REPRODUCTION – Lecture #7 March 8, 2012
- why sex?
- Human reproduction: conception, early pregnancy loss, nausea and vomiting during
- Reproductive health in the modern World – may be strongly modified by the concept of
living with our past. Womens bodies which are adapted for heavy investment for offspring
but in a different type of environment than what women encounter today. Experiences may
protect ppl from poor reproductive outcome, but may also increase risk to other poor
reproductive outcome things such as cancers
Why sexual reproduction?
Reproduction and sex are different:
- making copies versus jumbling genes
- sex is not essential for life or reproduction: ie budding (eg plants, bacteria:bacterias that
don’t look for mates. They just grow and when they get bigger they split in two) ie.
parthenogenesis (eg aphids, rotifers – reproducing by generations with only females who
don’t have sex – lay eggs which are all females – parthenogeneis. There is no need for
males, and they live and reproduce just fine)
- other ways to share genetic material , eg. Bacterial conjugation – can be a one way two
way thing etc. Varying of genes over time.
Sexual reproduction is costly and hard to explain!:
- Sex isnt just something that happens without cost by the organisms that use it.
- No one has fully explained why organisms have sex
- Humans fall in the category where sex evolved deep in our evolutionary history before
primates – and we have retained the act due to uses, etc.
- How is sex costly? – biological fitness is when you make gentic copies of yourself – this is
normal for asexual reproduction. Sexual reproduction occurs with an offspring that is half
of you. Ie. daughter has half the genes of those that you have.
- asexual reproduction twice as efficient, avoids infection
- “two fold cost” of sex (# progeny + # gene copies) – you do better in total number of
copies of yourself.
- Males arent really all that necessary – bc 1 male can make 100 females preg. But a 100
males cant make 1 female prg.
- what fitness advantage outweighs benefit of asexuality?
- what is the point of males?
- why are th