Exponential Growth - Schurz High School

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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

POPULATION DYNAMICS

Objectives:

Compare and contrast exponential, logistic and linear growth.

PRINCIPLES OF POPULATION 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)

POPULATION GROWTH

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)

PATTERNS OF POPULATION GROWTH

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.