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Bell ringer: What is a population? How do populations grow ?

A group of organisms of the same species . Reproduction (sexual or asexual). Objective: Identify and understand the trends and limiting factors that affect growth within an ecosystem. Bell ringer: What is a population? How do populations grow ?. 2 Kinds of Population Growth.

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Bell ringer: What is a population? How do populations grow ?

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  1. A group of organisms of the same species. Reproduction (sexual or asexual) Objective: Identify and understand the trends and limiting factors that affect growth within an ecosystem. Bell ringer:What is a population?How do populations grow?

  2. 2 Kinds of Population Growth Exponential Growth Logistic Growth Occurs when individuals reproduce at a constant rate until a limit is reached, when growth of the population stops. • Occurs when individuals in a population reproduce at a constant rate, and the population keeps growing and growing.

  3. Exponential Growth unlimited • Occurs under conditions with resources. • The following is a real life example of exponential growth: ideal

  4. Chat Chum Questions • How many wild rabbits were originally brought in from England? • What conditions allowed the rabbit population to reproduce? • Look at the graph. Describe in words what happens to the rabbit population over 0-15 weeks. • Based on the graph, describe in words what happens to the rabbit population over 15-30 weeks. • What biotic and abiotic factors would be necessary to stop the growth of the rabbit population? • What do you think would happen to the numbers of the rabbit population in this case?

  5. Limiting Factors • Many factors can limit population size and stop populations from growing exponentially. These factors are called limiting factors. • Examples of limiting factors: • Density Dependent factors (depend on # of organisms): • Competition (with other organisms for food, water, sunlight, space) • Predation • Parasitism • Disease • Density Independent factors (don’t depend of # of organisms): • Unusual weather/ natural disasters • Seasonal cycles • Certain human activities

  6. IN REALITY, most populations are limited by these factors, and only grow exponentially until they reach the ecosystem’s carrying capacity. • Carrying capacity is defined as: The number of organisms of one species that an environment can support indefinitely.

  7. Logistic Growth • As populations reach carrying capacity, its growth slows/stops.

  8. Chat Chum Questions • In this sample population, how many hours of growth does it take to reach the carrying capacity? • Describe in words what happens to the number of organisms from 0-12 hours. • Describe in words what happens to the number of organisms from 12-30 hours. • Describe in words what happens to the number of organisms from 30-42 hours. • Does a population stay at its EXACT carrying capacity? Explain why.

  9. Exit Questions • The Human Population • What type of growth represents the human population? • Why do you think this is? • Has the Earth reached its carrying capacity? • Will we ever run out of room? Where will people go once we run out of room?

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