ENVIRONMENTAL ECOLOGY

1. Ecology

The term Ecology is derived from the Greek language and was coined by Ernst Haeckel. Ecology is a branch of biology which means the study of living organisms and the interaction between them and their surrounding environment. Ecology helps to understand how organisms live with each other in unique physical environments.

Ecology is a combination of two words- ‘oikos’ meaning home or place to live in and ‘logos’ meaning study. Ecology means the study of the home of nature.

Definition- Scientific study of interactions of organisms with their physical environment and with each other.

It deals with how organisms are moulded by their environment, and how they make use of environmental resources including energy flow and mineral cycling.    

A healthy interaction between biotic and abiotic components brings balance to the environment.

History

• The roots of ecology lie in Natural History, which is as old as human civilization. In primitive societies, every individual was required to have an intimate knowledge of the environment for their survival, like the forces of nature and plants and animals around them.
• Ancient Indian texts have references to ecological principles. The classical texts of the Vedic period like the Vedas, the Samhitas, the Brahmanas, the Aranyakas and the Upanishads contain references to ecology.
• The Indian medicine treatise, the Charaka-Samhita and the surgical text Sushruta-Samhita, written by Agnivesa a sage, show that people during this period had a good understanding of plant and animal ecology.
• These texts contain classification of animals based on habit and habitat, land in terms of nature of soil, climate and vegetation and description of typical plants, to various localities. Charaka-Samhita contains information that air, land, water and seasons were indispensable for life and that polluted air and water were injurious to health.

2. Environment 

• Everything that surrounds or affects an organism during its lifetime is called environment. Environment is composed of both living and non-living components; influences and events surrounding an organism.
• All organisms, from unicellular bacteria (viruses) to multicellular humans are obligatorily dependent on other organisms and the environment for food, energy, water, oxygen, shelter and other needs.
• The relationship and interaction between organisms and the environment is very complex. It comprises of living(biotic) and non-living(abiotic) components. The environment is not static, it keeps on changing.

Components of Environment 

Environment of a fish in the pond

Fish is an aquatic organism, so there will be many biotic and abiotic factors responsible for its survival. Let's discuss this in detail.

External environment of fish

• Abiotic factors like light, temperature, water with nutrients, oxygen, other gases and organic matter are dissolved.
• The biotic environment consists of microscopic organisms called plankton which it assumes as well as aquatic plants, animals and decomposers.

The internal environment of fish

• The internal environment is relatively stable as compared to the external environment.
• It is enclosed by the outer surface.
• Injury, illness or excessive stress upsets the internal environment.
• For instance, if a marine fish is transferred to a freshwater environment, it will not be able to survive.

Levels of Organization

ECOLOGY is considered the study of organisms with their environment. Many levels are organized and framed for ease of study.

Individual—>Population—>Community—>Ecosystem—>Biome—>Biosphere

Individual

A single, separate, distinct person/animal/plant/bacteria distinguished from others of the same kind is called an individual. An individual living being that can function or act independently. It is a body made of organs, organelles or other parts that work together to carry out the various processes of life.

Population

• Population is a group of organisms usually of the same species, occupying a defined area during a specific time.
•  Population growth rate is the percentage variation between the number of individuals in a population at two different times. Therefore the population growth rate can be positive or negative.
• The main factors that cause population increase are birth and immigration. The main factors that make the population decrease are death and emigration.
• The main limiting factors for the growth of a population are abiotic and biotic components.
• Population density is the relation between the number of individuals in a population and the area they occupy.
• Population growth is the increase in the number of people in a population or dispersed group.

Population growth rate is the rate at which the number of individuals in a population increases in a given period, expressed as a fraction of the initial population. Population growth rate refers to the change in population over a unit period, often expressed as a percentage of the number of individuals in the population at the beginning of that period.

          Population growth rate = P(t2)-P(t1)/P(t1) (t2-t1)

Community

• A community is a group or association of populations of two or more different species occupying the same geographical area at the same time. It is also known as biocoenosis, biotic community, or ecological community.
• Community ecology or synecology is the study of the interactions between species in communities and interactions between coexisting populations.
• If we look around ourselves, we will notice that the population of plants and animals seldom occur by themselves. The reason for this is quite obvious. To survive, individuals of any one species depend on different species with which they actively interact in several ways.
• For example, animals require plants for food and trees for shelter. Plants require animals for pollination, seed dispersal and soil microbes to facilitate nutrient supply.
• Communities in most instances are named after the dominant plant form i.e., plant species.
• For example, a grassland community is dominated by grasses, though it may contain herbs, shrubs and trees, along with associated animals of different species.
• A community is not fixed or rigid; communities may be large or small.

