Biology 1408 exam 2 answers

BIOLOGY CONCEPTS AND INVESTIGATIONS. MARIELLE HOEFNAGELS. THIRD EDITION

1. Imagine that you are a scientist working with one of the first research teams sent to the planet Mars. One day, while digging in one of your research plots, you discover something new in the soil. You think it might be alive!

a. How will you determine whether it is alive or not?

b. How will you know whether it is a prokaryote or a eukaryote?

c. How will you determine in which of the three Domains of life it might be classified?

2. Explain how energy enters and travels through most living systems on Earth.

a. What is the original source of the energy?

b. How is energy transferred within living systems? You may answer in written text and/or by drawing and labeling a diagram of a generalized system.

c. Why are there always more primary producers than there are consumers in living systems?

d. Include the following terms in your answer: autotroph, heterotroph, decomposers, primary producers, primary consumers, secondary consumers.

3. Explain why photosynthesis and aerobic respiration are considered to be opposite reactions. Use the following terms in your explanation: exergonic reaction, endergonic reaction, potential energy and kinetic energy.

4. Hypothesis testing and experimental design:

a. State an observation about your environment.

b. List three hypotheses (ideas that you can test) that might explain the mechanism(s) responsible for the phenomenon that you observed.

c. Choose one of those hypotheses to test. State your null hypothesis.

d. Design an experiment or a set of observations that you could perform to test your chosen hypothesis.

i. What would your control group be?

ii. What would your treatment group(s) be?

iii. What variables would you standardize?

iv. What variables would you measure?

e. What would the outcome of your experiment be if your hypothesis is correct?

f. What would the outcome of your experiment be if your hypothesis is incorrect?

5. How can a failed checkpoint during the cell cycle result in cancer? Describe some of the mistakes that can result if a checkpoint fails at each of the following stages of the cell cycle:

a. Gap Phase 1:

b. Synthesis Phase:

c. Gap Phase 2:

d. Metaphase of Mitosis:

6. Why is sexual reproduction so costly? If sexual reproduction is so costly, why do so many organisms have sex?

7. Draw a pair of un-replicated homologous chromosomes.

8. Imagine that you are a herpetologist (i.e., a scientist who studies reptiles) working in West Texas. You specialize in studying checkered whiptail lizard species, some of which reproduce sexually and some of which reproduce asexually. The asexual species are thought to have arisen from a hybridization event between two sexual species. One day you come across what you think is a new species of checkered whiptail lizards. It appears to reproduce asexually, but after some lab work, you discover that it does NOT replicate its DNA twice before undergoing meiosis like some of the other asexual species do. You also observe that the offspring of these asexual lizards still have the same number of chromosomes as their parents. What else could these lizards be doing (besides two rounds of DNA replication prior to meiosis) to reproduce themselves without reducing the number of chromosomes in their offspring?

a. Draw and label a normal sexual reproductive life cycle.

b. Draw and label your hypothesized asexual reproductive life cycle for the newly discovered lizard species.

9. If you have a plant that expresses a dominant trait, how can you determine its genotype?

Tall (L) = Dominant allele Short (l) = Recessive allele

a. What are the possible genotypes for a tall plant?

b. With what genotype/phenotype plant could you cross a “mystery” tall plant to determine its genotype?

c. Draw the punnette square for the possible crosses?

d. What phenotypic ratios would you expect in the offspring if the "mystery" plant were homozygous dominant?

e. What phenotypic ratios would you expect in the offspring if the "mystery" plant were heterozygous?

f. What is the term for this type of cross?

10. Sex-linked Traits:

a. What is the probability that a human couple will give birth to a girl?

b. Hemophilia is an X-linked recessive trait. What is the probability that a woman who is a heterozygous carrier and a hemophiliac man will give birth to a daughter with hemophilia?

11.