ECOSYSTEMS: AN INTRODUCTION

Ecosystem is a broad term which includes all organisms and the environment they live, i.e. it includes all living and non living things, and their interactions. In other words it is a community of organisms along with their physical environment. The study of ecosystems is called Ecology. It was Sir A G Tansley, who was an English Botanist, who introduced the concept of 'Ecosystem". The living and non-living components of the ecosystems are interlinked by means of energy transfer and biogeochemical cycles. Ecosystem can be defined as 'the living community of plants, animals and microbes in an area and their surrounding environment such as soil, air and water.' The basic living components of the ecosystem are producers, consumers and decomposers.

Ecosystems are broadly divided into terrestrial or land based ecosystems, and aquatic ecosystems in water.

1. AQUATIC ECOSYSTEMS

Aquatic ecosystems are water based ecosystems in which water acts as the surrounding environment for the living organisms. Aquatic ecosystems are further classified in to the following categories. - marine ecosystem, estuarine ecosystem and freshwater ecosystem, based on the salinity of water.

Marine ecosystem: When the salinity of the water is equal or more than 35ppt (parts per thousand), the ecosystem is considered to be marine. 

Freshwater ecosystem: When the salinity is 0.5 ppt or less, it is considered as freshwater ecosystem.

Estuarine ecosystem: When the salinity keeps varying between 0.5 to 30 ppt it is considered to be estuarine.

2. TERRESTRIAL ECOSYSTEMS

All the ecosystems which are seen on the land are called terrestrial ecosystems. They can be further divided based on the the types of plants and animals inhabiting. Some features of terrestrial organisms are the following; they are exposed directly to air, hence developed respiratory system for gaseous exchange; the plants have extensive root system for finding water in the soil and absorbing it; animals have developed mechanisms to combat with heat or cold.

Forest ecosystem: Terrestrial ecosystem in which trees are the dominant vegetation. They can be further subdivided into tropical forests, temperate forests and boreal forests.

Grassland ecosystem: When the vegetation is dominated by grasses, the ecosystem is called grassland ecosystem. They can be further divided into tropical grasslands and temperate grasslands. Tropical grasslands are called savannah and temperate grasslands are called prairies, steppes, pampas, veldts etc. in different places.

Desert ecosystem: Desert is a region which receives very less rainfall, which is usually less than 25 cm per year. There are two types of deserts: hot deserts and cold deserts.

ECOLOGICAL PYRAMIDS

Ecological pyramids are graphical representations of the trophic structure in an ecosystem. The major trophic levels in an ecosystem are the following;

1. Producers

2. Primary consumers

3. Secondary consumers

4. Tertiary consumers

5. Decomposers

Producers are green plants and algae which have the potential to fix atmospheric carbon dioxide and make glucose through a process called photosynthesis. 

Primary consumers are the animals which eat the green plants and algae. They are called herbivores, for example cow, rabbit, goat, deer.

Secondary consumers are the animals which prey upon herbivores. For example, Fox, dog, cat

Tertiary consumers are those animals which prey upon all animals irrespective of trophic levels, such as lion, tiger and hawk.

Decomposers are organisms which decay the dead organic matter formed by the death of organism, leaf fall etc. For example, fungi and microbes.

The energy trapped by green plants is transferred to primary consumers, then to secondary consumers and then to tertiary consumers. There is an energy loss at each level, which means only 10% of energy from one trophic level is transferred to the next. This is called 10% Rule. 

For example, if a producer has 1000 calories of energy, then the herbivore will get only 100 calories. When the herbivore is eaten by primary carnivores, they get only 10 calories. Finally the top carnivores will get only 1 calorie. At each trophic level, 90% of energy is lost for activities such as respiration, movement etc.

The following diagram explains the concept.

Ecological pyramids are of different types as given below.

1. Pyramid of Number: Graphical representation of number of organisms at each trophic level is called pyramid of number.

2. Pyramid of Energy: When the energy level of each trophic level is represented in an ecological pyramid, it is called pyramid of energy.

3. Pyramid of Biomass: When the biomass of organisms at each trophic level is represented in an ecological pyramid, it is called pyramid of biomass.

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FOOD CHAIN AND FOOD WEB

The process of life on earth follows a similar pattern for all organisms. All life forms require energy to run its day to day activities such as movement, communication, seeing and hearing. The ultimate source of energy for all living organisms is sun. The solar energy from the sun is trapped by the photosynthesizing plants, which are called as producers. Plants can trap up to 2% of solar energy reaching the earth. The light  energy trapped by plants is converted and stored as chemical energy in the form of biomolecules such as starch, glucose etc. 

SUN--------> LIGHT ENERGY---------> PLANTS---------PHOTOSYNTHEIS--------> CHEMICAL ENERGY

The herbivores eat photosynthesizing plants such as grasses, herbs etc. These herbivores which directly depend upon plants are called primary consumers. For example, grass hopper, rabbit, cow, goat. The herbivores are eaten by carnivores, such as snake, frog and lizard. These carnivores are eaten by large carnivores such as lion, tiger and hawk. Finally when all these organisms die, the dead body is eaten by detrivore animals such as millipedes, dung flies, worms etc or decayed by fungi and bacteria. 

This linear chain of organisms in the ecosystems, which are connected to each other by the process of eating and being eaten is called food chain.

The following are examples;

Maize---> Locust---> Lizard---> Snake

Corn--> Rat--> Owl.

Carrot-->Rabbit-->Fox--> Lion

Food chains are of two types:

1. Grazing food chain- The food chain that starts from  green plants and depend on solar radiation is called grazing food chain. Most of the food chains in the ecosystems are of this type.

