Chapter 22, Problem 1MC

In an alternation of generations life cycle, spores develop into __________ that produce gametes that fuse to give rise to __________.

1. a. haploid gametophytes; diploid sporophytes
2. b. diploid gametophytes; haploid sporophytes
3. c. haploid sporophytes; diploid gametophytes
4. d. diploid sporophytes; haploid gametophytes

Summary Introduction

Introduction:

A spore is a smallest unit of sexual and asexual reproduction that may be adapted for the dispersal and for the survival in an unfavorable condition. Spores are agents of asexual reproduction. Spores are the cells produced by bacteria and fungi that can develop into new bacteria either directly or indirectly. Alteration of generation is the type of cycle that occurs in those plants and fungi that have distinct sexual haploid and asexual diploid stages.

Answer to Problem 1MC

Correct answer:

In an alteration of generation life cycle, spores develop into haploid gametophytes that produce gametes that fuse to give rise to diploid sporophytes. Therefore, option (a) is correct.

Option (a) is given as “haploid gametophyte; diploid sporophytes”.

Explanation of Solution

Justify reason for the correct statement:

The haploid spores germinate and grow into a haploid gametophyte. When it becomes mature it divides through mitosis that does not alter the number of chromosomes, so when this gamete fuse to another gamete to produce a zygote which will develop into a diploid sporophytes

Hence, option (a) is correct.

Justify reasons for the incorrect statements:

Option (b) is given as “diploid gametophytes; haploid sporophytes”.

When a spore germinates it will give rise to a haploid gametophyte which will further divide by mitosis to form diploid sporophytes. Hence, it is a wrong answer.

Option (c) is given as “haploid sporophytes; diploid gametophytes”.

During the process of spore germination first gametophytes are developed that are haploid in nature after this the diploid sporophytes occur. Hence, it is a wrong answer.

Option (d) is given as “diploid sporophytes; haploid gametophytes”.

During the process of spore germination first gametophytes are developed that are haploid in nature after this the diploid sporophytes occur. Hence, it is a wrong answer.

Hence, options (b), (c), and (d) are incorrect.

Conclusion

A haploid spore will always form haploid gametophyte, which will then divide to form haploid gametes. These gametes will fuse into other gametes to form diploid sporophytes.