Question

Which of the following is correct about ascaris? (a) Females are smaller than males (b) Posterior end of male curved dorsally (c) Females are longer than males (d) Fertilization is external

Short answer

Therefore, the correct answer is (c) Females are longer than males.

Step-by-step solution

Understanding Ascaris Characteristics

The first step is to analyze each of the options according to what we know about Ascaris. Ascaris is a type of roundworm where sexual dimorphism is present. This means that males and females have notable physical differences. Regarding size, females of Ascaris are generally larger than males.

Analyzing Male Body Structure

When looking at the body structure of males, they do indeed have a curved posterior end. However, it is essential to note that the male's posterior end curves ventrally (towards the belly), not dorsally (towards the back). So option (b) is not correct.

Studying Fertilization Process

Lastly, the fertilization process in Ascaris is internal, not external. Male roundworms deposit a copulatory plug into the female after copulation, which seals the vagina and stores sperm for fertilization, so, option (d) is not correct.

Key concepts

Sexual Dimorphism in Ascaris

Sexual dimorphism refers to the differences in appearance between male and female individuals of the same species. In Ascaris, this phenomenon is quite noticeable. The most significant difference lies in their size. Female Ascaris are generally larger and longer than their male counterparts. This size difference is more than just a number; it reflects the biological roles each sex plays in reproduction and survival. Male Ascaris are usually smaller and have a distinct feature at their posterior end, which is shaped to help in the mating process. Understanding these differences can help us recognize Ascaris genders more easily during examination.

Internal Fertilization in Ascaris

In the world of Ascaris, fertilization happens internally. This means that sperm is directly transferred from the male to the female, which is efficient and helps ensure successful reproduction in their environment. During mating, the male uses specialized spicules to attach to the female, delivering sperm directly into her reproductive tract. This process is followed by the formation of a copulatory plug, a fascinating feature that helps secure sperm within the female, safeguarding against loss and increasing the chances of successful fertilization. Internal fertilization is a key feature that differs from species that rely on external fertilization methods.

Male and Female Anatomy Differences in Ascaris

Male and female Ascaris differ anatomically aside from their size. One significant difference involves the male's posterior end, which is ventrally curved. This curve is not only a physical distinction but also serves a crucial function during reproduction. It allows the male to accurately position itself when transferring sperm to the female.

• Female Anatomy: Females lack a curved posterior end. They have a straight and longer body suited to accommodate numerous eggs.
• Male Anatomy: Males have a shorter, slimmer body and possess a ventrally curved tail. This structure supports the positioning of copulatory spicules.

By observing these anatomical differences, one can correctly differentiate between male and female Ascaris, which is essential for studies involving these parasites.