Evolution

Question 1

Why biologists view Evolution as a theory and a fact?

Answer 1

Many scientists and philosophers of science have described evolution as fact and theory, a phrase which was used as the title of an article by Stephen Jay Gould in 1981. He describes fact in science as meaning data, not absolute certainty but “confirmed to such a degree that it would be perverse to withhold provisional assent.” A scientific theory is a well-substantiated explanation of such facts. The facts of evolution come from observational evidence of current processes, from imperfections in organisms recording historical common descent, and from transitions in the fossil record. Theories of evolution provide a provisional explanation for these facts.

Question 2

Charle Darwin’s major contribution to evolutionary theory

Answer 2

He didn’t invent the concept of Natural Selection but he showed how it operated in nature. He also advanced the general idea that all organisms have descended from the same ancestor.

Question 3

Definition of Evolution

Answer 3

Heritable change in allele frequencies in a population over time

Question 4

What are the four (4) major forces of evolutionary change?

Answer 4

Natural Selection
Mutation
Gene Flow
Genetic Drift

Question 5

Natural Selection

Answer 5

The idea that those organisms that are best adapted to a particular environment are most likely to survive, reproduce & pass down their traits to future generations. (But note that if the environment changes, traits that were once adaptive may no longer be optimal for survival)

Question 6

Mutation

Answer 6

A permanent change in the DNA sequence of a gene

Question 7

Gene Flow

Answer 7

Gene flow is the transfer of the allele or genes from one population to an another

Question 8

Genetic Drift

Answer 8

Genetic drift or allelic drift is the change in the frequency of a gene variant (allele) in a population due to random sampling.

Question 9

Why meiosis plays a significant role in evolution but is not one of the major forces of evolution?

Answer 9

Meiosis is a source of individual generic variation. Without that variation, natural selection cannot take place. However, evolutionary change occurs only if offspring inherit a genetic variation that becomes widespread in a population. `

Question 10

The major genetic principles discovered by Mendel

Answer 10

1. The inheritance of biological characteristics is determined by individual units known as genes. They are passed from parent to offspring.
2. In cases in which two or more alleles of the gene for a single trait exist, some forms of the gene may be dominant or recessive.
3. In most sexually reproducing organisms, each adult has two copies of each gene- one from each parent. These are segregated from each other when gametes are formed.
4. The alleles for different genes usually segregate independently of one another.

Question 11

Difference between Mendelian and non-Mendelian traits

Answer 11

Mendelian inheritance does not take account of recombination or mutation, and with Mendelian inheritance the loci are unlinked.

Question 12

What is the difference between mitochondrial DNA (mtDNA) & nuclear DNA?

Answer 12

Unlike nuclear DNA, whose genes are rearranged in the process of recombination, there is usually no change in mtDNA from parent to offspring. Because of this, and the fact that the mutation rate of mtDNA is higher than that of nuclear DNA and is easily measured, mtDNA is a powerful tool for tracking matrilineage, and has been used in this role for tracking the ancestry of many species back hundreds of generations. Human mtDNA can also be used to identify individuals.

Question 13

Founder’s Effect

Answer 13

The founder’s effect is is the loss of genetic variation that occurs when a new population is established by a very small number of individuals from a larger population. eg. French Canadians

Question 14

Race is not biologically Meaningful because

Answer 14

a) migration, trade, military conquest, colonization, etc have result to gene flow-the interchange of genes between groups b) skin color, hair texture & other traits used to define races are polygenic c) Racial variation is continuous-it doesn’t stop at the borders of nation-states d) Variation may also be discontinuous-found in pockets or small areas of a country.

Question 15

Race in Biology

Answer 15

Is a subspecies that’s evolving toward becoming a separate species eg reindeer and caribou were originally the same species: Rangifer tarandus.

Question 16

Why humans sweat easier than other mammals

Answer 16

Humans are relatively hairless, compared to other land mammals. All mammals produce sweat but humans sweat much more than the other mammals because of the ratio of our 2 types of sweat glands: eccrine and apocrine glands. Humans have more eccrine glands (αδένες), which secreat a watery liquid that cools us as it evaporates. Sweating is also a response to emotional stimuli. Secretions from apocrine glands (in the armpit and genital area) release pheromones that serve as signals to others in a group.

Question 17

Human adaptation to the heat

Answer 17

Various environmental stressors-including heat-may result in permanent changes, not just acclimatization. Long-term genetic adaptation may occur in a population that is regularly exposed to a stressor.

Question 18

Allen’s law

Answer 18

A tall, slim body with long appendages is one type of genetic adaptation.

Question 19

Reproductive isolating mechanisms

Answer 19

Are a collection of mechanisms, behaviors and physiological processes that prevent the members of two different species that cross or mate from producing offspring, or which ensure that any offspring that may be produced is not fertile. These barriers maintain the integrity of a species over time, reducing or directly impeding gene flow between individuals of different species, allowing the conservation of each species’ characteristics