what are two ways a population may decrease in number? Explain the difference between direct and indirect observation in regard to determining population size.
Please help!!!
Thank you!!
http://en.wikipedia.org/wiki/Demography
thank you!! it helped me alot :)
You're very welcome. :-)
if 200mL of water were used instead of 100mL,how many grams of the compound would dissolve at 40c
Two ways a population may decrease in number are through mortality (death) and emigration (the movement of individuals out of the population).
Mortality can occur due to various factors such as predation, disease, competition, or environmental changes. These factors can lead to a decrease in the survival rate, causing a decline in population numbers. Emigration, on the other hand, occurs when individuals leave the population to establish new habitats or seek better resources in other locations. This migration can reduce the population size as individuals are no longer counted within the original population.
To determine population size, scientists use both direct and indirect observation methods.
Direct observation involves physically counting the individuals in a population. This method is feasible when the population is relatively small and individuals can be easily seen and counted. For example, scientists may conduct surveys and field observations to directly count birds in a forest or fish in a lake. While direct observation provides an accurate count, it can be impractical or impossible for populations that are large, widely dispersed, or difficult to access.
Indirect observation methods are used when direct counting is not feasible. These methods involve estimating the population size based on observations or data that indirectly relate to the population. For example, scientists can use capture-recapture techniques, where a subset of individuals is captured, marked, released, and then recaptured later. By comparing the number of marked individuals to the total number captured in subsequent samplings, scientists can estimate population size. Other indirect methods include using statistical models, satellite imagery, or environmental DNA analysis.
In summary, direct observation involves physically counting individuals, while indirect observation methods rely on estimation and inference techniques to determine population size. The choice of method depends on the characteristics of the population and the available resources and technologies.