Problem 141 - Objective Biology for NEET

Question

Process similar to seed habit considerably is observed in (a) Homosporous species of pteridophytes (b) Heterosporous species of pteridophyte (c) All the members of pteridophytes (d) Not seen in pteridophyte

Step-by-Step Solution

Answer

The process similar to seed habit is considerably observed in heterosporous species of pteridophytes (option b).

Step 1: Understand Terms

First, understand the terms used in the question. Pteridophytes are a group of plants that produce spores for reproduction. Homosporous species produce spores of one type only, which can develop into both male and female gametophytes. Heterosporous species, on the other hand, produce two types of spores: microspores and megaspores, which develop into male and female gametophytes respectively. The seed habit is the development of a seed, a process found in gymnosperms and angiosperms (higher plants).

Step 2: Connect Terms with Concepts

Now that we understand these terms, let's connect the dots. Species that show a most similar process to seed habit are likely to be the ones that produce two different types of gametophytes. This is because the seeds in higher plants develop from the union of male and female gametophytes, similar to how different types of gametophytes develop in heterosporous species.

Step 3: Answer the Question

With the understanding of these concepts, we come to the conclusion that the process similar to seed habit is considerably observed in heterosporous species of pteridophytes.

Key Concepts

Homosporous species

In the fascinating world of pteridophytes, homosporous species are plants that produce only one type of spore. These spores are versatile, as they develop into gametophytes that can hold both male and female reproductive organs. This means that a single spore has the potential to give rise to both sperm and egg cells.
This incredible ability simplifies the reproduction process in homosporous species. However, it can lead to a lack of genetic diversity.

• All spores are identical, playing dual roles.
• Gametophytes can be one size, containing both reproductive organs.
• This may lead to self-fertilization, affecting variability in the population.

Despite the potential drawbacks, homosporous species have thrived over millions of years, showing their evolutionary significance.

Heterosporous species

Heterosporous species are a more complex class among pteridophytes. These plants produce two distinct types of spores: microspores and megaspores. Rather than being identical, these spores have distinct functions. Microspores develop into male gametophytes, while megaspores develop into female gametophytes.
This separation paves the way for genetic diversity, as it encourages cross-fertilization between different individuals.

• Microspores and megaspores are produced by different sporangia.
• This leads to the formation of separate male and female gametophytes.
• Greater genetic diversity is possible due to cross-fertilization.

Heterosporous species lay the groundwork for seed habits seen in higher plants, including gymnosperms and angiosperms, which involve male and female gametophytes joining together to create seeds.

Seed habit

The seed habit represents a significant evolutionary advancement seen in plants, particularly among gymnosperms and angiosperms. It is characterized by the development of seeds after fertilization, which ensures the protection and nourishment of the developing embryo. This habit contrasts with spore-reliant reproduction seen in pteridophytes.
Seeds provide several benefits:

• Protection for the embryo through a tough outer coat.
• Nutrient supply via endosperm for early-stage development.
• Enhanced dispersal mechanisms, increasing range for colonization.

By offering advantages like these, the seed habit has allowed plants to adapt to diverse environments and has been a key contributor to the success of flowering and cone-bearing plants.

Reproduction in plants

Reproduction in plants is a complex and varied process that can occur via spores or seeds, depending on the species. In pteridophytes, reproduction typically involves the release of spores into the environment. These spores develop into gametophytes, which then produce gametes (sperm and eggs) for fertilization.
There are two main reproductive strategies:

• Sporic reproduction: Utilized by plants like pteridophytes, involving a sporophyte stage where spores are produced.
• Seed reproduction: Found in gymnosperms and angiosperms, where fertilized ovules develop into seeds.

The journey from spore or seed to a fully developed plant is a marvel of nature. Each strategy offers unique benefits, ensuring plant species can thrive across various environmental conditions.