1. Chapter.1-Loss of biodiversity:
Biodiversity: The number and variety of species that live in an area. A species that is extinct is gone forever.
Extinction of species is a natural process and mass extinctions also have occurred throughout Earth’s history. For example, Tasmanian tiger, native to an island near Australia, was declared extinct in 1986.
Extinction of species may cause problems for human populations in future.

2. “The tragedy of the commons”
Hardin observed that when land was held in common, people tended to graze as many animals as possible.
Overgrazing led to the destruction of the land resources.
When commons were replaced by enclosed fields owned by individuals, people tended to graze only the few number of animals that the land could support.

3. The law of supply and demand:
The law of supply and demand states that the greater the demand for a limited supply of something, the more that thing is worth.
Cost and benefits: A cost benefit analysis balances the cost of the action against the benefits one expects from it.
Risk Assessment: To come up with the effective solution to an environmental problem, the public must perceive the risk accurately.

4. Developed and Developing Countries:
Developed countries have higher average incomes, slower population growth, diverse industrial economies, stronger social support system. Ex. U.S.A, Japan, Canada and countries of Western Europe.
Developing Countries have lower average incomes, simple and agriculture-based economies, and rapid population growth.
Developed and Developing countries have different consumption patterns, which affect the environment in different ways.

5. Ecological footprint:
An ecological footprint shows the productive area of Earth needed to support one person in a particular country.
An ecological footprint is a calculation of the amount of land and resources needed to support one person from a particular country.
The ecological footprint of a person in a developed country is, on average, four times as large as the footprint of a person in a developing country.

6. A Sustainable World
Sustainability is the condition in which human needs are met in such a way that a human population can survive indefinitely
In a sustainable world, technology advances and human civilizations continue to be productive but the present world is far from sustainable.
Nevertheless, our environmental problems are significant and require careful attention and action.
Achieving sustainable world requires everyone’s participation.