Biomes and Biosphere Study Guide
Biomes and Biosphere Overview
Goals:
Understand what is a Biome.
Describe different terrestrial and aquatic biomes.
Describe where they are found and why (related to global and regional climatic patterns).
Definition of Biomes
Biomes are large-scale biological communities shaped by the physical environment, particularly temperature and precipitation variation.
Named after the dominant vegetation visible.
Include all plants, animals, and microbes.
Classification into three main categories:
Terrestrial
Marine
Freshwater
Source: Wikimedia Commons
Latitude Patterns of Biomes
Biomes follow latitude patterns:
Tropical: 0° to 23.5°
Subtropical: 23.5° to 35°
Temperate: 35° to 55°
Subpolar: 55° to 66.5°
Polar: 66.5° to 90°
Same zones occur in the southern hemisphere.
Biomes referred to as – Latitude + habitat (e.g., tropical rainforest, temperate grasslands).
Characteristics of Terrestrial Biomes
Key characteristics:
Sunlight and temperature.
Precipitation.
Soil and nutrient levels.
Living organisms.
Importance of plants:
Plants are immobile and must cope with environmental extremes and biological pressures to occupy a site long-term.
Biomes are based on similarities in morphological responses of organisms to the physical environment, not taxonomic similarities.
Vegetation and Climate Interaction
How land affects physical climate:
Presence of vegetation affects solar radiation reaching the soil.
Albedo:
Capacity of land surface to reflect solar radiation.
Dark forests (lower albedo) absorb more than grasslands.
Deserts have about 40% albedo, while snow has high albedo.
Consequences of snow melting include changes in shading, cooling, and air moisture (transpiration and precipitation).
Aquatic Biomes
Characterized by:
Salinity (distance to shore).
Depth (light availability).
Temperature.
Current and stratification.
Substrate (sand, rocks, reef).
Dissolved minerals (pH).
Types of aquatic biomes:
Saltwater.
Freshwater.
Estuarine/brackish water.
Tropical Biome
Tropical Rainforests
Location: 0° to 10° latitude.
Annual precipitation greater than 200 cm.
No seasonal changes.
Only 6% of total land surface, yet high biomass and diversity (about 50% of Earth’s species).
Flora includes broadleaved evergreen and deciduous trees and epiphytes.
Tropical Forest Structure
Vertical structure consists of five major layers:
Emergent Layer:
Few species taller than canopy.
Canopy:
Crowns of trees providing maximum photosynthesis, high diversity (plants and animals), characterized by 'Crown Shyness.'
Understory:
Shade-tolerant species, including climbing vines and epiphytes.
Shrubs:
Shade-tolerant, large leaves with waxy coverings.
Forest Floor:
Maximum decomposition, recycling of nutrients, little sunlight, buttress roots.
Threats to Tropical Rainforests
Highly threatened due to logging and industrial agriculture.
Diverse ecological communities with few individuals of each species make them highly vulnerable to extinction.
Over half of tropical rainforest biome has been altered; soil is often nutrient-poor due to leaching of Al and Fe, and recovery is uncertain.
Tropical Savannas
Location: Between 10° and 23.5° N and S latitudes.
Characterized by lower water availability during wet seasons, leading to shorter trees, deciduous species, and dominance of grasses and shrubs.
Key factors promoting savanna growth:
Fires (natural or human-induced).
Presence of keystone species (e.g., large herbivores like wildebeests, zebras, elephants).
Seasonal flooding in river floodplains promotes savanna ecosystem.
Habitat loss due to conversion to agriculture and pastureland.
Climate Zones and Political Map
Political map of the world indicates various climate zones:
Polar and subpolar zone
Temperate zone
Subtropical zone
Tropical zone
Subtropical Deserts
Generally found around high-pressure zones at latitudes of 30° N and S.
Characterized by:
Low water availability.
Sparse vegetation and animal populations.
Common plant adaptations include stem succulence (cacti and euphorbs).
Desertification is a concern due to human activities such as overcultivation and poor irrigation practices.
Plant Adaptations in Desert Biomes
Adaptations for water conservation include:
Tiny leaves or no leaves.
Green stem for photosynthesis.
Succulent tissues for water storage.
Deep roots in trees and shallow roots in cacti.
Hairy leaves trap moisture.
Examples:
Cactus species exhibit adaptations that allow them to survive harsh conditions by minimalizing water loss.
Human Impacts on Desert Biomes
Increasing use of deserts for agriculture leads to soil salinization.
Desertification degrades arid, semi-arid, and dry sub-humid areas, leading to loss of soil productivity and vegetative cover.
Temperate Biomes
Temperate Grasslands
Examples include Great Plains and Prairie found between 30° and 50° latitude.
Characteristics include:
Seasonal temperature variation with warm, moist summers and cold, dry winters.
Dominated by grasses maintained by regular fires and large herbivores (e.g., bison).
Adaptations include grasses growing more roots than stems or leaves to survive dry conditions, leading to high soil fertility.
Human Exploitation of Temperate Grasslands
Converted to agriculture for crops like wheat and corn.
Overgrazing can lead to desertification and grassland degradation.
Temperate Forests
Occur at 30° to 50° N on continental edges, with high rainfall.
Species diversity is lower than in tropical rainforests.
Types of temperate forests:
Deciduous
Evergreen
Soils are generally fertile.
Notable decrease in old-growth forests.
Regrowth seen as agriculture shifts to tropical regions, leading to changes in species composition due to invasive species.
Mediterranean Biomes
Characterized by hot, dry summers and cool, wet winters.
Nutrient-poor soils; suitable for specific crops like grapes and olives.
Boreal Forests (Taiga)
Located between 50° and 65° N; impacted significantly by climate change.
Evergreen coniferous trees dominate with a low species diversity.
Cold, wet conditions limit decomposition, leading to high organic matter in soils.
Forest fires can occur during summer droughts.
Tundra Biome
Found above 65° latitude, primarily in the Arctic.
Characterized by cold temperatures, low precipitation, and a short summer (1-2 months).
Vegetation includes sedges, grasses, low-growing shrubs, lichens, and mosses, primarily reproducing asexually due to short growing seasons.
Aquatic Biomes Overview
Marine Biomes
Types:
Open ocean
Estuaries
Coastal waters
Intertidal
Neritic (reefs and kelps)
Salt marshes
Mangroves
Freshwater Biomes
Types:
Rivers
Lakes
Ponds
Wetlands
Characteristics of Aquatic Biomes
Salinity (marine versus freshwater).
Depth impacts light absorption and visibility.
Temperature influences stratification patterns in water bodies.
Oxygen content relies on temperature, photosynthesis, and decomposers.
Ocean Biome Structure
Zones:
Intertidal and Neritic zones are the most productive.
Photic zone supports photosynthesis, while Aphotic zones lack light.
Abyssal zones represent the deep ocean, with depths reaching 11,000m.
Wetland Biomes
Transition zones between aquatic and terrestrial ecosystems.
Cover approximately 6% of Earth's surface, classified based on vegetation type and water source affecting pH and plant growth.
Mangroves are key due to their biodiversity support, providing nursery grounds and habitat.
Summary of Freshwater Biomes
Glaciers and underground reservoirs represent most freshwater.
Freshwater is crucial for connecting terrestrial and marine systems, processing chemical elements and transporting them to oceans.
Classification into Lentic (non-flowing) and Lotic (flowing) waters.
This thoroughly structured guide covers essential biome characteristics, climatic influences, and key interactions between biomes and human activity, making it a comprehensive resource for studying the biomes and biosphere.