Survival Rate

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Survival Rate


in biology, the average probability of survival and reproduction of the organisms of each generation of a species (population). The survival rate is measured by the ratio of the number of adults that reproduce to the number born in each generation (or the number of eggs de-posited, spawn laid, seeds ripened, and so forth).

Under unfavorable conditions the survival rate (like fertility) decreases, and a population declines. Under favorable conditions the survival rate increases, stabilizing or augmenting the population. The survival rate increases by many orders in the course of progressive evolution. Thus, the average survival rate increases from 10~7-10~6 percent in bacteria, unicellular organisms, and plants to 10-30 percent in higher animals. This is associated with the development of several systems that promote the safety of the organism and reduce loss in all phases of ontogeny (development of multicellularity, differentiation of organs, perfection of self-regulation and homeostasis, increase in the amount of yolk in an egg, shift to internal fertilization, viviparity, active con-cern for offspring, and so forth). An increase in the survival rate during evolution is accompanied by a regular decrease in fertility. For example, in animals with small eggs deficient in yolk that are laid directly in water, the females deposit many million eggs at a time; however, in species that have large well-protected eggs and are capable of guarding their young, the females deposit only ten to 100 eggs. Maintenance of the optimum survival rate is important for evolution because higher rates can dangerously lower the effectiveness of natural selection and the evolutionary flexibility of the species.

The term “survival rate” is also used in research on the effect on the organism of various unfavorable factors, such as ionizing radiation. It means the percentage of organisms surviving exposure to such factors.


References in periodicals archive ?
While these numbers are alarming, the increase in cancer survival rates is a testament to our health services - and all those staff who have worked tirelessly to improve health outcomes for cancer patients.
The latest figures highlight the importance of raising awareness and increasing our understanding of cancer and show that, in Merseyside and the Wirral, we are further behind the rest of England when it comes to survival rates, which means there is a lot of work to be done to address this gap.
In comparison, ve-year breast cancer survival rates are 86.
12-15 By renal drafting, patients with ESDR experience more survival rate and better quality of life in all ages.
As with all cancers, early detection vastly improves survival rates.
It's a disgrace that such a small proportion of PCTs have survival rates that match the best figures in Europe, or even the best rates in Europe ten years ago.
virginica Paniagua-Chavez and Tiersch (2001) reported that the postthaw survival rate of trochophore larvae (12 h postfertilization at 25[degrees]C) was affected by the larval concentration used during cryopreservation, and decreased as the larval concentration increased, from about 100% at 10 individuals [mL.
In 32,845 women diagnosed with epithelial ovarian cancer between 1973 and 1997, the 5-year relative survival rate by year of diagnosis was 37% for 1973-1979, 39% for 1980-1989, and 43% for 1990-1997.
That survival rate was significantly different from the survival in patients with tumors that were 2-2.
At the University of Pittsburgh liver transplant program, the five-year survival rate of transplant recipients with antigen-positive hepatitis B is 45 percent, compared to 63 percent in recipients who are immune to the virus.
Based on protocol defined prognostic factors of patients who enrolled in the study (n=50), a 12-month survival rate of 25 percent would have been expected.

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