Introduction to Ecology

• Ecology represents the scientific study of the interactions between organisms and their environment.
• Ernst Haeckel coined the term "ecology" in 1866.
• Ecology takes into account different hierarchical levels of organization, from individual organisms to the biosphere.
• An ecosystem constitutes a community of living organisms, along with biotic factors, interacting with their nonliving or abiotic environment.
• Ecosystems differ significantly in size and complexity.
• Forests, lakes, and grasslands serve as examples of various ecosystems.

Levels of Ecological Study

• Organismal ecology explores how an organism's structure, physiology, and behavior help it to meet environmental challenges.
• Population ecology studies the factors affecting the number of individuals of a species within a specific area.
• Community ecology examines the interactions between different species within a given area.
• Ecosystem ecology places emphasis on both energy flow and chemical cycling between organisms and the environment.
• Landscape ecology addresses the arrangement of ecosystems within a geographical region.
• Global ecology studies the influence of energy and materials on organisms across the biosphere.

Abiotic Factors

• Abiotic factors are the non-living components of the environment.
• Sunlight, temperature, water, nutrients, and wind represent key abiotic factors.
• Sunlight provides photosynthetic organisms with energy.
• Temperature influences metabolic rates and the distribution of organisms.
• Water availability is vital for all living organisms.
• Nutrients like nitrogen and phosphorus, are essential for both plant and animal growth.
• Wind impacts temperature, water availability, and distribution of nutrients.
• The specific impact of abiotic factors can vary depending on the ecosystem.

Biotic Factors

• Biotic factors are the living components of the environment.
• Plants, animals, fungi, bacteria, and other microorganisms are examples of biotic factors.
• Interactions between organisms include competition, predation, mutualism, and commensalism.
• Competition happens when multiple organisms need the same limited resources.
• Predation involves one organism or the predator, consuming another organism as prey.
• Mutualism defines a relationship that benefits both species.
• Commensalism benefits one species without harming or helping the other.
• These interactions can determine the structure and dynamics of ecological communities.

Energy Flow in Ecosystems

• Energy flow defines the passage of energy through the components of an ecosystem.
• Primary producers like plants convert sunlight into chemical energy through the process of photosynthesis.
• Consumers obtain energy by feeding on other organisms.
• Primary consumers or herbivores consume primary producers.
• Secondary consumers or carnivores eat primary consumers.
• Tertiary consumers consume secondary consumers.
• Detritivores (decomposers) consume dead organic matter.
• Energy transfer lacks efficiency between trophic levels.
• Approximately 10% of the energy stored in one trophic level converts into biomass in the subsequent trophic level.
• This limits the length of food chains within an ecosystem.

Nutrient Cycling in Ecosystems

• Nutrient cycling involves the movement of nutrients between the biotic and abiotic components of an ecosystem.
• Key nutrient cycles include the water cycle, carbon cycle, nitrogen cycle and phosphorus cycle.
• The water cycle consists of evaporation, transpiration, condensation, and precipitation.
• The carbon cycle includes photosynthesis, respiration, decomposition, and combustion.
• The nitrogen cycle includes nitrogen fixation, nitrification, assimilation, ammonification, and denitrification.
• The phosphorus cycle includes weathering of rocks, absorption by plants, and decomposition.
• Human activities can significantly alter nutrient cycles.
• Excessive fertilizer use, for instance, can contribute to nutrient pollution.

Population Ecology

• Population ecology focuses on the factors influencing size, density, and distribution of populations.
• Population size denotes the number of individuals within a population.
• Population density represents the number of individuals per unit area or volume.
• Population distribution is the spatial arrangement of individuals.
• Populations reveal different growth patterns.
• Exponential growth occurs when a population increases at a constant rate.
• Logistic growth happens when a population's growth slows down as it approaches its carrying capacity.
• Carrying capacity represents the maximum population size that an environment can sustain.
• Limited resource availability, competition, predation, and disease can be factors that limit population growth.

Community Ecology

• Community ecology explores the interactions between various species within a specific area.
• Community structure is subject to predation, competition, and disturbance.
• Interspecific competition is when different species compete for the same limited resource.
• Ecological niche defines the function and position a certain species has in its environment; including how it secures its needs for shelter and food, how it survives, and how it reproduces.
• Predation affects the distribution and abundance of prey populations.
• Disturbances, like fires and storms, can modify community structure.
• Ecological succession defines the process of community change over period.

Ecosystem Services

• Ecosystem services encompass the benefits humans derive from ecosystems.
• These services can be categorized into provisioning, regulating, supporting, and cultural services.
• Provisioning services cover the supply of food, water, timber, and fuel.
• Regulating services relate to climate regulation, flood control, and water purification.
• Supporting services cover nutrient cycling, soil formation, and pollination.
• Cultural services include recreational, aesthetic, and spiritual benefits.
• Human activities impact the capability of ecosystems to provide services.

Human Impacts on Ecosystems

• Human activities have significantly impacted ecosystems globally.
• Such impacts lead to habitat destruction, pollution, climate change, and invasive species.
• Habitat destruction accounts for the leading cause of biodiversity loss.
• Pollution has the potential to contaminate the air, water, and soil.
• Climate change alters temperature and precipitation patterns.
• Invasive species outcompete native species and disrupt ecosystem functions.
• Conservation efforts can aid in protecting ecosystems and the services they provide.