Biology Mentorship Program Cycle 7 Workshop (2024-25) PDF

Cycle 7: All About Sex! Biology Mentorship Program  Follow us on Instagram and Tiktok! Stay up to date on what events are happening @uwobiologymentors Infographics and Con...

Cycle 7: All About Sex! Biology Mentorship Program  Follow us on Instagram and Tiktok! Stay up to date on what events are happening @uwobiologymentors Infographics and Connections for every cycle! BMP 2024-25 iClicker + Discord In-workshop questions will be polled through iClicker! Join code: Join the BMP If join code not working: Discord! GNOC Look up “BMP 2024-2025” Slides + Resources will be OR Scan the QR Code posted here: Outcomes for Cycle 7: Lecture 1 On multiple choice exams, you should be able to identify... 1. examples of sexual and of asexual reproduction 2. how sexual reproduction affects the maintenance of genetic variation in a population 3. meanings of dioecious, monoecious, sequential monoecy, simultaneous monoecy 4. examples and predictions of the size-advantage model of sex change 5. which form of reproduction (sexual or asexual) is most common in animals 6. the costs and benefits of reproducing sexually as opposed to asexually Lecture 14: Why Sex? What is Sex? Exchange of genetic material between 2 individuals ○ Egg + sperm (fusion of gametes) ○ Bacterium transferring plasmid to another Bacterium Sex creates new combinations of alleles! What is Sex? Part 2 Sexual reproduction: Production of new living organisms by combining genetic material from two other individuals Reproduction does not always involve sex! Nor do sexual processes always involve reproduction! obligately asexual facultatively sexual obligately asexual Mini-Exercise: Is it Isogamous or Anisogamous? Anisogamous Isogamous Sexually reproducing species may be… Isogamous Anisogamous Iso = same: Produce equal Produce different sized/motility sized gametes gametes Can have either have a distinct Ex. Large eggs and small, motile mating type or different types. sperm Ex. Yeast (has an A and alpha Usually has 2 sexes – type of gametes that must fuse) dioecious or monoecious Self-fertilizing – can fuse gametes from the same individual to make a zygote Dioecious vs Monoecious Dioecious: each individual is either male or female Monoecious: each individual has both male and female functions/structures, eg. certain flowers ○ Hermaphrodites: animals that are monoecious Simultaneous: both sexes at the same time, eg. earthworms Sequential: born one sex, but then switch to another at a certain threshold, eg. clownfish Size-Advantage Model (for sequential hermaphrodites) Determines when it is advantageous to be male and when its advantageous to be female Point of intersection on graph is where sex changes Organisms take on the sex that makes them more fit at that time in their life Protandry = male → female Protogyny = female → male ○ Proto = first ○ Gynecologist = doctor who specializes in female health Example: Clownfish Clownfish start as males and become females! Question An experiment on two plants showed that one reproduces asexually while the other reproduces sexually. Over multiple generations, the sexually reproducing plant shows more genetic diversity. What is the primary reason for this increased diversity? A. Sexual reproduction combines genetic material from two parents, creating unique combinations. B. Asexual reproduction leads to more mutations, decreasing genetic variation. C. Sexual reproduction allows each generation to revert to the genetic profile of a common ancestor. D. Asexual reproduction requires more energy, leading to genetic stability. Question ANSWER + EXPLANATION: Male first → protandry Question Which of the following describes facultative asexual reproduction? A. Species reproduce only by producing clones of the mother. B. Species can reproduce both asexually or sexually depending on the environment. C. Gametes fuse from the same individual to create a zygote. D. Species reproduce using equal-sized gametes. Question A study on a hermaphroditic fish species shows that reproductive success increases significantly once the fish reaches a certain size. This is likely due to: A. The species engaging in obligate asexual reproduction once mature. B. Size-advantage model, where larger individuals gain reproductive benefits by changing sex. C. Obligate sexual reproduction, requiring multiple mates for success. D. Dioecious reproduction, with one sex dominating reproduction. Question A species of plant reproduces sexually with anisogamous gametes. What does this imply about the nature of its reproductive cells? A. Its gametes are identical in size, promoting equality in fertilization. B. The plant produces different-sized gametes, with one being more mobile. C. The plant's gametes are all immobile, leading to high fertilization rates. D. The plant can self-fertilize due to identical gametes.  Origins & History of Sex 3.5 BYA - first cells reproduced 1.2 BYA - eukaryotic asexually sex appears 2 BYA - bacteria start Now - most multicellular exchanging genes organisms repr. sexually; (parasex) obligately asexual species are rare & extinction-prone Costs of Sexual Reproduction Risky: Time consuming, dangerous. Cost of Meiosis: Only half of your alleles pass on, possibility of more errors compared to binary fission. Cost of Males: Only females can grow the population → reproductive output reduces if male. Sexual selection may favour traits that increase mating success, but reduce survival. WHY IS SEXUAL REPRODUCTION BETTER? Long-Term: Favours best allele combination. Gets rid of harmful alleles. Muller’s Ratchet: Asexual repr. → distribution moves right over time (number of deleterious mutations increase until extinction) Sexual repr. → creates new genotypes that breaks this trend → flattens the curve, but take a long time to do so.  