# Chapter 5 Section 1 How Populations Grow ## How Populations Grow

• List the characteristics used to describe a population • Identify factors that affect population size • Differentiate between exponential and logistic growth

### Introduction 5-1 Activity December 2, 2013

• • • Write these questions and your answers on a sheet of paper.

How many people are in this classroom?

(include me because I am a person)

What is the room’s area?

(there are 39.37 inches per meter)(area is length x width)

How many people are there in the room per square meter?

(divide the number of people by the room’s area)

• Population density = # of individuals/unit area Suppose there are 150 bullfrogs living in a pond that covers an area of 3 square kilometers. What is the density of the bullfrog population?

List the characteristics used to describe a population.

• Three important characteristics of a population are its geographic distribution, density, growth rate, and population age structure.

– Density – the number of individuals per unit area. This can vary greatly depending on the species and its ecosystem.

– Geographic distribution – also called the range, the area inhabited by a population. This can vary greatly.

List the characteristics used to describe a population - continued – Growth rate – the rate at which the size of a population changes – Population age structure – the age distribution of the individuals in that population

Population growth – Three factors can affect population size: - The number of births (if you have more births than deaths the population size grows) - The number of deaths (if you have more deaths than births the population size shrinks) - The number of individuals that enter or leave a population - Immigration is the movement of individuals into an area - Emigration is the movement of individuals out of an area

Differentiate between exponential and logistic growth.

• • •

Logistic Growth

This occurs when a population slows or stops following a period of exponential growth As resources become less available, the growth of a population slows or stops.

This ususally appears as a “S-shaped” curve on a line graph.

• • •

Exponential Growth

This occurs when a population grows at a constant rate Under ideal conditions with unlimited resources, a population will grow exponentially.

This usually appears as a “J shaped” curve on a line graph.

### Post Notes Assignment

• • Write questions numbered 1-6 on page 123 and answer them.

Then write the definitions for the vocabulary terms found only in section 1 1. population density 2. immigration 3. emigration 4. exponential growth 5. logistic growth 6. carrying capacity