Evolution of Populations Evolution Unit

Population What is a population? Number of Individuals of the Same Species that Live together in one area or place

Factors That Control Population Growth A population’s biotic potential is the size it would be if nothing stopped it. Why don’t populations grow indefinitely?

Factors That Control Population Growth What determines the population number of an ecosystem (or planet)? (Think in terms the basics that plants, animals and ourselves need to survive.)

Factors That Control Population Growth Populations don’t grow indefinitely because of Limiting Factors. The major limiting factors are FWSS: – Food – Water – Shelter – Space

Factors That Control Population Growth Carrying Capacity is the maximum number of individuals the environment can support. Carrying capacity is closely associated with the availability of limiting factors.

Factors That Control Population Growth Does carrying capacity for an area ever change? Why or why not? ? ? carrying capacity

Population Growth Rate Exponential “J” Curve Some populations start slow and then have a burst of growth. This is called EXPONENTIAL growth. What shape curve does it have? Time Population

Time Population Population Growth Rate Exponential “J” Curve What is the slow almost flat growth called? What is the fast almost straight up growth called? Lag Exponential A B

What is this curve called? What is this phase? B. A.

Population Growth Rate Logistic “S” Curve Some populations start slow, have a burst of growth, then level off. This is called LOGISTIC growth. What shape is the curve? Time (in days) Population

Population Growth Rate Logistic “S” Curve Logistic curves have a lag phase and an exponential phase. Where are they on this graph? Time (in days) Population A B C D

Population Growth Rate Logistic “S” Curve The almost flat, slightly up/down line is called stabilization. What letter represents stabilization on the graph? Time (in days) Population A B C D

Population Growth Rate Logistic “S” Curve What is carrying capacity? What letter represents it? Why does the population stabilize at “A”? Time (in days) Population A B C D

Population Growth Rate Logistic “S” Curve What will happen to a population if it goes over the carrying capacity? What will happen to a population if it drops under the carrying capacity? Time (in days) Population K K carrying capacity lag exponential stabilization

Population Growth Rate Logistic “S” Curve What is this? Why does it rise and fall slightly? A. C. B. D.

Natural Selection and Populations Recall Darwin’s Concepts of Natural Selection variation exists in all species organisms produce more offspring than can survive competition for limited life resources survival of the fittest (most suited to the environment) descent with modification

Natural Selection and Populations Relate variation and offspring production to the population at B and C. Describe competition when the population reaches A Time (in days) Population A B C D

Natural Selection and Populations Relate survival of the fittest with the population at D. Describe the population at D in terms of descent with modification and variation Time (in days) Population A B C D

Natural Selection and Populations Relate the five concepts of natural selection to Graph #3. Variation Numbers increase Competition Survival of the fittest Descent with modification Event C Event B Event D Event A

Human Population What kind of curve is world population growth?

Human Population Where is the lag phase? The exponential phase?

Human Population Where is the carrying capacity?

Human Population What historical event could have caused the dip at the arrow?

Human Population Consider the Black Death Plague as an environmental change. Describe the population after the Black Death (yellow arrow) in terms of variation and survival of the fittest.

Human Population Why would the industrial revolution cause a population increase? (think in terms of FWSS and carrying capacity)

Human Population Where do we go from here? Children per Woman: High 2.5 Medium 2.0 Low 1.6

Human Population What is the Earth’s carrying capacity? When will we reach it? Who will survive? ? ? ? ? ? ? ? ? ? ?

Works Cited “Big Horn Sheep”, “Seabirds”. No date. Online Image. Free Stock Photos. June 15, 2004.