The meaning of fecundity is the reproductive rate (fecundity rate) or the performance of an individual or the population. In biology, what is the meaning of fecundity? Fecundity is the estimate of the number of gametes produced by an individual. In simpler terms, fecundity is the quantification of the number of individuals added to the population. Show
Biology definition: Demographically, what is fecundity? Demographers have a different way to express this. They define fecundity as (1) the possibility of becoming pregnant or (2) the likelihood of exposure to being pregnant, which is essentially dependent on the sexual pattern and preventive measures being taken. In humans, the fecundity is reflective of the duration between female menarche and menopause. Fecundity is influenced by the accessibility to the resources and access to possible mates. Thus, fecundability is the ability of a female to produce progeny in a given reproductive cycle. A contrasting term to fecundity is reproductivity (synonyms: reproductive output; reproductive potential; fertility), which represents the number of individuals or the proportion of the population that was deducted or died from the population in a specified period of time. Fecundity vs. FertilityFecundity is often confused with fertility and vice versa, however, these terms are completely different. So, what is the difference between fecundity and fertility? Fecundity is the capability of an individual or population to produce offspring whereas fertility is the number of offspring produced by the population or the individual. Fertility is the actual number of offspring produced and not the rate of reproduction. The individual capable of reproducing is known as fertile. Fecundity is the natural ability of a person to reproduce and that depends on the health and availability of healthy and genetics. On the other hand, fertility is the number of offspring per couple in a population. Fertility is dependent on various factors, such as lifestyle, stress, emotional and reproductive health, willingness, availability of a potential mating partner, and preventive measures being taken. Fecundity is not equivalent to fertility as the translation of the ability to reproduce is further dependent on a number of societal, environmental, and physiological factors. Complete or 100% translation of fecundity into fertility is seldom possible in any given population whether they may be of animal or plant. Fecundity is a developmental and genetic trait that advances within a specific framework. Table 1: Fecundity vs. FertilityFecundityFertilityBiological capacity or physical ability to reproduce offspringThe actual giving birth of mothers or the number of offspring produced by the population or the individualStarts at first menstruation or menarche (or puberty)Starts at sexual intercourseChiefly cannot be modifiedCan be modifiedDependent on various factors, e.g. societal, environmental, genetics, health, and physiological factorsDependent on various factors, e.g. lifestyle, stress, emotional and reproductive health, willingness, availability of a potential mating partner, and preventive measures being taken.Fecundity and fertility are closely associated terms but they are viewed differently. Not all pregnancies result in the birth of a live child. When that happens the couple does not contribute to the population growth. (Källén, B., 1988). In this regard, conception is associated with a couple’s fecundity. However, the capacity to produce live offspring is the couple’s fertility. Despite the distinctions of use between fecundity and fertility, the two terms are sometimes used synonymously. (U.N. Asian Development Institute Bangkok, 2003). Methods to Estimate FecundityThe method to measure fecundity varies as per species and their mode of reproduction as well. In aquatic animals (except mammals and reptiles), the count of oocytes from a spawning female is used to measure fecundity. In highly fecund spawners, to measure fecundity, the fraction of ovarian tissue of known weight/volume and the consequential oocyte densities are extrapolated to the total weight/volume of the ovary using a gravimetric or volumetric method. The size of oocytes is also employed to measure fecundity. The day-specific probabilities of conception with respect to the day of ovulation along with the assessment of time to pregnancy are taken into account to measure fecundity in humans. Fecundity in Ecology and Biological ImportanceIn ecological terms, the net reproductive rate is an important parameter that takes into account fecundity. Net reproductive rate is the average number of offspring that a female can produce throughout its reproductive life span, with due consideration of fertility with respect to age and rate of death in a given period of time. 1. Energy investmentAn estimate of population fecundity improves the ability to translate research in reproductive physiology into foreseen effects on fertility. Thus, fecundity is a very important parameter to study in ecology and animal biology. In ecology, fecundity is also an indication of the amount of energy that is spent on raising offspring. As a general rule of thumb, fecundity is inversely proportional to the amount of energy spent. Let’s understand it more simply, the higher the fecundity i.e. higher the ability to reproduce, the lower would be the requirement of energy to be spent on raising offspring i.e., parental care. As per this rule, there are two possibilities: (1) a group of the population that can reproduce in higher numbers and (2) a group of the population that can reproduce a limited or few offspring in their lifetime. Thus, as per the inverse fecundity and energy rule:
This inverse fecundity and energy rule are similarly applicable to the Plant Kingdom as well. Here, of course, the energy investment is not in terms of parental care, however, it is in terms of energy-rich quality seeds. Plants with low fecundity will produce a few or limited numbers of seeds with high energy which thereby have the higher or maximum possibility of survival, for example, coconuts. On the other hand, plants with higher fecundity will produce a large number of seeds (e.g. dandelion) but each seed will have a low amount of energy. Thus, the survival chances of these seeds would therefore be low. 2. Reproduction timeAnother important aspect of fecundity and ecology is the time of reproduction. Again, the population can be divided into two basic groups depending on the time when an organism starts to reproduce:
3. ParityParity is indicative of the number of any individual that can reproduce in its life span. Some organisms can reproduce their progeny only once in their lifetime while others can exhibit multiple reproductions. Thus, fecundity can follow two patterns:
Factors affecting FecunditySome of the factors affecting fecundity are explained below. These factors include body size, environmental conditions, are choice of a mating partner.
