POPULATION GROWTH Optional Notes

Population Growth 1. Population: A group of organisms that all belong to the same species, can interbreed, and live in a given area. 2. Population Growth: The change in the size of a population with time. Optional Notes

Population Growth 3. Birthrate: Number of births in a population over time. A.High birthrate increase/decreasethe population B. Low birthrate increase/decrease the population Optional Notes

Population Growth 4. Death rate: Number of deaths in a population over time. A. High death rate increase/decrease the population B. Low death rate increase/decrease the population B. Low death rate increase/decrease the population Optional Notes

Population Growth 5. Immigration: Number of individuals entering a given population. 6. Emigration: Number of individuals exiting a given population. Optional Notes

Population Growth How do you calculate the size of a population? How do you calculate the size of a population? Last Population Count + Births + Immigration - Deaths - Emigration Optional Notes

Limits of the Environment on Population Size 7. Limiting Factors: Any component (part) of the environment that restrict (stop) the growth of populations. Anything in the environment that could keep a population from increasing is a limiting factor. Optional Notes

Limits of the Environment on Population Size Examples: not enough water for plants to grow in a forest, too much water for cacti to grow in a desert, not enough light for autotrophic bacteria to produce food, not enough space for the number of fish to live in a pond, not enough food for a population of birds. Limiting factors keep populations from growing out of control. Optional Notes

Limits of the Environment on Population Size 8. Carrying Capacity: The number of organisms that can be supported by the environmental resources (food, space, water, predators) in a given ecosystem. Optional Notes

Limits of the Environment on Population Size The population curve flattens out when an ecosystem is at its carrying capacity. At this point, the population is gaining and losing about equal numbers of individuals. Optional Notes

Graphing Growth Curves 9. Exponential Growth: Exponential growth occurs when the number of organisms keeps on increasing at a faster and faster rate because nothing stops the population from growing. Optional Notes

Graphing Growth Curves This in not what normally happens in most populations of organisms. This type of growth is represented on a graph by a J- shaped growth curve. Exponential Growth Game Optional Notes

Graphing Growth Curves 10. NORMAL GROWTH: Most populations go through a number of growth phases, which can be represented by a S- shaped growth curve. Maximum Population Population Logistic Growth Game Optional Notes

Graphing Growth Curves A.Initial Growth Stage: Most populations begin to grow slowly at first. B. Exponential Growth: Soon the population will begin to grow very rapidly. Optional Notes

Graphing Growth Curves C and D: Population growth begins to slow down more and more. Steady State: When the population growth remains about the same. The population may increase a little and decrease a little. Population growth is at zero because the number of organisms in the population remains the same. Optional Notes

Graphing Growth Curves Optional Notes

Graphing Growth Curves 11. Decline: A decrease in a population due to a decrease in birthrate or an increase in death rate. Optional Notes

Graphing Growth Curves 12. Extinction: A continuing decrease in the population until no more individuals are left to reproduce. Optional Notes

Graphing Growth Curves 13. Predation: Predator-Prey Relationships: If we watch populations of predators and prey over time, we almost always find changes in their numbers. These changes are important in controlling natural populations. There should always be a higher prey population compared to the predator population. Optional Notes

Graphing Growth Curves Optional Notes

Graphing Growth Curves 14.Human Population Growth Curves: Human population, like those of all other animals, tends to increase in size with time. If we examine the size of the human population over the course of history, we see that for a long time it grew slowly. Then, about 500 years ago, the world’s human population started growing exponentially. Optional Notes

Graphing Growth Curves What happened to allow for this increase in population growth? Optional Notes

Graphing Growth Curves Today, population growth in the United States and parts of Europe has slowed down. But most of the world’s people do not live in these countries. Instead, the live in China, India, and parts of Africa and Latin America- places where populations are still growing very rapidly. This population growth poses a serious threat to the Earth including: Optional Notes

Graphing Growth Curves A. Pollution in air, water and soil from use of chemicals in everyday life B. Deforestation: cutting down the forests C. Intensive Farming: Farmland can only be used for short time before nothing else will grow there. Farmers then leave that land and go to new areas to farm, causing that area to also become useless. Optional Notes