POPULATIONS

1. S curve = Logistic growth Resource availability will cause the population to level off over time When we look at how populations grow, we can observe 2 types of growth curves: 1. S shaped curve- Logistic growth 2. J shaped curve-Exponential growth

2. J curve = Exponential growth “J” Shape Happens during ideal conditions Plenty of food, shelter etc. Unlimited resources No limiting factors POPULATION EXPLOSION

Horizontal line where growth of the population has leveled off is the CARRYING CAPACITY Carrying Capacity = The number of individuals in a population that an environment can support over a long period of time As growth continues, the environment's resources are shared by more and more individuals. Eventually, some resources are in short supply and become a limiting factor Determine an environment’s carry capacity – things that prevent a population from growing any larger

In the graph below, what factors would cause the growth rate to decrease or level off?

Limiting Factor = a factor that causes the growth of a population to decrease. 1.Density dependent: (biotic) – Competition: may use same food, or shelter. – Predation : predator–prey curve (pop. control) – Parasitism and disease 2.Density independent (abiotic): – Natural disasters – Human disturbances (construction…) – Weather

How does the difference in water temperature affect the growth rate of the three species of fish depicted in the graph?

DISCUSSION. DISCUSSION. QUESTION: Has the Earth reached its carrying capacity for Humans? Based on what you have learned about carrying capacity, answer the following questions. 1.Some scientists believe we have passes Earth’s Carrying capacity for humans. Some believe we may reach it when the human population reaches 12 billion. 2. In your opinion, has the earth passed its carrying capacity? Justify your answer. - Give 3 reasons to support each argument. 3.What would limit humans from increasing its population indefinitely?

EXPONENTIAL & LOGISTIC GROWTH CURVES WORKSHEET A B C D

PREDATOR – PREY CURVE WORKSHEET

HUMAN POPULATION GROWTH AND OTHER THREATS TO BIODIVERSITY

History of the Human Population Scientists believe that the first modern humans evolved on Earth approximately 100,000 years ago. Hunter-gatherers – humans that roamed the forests/plains and lived in small tribes or families. Predation, Starvation, and disease prevented them from living long, 35 years old was considered very old. 10,000-20,000 years ago, people began to establish settlements and store their food which reduced the threats of starvation.

Increases in Growth Rate - This shift from harvesting wild food sources to producing food through farming and herding is known as agricultural revolution. - Farming provided a steady and increased food supply which led to an increase in human population.

Decline in Growth Rate A sharp decline occurred during the mid-14th century. Result of bubonic plague or Black death that struck Asia and Europe. Worldwide outbreaks of malaria, smallpox, yellow fever, and cholera claimed hundreds of thousands of lives. – Irish Potato Famine- resulted in more than 1 million deaths – Famine in China ( )- resulted in more than 9 million deaths – War- have a destructive effect on human population

B. Human Populations Population growth depends on rates of birth, death, immigration, and emigration. 1.Emigration- movement of people OUT of a country 2.Immigration- movement of people INTO a country 3.Birth rate-expressed as # of births per 1000 per year 4.Death rate-expressed as # of deaths per 1000 per year Growth = B D I E

The human population has been growing exponentially for centuries. The most significant additions to human populations are due to births. Total fertility rate (TFR): the average number of children a woman has during her reproductive years. Replacement-level fertility: the number of children a couple must bear to replace themselves.

C. Factors Influencing Total Fertility Rates: availability of birth control and abortions. Education level of women. populations religious beliefs, customs, culture and traditions. demand for children in the work force. existence of retirement systems- pensions. Marriage age. Urbanization.

Human Populations- U.S. The baby bust that followed the baby boom was largely due to delayed marriage, contraception, and abortion.

Human Population Growth Population growth is considerably higher because the death rate has dropped. People live longer & there is lower infant mortality. Due to: 1.Industrial Revolution- improved standards of living. 2.Clean water sources. 3.Better sanitation. 4.Dependable food supplies. 5.Better health care.

D. Population Age Structure A population’s growth is dependent upon the number of people in young, middle, and older age groups. # of people younger than age 15 = the major factor determining a country’s population growth. Populations with a large proportion of its people in the pre-reproductive ages 1-14 have a large potential for rapid population growth.

Growth Momentum

Age- Structure Pyramids (click picture for pyramid data on all countries)

In 2006, the % of people under age 15 (pre-reproductive age) was… 17% in developed countries 32% in developing countries

E. Reading Population Histograms 1- Birth rate exceeds the death rate. Population is getting larger. Pyramid shaped histogram. EX: Kenya, Nigeria and Saudi Arabia.

2- Birth rate almost equals death rate. The population is not getting any larger or is growing very slowly. Histogram shape is straighter and more box-like until about age EX. US, Australia & Canada has slow growth. Denmark, Austria and Italy has stable growth.

3- When the birth rate is smaller than the death rate. The pyramid bulges near the top or is inverted. EX: Germany, Bulgaria & Hungary

HUMAN HISTOGRAMS Q: Which is the largest age cohort? Q: What do you think this says about population change? Q: What do you think would happen if the pre- reproductive cohort was larger than the cohorts above it?

HUMAN HISTOGRAM LAB

Over-population leads to: Resource depletion Resource degradation Pollution Loss of biodiversity

Impact of over population