Reproductive success is the production of offspring per reproductive event or lifetime of an individual. It is not limited to the number of offspring produced by an individual, but also the reproductive success of these offspring themselves. Reproductive success is distinct from fitness because individual success is not necessarily a determinant for the adaptive strength of a genotype because the effects of coincidence and the environment have no effect on those specific genes.  Reproductive success translates into a portion of fitness when the offspring are actually recruited into the breeding population. This is true if the quantity of offspring is not correlated with quality, but if not, then reproductive success must be adjusted by traits that predict juvenile survival to be measured effectively. Quality and quantity is about finding the right balance between reproduction and maintenance and the disposable soma theory of aging tells us that a longer lifespan will come at the expense of reproduction and thus longevity is not always related to high fertility.   Parental investment is an important factor in reproductive success because taking better care of the offspring will give them a fitness advantage later in life.  This includes mate choice and sexual selection as an important factor in reproductive success , which is another reason why reproductive success differs from fitness because individual choices and outcomes are more important than genetic differences.  Since reproductive success is measured over generations, Longitudinal studies are the preferred study type because they follow a population or individual over a long period of time to monitor the progress of the individual(s). These long-term studies are preferable because they negate the effects of variation in a year or breeding season.
Nutrition is one of the factors that affects reproductive success. For example, carbohydrate to protein ratio consumed in various amounts and more specifically. In some cases, the amount or ratio of intake is more dominant during certain stages of life. For example, in the Mexican fruit fly , male protein intake is significant only at the time of eclipse. Consumption at this time provides long lasting fertility. After this developmental stage, protein intake will have no effect and is not essential for reproductive success.  In addition, Ceratitis capitata was used to see how the protein influences mating success during the larval stage.Male was used. Males were fed either a high protein diet, consisting of 6.5g/100mL, or a no protein diet during the larval stage. Men who were given the protein had higher copulation than those who were not given the protein, which ultimately correlates with a higher mating success.  Protein-deprived black blow fly males have been observed to display a smaller number of oriented mounts and to inseminate fewer females than more lively fed males.  In still other instances, a lack of prey or an inadequate diet has been shown to partially or completely inhibit male mating activity. The sugar-fed males had a longer copulation time than the protein-fed flies, indicating that carbohydrates were more essential for the longer copulation period. 
In mammals, the amount of protein, carbohydrate and fat is seen to influence reproductive success. This was assessed among 28 female black bears assessed by measuring the number of cubs born. Using a variety of foods during the fall, including corn, herbs, red oak, beech, and cherries, the nutritional facts of protein, carbohydrate, and fat were noted, as each differed in percentage compositions. Seventy percent of bears that had a high-fat and high-carbohydrate diet produced cubs. In contrast, all 10 females who had a low-carbohydrate diet did not reproduce cubs, considering carbohydrate an important factor for reproductive success where fat was not a barrier. [11 1]
Adequate nutrition in the pre-mating time period has the greatest impact on various reproductive processes in mammals. Enhanced nutrition, in general, was most beneficial for oocyte and embryonic development during this time. As a result, progeny numbers and viability were also improved. Thus, proper nutritional timing during the pre-mating time is critical for the development and long-term benefit of the offspring. Florida scrub-jays were fed two different diets and were noted to have different effects on reproductive performance. One diet is high in protein and high in fat, and the other is only high in fat. The important result was that birds on high protein and high fat diets laid heavier eggs than birds on high fat diets. There was a difference in the amount of water inside the eggs, which accounted for the different weights. It is hypothesized that the added water resulting from an adequate protein-rich and fat-rich diet may contribute to chick growth and survival, therefore aiding in reproductive success. 
Dietary intake also improves egg production, which may also be believed to help produce viable offspring. Post-mating changes are observed in organisms in response to conditions necessary for development. This has been shown in two-spotted crickets where females were tested for food. It was found that women who had intercourse demonstrated a higher overall consumption than unmarried. Observations of female crickets showed that after laying eggs, their protein intake increased at the end of the second day. Therefore the female cricket requires a higher consumption of protein for the development of subsequent eggs and even for mating. More specifically, using geometric profiling analysis, post-intercourse females were fed a higher protein-rich diet. Unmarried and mated female crickets were given 2:1 and 3.5, respectively, instead of carbohydrates: In Japanese quail, the effect of diet quality on egg production was studied. Diet quality varies in the percentage composition of protein, with a high protein diet at 20% and a low protein diet at 12%. It was found that both the number of eggs produced and the size of the eggs were higher in the low-protein diet than in the low. What was found to be unaffected, however, was maternal antibody transmission. Thus, the immune response was not affected because there was still a source of protein, although less. This means that the bird is able to compensate for the lack of protein in the diet by protein reserves, for example. 
High concentration of protein in the diet is also positively correlated with gamete production in various animals. The formation of oothecae in brown-banded cockroaches was tested based on protein intake. A 5% protein intake is considered too low as it delays mating and an excessive amount of 65% protein kills cockroaches directly. Utheka production was more optimal for the female on a 25% protein diet.
Although proteins and carbohydrates tend to be essential for various reproductive functions, including copulation success, egg development and egg production, the proportion and amount of each is not fixed. These values vary in term of animals, from insects to mammals. For example, many insects may require a diet with a slightly higher protein to protein ratio of both protein and carbohydrate for reproductive success. On the other hand, a mammal such as a black bear would require a higher amount of carbohydrates and fat, but not necessarily protein. Different types of animals have different requirements based on their makeup. One cannot generalize because the results can be different in different types of animals, and even more so in different species.
