Population Biology

A population is a group of individuals of the same species living close enough to reproduce with each other. 

Studying populations has a lot of practical applications such as

• • managing natural resources such as fish populations
  • conservation of rare species
  • controlling pest populations ( cockroaches, rats, viruses)
  • planning for human population needs. 

Population Descriptions

We have to be able to describe populations before we try to manage them.  Here are some important characteristics that scientists  measure and quantify. 

Population Size (N)  and Density 

The number of individuals in a population is the population size, and it is symbolized with the letter N.  But just as important as  the population size is the Density.  As you can see from the picture, that density tells us the number of individuals in a certain area- how crowded are they.  

Population Age Structure

Another important description is the age structure of a population. This is the percentage of the population that is in each age category.    If you know something about the biology of the species, such as when they reach reproductive age, when they begin to age, you can make predictions about future population size. 

Population Growth

Population size can increase or decrease  and Knowing and predicting patterns of population growth are very important.  Here are some examples 

control insects, pests, viruses	Conservation	manage crops and livestock	predict human population needs

When population size is small, the growth rate is very fast and you will see exponential growth curve. The slope of the line, indicates how fast the population is changing. 

As population size increases, the individuals compete with each other for resources and growth slows down. The population size will level out at the  number of individuals that the environment can ''carry'' = the carrying capacity. 

Use this information to answer the quiz questions. You will have 3 attempts at the quiz.