Populations
Overview
Put a few yeast cells in sugar solution and come back in a week: where there were dozens, there are now millions, and then, just as suddenly, the numbers crash. Almost every population, from bacteria to buffalo, follows the same S-shaped story, racing upward and then hitting the limits of its world.
In this lesson you will define population, community and ecosystem, name the factors that drive numbers up and down, and read the four phases of the sigmoid growth curve. You will learn to explain each phase in terms of food, competition, predation and disease, the same limiting factors that decide how many of any species a habitat can hold.
Objectives
- Describe a population as a group of organisms of one species, living in the same area, at the same time
- Describe a community as all of the populations of different species in an ecosystem
- Describe an ecosystem as a unit containing the community of organisms and their environment, interacting together
- Identify and state the factors affecting the rate of population growth for a population of an organism, limited to food supply, competition, predation and disease
- Identify the lag, exponential (log), stationary and death phases in the sigmoid curve of population growth for a population growing in an environment with limited resources
- Interpret graphs and diagrams of population growth
- [Supplement] Explain the factors that lead to each phase in the sigmoid curve of population growth, making reference, where appropriate, to the role of limiting factors
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Mind map
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Lesson Note
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Lesson Evaluation
Congratulations on completing the lesson on Populations. Now that youve explored the key concepts and ideas, its time to put your knowledge to the test. This section offers a variety of practice questions designed to reinforce your understanding and help you gauge your grasp of the material.
You will encounter a mix of question types, including multiple-choice questions, short answer questions, and essay questions. Each question is thoughtfully crafted to assess different aspects of your knowledge and critical thinking skills.
Use this evaluation section as an opportunity to reinforce your understanding of the topic and to identify any areas where you may need additional study. Don't be discouraged by any challenges you encounter; instead, view them as opportunities for growth and improvement.
- A population is best described as: A. all the living things in an area B. a group of one species in the same area at the same time C. organisms plus their environment D. all the consumers in a food web Answer: B
- Which is NOT a factor affecting the rate of population growth? A. food supply B. predation C. disease D. the colour of the soil Answer: D
- In the sigmoid curve, the phase of most rapid growth is the: A. lag phase B. exponential phase C. stationary phase D. death phase Answer: B
- During the stationary phase of population growth: A. there are no births B. birth rate equals death rate C. death rate is zero D. the population doubles each hour Answer: B
- An ecosystem is: A. one species in an area B. all populations of different species C. a community plus its non-living environment D. only the producers Answer: C
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