The text below shows a diagram of a single pair of chromosomes in different stages of either mitosis or homologous meiosis. Please identify the diagram that represents anaphase of meiosis. A) I B) III In meiosis, homologous chromosomes are separated during anaphase. Which phase does this occur in? A) anaphase B) prophase C) mitosis Imagine that there are twenty-five different species of protists living in a tide pool. Some of these species reproduce both sexually and asexually, while others can only reproduce asexually. The pool gradually becomes infested with disease-causing viruses and bacteria. Which species is most likely to thrive in this changing environment? The asexually reproducing species, the sexually and asexually reproducing species, or the sexually reproducing species? Because sexual reproduction allows for genetic variation, the sexually reproducing species are more likely to thrive.
The Correct Answer and Explanation is:
Of course. Here are the correct answers and a detailed explanation for the questions on the worksheet.
Correct Answers
- Question 46: Which diagram represents anaphase I of meiosis?
The correct answer is A) I. - Question 47: Which diagram represents anaphase II of meiosis?
The correct answer is B) II. (Note: The circled answer D on the worksheet is incorrect; diagram V represents metaphase II). - Question 48: In meiosis, homologous chromosomes are separated during ______.
The correct answer is A) anaphase I. - Question 49: …Which species are more likely to thrive in the changing environment?
The correct answer is C) the sexually reproducing species.
Explanation
The questions cover key processes in meiosis and the evolutionary advantages of different reproductive strategies.
Meiosis Stages (Questions 46, 47, and 48)
Meiosis is a two-part cell division process that produces gametes (sperm and egg cells). Its main goal is to reduce the number of chromosomes by half and create genetic diversity.
- Anaphase I (Diagram I): The defining event of anaphase I is the separation of homologous chromosomes. In Diagram I, you can see the paired chromosomes (each still composed of two sister chromatids) being pulled to opposite poles of the cell. This is the “reductional division,” where the chromosome number is halved. This directly answers question 48, which asks when homologous chromosomes are separated.
- Anaphase II (Diagram II): Meiosis II is much like mitosis. Its goal is to separate the sister chromatids. In Diagram II, you can see individual chromatids being pulled apart to opposite poles. These are now considered individual chromosomes. This is the key difference from anaphase I, where the sister chromatids remained attached.
Sexual Reproduction and Environmental Change (Question 49)
The question about the protists in a tide pool tests the understanding of the core benefit of sexual reproduction: creating genetic variation. In a stable, unchanging environment, asexual reproduction can be very efficient. It allows a well adapted organism to create many identical, equally well adapted offspring quickly.
However, the scenario introduces a significant environmental change in the form of disease causing viruses and bacteria. This change acts as a powerful selective pressure. For the asexually reproducing species, every individual is a genetic clone. If the parent organism is susceptible to a new virus, all of its offspring will also be susceptible. A single successful pathogen could wipe out the entire population.
In contrast, sexual reproduction combines genes from two different parents, creating genetically unique offspring. This process shuffles existing genes into new combinations. Because of this genetic variation, it is statistically likely that some individuals in the sexually reproducing population will, by random chance, possess a combination of genes that provides resistance to the new diseases. While many individuals may still perish, the resistant ones will survive and reproduce, passing their advantageous genes to the next generation. This allows the species as a whole to adapt and thrive in the new, hostile environment. Therefore, the sexually reproducing species have a significant survival advantage over the asexually reproducing ones when faced with a new challenge like disease.
