Chapter 20 Lesson 1

P718-722

PEOPLE AND THEIR ENVIRONMENTS

Population and Carrying Capacity For scientist, a population is all the

members of a species living in a given area.

You are a population of humans! (hurray) There are also birds and trees that make

up separate populations in your area.

The Human Population

Earth was once home to relatively few humans

Today, about 6.7 billion people live on Earth. The greatest increase in human population occurred during the last few centuries

Population Trends

A sudden rise in human population that has happened in recent history is called a population explosion.

Look at the chart

What caused this sharp increase?• Improved health care• Clean water• Technological advancements* In 1 hour about 15000 babies will be born

Population Limits

All living things have certain needs. What do humans need?

Food, clothing, clean water, shelter Where do all the materials we use for

products come from? Nature!

Does Earth have enough resources to support an unlimited number of humans?

Population Limits

Earth has limited resources It cannot support a population of any species

in a given environment beyond its carrying capacity

Carrying capacity is the largest number of individuals of a given species that earth’s resources can support and maintain for a long time.

If the human population continues to grow beyond Earth’s carrying capacity, eventually Earth’s resources will run out.

Impact of Daily Actions

As of 2012, the human population is 7.046 billion Everyone is using resources Think, everyday people should be drinking

2-3 liters of liquids a day That’s 14,000,000,000L of liquid consumed

in a day used just for drinking (if everyone got the necessary amount)

Consuming Resources

Like most people, I hope you are taking a shower everyday. What resources are needed to make that happen? The metals in the pipes are obtained through mining, which

causes pollution and destroys habitats Gasoline is needed to transport those metals, which releases

pollution into the atmosphere You probably use a cotton towel. Fertilizers often used to grow

crops run off into water and affect overall water quality Think about all the activities you do in a week and the

resources needed to make them possible. Then, multiply that by 7 billion. This why using resources wisely, even at a personal level, can

help Earth

Positive and Negative Impacts Not all human activities have a negative

impact on the environment. What are some positive and negative

impacts of humans?

Check Out GapMinder

Gapminder.org Food Supply (Y-axis) Population (x) GDP (size)