Question

Which does not apply to all seed plants? a. Vascular tissues b. Diploid dominance c. single spore type d. All of the above

Short answer

Option C (single spore type) does not apply to all seed plants.

Step-by-step solution

Understanding the Options

We begin by examining each of the given options to determine what characterizes "seed plants." Seed plants are typically known for certain features, and we need to identify which feature listed does not apply to all of them.

Analyzing Option A: Vascular Tissues

Vascular tissues, including xylem and phloem, are structures that allow plants to transport water, nutrients, and food throughout the plant. All seed plants (gymnosperms and angiosperms) have vascular tissues, making this a characteristic that applies to all seed plants.

Analyzing Option B: Diploid Dominance

In the context of seed plants, diploid dominance refers to the life cycle where the dominant phase is diploid. In seed plants, the sporophyte (which is diploid) is the dominant phase, meaning this characteristic applies universally to seed plants.

Analyzing Option C: Single Spore Type

Single spore type refers to the production of a single type of spore, known as homospory. However, seed plants are generally heterosporous, producing two different types of spores: microspores and megaspores. Thus, not all seed plants have a single spore type, making this the correct answer to what does not apply to all seed plants.

Reviewing Option D: All of the Above

'All of the above' could only be correct if none of the features applied universally to seed plants. However, both vascular tissues and diploid dominance do apply to all seed plants. Therefore, option D cannot be correct.

Key concepts

Vascular Tissues

Vascular tissues are the lifelines of seed plants, enabling the transportation of essential substances. These tissues consist primarily of two main components:

• Xylem: Responsible for transporting water and minerals from the roots to the rest of the plant. It's composed of tubular structures that help in moving water upwards.
• Phloem: This tissue transports food produced in the leaves to other parts of the plant. It enables vital nutrients to reach areas that need them for growth and energy.

Both gymnosperms and angiosperms, the two main groups of seed plants, possess vascular tissues. This makes vascular tissues a universal characteristic among seed plants.
By facilitating efficient fluid movement, these tissues contribute to the plant’s growth, structural integrity, and survival in various environments.

Diploid Dominance

Diploid dominance refers to the stage in a plant's life cycle where the diploid phase, known as the sporophyte, is dominant. In seed plants, this phase is not only longer in duration but is also more visually prominent. Seed plants spend most of their lifecycle in the sporophyte phase. This means they have two sets of chromosomes, making them diploid. This phase leads to the production of seeds, which are crucial for the reproduction and propagation of the species.
The occurrence of diploid dominance helps in creating genetic diversity through sexual reproduction, ensuring that seed plants can adapt and thrive in changing environments. As a result, diploid dominance is integral to the biology of seed plants and is a trait they all share.

Heterospory

Heterospory is a term that describes the production of two different types of spores in plants. Most seed plants are heterosporous, which means they produce:

• Microspores: Develop into male gametophytes.
• Megaspores: Develop into female gametophytes.

This differentiation is vital as it leads to the formation of seeds, a critical aspect of reproduction in seed plants. However, not all plants are heterosporous. While most seed plants exhibit this feature, some primitive relatives or other plant groups might not. The advantage of heterospory lies in its ability to foster a more efficient and specialized reproductive process. It allows plants to maximize reproductive success by effectively managing resources and ensuring genetic variation through sexual reproduction.