Types of Communities

Based on size and degree of relative independence, communities may be divided into two types.

Minor Community- These are dependent on neighbouring communities and are often called societies. They are secondary aggregations within a major community and are not therefore completely independent units as far as energy and nutrient dynamics are concerned  Example- A mat of lichen on a cow dung pad.

Structure of a community

• In a community, the number of species and the size of their population vary greatly. A community may have one or several species.
• The environmental factors determine the characteristics of the community as well as the pattern of organization of the members in the community.
• The characteristic pattern of the community is termed as structure which is reflected in the roles played by various population, their range, the type of area they inhabit, the diversity of species in the community and the spectrum of interactions between them.

3. Ecosystem

• An ecosystem is defined as a structural and functional unit of the biosphere consisting of a community of living beings and the physical environment, both interacting and exchanging materials between them.
• It includes plants, trees, animals, fish, birds, microorganisms, water, soil and people.
• Ecosystems vary greatly in size and elements but each is a functioning unit of nature. Everything that lives in an ecosystem is dependent on the other species and elements that are also part of that ecological community. If one part of an ecosystem is damaged or disappears,  it has an impact On everything else.
•  When an ecosystem is healthy( sustainable),  it means that all the elements live in balance and are capable of reproducing themselves.  An ecosystem can be as small as a single tree or as large as an entire forest.

Components of ecosystem

 The components of the ecosystem and environment are the same.

• Abiotic factors are the most important determinants of where and how well an Organism exists in its environment.  Although these factors interact with each other, one single factor can limit the range of an Organism.
• Energy- Energy from the sun is essential for the maintenance of life. In the case of plants, the sun directly supplies the necessary energy.  Since animals cannot use solar energy directly they obtain it indirectly by eating plants animals or both. Energy determines the distribution of organisms in their environment.
• Rainfall- Water is essential for all living beings.  The majority of biochemical reactions take place in an aqueous medium.  Water helps to regulate body temperature.  Further, water bodies form the habitat for many aquatic plants and animals.
• Temperature- Temperature is a critical factor of the environment which greatly influences the survival of organisms.  Organisms can tolerate only a certain range of temperature and humidity.
• Atmosphere- The Earth’s atmosphere  Is responsible for creating conditions suitable for the existence of a healthy biosphere on this planet.
• Substratum- The land is covered by soil and a wide variety of microbes, protozoa, fungi, and small animals(invertebrates) thrive in it.  Roots of plants pierce through the soil to absorb water and nutrients.  Organisms can be terrestrial or aquatic.  Terrestrial animals live on land. Aquatic plants,  animals and microbes live in hot water under the sea.
• Materials- Organic compounds like proteins, carbohydrates, and lipids, are formed from inorganic compounds on decomposition. Inorganic compounds like carbon dioxide, water, sulphur, nitrates, phosphates and ions of various metals are essential for organisms to survive.
• Latitude and altitude- Latitude has a strong influence on an area’s temperature, resulting in changes in climates like polar, tropical, and temperate. These climates determine different natural biomes.

Biotic components

Biotic components include living organisms comprising plants,  animals and microbes.  They are classified according to their functional attributes into producers and consumers.

1. They are also known as autotrophs.
2. Producers are green plants and certain bacteria and algae.
3. They synthesize carbohydrates from simple inorganic raw materials like carbon dioxide and water in the presence of sunlight by the process of photosynthesis.
4.  In terrestrial ecosystems, producers are herbaceous and woody plants, while in aquatic ecosystems producers are various species of microscopic algae.

Macro consumers

1. They feed on plants and animals or both and are categorized based on their food source.
2. Herbivores are primary consumers who feed on plants or their products. Example- cow, goat, grasshopper etc.,
3. Secondary consumers feed on primary consumers. Example-wolves are frogs etc.,
4. Carnivores which feed on secondary consumers are called tertiary consumers. Example-lions, snake etc.,
5. Omnivores are organisms which consume both plants and animals. Example- man, bear, monkey etc.,

 Micro consumers

1. They are also known as decomposers or saprotrophs or 
2. They include bacteria and fungi which obtain energy and nutrients by decomposing dead organic substances of plant and animal origin.
3. The products of decomposition such as inorganic nutrients which are released in the ecosystem are reused by producers and recycled.
4. Earthworms and some soil organisms like nematodes and arthropods are detritus feeders and help in the decomposition of organic matter and are called detrivores.

