Compare the reproductive system of the earthworm with that of Ascaris. Be sure to note both similarities and differences. 2. explain how earthworms demestrates cephalization 3. How does the digestive system of an earthworm and an Ascaris differ?
The Correct Answer and Explanation is :
1. Comparison of the Reproductive System of Earthworm and Ascaris:
Similarities:
- Both earthworms and Ascaris are hermaphroditic in nature, meaning each individual contains both male and female reproductive organs.
- Both species utilize external fertilization. Earthworms exchange sperm with other individuals during copulation, while Ascaris fertilization takes place within the body but involves sperm and egg from separate individuals.
- Both species have separate sexes but hermaphroditism is a notable characteristic for earthworms, whereas Ascaris are dioecious (males and females are distinct).
Differences:
- In earthworms, the male and female reproductive organs are present in each individual. They have testes and ovaries. Fertilization occurs externally, and they lay eggs.
- In Ascaris, the reproductive system is more complex. Ascaris males are smaller, with a curved tail for mating, while females are larger. Females can produce thousands of eggs that are fertilized internally, and the fertilized eggs are then excreted to the environment to develop into larvae.
- Earthworms have a specialized structure called a clitellum, which secretes a mucus cocoon for egg deposition, whereas Ascaris females lay eggs directly into the environment.
2. Cephalization in Earthworms:
Cephalization in earthworms is demonstrated through the presence of a well-defined anterior end where the brain and sensory organs are located. Earthworms have a simple brain, which is a cluster of ganglia, and they exhibit bilateral symmetry. They also have sensory structures like the setae (bristles) that help them sense their environment. The nervous system is concentrated at the anterior end, showing an evolution of cephalization.
3. Digestive System Differences between Earthworms and Ascaris:
- Earthworms: Earthworms possess a complete digestive system, meaning they have both a mouth and an anus. The digestive tract includes a pharynx, esophagus, crop, gizzard, intestine, and anus. They process organic matter from soil in a complex manner, using a gizzard for grinding and an intestine for absorption.
- Ascaris: Ascaris, being a parasitic roundworm, has a simpler digestive system. They have a mouth and an anus, but their digestive tract is tubular and functions primarily for absorbing nutrients directly from the host’s body. They lack specialized organs for grinding food, relying on the host’s digestive process