Question

An important feature of land plants that originated during the diversification of streptophyte algae is a. the sporophyte. b. spores, which are dispersed in air and coated with sporopollenin. c. tracheids. d. plasmodesmata. e. fruits.

Short answer

The important feature of land plants that originated during the diversification of streptophyte algae is b) Spores, which are dispersed in the air and coated with sporopollenin.

Step-by-step solution

Understanding the process of diversification in streptophyte algae

The diversification of streptophyte algae is a period in biological history during which various features essential for land plants have evolved. It is important to understand that not all features listed in the options were developed during this diversification.

Evaluating options

Evaluating each option given, we can find that a) the sporophyte, c) tracheids, and e) fruits are adaptations of land plants, but did not appear until after the transition from water to land had already occurred, which excludes them from being developed during the diversification in streptophyte algae. Option d) plasmodesmata is a characteristic of all plant cells, not specific to the development in streptophyte algae

Finding the Correct Answer

Option b) Spores, which are dispersed in the air and coated with sporopollenin, meet the criteria of this question. Spores are not only specific to the streptophyte group of green algae (which includes land plants), but their development also coincides with the diversification of streptophyte algae. Therefore, option b) is the correct answer.

Key concepts

Land Plant Evolution

Land plant evolution marks a significant era in the history of life on Earth. This process began over 450 million years ago and involved the adaptation of certain features that enabled aquatic plants to thrive on land. The transition involved several key adaptations:

• Vascular tissues, like xylem and phloem, allowed for the distribution of water and nutrients throughout the plant.
• Cuticles, a waxy layer on the surface of leaves, helped to prevent water loss.
• Roots were developed to anchor plants and absorb water and minerals from the soil.

These innovations marked the beginning of a diverse and complex terrestrial plant world that includes not only mosses, ferns, and conifers, but also flowering plants.

Sporophyte Development

The development of the sporophyte is pivotal in the life cycle of plants. Sporophytes represent the diploid phase, which means they have double the number of chromosomes compared to their gametophyte counterparts. In the evolutionary history of plants, the transition from gametophyte dominance to sporophyte dominance was crucial.
This shift allowed organisms to explore new strategies for reproduction and adaptation.

• Sporophytes produce haploid spores through meiosis, which can disperse and land in a favorable environment to grow into a new organism.
• This generation depends less on water for fertilization, offering plants a wider range of habitats.

Sporopollenin Spores

One of the most remarkable features that evolved during the diversification of streptophyte algae is the formation of spores coated with sporopollenin. This compound provides a resilient outer layer that is highly resistant to environmental stressors like UV radiation and desiccation.
These adaptations were essential for early plants as they transitioned to life on land, where the protective effects of water were no longer available.

• Sporopollenin helps spores survive long periods of air travel before they settle in a suitable location.
• This durability is key to the efficient reproduction and dissemination of plants across diverse landscapes.

Tracheids in Plants

Tracheids are specialized cells that play an integral role in water transportation within vascular plants. They are part of the xylem and are long, tubular cells with thickened, lignin-reinforced walls, which prevent them from collapsing under pressure.
As plants adapted to terrestrial environments, efficient water transportation became pivotal.

• Tracheids facilitate the upward movement of water and nutrients from roots to leaves.
• Their structure also provides mechanical support, helping plants grow taller and compete for sunlight.

The evolution of tracheids represented a major breakthrough in plant evolution, enabling them to colonize diverse habitats.

Plasmodesmata in Plant Cells

Plasmodesmata are microscopic channels that traverse the cell walls of plant cells, allowing for the direct exchange of substances between adjacent cells. This feature is critical for maintaining the integrity and functionality of plant tissues.
In the context of plant evolution, plasmodesmata ensure

• Efficient transport of nutrients, signaling molecules, and water across cells.
• Coordination of cellular activities, contributing to the overall growth and development of the plant.

These connections reflect a sophisticated level of cellular communication, which is fundamental for plant survival and adaptation across various environments.