🦉Intro to Ecology Unit 3 – Biomes and Biogeography

Key Concepts and Definitions

• Biome refers to a large ecological area on the earth's surface with distinctive plant and animal communities adapted to the region's physical environment, particularly climate
• Biogeography studies the distribution of species and ecosystems in geographic space and through geological time
• Climate encompasses the long-term average weather patterns and temperature ranges that characterize a specific area
• Latitude, elevation, and proximity to water bodies are key factors influencing the climate and biome distribution across the globe
• Biodiversity describes the variety of life in a particular habitat or ecosystem, including the number of different species and their relative abundance
  • Biodiversity is often used as a measure of the health of an ecosystem
  • High biodiversity is associated with greater ecosystem stability and resilience
• Ecological niche refers to the role and position a species has in its environment, including the resources it consumes, its habitat preferences, and its interactions with other species

Types of Biomes

• Terrestrial biomes are characterized by their predominant vegetation, determined by temperature and precipitation patterns
  • Major terrestrial biomes include tundra, taiga (boreal forest), temperate deciduous forest, temperate grassland, temperate rainforest, desert, tropical savanna, and tropical rainforest
• Aquatic biomes are divided into two main categories: freshwater and marine
  • Freshwater biomes include rivers, streams, lakes, ponds, and wetlands
  • Marine biomes include oceans, coral reefs, estuaries, and coastal zones
• Tundra biome is characterized by low temperatures, short growing seasons, and limited precipitation, supporting hardy vegetation like mosses, lichens, and dwarf shrubs
• Taiga biome, also known as boreal forest, features coniferous trees adapted to cold temperatures and acidic soils (spruces, firs, and pines)
• Temperate deciduous forests have trees that lose their leaves seasonally (maples, oaks, and beeches) and experience distinct seasonal changes
• Temperate grasslands, such as prairies and steppes, are dominated by grasses and have few trees due to limited precipitation and periodic fires

Climate's Influence on Biomes

• Temperature and precipitation patterns are the primary factors determining the distribution of biomes across the globe
  • Temperature affects the rate of evaporation, plant growth, and decomposition
  • Precipitation determines the availability of water for plant growth and influences soil characteristics
• Köppen climate classification system categorizes the world's climates based on temperature and precipitation patterns, providing a framework for understanding biome distribution
• Latitude influences the amount of solar radiation received, resulting in distinct temperature zones (polar, temperate, and tropical)
  • Regions near the equator receive more direct sunlight and have higher temperatures compared to polar regions
• Elevation affects temperature and precipitation, with higher elevations generally experiencing cooler temperatures and increased precipitation
  • Mountainous regions often display altitudinal zonation, where biomes change with increasing elevation
• Ocean currents and proximity to water bodies moderate temperatures and influence precipitation patterns in coastal regions
  • Coastal areas often have milder temperatures and higher humidity compared to inland regions at the same latitude

Biogeography Basics

• Dispersal refers to the movement of individuals or propagules (seeds, spores, or eggs) away from their place of origin, allowing species to colonize new areas
  • Dispersal can occur through various means, such as wind, water, or animal transport
• Vicariance occurs when a population is divided by a geographic barrier (mountain range or river), leading to the formation of separate species over time due to reproductive isolation
• Endemism describes species that are unique to a particular geographic location and found nowhere else in the world
  • Endemic species often evolve in isolation and are particularly vulnerable to extinction due to limited range and specialized adaptations
• Island biogeography theory predicts that larger islands and those closer to the mainland will have higher species richness compared to smaller, more isolated islands
  • The theory also suggests that the number of species on an island represents a dynamic equilibrium between immigration and extinction rates
• Adaptive radiation is the process by which a single ancestral species gives rise to multiple descendant species adapted to different ecological niches
  • Classic examples of adaptive radiation include Darwin's finches in the Galapagos Islands and cichlid fish in the African Great Lakes

