Wake Up Work #2 • What are the 6 criteria that need to be followed in order for an organism to be considered living?
Spanish Flu Epidemic of 1918 • The influenza pandemic of 1918-1919 killed more people than World War I (WWI), at somewhere between 20 and 40 million people. • It has been cited as the most devastating epidemic in recorded world history. • The flu was most deadly for people ages 20 to 40 • It is thought to have originated in China in a rare genetic shift of the influenza virus
Population Density • Population – group of organisms of the same species living together • Population Density – the number of individuals of that species living in a defined space • This number can vary tremendously depending on the species and its ecosystem.
Low Population Density High Population Density
Population Growth • Birth • Immigration • Individuals moving IN • Death • Emigration • Individuals moving OUT Increase (population getting bigger/higher density) Decrease (population getting smaller/lower density)
Types of Population Growth • Exponential Growth • Population continues to grow WITHOUT LIMIT • Example: Human population (this is rare in nature) • Starts off by slowly increasing • Under ideal conditions with unlimited resources, a population will grow this way
Types of Population Growth • Logistic Growth • The population grows fast at first, then slows, then levels off at a stable population size • Most natural populations follow this pattern (fish, trees, rabbits, etc.) • As the population gets larger, more individuals are competing for limited amount of resources (food, habitat, mates) • The “leveling off” point is called the carrying capacity—the largest number of individuals (maximum population) that a given environment can support
Limiting Factors • A limiting factor is something that limits the size of a population. • Anything that could cause the population size to change (Such as; birth, death, immigration, emigration) • Disease causes death: decrease in population • More food causes immigration: increase population • Humans cut down a forest/individuals emigrate: decrease population
Limiting Factors • Limiting Factors can be biotic/living or abiotic/non-living • Biotic Factors • Food, disease, humans, birds, trees, mushrooms, bacteria • Abiotic • Water, natural disaster, climate, temperature, precipitation, humidity, wind, soil, sunlight
Limiting Factors • Limiting factors can be density-dependent or density-independent.
Density-Dependent Limiting Factors • Density-Dependent Limiting Factors: • Impacts larger, denser populations more than smaller populations…usually related to competition. • These may not limit the population at all until the population reaches a certain size • Examples: • Food • Disease • Shelter
Density-Independent Limiting Factors • Density-Independent Limiting Factors • Impact populations regardless of size. • Examples: • Weather • Natural Disasters • Human Impacts
Stable Ecosystem • A stable ecosystem must remain relatively constant, with predictable changes.
Practice • Page. 8, concept map on Describing Populations • Pages 9-11 • https://www.youtube.com/watch?v=H6zg3nWXeP4