Ecology 101

Ecology: Study of Organisms and Their Environment

Ecology is a branch of biology that studies the relationships between living organisms, including humans, and their physical environment.
It considers organisms at individual, population, community, ecosystem, and biosphere levels, and overlaps with biogeography, evolutionary biology, genetics, ethology, and natural history.
Ecology has practical applications in conservation biology, wetland and natural resource management, urban planning, and human social interaction.
The word ecology was coined in 1866 by Ernst Haeckel, and modern ecological theory is based on evolutionary concepts of adaptation and natural selection.
Ecosystems are dynamic systems of organisms and their non-living components, with feedback mechanisms that regulate energy and matter fluxes and sustain life-supporting functions.
Ecology is organized into a nested hierarchy, ranging from genes to the biosphere, and exhibits non-linear behaviors.
Biodiversity includes species diversity, ecosystem diversity, and genetic diversity, and plays an important role in ecosystem services and conservation.
A habitat describes the environment over which a species occurs, and a niche is the set of biotic and abiotic conditions in which a species is able to persist.
Biomes categorize regions of the Earth's ecosystems, such as the tropical rainforest, temperate deciduous forest, and tundra.
The largest scale of ecological organization is the biosphere, which regulates energy, nutrients, and climate at the planetary scale.
Population ecology studies the dynamics of species populations and how they interact with the wider environment.
Malthus' population principle of growth was transformed into the logistic equation, which describes population change as a function of birth, death, immigration, and emigration rates.Overview of Ecological Concepts and Their Applications
Population ecology is concerned with the growth and dynamics of populations and is based on models that assume a balance between the rates of increase and crowding.
Metapopulation ecology is a statistical approach used in conservation research that simplifies landscapes into patches of varying quality, and metapopulations are linked by migratory behaviors of organisms.
Community ecology investigates the interactions between different species that inhabit the same geographic area and studies predator-prey dynamics, competition, and mutualistic interactions.
Ecosystem ecology studies the fluxes of materials between different pools and attempts to determine the underlying causes of these fluxes. It is concerned with the community connections between plants and decomposers.
Food webs are archetypal ecological networks that illustrate pathways of energy and material flows. They are composed of subgroups where members are linked by strong interactions, and weak interactions occur between these subgroups.
Trophic levels are groups of organisms that acquire a considerable majority of their energy from the lower adjacent level and can be organized into trophic pyramids.
Keystone species are species that are connected to a disproportionately large number of other species in the food-web and maintain the organization and structure of entire communities.
Complexity in ecology is of at least six distinct types: spatial, temporal, structural, process, behavioral, and geometric, and relates to the dynamic resilience of ecosystems that transition to multiple shifting steady-states directed by random fluctuations of history.
Long-term ecological studies provide important track records to better understand the complexity and resilience of ecosystems over longer temporal and broader spatial scales.
The International Long Term Ecological Network (LTER) manages long-term ecological studies, such as the Park Grass Experiment that was initiated in 1856, and the Hubbard Brook study that has been in operation since 1960.
Plant ecologists use pollen records that accumulate and stratify in wetlands to reconstruct the timing of plant migration and dispersal relative to historic and contemporary climates.
Animal migration involves the seasonal departure and return of individuals from a habitat and is a population-level phenomenon. Dispersal is usually distinguished from migration because it involves the one-way permanent movement of individuals from their birth population into another population.Ecology: A Comprehensive Overview
Holism is a critical part of the theoretical foundation in contemporary ecological studies, which addresses the biological organization of life that self-organizes into layers of emergent whole systems that function according to non-reducible properties.
Ecology and evolutionary biology are sister disciplines of the life sciences, with natural selection, life history, development, adaptation, populations, and inheritance being examples of concepts that thread equally into ecological and evolutionary theory.
Behavioural ecology is the study of an organism's behaviour in its environment and its ecological and evolutionary implications, where adaptation is the central unifying concept.
Cognitive ecology integrates theory and observations from evolutionary ecology and neurobiology, primarily cognitive science, in order to understand the effect that animal interaction with their habitat has on their cognitive systems and how those systems restrict behavior within an ecological and evolutionary framework.
Social ecology is notable in the social insects, slime moulds, social spiders, human society, and naked mole-rats where eusocialism has evolved, and social behaviours include reciprocally beneficial behaviours among kin and nest mates and evolve from kin and group selection.
Biogeography is the comparative study of the geographic distribution of organisms and the corresponding evolution of their traits in space and time, with biogeographical patterns resulting from ecological processes that influence range distributions, such as migration and dispersal, and from historical processes that split populations or species into different areas.
r/K selection theory is one of the first predictive models in ecology used to explain life-history evolution, where the premise behind the r/K selection model is that natural selection pressures change according to population density.
Molecular ecology uses various analytical techniques to study genes in an evolutionary and ecological context, where newer technologies opened a wave of genetic analysis into organisms once difficult to study from an ecological or evolutionary standpoint, such as bacteria, fungi, and nematodes.
Human ecology is an interdisciplinary investigation into the ecology of our species, where the ecological complexities human beings are facing through the technological transformation of the planetary biome has brought on the Anthropocene.
Ecosystems tie into human societies through the critical and all-encompassing life-supporting functions they sustain, and in recognition of these functions and the incapability of traditional economic valuation methods to see the value in ecosystems, there has been a surge of interest in social-natural capital.
Ecology is an employed science of restoration, repairing disturbed sites through human intervention, in natural resource management, and in environmental impact assessments.
The relationship between ecology and genetic inheritance predates modern techniques for molecular analysis, with molecular ecological research becoming more feasible with the development of rapid and accessible genetic technologies, such as the polymerase chain reaction (PCR).
Indirect mutualisms occur where the organisms live apart, and if the associate benefits while the host suffers, the relationship is called parasitism.Ecology: The Study of Ecosystems
Resource managers employ ecologists to develop and implement ecosystem-based methods for land-use planning, operation, and restoration.
The environment of ecosystems includes physical parameters and biotic attributes, which are dynamically interlinked and contain resources for organisms.
The distinction between external and internal environments is an abstraction, as there is an interpenetration of cause and effect between the environment and life.
Ecosystems are regularly confronted with natural environmental variations and disturbances, creating places of renewal where new directions emerge from natural experimentation.
The Earth's atmosphere and biogeochemical cycles have been in a dynamic equilibrium with planetary ecosystems throughout history.
Heat affects growth rates, activity, behavior, and primary production in organisms, and temperature is largely dependent on the incidence of solar radiation.
Water influences the intensity and spectral composition of light, and aquatic plants exhibit a wide variety of morphological and physiological adaptations.
Gravitational forces significantly affect the shape and energy of the land, as well as the direction of plant and fungal growth and animal migrations.
Climatic and osmotic pressure places physiological constraints on organisms, especially those that fly and respire at high altitudes or dive to deep ocean depths.
Wind power and the turbulent forces it creates can influence heat, nutrient, and biochemical profiles of ecosystems.
Fire is a significant ecological parameter that creates a heterogeneous ecosystem age and canopy structure, opening new ecological niches for seedling establishment.
Soil is the chief organizing center of most ecosystem functions, with a large biomass of the Earth's biodiversity organizing into trophic levels.
Nutrient budgets are regulated, flow, and recycled through the environment, with six major elements forming the constitution of all biological macromolecules and feeding into the Earth's geochemical processes.