5-2 Limits to Growth

Limiting Factors Limiting Factors Remember, primary productivity of an ecosystem can be reduced by limiting nutrients Limiting factors can determine carry capacity –Density Dependent Factors –Density Independent Factors

1. Density-Dependant Factors Limiting factors that depend on population size Density-dependent factors become limiting only when population density reaches a certain level Does not affect small, scattered populations

1a. Competition Occurs when populations become crowded When 2 species compete for same resource, they are under pressure to change –Over time, evolve to occupy diff. niches

1b. Predation Populations in nature are controlled by predation –Known as predator-prey relationship

Isle Royale in Lake Superior

1c & 1d Parasitism & Disease Parasites are similar to predators – weaken and kill hosts Large populations can be under stress making them more susceptible to diseases More members = easier to pass “things” around

3. Density-Independent Factors Factors that affect populations regardless of their size Examples: –Unusual weather (Draught, Hurricanes) –Season cycles –Human activities (damming rivers, forest cutting)

5-3 Human Population Growth Like the populations of many other living organisms, the size of the human population tends to increase with time. For most of human existence, the population grew slowly Until fairly recently, only half the children in the world survived to adulthood.

What caused human populations to suddenly grow rapidly? Agriculture Industry/Medicine

About 500 years ago, the human population began growing more rapidly because of agriculture and industry. With these advances, the human population experienced exponential growth

Patterns of Population Growth English economist Thomas Malthus observed that human populations were growing rapidly. Malthus predicted that such growth would not continue indefinitely. Malthus- war, famine, and disease would limit human population growth.

Demographic Transition The scientific study of human populations is called demographydemography Demographic transition, a dramatic change in birth and death rates.Demographic transition Ex: U.S., Japan, Europe

What are the 4 density- dependent limiting factors? Predation Disease Competition Parasitism

What are examples density independent limiting factors? Storms Natural Disasters Human activity

What caused the human population to grow rapidly? Agriculture Industry Medicine