Biology 1001A Lecture Notes - Lecture 7: Amphiprioninae, Plant Reproductive Morphology, Sequential Hermaphroditism
13 Jun 2018
School
Department
Course
Cycle 7
Why Sex?
- reproducing sexually generates new multilocus combinations of alleles
- sex generates genetic diversity, new haplotypes
- sexual recombination creates genetically unique offspring therefore the offspring has
both of its parents DNA
- genetic exchange is not always associated with reproduction
- obligately asexual: reproduce by parthenogenesis (ovum but no fertilization)
- facultatively asexual: can reproduce as/sexually
- ex. bacteria transfer genetic material through their mating tube
to another bacterium… no sex
Monoecious: same individual is male and female in one, reproduces
sexually
- Sequential Monoecy: start life as one sex then switch later, ex. clown
fish switch to female later in their lives when they are big enough
- protandry: maleness occurs first in lifetime
- protogyny: female then male
- Simultaneous Monoecy: both sexes at the same time
(hermaphrodites)
Dioecious: separate sexes in separate individuals, reproduce
sexually
Sex Ratio Manipulation
- Non-hermaphrodites also need to balance male and female function
- if it is in relatively good condition (lots of resources), they might tend to produce sons
- if not in good condition = more daughters, because most girls can reproduce so theres less to
lose,
- because the male offspring will have poorer conditions, and may not be as strong as
competing male, resulting in less sexual fitness.
- If a female is produced instead, it will have a higher sexual fitness even in poor condition,
since males compete for access to the female
History of Sex
- The first living things, and the first eukaryotes, reproduced asexually
- meiosis and normal diploid sex probably appeared ~ 1.5 BYA
- isogamy (equal-sized gametes) in females and males appeared first, then anisogamy
(unequal gamete sizes), females have larger but fewer gametes, whereas males have
smaller but more gametes
- most living things reproduce mostly asexually; plants and animals are the exceptions
Benefits of Sexual Reproduction
- increases speed of evolution
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Document Summary
Reproducing sexually generates new multilocus combinations of alleles. Sexual recombination creates genetically unique offspring therefore the offspring has both of its parents dna. Genetic exchange is not always associated with reproduction. Obligately asexual: reproduce by parthenogenesis (ovum but no fertilization) Ex. bacteria transfer genetic material through their mating tube to another bacterium no sex. Monoecious: same individual is male and female in one, reproduces sexually. Sequential monoecy: start life as one sex then switch later, ex. clown fish switch to female later in their lives when they are big enough. Simultaneous monoecy: both sexes at the same time (hermaphrodites) Dioecious: separate sexes in separate individuals, reproduce sexually. Non-hermaphrodites also need to balance male and female function. If it is in relatively good condition (lots of resources), they might tend to produce sons. If not in good condition = more daughters, because most girls can reproduce so theres less to lose,