Metabolic rate, dispersal capacity, survival probability, and fecundity are some of the factors that cause the disparity in body mass among individuals or species. However, it is important to understand that in a species, the ratio of combined offspring mass to maternal mass tends to roughly remain constant. This means that females with larger bodies tend to have higher fecundity and larger offspring. Thus, evolutionarily, a larger body gives a selective advantage to large-sized females and their offspring.
The fecundity is affected by environmental conditions. Environmental conditions can affect maternal body condition and survival. Thus, affecting the fecundity.
The theory of mate selection is based on the fact that a female may select a superior mating partner in order to increase the fecundity. The selection of a superior mating partner is linked to producing genetically healthy and better-quality offspring with high fecundity. Certain species are involved in multiple mating. This is again linked to selecting a superior mating partner. Nevertheless, multiple mating can be huge energy investing activity for females. Multiple mating results in the improvement of fecundity due to the fact that egg production is stimulated by mating, fresh sperms help to maintain the fertility of eggs, egg production rate also increases with the mating. Multiple mating results in sperm-sperm competition. Two sperms compete to fuse with the ova. Again, by the theory of survival of the fittest, the sperm that apparently is superior will eventually fuse with the ova. This results in the formation of a zygote likely with a viable genetic constitution. Males usually have higher fecundity than females. Biological and Ecological Significance of Fecundity MeasurementsFecundity is an essential component of studying the population composition model. To understand the life history strategy and the factors affecting the, it is equally important to study population fecundity, fertility, and survival rate. Different models are employed to study their cumulative effect on the life history strategy of a population. One such model is the stage-structured matrix population model. This model mathematically summarizes the population behavior using stage-specific estimates of vital rates (rates of birth, growth, maturation, fertility, and mortality) and it gives a relationship between the individual (and its selective pressures) and the population. This model gives a stable stage distribution which gives an estimate of the theoretical population composition that exhibits a fixed birth rate. Thus, the factors like the variation in the environment or any other intrinsic regulatory factor that change the theoretical population composition can be graded to study and predict their effect on the composition of the population. This model also gives the contribution of an individual to the future status of its population by taking into account fecundity, fertility, and survival rate. This is known as the reproductive value which essentially is the sum of the current and future reproductive values. By nature’s selection theory, reproductive value is the currency used by nature to generate a specific life-history approach. By natural law, reproductivity is to be maximized, thus the population model takes fecundity into account. While in matrix models, the changes in fertility (and survival) to population growth give a stage-specific sensitivity analysis. In this model, the reproductive value at a particular stage is calculated as the product of the sensitivity of all matrix elements that contain that stage and the stable stage proportion. Thus, a short-lived species has a tendency to exhibit higher fertility sensitivity than for survival. While the long-lived animals exhibit higher sensitivity towards survival than fertility. Thus, the factors that affect the population composition can be studied. What is population age structure and what are the three major age groups called?It is common in demography to split the population into three broad age groups: children and young adolescents (under 15 years old) the working-age population (15-64 years) and. the elderly population (65 years and older)
What occurs when an interaction benefits one species but has little if any effect on the other?Commensalism is a long-term biological interaction (symbiosis) in which members of one species gain benefits while those of the other species neither benefit nor are harmed.
Which of the following describes having more than one reproductive episode during a lifetime?In iteroparity, individuals of a species reproduce repeatedly during their lives.
Which of the following reproductive patterns are opportunists and reproduce when conditions are favorable or when disturbance opens a niche for invasion?r-Selected species are opportunists and reproduce when conditions are favorable or when disturbance opens a niche for invasion. Most species of this type go through irregular and unstable boom-and-bust cycles in population size.
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