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Inquiry Questions

Geometric and arithmetic progressions. A geometric progression increases by a constant factor (e.g., x 2 or x 3 or x 4), while an arithmetic progression increases by a constant difference (e.g., units of 1 or 2 or 3). Malthus contended that the human growth curve was geometric, but the human food production curve was only arithmetic.
What is the effect of reducing the constant factor by which the geometric progression increases? Might this effect be achieved with humans? How?

Answer:Reducing the factor by which the geometric progression increases (lowering the value of the exponent) reduces the difference between numbers of people and amount of food production. It can be achieved by lowering family size or delaying childbearing.

Molecules reflect evolutionary patterns. Vertebrates that are more distantly related to humans have a greater number of amino acid differences in this vertebrate hemoglobin peptide.
Where do you imagine a snake might fall on the graph? Why?

Answer: A snake would fall somewhere near the bird, as birds and snakes are closely related.

The molecular clock of cytochromec. When the time since each pair of organisms diverged in the fossil record is plotted against the number of nucleotide differences in the cytochrome c gene, the result is a straight line, suggesting this gene is evolving at a constant rate.
Do you think Dog differs from Cow more than might be expected based on other vertebrates? What might explain this?

Answer: Yes–distance to the line is greater. Random scatter is the most likely explanation: some point is bound to be furthest from the line.

Self Test

1). Which of the following characteristics is not a property of life?
    a). responding to stimuli
    b). dividing in two
    c). regulating internal conditions
    d). All of these are characteristics that define life
Answer: b

2). The process of inductive reasoning
    a). involves the observation of specific occurrences to construct a general principle.
    b). involves taking a general principle and applying it to a specific situation.
    c). is not used very often in the study of biology.
    d). all of the above
Answer: a

3). A goal of a scientist is to formulate a hypothesis
    a). that will never be proven false.
    b). that is essentially a theory explaining an observation.
    c). that is just a wild guess.
    d). that will be tested by experimentation.
Answer: d

4). An experiment testing a hypothesis will
    a). always support the hypothesis.
    b). always disprove the hypothesis.
    c). include a variable and a control.
    d). not be successful if the hypothesis is rejected.
Answer: c

5). Darwin's proposal, that evolution occurs through natural selection caused controversy because
    a). it challenged the existence of a Divine Creator.
    b). it challenged the views of earlier philosophers.
    c). it challenged a literal interpretation of the Bible.
    d). the explanation wasn't based on any observations.
Answer: c

6). Darwin was convinced that evolution had occurred based on observations that
    a). armadillos on the different islands off the coast of South America had slightly different physical characteristics.
    b). tortoises found on the different Galapagos Islands had different and identifiable shells.
    c). bird fossils that showed modifications from modern-day birds found in the same area.
    d). All of these observations were made by Darwin.
Answer: b

7). A key piece of information for Darwin's hypothesis that evolution occurs through natural selection was
    a). the fossil evidence.
    b). his work breeding of pigeons through artificial selection.
    c). Malthus' proposal that death, due to limited food supply, restricts population size.
d). geographic distribution of similar animals with slight variations in physical characteristics.
Answer: c

8). Which of the following "new" areas of scientific study could Darwin have used to strengthen his hypothesis?
    a). the age of the earth
    b). the mechanism of inheritance
    c). the expanded fossil record
    d). the geographical distribution of animal species
Answer: b

9). What are homologous anatomical structures?
    a). structures that look different but have the similar evolutionary origins
    b). structures that have similar functions but different evolutionary origins
    c). a bat's wing and a butterfly's wing
    d). a bat's wing and a human's leg
Answer: a

10). The themes of biology include all of the following except:
    a). chemistry.
    b). cell biology.
    c). genetics.
    d). evolution.
Answer: a

Test Your Visual Understanding

1). Which line on the graph indicates the growth of a population if resources were unlimited? Name three factors that limit population growth.
Answer: The blue line represents geometric progression and this type of growth occurs when resources are plentiful. Factors that limit population growth are factors that lead to death. Many factors can lead to death in a population such as limited supplies of food or water, disease, or natural disasters such as floods and fire.

2). By following the general path of evolution, would you say that fungi are more closely related to Archaebacteria or Bacteria? Why?
Answer: Fungi are more closely related to Archaebacteria than to Bacteria because the ancestors to Archaebacteria and Eukarya are on the same branch, which separated from the Bacteria before Archaebacteria and Eukarya groups formed.

Apply Your Knowledge

1). When breeding hunting dogs, the parents are selected for their keen sense of smell, which allows them to find the game (i.e., birds) faster. Breeders predict that this trait will be passed on to the dogs' offspring, producing a family of good hunting dogs. This is artificial selection. Explain how this same trait could be selected for through natural selection in a population of wild dogs.
Answer: A keen sense of smell is vitally important to dogs, especially to dogs in the wild. Unlike a domesticated dog that is fed by its owner, a wild dog is a hunter and needs to track its prey. A keen sense of smell would allow a wild dog a competitive advantage to track down prey compared to other dogs that didn't possess as keen a sense of smell. Through natural selection, the dogs with the keener sense of smell would acquire more food that would aid to its survival. Dogs that survived would have a greater opportunity to produce offspring, some of whom would inherit the keen sense of smell. Eventually, this characteristic would become more prevalent in the population, leading to a change in the make up of the population.

2). Assume four people are stranded on a deserted island and they reproduce once a year. How many people will be on the island after ten years using:
    a). a geometric progression with a factor of two.
    b). an arithmetic progression with a factor of two.

Answer: a). With geometric progression, the population would increase by a constant factor, which in this case is 2. Assuming that all four individuals can reproduce the number of people on the island after 10 years would be 4096:
    b). With arithmetic progression, the population would increase by a constant difference, which in this case is 2. Assuming that all four individuals can reproduce, the number of people on the island after 10 years would be 24:

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