Chapter 10: Evolution

Question 1

Evolution

Answer 1

The change in allelic frequencies within a population.

Question 2

Methods to Date the Earth’s History

Answer 2

• Radiometric dating.
• Paleomagnetic dating.
• Studying fossils and sedimentary rock layers.

Question 3

Cambrian Explosion

Answer 3

The sudden appearance of many present-day phyla.

Question 4

Evidence for Evolution

Answer 4

1. Fossil Record: Using radioactive dating and half lives, we can wee how old a fossil is. This is evidence that many of the species once on earth already went extinct.
2. Comparative Anatomy: we can compare similar structures between species to determine if they are evolutionary related or not.
3. Comparative Biochemistry: Evolutionarily related species will exhibit the same or very similar biochemical pathways.
4. Comparative Embryology: Evolutionary related species will exhibit the same or similar embryonic development.
5. Molecular Biology: Comparison of the cytochrome c. sequence (all organisms have this). Similar organisms will have similar or identical sequences.
6. Biogeography: the continental drift change the Earth’s flora and fauna. This often changes the distribution of life on Earth.

Question 5

Analogous Structures

Answer 5

Same structure on two species that results due to a similarity in selection press, and is an evidence of evolution.

Question 6

Homologous Structures

Answer 6

Same structure on two species that results due to a common ancestor between the two.

Question 7

Vestigial Structures

Answer 7

A structure that is no longer necessary and plays no useful role in the functioning of the organism, and thus is evidence of evolution.

Question 8

Linneaus

Answer 8

Specialized in taxonomy, and created the binomial naming system.

Question 9

Cuvier

Answer 9

Stated that each time period had characteristic fossils, which were caused by a series of catastrophes.

Question 10

Hutton

Answer 10

Proposed the idea of gradualism: Earth changes over time, gradually.

Question 11

Lamarck

Answer 11

Proposed a wrong theory of evolution. Stated that individuals could inherit acquired characteristics from their ancestors through use and disuse.

Question 12

Wallace

Answer 12

Came up with the same theory of natural selection as Darwin.

Question 13

Charles Darwin

Answer 13

On his trip to the Galapagos Islands, Darwin created his theory of natural selection and the descent with modification. Published his book “On the Origin of Species.”

Question 14

Darwin’s Theory of Natural Selection

Answer 14

1. Populations tend to overgrow.
2. This overpopulation leads to competition for resources.
3. Some individuals are more “fit” to reproduce and pass on its genes than others.
4. Only the most “fit” live on to survive and reproduce.
5. This leaves an increasingly advantageous population.

Question 15

Selective Advantage

Answer 15

An advantage certain individuals have against their environment’s selection pressures.

Question 16

Stabilizing Selection

Answer 16

Eliminates the extremes and favors the middle ground organisms. An example includes baby weight – middle weight babies are more likely to survive than very light or heavy babies.

Question 17

Disruptive Selection

Answer 17

Favors the two extremes of a population. Might result in balanced polymorphism, or the creation of two distinct species. An example includes light and dark mice in light and dark rocks.

Question 18

Balanced Polymorphism

Answer 18

When a species is separated into two types.

Question 19

Directional Selection

Answer 19

Favors only one extreme in a population. An example includes dark and light moths in England. At first, light moths had the advantage. However, when England was covered in soot and smoke, the dark moths the received the advantage.

Question 20

Sexual Selection

Answer 20

Selection in competing or attracting mates.

Question 21

Sexual Dimorphism

Answer 21

Differences in appearance between males and females.

Question 22

Artificial Selection

Answer 22

Humans tamper with normal mating by purposely breeding two organisms to get favorable traits.

Question 23

Methods to Preserving Variation in a Population

Answer 23

1. Balanced Polymorphism: Presence of two or more phenotypically distinct forms of a trait (dark mice and light mice).
2. Geographic isolation: difference in phenotype due to different selection pressures in a species.
3. Sexual Reproduction: Variation due to the shuffling and recombination of parts of chromosomes (independent assortment, crossing over, random mating).
4. Outbreeding: mating of organisms with someone not closely related to get a wide gene pool (opposite of inbreeding).
5. Diploidy: maintains and hides a huge pool of alleles.
6. Heterozygote Advantage: sometimes the hybrid will have selective advantage over the homozygous individuals, which retains more alleles.
7. Frequency-dependent Selection: Decrease in the frequency of common phenotypes, and increase in the frequency of rarer phenotypes.
8. Evolutionary Neutral Traits: Traits that seem to have no selective advantage over the other (ex: human blood type).

