A species of rotifer, a small freshwater invertebrate, lost the ability to reproduce sexually millions of years ago. A remarkable feature of its life cycle is the ability to withstand dry conditions. When the rotifer's environment dries out, so does the rotifer, and it can be blown to a new area. Rotifers that land in water will rehydrate and resume an active life. A major pathogen of these rotifers is a species of fungus that cannot survive drying. Some scientists hypothesize that drying rids the rotifers of this pathogen. Why might the ability to withstand drying reduce any potential advantage of sexual reproduction in this rotifer species?

Verified step by step guidance

1. Understand the role of sexual reproduction: Sexual reproduction typically provides genetic diversity, which can be advantageous for adapting to changing environments or resisting pathogens.
2. Consider the rotifer's environment: The rotifer's ability to withstand drying and rehydrate in new areas means it can escape environments where pathogens are present, reducing the need for genetic diversity to combat these pathogens.
3. Evaluate the impact of drying on pathogens: Since the fungus pathogen cannot survive drying, the rotifers are naturally protected from this threat when they dry out, diminishing the need for sexual reproduction as a defense mechanism.
4. Analyze the trade-off: The rotifer's ability to survive drying and escape pathogens may outweigh the benefits of genetic diversity provided by sexual reproduction, making asexual reproduction more advantageous in this context.
5. Conclude the hypothesis: The ability to withstand drying likely reduces the advantage of sexual reproduction because the rotifers can avoid pathogens without needing genetic diversity, thus favoring asexual reproduction.

Key Concepts

Asexual Reproduction

Asexual reproduction is a mode of reproduction where offspring are produced by a single organism without the involvement of gametes. This process results in genetically identical offspring, allowing rapid population growth and survival in stable environments. In rotifers, asexual reproduction eliminates the need for mates, which can be advantageous in fluctuating environments where finding a partner is challenging.

Desiccation Tolerance

Desiccation tolerance refers to an organism's ability to survive extreme drying conditions. Rotifers can enter a dormant state when their environment dries, allowing them to be transported to new locations by wind. Upon rehydration, they resume normal activity, which helps them escape pathogens like fungi that cannot survive desiccation, thus providing a survival advantage without the need for genetic diversity from sexual reproduction.

Pathogen Resistance

Pathogen resistance is the ability of an organism to withstand or eliminate infections by pathogens. In rotifers, desiccation acts as a natural defense mechanism against fungal pathogens that cannot survive drying. This reduces the evolutionary pressure to develop genetic diversity through sexual reproduction, as the rotifers can effectively rid themselves of pathogens by simply drying out and relocating.