Evolutionarily, humans adapt socially to their environment and co-exist with each other in a way that benefits the entire species. Cooperative breeding , the ability for humans to invest and help raise the offspring of others, is an example of some of their unique characteristics that set them apart from other non-human primates, even though some practice this system at a low frequency. We do.  One reason humans require more non-parental investment than other species is that they still depend on adults to care for them for most of their juvenile period. Cooperative breeding can be expressed through economic support that requires a human to invest financially in someone else’s offspring, or through social support, which may require active energy investment and time. .  This parenting system ultimately helps individuals increase their survival rate and overall reproductive success.  Hamilton’s law and kin selection are used to explain why this altruistic behavior is naturally selected and what non-parents gain by investing in offspring that are their own. Not there.  Hamilton’s law states that Rb > C where R = relatedness, B = benefit to the recipient, C = cost of the subsidiary. This formula describes the relationship that occurs between three variables for kin selection. Kin selection will most likely occur if the relative heredity of the helper is close with that of the offspring and their benefit exceeds the cost of the helper.  Even though selection of relatives does not benefit individuals who invest in the offspring of relatives, ensuring that genes are passed on to the next generation, it still affects the reproductive success of the population. enhances.
Some research has suggested that historically, women have had higher reproductive success rates than men. Dr. Baumeister has suggested that modern humans have twice as many female ancestors as male ancestors.
Males and females should be considered separately in reproductive success for their different limits in producing the maximum amount of offspring. Women have limitations such as the time of conception (usually 9 months), then breast-feeding which suppresses ovulation and makes her more likely to get pregnant again.  In addition, a woman’s ultimate reproductive success is limited by her ability to distribute her time and energy towards reproduction. Peter T. “The metabolic task of converting energy from the environment into viable offspring falls on the female, and the rate at which she can produce offspring is limited by the rate at which she can direct metabolic energy to work,” says Ellison . may” The logic of the transfer of energy from one category to another extends away from each individual category as a whole. For example, if a female has not yet reached menarche, she will only need to focus her energy on growth and maintenance because she cannot yet channel energy towards reproduction. However, once a female is ready to start putting energy into reproduction she will have less energy towards overall development and maintenance.
Females have restrictions on the amount of energy required to reproduce. As women go through conception, they have a certain obligation to produce energy in reproduction. However, males do not have this constraint and can therefore potentially produce more offspring because their commitment to energy in reproduction is less than that of females. All things considered, males and females are constrained for different reasons and the number of offspring they can produce. In contrast, males are not constrained by the timing and energy of conception or lactation. Females are also dependent on the genetic quality of their mate. This refers to the quality of the male’s sperm and the compatibility of sperm antigens with the female’s immune system. If humans in general, consider the phenotypic traits that characterize their health and body symmetry. The pattern of constraints on female reproduction is consistent across human life-history and across all populations.
One difficulty in studying human reproductive success is its high variability.  Every person, male or female, is different, especially when it comes to reproductive success and fertility. Reproductive success is determined not only by behavior (choice), but also by physiological variables that cannot be controlled. 
The Blurton-Jones ‘backload model’ tested a hypothesis that the length of the birth interval of kung hunter-gatherers allowed women to have children and to balance the energetic demands of pasture in a society where women had small children. had to be carried and pasture a sufficient distance”.  The reason behind this hypothesis is the fact that the birth interval allowed for a better chance of survival of the child and ultimately promoted evolutionary fitness. This hypothesis goes along with the evolutionary tendency of three areas to split one’s personal energy: growth, maintenance, and reproduction. This hypothesis is “good for securing an understanding of individual-level variation in fertility in small-scale, high-fertility, societies (sometimes referred to by demographers as ‘natural-breeding’ populations).  Reproductive Success is hard to study because there are so many different variables, and so many concepts are subject to each situation and environment.
natural selection and evolution
An understanding of the principle of natural selection is essential to complement a full understanding of reproductive success or biological fitness. Darwin’s theory of natural selection describes how the variation of genetic variation over time within a species allows some individuals to adapt to their environmental pressures, find suitable mates, and/or find a food source faster than others. Over time the same individuals pass their genetic makeup on to their offspring and so the frequency of this beneficial trait or gene increases within that population.
The same may be true for the opposite. If a person is born with a genetic structure that makes them less adapted to their environment, they may be less likely to survive and pass on their genes and therefore may see a reduction in the frequency of these deleterious traits. .  This is an example of how biological fitness, along with reproductive success, is a core component of the theory of natural selection and evolution.
Throughout evolutionary history, often an advantageous trait or gene will continue to increase in frequency within a population due to a decrease or decrease in the functionality of another trait. This is known as an evolutionary trade-off, and is related to the concept of pleiotropy, where a change in a gene has multiple effects. From Oxford Academic, “The resulting ‘evolutionary tradeoff’ shows the necessary agreement between the functions of many traits”.  This means that there is a balance between traits due to various limitations such as energy availability, resource allocation during biological development or growth, or limitations of genetic structure. An increase in effectiveness in one trait can result in a decrease in the effectiveness of other traits.
This is important to understand because if certain individuals within a population have a certain trait that enhances their fertility, that trait may develop at the expense of others. Changes in genetic makeup through natural selection are not necessarily changes that are either beneficial or harmful but changes that can be both. For example, an evolutionary change over time that results in higher reproductive success at a young age may eventually lead to a reduction in life expectancy for those with that particular trait.