The Question is from neet-botany plant-kingdom , and it was created by the author K SURESH KUMAR

Question

The complex life cycle of *Laminaria* involves an alternation of generations.  Which statement accurately describes the dominant phase and its ploidy?

K SURESH KUMAR · Accepted Answer

## CORE INFORMATION
✓ **Answer**: B
## CONCEPT FRAMEWORK
 **Primary Concept**: Alternation of generations in brown algae
 **Related Topics**:  Life cycles, haploid, diploid, sporophyte, gametophyte
 **Prerequisites**: Understanding of basic cell biology (ploidy), plant life cycles.
## SOLUTION PATHWAY
**Given Information**:
  *Laminaria* has an alternation of generations.
**Method & Steps**:
 1. Understand alternation of generations: This involves a multicellular haploid phase (gametophyte) and a multicellular diploid phase (sporophyte).  These phases alternate in the life cycle.
  Reasoning:  The question asks which phase is dominant in *Laminaria*.
  Formula/Rule: None directly applicable; this is a biological concept.
 2. Identify the dominant phase in *Laminaria*: In *Laminaria*, the sporophyte is the larger, more conspicuous, and longer-lived phase. The gametophyte is relatively small and short-lived.
  Working:  We need to determine which generation (sporophyte or gametophyte) is dominant and its ploidy (haploid or diploid).
  Key Point: The dominant phase is the one that is more easily observed and represents the majority of the organism's life cycle.
 3. Determine the ploidy of the dominant phase: The sporophyte is diploid (2n) because it results from the fusion of gametes (fertilization).
  Result: The sporophyte is the dominant phase, and it is diploid.
  Verification: This aligns with the typical life cycle of *Laminaria* and other brown algae.
 ## OPTION ANALYSIS
A :x: Incorrect. The gametophyte is not the dominant phase in *Laminaria*.
B ✓: Correct. The sporophyte is the dominant and diploid phase in *Laminaria*.
C :x: Incorrect. Both phases are not equally dominant, and the sporophyte is diploid, while the gametophyte is haploid.
D :x: Incorrect. The gametophyte is not dominant, and it is haploid, not diploid.
 ## LEARNING AIDS
 **Common Mistakes**:
  1.Confusing the dominant phase: Students might mistakenly assume the gametophyte is dominant due to its role in producing gametes.
   How to avoid:  Focus on the size, longevity, and overall prominence of each phase in the organism's life cycle.
  2.Misunderstanding ploidy: Students might incorrectly assign ploidy to each phase.
   How to avoid: Remember that the sporophyte is diploid (2n), resulting from fertilization, while the gametophyte is haploid (n) and produces gametes by meiosis.
 **Quick Tips**:
  1.Remember that in many brown algae (like *Laminaria*), the sporophyte is the larger, more noticeable phase.
  2.Use a diagram of the *Laminaria* life cycle to visualize the alternation of generations and the relative sizes of the sporophyte and gametophyte.

K SURESH KUMAR · Answer

The gametophyte is dominant and haploid.

K SURESH KUMAR · Answer

The correct Option is "The sporophyte is dominant and diploid."

K SURESH KUMAR · Answer

Both gametophyte and sporophyte are equally dominant and diploid.

K SURESH KUMAR · Answer

The gametophyte is dominant and diploid.

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