The term "Ecology" was coined by Ernst Haeckel in 1866 from the Greek words Oikos ("house" or "dwelling place") and Logos ("study of").
Definition: Ecology is the scientific study of the interactions between organisms and their environment, and how these interactions determine the distribution and abundance of organisms.
The "environment" includes:
A landscape is a heterogeneous area composed of a cluster of interacting ecosystems that are repeated in a similar form throughout. It's a mosaic of different "patches."
Definition: A habitat is the natural environment or "address" where an organism, population, or species lives.
It is characterized by its physical and chemical features (abiotic factors) and the other species living there (biotic factors). A habitat provides an organism with everything it needs to survive: food, water, shelter, and mates.
Definition: An ecotone is a transition zone between two or more different biological communities or ecosystems.
Ecotones are not sharp boundaries but gradual blending areas. They often have high species diversity because they contain species from both adjacent ecosystems, as well as species that are unique to the ecotone itself. This phenomenon is called the Edge Effect (covered in Unit 3).
The biosphere is the highest level of ecological organization. It is the global sum of all ecosystems.
Definition: The biosphere is the part of the Earth where life exists, including all living organisms, from the deepest ocean trenches to the highest mountain peaks and into the atmosphere.
It is a relatively thin layer that includes:
The term "Ecosystem" was coined by A.G. Tansley in 1935.
Definition: An ecosystem is a functional unit of nature, comprising all the living organisms (biotic community) in a particular area interacting with their non-living physical environment (abiotic factors) and with each other.
Key features of an ecosystem:
Ecosystem stability refers to the ability of an ecosystem to maintain its structure (e.g., species composition) and function (e.g., nutrient cycling) over time, especially in the face of disturbances.
Stability has two main components:
Also known as Species Ecology.
Definition: Autecology is the branch of ecology that studies the interactions of an individual organism or a single species with its environment.
It focuses on the physiological, morphological, and behavioral adaptations of a species to its surroundings.
Also known as Community Ecology.
Definition: Synecology is the branch of ecology that studies the interactions between groups of organisms (like communities or ecosystems) and their environment.
It focuses on the composition, structure, and development of communities.
Biomes are very large ecological areas on the Earth's surface, with fauna and flora (animals and plants) adapting to their environment. They are primarily defined by their climate (temperature and precipitation) and dominant vegetation.
| Biome | Key Characteristics (Climate & Vegetation) |
|---|---|
| Tundra (Arctic and Alpine) | Treeless, low-growing vegetation (mosses, lichens), permafrost (permanently frozen soil), low precipitation, very cold. |
| Taiga (Boreal Forest) | Dominated by coniferous (needle-leaf) trees (pine, spruce, fir), long cold winters, short mild summers. |
| Temperate Deciduous Forest | Dominated by broad-leaf trees that lose their leaves in winter (oak, maple, beech), four distinct seasons, moderate precipitation. |
| Temperate Grassland (Prairie/Steppe) | Dominated by grasses, few trees, fertile soils, often converted to agriculture, cold winters and hot summers. |
| Tropical Rainforest | Highest biodiversity, high rainfall and high temperatures year-round, multi-layered vegetation (canopy, understory). |
| Savanna (Tropical Grassland) | Grasslands with scattered trees, distinct wet and dry seasons, supports large herbivores. |
| Desert (Hot and Cold) | Very low precipitation (less than 25 cm/year), organisms have special adaptations (e.g., succulent plants, nocturnal animals). |
This refers to the range of tolerance an organism has for a particular environmental factor (e.g., temperature, salinity, pH).
Example: A pigeon (eury- species) can be found in many climates, while a penguin (steno- species) is restricted to cold regions.
Proposed by Justus von Liebig, a soil chemist.
Law: The growth and distribution of a species are controlled not by the total resources available, but by the scarcest resource (the "limiting factor").
This is often visualized as a "Liebig's barrel," where the staves (planks) of the barrel represent different nutrients. The barrel can only be filled as high as the shortest stave (the limiting nutrient), no matter how high the other staves are.
An expansion of Liebig's Law, proposed by Victor Shelford.
Law: The success of an organism is determined by a range of conditions (tolerance range) for each environmental factor. There is not only a minimum requirement but also a maximum tolerance.
For any factor (e.g., temperature), an organism has:
These terms describe how species and communities vary in response to environmental gradients.
Definition: An ecocline is a gradual, continuous change in the species composition and environmental factors along a transect or environmental gradient.
It is a gradient of communities, not a sharp boundary.
Definition: An ecotype is a genetically distinct population of a species that is adapted to a specific set of local environmental conditions.
Ecotypes of the same species can look different and have different physiological tolerances, but they can still interbreed (though they may be geographically isolated).
Definition: An ecade (or ecophene) refers to the phenotypic (physical) variations in an organism caused directly by environmental conditions, without any genetic change.
If you take an ecade and move it to a different environment, it (or its offspring) will change to match the new conditions. This is phenotypic plasticity, not genetic evolution.