Warm-Up Fri 4/7 If the producers have 10,000 J of energy, how much energy is contained in the highest trophic level? What is the name of this type of pyramid? Which organism would be the most affected by toxic chemicals in the water? EXPLAIN.

To be successful today… Pick up warm-up sheet **If you need to make-up a test, you must do so by tomorrow AM. ** 3) STAAR Review in Auditorium TODAY! BYOD Color of the day is Phones are in put away in backpacks

Warm-up Mon 4/10 How would the populations of rabbits and hawks would change if a forest fire destroyed all the grass? What type of disturbance is this?

Population Ecology

Population Ecology Deals with factors that affect population size Natural and Human Disturbances play a role in the shaping an ecosystem. Natural Disturbances – fire, tornadoes, hurricanes, etc. Human Disturbances – deforestation, destroying of habitats.

Population Ecology Natural and Human disturbances can lead to a change in a population over time. If the number of species in one community changes it will ultimately lead the changes in the number of species in all other communities in the ecosystem.

Sea Otter Example

Predict what happens to sea urchin and kelp when sea otters are removed

How Populations Change Over Time Three factors control how a population changes over time: Number of births Number of deaths Number of individuals that enter (emigration) or leave (immigration) an ecosystem

Carrying Capacity Carrying Capacity - The largest number of individuals that the environment can support! When an ecosystem reaches its carrying capacity the food web begins to change drastically.

Predict what happens when a population “overshoots” its carrying capacity

Population growth Populations can grow in 2 different ways:

1) Exponential growth Growth under ideal conditions at an ever increasing rate Abundant space, food, protection J-shape curve

2) Logistic growth Growth when resources become less available and growth slows S-shape curve NOTE: even when population growth stops it still rises and falls somewhat

Other Growth Curves Boom and Bust Exponential Growth that leads to population crash Predator-Prey Predator & prey populations increase and decrease together

Describe these growth curves

Limiting Factors Limiting factors are factors that cause population growth to decrease. Can be dependent on the species in the ecosystem or completely unpredictable like natural disasters.

What Limits the size of a population?

Density dependent limiting factors Depends on population size Operates most strongly on large populations Competition for resources — food, water, space, sunlight Competition within species or with different species

Density-Independent limiting factors Affects all populations, regardless of the size of the population Population crashes Causes: human activity, weather, and natural disasters

Practice Classify each of the following as either density-dependent or density-independent. Intense heat wave Half of the forest trees are cut down 3. Sudden blizzard 4. Overpopulation of an organism

What happens when an invasive species is introduced into an established ecosystem?

Not native to ecosystem No natural predators Can outcompete native species for resources Examples: Kudzu vine, Chinaberry trees