Lesson 3 Ecosystem and Biomes

Core Concepts & Definitions

  • Ecosystem: A community of living organisms (biotic factors) interacting with the non-living components (abiotic factors) of their environment.

  • Example: A fish pond where fish, plants, water, and soil interact; or a forest where trees and animals live and interact.

  • Biome: A large-scale region of the Earth with a distinct climate, flora, and fauna. It is a collection of many similar ecosystems (e.g., deserts, grasslands, tropical forests).

  • Key Distinctions:

  • An ecosystem is smaller than a biome because a biome is distributed throughout the Earth.

  • A biome is strongly influenced by physical climatic conditions (such as snow, temperature, rainfall), whereas an ecosystem is not solely defined by them at a global scale.

Major Terrestrial Biomes & Limiting Factors

1. Tundra

  • Characteristics:

  • Coldest of all biomes.

  • Defined by a layer of permafrost (permanently frozen soil) that prevents trees from growing.

  • Vegetation limited to low-growing plants like mosses, lichens, and shrubs.

  • Animals are adapted to extreme cold (e.g., thick fur, hibernation).

  • Limiting Factors:

  • Temperature: Extremely cold temperatures limit the types of plants and animals that can survive.

  • Permafrost: Permanently frozen ground prevents large trees from establishing deep root systems.

  • Nutrient-Poor Soil: Slow decomposition rate in the cold environment limits available nutrients.

2. Temperate Forest

  • Characteristics:

  • Four Distinct Seasons: Experiences hot summers, cold winters, and moderate spring and autumn seasons.

  • Rich, Fertile Soil: Soil is rich in nutrients due to the decomposition of fallen leaves and organic matter.

  • Dominated by Deciduous Trees: Primary plant life includes broadleaf trees like oak, maple, and beech that lose their leaves in autumn.

  • Limiting Factors:

  • Seasonal Temperature Changes: Plants and animals must adapt to cold winters and warm summers.

  • Sunlight: Dense canopy blocks sunlight from reaching the forest floor, limiting growth of smaller plants.

  • Human Impact: Deforestation, pollution (such as acid rain), and invasive species limit health and expansion.

3. Tropical Rainforest

  • Characteristics:

  • High rainfall and humidity all year round.

  • The most biodiverse biome on Earth.

  • Philippine Tropical Rainforest Types:

  • Dipterocarp Forest:

  • Most common forest type in the Philippines.

  • Dominated by species from the Dipterocarpaceae family, known for commercially valuable timber (e.g., Yakal - Shorea astylosa, Philippine Red Lauan - Shorea negrosensis).

  • Location: Widespread throughout the Philippines, notably in Mindanao and Palawan.

  • Molave Forest:

  • Found in areas with a distinct dry season (dry-type Dipterocarp forests).

  • Trees are typically smaller and have a gnarled, crooked appearance (e.g., Molave - Vitex parviflora, Narra - Pterocarpus indicus).

  • Location: Widespread throughout the Philippines, notably in Mindanao and Palawan.

  • Pine Forest:

  • Found in cooler, mountainous regions with higher elevations (above 1000 m).

  • Dominated by pine trees with long, needle-like leaves to survive drier, cooler conditions (e.g., Benguet Pine).

  • Location: Primarily in the Cordillera Administrative Region (CAR), including Baguio, Benguet, and Mountain Province.

  • Mossy Forest:

  • Found at the highest elevations of mountains, often shrouded in constant mist and clouds.

  • Trees are stunted and gnarled, with branches and trunks covered in thick layers of mosses, ferns, and orchids.

  • Home to rare and endemic plants and animals (e.g., pitcher plants, specific frogs).

  • Location: High-altitude peaks like Mount Apo (Davao) and Mount Pulag (Benguet).

  • Limiting Factors:

  • Light: Very little sunlight reaches the lower layers (understory and forest floor), limiting plant growth.

  • Nutrients: Intense rainfall quickly strips nutrients from the soil.