Sexual Reproduction: Environmental Benefits Immediate Effect Red Queen Principle Lottery principle: more sex Must evolve as rapidly in unpredictable as possible to keep up environments increases with evolving chances of survival population Evolutionary arms races: New & rare allele keeping up with other combos can reduce species (host-parasite parasite’s ability to interactions) → want to infect others outcompete the diversifying population Question Which of the following correctly sequences the major milestones in the evolution of sexual reproduction based on the provided timeline? A) Gene exchange among prokaryotes initiates → Complex cellular sex mechanisms emerge → Primitive cells replicate independently of gene sharing B) Initial cellular replication without gene sharing → Mechanisms for gene transfer between bacteria develop → Sexual reproduction structures arise in eukaryotes C) Autonomous cell division precedes genetic exchange mechanisms → Sexual reproduction processes emerge within eukaryotic cells → Gene sharing among early microbes begins D) Early single-celled organisms begin replication → Eukaryotic cellular complexity introduces sexual reproduction → Bacteria adopt gene transfer mechanisms Answer Which of the following correctly sequences the major milestones in the evolution of sexual reproduction based on the provided timeline? A) Gene exchange among prokaryotes initiates → Complex cellular sex mechanisms emerge → Primitive cells replicate independently of gene sharing B) Initial cellular replication without gene sharing → Mechanisms for gene transfer between bacteria develop → Sexual reproduction structures arise in eukaryotes C) Autonomous cell division precedes genetic exchange mechanisms → Sexual reproduction processes emerge within eukaryotic cells → Gene sharing among early microbes begins D) Early single-celled organisms begin replication → Eukaryotic cellular complexity introduces sexual reproduction → Bacteria adopt gene transfer mechanisms Question The "Red Queen principle" as an explanation for the persistence of sexual reproduction primarily emphasizes which of the following evolutionary advantages? A) Reduction of the cost associated with finding a mate B) Enhancement of population growth by allowing all individuals to reproduce C) Maintenance of genetic diversity to evade parasite adaptation D) Elimination of deleterious mutations through asexual reproduction Answer The "Red Queen Principle" as an explanation for the persistence of sexual reproduction primarily emphasizes which of the following evolutionary advantages? A) Reduction of the cost associated with finding a mate B) Enhancement of population growth by allowing all individuals to reproduce C) Maintenance of genetic diversity to evade parasite adaptation D) Elimination of deleterious mutations through asexual reproduction  Lecture 15: Sexual Selection Outcomes for lecture 15 How and why sexual reproduction places different selective forces on males vs females Distinction between intersexual and intersexual selection Why males usually compete for access to females, not vice versa; and why this pattern is reversed in some species Which sex usually has higher potential fitness Which sex usually has higher average fitness How sex differences in parental investment affect which sex is competitive and which sex is choosy Intrasexual vs. Intersexual Selection elk Competition among INTRASEXUAL individuals of the same sex (“within”) e.g., fighting, nest building, sperm competition bowerbirds INTERSEXUAL One sex chooses a mate (“between”) Who chooses and who competes? Parental Investment Choosier sex = more invested Competing sex = less invested LOW-INVESTING SEX COMPETES FOR ACCESS TO HIGH-INVESTING SEX Why (usually) females choose and males compete Anisogamy One sex produces a large gamete and one produces a smaller gamete Female produces an egg (larger) Male produces a sperm (smaller) Sexual Dimorphism - Opposite sexes have difference in size or appearance - Parental investment affects the degree of sexual dimorphism - Eg. lions. Females provide most parental care → Males are bigger because of sexual selection Sexual Dimorphism - Biparental care - Both sexes provide parental care - Sexual selection on both = little to no sexual dimorphism Potential vs. Average Fitness higher potential fitness same average fitness Differing Selective Forces MALES FEMALES Maximize quantity Maximize quality Thus, reproduction is limited by... Access to females Finite gametes ○ Competition with Time for growing other males and rearing offspring Why be choosy? DIRECT BENEFITS INDIRECT BENEFITS Good parents Good alleles Food, territory, Survival and protection for attractiveness of offspring offspring Gifts Sexy sons hypothesis Parental Investment Differences Males aren’t always the competing sex ○ Phalaropes ○ Seahorses Key Point: The sex with the greater total parental investment will be the choosier sex. Question: What happens when... BOTH SEXES invest equally in the offspring —which sex is sexual selection acting upon? A. Males B. Females C. Both ANSWER: What happens when... BOTH SEXES invest equally in the offspring —which sex is sexual selection acting upon? A. Males B. Females C. Both How About in Humans? For the most part, both look for similar qualities In humans, bilateral symmetry is an attractive in a partner Also depends on type of mating opportunity (short or long term) ○ Wealth vs physical attractiveness? Question: Which of the following would be an example of an indirect benefit when choosing a partner? A) Protection B) Food C) Good parent D) Good alleles ANSWER: Which of the following would be an example of an indirect benefit when choosing a partner? A) Protection B) Food C) Good parent D) Good alleles Question: ANSWER: Question: ANSWER:  Term heavy cycle: Make a flowchart → Connect and summarize ideas Eg. Sexual vs Asexual → further subtypes → Examples → advantages/disadvantages → Environmental influence: stable/unstable Also… when in doubt, break down to the roots of words!  Questions? Good luck to anyone writing the calc midterm this weekend!