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A student grew a yeast culture on sterilized nutrient medium in a closed dish for 5 days. Each day, she took the same size sample from the dish and placed it on a special slide used for counting microorganisms. She examined the samples under a microscope and drew the following illustrations of her observations over the course of the investigation. Each dot represents 10 yeast cells.
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1. Why did the student use sterilized medium and keep the dish closed?
Sterilized medium and closed dish were used to minimize contamination.
2. During which two-day period was population growth most rapid?
From Day 2 to Day 3

Objectives:
• Compare and contrast exponential, logistic and linear growth.

A population is a group of organisms, all of the same species, that live in a specific area.
A healthy population will grow and die at a steady rate unless it runs out of food or space, or is attacked in some way by disease or predators.
Characteristics of a Population
• Geographic distribution or range (the area inhabited by a population)
• Density (the number of individuals per unit area)
• Growth rate (how slow or how fast a population grows)

Factors that Affect Population Growth
• Number of birth
• Number of death
• Number of individuals that enter or leave a population
# of Birth >
# of Birth <
# of Birth =
# of Death
# of Death
# of Death
Population will grow
Population will shrink
Population will stay the same
Immigration: The movement of individuals into an area (Causes populations to grow)
Emigration: The movement of individuals out (Exit) an area (Causes populations to shirk)

Linear
Growth
Exponential
Growth
Linear Growth: A steady growth over time
Logistic
Growth

Exponential Growth: When a population reproduces at a constant rate. Initially the population grows slowly, but as it get larger it grows at a faster rate.

Logistic Growth: When a population’s growth slows or stops following a period of exponential growth
Carrying capacity: The maximum number of organisms that a population can support.