Introduction to Ecology

• Ecology is the study of the interactions between organisms and their environment, spanning multiple levels of study including organisms, populations, communities, ecosystems, and the globe

Levels of Ecological Study

• Organismal ecology explores adaptations (morphological, physiological, and behavioral) that enable individuals to live in specific environments
• Population ecology studies how the number and distribution of individuals in a population change over time
• A population is a group of individuals of the same species living in the same area at the same time
• Community ecology examines the interactions between different species within a specific area and their consequences
• A biological community consists of the species that interact with one another within a particular area
• Ecosystem ecology focuses on how energy and nutrients move among organisms and through the surrounding environment (atmosphere, soil, or water)
• An ecosystem includes all the organisms in a region along with nonliving (abiotic) components
• Global ecology studies the biosphere, the thin zone surrounding the Earth where all life exists, and the effects of global changes on it
• This is a young but rapidly growing field

Niche and Factors Affecting Organism Distribution

• A species' niche is the range of conditions it can tolerate and the resources it can use
• A species' realized niche is determined by abiotic and biotic factors, both past and present
• Abiotic factors include climate, resources, and other non-living elements
• Biotic factors include interactions with other organisms such as pollinators, pests, predators, parasites, and competitors
• Fitness trade-offs are evolutionary compromises between traits that cannot be optimized simultaneously, limiting the environmental conditions a species can live in
• Dispersal is the movement of organisms from their place of origin to where they live and breed as adults

Climate and Global Patterns

• Weather is short-term atmospheric conditions, including temperature, precipitation, sunlight, and wind
• Climate is the long-term prevailing weather conditions in an area
• Warm areas receive a large amount of sunlight per unit area
• Cold areas receive a small amount of sunlight
• At the equator, sunlight strikes the Earth at an angle allowing the maximal amount of solar radiation
• As Earth's surface slopes away from the equator toward the poles, sunlight arrives at lower angles, minimizing the energy (and heat) Areas along the equator receive the most moisture
• Areas at about 30°N and 30°S latitude are among the driest on Earth
• Global air circulation is patterned by Hadley cells, which lift warm, moist equatorial air that cools and drops rain, then descends as dry air around 30° latitude
• The Coriolis effect deflects air and water, creating clockwise patterns in the Northern Hemisphere and counterclockwise patterns in the Southern Hemisphere
• Seasons are annual fluctuations in temperature and precipitation
• In June, the Northern Hemisphere is tilted toward the Sun
  • It faces the Sun most directly and receives the largest amount of solar radiation per unit area
• In December, it is summer in the Southern Hemisphere and winter in the Northern Hemisphere
• In March and September, the equator faces the Sun most directly, so the tropics receive the most solar radiation

Regional Climate Effects

• Mountain ranges can modify regional climate
• As moist air blows up a mountain range, it cools and loses its ability to hold water, producing rain
• The cool, dry air then passes the mountain ridge
• The area on this side of the ridge receives little precipitation and is said to be in a rain shadow
• Oceans moderate temperature due to water's high specific heat:
  • Water absorbs atmospheric heat in the summer and releases it in winter
• Coastal areas generally have more moderate climates than inland areas
• Gyres, or massive ocean current cycles, bring warm water to colder latitudes and vice versa

Terrestrial Biomes

• Biomes are regions characterized by distinct abiotic characteristics and dominant vegetation types
• Examples: broad-leaved evergreen forests, deserts, grasslands, and tundra
• Each terrestrial biome is determined largely by climate-temperature, moisture, sunlight, and wind
• The nature of the biome that develops in a particular region is governed by average and annual variation in temperature and precipitation
• Temperature and moisture influence net primary productivity (NPP), or total amount of biomass generated by the carbon that is fixed per year minus the amount oxidized during cellular respiration
• Biomass refers to the total mass of organisms, primary producers in this case
• In terrestrial environments, NPP is often estimated by measuring aboveground biomass, the total mass of living plants, excluding roots
• Photosynthesis, plant growth, and NPP are maximized in sunny, warm, wet conditions
• About 75% of Earth's ice-free land shows evidence of direct alteration by humans Examples: farming, logging, and urban development
• Wildlands account for just 11% of terrestrial NPP
• Simulation studies, observational studies, historical studies, and experiments are the tools that Biologists use to understand how climate change will affect ecosystems

Aquatic Biomes

• Salinity, water depth, water flow, and nutrient availability are the four abiotic factors that distinguish streams from oceans
• The turbidity, or cloudiness, of the water is an important determinant of light penetration
• Organisms occupy zones based on their own adaptations
• Plankton (small, drifting organisms) and many of the animals that eat them are common in the photic zone
• Invertebrates and fish that consume dead organic matter, or detritus, are abundant in the benthic zone

Ocean and Lake Zones

• Oceans
  • Submerged at high tide areas that exposed at low tide
  • Continental shelf is -from the intertidal zone to about 200 m, defined by the gently sloping, submerged portion of a continental plate
• Coral reefs can be found here
  • Deepwater region beyond the continental shelf
  • Bottom of the ocean at all depths
  • Regions that are sunlit, including the intertidal and portions of the neritic, oceanic, and benthic zones Areas that do not receive sunlight include the aphotic zone
• In the ocean photic zone, sunlight is abundant, but nutrients are hard to come by When organisms in the zone die, they drift down to the benthic zone
• Lakes Littoral ("seashore") zone has shallow waters along the shore, where plants can take root
• Limnetic (“lake") zone is offshore and comprises water that receives enough light to support photosynthesis; too deep for plants to take root The photic, aphotic, and benthic zones are similar in definition to those in the ocean

Nutrient Availability

• Three types of water flow provide critical nutrients:
  • Coastal runoff
  • Ocean upwelling
  • Lake turnover
• As water rushes down mountains and streams get wider and slower, nutrients gather, sink, and collect at the bottom as debris
• In estuaries, sunlight is also plentiful, making them among the most productive environments on Earth
• Nutrients that have fallen into the benthic regions are brought to the surface by currents that cause upwellings
• Each year, glacially formed lakes undergo spring and fall turnovers in response to air temperature changes
• Thermocline is gradient where In winter and summer, the temperature in these lakes varies
• During lake turnover The water on the bottom of the lake is displaced, so it comes to the top, carrying nutrients and sediments A rapid increase of photosynthetic organisms follows, and eventually, the lake again stratifies in the summer