# AP Environmental Science/Ecology

Ecology is the biological science that studies the relationships between living organisms and their environment. The levels of biology are, in order:
* Biosphere
* Biomes (terrestrial regions inhabited by certain types of life, especially vegetation. Examples include various types of deserts, grasslands, and forests)
* Ecosystems
* Communities
* Populations
* Organisms
Eukaryotic organisms are organisms that have a nucleus; their domain is eukarya and kingdoms in this eukarya are protists, fungi, animals, plants, etc. Prokaryotic organisms are organisms that have no nucleus--their domain is bacteria (archae), and kingdoms include archaebacteria and bacteria. Genetic diversity is the variability in the genetic makeup among individuals within a single species. This is important since genetic diversity gives populations disease-resistance. The California Condor is a good example relating to the topic of genetic diversity. Although the population has improved from 15 to 300, it is still not enough for them to achieve a disease-protecting genetic diversity.

### Biosphere

The biosphere are the zones of the earth where life is found. This includes the water (hydrosphere), crust (lithosphere/geosphere) and air (atmosphere).

#### Atmosphere

    See more at Layers of the Atmosphere
The atmosphere is the mass of air surrounding a planet. The ones we will mention here in this section is the troposphere, where our weather and habitat is found. The troposphere is the only atmospheric layer that can sustain living organisms and supports climate change. The stratosphere is the layer where the Ozone Layer is found. The Ozone Layer protects us from UV radiation.
The four natural gases, carbon dioxide, water vapor, methane, and nitrous oxide, and several other gases make the earth sustainable and habitable.

##### UV radiation

UV rays do not have heat within themselves, but rather they generate heat by being absorbed and radiated back into the atmosphere as infrared radiation.

### Biomes

Biomes: Already defined above.
Acquatic life-zones: marine systems (ocean); two types: saltwater and freshwater; the "biomes of the ocean".
Ecotone: Transitional zone between ecosystems (marsh, swamp)

#### Range of Tolerance

Range of Tolerance: The extent to which a population can withstand variations in its chemical and physical environment. Extreme variations in the environment require a wide range of tolerance. Examples are in intertidal zones, organisms living here need to have to be able to live easily in a variety of air temperatures and need to have a good range of tolerance for storm energy. This also goes for a desert, where organisms there need to be able to sustain the temperature and the water availability. The last example is a estuary (salinity)(def)--see the Chesapeake Bay.

### Limiting factors

A limiting factor restricts the growth of a population. A limiting factor falls into either one of the two categories:
    Density: Number of organisms in a given area.
* Density Independent - Natural disasters (weather), pollution (organic chemical water pollution)
* Density Dependent - Disease, competition

#### Density Independent

* 5 box turtles, a hurricane passes by: it doesn't matter how many turtles there were, all were going to die.
* Oil spill: 100 oysters or not, all of the oysters would've been dead.

#### Density-dependent

* Flu: Proximity caused a spread in flu (school)

### Food Chain/Food Web

A food chain is a linear view of how energy is transferred while a food web is a display of several paths of how energy is transferred. 5-20% energy is transferred from one trophic level to the next.
Producers can include algae, chemotrophs (bacteria in wetlands and ocean vents) and cyanobacteria. Photosynthetic producers use Photosynthesis. The formula for photosynthesis is:
   energy from the Sun + 6CO$_2$ + 6H$_2$O → C$_6$H$_{12}$O$_6$ + 6O$_2$
Chemosynthesis is used by bacteria. Those bacteria convert sulfur in the presence of CO2 (carbon dioxide).

### Biodiversity

See chapter 1 for the other biodiversity fields. We will provide the definition of these two fields of biodiversity:
* Functional Diversity - A component of biodiversity that generally concerns the range of things that organisms do in communities and ecosystems.
* Ecological Diversity - Variety of terrestrial and aquatic ecosystems found in an area or on a place of the Earth.

### Pyramids

What an ecological pyramid shows:
-Energy -Organisms -Biomass (organic matter produced by plants and other photosynthetic producers)
Producers are at the bottom with the most energy.
Each trophic level, it decreases except numbers (temperate forest)). Temperate forest pyramids go from decreasing to increasing since the trees (producers; at the bottom) are able to provide for many organisms, such as insects--hence the increase in the trophic levels.

### Productivity

    See Talk:AP_Environmental_Science/CH._3._Introduction_to_Ecology#Productivity_Note for more
Productivity - production by producers of energy (glucose).
Gross productivity is all energy something is able to produce while net productivity is the energy left that is available for organisms (think of catching fish using a net). Levels of productivity are high near the coastlines of countries due to nitrogen and phosphorus (nutrients used by aquatic life are produced by the land--runoffs) and desert zones (wind blowing sand into the ocean).

### Threats to Biodiversity

* Habit destruction (deforestation for paper and houses)
* Invasive species (they use resources in a non-native land--lionfish eats other fish from the east coast; lionfish scenario also deals with species diversity)
* Pollution deals with specific fields of pollution like thermal pollution, pathogenic water pollution (oysters: MSX and Dermo)
* P[human]..opulation..[growth], which deals with the increase in humans (us)--leads to loss of ecosystems (functional diversity).
* Overexploitation/overharvesting: Oysters (genetic diversity in terms of disease like MSX and Dermo).