Question

Darwin hypothesized that there are definite steps to natural selection. Consider the model here. Use the Roman numerals (I - III) to guide you through the steps. Which is an accurate description of Darwin's hypothesized theory of natural selection?

A) Sexual reproduction of bacteria cause variation. Some bacteria survive and some do not. Over time all of the bacteria should become extinct.
B) In any population, variation exists. Some bacteria are resistant to antibiotics. Most bacteria die, but the bacteria that are resistant survive and reproduce.
C) In a population of bacteria that are exposed to antibiotics, some bacteria change their genetic make-up and survive. The new genetic make-up is passed on to offspring.
D) There is a change in the environment: an antibiotic is added. Some of the bacteria are capable of changing to the new environment. They survive and reproduce, passing along their favorable traits.

Answer 1

The answer is B because if there is variation there would be certain bacteria with a favorable trait to survive when the antibiotic is released.

Answer 2

The most appropriate answer would be D) There is a change in the environment: an antibiotic is added. Some of the bacteria are capable of changing to the new environment. They survive and reproduce, passing along their favorable traits.

Natural selection refers to the process by which organisms who are better adapted to the change in the environment have better chances for survival and reproduction.

The steps for natural selection can be explained as:

I. Inherited variation: Within a population, organisms often exhibit variations which can be inherited such as color, size, et cetera.

II. Competition: This is the phase in which organisms struggle to survive. During this, species usually produce more offspring as compared to the carrying capacity of the environment.

In the given situation, environment change is the addition of antibiotic.

III. Selection: It is the phase of differential reproduction that is, organisms who are best adapted to the environmental change have better chances to mature to reproductive age. They reproduce and pass the beneficial traits to the offspring.

Bacteria which are better adapted to the new environment survive, reproduce, and pass their beneficial traits to the next generation.

IV. Evolution: Changes in allele frequency in a population accumulate over time and leads to the evolution.