Ch. 24 Ecology

Ecology is defined as the study of organisms in relation to their environment.
Population: A group of organisms living in the same area at the same time.
Species: A group of organisms that can interbreed and produce fertile, viable offspring.
Community: Multiple populations (e.g., humans, coyotes, palm trees, butterflies) living in the same area at the same time.
Ecosystem: The interaction between biotic (living community) and abiotic (non-living components like soil, temperature, water) factors.
Habitat: The place where a species lives.

Biotic factors: Living factors such as organisms themselves, diseases (e.g., avian flu), and interspecific interactions (predation, commensalism, herbivory).
Abiotic factors: Non-living factors such as climate, temperature, water, salinity, and pH.
Example of pH affecting organisms: Hydrangeas change flower color based on soil pH (acidic = blue, alkaline = reddish).
Edaphic: Relating to soil.

Biomes are major ecosystems spread over wide geographic areas with similar climatic conditions and similar flora and fauna.
Includes terrestrial and aquatic types.
Desert biomes share similar characteristics of temperature, precipitation, and weather patterns worldwide.
Climate determines the biome, and climate is determined by temperature and precipitation.
Climber graphs illustrate the distribution of biomes based on temperature and precipitation.

Based on the relationship between temperature and precipitation.
X-axis represents a negative scale.
- Tropical rainforest: High temperatures and high precipitation.
- Tundra: Extremely low temperatures and low precipitation.

Tropics receive sunlight at 90 degrees, resulting in higher temperatures.
Temperate regions and poles receive sunlight at higher angles, resulting in lower temperatures.

Determined by the permanent tilt of the Earth (23.5 degrees).
Northern Hemisphere summer: Tilted towards the sun, while Southern Hemisphere experiences winter.
Revolution of the Earth around the sun causes seasons.
Aquatic biomes are shaped by ocean currents and water salinity.
Estuary: Junction between a river and a sea/ocean with mixing of fresh and saline water.

The ecological role or profession of a species (e.g., an oak tree).
Ecological services provided: photosynthesis (producing oxygen), providing shade, acorns for squirrels, habitat for animals, and preventing soil erosion.
No two species can have the same niche; otherwise, competition occurs, and one species may outcompete the other.

Water cycle, nitrogen cycle, carbon cycle, and phosphorus cycle (phosphorus cycle lacks an atmospheric component).

Water is lost from terrestrial ecosystems through transpiration (loss of water from aerial parts of plants).
Water flows into rivers and streams via runoff.
Evaporation transforms liquid water into a gaseous state.
Condensation: As air rises, temperature drops, causing water vapor to become water droplets.
Precipitation: Water falls back to Earth as rain.

Involve both biotic and abiotic components, including abiotic reservoirs such as rivers, streams, rocks, and the atmosphere.

Nitrogen is a vital component for living organisms, abundant in the atmosphere (79%).
Essential for plant growth, proteins, and DNA.

Stages of the Nitrogen Cycle

Nitrogen fixation: Atmospheric nitrogen converted to ammonium.
- Acetobacter: Free-living bacteria in soil.
- Rhizobium: Resides in root nodules of leguminous plants.
- Cyanobacteria: Blue-green bacteria.
- Lightning.
- Haber process: Industrial process combining nitrogen and hydrogen to produce ammonia.
Nitrification: Ammonium converted to nitrite (NO2), then to nitrate (NO3).
- Nitrosomonas: Converts ammonium to nitrite.
- Nitrobacter: Converts nitrite to nitrate.
- Nitrate is the form usable by plants (assimilation).
Assimilation: Nitrogen gets incorporated into plant parts.
Denitrification: Nitrate converted back to nitrogen.
- Pseudomonas denitrificans bacteria facilitate this conversion.

Causes: Eutrophication, acid rain, and photochemical smogs.
Eutrophication: Excess nutrients (N, P, K) from fertilizers cause algal bloom in bodies of water.
- Algae die, aerobic bacteria decompose them, oxygen levels drop, leading to fish death.
- Natural eutrophication occurs over centuries, while cultural (anthropogenic) eutrophication is accelerated and occurs in decades.
Acid Rain: Sulfur dioxide and nitrogen oxides react with water to form sulfuric and nitric acids.
- Damages forests, decays leaves, corrodes marble statues.
Photochemical Smog: Oxides in the atmosphere react in the presence of light.
Thermal Inversion: Pollutants trapped between two layers of cold air, preventing dispersion.
- Usually, warm air rises, but cold air gets trapped in thermal inversion scenarios.
- Thermal inversion ceases when sunlight heats up the Earth’s surface.

Greenhouse gases include carbon dioxide, methane, oxides of nitrogen, chlorofluorocarbons, sulfur dioxide, and water vapor.

Greenhouse gases trap incoming Earth's rays, warming the surface.
Without greenhouse gases, Earth would be frigid.
Incoming high-energy rays (e.g., UV) are converted to infrared upon striking the Earth’s surface.
Greenhouse gases reflect infrared radiation back to Earth. Excessive amounts of this reflection cause global warming.
Ozone shields the Earth and chlorofluorocarbons erode the ozone layer by colliding against it through chain reactions over many years.

Inedible parts (hooves, nails, claws, fur) and feces lead to carbon loss.
10% Rule: Only 10% of energy is transferred from one trophic level to the next, due to entropy and the laws of thermodynamics.
Energy can neither be created nor destroyed.

Autotrophs: Inorganic carbon source (carbon dioxide).
- Producers making their own food.
- Photoautotrophs use light as their energy source.
- Chemoautotrophs use chemicals as their energy source.
Heterotrophs: Organic carbon source.
- Rely on autotrophs.
- Consumers (primary, secondary) eat producers or other consumers.
- Decomposers rely on dead organic matter.
  - Detritivores (e.g., earthworms) ingest dead organic matter.
  - Saprotrophs (bacteria, fungi) secrete enzymes, break down polymers into monomers, and absorb them.

Position of an organism in a food chain.
Food chain: Linear sequence of energy transfer between trophic levels.
- Arrows denote the flow of energy, not who eats whom.
Food web: Interconnected food chains.

Graphical representation of relationships between trophic levels.
- Pyramid of numbers: Represents the number of organisms.
- Pyramid of biomass: Shows the flow of energy over time in terms of energy.
- Pyramid of energy: Illustrates the flow of energy between trophic levels.

Limited due to the 10% rule; energy available diminishes at higher trophic levels, limiting chain length.