Reproductive success
If offspring quantity is not correlated with quality this holds up, but if not then reproductive success must be adjusted by traits that predict juvenile survival in order to be measured effectively.
The disposable soma theory of aging tells us that a longer lifespan will come at the cost of reproduction and thus longevity is not always correlated with high fecundity.
[2][3] Parental investment is a key factor in reproductive success since taking better care to offspring is what often will give them a fitness advantage later in life.
These long term studies are preferable since they negate the effects of the variation in a single year or breeding season.
[6] In addition, Ceratitis capitata males were experimented on to see how protein influence during the larval stage affects mating success.
[8] In still other instances, prey deprivation or an inadequate diet has been shown to lead to a partial or complete halt in male mating activity.
Using different foods during the fall including corn, herbaceous, red oak, beech, and cherry, nutritional facts of protein, carbohydrate, and fat were noted, as each varied in percent compositions.
It is hypothesized that the added water resulting from the adequate protein-rich and fat-rich diet may contribute to development and survival of the chick, therefore aiding reproductive success.
Observations of female crickets showed that after laying their eggs, their protein intake increased towards the end of the second day.
The female crickets therefore require a larger consumption of protein to nourish the development of subsequent eggs and even mating.
Cooperative breeding, the ability for humans to invest in and help raise others' offspring, is an example of some of their unique characteristics that sets them apart from other non-human primates even though some practice this system at a low frequency.
[17] One of the reasons why humans require significantly more non-parental investment in comparison to other species is because they are still dependent on adults to take care of them throughout most of their juvenile period.
[17] Even though kin selection does not benefit individuals who invest in relatives' offspring, it still highly increases the reproduction success of a population by ensuring genes are being passed down to the next generation.
[18][19][20][21] Males and females should be considered separately in reproduction success for their different limitations in producing the maximum amount of offspring.
Females have limitations such as gestation time (typically 9 months), then followed by lactation which suppresses ovulation and her chances of becoming pregnant again quickly.
[22] In addition, a female's ultimate reproductive success is limited due to ability to distribute her time and energy towards reproducing.
All things considered, men and women are constrained for different reasons and the number of offspring they can produce.
The Blurnton-Jones 'backload model' "tested a hypothesis that the length of the birth intervals of !Kung hunter-gatherers allowed women to balance optimally the energetic demands of child bearing and foraging in a society where women had to carry small children and foraged substantial distances".
[23] Behind this hypothesis is the fact that spacing birth intervals allowed for a better chance of child survival and that ultimately promoted evolutionary fitness.
[23] Reproduction success is hard to study as there are many different variables, and a lot of the concept is subject to each condition and environment.
Over time those same individuals pass on their genetic makeup onto their offspring and therefore the frequency of this advantageous trait or gene increases within that population.
If an individual is born with a genetic makeup that makes them less suited for their environment, they may have less of a chance of surviving and passing on their genes and therefore may see these disadvantageous traits decrease in frequency.
