Definition: 1) Producing live offspring from within the body of the parent (Lincoln et al., 1998). 2) Development of an embryo within the body of the parent, in part, resources passing directly from parent to embryo (Barnes et al., 2006).
Definition: The initial mortality rate (IMR) represents the mortality rate independently of the ageing process. Though there are different methods, the IMR is typically estimated from the mortality rate prior to its exponential increase with age, which can be obtained from the mortality curve (by looking at the baseline mortality prior to its exponential increase) or, for mice, by using t = 0.25 in the Gompertz equation.
Definition: The mortality rate doubling time (MRDT) is considered to be a measure of the rate of ageing. It is estimated from the slope of the Gompertz curve by: MRDT = 0.693/G where G is the exponential (Gompertz) mortality rate coefficient.
Definition: The duration of the development from fertilized, deposited or implanted egg to hatching/birth. Corresponds to egg incubation duration in oviparous animals and to gestation period duration in viviparous animals.