Population Growth How do communities change over time

Population Growth How do communities change over time?

• Groups of 2, 3, or 4…spread out…face each other! 1. Chunk/Divide up the text. Say Something… 2. Decide how to read (Independently? Aloud? Take turns? ) 3. Begin. When it’s your turn to “say something” do one of the flowing using the discussion stems provide: 1. Make a prediction 2. Ask a question 3. Clarify something you misunderstood 4. Make a comment 5. Make a connection

Population growth • Populations will grow until they reach their biotic potential, unless they are limited by factors in the environment • This type of growth is known as a J-curve called EXPONENTIAL GROWTH

Exponential Growth (J-curve) • As a population gets larger it also grows faster. • Resources (food, water, space) are unlimited and plentiful.

Population growth • As resources (called limiting factors) become scares, the population growth will slow. • This type of growth is known as a S-curve. called LOGISTIC GROWTH

Logistic Growth (S-curve) • Population growth eventually slows/stops and stabilizes when it reaches its carrying capacity • Resources (food, water, space) are scarce and in limited supply.

Logistic Growth • Occurs when a population’s growth slows or stops following a period of exponential growth As resources become less available, the growth of a population slows or stops

Population growth Carrying capacity is defined as the number of individuals an environment can support.

Population growth • Limiting factors in the environment help to maintain ecosystem stability by allowing populations to fluctuate around the carrying capacity. • This is called dynamic equilibrium.

What is the CARRYING CAPACITY of the deer on Walla Island?

LIMITING FACTORS • A limiting factor is a factor that causes population growth to decrease. • 2 TYPES: – Density-Independent – Density-Dependent

DENSITY – DEPENDENT LIMITING FACTORS • DDLFs are resources that have greater effects as the population size/density increases. • Affects larger population sizes/densities

EXAMPLES of DENSITY – DEPENDENT LIMITING FACTORS • • Availability of Food Availability of Water Availability of Space Competition Disease Predation Migration

DENSITY – INDEPENDENT LIMITING FACTORS • Resources/factors that affect all populations, regardless of the population density (size).

DENSITY – INDEPENDENT LIMITING FACTORS • Resources/factors that affect all populations, regardless of the population density (size). • Affects all population sizes/densities.

EXAMPLES of DENSITY – INDEPENDENT LIMITING FACTORS • Natural Disasters (floods, hurricanes, earthquakes, tornadoes, forest fires, etc. ) • War and Human Activities • Weather (drought) • Temperature (frost)

Practice! • Complete the practice worksheet (both sides). • Finish for Homework