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Fecund
Fecundity is defined in two ways; in human demography, it is the potential for reproduction of a recorded population as opposed to a sole organism, while in population biology, it is considered similar to fertility, the natural capability to produce offspring, measured by the number of gametes (eggs), seed set, or asexual propagules. Superfecundity refers to an organism's ability to store another organism's sperm (after copulation) and fertilize its own eggs from that store after a period of time, essentially making it appear as though fertilization occurred without sperm (i.e. parthenogenesis). Human demography Human demography considers only human fecundity, at its culturally differing rates, while population biology studies all organisms. The term ''fecundity'' in population biology is often used to describe the rate of offspring production after one time step (often annual). In this sense, fecundity may include both birth rates and survival of young to that time step. Whi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fecundity Selection
Fecundity selection, also known as fertility selection, is the fitness advantage resulting from selection on traits that increases the number of offspring (i.e. fecundity). Charles Darwin formulated the theory of fecundity selection between 1871 and 1874 to explain the widespread evolution of female-biased sexual size dimorphism (SSD), where females were larger than males. Along with the theories of natural selection and sexual selection, fecundity selection is a fundamental component of the modern theory of Darwinian selection. Fecundity selection is distinct in that large female size relates to the ability to accommodate more offspring, and a higher capacity for energy storage to be invested in reproduction. Darwin's theory of fecundity selection predicts the following: # Fecundity depends on variation in female size, which is associated with fitness. # Strong fecundity selection favors large female size, which creates asymmetrical female-biased sexual size dimorphism. Althou ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fertility
Fertility is the capability to produce offspring through reproduction following the onset of sexual maturity. The fertility rate is the average number of children born by a female during her lifetime and is quantified demographically. Fertility is addressed when there is a difficulty or an inability to reproduce naturally, which is referred to as infertility. Infertility is widespread, with fertility specialists available all over the world to assist mothers and couples who experience difficulties having a baby. Human fertility depends on factors of nutrition, sexual behaviour, consanguinity, culture, instinct, endocrinology, timing, economics, personality, way of life, and emotions. Fertility differs from fecundity, which is defined as the ''potential'' for reproduction (influenced by gamete production, fertilization and carrying a pregnancy to term). Where a woman or the lack of fertility is infertility while a lack of fecundity would be called sterility. Demography I ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Semelparity And Iteroparity
Semelparity and iteroparity are two contrasting reproductive strategies available to living organisms. A species is considered semelparous if it is characterized by a single reproductive episode before death, and iteroparous if it is characterized by multiple reproductive cycles over the course of its lifetime. Iteroparity can be further divided into continuous iteroparity (primates including humans and chimpanzees) and seasonal iteroparity (birds, dogs, etc.) Some botanists use the parallel terms monocarpy and polycarpy. (See also plietesials.) In truly semelparous species, death after reproduction is part of an overall strategy that includes putting all available resources into maximizing reproduction, at the expense of future life (see § Trade-offs). In any iteroparous population there will be some individuals who die between their first and second reproductive episodes, but unless this is part of a syndrome of programmed death after reproduction, this would not be called ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Population Ecology
Population ecology is a sub-field of ecology that deals with the dynamics of species populations and how these populations interact with the environment, such as birth and death rates, and by immigration and emigration. The discipline is important in conservation biology, especially in the development of population viability analysis which makes it possible to predict the long-term probability of a species persisting in a given patch of habitat. Although population ecology is a subfield of biology, it provides interesting problems for mathematicians and statisticians who work in population dynamics. History In the 1940s ecology was divided into autecology—the study of individual species in relation to the environment—and synecology—the study of groups of species in relation to the environment. The term autecology (from Ancient Greek: αὐτο, ''aúto'', "self"; οίκος, ''oíkos'', "household"; and λόγος, ''lógos'', "knowledge"), refers to roughly the same fie ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Demography
Demography () is the statistics, statistical study of populations, especially human beings. Demographic analysis examines and measures the dimensions and Population dynamics, dynamics of populations; it can cover whole societies or groups defined by criteria such as education, nationality, religion, and ethnicity. Educational institutions usually treat demography as a field of sociology, though there are a number of independent demography departments. These methods have primarily been developed to study human populations, but are extended to a variety of areas where researchers want to know how populations of Social actions, social actors can change across time through processes of birth, death, and Human migration, migration. In the context of human biological populations, demographic analysis uses Public records, administrative records to develop an independent Approximation, estimate of the population. Demographic analysis estimates are often considered a reliable stan ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pregnant
