Problem 9 - Biology

Question

Which one of these characteristics is present in land plants and not in Charales? a. alternation of generations b. flagellated sperm c. phragmoplasts d. plasmodesmata

Step-by-Step Solution

Answer

c. phragmoplasts

Step 1: Identify the Terms

Understand the key terms and their definitions: - Alternation of generations: A life cycle involving both haploid and diploid phases. - Flagellated sperm: Sperm cells that use a flagellum for movement. - Phragmoplasts: A cell structure involved in forming the cell plate during cell division. - Plasmodesmata: Channels between plant cells that allow for transport and communication.

Step 2: Analyze Charales Characteristics

Study the characteristics of Charales (a group of green algae): - They reproduce through a form of alternation of generations but mostly in a simple form.- They have flagellated sperm.- They form plasmodesmata between cells.- They do not form phragmoplasts.

Step 3: Compare with Land Plants

Compare the characteristics of Charales with those of land plants: - Land plants also exhibit alternation of generations. - Land plants also have flagellated sperm. - Land plants form plasmodesmata. - Land plants uniquely form phragmoplasts during cell division.

Step 4: Determine the Correct Answer

Based on the comparison, the characteristic that is unique to land plants and not found in Charales is the formation of phragmoplasts.

Key Concepts

Alternation of Generations

Alternation of generations is a unique life cycle feature in many plants, including land plants and some green algae like Charales. This cycle involves two distinct phases: the haploid (gametophyte) phase and the diploid (sporophyte) phase.
The gametophyte phase produces gametes (sperm and eggs) via mitosis. Once fertilization occurs, a diploid zygote forms. This zygote grows into the sporophyte.
The sporophyte phase generates spores through meiosis. These spores then grow into new gametophytes.
For land plants, the alternation of generations is more complex than in Charales. In Charales, the haploid phase dominates, while in land plants, the diploid phase is more prominent.

Flagellated Sperm

Flagellated sperm are sperm cells that move using a whip-like tail called a flagellum. Both Charales and land plants produce flagellated sperm.
Flagellated sperm are crucial for fertilization in aquatic environments, as they swim through water to reach the egg.
Charales, being aquatic algae, rely heavily on flagellated sperm for reproduction.
Land plants, especially lower plants like ferns and mosses, also use flagellated sperm. However, higher land plants (like flowering plants) often use other methods like pollen for fertilization without the need for water.

Phragmoplasts

Phragmoplasts are structures that form during cell division in land plants, particularly during cytokinesis. They help in forming the cell plate, which eventually becomes the cell wall.
During cell division, the phragmoplast directs vesicles containing cell wall materials to the center of the cell.
These vesicles fuse to form the cell plate, which divides the parent cell into two daughter cells.
Unlike land plants, Charales do not form phragmoplasts; instead, they use a simpler mechanism to divide cells.

Plasmodesmata

Plasmodesmata are small channels that connect plant cells to each other, allowing for communication and transport of substances between cells.
They play a crucial role in maintaining the plant's physiological balance by facilitating the exchange of nutrients, hormones, and other signaling molecules.
Both Charales and land plants have plasmodesmata. These channels enable them to transport vital substances and communicate efficiently across cells.
The presence of plasmodesmata is essential for plant growth and development, helping coordinate responses to environmental stimuli.