Every living thing on Earth can be studied using population biology.
In this lesson, you’ll learn about population biology and discover the components of a population that are measured by researchers in this field of study.
Imagine yourself outside on a sunny day. Then, it turns eerily overcast. When you look up, you see that what is blocking the sun is a huge flock of birds. In America, this used to occur often from a species of bird called passenger pigeons. However, in 1914, the last known passenger pigeon, named Martha, died at the Cincinnati Zoo.
The causes for the decline of these once plentiful birds included over-hunting and the unique characteristics of their population. Perhaps if the modern field of population biology were around then to study these birds, they may be around for us to enjoy today.Population biology is a subset study within ecology that evaluates factors that affect populations. A population is defined as a group of the same species living in a similar geographical area.
All life can be studied within this field, from mountain gorillas in Africa to passenger pigeons in North America. This lesson will focus on general factors or components of a population that biologists focus on when evaluating populations.
Research ; Science
The field of population biology came about too late to save the passenger pigeon, but is now a common field of study and researched all over the world. When a population biologist begins to evaluate a population of species, they use many tools to help them gather information. Detailed notes are taken while observing the animals, and every component of the population are carefully measured. Conditions of the population and their habitat are imitated in laboratories to test hypotheses scientists may have. Mathematical formulas and models are constructed based on the experiments and observations and then used to make predictions.
Basically, the researchers need to look at factors that affect the population. Let’s look at some of the general factors they would consider.
Demographic and Migratory Factors
One such factor studied by population biologists is the characteristics of a population. The characteristics of a population would include migration in and out of areas, density of the population, and demography. Demography is the study of the decline or increase of populations. A species on the decline may be near extinction, like the polar bear.
A species increasing rapidly could mean it’s invasive, like a beetle eating crops or a weed that strangles out native plants. The ratio of birth to death rate determines if a species will rebound, be lost forever, or become invasive.One demographic theory of why the passenger pigeons quickly declined centers on how they reproduced in conjunction to how they were hunted. Females lay only one egg per year, which is a low birth rate, and in addition, the birds experienced a high death rate due to over-hunting. Knowing the demography of a species, including things like these specific factors, is a very important characteristic to consider when studying populations.Two other characteristics to consider that also led to the decline of passenger pigeons are their migrations and their density. As the birds moved out of one area and moved into another, there was no safe place for the birds.
They were left with no sanctuary or reprieve from hunting. As they migrated, they would form flocks in the millions and their nesting sites within the forest were so dense it was referred to as living wind.The strategy for survival for these birds was safety in numbers, or having a high density population. Their survival from becoming a snack was to look intimidating, similar to large schools of fish looking like one big fish. When their numbers declined, they could no longer sustain the high density of their flocks, and this led to an even faster decline and eventual extinction. Knowing the characteristics of populations helps population biologists understand how populations survive and thrive.
Abiotic ; Biotic Factors
There are countless factors involved in studying populations of organisms.
Scientists categorize some of these factors into groupings, such as abiotic (or all non-living factors) and biotic (or all living factors). Organisms need nutrients, water, shelter, sunlight, and air, which are abiotic factors. If a population doesn’t have access to abiotic factors, it could mean their demise. Every population is in a fight for access to these factors. This competition between species can mean the growth of one and the decline of another. Thus, population biology overlaps with many different disciplines in order to understand all abiotic factors that affect the population being studied.However, biotic factors are just as important as abiotic factors in understanding the biology of a population.
All organisms depend on other organisms to survive, which are the biotic factors. Every organism is either a predator or a prey, or both. When understanding the biology of a population, it’s important to consider where and how that population fits into the larger ecology. Whether it’s the pressure of not having enough to eat or having the pressure of being killed too often, these biotic factors will be the difference to whether a species is increasing or decreasing.
In this lesson, you learned that population biology is a modern scientific field that studies the many factors that affect populations of species. The research tools used to study populations include observation, experimentation, and modeling of populations. Many factors are considered when judging the health of populations, such as demographic, migratory, abiotic, and biotic factors.