In-Depth Notes on Ecology and Biogeography

Introduction to Ecology

• Ecology is the study of interactions between living organisms and their environment.
• The module will introduce different levels of ecological study, including organismal ecology, population ecology, community ecology, and ecosystem ecology.

Levels of Ecology

Organismal Ecology

• Focus: Single organisms and adaptations to their habitats.
• Example: Karner blue butterfly, a specialist species that lays eggs on only wild lupin.
  • As caterpillars, they rely completely on wild lupin for food but feed on various wildflowers as adults.

Population Ecology

• Focus: Populations, defined as interbreeding organisms in the same area at the same time.
• Key Concepts:
  • Population dynamics involve birth rates, death rates, and migration.
  • Conspecifics: Individuals of the same species within a population.

Community Ecology

• Focus: All living organisms in a specific area.
• Key Concepts:
  • Interactions within a community can be between conspecifics (competition for resources) or heterospecifics (predation, parasitism).
  • Example of mutualistic relationships: Karner blue butterfly caterpillars and ants (caterpillars provide sugar to ants, and ants offer protection).

Ecosystem Ecology

• Focus: Communities along with abiotic (non-living) factors like sunlight, water, soil nutrients, and gases.
• Example: The relationship between soil nutrient availability and the distribution of the wild lupin that the Karner blue butterfly relies on.

Biogeography

• Definition: The distribution of life across Earth.
• Influencing Factors:
  • Primarily abiotic factors such as temperature and precipitation, which vary with latitude and elevation.
• Example: Changes observed when moving from the Central Valley to Shaver Lake, noting differences in temperature and precipitation.

Species Types

Endemic vs. Generalist Species

• Endemic Species: Species with limited geographical ranges (e.g., many animals in Australia).
• Generalist Species: Species that thrive in a wide range of environments (e.g., house mouse, mockingbird).

Abiotic Factors Influencing Biogeography

• Temperature: It affects species distribution.
  • Adaptation techniques: Migration, torpor (reduction in metabolic rate).
• Water: Presence and type (freshwater vs saltwater) influence species adaptations.
• Nutrient Availability: Critical for producer growth, impacting entire food chains.
• Ocean Upwellings: Nutrient-rich waters brought to the surface by wind patterns.

Aquatic Ecosystem Dynamics

Lake Turnover

• Spring Turnover: Warmer/denser water (4°C) sinks, bringing nutrients from the bottom to the surface.
• Fall Turnover: As surface water cools and reaches 4°C, it sinks, similarly pushing nutrients upward.
• Thermocline: A stratified layer of temperature in lakes.

Climate Change

Definitions

• Weather: Short-term atmospheric conditions.
• Climate: Long-term averages of weather conditions.

Factors Driving Climate Change

1. Milankovitch Cycles: Changes in Earth's orbit affecting solar radiation.
2. Natural Solar Radiation Variation: Fluctuations in solar output.
3. Volcanic Eruptions: Can cause cooling through atmospheric particles blocking sunlight.
4. Greenhouse Gases: Human impact primarily affects levels of greenhouse gases (CO$_2$, methane).

Greenhouse Effect

• Greenhouse gases trap heat in the atmosphere, preventing it from escaping, similar to a blanket.
• The most significant greenhouse gas influenced by humans is CO$_2$, derived from burning fossil fuels.

Fossil Fuels

• Comprised of hydrocarbons from ancient organic materials.
• Combustion releases carbon that was stored underground, contributing to atmospheric CO$_2$ buildup.

Impact of Human Activity

• Human-caused climate change leads to higher concentrations of greenhouse gases, evidenced by data showing a significant rise in CO$_2$ since the 1800s.
• The increase in global temperatures correlates with the rise in greenhouse gases.
• Historical variations in greenhouse gases tracked through ice cores show current levels are unprecedented.

Conclusion

• Climate change poses severe consequences, accelerated by human actions.
• Even if all fossil fuel use ceased, temperatures would continue to rise due to existing CO$_2$ levels in the atmosphere.