Problem 112 - Objective Biology for NEET

Question

Sporophyte of mosses is more elaborated from (a) Ferns (b) Pinus (c) Polytrichum (d) Marchantia

Step-by-Step Solution

Answer

The sporophyte of mosses is more elaborated from (d) Marchantia.

Step 1: Understanding the terms

The sporophyte is a multi-cellular stage in the life cycle of plants and algae that undergo alternation of generations. It's important to understand the life cycle patterns in mosses (Polytrichum), ferns, conifer trees (Pinus) and liverworts (Marchantia).

Step 2: Comparing the Sporophytes

A Polytrichum is a genus of mosses which also has a sporophyte stage. Comparing the sporophyte stages of mosses and Polytrichum, there would be no major differences since they belong to the same category of plants. On the other hand, Ferns and Pinus have more complex sporophytes as compared to mosses. Lastly, Marchantia is a genus of liverworts which has a relatively simple sporophyte compared to mosses.

Step 3: Identifying the correct option

From the comparison, the sporophyte of mosses is more elaborated than that of Marchantia. Hence, the right answer is (d) Marchantia.

Key Concepts

Plant Life Cycles

Understanding the life cycle of plants is foundational in grasping how they grow, reproduce, and ultimately, sustain life on Earth. Plants have a unique life cycle called 'alternation of generations', which involves cycling between two distinct forms: the sporophyte and the gametophyte.

In mosses, the gametophyte is the dominant, green, and photosynthetic stage that we commonly see, while the sporophyte is usually attached to the gametophyte and depends on it for nutrition. It's important to note that the sporophyte is less elaborated in mosses compared to flowering plants like Pinus, and even ferns. In the case of mosses, sporophytes are simple structures with a stalk called a seta and a capsule where spores are produced.

Alternation of Generations

The alternation of generations is a complex process where plants alternate between two main stages throughout their life cycle: the haploid gametophyte and the diploid sporophyte. The sporophyte generation produces spores, which are haploid cells that can develop into a new organism without the need for fertilization. These spores grow into the gametophyte generation.

The gametophyte generation produces gametes (sperms and eggs) which combine during fertilization to give rise to a new sporophyte. This process creates a cycle that allows for genetic diversity and adaptation in plant species. In mosses, the sporophyte is relatively simple and remains attached to the gametophyte, relying on it for nutrients and water, while ferns and seed plants develop a more complex sporophyte independent of the gametophyte.

Comparative Plant Biology

When we delve into comparative plant biology, we explore the diversity in plant forms and structures across various species. By comparing the complexity of sporophytes among different groups, such as mosses, ferns, conifers, and liverworts, we can appreciate evolutionary adaptations that plants have undergone.

Mosses, for example, have sporophytes that are less complex and heavily reliant on the gametophyte. This can be contrasted with ferns and conifers, where the sporophytes are larger, more independent, and form complex organs like leaves and roots. Liverworts, such as Marchantia, have sporophytes even simpler than those of mosses. Understanding these differences highlights the incredible variation within plant lineages and allows us to track the evolutionary progression of plants from simple to more complex organisms.