2.1 Improved

Biosphere

The global sum of all ecosystems, including life and interactions with land, water, and air.

Ecosystem

A community and the physical environment with which it interacts. It's an open system where both energy and matter can enter and exit.

Community

A group of populations of different species living and interacting with each other in the same area.

Population

A group of organisms of the same species living in the same area at the same time and capable of interbreeding.

Species

A group of organisms that share common characteristics and that interbreed to produce fertile offspring.

Individual

A single organism capable of independent survival (e.g., a single elephant).

Habitat

The natural environment where a species lives, providing necessary survival conditions.

Biotic Factor

A living, biological factor that may influence an organism or ecosystem (e.g., predation, parasitism, disease).

Abiotic Factor

A non-living, physical factor that may influence an organism or ecosystem (e.g., temperature, sunlight, pH).

Niche

The ecological role of a species in an ecosystem and the range of conditions necessary for its survival.

Fundamental Niche

The full range of environmental spaces, habitats, and resources a species could theoretically use if not limited by competitors or other factors.

Realized Niche

The actual range of environmental spaces, habitats, and resources a species uses due to biotic interactions like competition and predation.

Competition

A common demand by organisms upon a limited resource (e.g., food, water). May be intraspecific or interspecific.

Predation

Interaction where one organism hunts and consumes another (e.g., wolves and deer).

Herbivory

The consumption of plants by animals, influencing plant populations and ecosystem balance.

Parasitism

A relationship where one species (parasite) lives on or in another (host), gaining nutrients. E.g., ticks, tapeworms.

Mutualism

A relationship in which all species involved benefit. E.g., bees and flowers.

Disease

A condition disrupting normal functioning due to pathogens, genetics, or environment.

Classification

The organization of organisms into different taxa (hierarchical groups) based on shared characteristics.

Taxonomist

A scientist who classifies organisms using traits and tools like dichotomous keys.

Genus Species

The scientific naming system for a species (e.g., Homo sapiens). The genus is capitalized, the species is lowercase, and both should be either italicized or underlined.

Dichotomous Key

A tool for identifying organisms by answering a series of trait-based questions.

Clade

Illustrates evolutionary relationships in which all the members of a taxonomic group have evolved from a common ancestor.

Exponential Growth

A rapid increase under ideal conditions, forming a J-shaped curve; typically unsustainable.

Logistic Growth (S-Shaped)

A growth model that slows as it nears carrying capacity

Carrying Capacity

The maximum population size of a species or "load" that can be sustainably supported by a given environment. This 'maximum' is dynamic and influenced by changes in abiotic and biotic factors.

Density-Dependent Factors

Limiting factors whose impact increases as population density rises. Examples include competition for resources, predation, and disease, which intensify in crowded populations.

Density-Independent Factors

Limiting factors that affect populations regardless of their density. Examples include natural disasters (e.g., hurricanes, droughts) and extreme weather events.

Negative Feedback Mechanism

A mechanism that reverses a change, bringing a system back towards equilibrium. In population dynamics, density-dependent factors create this effect to regulate population size around the carrying capacity.

Random Sampling

A technique where every individual or location has an equal chance of being selected to minimize bias, often used in uniform habitats.

Systematic Sampling

Data collection at regular intervals to ensure even coverage of the study area, often used along a transect to study an environmental gradient.

Transect Sampling

A form of systematic sampling where data is collected along a line at regular intervals, often used to investigate changes along an environmental gradient.

Quadrat

A square frame used to isolate a standard area for studying abundance and distribution of organisms.

Capture-Mark-Release-Recapture

A method to estimate animal population sizes by marking, releasing, and recapturing individuals.

Lincoln Index

A formula to estimate population size using mark-recapture. Population Estimate = (M × N) / R, where M = number initially caught and marked, N = total caught in the second sample, and R = number of marked individuals recaptured.

Sustainability

The ability of a system to continue indefinitely. In ecosystems, this is seen as a steady-state equilibrium where inputs are balanced by outputs, allowing the system to persist for long periods.

Keystone Species

A species that has a disproportionately large impact on its environment relative to its abundance, and is necessary for maintaining its ecosystem's structure and function. Examples include wolves in Yellowstone and sea otters in kelp forests.

Tipping Point

The critical threshold in a system where a small change can lead to an abrupt and often irreversible shift to a new state.

Food Web

A network of interconnected food chains showing energy/nutrient flow in an ecosystem.

Trophic Cascade

When changes in one species (often a top predator) ripple through the food chain. (e.g., The reintroduction of wolves, a keystone species, to Yellowstone caused this phenomenon, restoring the ecosystem).

Biosphere Integrity

The health and functioning of Earth's ecosystems, including biodiversity and resilience. One of the nine planetary boundaries.

Planetary Boundaries Model

A framework identifying nine key Earth system processes with a "safe operating space" for humanity. It proposes that crossing these boundaries increases the risk of large-scale, abrupt environmental change.

Extinction Rate

The number of species becoming extinct over a given period of time. It is used as a key metric for assessing the genetic diversity component of the Planetary Boundary for Biosphere Integrity.

Invasive Species

Non-native species that disrupt ecosystems, outcompete natives, and reduce biodiversity.

Afforestation vs. Reforestation

Planting trees on non-forested land vs. replanting in previously forested areas.