Environment refers to all the conditions that influence and affect the development and sustainability of life of all organisms present on the earth. It is an immediate surrounding of living organisms in which it lives and operates.
Ecology is the study of inter-relationship of organisms with physical as well as biotic environments.
Organisms and environment are interrelated and interdependent. Any change in the environment affects the living organisms and vice-versa.
An ecosystem is the structural and functional unit of ecology. It is a community of living organisms along with the abiotic components interacting together through energy flows and nutrient cycles.
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It is important to have an understanding of the surroundings as the survival of mankind is dependent on it. These terms are often used interchangeably but they differ in their scope.
The continued increase in human population and intervention, e.g. deforestation, pollution, excess use of natural resources and pesticides has resulted in the destruction of the natural environment and has made people aware about the ecology and environment.
Introduction to Ecology
Ecology is the study of interaction among living organisms (plants, animals, microbes) as well as interaction with its abiotic environment (temperature, water, air, soil, light, etc.).
According to Odum, who is known as the Father of modern ecology, “Ecology is the study of structure and function of ecosystems”.
Reiter was the first person to use the term ecology.
Ernst Haeckel was given credit to coin and defined the term “Ecology”.
Ramdeo Misra is known as the Father of ecology in India.
Ecology is divided into two main branches:
- Autecology- deals with an organism or species, its adaptations and interaction with its environment
- Synecology- deals with the study of different species living in a community and its relation with the surrounding. It is further divided into aquatic and terrestrial ecology.
Aquatic ecology deals with aquatic ecosystems, e.g. freshwater, marine, etc.
Terrestrial ecology deals with the terrestrial ecosystems, e.g. forest, grassland, desert, etc.
There are some modern branches of ecology:
- Applied Ecology deals with the study of conservations and getting economic benefits of organisms, e.g. wild-life management, agronomy, etc.
- Genecology is the study of genetic composition and variation present in communities compared to the environment and population distribution and origin of new species, ecads, ecotypes, etc.
- System Ecology is the most modern branch of ecology, which takes advantage of applied mathematics, computer science and advanced statistical techniques to understand the structure and function of an ecosystem.
Some Important concepts of Ecology
Ecological hierarchy follows the below order with an increase in size and complexity
Organism → Species (population) → Biotic community → Ecosystem → Biome → Biosphere
Organism: is the smallest and basic unit of ecology. It includes all the living organisms, unicellular or multicellular having a fixed lifespan.
Species or Population: members of the same species living in a specific geographical area. A species is a group of organisms that have a common gene pool and can interbreed to produce fertile offspring.
- Endemic species are found only in a particular area, e.g. kangaroos found in Australia
- Key-stone species is mostly a predator species, which is not present in large number but has a major influence on the characteristics of a community, e.g. lion in the forest.
- Critical Link species, which help other species in the vital activities, e.g. pollinators for plants, parasitic and symbiotic relationships.
Community: the interacting group of various different species living in an area, it includes plants, animals and microbes.
Ecosystem: it is the functional unit of the ecology. It includes the biotic community and the interacting physical environment associated with it. Biotic components and abiotic components constitute an ecosystem.
Biotic components include producers, consumers and decomposers.
Abiotic components include climatic conditions such as temperature, soil, water, air, light; inorganic and organic substances such as nitrogen, phosphorus, sulfur, carbohydrate, protein, lipid, etc.
Biome: consists of communities present in a large geographical area.
Biosphere: it is the total sum of all ecosystems. It is also known as the zone of life on Earth. It includes all the living organisms, their relationships and interaction with the elements of atmosphere, hydrosphere and lithosphere.
Habitat: It is a natural environment of an organism where it grows, lives and reproduces. It is an ecological area best-suited for an organism. Habitats vary in the physical and chemical composition. It includes abiotic components like water, temperature, light and soil and biotic components too, e.g. parasites, competitors, pathogens and predators interacting with them constantly. Life exists not only in the most favourable habitat but also in the most extreme and harsh environment. Ecology at an organism level tries to understand how different species adapt to their environments for their survival and reproduction.
Niche: includes all the interaction of a species with the biotic and abiotic factors of its environment. Each species has a defined range of various abiotic factors that it can tolerate, a number of resources it utilises for survival and performs a specific functional role in an ecosystem, all these together form a niche, which is unique to a species.
