But natural populations are finite in size; often they are small.
The only source of new gene combinations in asexual populations is mutation.
In areas of the world where populations eat local, fresh ingredients, populations do not become obese.
Over the past 200 years, hunting and invasive species reduced giant tortoise populations by an estimated 90 per cent, destroying several species and pushing others to the brink of extinction, although a few populations on remote volcanoes remained abundant.
In very small populations, however, some of that variation is lost by chance alone through random genetic drift.
In an ideal environment, one that has no limiting factors, populations grow at a geometric rate or an exponential rate.
Rich nations have made bilateral deals with manufacturers to vaccinate entire populations, sometimes several times over.
We need a vaccine for these populations because the vulnerable populations sits within these ethnic minorities.”
In general, there can be no doubt that nomadic populations always remained far sparser than agricultural populations.
Over long periods of time, genetic variation is more easily sustained in large populations than in small populations.
The difference between the two populations, called Populations I and II, was a critical clue to the evolution of galaxies.
In fact these governments committed another and quite distinct transgression against their black populations; they failed to make reparation to those populations.
Some small isolated populations of asexual species often have little genetic variation among individuals, whereas large sexual populations often have great variation.
Scientists estimate than an average species consists of 220 genetically distinct populations, suggesting that there may be more than 2 billion such populations globally.
Because small populations are so much more at risk than large ones, individuals of species that can readily disperse can rescue local populations on the verge of extinction.
Indigenous populations within a broad band known as the tropics (the regions falling in latitude between the Tropics of Cancer and Capricorn) have darker skin colours than indigenous populations outside of these regions.
A continuum exists from closed populations that are geographically isolated from, and lack exchange with, other populations of the same species to open populations that show varying degrees of connectedness.
The geographic separation of populations derived from common ancestors may continue long enough so that the populations become completely differentiated species before ever regaining sympatry and the opportunity to interbreed.
The populations in poor environments, characterized by high rates of infectious disease and poor nutrition, have higher death rates than populations in good environments at all ages, yet there is no positive evidence that disadvantaged populations experience a higher rate of aging.
Natural selection, therefore, continually works to reduce genetic variation within populations, but populations risk extinction without the genetic variation that allows populations to respond evolutionarily to changes in the physical environment, diseases, predators, and competitors.
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