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BELL RINGER 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. 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 Death Population will grow # of Birth Population will shrink < # of Death # of Birth = # of Death 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 Logistic Growth Linear Growth: A steady growth over time
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.