Question 24

Genetic Drift

Answer 24

Change in the gene pool due to chance.

Question 25

Bottleneck effect

Answer 25

Natural disasters greatly reduce the size of the gene pool unselectively, which causes a loss in genetic variation. Some alleles are then over or under represented in this new modified population.

An example includes elephant seals being hunted almost to extinction until the government placed regulations over hunting. When the population grew back, the genetic variation is very small.

Question 26

Founder effect

Answer 26

A small part of the population moves away to a new area, in which the gene pool is probably not representative of the original one.

An example includes a group of Amish people moving to a new area, and one of the members had the rare trait for polydactyly. This resulted in this close community having a high incidence of polydactyly.

Question 27

Gene Flow (Causes of Evolution)

Answer 27

Movement of alleles in and out of a population.

Question 28

Mutations (Causes of Evolution)

Answer 28

Changes in genetic material that leads to an increase in diversity.

Question 29

Nonrandom Mating (Causes of Evolution)

Answer 29

Organisms choose their mate due to the concept of survival of the fittest, which eliminates the less fit individuals.

Question 30

Natural Selection (Causes of Evolution)

Answer 30

Survival of the fittest leads to only the most fit individuals passing their genes onto the next generation.

Question 31

Characteristics of Hardy Weinberg Equilibrium

Answer 31

1. Large populations.
2. No natural selection
3. No immigration
4. Random mating
5. No mutations.

Question 32

Species

Answer 32

A population whose members have the potential to interbreed and produce viable, fertile offspring.

Question 33

Speciation

Answer 33

The diverging of one species into two, due to genetic differences.

Question 34

Allopatric Speciation

Answer 34

Caused by geographic isolation, such as separation due to mountains, canyons, etc. An example is the Grand Canyon squirrels.

Question 35

Sympatric Speciation

Answer 35

Speciation that occurs without geographic isolation. Causes include:

Polyploidy: polyploidy is when a cell has more than two sets of complete chromosome. Polyploid organisms cannot breed with non-polyploid organisms.

Habitat Isolation: Where two organisms live in the same place but rarely encounter each other.

Behavioral Isolation: mistakes and differences in mating rituals will prevent mating.

Temporal isolation: Difference in timing that prevents mating

Reproductive isolation: a variety of reasons. One includes incompatibility of the genitalia.

Question 36

Prezygotic barriers

Answer 36

Barriers that impeded the mating of two organisms.

Question 37

Postzygotic barriers

Answer 37

Barriers after the mating has occurred, which stop the zygote from being developed.

Question 38

Divergent Evolution

Answer 38

When a population becomes separated and faces a new set of selection pressures which evolves into a new species. Allopatric and sympatric speciation are examples.

Question 39

Convergent Evolution

Answer 39

When similar selection pressures result in very similar adaptations. Based on analogous structures.

Question 40

Parallel Evolution

Answer 40

Evolution that occurs from evolving from a common ancestor, then experiencing similar selection pressures that result in similar adaptations.

Question 41

Coevolution

Answer 41

When an adaptation in one species causes an adaptation to a related species. Examples include predator-prey, parasite-host, competitive, and mutualistic species. For example, an evolutionary change in the morphology of a plant might cause a change in the organism that eats that plant.

Question 42

Adaptive Radiation

Answer 42

Emergence of many species from a common ancestor to fill an ecological niche. Examples include the Darwin’s finches on the Galapagos Islands.

Question 43

Gradualism

Answer 43

The theory of evolution that states evolution occurs in a series of small steps and transitional phases.

Question 44

Punctuated Equilibrium

Answer 44

The favored theory of evolution, in which new species emerges suddenly after long periods of stasis.