Transcript Population
Populations 1. 7 Billion –Videos 2. 7 Billion – Agree or Disagree 3. Intro to Populations - Notes http://www.youtube.com/watch?v=s c4HxPxNrZ0 https://www.youtube.com/watch?v=4B2xO vKFFz4 https://www.youtube.com/ watch?v=VcSX4ytEfcE Understanding Populations Population: all the members of a species living in the same place at the same time. 3 words to describe a population: 1. Size – (7 billion people on the planet) 2. Density – (people per square mile) 3. Dispersion – (distribution or arrangement of its individuals within a given amount of space) Even Clumped Random Density Dispersion How Does a Population Grow? Growth rate: change in the size of a population over a given period of time. Positive (+): birth rate > death rate Zero (0): birth rate = death rate Negative (-) = birth rate < death rate Change in population size = Births - Deaths How Fast Can a Population Grow? Reproductive potential: the maximum number of offspring that a given organism can produce. Examples: It would take elephants 750 years to produce 19 million descendents It would take bacteria a few days to produce 19 million descendents. What is another organism with a low reproductive rate? How Fast Can a Population Grow? High reproductive potential when individuals… Produce more offspring at a time Reproduce more often Reproduce early in life Examples: Insects – can reproduce when they are a few hours or days old Humans – reproduce after a number of years How Fast Can a Population Grow? Exponential Growth: when populations grow faster and faster Occurs when a population has: Plenty of food and space No competition or predators What Limits Population Growth? Carrying Capacity: the largest population that an environment can support in any given time What Limits Population Growth? Limiting resources: a natural resource that is consumed at the same rate at which the ecosystem produces the resource Example: Limiting Factors Food Water Sunlight (producers) Space Disease Competition Predation Two Types of Population Regulation Density Dependent Density Independent Same species close Portion of a together Disease spreads from one to the next Death occurs quickly population dies regardless of population density Example: Natural disasters (hurricane) If humans have no natural predators, how is our population controlled? Human Carrying Capacity? Current human population: approx 7.12 billion people Ranges estimated from 4-16 billion people Hard to estimate how many people this world can hold Technological innovations Medical breakthroughs http://www.census.gov/popclock/ What caused this rapid growth? What sparked our growth? Industrial Revolution (~1750) Modern medicine (20th century) Death rates DROPPED due to better care Agricultural Advances Transportation Advances Human Population Growth Population (in billions) 1 2 3 4 5 6 7 8 9 Year 1804 1927 1960 1974 1987 1999 2012 2027 2046 Years elapsed between milestones -- 123 33 14 13 12 13 16 19 Source: U.S. Census Bureau-World POPclock Projection What takes us out? Pair and Share (2 min): Humans are at the top of any food web resulting in no natural predators to keep our populations in check… 1. What are the limiting factors of the human population? 2. How are we different than other species in regards to population control? What’s our limiting factor? Disease: Bubonic Plague, AIDS, Flu, Malaria Access to food Access to clean water Competition (a.k.a. War) Event Casualties American War Deaths, all-time 600,000 India Famine (1769-70) 3,000,000 AIDS deaths in 2011 1,700,000 Influenza Epidemic (1918) 21,000,000 Indonesian Tsunami/Earthquake (2004) 230,000 Bubonic Plague (1347-51) 75,000,000 Populations Review 1. What is growth rate? 2. What is reproductive potential? 1. High reproductive potential? 2. Low reproductive potential? 3. What are the two reasons that cause a population to have exponential growth? 4. What is carrying capacity? 5. What is an example of a limiting factor? How Many People Can Live on Planet Earth? http://www.youtube.com/watch?v=d N06tLRE4WE Human population growth Water Food