Populations

A group of members of a certain species (i.e., can interbreed and reproduce fertile offspring) that living in the same area. This is different from community, which describes multiple populations/species living in the same area.

“Whoa that is a huge population of Homo sapiens hanging out at Alderwood Mall on a Saturday”

Populations

• Things we examine in populations:– Population Growth (graphs)– Population Density– Limiting Factors– Carrying Capacity

Population Density

How many organisms of one population occupy one area.

Population = # Members of Population Density Area (square miles)

“Whoa, the population density of Homo sapiens in Mill Creek is far less than that of the population density of Homo sapiens in China”

Try it…• The United States has an area of 3,539,225

square miles and a population of 298,444,215. Calculate the population density.

• China has an area of 3,705,000 square miles and a population of 1,357,000,000. Calculate the population density.

• Calculate the population density of a town that is 4.7 square miles and has a population of 18,828.

Limiting Factors

Carrying CapacityThe maximum population size an environment can sustain indefinitely, given the food, habitat, water, and other necessities available in the environment.

Observe the 2 graphs showing different populations carrying capacity. What is the difference? What does this tell you about carrying capacities?

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Discuss:What conditions are necessary for populations to increase rapidly?

Shifting Gears…• Think back to food

webs and food chains. What do you recall about this?

• If you traced a radioactive carbon atom from the primary producer level, could it end up in the eagle? Why or why not?

Observe both diagrams.What do they have in common?

The concepts of bioaccumulation and/or toxic magnification is shown in the images. Make a statement that explains this phenomenon.

How might the cycle of this matter affect the health of an ecosystem?

One last topic…

• How does an ecosystem “begin”? Think about what it means to be an ecosystem and what it takes to get there.

• Discuss and share out in 3 minutes.

Ecological Succession• What is it?

• Ecological Succession– The process by which the structure of a biological

community evolves over time– Primary Succession

• Occurs in essentially lifeless areas. Soil is incapable of sustaining life.

• Follows lava flows, newly formed sand dunes, or rocks left from a retreating glacier

– Secondary Succession• Occurs in areas where a community that previously existed has

been removed• Caused by smaller-scale disturbances that do not eliminate

all life and nutrients from the environment. Soil still in tact.

Animation

Fri 5/29

• The Mystery of Easter Island

Mystery of Easter Island