetic species concept (monophyletic groups only identified
  4. Biological species concept
67
Q

Different selection pressures can lead to speciation.

Can you think of examples of
particular selection pressures that could result in the split of one species into two or more species?

A

-Geographical Isolation
-Sexual Selection
-Directional/Disruptive Selection

68
Q

Explain the Biological Species Concept

A

“Species are groups of actually or potentially interbreeding natural populations that are reproductively isolated from other such groups”

  1. Produce viable, fertile offspring (at least potentially)
  2. Breeding with other species is prevented (reproductive isolation)
69
Q

According to the Biological Species Concept, is a mule a species?

NOTE: Horse x Donkey = Mule

A

No - two different species bred and produced the mule offspring, which is against what the Concept states

70
Q

What is the main difference between prezygotic and postzygotic reproductive barriers?

A

Prezygotic Barriers = impede mating or fertilization if mating occurs (BEFORE formation of zygote)

Postzygotic Barriers = prevent a hybrid zygote from developing into a viable, fertile adult (AFTER formation of zygote)

71
Q

Explain the eight reproductive barriers that we discussed in class.

A

PREZYGOTIC BARRIERS
1. Habitat Isolation
2. Temporal Isolation (i.e., reproduce, active at different times)
3. Behavioral Isolation (i.e., differences in behavior… songs, dances)
4. Mechanical Isolation (i.e., physical incompatibility between reproductive organs)
5. Gametic Isolation (i.e., gametes come together, but fertilization does not occur)

POSTZYGOTIC BARRIERS
6. Reduced Hybrid Viability (i.e., hybrid does not make it to reproductive age)
7. Reduced Hybrid Fertility (i.e., sterility…like the mule, so can’t reproduce)
8. Hybrid Breakdown (i.e., offspring of hybrid have reduced viability or fertility)

72
Q

Under what conditions would allopatric speciation occur? Provide examples.

A

Allopatric Speciation (MOST COMMON) = geographical isolation through the formation of a physical barrier

e.g., uplift of mountain range splits a population
e.g., new river forms and splits a population
e.g., lowering of water level of a lake produces 2 smaller lakes

73
Q

Under what conditions would sympatric speciation occur? Provide examples.

A

Sympatric Speciation (RARER) = no geographical isolation, requires special conditions

e.g., polyploidy (genome duplication) in plants…grapes, strawberries, citrus
e.g., strong divergent selection

74
Q

What is the main difference between allopatric and sympatric speciation?

A

In allopatric speciation, groups from an ancestral population evolve into separate species due to a period of geographical separation. In sympatric speciation, groups from the same ancestral population evolve into separate species without any geographical separation.

75
Q

Which form of speciation (allopatric or sympatric) is more common?

A

Allopatric Speciation

76
Q

Is polyploidy more common in plants or animals? Can it occur in both?

A

Most common in Plants

Can occur in both, but rarely in animals (frogs, fish, salamanders)

77
Q

How could polyploidy sometimes result in a new species?

A

Polyploidy is where the whole genome of an organism is duplicated

Here, there is a cell division error that leads to the number of chromosomes being doubled.

Through meiosis, tetraploid cells are created (NOT diploid), meaning that these cells give rise to a new species (as they can no longer reproduce with either parent0

This speciation is broken into two types:
1. Autopolyploid Speciation (within a species)
2. Allopolyplod Speciation (between different species)

78
Q

Let’s say you are studying a large forest patch containing a population of rare plants.

Humans remove the entire middle of the forest patch in order to build a large highway.

As a result, two forest patches remain, each containing a smaller population of the rare plant.

What do you predict would happen to the allele frequencies in the rare plant
populations in the two forest patches over time? Why?

A

This is considered Allopatric Speciation

Here, it is more likely that allele frequencies will change as genetic divergence rises, making the organism different in its genetic makeup and heritable traits than before, considering its environment.

This can lead to traits that act as both prezygotic and postzygotic barriers for the plant, which could lead these plants (if the isolation was taken away) to be unable to reproduce with one another due to their newfound differences

79
Q

How could habitat differentiation sometimes result in a new species?

A

Greater habitat differentiation means there are more types of habitats in the same amount of geographical area. If there are more types of habitats, this presents a scenario in which one species could diverge into two species through sympatric speciation.

80
Q

How could sexual selection sometimes result in a new species?

A

parallel change in mate preference and secondary sexual traits within a population leads to prezygotic isolation between populations - and thus a “split” of species into a new one

81
Q

In Lake Victoria cichlid species, the fish species are currently declining in number,
possibly as a result of water pollution and murkiness. Cichlid females choose mates
(males of the same species as the female) based on the color of the male.

How would murky water impact sexual selection, and also impact the number of species in Lake Victoria?

A

With the murky water conditions, it is more likely that “random mating” may occur, where these waters can “hide” the color of the male cichlid that the female is usually choosy with.

This leaves the possibility that cichlid females could mate with male cichlids of another species - or random mating - which can thus lead to a LOSS of species and the creation of hybrid offspring.

82
Q

Why is sexual selection considered to be nonrandom mating?

A

It is not a random process - not every individual is chosen as a mate, it is a selective process (e.g., cryptic bird not getting its mate on Planet Earth video)

83
Q

Due to less snowfall over the last few winters in the Ozarks, white mice were predated upon more than intermediate- or dark-colored mice.

What kind of selection is acting on the mouse population?

A

Directional Selection

84
Q

A population of fruit flies was starved for 20hrs until 80% of the flies died. The remaining flies were fed and offspring were produced.

What do you expect to see in the next generation if you repeat the starvation experiment with the offspring?

A

More flies will be alive after 20hrs

85
Q

After 60 generations, the average starvation resistance of fruit flies was 160 hours (originally 20hrs)!

What has happened to this population of fruit flies?

A

They are genetically DIFFERENT from the original population

86
Q

The conversion of praise habitat into farmland indiscriminately reduced the population size of greater prairie chicken from millions to ~50 in just a few generations and reduced their genetic diversity.

What event is the likely cause of this change in allele frequency?

A

Bottleneck event

87
Q

Sea urchins are broadcast spawners - they release their gametes into the water without courtship.

What reproductive isolation mechanism is most likely maintaining sea urchin species?

A

Gametic Isolation

Temporal Isolation

88
Q

What primary reproductive isolation mechanism is most likely the cause for sympatric speciation in North American apple maggot flies?

A

Habitat Differentiation

89
Q

Where is energy flow the greatest?

A

From Sun to Primary Producers

90
Q

In most ecosystems, which trophic level has the greatest biomass?

A

Primary Producers

91
Q

In Generation 1 of a study, the allele frequency of A1 is 0.35 and the allele frequency of A2 is 0.65.

In Generation 2 the allele frequency of A1 is 0.40 and the allele frequency of
A2 is 0.60.

Is evolution occurring?

A

Yes - there is a change in allele frequencies between the generations, so we are not in HW Equilibrium!

92
Q

Have most species that exist been identified?

A

No - only about 1.8M species have been formally described and named

There are current estimates that there are about 5 - 100M species that exist

93
Q

How are healthy ecosystems important for human health?

A

Provide Services:
-flood control
-pest control
-air and water purification
-waste decomposition
-crop pollination
-shade and UV protection

94
Q

What are patterns in species extinction rates during the past several hundred years?

A

Most recent extinctions are the result of human actions, and these rates have been increasing

BIO-203: Ecology, Evolution, and Diversity (3 decks)

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