Also Check: Difference between Habitat and Niche
Temperature: It is the most important environmental ecological factor. It ranges from a subzero level in polar areas to >50℃ in tropical desserts. In thermal springs and deep-sea hydrothermal vents, the temperature even exceeds 100℃. Temperature affects the kinetics of enzymes and alters metabolic and physiological functions of organisms.
- Eurythermal- organisms, that can tolerate a wide range of temperatures
- Stenothermal- organisms, that can tolerate a narrow range of temperatures
Water: life originated in water and organisms cannot sustain without water. Organisms need special adaptations to live in water. Various factors like pH, chemical composition govern the quality of the water, which is an important factor for organism inhabiting the area. The salinity of water varies in different water resources, e.g. it is 5 (measured as salt concentration in part per thousand) in rivers, lakes, 30-35 in the ocean and >100 in hypersaline lagoons
- Euryhaline- organisms, that can tolerate a wide range of salinities
- Stenohaline- organisms, that can tolerate a narrow range of salinities
Light: Sunlight is the source of energy that flows in an ecosystem. Producers convert light energy to chemical energy in the process of photosynthesis. The spectral quality of light is also an important factor, e.g. UV component is harmful to many organisms. Many plants require critical daylight for flowering, the process is known as photoperiodism.
Soil: different places have different quality of the soil. They differ due to climatic conditions, weathering process and soil development.
Responses to Abiotic Factors
It is important to understand how organisms cope with stressful and adverse environmental conditions. There are different mechanisms by which an organism accomplishes homeostasis.
- Regulate: Mammals, birds, a few lower vertebrates and invertebrates are capable of thermoregulation and osmoregulation to keep the constant internal temperature and osmotic concentration, thereby maintaining homeostasis. They are called homeotherms or endotherms.
- Conform: Most of the plants and animals, cannot keep their internal temperature and osmotic concentration constant and it changes with the external environment. They are known as poikilotherms or ectotherms. They adapt to the surroundings or migrate in extreme conditions.
- Migrate: Organisms move away to the more hospitable area temporarily to avoid stressful period and come back once it is over. E.g. Siberian birds migrate to Keoladeo National Park in Bharatpur in winters.
- Suspend: Cold-blooded animals go into hibernation or aestivation to survive extreme cold or hot environmental conditions respectively.
Zooplankton species enter diapause under unfavourable conditions.
Formation of thick-walled spores in lower plants, fungi and bacteria help them in surviving unfavourable conditions. Higher plants survive under unfavourable conditions by going into the dormancy state.
- Adaptation: Adaptation is any morphological, physiological and behavioural changes that help an organism to survive and reproduce in its habitat.
Some examples of adaptation:
- Kangaroo rat– meets its water requirement by internal fat oxidation where water is a by-product and by concentrating its urine
- Desert plant- have a thick cuticle, sunken stomata, leaves reduced to spines, green stem performing photosynthesis, CAM (Crassulacean Acid Metabolism) pathway for photosynthesis in which stomata remains closed during the day to reduce water loss by transpiration
- Allen’s Rule- mammals in the colder region have shorter ears and limbs to reduce heat loss
- Seals- have a thick layer of fat under their skin known as blubber
- Himalayan tribes- higher RBC count and total haemoglobin to compensate for low oxygen availability at higher altitudes
Biological Interactions in an Ecosystem
In an ecosystem, all the organisms interact with each other for various needs or benefits such as food, support, nutrients, etc. Some interactions benefit all the organisms interacting and in some only one fulfils its need.
Below are a few important interactions present in the system:
- Commensalism: one species is benefited and other is neither benefited nor harmed, e.g. cattle egrets, tree frog
- Amensalism: one species is harmed and other remains unaffected, disease-causing parasites in human
- Mutualism: when two organisms interact together for the benefit of both the species, e.g. bees and flower, the association of Azolla (water fern) and Anabaena (nitrogen-fixing cyanobacterium)
- Competition: two species competing for the same resources and fitness of one species is affected by the presence of another species
- Predation: relationship of prey and predator
- Parasitism: the relationship between the host and a parasite, where the parasite gets benefited by the host. The host may remain unaffected or harmed