Population Growth

A population is….

A group of organisms, of the same species, that live in the same location.

Ex: population of frogs in Lums Pond

Ex; population of bacteria in a mouth

Ex: human population of Delaware

Biotic Potential

The highest rate of reproduction under ideal conditions

Ex: a fly’s biotic potential is 900.

Ex: a human’s biotic potential is over 68 children.

Population Density

The number of individuals in a given area .

(Ex: 22 students/classroom or 18 people/phone booth)

Calculating Population Density

Population Density =Number of Individuals

Unit Area

Example:

Suppose you counted 200 Oak trees in a 100 acre area. What is the population density?

Answer : 200 oaks/100 acres or 2 oaks/1 acre

Question

If both Wilmington and Milton are considered the same size area, which would have the higher Population Density?

Three basic patterns for a population’s growth

Linear growth

Exponential growth

Logistic growth

Linear Growth

Growth that occurs at a constant rate would be considered linear growth

Example: If my hair grows .25 inches every week, then in one month my hair grows 1 inch, in two months it grow two inches, and in three months it grows three inches

Linear growth

Exponential Growth

Bacteria can reproduce quickly given the resources…

Exponential Growth

Describe what it means by looking at the graph.

Starts out slowly…takes a long time to build up and then it has a rapid increase.

Current world populations is approximately is over 7.2 Billion since October 2013.

Logistic Growth: The S curve

Logistic GrowthWhat does it mean according the graph pattern?

The population grows exponentially until limiting factors halt population growth and things eventually start to die out.

No population can grow forever:

Growth stops when the population reaches its CARRYING CAPACITY

The maximum number of individuals that an environment can support!

Scientists estimate the world’s carrying capacity for humans to be around 8.5-10 billion people.

Population Growth Depends on 2 Things

Birth RateNumber of births in a given amount of time

Ex: US birth rate is 14.16/1000 people

Death RateNumber of deaths in a given amount of time

Ex US death rate is 8.27/1000 people

Changes in Predator and Prey populations

Predator and Prey relationship

As the population of prey increases ( ), the predator population ( ) begins to follow it.

As prey populations begin to decrease ( ), the predator populations begin to decrease

( ).

Whooping Cranes (Grus americana) are the tallest birds in North America. They stand about 1.6 metres tall and have a wingspan of two metres.

Beginning in the 1900s the Whooping Crane population began to decline as wetland habitat was drained for farmland and as birds were shot. By 1941, only 16 birds survived and shortly after this a concerted conservation efforts by Canada and the United States began. This effort has succeeded in increasing the population to about 180 birds by 1999.

Distribution