Lecture 18. A

Question 1

what is evolution

Answer 1

Evolution can be viewed on a small scale (microevolution) as it relates to changes in one or a few genes in a population over time, or it can be viewed on a larger scale (macroevolution) as it relates to the formation of new species or groups of related species

Question 2

what did Lamarck propose

Answer 2

Lamarck proposed that changes in the environment caused changes in the appearance and behavior in organisms ie that organisms evolve over time in response to the environment.

Question 3

where is Lamarck thought to mess up?

Answer 3

thinking that the parents could pass on acquired traits ie phenotypes.
So, for example, he might have hypothesized that giraffes evolved to have long necks because the first giraffes stretched their necks, and these stretched necks were then passed onto the offspring of these parents.

Question 4

Natural selection ?

Answer 4

process in which individuals with favorable inherited traits are more likely to survive and reproduce.

Question 5

Four observations of darwin?

Answer 5

1. Darwin noticed that even within one species, there was great (phenotypic) diversity
2. Organisms produce more offspring than can survive to reproductive age. Most offspring that are produced die before they reach sexual maturity.
3. There is a struggle to survive due to predation, disease, and competition for limited resources.
4. Organisms with the most favorable traits are most likely to survive to reproductive age, reproduce, and so pass their traits (genes) on to the next generation.

Question 6

Natural selection can be expressed as the following general law :

Answer 6

1. IF there are organisms that reproduce, and
2. IF offspring inherit traits from their progenitor(s), and
3. IF there is variability of traits, and
4. IF the environment cannot support all members of a growing population,
5. THEN those members of the population with less-adaptive traits (determined by the environment) will die out*, &
6. THEN those members with more-adaptive traits (determined by the environment) will thrive.

Question 7

why organisms of same specie look different

Answer 7

because of genetic diversity.

Question 8

what happens if there is no genetic diversity?

Answer 8

if there isn’t any genetic diversity for a particular phenotype, then no selection, no evolution can occur for that phenotype. If all dogs are brown, you can’t select for black fur.

Question 9

on the observation of what did Darwin based his theory of evolution?

Answer 9

mainly on observations he made on birds called finches. He noticed the great variety of finches and how their beaks varied depending on the type of food the birds ate. In the figure on the right, the center of the circle represents what is thought to be the common ancestor to all the finches. The idea is that depending on what food was available (the finches live on different islands), the beaks of the birds would be selected to become adapted to their food
–> natural selection

Question 10

Natural selection includes?

Answer 10

• selective biotic and abiotic pressures like temperature, amount of sun, amount of nutrients, predators, prey populations and
• selective sexual selection. Both the structures and behaviors of sexually reproducing organisms are important. Think of a male bird that sings well; he’ll attract more females, and will be more successful, reproductively. Same thing for plants that have flowers that make a certain odor that is good at attracting pollinators

Question 11

Organisms that are adapted to their environment are able to:

Answer 11

• obtain needed gases, water, food and nutrients
• cope with physical conditions such as temperature, light and heat
• defend themselves from their natural enemies
• reproduce
• respond to changes around them.

Question 12

adaptations?

Answer 12

Inherited characteristics that increase survival & reproductive success in specific environments are called adaptations.

Question 13

Adaptations can be __ , __ , or __ .

Answer 13

morphological, physiological, or behavioral.

Question 14

who proposed the “single common ancestor”?

Answer 14

Darwin proposed that all organisms currently alive or extinct, evolved from a single common ancestor.

Question 15

why is Darwin wrong about the single common ancestor?

Answer 15

Darwin’s tree is likely at least partly incorrect in that there is likely more than one ancestor and horizontal as well as vertical gene transfer occurs

Question 16

Descent with modification?

Answer 16

Darwin proposed that the diversity of organisms originates from a common ancestor with different modifications made through time

Question 17

epigenetics ?

Answer 17

the study of changes in organisms caused by modification of gene expression rather than alteration of the genetic code itself.
. Epigenetics is the study of heritable changes in gene expression (active versus inactive genes) that do not involve changes to the underlying DNA sequence — a change in phenotype without a change in genotype — which in turn affects how cells read the genes. These changes can (but don’t necessarily) get passed down from one generation to the next.

