Problem 240 - Objective Biology for NEET

Question

Assertion: Fertilization in sponge is internal. Reason: Sponges are aquatic organisms.

Step-by-Step Solution

Answer

The assertion and reason are correct but the reason is not the correct explanation of the assertion.

Step 1: Understanding the Assertion

This step is about understanding the assertion, which states that fertilization in a sponge is internal. This implies that the process of fertilization i.e., the fusion of sperm and egg to form a zygote happens inside the body of the sponge.

Step 2: Understanding the Reason

This step involves understanding the reason provided that being an aquatic organism has to do with frogs having internal fertilization. Aquatic organisms are those that live in water.

Step 3: Connecting Assertion and Reason

In this step, the connection between the assertion and the reason is made. After understanding both the assertion and the reason, one might conclude that being an aquatic organism has an effect on the mode of fertilization. However, the mode of fertilization (whether it's internal or external) is not necessarily determined by whether an organism is aquatic or not. For example, both frogs (aquatic organisms) and birds (non-aquatic organisms) have external fertilization.

Step 4: Final Analysis

Because the assertion is a fact and true, and the reason is also a fact, but they do not correlate logically, the answer is that the assertion and reason are correct but the reason is not the correct explanation of the assertion.

Key Concepts

Internal Fertilization

Internal fertilization is a fascinating process that refers to the union of sperm and egg within the body of an organism. This means that for organisms such as sponges, fertilization does not take place in the outside environment but rather inside the sponge’s body.

This type of fertilization provides certain advantages:

• Protection: The sperm and egg are protected from external environmental factors such as water currents and predators.
• Higher success rate: Since the gametes are kept in a controlled environment, the chances of successful fertilization are increased.
• Adaptation: It is particularly useful for species living in environments where aquatic conditions can fluctuate.

Sponges, with their internal fertilization, show how various organisms have adapted to increase their reproductive success.

Aquatic Organisms

Aquatic organisms are creatures that live predominantly or entirely in water. They can be found in oceans, rivers, lakes, and even small ponds. These organisms have adapted over time to thrive in aquatic environments, with special adaptations such as gills or fins in fish, and unique skin surfaces in amphibians.

However, the aquatic nature of an organism does not necessarily dictate its mode of fertilization:

• External Fertilization: Seen in many aquatic organisms such as fish and amphibians, where eggs and sperm are released into the water.
• Internal Fertilization: Like that in sponges, where the fusion of gametes occurs inside the organism.

Aquatic organisms have diverse reproductive strategies to ensure the continuity of their species.

Sponge Reproduction

Sponge reproduction is an intriguing aspect of marine biology. Sponges can reproduce both sexually and asexually, providing flexibility in their reproductive strategies. In sexual reproduction, they commonly exhibit internal fertilization.

Sponges release sperm into the water, which is drawn into another sponge through a special opening called the osculum. Inside, the sperm meets the eggs, and fertilization occurs internally. This adaptation is crucial for their survival as it protects the gametes from the harsh aquatic environment.

• Asexual Reproduction: Sponges can also reproduce asexually through budding or fragmentation. This allows them to survive and proliferate even when conditions aren't ideal for sexual reproduction.
• Hermaphroditism: Many sponges are hermaphrodites, meaning they possess both male and female reproductive organs, which increases the likelihood of successful reproduction.

The ability of sponges to reproduce both internally and asexually demonstrates their remarkable adaptability to aquatic environments.