Question

Which of the following exhibits a haplodiplontic lifecycle?

• A. Fucus
• B. Chlamydomonas
• C. Gelidium
• D. Ectocarpus

Hint:

Haplodiplontic lifecycles are characteristic of some algae and bryophytes.

Answer 1

The Correct Option is D

Haplodiplontic life cycle analysis:

(A) Fucus - Incorrect: This brown alga has a diplontic life cycle (only zygote is diploid).

(B) Chlamydomonas - Incorrect: This green alga exhibits haplontic life cycle (only zygote is diploid).

(C) Gelidium - Incorrect: This red alga shows triphasic life cycle (not classic haplodiplontic).

(D) Ectocarpus - Correct: This brown alga demonstrates true haplodiplontic (alternation of generations) with isomorphic gametophyte and sporophyte stages.

The correct answer is (D) Ectocarpus, as it shows equal alternation between haploid and diploid multicellular phases.

Answer 2

A haplodiplontic lifecycle involves alternating generations of haploid (n) and diploid (2n) phases. Key characteristics include:

Haploid phase : Gametes fuse to form a diploid zygote.

Diploid phase : The zygote undergoes meiosis to produce haploid spores.

Spores : Develop into haploid gametophytes, which produce gametes.

(A) Fucus : Belongs to the brown algae (Phaeophyceae) and exhibits a diplontic life cycle .

(B) Chlamydomonas : A green alga that follows a haplontic lifecycle (only haploid phase is dominant).

(C) Gelidium : A red alga that follows a diplontic lifecycle (only diploid phase is dominant).

(D) Ectocarpus : A brown alga that follows a haplodiplontic lifecycle.

Thus, Ectocarpus exhibit haplodiplontic lifecycles.