🐾General Biology II Unit 19 – Ecology and the Biosphere

Key Concepts and Definitions

• Ecology studies the interactions between organisms and their environment at various levels of organization
• Biosphere encompasses all living organisms on Earth and the environments they inhabit
• Ecosystems consist of communities of organisms interacting with each other and their physical environment
• Habitat refers to the physical location where an organism lives and includes both biotic and abiotic factors
• Niche describes an organism's role within an ecosystem, including its interactions with other organisms and its use of resources
• Biodiversity measures the variety of life at all levels, from genes to ecosystems, and plays a crucial role in maintaining ecosystem stability
• Ecological succession is the gradual process by which ecosystems change over time, often following a disturbance

Levels of Ecological Organization

• Organisms are individual living entities that belong to a specific species
• Populations consist of individuals of the same species living in a particular area at a given time
• Communities are assemblages of multiple populations of different species that interact with each other
• Ecosystems encompass both the biotic communities and the abiotic environment in which they exist, including energy flow and nutrient cycling
• Biomes are large, distinct regions characterized by similar climate, vegetation, and animal life (tropical rainforest, tundra)
• The biosphere is the global sum of all ecosystems, encompassing all living organisms and their environments on Earth
  • Includes the atmosphere, hydrosphere, and lithosphere

Biotic and Abiotic Factors

• Biotic factors are the living components of an ecosystem, including all organisms and their interactions
  • Examples of biotic factors include plants, animals, fungi, and microorganisms
• Abiotic factors are the non-living, physical and chemical components of an ecosystem that influence living organisms
  • Temperature, light, water, soil, and atmospheric gases are examples of abiotic factors
• The interaction between biotic and abiotic factors shapes the characteristics and functionality of ecosystems
• Limiting factors are biotic or abiotic factors that constrain the growth, distribution, or abundance of organisms in an ecosystem
  • Examples of limiting factors include water availability in deserts and nutrient availability in aquatic ecosystems
• Organisms adapt to both biotic and abiotic factors in their environment through evolutionary processes
• The tolerance range of an organism determines its ability to survive and reproduce under specific environmental conditions

Energy Flow in Ecosystems

• Primary producers, such as plants and algae, convert solar energy into chemical energy through photosynthesis
• Consumers obtain energy by feeding on other organisms and can be classified as herbivores, carnivores, or omnivores
• Decomposers, such as bacteria and fungi, break down dead organic matter and recycle nutrients back into the ecosystem
• Trophic levels represent the position of an organism in the food chain based on its source of energy (producers, primary consumers, secondary consumers)
• Food chains and food webs illustrate the transfer of energy from one trophic level to another
• Energy pyramids depict the decrease in available energy at each successive trophic level due to energy loss through metabolic processes and heat dissipation
• The 10% rule states that approximately 10% of the energy from one trophic level is transferred to the next, limiting the number of trophic levels in an ecosystem

Biogeochemical Cycles

• Biogeochemical cycles describe the movement of essential elements and compounds between the biotic and abiotic components of an ecosystem
• The water cycle (hydrologic cycle) involves the continuous movement of water through evaporation, transpiration, condensation, precipitation, and surface and groundwater flow
• The carbon cycle encompasses the exchange of carbon among the atmosphere, oceans, terrestrial ecosystems, and Earth's interior
  • Photosynthesis, respiration, decomposition, and combustion are key processes in the carbon cycle
• The nitrogen cycle includes nitrogen fixation, nitrification, denitrification, and ammonification, which convert nitrogen between its various forms
• The phosphorus cycle involves the weathering of rocks, uptake by organisms, and the return of phosphorus to the environment through decomposition and sedimentation
• Human activities, such as fossil fuel combustion and deforestation, can disrupt biogeochemical cycles and lead to environmental issues like climate change and eutrophication

Population Ecology

• Population size refers to the number of individuals of a species in a given area at a specific time
• Population density measures the number of individuals per unit area or volume
• Population distribution describes the spatial arrangement of individuals within a population (clumped, uniform, random)
• Population growth is influenced by factors such as birth rates, death rates, immigration, and emigration
• Exponential growth occurs when a population increases at a constant rate, resulting in a J-shaped curve
• Logistic growth occurs when a population's growth slows down as it approaches the carrying capacity, resulting in an S-shaped curve
• Carrying capacity is the maximum population size that an environment can sustain given the available resources
  • Factors influencing carrying capacity include food availability, space, and competition

Community Interactions

• Interspecific interactions occur between individuals of different species within a community
• Competition is an interaction in which organisms vie for limited resources, leading to reduced growth, survival, or reproduction
  • Competitive exclusion principle states that two species competing for the same resources cannot coexist indefinitely
• Predation is an interaction in which one organism (predator) hunts, kills, and consumes another organism (prey)
  • Predator-prey relationships can lead to population fluctuations and adaptations in both predator and prey species
• Symbiosis is a close and long-term interaction between two different species
  • Mutualism is a symbiotic relationship in which both species benefit (oxpeckers and rhinos)
  • Commensalism is a symbiotic relationship in which one species benefits while the other is unaffected (barnacles and whales)
  • Parasitism is a symbiotic relationship in which one species (parasite) benefits at the expense of the other (host)
• Ecological niche partitioning allows species to coexist by utilizing different resources or habitats within a community

Biomes and Aquatic Ecosystems

• Biomes are large, distinct terrestrial regions characterized by similar climate, vegetation, and animal life
• Terrestrial biomes include tundra, taiga, temperate forests, temperate grasslands, chaparral, deserts, and tropical forests
  • Biome distribution is primarily determined by temperature and precipitation patterns
• Aquatic ecosystems are divided into marine and freshwater ecosystems
  • Marine ecosystems include oceans, coral reefs, and estuaries
  • Freshwater ecosystems include lakes, rivers, streams, and wetlands
• The intertidal zone is the area along the coastline that is exposed during low tide and submerged during high tide, supporting a diverse array of adapted organisms
• Coral reefs are underwater structures composed of coral polyps that support high biodiversity and provide critical habitat for many marine species
• Estuaries are partially enclosed coastal bodies of water where freshwater from rivers and streams mixes with saltwater from the ocean, creating unique and productive ecosystems

Human Impact on the Biosphere

• Habitat destruction, fragmentation, and degradation are major threats to biodiversity caused by human activities such as deforestation, urbanization, and agriculture
• Overexploitation of natural resources, including overfishing and overhunting, can lead to population declines and species extinctions
• Pollution, including air, water, and soil pollution, can have detrimental effects on ecosystems and individual organisms
  • Examples include acid rain, oil spills, and plastic pollution in marine environments
• Climate change, largely driven by human activities such as fossil fuel combustion and deforestation, can alter temperature and precipitation patterns, affecting species distributions and ecosystem functioning
• Invasive species, often introduced by human activities, can disrupt ecosystems by outcompeting native species and altering community dynamics
• Conservation efforts aim to protect and restore ecosystems and biodiversity through measures such as habitat protection, sustainable resource management, and species recovery programs
  • Examples include establishing protected areas, implementing fishing quotas, and captive breeding programs for endangered species