Final answer:
Biologists assess extinction risk by examining population size, trends, and habitat loss, using life tables, mark and recapture, and allele frequency studies. Mathematical models aid in depicting changes and making predictions. A declining trend without change could lead to a species being endangered.
Step-by-step explanation:
To ascertain whether a species is at risk of extinction, biologists analyze data such as population size and trends, habitat loss, and reproductive rates. When direct data is scarce, researchers may use expert opinion or mathematical models to make predictions. If a population is found to be significantly decreasing and continues on this trend without intervention, the species might be classified as endangered or even critically endangered.
A proposed high mortality rate during a specific developmental period can be investigated using methods like mark and recapture for estimating population densities or by creating a life table to study mortality rates at various age intervals. A sudden improvement in population, such as an increase in the number of voles surviving to reproduce, allows biologists to infer factors like reduced predation or improved food availability.
Population ecologists utilize mathematical models besides direct observation for a more accurate description of population changes and to predict future changes. Understanding population dynamics is crucial for conservation biology to determine if a population is stationary, increasing, or declining. Tools like statistical analysis, life tables, and allele frequency calculations in populations help in assessing the health of the species.