Exam I Answers

Introduction to Biological Anthropology

Appalachian State University, Fall 2006

This exam is worth 25% of your final grade for this class. There are a total of 100 possible points. You will have about 70 minutes to complete the exam. Please take the time to answer the essay portion fully and completely as possible, given the time allowed. Include as much information as you think relates to the question. A simple question does not have a simple “yes” or “no” answer but is an opportunity for you to show off what you have learned.

Multiple Choice (2 points each)

1. The four forces of evolution are

a.) mutation, natural selection, sexual selection, and speciation

b.) mutation, directional selection, speciation, and genetic drift

c.) mutation, natural selection, gene flow, and genetic drift

d.) mutation, geographic isolation, speciation, and genetic drift

2.) In meiosis

a.) the DNA replicates once before each division

b.) somatic cells are produced, with a diploid complement of chromosomes

c.) cell division occurs once and four haploid daughter cells are produced

d.) after two divisions, you end up with four sperm in males and 1 egg in females

3.) Human variation that occurs within a continuous gradation from one region to another is called a:

a.) grade

b.) cline

c.) race

d.) subspecies

4.) Stabilizing Natural Selection requires a _________________ environment and acts ________________ individuals who deviate from the norm.

a.) constant, against

b.) constant, in favor of

c.) changing, against

d.) changing, in favor of

5.) Genetic drift

a.) involves the action of strong natural selection

b.) works best in large populations with lots of genetic variation

c.) involves chance fluctuations in a populations gene frequencies

d.) involves change over a long period of time in a large population

Matching (1 point each)

Circle the Correct Answer (1 point each)

1.) Phenotypic traits produced by  recessive / dominant  alleles may disappear for one generation only to reappear later.

2.) Gametes have the  diploid / haploid  number of chromosomes.

3.) Allopatric / sympatric  speciation begins with the geographic isolation of at least one population from the larger parent species.

4.) Catastrophism / Uniformitarianism  is the idea that the appearance of new forms can be explained by a series of disasters.

Definitions and Contrasts (3 points each)

Write a succinct definition for each of these terms (1 or 2 sentences). When two terms are provided explain the difference between the two concepts (in 2-4 sentences).

1.) Binomial nomenclature

A 2 word naming system that was part of Linnaeus' classification system (taxonomy). It is a formal way of naming of describing an organism that consists of the genus and species name. The genus should be capitalized, species should not be capitalized. They should be typed in italics. An example is Homo sapiens as a description of humans. The genus name can also be abbreviated as the first letter only e.g. H. sapiens.

2.) Biological Species Concept

A species is defined by this concept as: interbreeding natural populations that are reproductively isolated from other such groups. The terms "naturally interbreeding" are used because sometimes members of different species could interbreed but they are isolated from one another in time or geographical space and thus do not naturally do so. Reproductive isolation can refer to geography, time, anatomical, genetic, and behavioral barriers. This is one of many species concepts and it is commonly used although it has limitations in that it is difficult to define fossil species using this concept. 

3.) Grades versus clades and

4.) Cladogenesis and Anagenesis

Two different styles of understanding phylogeny and of thinking about evolution. Grades are analogous to evolutionary change along a linear, slow anagenetic progression, similar to the way that Darwin conceived of evolution. If grades are used to understand phylogenetic relationships, then both primitive and derived traits are used to construct the trees. Clades are a branching form of evolution, in which species form from one ancestral population into two new sister taxa. The branching events are measured in the fossil record only by derived traits. This philosophy is analogous to the theory of punctuated equilibrium, whereby macroevolution procedes in fits and starts with long periods of stasis punctuated by rapid change. 

5.) Inter- and Intra-sexual Selection

Intra-sexual selection is when members of the same sex compete for mates. One example of this process would be male-male competition through displays or actual fighting. Inter-sexual selection is the competition between members of the opposite sex for mates. One example of inter-sexual selection is female choice, when females select males based on their evaluation of his evolutionary fitness using their own objective and subjective criteria. Female choice can be more powerful than male-male competition when females choose not to mate with males that have won contests, effectively wasting the energy that male expended. Sometimes females choose traits that have natural selection value, and sometimes not.

6.) Ring species

Ring species is a term that describes a process whereby a species is widespread geographically and some segments of the species (populations) are geographically isolated from one another. The populations that are farthest from one another undergo a period of isolation that allows for enough change in gene frequencies to accumulate that even if they eventually meet up again, they can no longer interbreed with one another. An example would be Herring gulls. Populations of gulls live in a geographical ring around the arctic circle. Adjacent populations can interbreed however the Herring gull of England the Lesser Black-backed gull of northern Russia cannot interbreed despite geographic proximity. The gene flow between populations has only proceeded in one direction. Ring species represent a difficulty to those who would like to imagine that species are discrete entities.

7.) Recombination versus outcrossing

Outcrossing (also known as sex) is one way that genetic variation is maintained within a species- through novel combinations of maternal and paternal DNA creating genetically unique offspring. Recombination (also known as crossing over) is a form of genetic shuffling that recombines segments of maternal and paternal chromosomes during the production of gametes (meiosis).

Fun with Genetics (18 points)

In humans, brown eyes (B) are dominant over blue (b). A brown-eyed man marries a blue-eyed woman and they have three children, two of whom are brown-eyed and one of whom is blue-eyed. Draw the Punnett square that illustrates this marriage. What is the man’s genotype? What are the genotypes of the children?

If Blue is recessive, what is mom’s genotype? ________bb________________________

If that’s her genotype, what kinds of gametes can she produce? ____________b and b_______________

If Brown is dominant, but they have a blue eyed child, what is dad’s genotype? ____Bb__________

If that’s dad’s genotype, what kind of gametes can he produce? _______B and b____________________

____50____% are heterozygous brown eyed and ____50____% are __homozygous blue eyed___________________

Females have two X chromosomes, which can be represented by XX. Males have one X and one Y chromosome, so we say they are XY. Say these parents have one blue-eyed boy and two brown-eyed children, one girl and one boy. Now what if these parents decided to have a bunch more children, 16 total, how many of those 16 would you expect to be blue-eyed girls?

Dad’s genotype was: _Bb_________ and he is XY. What kinds of gametes can he produce?

Mom is XX and ______bb______ for eye color. What kind of gametes can she produce?

When they mate, their offspring look like this:

x4

_______1/4_________ will be blue eyed girls.

Short Essay Questions (10 points each, 30 points total)

Your answer should be a short essay (at least 1-2 paragraphs of 4-5 sentences each). Be sure to define terms, explain concepts, and give relevant examples to illustrate your understanding of the readings and lectures. Choose 3 of the 5 questions below and write your answer on the back of this page and on the paper provided.

1. Describe the scientific method. Provide details about the process that scientists go through to understand the natural world from observation to dissemination (publication).

2. List the nine misconceptions of evolution discussed in class and give an example for each one (this one is a list, not a paragraph).

3. In his experiments with the garden pea, Mendel discovered the laws of heredity. What are Mendel’s two laws of heredity and how do they work? Draw diagrams to illustrate.

4. Explain the term heterozygote advantage. How does it work to preserve harmful recessive alleles? Give one example from the readings/lecture and explain.

5. Define the concepts of stabilizing and directional selection. What are some examples of reproductive barriers and how can niche partitioning accomplish macroevolution?