❤️AP Bio Unit 9 – Ecology

Key Concepts and Definitions

• Ecology studies the interactions between organisms and their environment at various levels of organization
• Biotic factors include living components of an ecosystem (plants, animals, microorganisms)
• Abiotic factors encompass non-living components (temperature, light, water, soil)
• Habitat refers to the physical environment where an organism lives and interacts with biotic and abiotic factors
• Niche describes an organism's role within an ecosystem, including its interactions with other species and resource utilization
• Ecosystem consists of all living organisms and non-living components in a given area, interacting as a functional unit
• Biome represents a large geographical area characterized by distinct climate, flora, and fauna (tropical rainforest, tundra)

Levels of Ecological Organization

• Organism is an individual living entity capable of independently carrying out life processes
• Population comprises individuals of the same species living in a specific area at a given time
• Community includes populations of different species interacting within a shared environment
• Ecosystem encompasses all biotic and abiotic components in an area, along with their interactions and energy flow
• Biosphere is the global ecological system integrating all living organisms and their relationships on Earth
• Ecotone represents a transition zone between two distinct ecosystems (forest edge, intertidal zone)
• Ecocline describes a gradual change in environmental conditions and species composition across an ecological gradient

Interactions Within Ecosystems

• Predation occurs when one organism (predator) hunts and consumes another (prey) for energy and nutrients
  • Predator-prey relationships can influence population dynamics and shape community structure
• Competition arises when organisms vie for limited resources, such as food, water, or space
  • Intraspecific competition involves individuals of the same species
  • Interspecific competition occurs between different species
• Symbiosis describes close and long-term interactions between organisms of different species
  • Mutualism benefits both species involved (pollination, nitrogen fixation in legume-rhizobia associations)
  • Commensalism benefits one species without significantly affecting the other (barnacles on whales, epiphytes on trees)
  • Parasitism involves one species (parasite) deriving nutrients from and causing harm to another (host)
• Herbivory refers to animals consuming plants or algae for sustenance
• Facilitation happens when one species enhances the survival, growth, or reproduction of another

Energy Flow and Nutrient Cycles

• Primary producers (autotrophs) convert solar energy into chemical energy through photosynthesis, forming the base of most ecosystems
• Consumers (heterotrophs) obtain energy by feeding on other organisms
  • Primary consumers (herbivores) feed on plants or algae
  • Secondary consumers (carnivores) feed on other animals
  • Omnivores consume both plants and animals
• Decomposers break down dead organic matter, releasing nutrients back into the ecosystem
• Trophic levels represent the position of an organism in the food chain based on its energy source
• Food web illustrates the complex feeding relationships within an ecosystem, connecting multiple food chains
• Energy flows through ecosystems, with some energy lost as heat at each trophic level due to the second law of thermodynamics
• Biogeochemical cycles (carbon, nitrogen, phosphorus, water) involve the movement and transformation of essential elements through biotic and abiotic components of ecosystems

Population Dynamics

• Population size is the number of individuals of a species in a given area at a specific time
• Population density refers to the number of individuals per unit area or volume
• Dispersion patterns describe the spatial arrangement of individuals within a population (clumped, uniform, random)
• Demography studies the structure and dynamics of populations, including age distribution, sex ratio, and life history traits
• Exponential growth occurs when a population increases at a constant rate, resulting in a J-shaped curve
• Logistic growth happens when a population's growth slows down as it approaches the carrying capacity, forming an S-shaped curve
• Carrying capacity is the maximum population size an environment can sustain given available resources
• Density-dependent factors (competition, predation, disease) have a greater impact on population growth as density increases
• Density-independent factors (natural disasters, climate) affect populations regardless of their density

Community Ecology

• Species richness is the number of different species present in a community
• Species evenness refers to the relative abundance of each species within a community
• Species diversity combines both richness and evenness, providing a comprehensive measure of community composition
• Ecological succession describes the gradual and predictable changes in species composition over time
  • Primary succession begins in a newly formed, uninhabited environment (volcanic island, glacial retreat)
  • Secondary succession occurs in a previously inhabited area following a disturbance (forest fire, abandoned agricultural land)
• Keystone species have a disproportionately large influence on community structure and function relative to their abundance (sea otters, wolves)
• Foundation species create and maintain habitats that support many other species (coral reefs, kelp forests)
• Invasive species are non-native organisms that cause ecological or economic harm in a new environment
• Ecological niche partitioning allows multiple species to coexist by dividing resources and habitat use

Biodiversity and Conservation

• Biodiversity encompasses the variety of life at all levels, from genes to ecosystems
• Genetic diversity refers to the variation in genetic material within a species or population
• Species diversity is the number and relative abundance of different species in a given area
• Ecosystem diversity describes the variety of ecosystems within a region or across the globe
• Biodiversity hotspots are areas with exceptionally high species richness and endemism, often threatened by habitat loss
• Endemism refers to species that are unique to a specific geographic location and found nowhere else
• Habitat fragmentation divides contiguous habitats into smaller, isolated patches, reducing connectivity and biodiversity
• Extinction occurs when the last individual of a species dies, and the species ceases to exist
• Conservation biology aims to protect and restore biodiversity through scientific research, management, and policy
  • In-situ conservation protects species and habitats in their natural environment (national parks, wildlife reserves)
  • Ex-situ conservation maintains species outside their natural habitats (zoos, botanical gardens, seed banks)

Human Impact on Ecosystems

• Habitat destruction is the primary cause of biodiversity loss, resulting from deforestation, urbanization, and agricultural expansion
• Overexploitation involves the unsustainable harvest of natural resources (overfishing, poaching, logging)
• Pollution degrades ecosystems through the introduction of harmful substances (pesticides, plastics, greenhouse gases)
• Climate change, largely driven by human activities, alters temperature, precipitation patterns, and sea levels, affecting species distributions and ecosystem functioning
• Invasive species, often introduced by human activities, can disrupt native communities and cause ecological and economic damage
• Ecological restoration attempts to repair degraded ecosystems and restore biodiversity and ecosystem services
• Sustainable development seeks to balance economic growth, social well-being, and environmental protection
• Ecosystem services are the benefits humans derive from ecosystems (food production, water purification, carbon sequestration, recreation)