Origin of Life (1)

Question 1

What did darwin call his theory and explain its two statements?

Answer 1

Theory descent with modification, which explains that:

1. All of life is connected by common ancestry.
2. Descendants have accumulated adaptations to changing environments over vast spans of time.

Question 2

What is natural selection?

Answer 2

Natural selection is the idea that organisms with certain traits are more likely to survive and reproduce than others without those traits

Question 3

What are the 3 key points about evolution by natural selection?

Answer 3

1. Although natural selection occurs through interactions between individual organisms and the environment, individuals do not evolve. Rather, it is the population, the group of organisms, that evolves over time.
2. Natural selection can amplify or diminish only heritable traits.
3. Evolution is not goal-directed; it does not lead to perfectly adapted organisms.

Question 4

What are some unique things about Galapagos island?

Answer 4

1. Most species here are not found anywhere else in the world, but they do resemble some South American species
2. No natural predators on the island

Question 5

How would Darwin observe the species on the island? Whose concept did apply to species?

Answer 5

1. Darwin would compare fossil records to present living species and detail the traits of different animals to relate them to the environment.
2. Charles Lyell, postulated that an ancient Earth was sculpted over millions of years by gradual geological processes

Darwin applied the same concept to organisms

Question 6

What are fossils and what is their significance?

Answer 6

Fossils are the imprints or remains of organisms that lived in the past.

-document differences between past and present organisms

-reveal that many species have become extinct.

-The fossil record reveals the historical sequence in which organisms have evolved.

Question 7

Some fossils aren’t fossils. Explain.

Answer 7

Ammonite shells are casts of the dead organism captured in sedimentary rock that remain after decomposition.

Question 8

Why are fossils not a complete record?

Answer 8

Many organisms did not live in areas that favored fossilization.

Fossils usually require areas that favor sedimentary rock formation.

Question 9

How did paleontologists postulate that whales had legs?

Answer 9

Based on their pelvic bones,paleontologists hypothesized that the answers of whales were hoofed, wolf-like carnivores.

Question 10

What did molecular biologists say about whale evolution?

Answer 10

While paleontologists found Pakicetus to support their theory of whale evolution, molecular biologists found a close relationship between whales and hippopotamuses and hypothesized that whales and hippos were both descendants of a cloven-hoofed ancestor.

Question 11

What are homologous structures?

Answer 11

1. Homologous structures are similar in structure but often different in function.
2. Organism with a common ancestor that diverged

Question 12

What’s an example of homology?

Answer 12

Vestigial structures are remnants of features that served important functions in the organism’s ancestors.

Question 13

How did Darwin test his theory?

Answer 13

Darwin reasoned that if artificial selection can bring about so much change in a relatively short period of time, then natural selection could modify species considerably over hundreds or thousands of generations.

Question 14

What does evolutionary adaptation tell us about natural selection?

Answer 14

1. Natural selection is more of an editing process than a creative mechanism.
2. Natural selection is contingent on time and place, favoring those heritable traits in a varying population that fit the current, local environment.

Question 15

_______are the ultimate source of the genetic variation that serves as raw material for evolution.

Answer 15

Mutation.

Question 16

Fresh assortments of existing alleles arise every generation from three random components of sexual reproduction. Which are they?

Answer 16

1. Crossing over
2. Independent orientation of homologous chromosomes at metaphase I of meiosis
3. Random fertilization

Question 17

What is gene pool?

Answer 17

A gene pool consists of all copies of every type of allele, at every locus, in all members of the population.

Question 18

What is microevolution?

Answer 18

Microevolution is a change in the frequencies of alleles in a population’s gene pool and evolution occurring on its smallest scale.

Question 19

What are the causes of evolutionary change?

Answer 19

1. Genetic drift
2. Gene flow
3. Natural selection

Question 20

What is genetic drift and how is it caused?

Answer 20

Genetic drift is the change in frequency of an existing gene variant in the population due to random chance.

1. Bottleneck effect: happens when the size of a population is severely reduced due to natural disasters leaving behind few survivors.
2. Founder effect: when a few individuals colonize a new habitat.

Question 21

What is gene flow and what does it do?

Answer 21

Gene flow refers to when a population gains or loses alleles when fertile individuals move into or out of a population, or when gametes are transferred between populations

Gene flow tends to reduce differences between populations.

Question 22

How does natural selection lead to evolutionary change?

Answer 22

Relative fitness is the contribution an individual makes to the gene pool of the next generation relative to the contributions of other individuals.

As a result of natural selection, favorable traits increase in a population.

Question 23

What are the types of natural selection?

Answer 23

1. Stabilizing selection: favors intermediate phenotypes.
2. Directional selection: shifts the overall makeup of the population by acting against individuals at one of the phenotypic extremes.
3. Disruptive selection typically occurs when environmental conditions vary in a way that favors individuals at both ends of a phenotypic range over individuals with intermediate phenotypes.

Question 24

What is sexual selection?

Answer 24

Sexual selection is a form of natural selection in which individuals with certain characteristics are more likely than other individuals to obtain mates.

Question 25

Differentiate between intersexual and intrasexual selection.

Answer 25

Intrasexual selection: Individuals compete directly with members of the same sex for mates.

In intersexual selection or mate choice, individuals of one sex are choosy in selecting their mates.

Question 26

How do humans contribute to the problem of antibiotic resistance?

Answer 26

1. Doctors overprescribe antibiotics,
2. Patients prematurely stop taking antibiotics.
3. Livestock producers add antibiotics to animal feed as a growth promoter and to prevent illness

Question 27

How does diploidy preserve genetic variation?

Answer 27

Diploidy preserves variation by “hiding” recessive alleles.

1. Balancing/ stabilizing selection
2. Heterozygote advantage

Question 28

What is heterozygote advantage?

Answer 28

Heterozygote advantage is a type of balancing selection in which heterozygous individuals have greater reproductive success than either type of homozygote, with the result that two or more alleles for a gene are maintained in the population.

Question 29

Natural selection does not make perfect organisms and is constrained. Explain.

Answer 29

1. Selection can act only on existing variations. ​
2. Evolution is limited by historical constraints.

​3. Adaptations are often compromises. The same structure often performs many functions.
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4. Chance, natural selection, and the environment interact. Environments often change unpredictably.