Unit 8: Evolution

Question 1

What is evolution?

Answer 1

Evolution is the genetic change of a population overtime. It’s the process by which modern organisms have descended from ancient, common ancestors. It’s the explanation for biodiversity on Earth.

Question 2

What did Darwin observe about the species on the Galapagos Islands? What did he conclude based on these observations?

Answer 2

Darwin observed that the Galapagos Islands are close and they have similar climates, but they have different vegetation. He observed that the variations among island species seemed well suited to animals diets and environments. They weren’t created in their present form, but evolved from a common ancestor to better survive their environment.

Question 3

How are genetic diversity, allele frequencies, and genetic equilibrium related to evolution?

Answer 3

Evolution changes populations over generations of time. It changes the allele frequency of the population, along with the phenotypes of the organisms. This creates genetic diversity; evolution affects different species living in separate environments uniquely. When a population stops evolving, they have reached genetic equilibrium.

Question 4

What is the main mechanism that drives evolution?

Answer 4

Natural selection.

Question 5

What is natural selection? Who/ what is the selective agent?

Answer 5

Natural selection states that individuals that have physical or behavioral traits that better suit their environment are more likely to survive and will reproduce more successfully than those that don’t have such traits. The selective agent is nature.

Question 6

What are the 4 principles of natural selection? Define each in your own words.

Answer 6

The 4 main principles of natural selection are: overproduction, adaptation, and descent with modification. Variation meaning the population has heritable traits. Overproduction is when more offspring are produced so that when some are killed off, the rest have a chance to carry on their genes. Adaptation is the process in which variations allow individuals to survive better than others. Descent with modification: each new generation of species inherits adaptations that are well suited for survival and reproduction in its environment.

Question 7

What does natural selection act on directly? Indirectly?

Answer 7

Natural selection acts directly on a population’s phenotype. It acts indirectly on their genotype.

Question 8

What kind of traits are “selected” for by natural selection?

Answer 8

Physical and behavioral traits that best suit the population’s environment are selected by natural selection.

Question 9

How long does it take for organisms to develop adaptations that are well suited for their environment?

Answer 9

It takes millions of years.

Question 10

How do fossils provide evidence for evolution?

Answer 10

Fossils show the changes of a population over time. Transitional fossils are species that are in the middle of two different animal groups. They are important to evolution because they are the missing links between ancestral and modern-day organisms.

Question 11

Where are most primitive fossils found?

Answer 11

They are mostly found in lower layers of the Earth.

Question 12

Explain how embryology provides evidence for evolution.

Answer 12

Since all the embryos of organisms look extremely similar and have almost the same exact structures as each other, it means that they would have had to come from a common origin.

Question 13

What is a homologous structure and why is it important when studying evolution? Give an example of a homologous structure.

Answer 13

Homologous structures are similar structures, but in different organisms and have different functions. Since all organisms now are separated into different species, but they have the same bone structures, it supports Darwin’s theory of evolution. Ex: penguin and bird wings.

Question 14

Explain the term vestigial structure. Give an example.

Answer 14

They are remnants of organs/structures that used to have a function in an early ancestor. They have either reduced in size or use. Ex: human appendix and wisdom teeth.

Question 15

Which type of structure cannot be used as evidence of a common ancestor/descent?

Answer 15

Analogous structures.

Question 16

Define and give yourself an example for each of the following terms: Gene pool, adaptation, species, population.

Answer 16

A gene pool is the total collection of genes in a population at any one time. Adaptations are when variations allow individuals to survive the best. Organisms that reproduce and belong to the same species interbreed and produce fertile offspring. A population is a group of in interbreeding individuals that live in the same place at the same time.

Question 17

Explain what makes a species less likely to go extinct.

Answer 17

Genetic diversity. It increases likelihood that some individuals will be able to survive environmental change.

Question 18

Define and explain how each the following terms affect genetic diversity: founder effect, gene flow, mutation, bottleneck effect, sexual selection.

Answer 18

The founder effect results from the colonization of a new location by a small number of individuals. It reduces genetic variation. Gene flow is the movement of alleles into or out of a population. It increases the genetic variation of the receiving population. Mutations are alterations of genetic material that occur randomly. It increases genetic variation by producing new traits. The bottleneck effect drastically reduces genetic variation of the surviving population from a big disaster. Sexual selection occurs when certain traits increase mating success.

Question 19

Define speciation then explain how reproductive isolation is important for speciation.

Answer 19

Speciation is the evolution of one species into two or more new species. Reproductive isolation is when genes become different in a population. It establishes that there are now two different species.

Question 20

List the 3 types of isolation that can lead to speciation. Give an example of each.

Answer 20

Geographic isolation is when a physical barrier separates a population. Ex: rivers, canyons, mountains, volcanoes. Behavioral isolation is when differences in courtship and mating behaviors. Ex: blue-footed booby and the robin. Temporal isolation is when reproductive periods happen at different times, preventing mating. Ex: american and fowler’s toad.

Question 21

List the 3 types of evolution and give an example of each.

Answer 21

Coevolution is when two or more species evolve together in response to changes in each other. Convergent evolution is when species from different evolutionary lines evolve similar traits due to similar environments. Divergent evolution is when similar species diverge and become increasingly different in order to adapt to a new environment.

Question 22

Compare allopatric and sympatric speciation.

Answer 22

Allopatric speciation is when a population is separated geographically, restricting the gene flow between the subpopulations. Sympatric speciation is when a new species forms, but in the same geographic location within the population. There is no physical barrier to gene flow. They both build up genetic differences; they become reproductively isolated.

Question 23

Where does variation among the individuals that make up a population come from?

Answer 23

Gene flow, genetic drift (bottleneck and founder effects), natural selection (stabilizing, directional, and disruptive), sexual selection (intrasexual and intersexual), and mutations.

Question 24

Explain how postzygotic mechanisms are involved in speciation.

Answer 24

Reduced hybrid viability can cause some hybrids to fail maturity or die during development. Reduced hybrid fertility means hybrids cannot produce its own offspring. These complications ensure that hybrids are separated from other species.