Ecology
The study of the interactions among living organisms and with their environment, including relationships between organisms of the same species and also between different species
Organism
An individual living entity that can act independently and perform life processes
Population
A group of interbreeding organisms of the same species living in a specific area at the same time
Community
The different species within an area and their interactions
Biome
A large community of plants and animals that occupies a distinct region defined by its climate and dominant vegetation
Ecosystem
Composed of all the biotic (living) and abiotic (non-living) components in an area and their interactions
Biosphere
The global sum of all ecosystems, encompassing all life on Earth and their environments
Niche
The role or position that an organism occupies within an ecosystem, including how it meets its needs for nutrients, shelter, reproduction, and its part in the energy flow
Habitat
The natural environment where an organism lives and can find food, shelter, and mates
Intraspecific interactions
Interactions that occur between individuals of the same species, often involving competition for resources
Interspecific interactions
Interactions between different species, including predation, parasitism, herbivory, competition, and symbiosis
Biotic factors
The living components of an ecosystem, such as plants, animals, and microorganisms
Abiotic factors
The non-living components of an ecosystem, such as temperature, water, and soil
Biogeochemical cycles
The pathways by which essential elements are recycled through the biosphere, including the water, carbon, nitrogen, and phosphorus cycles
Water cycle
Describes the continuous movement of water within the Earth and atmosphere, including evaporation, condensation, and precipitation
Carbon cycle
Involves the movement of carbon through the atmosphere, living organisms, and the Earth, crucially involving processes like photosynthesis and respiration
Nitrogen cycle
Describes how nitrogen is fixed into forms usable by living organisms, primarily through the action of bacteria, and how it cycles through the environment
Phosphorus cycle
The cycle in which phosphorus moves through the lithosphere, hydrosphere, and biosphere, essential for DNA and energy transfer in living organisms
Eutrophication
A process whereby nutrient runoff (e.g., from fertilizers) causes the excessive growth of microorganisms, depleting dissolved oxygen levels and harming aquatic ecosystems
Predation
An interaction where one organism (predator) hunts and kills another (prey) for food
Herbivory
The consumption of plants by animals
Mechanical/chemical defenses
Physical structures or chemical compounds that protect organisms from predators
Camouflage
An adaptation that allows organisms to blend in with their surroundings to avoid detection by predators
Aposematic coloration
Bright, warning colors that signal to predators that an organism is toxic or unpalatable
Batesian mimicry
A harmless species mimics a harmful one
Müllerian mimicry
Two or more harmful species evolve to look alike, reinforcing predator avoidance
Competitive exclusion principle
The concept that two species competing for the same resources cannot coexist if other ecological factors remain constant
Resource partitioning
The division of resources among species to reduce competition
Character displacement
Evolutionary changes that occur when two similar species inhabit the same environment, leading to differences in characteristics
Commensalism
Symbiotic relationship where one species benefits, the other is neither helped nor harmed
Mutualism
Symbiotic relationship where both species benefit
Parasitism
Symbiotic relationship where one species benefits at the expense of the other
Species richness
The number of different species in a community
Species diversity
A measure that takes into account both the number of species and the evenness of their populations in a community
Diversity index
A quantitative measure reflecting the diversity of species in a community
Keystone species
A species that has a disproportionately large effect on its environment relative to its abundance
Invasive species
Non-native species that spread widely and cause harm to the environment, economy, or human health
Primary succession
The colonization of barren environments by living organisms
Secondary succession
The process of ecological recovery following a disturbance in an environment where life previously existed
Climax community
A stable and mature community that has reached the final stage of ecological succession
Autotrophs/producers
Organisms that produce their own food through processes like photosynthesis
Heterotrophs/consumers
Organisms that consume other organisms for energy
Food chain
A linear sequence of organisms where nutrients and energy pass from one organism to the next
Food web
A complex network of interconnected food chains within an ecological community
Trophic level
The position an organism occupies in a food chain
Ecological pyramids
