Biomes and Ecosystems: A Comprehensive Overview
Biomes: Earth’s Diverse Habitats
Biomes are distinct regions of Earth, each characterized by a unique set of plant and animal communities. These communities share a common structure, function, and development pattern, all directly influenced by the prevailing climate. Biomes are broadly categorized into two main types: terrestrial and aquatic.
1. Terrestrial Biomes
Terrestrial biomes are land-based ecosystems. Within these biomes, vertical and horizontal zones can exist, depending on factors like altitude and proximity to water. For instance, a forest can exhibit vertical stratification:
- Hypogeum Layer: Organisms thriving in the soil.
- Cryptogamic Layer: Mosses and lichens.
- Herbaceous Layer: Low-lying woody plants.
- Shrub Layer: Woody plants up to 5 meters tall.
- Tree Layer: Trees exceeding 5 meters in height.
Horizontal variations can also arise due to proximity to water and altitude. Key terrestrial biomes include:
- Tundra: Polar regions with frigid winters, brief cool summers, and permafrost supporting mosses and lichens.
- Taiga: Cold regions with short summers, long winters, and coniferous forests.
- Steppe/Meadow: Grasslands with significant temperature fluctuations and low precipitation.
- Mediterranean Forest: Dry summers, low rainfall, and forests of pines and oaks.
- Temperate Deciduous Forest: Mild temperatures, ample moisture, and deciduous and coniferous trees.
- Desert: Arid regions with minimal rainfall, extreme temperature variations, and xerophytic plants.
- Rainforest: Warm, humid climate with near-daily rainfall and high biodiversity.
2. Aquatic Biomes
Aquatic biomes are water-based ecosystems, where the distribution of organisms depends on factors like salinity and light. Marine organisms can be classified as:
- Plankton: Organisms suspended in water.
- Phytoplankton: Photosynthetic organisms.
- Zooplankton: Heterotrophic plankton.
- Nekton: Actively swimming organisms in pelagic zones.
- Benthos: Organisms living on or in the seabed.
- Sessile: Fixed organisms like bivalves.
- Vagile: Organisms with limited movement like starfish.
- Demersal: Organisms swimming near the bottom like cephalopods.
A climax plant community represents a stable state in equilibrium with the environment, marking the final stage of ecological succession.
Marine and Freshwater Ecosystems
1. Inland Water Ecosystems
Freshwater biomes found on continents with low salinity.
2. Lake Ecosystems
Stagnant water ecosystems with two distinct layers:
- Epilimnion: Warmer upper layer.
- Hypolimnion: Colder bottom layer.
Based on nutrient content, lakes can be:
- Oligotrophic: Low nutrient and plankton levels.
- Eutrophic: High nutrient and plankton levels.
3. River Ecosystems
Flowing water systems with a horizontal transport of nutrients, creating a nutrient spiral.
4. Wetland Ecosystems
Dominated by helophytes (e.g., reeds) and macrophytes (partially or fully submerged plants). Slower-moving water supports neuston (e.g., duckweed), while periphyton organisms attach to submerged surfaces.
5. Soil Ecosystems
Soil ecosystems have low biomass but high importance. Bacteria and fungi are dominant groups, while soil fauna significantly influence soil properties like porosity.
Ecological Succession
Ecological succession is a continuous, directional, and seasonal process of colonization and extinction of species in an area. Types of succession include:
- Degradative Succession: Decomposition of dead organic matter by microorganisms and detritivores.
- Allogenic Succession: Species replacement due to changes in the abiotic environment (e.g., desiccation).
- Autogenic Succession: Species replacement due to vegetation altering soil conditions and resources.
- Primary Succession: Colonization of a previously unvegetated area (e.g., sand dunes).
- Secondary Succession: Recolonization of an area where vegetation has been partially or fully removed (e.g., after a fire).