Module 9 Flashcards
3 Dimensions to Reproduction
- Fertility
~ production of offspring - a man or woman who is fertile has produced offspring
- often addressed as a rate of reproduction or of total number of children produced
- Fecundity
~ the capital to produce offsping - A man or woman who is fecund has the physiological ability ot reproduce, even if they choose not to
- A mesure of reproduction function
- Reproductive Value
~ expected reproduction in the future - Reproduction value peaks at the onset of reproduction, before any fertility
Fertility
- realized production of offspring
~ Birth rate
~ This will be partly related to fecundity but also to behavioral factors
~ completed fertility is the total number of offspring over the lifespan
Fecundity
- The capacity to produce offspring
~A man or woman who is fecund has the physiological ability to reproduce, even if they do not
~ Could be related to probability of ovulation or implantation, sperm production/ quality, fetal loss
In nutririonally stressed populations, lower probability of conception, but less control of fertility
- Birth intervals of ~3-4 years, total fertility of 5-7
In industrialized populations, high probability of conception, but significant control of fertility
- Birth intervals of one year, total of 2-4
Chimpanzees- short-term mating relationships
- Male choose for
~ High fecundity (conception likely)
~ High fertility females (experienced mothers)
Humans- long-term mating relationships
Male choice
- High reproductive value
- Cues of high fecundity
- Females with low fertility (few preexisting children)
For women
the ability to reproduce- fecundity- is highly sensitive to energy avilability
Ovarian functions
- Most anaimals are able to conceive very quickly, but may lose many pregnancies or infants in poor conditions
- Humans have a much harder time conceiving but lose fewer infants
- Human infants are extrz expensive- require a cautious strategy to aviod lost time and energy
The probability of conception is up and down-regulated in reponse to theri energetic condition
- not just on and off, but continual variation
- Adaptive regulation of reproductive timing to proobability of sucess
The probability of conception is up and down-regulated in repose to their energetic condition
- not just on and off, but continual variation
- Adaptive regulation of reproductive timing to probability of success
Energy balance
- The difference between calories consumed and calories expended
- Positive energy balancy -= weight gain
- Negative energy balance = weight loss
- High energy balance results in the accumulation of fat, but energy balance is not the same as ‘fatness’
% Body fat or BMI have relatively little effect of fecundity
Energy balance
- The difference between calories consumed and calories expended
- Positive energy balance -= weight gain
- Negative energy balance = weight loss
- High energy balance results in the accumulation of fat, but energy balance is not the same as ‘fatness’
% Body fat or BMI have relatively little effect of fecundity
For men
- energy availability is less of a constraint on fecundity because direct reproductive costs are low
- men in poor energy balance still produce viable sperm
Population variation in testosterone may be important for other reasons
- high testosterrone is costly to the immune system and promotes costly muscle growth during development