Ecological Adaptations

• Adaptations are traits that enhance an organism's ability to survive and reproduce in its environment
  • Adaptations can be morphological (physical features), physiological (internal processes), or behavioral
• Camouflage is a common adaptation that helps organisms blend in with their surroundings, reducing the risk of predation
  • Examples include the white fur of polar bears in the Arctic and the leaf-like appearance of leaf-tailed geckos
• Mimicry occurs when one species evolves to resemble another species, often to deceive predators or prey
  • Batesian mimicry involves a harmless species mimicking a harmful or unpalatable species (monarch and viceroy butterflies)
  • Müllerian mimicry involves two or more harmful species mimicking each other, reinforcing the warning signal to predators
• Physiological adaptations enable organisms to cope with specific environmental conditions
  • Desert plants have adaptations to conserve water, such as reduced leaf surface area, deep root systems, and the ability to store water in their tissues (cacti)
  • Arctic animals have adaptations to retain heat, such as thick fur, insulating fat layers, and countercurrent heat exchange systems (polar bears and penguins)
• Behavioral adaptations involve changes in an organism's actions to increase its chances of survival and reproduction
  • Migration allows animals to take advantage of seasonal resources and avoid unfavorable conditions (birds flying south for the winter)
  • Hibernation is a strategy used by some animals to conserve energy during periods of low food availability and harsh weather conditions (bears and ground squirrels)

Human Impact on Biomes

• Habitat destruction is the primary cause of biodiversity loss worldwide, resulting from land-use changes such as deforestation, urbanization, and agricultural expansion
  • Tropical rainforests are particularly vulnerable, with an estimated 18 million acres lost each year due to logging, cattle ranching, and palm oil plantations
• Fragmentation occurs when habitats are divided into smaller, isolated patches, reducing connectivity and impeding the movement of species
  • Fragmentation can lead to decreased genetic diversity, increased vulnerability to edge effects, and local extinctions
• Overexploitation refers to the unsustainable harvest of natural resources, such as overfishing, poaching, and the illegal wildlife trade
  • Many species, such as sharks, rhinos, and pangolins, are threatened by overexploitation driven by demand for their products
• Climate change, largely driven by human activities, is altering temperature and precipitation patterns, leading to shifts in species distributions and the timing of ecological events (phenology)
  • Rising sea levels and ocean acidification pose significant threats to coastal and marine ecosystems, particularly coral reefs
• Invasive species, often introduced by human activities (shipping or pet trade), can disrupt ecosystems by outcompeting native species and altering habitat structure
  • Notorious examples include the cane toad in Australia and the Burmese python in the Florida Everglades

Conservation Strategies

• Protected areas, such as national parks, wildlife refuges, and marine reserves, are designated to safeguard habitats and species from human disturbance
  • The International Union for Conservation of Nature (IUCN) categorizes protected areas based on their management objectives and level of protection
• Habitat restoration involves the active recovery of degraded or destroyed ecosystems to their natural state
  • Restoration projects can include reforestation, wetland rehabilitation, and coral reef regeneration
• Ex-situ conservation focuses on protecting species outside their natural habitats, such as in zoos, aquariums, and seed banks
  • Captive breeding programs aim to maintain genetic diversity and provide a safety net for critically endangered species
• Community-based conservation engages local communities in the management and protection of their natural resources, promoting sustainable use and equitable benefit-sharing
  • Successful examples include the Namibian conservancy program and the Locally Managed Marine Areas (LMMAs) in the Pacific Islands
• International agreements and conventions, such as the Convention on Biological Diversity (CBD) and the Convention on International Trade in Endangered Species (CITES), provide frameworks for global cooperation in biodiversity conservation
  • These agreements set targets, establish guidelines, and regulate the trade of endangered species to minimize threats to biodiversity

Case Studies and Examples

• The Amazon rainforest, the world's largest tropical rainforest, is home to an estimated 10% of Earth's known species
  • Deforestation driven by cattle ranching, soybean cultivation, and logging threatens the Amazon's biodiversity and its critical role in regulating the global climate
• The Great Barrier Reef, the world's largest coral reef system, is experiencing severe coral bleaching and mortality due to rising ocean temperatures and acidification
  • Efforts to protect the reef include the establishment of marine protected areas, water quality improvement, and the development of heat-resistant coral strains
• The Serengeti-Mara ecosystem in East Africa is renowned for its annual wildebeest migration, one of the largest terrestrial mammal migrations in the world
  • The ecosystem faces challenges from poaching, habitat fragmentation, and increasing human-wildlife conflicts in the surrounding areas
• The island of Madagascar is a biodiversity hotspot, with over 90% of its wildlife found nowhere else on Earth
  • Madagascar's unique flora and fauna are threatened by deforestation, slash-and-burn agriculture, and the illegal pet trade
• The Arctic tundra is experiencing rapid warming, leading to the thawing of permafrost, changes in vegetation composition, and alterations in the distribution and behavior of iconic species like the polar bear
  • Conservation efforts in the Arctic focus on mitigating the impacts of climate change, protecting critical habitats, and supporting the livelihoods of indigenous communities