5.1How Populations Grow

Name Class______Date______

5.1How Populations Grow

Describing PopulationsResearchers study five important characteristics of a population:

______is the area in which a population lives.

______is the number of individuals per unit area.

______is how individuals are spaced out in their range.

______determines whether a population grows, shrinks, or stays the same size.

______is the number of males and females of each age in a population.

Population GrowthPopulations can grow, shrink, or stay the same size. The four factors that can affect growth rate are:

1. ______
2. ______
3. ______
4. ______

Factors that______population size include births and immigration, which is the movement of individuals into an area.

Factors that ______population size include deaths and emigration, which is the movement of individuals out of an area.

Exponential GrowthWhen conditions are ideal, the larger a population gets, the faster it grows. When a population’s numbers grow larger with each generation,______ is occurring. Ideal conditions include ______and absence of ______and ______.

Logistic Growth Resources become less available as a population grows.

______occurs when population growth slows and then stops after a period of exponential growth has occurred.

Population size stabilizes at the ______, the maximum number of individuals of a given species that an environment can support.

Exponential Growth

Logistic Growth

Concept Map

Immigration and emigration affect .

Exponential growth occurs when resources are .

Logistic growth occurs when resources are .

5.2 Limits to Growth

Limiting Factors A ______ is a factor that controls the growth of a population.

______. Others do not.

Acting separately or together, limiting factors determine an environment’s carrying capacity.

Limiting factors produce the pressures of natural selection.

Density-Dependent Limiting Factors

______operate strongly when the number of individuals per unit area reaches a certain point.

Examples include:

• ______
• ______
• ______
• ______

Density-Independent Limiting Factors Some limiting factors do not necessarily depend on population size.

______are limiting factors that affects all populations in similar ways regardless of population size and density.

Examples include ______.

Some of these factors may have more severe effects when population density is high.

Density-Dependent Limiting Factors

What happened to the number of wolves on Isle Royale between 1975 and 1985?

What happened to the moose population when the number of wolves was low?

What is the relationship between the moose and the wolves on Isle Royale?

Is the number of moose on the island a density-dependent or density-independent limiting factor for the wolf? Explain your answer.

Density-Independent Limiting Factors

5.3Human Population Growth

Historical OverviewThe size of the human population has increased over time.

For most of human existence, limiting factors such as the scarcity of food kept death rates high.

As civilization advanced, agriculture, industry, improved nutrition, sanitation, and medicine reduced death rates. Birthrates stayed high in most places. This led to exponential growth.

Today, the human population continues to ______, although the doubling time has slowed.

Patterns of Human Population Growth______ is the scientific study of human populations. Demographers try to predict how human populations will change over time.

Over the past century, population growth in developed countries slowed. As death rates dropped, birthrates dropped also. Demographers call this shift the ______. Most people live in countries that have not undergone the demographic transition.

An ______shows how many people of each gender are in each age group in a population. Demographers use such graphs to predict how a population will change. More people of reproductive age usually means faster growth.

Many factors, including disease, will affect human population growth in the twenty-first century. Current data suggest the human population will grow more slowly over the next 50 years than it did for the last 50 years.

Historical Overview

Over the last 1000 years, the size of the human population has ______.

Since the 1800s, human population growth has been ______.

The human population has increased because ______have dropped.

The combination of low death rates and high ______led to exponential growth.

______suggested that human populations are regulated by war, famine, and disease.

Factors That Affected Human Population Growth
Cause / Effect
Agriculture
Improved health care and medicine
Improved sanitation
Bubonic plague
Industrial Revolution

Patterns of Human Population Growth

Use these age structure diagrams to answer the questions below.

Which country has gone through the demographic transition? How do you know?

______

Which country do you predict will experience a slow and steady growth rate in the near future? Why?

______

Which country is most likely to grow exponentially in the near future? Why?

______

Suggest three factors that might slow population growth in Rwanda.

______