Question 18

Mutation

Answer 18

a permanent change in a DNA sequence

Mutations can result from DNA copying mistakes made during S phase

Question 19

Gene flow

Answer 19

: transfer of alleles between populations; usually this refers to exchange of alleles between members of the same species (ex grizzly bears in BC and in Alaska), through sexual reproduction, but gene flow (horizontal gene flow) can also occur between different species.

Question 20

Genetic drift

Answer 20

microevolution that occurs due to chance or an unexpected/unpredictable event; Said another way it is a change in a population’s allele frequencies caused by chance instead of selection. Genetic drift usually happens when there is a reduction in the population size.

Question 21

Stabilizing selection

Answer 21

selection where the intermediate phenotype is favored over the extremes; this selection is most common & results in the elimination of extreme phenotypes within a population

Question 22

Directional selection

Answer 22

selection where a previously stable population begins to favor one extreme phenotype over another; the population distribution curve will shift in the direction of the extreme phenotype.

Question 23

Disruptive selection

Answer 23

selection where the intermediate phenotype is unfavored and both extreme phenotypes are favored

Question 24

hybrid zone

Answer 24

region in which members of different species mate and produce hybrids. Hybrids result from mating between species with incomplete reproductive barriers

Question 25

Lamark hypothesized that

Answer 25

organisms undergo change as a result of natural phenomenon.

characteristics acquired during the lifetime of an animal were transmitted, to its offspring.

Question 26

Natural selection acts on?

Answer 26

an organism’s phenotype

Question 27

The Darwinian Theory of Evolution states

Answer 27

those individuals which are most fit for an environment will be the ones most likely to survive.

those individuals which are most fit for an environment will demonstrate differential reproductive success

individuals of species vary.

Question 28

Darwin’s theory of natural selection states that:

Answer 28

the best adapted individuals will generally produce the greatest number of offspring

Question 29

gene flow vs genetic drift

Answer 29

Gene flow is the process of alleles going from one population to another while genetic drift is the alteration of allele frequency in a gene pool.

Question 30

While mutations can be __________ to an organism, they are usually _______ in effect.

Answer 30

beneficial, harmful

Question 31

What is an adaptation, and how do adaptations become more common within a population?

Answer 31

An adaptation is a characteristic that helps an individual survive and reproduce in its environment. Adaptations become more common within a population when they are heritable and when they increase the odds of survival and reproduction.

Question 32

What is the role of genetic variation in natural selection?

Answer 32

Genetic variation is what natural selection acts on since genetic variation creates variations in phenotypes, some of which are better suited to the current environment.

Question 33

How can natural selection favor different phenotypes at different times?

Answer 33

Natural selection can favor different phenotypes at different times if the environments change in subtle or dramatic ways.

Question 34

Why doesn’t natural selection produce perfectly adapted organisms?

Answer 34

Natural selection does not produce perfectly adapted organisms because each population’s evolution is constrained by its existing gene pool, which limits the possible allele combinations and may not contain every allele necessary to confront every challenge. Chance events may also wipe out adaptive allele combinations. Genetic illnesses that produce symptoms only after reproductive age also can maintain harmful alleles in a population.

Question 35

How can natural selection maintain harmful alleles in a population?

Answer 35

Natural selection can only select against phenotypes. If the dominant phenotype is selected for, heterozygous individuals will retain the recessive allele in the population. Also there are times when the heterozygous condition gives advantages to the individual

Question 36

how does variation arise in an asexually reproducing population? A sexually reproducing population?

Answer 36

variation arises in all species through mutations. In sexually reproducing species, variation spreads rapidly as a result of genetic recombination during meiosis. Hybridization and horizontal gene transfer are other important sources.

Question 37

Under what conditions does a mutation in one organism pass to subsequent generations?

Answer 37

a mutation in one organism passes to subsequent generations if it is a mutation that can be inherited. In sexually reproducing organisms, the mutation must appear in a gamete-producing cell. Mutations in somatic cells will not be passed to the next generation. In contrast, a mutation in an organism that produces asexually will be transmitted to all of the offspring.

Question 38

Many articles about the rise of antibiotic-resistant bacteria claim that overuse of antibiotics creates resistant strains. How is this incorrect?

Answer 38

Within populations of bacteria, random mutations are constantly occurring. Exposure to antibiotics does not cause such mutations, but it does cause the death of the bacteria that do not inherit alleles that confer resistance, and in this way selects for those cells that are already resistant to that antibiotic.

Question 39

how is evolutionary fitness measured?

Answer 39

reproductive success: how many offspring an individual has.