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The sample size is an important feature of any empirical study in which the goal is to make inferences about a population from a sample. In practice, the sample size used in a study is usually determined based on the cost, time, or convenience of collecting the data, and the need for it to offer sufficient statistical power. In complex studies ...
The effective population size (N e) is the size of an idealised population that would experience the same rate of genetic drift as the real population. The effective population size is normally smaller than the census population size N, partly because chance events prevent some individuals from breeding, and partly due to background selection and genetic hitchhiking.
Factors that contribute to the relative fitness of offspring size is either the resources the parents provide to their young or morphological traits that come from the parents. The overall success of the offspring after the initial birth or hatching is the survival of the young, the growth rate, and the birthing success of the offspring.
The net reproductive rate is the number of offspring an individual is expected to produce during its lifetime: = means demographic equilibrium. One may then define the generation time T {\displaystyle T} as the time it takes for the population to increase by a factor of R 0 {\displaystyle \textstyle R_{0}} .
Heritability may be estimated by comparing parent and offspring traits (as in Fig. 2). The slope of the line (0.57) approximates the heritability of the trait when offspring values are regressed against the average trait in the parents. If only one parent's value is used then heritability is twice the slope.
Spending equal amounts of resources to produce offspring of either sex is an evolutionarily stable strategy: if the general population deviates from this equilibrium by favoring one sex, one can obtain higher reproductive success with less effort by producing more of the other. For species where the cost of successfully raising one offspring is ...
For example fecundity is the potential to for a female to become pregnant and carry that pregnancy to a live birth in demography, while in clinical medicine it refers to actual production of live offspring.
This type of curve is characteristic of species that produce a large number of offspring (known as r-selected species). This includes most marine invertebrates. For example, oysters produce millions of eggs, but most larvae die from predation or other causes; those that survive long enough to produce a hard shell live relatively long.