Question

1. Explain why a life cycle that includes meiosis must also include fertilization. What is the advantage of such a life cycle?

2. Why are prokaryotes especially useful in bioremediation?

3. Describe some examples of how prokaryotes are helpful to humans and some examples of how they are harmful to humans?

4. Explain why a female can be heterozygous for an X-linked gene, but a male cannot.

5. What is a practical or clinical use of knowing the base sequence of a gene?

6. The human genome project has discovered that humans have about 30,000 genes, many fewer than earlier estimates of 100,000 genes. What implication does this have about the way human genes function?

7. Are viruses alive and deserving of the status of organisms or are they just biologically active chemicals? Defend a position on this based on what you know about what viruses are and how they work.

8. Plants in the tropical rain forest often grow faster than those in temperate forests. Explain how what you know about how the factors that affect transpiration would attribute to this.

9. Commercials on TV use food and sex as their most attractive selling points. Explain how flowers use the same tow attractants to “sell” their pollen to animals.

10. Virtually, all plants compete directly with all the plants around them. Why is this so?

11. Assume that protein synthesis always reads along a chromosome three bases at a time to code for each successive amino acid in a protein. There are two kinds of point mutations, a base substitution and a base deletion. How are these two types of mutations likely to affect the protein coded by a mutated gene?

12. Why do most human societies have laws or customs against marrying close relatives?

13. The majority of all plants are seed plants. What is the advantage of a seed? How do plants that lack seeds meet the needs served by seeds?

14. Describe the similarities and difference between the biochemical pathways of aerobic respiration and photosynthesis in eukaryotic cells. Include in your discussion the major reaction, the end products, and energy transfers.

15. Explain how a trait can skip generations.

16. Describe the fluid mosaic model of the plasma membrane. Discuss the role of the membrane in the movement of materials through it by each of the following processes.
    1. Active transport
    2. Passive transport

17. Describe negative and positive feedback loops, and discuss how feedback mechanisms regulate each of the following.
    1. The menstrual cycle in a nonpregnant human female.
    2. Blood glucose levels in humans.

18. Discuss the adaptations that have enabled flowering plants to overcome the following problems associated with life on land.
    1. The absence of an aquatic environment for reproduction
    2. The absence of an aquatic environment to support the plant body
    3. Dehydration of the plant

Answer 1

1. Meiosis involves the production of haploid gametes (i.e., they contain half the genetic makeup as comapred to a somatic cell). Hence, the formation of gametes must be followed by fertilization to restore the genetic makeup of the organism (to make it diploid). An advantage of meiosis is that it helps to maintain the ploidy of a cell, and also allows for the introduction of changes (via recombination) that can prove beneficial to the organism.

2. Prokaryotes are capable of utilizing a wide range of components as a source of nutrient and energy, and they also tolerate a wide range of environmental conditions of growth. These characteristics make them very useful in bioremediation process.

3. Prokaryotes are useful to humans in a number of ways :

• They are used in the commercial production of many food items like cheese, vinegar, sour cream etc.
• They are used in the production of genetically engineere insulin.
• Gut microbes aid in digestion of food and compete with external bacteria for growth, thus also serving a protective role.

Prokayotes can also prove to harmful :

• Many prokarytes call diseases in humans.
• They can contaminate and spoil food, water, etc.

4. A female receives one X chromosome from mother and one from the father, and thus can either be homozygous or heterozygous for the X chromosome. Males on the other hand receive only one copy of X chromosome from the mother. The other sex chromosome is Y that is received from the father. Hence, males cannot be heterozygous for X-linked gene.