Graphical representations that show the distribution of energy, biomass, or numbers of organisms at each trophic level
10% rule
The principle that only about 10% of the energy at one trophic level is transferred to the next level
Biomagnification
The increasing concentration of toxins in organisms at higher trophic levels in a food chain
Climate change
Long-term changes in temperature, precipitation, and other atmospheric conditions on Earth
Greenhouse effect
The trapping of heat in the Earth's atmosphere by greenhouse gases, leading to a warming effect
Demography
The statistical study of populations, including their size, structure, and distribution
Population size (N)
The total number of individuals in a population
Population density
The number of individuals within a specific area or volume
Mark and recapture
A method used to estimate population size by capturing, marking, releasing, and then recapturing individuals
Uniform species dispersion
Individuals are evenly spaced
Random species dispersion
Individuals are spread randomly
Clumped species dispersion
Individuals are grouped in patches
Density-dependent factors
Factors that affect population size based on population density (e.g., competition)
Density-independent factors
Factors that affect population size regardless of density (e.g., natural disasters)
Exponential growth
Population growth under ideal conditions with an accelerating rate
Logistic growth
Population growth that slows as it approaches the carrying capacity
Population growth rate
The change in population size over time
Death rate and birth rate
The number of deaths and births per 1,000 individuals per year
Zero population growth
When the birth rate equals the death rate, leading to a stable population size
Biotic potential
The maximum reproductive capacity of an organism under optimal environmental conditions
Carrying capacity
The maximum number of individuals of a species that an environment can support indefinitely
J-curve growth graph
Graph that represents exponential growth
S-curve growth graph
Graph that represents logistic growth, where the population stabilizes at the carrying capacity
Survivorship curve
A graph showing the number of individuals surviving at each age for a given species
Fecundity
The potential reproductive capacity of an individual within a population
r-selected species
Species that produce many offspring with low survival rates
K-selected species
Species that produce fewer offspring with higher survival rates
Age structure diagram
A graphical illustration showing the distribution of various age groups in a population
Behavior
The change in activity of an organism in response to a stimulus
Innate behavior
Behaviors that are genetically hardwired and do not require learning
Learned behavior
Behaviors acquired through experience and environmental conditioning
Behavioral biology
The study of the biological and evolutionary bases for behavior
Ethology
The scientific study of animal behavior, particularly in natural environments
Reflex action
An involuntary and rapid response to a stimulus, such as pulling your hand away from a hot stove
Kinesis
The undirected movement in response to a stimulus, often increasing the chance of moving out of an unfavorable environment
Taxis
Directed movement towards or away from a stimulus, such as moving towards light (positive phototaxis)
Fixed action pattern
A sequence of movements elicited by a stimulus that continues even if the stimulus is removed
Migration
The long-range seasonal movement of animals, often driven by resource availability
Foraging
The act of searching for and exploiting food resources
Selfish behavior
Behavior that benefits the individual performing it, sometimes at the expense of others
Altruistic behavior
Behavior that benefits another individual, often at a cost to the one performing it
Cooperative behavior
When two or more individuals work together for mutual benefit
Signals
Behaviors or structures that convey information to other organisms, such as pheromones or visual displays
Courtship displays
Ritualized behaviors designed to attract and convince a mate
Aggressive displays
Behaviors intended to intimidate or deter others, often to avoid actual fighting
Distraction displays
Behaviors designed to attract a predator away from vulnerable offspring, often seen in birds
Kin selection
The evolutionary strategy that favors the reproductive success of an organism's relatives, even at a cost to the organism’s own survival
Habituation
A decrease in response to a repeated stimulus that has no positive or negative consequences
Imprinting
A type of learning that occurs at a specific life stage, often rapid and independent of the consequences of behavior
Conditioned behaviors
Behaviors that are learned responses to specific stimuli
Classical conditioning
A learning process where a neutral stimulus becomes associated with a meaningful stimulus, eliciting a conditioned response
Operant conditioning
A type of learning where behavior is controlled by consequences, such as rewards and punishments
Cognitive learning
The acquisition of knowledge and skills through processing and understanding information