Pregnancy is the time during which one or more offspring develops (gestation, gestates) inside a woman, woman's uterus (womb). A multiple birth, multiple pregnancy involves more than one offspring, such as with twins. Pregnancy usually occurs by sexual intercourse, but can also occur through assisted reproductive technology procedures. A pregnancy may end in a Live birth (human), live birth, a miscarriage, an Abortion#Induced, induced abortion, or a stillbirth. Childbirth typically occurs around 40 weeks from the start of the Menstruation#Onset and frequency, last menstrual period (LMP), a span known as the Gestational age (obstetrics), gestational age. This is just over nine months. Counting by Human fertilization#Fertilization age, fertilization age, the length is about 38 weeks. Pregnancy is "the presence of an implanted human embryo or fetus in the uterus"; Implantation (embryology), implantation occurs on average 8–9 days after fertilization. An ''embryo'' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fertilization
Fertilisation or fertilization (see spelling differences), also known as generative fertilisation, syngamy and impregnation, is the fusion of gametes to give rise to a new individual organism or offspring and initiate its development. Processes such as insemination or pollination which happen before the fusion of gametes are also sometimes informally called fertilisation. The cycle of fertilisation and development of new individuals is called sexual reproduction. During double fertilisation in angiosperms the haploid male gamete combines with two haploid polar nuclei to form a triploid primary endosperm nucleus by the process of vegetative fertilisation. History In Antiquity, Aristotle conceived the formation of new individuals through fusion of male and female fluids, with form and function emerging gradually, in a mode called by him as epigenetic. In 1784, Spallanzani established the need of interaction between the female's ovum and male's sperm to form a zygote in frog ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Parthenogenesis
Parthenogenesis (; from the Greek grc, παρθένος, translit=parthénos, lit=virgin, label=none + grc, γένεσις, translit=génesis, lit=creation, label=none) is a natural form of asexual reproduction in which growth and development of embryos occur in a gamete (egg or sperm) without combining with another gamete (e.g., egg and sperm fusing). In animals, parthenogenesis means development of an embryo from an unfertilized Gametophyte, egg cell. In plants, parthenogenesis is a component process of apomixis. In algae, parthenogenesis can mean the development of an embryo from either an individual sperm or an individual egg. Parthenogenesis occurs naturally in some plants, algae, invertebrate animal species (including nematodes, some tardigrades, water fleas, some scorpions, aphids, some mites, some bees, some Phasmatodea and parasitic wasps) and a few vertebrates (such as some fish, amphibians, reptiles and birds). This type of reproduction has been induced artificially ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ungulates
Ungulates ( ) are members of the diverse clade Ungulata which primarily consists of large mammals with hooves. These include odd-toed ungulates such as horses, rhinoceroses, and tapirs; and even-toed ungulates such as cattle, pigs, giraffes, camels, sheep, deer, and hippopotamuses. Cetaceans such as whales, dolphins, and porpoises are also classified as even-toed ungulates, although they do not have hooves. Most terrestrial ungulates use the hoofed tips of their toes to support their body weight while standing or moving. The term means, roughly, "being hoofed" or "hoofed animal". As a descriptive term, "ungulate" normally excludes cetaceans as they do not possess most of the typical morphological characteristics of other ungulates, but recent discoveries indicate that they were also descended from early artiodactyls. Ungulates are typically herbivorous and many employ specialized gut bacteria to allow them to digest cellulose. Some modern species, such as pigs, are omnivorous, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Evolutionary Biology
Evolutionary biology is the subfield of biology that studies the evolutionary processes (natural selection, common descent, speciation) that produced the diversity of life on Earth. It is also defined as the study of the history of life forms on Earth. Evolution is based on the theory that all species are related and they gradually change over time. In a population, the genetic variations affect the physical characteristics i.e. phenotypes of an organism. These changes in the phenotypes will be an advantage to some organisms, which will then be passed onto their offspring. Some examples of evolution in species over many generations are the Peppered Moth and Flightless birds. In the 1930s, the discipline of evolutionary biology emerged through what Julian Huxley called the modern synthesis of understanding, from previously unrelated fields of biological research, such as genetics and ecology, systematics, and paleontology. The importance of studying Evolutionary biology is ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Life Table
In actuarial science and demography, a life table (also called a mortality table or actuarial table) is a table which shows, for each age, what the probability is that a person of that age will die before their next birthday ("probability of death"). In other words, it represents the survivorship of people from a certain population. They can also be explained as a long-term mathematical way to measure a population's longevity. Tables have been created by demographers including Graunt, Reed and Merrell, Keyfitz, and Greville. There are two types of life tables used in actuarial science. The period life table represents mortality rates during a specific time period of a certain population. A cohort life table, often referred to as a generation life table, is used to represent the overall mortality rates of a certain population's entire lifetime. They must have had to be born during the same specific time interval. A cohort life table is more frequently used because it is able to ma ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Reproductivity
Reproduction (or procreation or breeding) is the biological process by which new individual organisms – "offspring" – are produced from their "parent" or parents. Reproduction is a fundamental feature of all known life; each individual organism exists as the result of reproduction. There are two forms of reproduction: asexual and sexual. In asexual reproduction, an organism can reproduce without the involvement of another organism. Asexual reproduction is not limited to single-celled organisms. The cloning of an organism is a form of asexual reproduction. By asexual reproduction, an organism creates a genetically similar or identical copy of itself. The evolution of sexual reproduction is a major puzzle for biologists. The two-fold cost of sexual reproduction is that only 50% of organisms reproduce and organisms only pass on 50% of their genes.John Maynard Smith ''The Evolution of Sex'' 1978. Sexual reproduction typically requires the sexual interaction of two specialize ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
