Populations

Population Dynamics Population: a group of the same species that interbreed and live in the same area at the same time

Population Characteristics Density How many egrets are there in an area of 2km² Dispersion Uniform Clumped Random http://glencoe.mcgraw-hill.com/sites/0078695104/student_view0/unit1/chapter4/concepts_in_motion.html#

Principles of Growth How fast do populations grow? What are the limitations? Do organisms show patterns in their growth? http://www.otherwise.com/population/index.html

Population Ranges What determines which animals live where? A Bit of Review… Two Major Factors Limiting Factors Tolerance Ranges Other influencing factors: Competitors Predators Parasites

What limits population growth? Types of Limiting Factors Density Independent Any factor in the environment that does not depend on the number of members in a population per unit area Usually abiotic May cause a total wipeout Examples of natural events: Examples of Human alterations:

Types of Limiting Factors Density Dependent Any factor in the environment that depends on the number of members in a population per unit area. Usually biotic factors Predation Disease Competition Occurs between same species and different species Causes starvation or emigration to decrease competition Parasites

Effects of Competition When populations are low, resources are plentiful When populations increase, resources become scarce-

What is the relationship of the hare and the lynx? What might happen to the lynx if the producers in the area suffered a major decline? Explain.

Explain the relationship between the three populations of organisms and how their growth or decline rate are related to each other. Explain what density dependent factor might have influenced the two animal populations.

Population Trends Hurry up already. I am already two weeks old. We have to have as many kids as possible before we are ancient! No worries….let’s travel and see the Savannah before we have kids. I’m not ready yet. I need to be able to support my family first.

How fast can a population grow? Small Organisms Large Organisms Elephant - k-strategist Adapted to a stable environment Long life span – no hurry Few offspring Mosquito - r-strategist Adapted to an unstable environment short life span – hurry up many offspring Why the differences???

How fast can a population grow? Populations grow exponentially when resources are unlimited. An exponential Growth Curve http://www.otherwise.com/population/index.html

Population Growth Limited by carrying capacity: carrying capacity: the number of one species an area can support Limitations include: oxygen, nutrients, water, energy Causes a logistic growth curve to occur http://www.otherwise.com/population/index.html Logistic Growth Model