Principles of Ecology

Principles of Ecology

The Biosphere

• The biosphere is described as the zone of life on Earth.

• Two primary categories of biomes:

  • Terrestrial Biomes

  • Aquatic Zones

Terrestrial Biomes

Key Concepts

3.1 Characterization of Terrestrial Biomes

• Terrestrial biomes are characterized primarily by dominant vegetation forms.

  • Plants are categorized based on growth forms rather than taxonomic relationships.

Learning Objectives:

• Explain why plant growth forms are used to categorize terrestrial biomes.

• Describe how global patterns of precipitation and temperature influence the location of terrestrial biomes.

• Evaluate the impact of human activities on the distribution of biomes.

• Describe the nine major terrestrial biomes.

Human Activities and Biomes

• Human activity can significantly impact the distribution and health of various biomes:

  • Logging, agriculture, and land conversion contribute to habitat loss.

  • Example: About 50% of tropical rainforest biome has been altered, which complicates recovery due to nutrient-poor soils.

  • Nutrients are locked in vegetation above ground, resulting in decreased soil fertility after deforestation.

Aquatic Ecosystems

3.2 Freshwater Ecosystems

• Biological zones in freshwater ecosystems, such as rivers and lakes, depend on factors including:

  • Velocity

  • Depth

  • Temperature

  • Clarity

  • Chemistry

Learning Objectives:

• Explain how these factors affect streams and rivers of different orders, and lakes.

3.3 Marine Biological Zones

• Marine environments are determined by:

  • Ocean depth

  • Light availability

  • Bottom substrate stability

Learning Objectives:

• Explain how depth and substrate types influence aquatic life.

• Analyze how energy sources and food availability affect marine organism populations.

Growth Forms and Environmental Indicators

• Vegetation (plants) serves as a long-lasting indicator of climatic conditions in specific areas.

• Different growth forms reveal specific environmental adaptations:

  • For example, sclerophyllous shrubs grow in seasonally dry climates, demonstrating adaptations to water storage.

Examples of Plant Growth Forms

Figure 3.3 Plant Growth Forms (Part 1) and (Part 2)

• Growth forms illustrate environments and characteristics:

  • Sclerophyllous Shrubs: Adapted to dry/moist, warm/cool environments.

  • Deciduous Trees: Shed leaves, indicating adaptation to seasonal changes.

  • Succulent Plants: Store water, critical for survival in arid conditions like cacti and euphorbs.

Major Terrestrial Biomes

• Tropical Rainforests: Located near the equator, characterized by high biodiversity and annual precipitation exceeding 2000 mm.

  • Example: Yanganbi, Zaire 0°, 487 m with average annual temperature 24.6°C.

  • High biomass and species diversity; altered significantly by human practices.

• Tropical Seasonal Forests and Savannas: Found between tropical regions around 10° to 23.5° N/S with dry seasons.

  • Comprise dry forests and savannas with grasses and scattered trees.

  • Example: Coxim, Brazil 18°S, 287 m with average annual temperature 24.5°C, total annual precipitation 1493 mm.

• Hot Deserts: Characterized by high temperatures and low water availability.

  • Examples include Sonoran Desert, adapted plant species like cacti that store water.

• Temperate Grasslands: Maintained by fires and large herbivores; high soil fertility but heavily impacted by agriculture.

  • Example: Denison, Nebraska, USA, with average annual temperature 9.1°C and total annual precipitation 727 mm.

• Temperate Deciduous Forests: Significant for agriculture; species diversity lower than tropical forests but still notable (approx 3,000 species in North America).

  • Example: Wellsboro, Pennsylvania, USA, with average annual temperature 7.6°C and total annual precipitation 848 mm.

• Boreal Forests (Taiga): Found mostly in Russia and Northern America; conifers dominant, limited decomposition due to cold and wet conditions.

  • Example: Fort Simpson, Northwest Territories, Canada, with average annual temperature -4.6°C and total annual precipitation 333 mm.

• Tundra: Located above 65° latitude in Arctic conditions; characterized by permafrost, low-growing vegetation.

  • Example: Olenek, Russia, with average annual temperature -14.3°C and total annual precipitation 184 mm.

Mountain Biological Zones

• On mountains, biomes are organized by elevation:

  • Higher elevation tends to mimic other biomes such as grasslands, tundra, and boreal forests.

  • Different temperature and precipitation conditions at various elevations lead to distinct zonation.

• Example of elevation-related zones:

  • Alpine Zone: influenced heavily by temperature and elevation.

Understanding Stream Orders

Stream Characteristics

• Streams and rivers are categorized as lotic systems, originating at high elevations with first-order streams.

  • First-order streams merge to form higher-order streams, leading to large rivers (6th-order streams).

• Riparian Zones: Riparian vegetation provides essential organic matter and shade, critical for stream ecology.

Impact of Human Activities

Human Impacts on Ecosystems

• Significant human impacts on aquatic ecosystems include:

  • Sedimentation from agricultural practices affecting coral reefs and stream habitats.

  • Sewage and industrial waste as pollutants.

  • Deforestation and land conversion leading to habitat loss.

Questions to Consider:

• Are there associations between specific biomes and latitudinal gradients?

• Which biomes are more impacted by human activities? Why?

• Strategies for mitigating human impacts include improved land management practices, pollution reduction techniques, and habitat restoration initiatives.

Conclusion

• Understanding the dynamics and interconnections of biomes is essential in forming strategies around conservation and sustainable resource management.

• Addressing the complexities of human-environment interactions remains critical in preserving ecological integrity.