BIOL1004 Chap.5 Sexual Reproduction and Sexual Selection
Sexual Reproduction and Sexual Selection
Sex is widespread among multicellular eukaryotes and present in some single-celled organisms, so the question is why it persists despite costs. The two-fold cost compares halved reproductive output with asexual exponential growth when only one sex directly produces offspring.
Recombination load occurs when recombination breaks apart a high-fitness allele combination, illustrated with A and a frequencies and AA as the highest-fitness genotype. Muller's ratchet describes the irreversible accumulation of deleterious alleles in small asexual populations when the least-loaded class is lost.
A no-pathogen arm provides a baseline, while the fixed-pathogen arm separates disease pressure from reciprocal evolution. A correlation between a display and mates secured supports sexual selection but does not alone identify the chooser's mechanism. A strong experiment answer identifies arms, controlled contrast, prediction, observed pattern and the conclusion actually supported.
What this chapter covers
- 01
widespread among multicellular eukaryotes and present in some single-celled organisms, so the question is why it persists despite costs.
- 02
The two-fold cost compares halved reproductive output with asexual exponential growth when only one sex directly produces offspring.
- 03
Recombination load occurs when recombination breaks apart a high-fitness allele combination, illustrated with A and a frequencies and AA as the highest-fitness genotype.
- 04
Sex can increase genetic variation by creating new combinations of alleles, giving selection more combinations to act upon.
- 05
DNA repair can use non-homologous end joining or homology-directed repair, with homologous information providing a template.
- 06
lost.
- 07
The Red Queen hypothesis predicts that recombination helps hosts keep pace with evolving parasites rather than reaching a permanent optimum.
- 08
The nematode experiment crossed C. elegans with Serratia marcescens in three arms: no pathogen, a non-evolving pathogen and a co-evolving pathogen.
Chapter 5 model reasoning
- unweightedThe Red Queen hypothesis predicts that recombination helps hosts keep pace with evolving parasites rather than reaching a permanent optimum. The point is not the isolated label: it is how the statement contributes to weighing the costs and benefits of sex using predictions and experimental evidence. State the subject, process and outcome in that order, then test whether reversing any direction word would change the biological meaning. That discipline turns a remembered phrase into an explanation.
- unweightedThe nematode experiment crossed C. elegans with Serratia marcescens in three arms: no pathogen, a non-evolving pathogen and a co-evolving pathogen. Use this as a comparison rule. Name the shared feature first, then the feature that separates the cases, and finish with the evidence or observation that would let you choose between them. Avoid adding an unstated mechanism merely because it is familiar from general biology.
- unweightedIts questions asked how pathogen presence affects host reproductive mode and how pathogen evolution changes that response. Read it as a mechanism with a starting condition and a result. A complete account identifies what changes, what remains fixed and the scale at which the conclusion applies. If a number or date is not needed for that mechanism, do not let uncertain precision replace the causal explanation.
Key terms
- Recombination load
- Loss of favourable allele combinations when recombination breaks them apart.
- Muller's ratchet
- Accumulation of deleterious mutations in finite asexual populations.
- Red Queen hypothesis
- Sex and recombination are favoured in ongoing co-evolutionary races.
- Sexual selection
- Selection arising through unequal mating success.
- Bateman's principle
- A proposed sex difference in what most limits reproductive success.
Sexual Reproduction and Sexual Selection FAQ
What is the core reasoning skill in Sexual Reproduction and Sexual Selection?
The core skill is weighing the costs and benefits of sex using predictions and experimental evidence. A strong experiment answer identifies arms, controlled contrast, prediction, observed pattern and the conclusion actually supported.
Which distinction is easiest to reverse in Chapter 5?
A no-pathogen arm provides a baseline, while the fixed-pathogen arm separates disease pressure from reciprocal evolution. Sexual selection concerns differences in mating success and can favour traits that do not maximise survival.
What should I confirm on MyLearning for this chapter?
Use MyLearning for any missing topic pages, live assessment instructions and the complete Week Review Quiz pool. Do not extend the chapter beyond the published scope.
Exam move
Start with a closed-note reconstruction of the chapter's main relationship. Write each directional pair in both words and a small diagram, then answer the worked example without looking at the model. Use the two practice items to diagnose whether the error is vocabulary, sequence, evidence or scope.
Finish by checking the live MyLearning topic and Week Review Quiz, because this guide does not replace missing course pages or current instructions.
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