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Population Ecology Chapter 19.

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Presentation on theme: "Population Ecology Chapter 19."— Presentation transcript:

1 Population Ecology Chapter 19

2 Properties of Populations
What is a population? Group of organisms that belong to the same species and live in a particular place at the same time. What classifies a group to be considered a population? Population Size -- # of individuals Population Density – how crowded is it Dispersion (clumped, even or uniform, random)

3 Also known as even dispersion.

4 Population Dynamics Populations are dynamic…meaning they change in size and composition over time. Birth Rate Death Rate (Mortality) Life Expectancy Age Structure – distribution of individuals among different ages in a population. Survivorship Curves – mortality rate data of different species tend to conform to 1 of 3 curves.

5 AGE STRUCTURE GRAPHS

6 SURVIVORSHIP CURVES Type I = Likelihood of dying is small until late in life Type II = Some species the probability of dying doesn’t change throughout life Type III = Many organisms are very likely to die when young

7 Measuring Populations (Ch. 19-2)
Demographers study population dynamics. The size of a population depends on four factors: birth, death, emigration, and immigration. 1. Emigration- movement of individuals out of a population. Immigration- movement of individuals into a population. Growth rate = birth rate – death rate

8 Population Growth Type 1
Exponential Growth…”J” shaped curve. The larger the population gets, the faster it grows.

9 Limits on Populations A limiting factor is an environmental factor that prevents or stops a population from growing. What would be some examples of limiting factors?

10 Answers Some limiting factors --- natural disasters, weather, disease, living space, competition, predation, etc.

11 Population Growth Type 2
Logistic Growth…”S” shaped curve. Builds on the exponential model but takes into account limiting factors. Carrying Capacity- number of individuals the environment can support over a long period of time.

12 Population Regulation
Density Dependent --- A factor that has an increasing affect as a population increases. Examples --- disease, competition, parasites, and food. Density Independent --- affects all populations no matter what their size or density is. Examples – temperature, floods, storms, drought, and habitat destruction.

13 Human Population Growth (Ch. 19-3)
The history…hunter-gathers (500,000 years ago). Growth of population was very slow due to small populations and a high mortality rate. Agricultural Revolution (10,000 years ago). Population began to grow fast because of increased food supply. Bubonic Plague ( )…wiped out 25% of Europe’s population. 1650…Why did mortality rates decrease? World War II

14 Population Growth Today
It took most of human history for the world’s population to reach 1 billion (Year 1800) It took 27 years for the population to grow from 3 billion to 5 billion ( ). 20% of the world’s population lives in developed countries. (includes modern, industrialized countries) 80% lives in developing countries. (poorer countries & populations growing faster.)


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