Principles of Ecology

Introduction to Ecology

Ecology is the science that describes and explains the relationships between living organisms and their environment. Coined by German zoologist Ernest Heckel in 1866, it derives from the Greek word oikos, meaning "home" or "place of dwelling," thus representing the "home life" of organisms.

Core Focus: Ecologists describe and quantify connections between organisms and their environment.
Alternative Definition: Ecology also seeks to understand the distribution and abundance of organisms, creating and testing hypotheses to predict these patterns.

Why Care About Ecology?

Humans are an integral part of ecological systems and depend on them for survival and quality of life. The rapidly growing human population is altering the biosphere, making it less capable of sustaining human civilization.

Human Population Growth: The global population reached 7.888 billion in 2021, projected to be 8.3 billion in 2024, with a doubling time of approximately 61 years.
Adverse Effects: No single species has had such a profound and adverse effect on the biosphere, leading to mass extinctions, which historically were caused by natural catastrophes like meteor impacts.

Global Atmospheric Changes and Human Impact

Human population growth and waste products are causing significant global atmospheric changes.

Ozone Depletion: Illustrated by a map showing ozone levels, particularly over the Antarctic.
Global Warming: Evidenced by historical temperature changes in the Northern Hemisphere, Arctic sea ice boundary retreat (comparing 1979 to current), and glacier melt (e.g., Pasterze Glacier from 1875 to 2004).

The Biosphere: Our Fragile Home

The biosphere is the only known planet supporting life, and it is a fragile, complex interacting system of living organisms and the physical environment. Ecological processes have made Earth more hospitable to life, leading to increased biodiversity over geological time.

Biosphere Components: It contains all life and includes land (lithosphere), water (hydrosphere), and air (atmosphere).

Levels of Ecological Organization

Ecologists study organisms across various hierarchical levels of organization, from individual organisms to the entire biosphere.

Organism: An individual living thing, representing a single species (e.g., a crocodile).
Population: A group of individuals of the same species living in one area. Population growth or behavior refers to changes in individual numbers over time due to births and deaths.
Community: A group of different species' populations living and interacting together in one area (e.g., predator-prey relationships).
Ecosystem: A group of communities and their populations, embedded in a common physical environment and tied together by physical processes. It includes all organisms and nonliving things like climate, soil, water, and rocks.
Landscape: A group of ecosystems that may or may not interact within a given region.
Biome: A group of ecosystems sharing the same climate and similar dominant communities, typically classified by predominant vegetation.
Biosphere: The combined portion of the planet where all life exists, encompassing all biomes and ecosystems interacting with the physical environment of Earth.

Environment and Interactions

The environment of an organism includes all external factors and phenomena that influence it. Interactions are simply how organisms and their environment, including different ecosystem components, interact for survival.

Biotic Factors: All living organisms inhabiting the Earth (e.g., other living organisms).
Abiotic Factors: Nonliving parts of the environment (e.g., temperature, soil, light, moisture, air currents).

Principles of Ecology: Introduction, Human Impact, and Levels of Organization

Principles of Ecology: Introduction, Human Impact, and Levels of Organization