‘Ecology’ comprises the study of living organisms, their interdependence with other living organisms (mammals, insects, reptiles, micro-organisms) around them, along with their interactivity with their abiotic environment (non-living elements such as water, soil, air, land and sea, etc.).

Ecology can be categorized into two types, based on classification:

• Based on the nature of their interaction

1. Autecology deals with the study of an organism (or its species), their adaptations and interplay with their environment
2. Synecology deals with the study of different species living in habitats and their exchange with their surroundings. 

• Based on their location/type of ecosystem

1. Aquatic ecology involves the study of aquatic ecosystems. E.g. rivers, oceans, etc.
2. Terrestrial ecology involves the study of the terrestrial ecosystems. E.g. grasslands, forests, deserts, etc.

The ecological jargon involves biotic and abiotic elements, with varying complexities depending on the size of the scale in perspective. The following sequence is observed in Ecology for careful categorization and realization of organisms:

Organism → Species (population) → Biotic community → Ecosystem → Biome → Biosphere

• An organism is the simplest unit of an ecosystem. It comprises all living beings, unicellular or multicellular, including plants, animals, vertebrates, invertebrates, etc.
• Species/Population are organisms of the same species that live in the same habitat, often sharing geographical surroundings. A species refers to a group of organisms sharing a common gene pool and can be bred with each other for producing an offspring.
• Biotic community includes producers, consumers and decomposers, and all such living organisms that can be grouped as a part of multiple interlinked life-cycles. 
• An ecosystem is a fundamental unit of the ecological cycle. It covers the biotic community and its interrelations with its abiotic physical environment. Biotic and abiotic components together formulate a complete ecosystem.
• Biome consists of various ecosystems that are observed within a vast geographical area.
• The biosphere can be said to be the total sum of all ecosystems. It is also referred to as the zone of life on Earth. 

While an environment refers to the natural surroundings of organisms, it is difficult to explain it further without establishing the basis of classification. Habitat is the natural environment of an organism, where it tends to live, grow, and reproduce. It is a defined ecological area that is compatible with that specific organism. Habitats include abiotic components like water, temperature, light and soil, along with the biotic components, such as other species and organisms, predators, competitors, etc. 

A Niche involves the interaction of a species with its environment. Species are dependent on the quality of those abiotic and biotic factors for survival. When belonging to the same niche, organisms share a similar level of interaction to a range of factors that provide an optimum environment for survival.

Abiotic factors consist of climatic conditions such as temperature, soil, water, air, light; along with the inorganic and organic chemical components such as nitrogen, phosphorus, sulfur, carbohydrate, proteins, lipids, etc. that are necessary to sustain the biotic community. Following are some of the fundamental abiotic factors:

• Temperature is the most important environmental and ecological abiotic factor. Ranging from subzero temperatures in polar areas to scorching heat of above 50℃ in tropical desserts. Temperature impacts the kinetics of enzymes and alters the metabolic and physiological functions of organisms that are essential for survival.
• Water has been the basis of life since aeons. Organisms cannot sustain without water. Various factors like pH, chemical composition govern the quality of the water, which is important for the organisms inhabiting that area. They affect the survival of aquatic organisms, plants, algae, plankton, etc. as well as non-aquatic, terrestrial consumers of water.
• Sunlight has been the source of energy that flows in an ecosystem. Producers such as plants, trees and shrubs convert sunlight’s energy to chemical energy through the process of photosynthesis. The same energy, in the form of ATP, is transferred through the biological cycles, thus making it necessary for the survival of all beings. 
• Soils from different locations have different chemical compositions that affect the quality of nutrients that they provide for producers, as well as insects, micro-organisms, etc. They differ due to varying climatic conditions, weathering process and soil erosion.

The responses of biotic organisms to the abiotic factors that they are exposed to help us understand their optimum conditions, and thus ensure their survival. Following are the generally observed responses:

• Homeotherms maintain constant internal temperature, by responding to the temperature around them through a process called thermoregulation which helps them to adapt to the changes in temperatures. 
• Poikilotherms and ectotherms need to conform as they cannot regulate their internal temperature. They adapt to the change in temperature by absorbing heat or adjusting to the environment.
• Migratory organisms relocate temporarily to areas with hospitable environments to avoid stressful seasons.
• Cold-blooded animals perform hibernation or aestivation through periods of inactivity, to survive extreme cold or hot environmental conditions respectively.
• Most organisms undergo gradual evolution towards genetic adaptation. They include any morphological, physiological and behavioural adaptations carried out to increase the rate of survival of offspring.

Along with interactions with abiotic factors, organisms interact with one another for their survival. This synergy is what makes the study of ecology essential, as we can obtain better insights about an organism by studying the biological interactions that it undergoes during its lifespan. Here are some of the important biological interactions:

• Commensalism refers to the coexisting interaction of a species that benefits without affecting or harming other organisms. E.g. barnacles and bromeliads.
• Amensalism is an interaction where one species is under direct harm by the other, and the attacking organism remains unaffected. E.g. humans affected by harmful bacteria.
• Mutualism is when two organisms interact towards a mutual benefit of both the species.E.g. bees pollinating flowers.
• Competition is where two species need to compete for the same resources, and survival of one species can be declined by the presence of competitor species. E.g. hyenas and lions.
• Predation involves the relationship between prey and predator, where the predators need to hunt and consume their prey for survival. E.g.. frogs and insects.
• Parasitism refers to the relationship shared between a host and a parasite, where the parasite derives its needs from the host, while potentially harming it. E.g. tapeworms.