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Populations

Explore the dynamics of populations, from growth rates to limiting factors, and how human activities disrupt ecological balance. Learn about carrying capacity, predator-prey relationships, and demographic trends worldwide.

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Populations

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  1. Populations

  2. Populations • Population- A group of organisms of the same species that live in a particular area. • Three important characteristics of a population are its geographic distribution, density, and growth rate.

  3. POPULATIONS • Population Growth- the change in the size of a population with time. • Population Density- is the number of individuals per unit area. • Geographic Density is how the population is distributed.

  4. POPULATION SIZE • Three factors can affect population size. • Number of births • Number of deaths • Number of organisms that enter or exit the population

  5. POPULATION SIZE • Immigration- The movement of organisms into a population. • Emigration- The movement of organisms out of a population.

  6. POPULATION GROWTH • Exponential growth- occurs when the individuals in a population reproduce at an ever increasing rate.

  7. POPULATION GROWTH • Linear Growth-increase of a population at a constant rate.

  8. Maintaining a Balance • For a population to survive, a balance must exist between producers/consumers, predator/prey, growth and decay, water use and rainfall…etc.

  9. Limiting Factors • Limiting Factors- Any condition of the environment that limits the size of a population. • Some can happen naturally and some are caused by humans. • Ex: Food, water, shelter and space availability, Predation, Climate, Disease, Pollution, Competition,….

  10. HUMAN IMPACT • Humans have disrupted this balance through…. • Building of roads, industry, homes • Pollution • Hunting/poaching • Global Warming, Excess CO2

  11. Carrying Capacity • The number of organisms a given ecosystem can support. • S-shaped curve

  12. Because ecosystems change, carrying capacity is difficult to predict and calculate However, islands are the ideal place to study (clear boundaries) Predicting Carrying Capacity

  13. Rabbits in Australia • no rabbits in native ecosystems of Australia • introduced in 1859 • number increased rapidly plenty of vegetation; no predators; no competition • disease and starvation caused the rabbit pop. to crash • over time, vegetation recovered and rabbit pop. increased again • continues to increase and decrease, but less dramatically

  14. Rabbits reduced Phillip Island to a wasteland.Photos: Department of the Environment and Heritage Recovery was spectacular after the rabbits were eradicatedPhotos: Department of the Environment and Heritage

  15. Reindeer near Alaska • 25 reindeer introduced to one of Pribilof Islands near Alaska in 1911 • by 1938, herd had grown to 2,000 • reindeer ate mostly lichens, which grow back very slowly • by 1950, only 8 reindeer alive on the island

  16. Predator/Prey • This is an example of a predator/prey relationship. • As one increases the other will as a result decrease.….which in turns causes the other to decrease. • A normal cycle

  17. Two Types of Population Regulation • Cause of death may be density dependent or density independent

  18. Density Dependent Factors • Density Dependent Factors have an increasing effect as populations increases • deaths are caused due to density (population too many)

  19. Density Dependent Factors • Competition, • Predation • Parasitism • Disease • Crowding

  20. Population is growing rapidly and there are limited resources, predation, or disease

  21. Density Independent Factors • Density Independent Factors are factors that affect a population or cause death regardless of density. • Severe weather, natural disasters, etc. cause death that did not result due to density.

  22. DEMOGRAPHY • DEMOGRAPHY- The study of population. • You can study charts of the age structure of a population and determine if it is growing or not.

  23. Human Population

  24. HUMAN POPULATION • Currently at 6.5 Billion People • Growing Exponentially • Industrial Revolution and Agriculture advancements are the reason for the drastic increase since the 1800’s • The population trends differ depending on Developing and Developed Countries.

  25. Developed Countries • Higher Average Incomes • Slower Population Growth • Diverse Industrial Economies • Stronger social support • Uses a large % of available resources • Ex: US, Canada, Japan, and countries of Western Europe

  26. Developing Countries • Lower Average Incomes • Simpler and agriculture-based economies • Rapid Population Growth • Uses small % of available resources • Ex: Indonesia and countries in Africa.

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