AP Biology

• So far, we have looked at how homeostasis controls and regulates our bodies (removal of nitrogenous waste, immune system).
• While these are good examples of homeostasis, they are at an organism or cellular level.
• We can also see examples of homeostasis at higher levels such as populations, communities and ecosystems.
• The purpose of this exercise to to explore some of these higher levels of homeostasis and the environment.

• You will be given an example of homeostasis and the environment.
• First, your group should figure out the following
• What level (biome population individual)?
• Does your example involve natural homeostasis, or response to a disruptor?
• If it is in response to a disruptor, what is the disruptor?
• Gather any other relevant facts (use books, phones)
• Then you will answer the following short free response question:

• Remember, you only want to answer the question with relevant information.
• Your response should be 4 or 5 sentences.
• The structure of the response:
• Define your example (give an example if applicable)
• Explain if it is natural or a disruption
• Explain how is shows homeostasis.

Succession is the natural evolution or progression of an ecosystem, and there are two types: primary or secondary.
Primary succession is a natural process where life colonizes new land. Secondary succession can either be a natural progression (a lake becoming a meadow then a forest) or a response to a disruption (after a forest fire).
Succession shows how an ecosystem stabilizes after a disruption as plants and animals return.

Station Example
1 Predator/Prey
Relationship
2 Carrying
Capacity
3
Invasive
Species
4 Acid Rain
Station Example
5 Global Warming
6 Deforestation
7 Photoperiodism
8 Biofilms (Quorum sensing in bacteria)

Example Explanation
Predator/
Prey
Predator and prey relationships consist of a carnivore kill and eating another animal. An example is when a pride of lions stalks and kills a gazelle. The predator/prey relationship involves homeostasis by regulating each others’ population size.
Carrying
Capacity
Carrying Capacity is the maximum number of individuals an environment can support based on the amount of available resources. Limiting factors such as disease, crowding and predators are natural regulators. The limiting factors stabilize the population size and maintain homeostasis.

Invasive
Species
An invasive species is an organism that is not native to a specific location (introduced and spreads out of control). It disrupts homeostasis in an ecosystem. For example, rabbits were introduced to Australia and ate native plants and over-populates because there are no natural predators. It disrupts homeostasis because invasive species unbalances the food web.
Acid
Rain
Acid rain is a human-caused environment effect caused by chemical pollution that reduces the pH level of precipitation. Acid rain is a disruptor by affecting reproduction of plants and animals. It turns lakes acidic
(kills aquatic organism) and destroys nutrients needed by plants. Homeostasis is restored by reducing by sulfuric and nitrogenous pollution.

Global Warming
Global warming is an increase in earth’s average temperature. CO2 and other gases are collecting in the atmosphere, trapping the sun’s heat and causing the planet to warm up. Global warming could be a major disruptor to the Earth’s homeostasis
Deforestation
Deforestation is the process where forests are removed through logging or burning to use the timber or the cleared and for agriculture.
Deforestation is a disruptor because it destroys habitats and causes erosion. 46,000 – 58,000 square miles are lost each year. Deforestation disrupts plant and animal habitats.

Photoperiodism
Photoperiodism is an organism’s response to changes in the length of night. Examples include flowers blooming, trees dropping their leaves and animals migrating. Photoperiodism is a natural process and it maintains homeostasis by triggering responses in plants and animals.
Biofilms
Biofilms are surface-coating colonies or one or more species of bacteria that work in metabolic cooperation. They are natural occurrences and cause cells to stick to one another. An example of a biofilm is the layer of dental plaque that forms on teeth overnight. In this example, the biofilm can disrupt homeostasis by cause tooth decay.

• Piece of paper with the answer – remember: Keep it short!!
• We will put them together on a slide and discuss.