What is extinction and why does it happen?

Lesson 4Created by Ms. Barnes

Lesson Objectives I can identify trends in resource use.

I can describe some natural and human causes of extinction.

I can identify ways humans can work to prevent the extinction of endangered species.

Did you know…. A single house cat brought over on a

ship eliminated an entire species of bird from New Zealand island in less than a year.

Let’s Investigate!

Rain Forest Area and Human Population in EcuadorYear 1961 1971 1981 1991Rain Forest (square km) 173,000 153,00

0No data 112,000

Population (in millions) 5,162 7,035 No Data 10,782

•Study the table below. It shows the size of Ecuador’s rain forests and the size of it’s human population between 1961 – 1991.

Use your calculator to calculate the changes in rain forests for each period shown (1961-1971 and 1971-1991). Write your answer on your graphic organizer. 5 minutes

Use your calculator to calculate the changes in population size for the same periods. Also write this answer on your graphic organizer. 5 minutes

Investigation (cont.) Using the graph paper you have

attached to your graphic organizer, make two bar graphs showing the data of the rain forests and the population. This will make the information easier to read. Remember to give your graphs titles. 15 minutes

Drawing Conclusions1) Compare the two sets of data on the bar graphs.

What relationships, if any, do you observe between the growth of the human population and the amount of rain forest in Ecuador?

2) Based on the data collected, what can you infer about the size of Ecuador’s human population and the area of it’s rain forest in 1981?

3) According to the data, what do you predict the size of the rain forests in Ecuador will be in 2001 if the human population increases at the same rate as it has in the past?

Drawing Conclusions (answers)

1) As the population increases, the amount of rain forest land decreases.

2) The human population grows by about 1,873 million every decade.

3) The rain forest shrinks by about 20,000 km every decade.

Let’s Explore Extinction! With your table, read “Population Decline”

on page B50 in your book. STOP when you get to “Extinction Is Forever”. Take time to look at the pictures and their captions, discuss them with your group.

Give two reasons why populations decline. Human activity and natural events such as

floods, fires, or droughts.

Exploration (cont.) Read “Extinction Is Forever” on page

B51 with your table. STOP when you get to the end of the page. Look at the picture and its caption and discuss it with your table.

What is the biggest cause of extinction today?› Habitat destruction

Exploration (cont.) Read “Success Stories” with your table

on page B52. STOP when you get to the chapter summary. Look at the pictures and their captions and discuss them with your table.

What two birds were successfully removed from the endangered species list?› Bald Eagle and Peregrine Falcon

Lesson Summary Extinction occurs naturally, but certain

human activities result in a high rate of extinction among the world’s plants and animals. An organism is endangered or threatened when its population is so small that it is in danger of becoming extinct. People have saved some organisms from extinction.