  • Space: High competition for physical space.

4. Grassland

  • Characteristics:

  • Dominated by grasses and non-woody plants.

  • Receives enough rainfall to prevent desert formation, but not enough to support a forest.

  • Often created or maintained by human activities like farming and burning.

  • Limiting Factors:

  • Rainfall: Not enough rain to support forest growth.

  • Fire: Natural and human-caused fires limit the growth of woody plants.

  • Grazing: Presence of large grazing animals prevents the establishment of trees and shrubs.

5. Desert

  • Characteristics:

  • Defined by extremely low precipitation (less than 50 cm of rain per year).

  • Plants have unique adaptations to conserve water (small leaves, deep root systems).

  • Hot Deserts: High daytime temperatures, cold nights (e.g., Sahara Desert).

  • Cold Deserts: Very cold winters (e.g., Gobi Desert).

  • Limiting Factors:

  • Water Availability: Primary limiting factor is extremely low rainfall.

  • Extreme Temperatures: Very hot daytime and cold nighttime temperatures.

  • Nutrient-Poor Soil: Soils lack organic matter needed to support diverse plant life.

Aquatic Ecosystems

Ecosystems found in a body of water. Vital in the Philippines as an archipelago for food, livelihoods, coastal protection, and national identity.

  • Freshwater Ecosystems: Low salt content (e.g., rivers, lakes, ponds).

  • Marine Ecosystems: High salt content (e.g., oceans, coral reefs).

Coastal & Marine Ecosystems

1. Coral Reefs

  • Characteristics:

  • "Rainforests of the sea" due to immense biodiversity.

  • Created by tiny marine animals (corals) in a symbiotic relationship with algae.

  • Highly sensitive to pollution, overfishing, and climate change.

  • Limiting Factors:

  • Water Temperature: Highly sensitive to changes in water temperature.

  • Ocean Acidity: Increased acidity from dissolved carbon dioxide makes it difficult for corals to build skeletons.

2. Mangrove Forest

  • Characteristics:

  • Unique forests growing in salty coastal waters in the intertidal zone.

  • Trees have specialized root systems to filter salt and breathe in low-oxygen soil.

  • Ecological Role: Act as natural storm barriers against typhoons/tsunamis; serve as nurseries for fish, crabs, and shellfish.

  • Location: Widespread along the coasts of Palawan, Bohol, and other islands.

  • Limiting Factors:

  • Salinity: Ability to tolerate and filter salt.

  • Tidal Action: Daily tides affect oxygen levels and can wash away seedlings.

3. Seagrass Beds

  • Characteristics:

  • Underwater meadows of flowering plants (not seaweed).

  • Found in shallow, clear, sheltered coastal waters.

  • Ecological Role: Provide food for endangered marine animals (dugongs, sea turtles); serve as habitat/nursery grounds for juvenile fish and invertebrates.

  • Location: Throughout the Philippine archipelago, particularly in Palawan and Mindanao.

  • Limiting Factors:

  • Water Clarity: Requires clear water for sunlight penetration for photosynthesis.

  • Nutrient Levels: Excess nutrients from pollution lead to algae blooms that block sunlight.

4. Marine Zonation Limiting Factors

  • Light: Deeper water receives less sunlight, limiting photosynthesis.

  • Pressure & Temperature: Water pressure increases with depth, while temperature drops due to lack of sunlight penetration.

Freshwater Ecosystems

  • Characteristics: Low salt content; sourced from groundwater, rainfall, or snowmelt in mountains. Essential for drinking water, agriculture, and industry.

  • Philippine Examples:

  • Lakes: Laguna de Bay (largest lake), Taal Lake, Lake Lanao.

  • Rivers: Cagayan River (longest river), Pasig River.

  • Limiting Factors:

  • Pollution: Runoff from farms and urban areas introducing chemicals and excess nutrients.

  • Dissolved Oxygen: Oxygen levels can be low in stagnant or polluted water.