Do now 03/12

If an organism reproduces at a slow rate and has few offspring in their lifetime, and raises them, what

A)Life pattern does it follow and why?

B)What survivorship curve best fits it and why?

C)What survivorship curve would be the opposite? Why?

Discuss

Is the world overpopulated?

Should we control population growth? How?

Is population growth bad?

Factors affecting population growth

Today we will…

4.5: understand the factors that affect population growth: (fertility rates and death rates) and factors that affect those rates.

Factors affecting population size

As we talked about before, there are 3 major factors that can affect population size: birth(fertility), death (mortality), and migration rates. The general equation that best represents this is:

population change= (births+ immigration)- (deaths+ emigration)

When birth rates and immigration exceed deaths and emigration, our population grows during a specific period of time.

The use of birth rate, or crude birth rate (births per 1000 people in a year)

crude death rate (deaths per 1000 in a year) allow us to clearly see how our population grows and shrinks over time.

Declining fertility rates: fewer babies The average number of children a woman has, dropped sharply, but it is not low enough to stabilize the world’s population in the near future.

Fertility number of children born to a woman throughout her lifetime.

There are 2 types of fertility rates that affect the population:

1.Replacement fertility: the number of children a couple must have in order to replace themselves (slightly higher than 2. 1 children) and maximally high at 2.5 for developing countries.

This value depends on children dying before their reproductive years, especially in developing countries. Does reaching replacement fertility level stop population growth?--> NO. There are still many future parents that are alive.

•Total fertility rate average number of children a woman will have during her reproductive years. Women today have half as many children as they did back in the 70’s. Developed countries have a lower TFR compared to newly developing countries.

Total fertility rates

Quick check

1. What are the three major factors that affect population size?

2. What are crude birth and death rates?

3. Why doesn’t reaching replacement fertility level stop population growth?

Factors affecting birth and fertility rates

The population has grown mostly due to a decrease in crude death rates

These have decreased because of increased food supplies and Better nutrition/sanitation and improved medical care.

More people started living longer because of access to medicine and better nutrition. Less infants died. Better water supplies prevented the spread of diseases. Life expectancy and infant mortality rate can tell us the overall health of people in a country.

77 yearsLife expectancy 47 years

1900

2000

Married women working outside the home

8%81%

High school graduates

15%83%

Homes with flush toilets

10%98%

Homes with electricity

2%99%

Living in suburbs

10%

52%

Hourly manufacturing job wage (adjusted for inflation)

$3$15

Homicides per 100,000 people

1.25.8

Stepped Art

Fig. 6-7, p. 132

Life expectancy

Life expectancy average number of years an infant can live.

The life expectancy of people in developed countries is around 78-82 years; in developing countries it has gone up, but most still have a life expectancy of less than 49 years.

Infant mortality rate

Infant mortality rate number of babies out of 1000 that die before their first birthday.

If a country has a high infant mortality rate it can tell us about their basic nutritional access and quality, and if a country has a high incidence of infectious diseases.

Things like poor access to health care for poor women during pregnancy and for their babies after birth

Drug addiction

High teenage birthrate contribute to infant mortality.

Several Factors Affect Death Rates (cont’d.)

Fig. 6-10, p. 129

Less-developed countries

World

Infa

nt

mo

rtal

ity

rate

(d

eath

s p

er 1

,000

liv

e b

irth

s)

More-developed countries

Year

Quick check

What is the main factor that has increased population growth?

What two things tell us about the health of a country?

What important factors can contribute to high infant mortality rate?

Practice 1. what are some benefits that you would have from decreasing the

mortality rate and fertility rate?

2. What is the relationship between mortality rate under 5 and women’s education? Why do you think that is? Explain. .

3. What difference does living in an urban environment make versus rural environment? How?

4. Why do you think that women in wealthier households have fewer children than those in poorer households? Explain.

5. If you were the national leader of the Philippines, what would be your next step in order to decrease mortality rates? Why?