Community A group of different populations that lives in the same geographic area

Community Interactions Interactions between organisms have a huge impact on ecosystems.

Community Interactions Types of interactions: Competition—when organisms attempt to use a resource in the same place at the same time. Competitive exclusion principle—no two species occupy the same niche in the same habitat. Predation—an interaction where one organism captures and feeds on another organism

More interactions Symbiosis—a relationship in which two species live closely together. Usually one species lives on or inside of another. One species always benefits and other can be harmed, helped, or have no effect.

Types of Symbiosis Mutualism—a symbiotic relationship in which both species benefit. Ex: Flowers and the insects that pollinate them. Commensalism—a symbiotic relationship in which one species benefits and the other is unaffected. Ex: barnacles on a whale Parasitism—a symbiotic relationship where one species benefits and the other is harmed. Ex: Fleas, ticks, tapeworms and their hosts.

Types of Symbiosis . The acacia tree and Pseudomyrmex ants are an example of mutualism

Types of Symbiosis . An epiphyte plant is an example of commensalism

Types of Symbiosis . A tapeworm is an example of a parasite

Ecological Succession Ecological Succession—The series of predictable changes that occurs in a community over time. As an ecosystem changes, older species gradually die out and new species move in.

Types of Succession Primary Succession—When succession occurs on surfaces where no soil exists. Ex: after a volcanic eruption builds a new island or covers land with lava rock. Secondary Succession—When a disturbance changes an ecosystem without removing the soil. Ex: a forest after a fire.

Succession Climax Community—an older, established community that is no longer changing (as much)

Populations Population Density—The number of individuals per unit area Ex: number of dandelions per m2

Population Growth Several factors affect population size: Births— # of organisms born Deaths— # of organisms that die Immigration—The movement of organisms into a population Emigration—The movement of organisms out of a population

Exponential Growth Unrestricted populations of organisms experience exponential growth. Must have unlimited resources

Exponential Growth Graph

Logistic growth As resources become less available, population growth slows or stops (birth rate=death rate) This is called leveling off. Carrying capacity—The maximum number of organisms that the environment can support

Logistic growth graph

Limiting factors Limiting factor—a factor that causes population growth to decrease.

Density-Dependent factors Density-Dependent factors—limiting factors whose effects increase as the size of the population increases Ex: Competition, predation, parasitism, disease

Density-Independent factors Density-Independent factors—Limiting factors that affect all populations in similar ways, regardless of population size and density Ex: Natural disasters, seasonal cycles, certain human activities

Human populations Demography—The scientific study of human populations

Exponential Growth in our human population Since the industrial revolution of the 1800s the human population has been experiencing exponential growth.

Effects of increased growth If the human population continues to grow at an exponential rate this could cause: Starvation and death for millions Some countries to set limits on birth rates

Slowing population growth Human population growth can be slowed by: Global epidemics (influenza, HIV, etc.) Limiting birth rates

Biodiversity Biodiversity—the total variety of organisms in the biosphere. It is important to preserve biodiversity for a variety of reasons (food webs, new medicine, etc.)

Maintaining biodiversity Humans can help maintain biodiversity by: Enforcing the Endangered Species Act Making laws protecting the wilderness (including rainforests)

Destroying Biodiversity Humans can destroy biodiversity by: Habitat destruction - *** Keystone species may leave/die so those below it on food chain are effected Introducing invasive species (ex: Zebra mussels in Great Lakes, rabbits in Australia, etc.)

The Greenhouse effect The Greenhouse effect— Water vapor and greenhouse gases (CO2, methane, etc.) trap heat from the sun in our atmosphere. This keeps Earth warmer, like the glass panels of a greenhouse.

Global Warming Global Warming—An increase in greenhouse gases which increases the amount of heat trapped in Earth’s atmosphere. ADD; Specifically CO2

Human activities causing global warming Burning fossil fuels and cutting down the rainforests are increasing greenhouse gases (especially CO2), which is most likely causing global warming.

Temperatures rise  glaciers melt  sea levels rise Solutions: Burn less fossil fuels alternative energy sources

Air Pollution The quality of our air is important to our health. Burning fossil fuels and factory emissions being released into the air contribute to air pollution.