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Ecology Part II

Population Growth. How Fast Do Populations Grow?. Types of Growth. linear growth ? straight line growth, for every unit increase on the x axis, there is an equal increase in the value on the y axis. In nature, populations do not grow in this manner.. Types of Growth. exponential growth ? occurs in populations where the population grows at an increasing rate. Populations in nature may grow exponentially when organisms occupy a new environment and limiting factors have almost no affect on them..

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Ecology Part II

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    1. Ecology (Part II)

    2. Population Growth How Fast Do Populations Grow?

    3. Types of Growth linear growth – straight line growth, for every unit increase on the x axis, there is an equal increase in the value on the y axis. In nature, populations do not grow in this manner.

    4. Types of Growth exponential growth – occurs in populations where the population grows at an increasing rate. Populations in nature may grow exponentially when organisms occupy a new environment and limiting factors have almost no affect on them.

    18. However… …no population can continue to grow exponentially indefinitely.

    19. There will always be limiting factors. Availability of food

    20. There will always be limiting factors. Availability of food Disease

    21. There will always be limiting factors. Availability of food Disease Predators

    22. There will always be limiting factors. Availability of food Disease Predators Lack of space

    23. Types of Growth logistic growth – an “S” shaped growth curve, where the population eventually levels off at the carrying capacity of the environment. The population starts growing at a very fast rate but environmental limiting factors start having an effect on the rate of population growth and the rate of growth slows down until the rate of growth reaches zero. At this point the number of births in the population is equal to the number of deaths and the population is at the carrying capacity of the environment.

    24. Carrying Capacity The number of organisms of one species that an environment can support indefinitely.

    25. Logistic Growth

    26. The Effects of Environmental Factors on Population Growth

    27. Environmental Factors Predation – predators control their prey species in a predator-prey interaction. The population of the prey organisms influences the numbers of predators and the number of predator organisms affects the number of prey species.

    28. The Human Population Factors that are affecting its growth.

    29. Human Growth Rate The human population growth rate prior to 1600 was about zero. After 1600, the population started to grow at a faster rate. The growth curve is exponential and is going almost straight up at the present time.

    30. Human Growth Since 1600 The most probable cause for the tremendous increase in growth rate is a drastic decrease in the death rate without a corresponding decrease in birth rate. The decrease in death rate was primarily due to decrease in disease and healthier living conditions.

    31. Human Growth Since 1600 Populations in countries that have many young individuals increase faster than those that have the same number (percent) of individuals of all ages. Immigration and emigration have an effect on the population size of counties.

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