 Classification of ecosystem

•  A natural ecosystem is classified into terrestrial and aquatic ecosystems.
•  Terrestrial ecosystems include the forest,  grasslands,  and deserts.
•  Aquatic ecosystems include freshwater, saline water,  and marine water.

 Ecosystems are capable of maintaining their state of equilibrium. They can regulate their own species' structure and functional process. This capacity of the ecosystem of self-regulation is known as homeostasis.

 Goods and services provided by the ecosystem

• Provision of food, fuel and fibre
• Provision of shelter and building material
• Purification of air and water
• Detoxification and decomposition of waste
• Stabilization and moderation of  the earth’s climate
• Moderation of floods, droughts, temperature extremes and the forces of wind
• Generation and renewal of soil fertility, including nutrient cycling
• Pollination of plants, including many crops, control of  pests and  diseases
• Maintenance of genetic resources as key inputs to crop varieties and livestock breeds, medicines and other products
• Cultural and aesthetic benefits

4. Ecotone

A transitional area of vegetation between two different plant communities, such as forest and grassland.

An ecotone is a zone of junction between two or more diverse ecosystems. For example, my growing forest represents an Ecotone between marine and terrestrial ecosystems. Other examples are grassland, estuary and riverbanks.

 Characteristics of ecotone

•  It may be very narrow are quite wide.
• It has the conditions intermediate to the adjacent ecosystem. Hence it is a zone of tension.
• It is linear as it shows a progressive increase in species composition of one in the upcoming community and a simultaneous decrease in species of the other outgoing adjoining community.
• A well-developed ecotone contains some organisms which are entirely different from that of the adjoining communities.
• Sometimes number of species and the population density of some of the species is much greater in the zone of either community. This is called the edge effect.

The organisms which occur primarily or most abundantly in this zone are known as edge species.

 In terrestrial ecosystems Edge effect is especially applicable to birds. For example, the density of birds is greater in the mixed habitat of the ecotone between the forest and the desert.

 Niche

•  A  Niche is the unique functional role a place of a  species in an ecosystem. It is a description of all the biological, physical and chemical factors that a species needs to survive, stay healthy and reproduce.
•  A niche is unique for a  species, which means no two species have exact identical niches. Niche plays an important role in the conservation of organisms.
•  If we have to conserve species in its native habitat we should know the niche requirements of the species and should ensure that all requirements of its niche are fulfilled.

 Types of niche

1. Habitat niche- where it survives
2. Food niche- what it  eats or  decomposes and what   species it competes with
3. Reproductive niche- how and  when it reproduces
4. Physical and chemical niche- temperature, land shape, land slope, humidity and other requirements.

 Biome

• A distinct biogeographical unit consisting of a biological community that has formed in response to a shared regional climate.
• The terrestrial part of the biosphere is divisible into enormous regions called biomes, which are characterized by, climate, vegetation, animal life and general soil type.
•  The climate determines the boundaries of a Biome and the abundance of plants and animals found in each of them. No two biomes are alike. The most important climatic factors are temperature and precipitation.

5. Aquatic Zones

Aquatic systems are not called biomes, however, they are divided into distinct life zones, with regions of relatively distinct plant and animal life. The major differences between various aquatic zones are due to salinity, levels of dissolved nutrients, water temperature,  and depth of sunlight penetration.

•  The biosphere is a narrow layer around the surface of the earth. Life in the biosphere is abandoned between 200 meters below the surface of the ocean and about 6000 meters above sea level.
•  Biosphere is absent in extremes of the north and South poles, the highest mountains and the deepest oceans, since existing hostile conditions there, do not support life.
•  Occasionally sports of fungi and bacteria occur at great heights beyond 8000 meters, but they are not metabolically active and hence represent only dormant life.
•  The energy required for life within the biosphere comes from the sun. The nutrients necessary for living organisms come from air, water, and soil.  The same chemicals are  Recycled over and over for life to continue.
•  Living organisms or not uniformly distributed throughout the biosphere. Only a few organisms live in the polar regions, while the tropical rainforest how an exceedingly rich diversity of plants and animals( 50% of global biodiversity).