2. Detritus food chain- The food chain that starts from a dead organic matter and less dependent on solar energy is termed detritus food chain. This mainly involves microbes, detrivores and their predators.

FOOD WEB 

In nature, we cannot find linear food chains, because organisms eat multiple types of food and eaten by different types of animals. In real, the process of eating and being eaten forms a web or organisms which are interdependent and forms a cluster of different food chains so that an interconnecting food web is formed. 

A food web is a collective representation of all food chains in an ecosystem.

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HARDY-WEINBERG EQUILIBRIUM

Hardy- Weinberg Equilibrium deals with the distribution of mendelian genes in a population of sexually reproducing individuals. 

The following are the main assumptions of the theory.

1. Allele frequencies in a population do not change from generation to generation. 

2. If the allele frequencies in a population with two alleles  at a locus are p and q, the distribution of the different allele combination will be p2, 2pq and q2. This frequency dostribution will not change from generation to generation, once the population is in Hardy Weinberg equilibrium.

p2+2pq+q2 = 1

also, p+q = 1

Where p2 (pp) is the frequency of homozygous dominant, 2pq is the frequency of heterozygous and q2 (qq) is the frequency of homozygous recessive. 

The above said conclusions of the Hardy- Weinberg equilibrium is applicable only under the following five conditions.

1. Natural selection is not operative in the population i.e., nature is not favoring a particular allele so that its frequency is not increasing in the population.

2. Mutation is not occurring, so that the formation of new alleles is prevented, which may other wise alter the frequency of the existing alleles.

3. Migration is not occurring, so that there is no inflow or out flow alleles from other places.

4. Population size is infinite, so that genetic drift is not happening. Genetic drift is the variation in gene frequency that occurs due to low number of individuals, as some fail to reproduce or does not perform in the expected ways.

5.Individuals in the population mate randomly, so that there is no bias to particular traits. 

MAJOR AND MINOR ETHNIC GROUPS OF INDIA -Part I

People of India Project was launched by Anthropological Survey of India on 2 October  1985. The objective of the project was to enlist all the communities of India. It was found that 4635 communities exist in India and reported 461 tribal ethnic communities. Nearly 40 endogenous tribes exist in the Western Ghat region.

Major ethnic communities of the Western Ghat region:

1. Kanis 

Kanis or Kanikkars, a major tribe of the southern Western Ghats dustributed in Tamilnadu and Kerala states of India. They inhabit the hill ranges in villages consisting of 5-55 families. The total number of individuals range from 1200 to 2000. Some of them are hunter-gatherers. They also collect honey from the forest, involve in inland fishing and cultivate crops. They use around 350 plants. The most important among them is Trichopus zeylanicus known popularly as "arogya pacha' in malayalam, which is considered equal to chinese ginseng.

2. Kurichyas

Kurichyas are an important tribe in Kerala, living in Wayanad and adjacent areas of Kannur. They form nearly 10% of tribal population of Kerala. They are specialist in archery and martial arts. They fought against the British during the Pazhassi rule of North Malabar. They live in clusters called mittam or tharavadu, their head is known as Karanavar or pittan. They are matrilineal society. They worship goddess Kaali. They bury the dead and speak 'kurichya' language. There are nearly 30000 members in Kurichya community. They use nealy 110 plants for varous purposes. At present they are living by means of agricukture

3. Paniyas

Paniya community inhabit Wayanad of Kerala and Nilgiris of Tamilnadu. They are short, dark-skinned, and have curly hairs. They are considered to be of African origin, but some workers disagree it. Traditionally they have been bonded laborers often treated as slaves and sold along with plantations by the owners. They have excellent knowledge in agricultural and ethnomedicinal practices. They live in bamboo huts and they form 22% of the tribals in Kerala. They cultivate cardamom, pepper, ginger, coffee etc. Women wear large ear rings made of palm leaf rolls. They practice animism, but also worship Bhagavati.

4. Pulayas

Pulaya community, also known as Cheruma, is one of the ancient tribal communities of Kerala. They are short, black, have long mandibles and with flat nose. They were basically hunter gatherers and supposed to be the first land owners of the area. They claim to be descendants of  the Chera dynasty, indicating their name 'cheruma'. They have excellent knowledge in agricultural practices. They worship in sacred groves or 'kavu' and deities include Kaali and Chaathan'. They also worship ancestral spirits.

5. Cholanaikkars

Cholanaikkar is one of the earliest tribes in Kerala. They are also called as "Malanaikkar" and their number is only 360 as per census. Their name is supposed to have evolved from Chola= Shola forest as they inhabit forest areas and naikkar means king. They are found in Silent Valley region of Kerala. They form one of the last hunter gatherer communities of southern India. They are short, well built and dark complexioned. They live rock shelters called 'Kallulai" and live in groups called "Chemmam".

6. Kadars

Kadar community is found in the Anamalais of Tamilnadu and Western Ghats of Kerala. They are one of the most ancient tribal communities of India. They live deep inside forests, hence called 'Kadars'. They are hunter gatherers. As per the latest census, there are 650 members in the Kadar community and classified by UNESCO as Particularly Vulnerable Tribal Group -PTG- that they are at the verge of extinction. The huts of Kadars are located in hill slopes. Each village has 15 huts made of bamboo. their weekly markets are called 'sandhi'. They make many items of bamboo, such as bamboo vessels. They collect honey and other forest products. They are patriarchial society, the bridegroom should gift a comb made of bamboo during the marriage ceremony. They wear ''thali' in a black beaded chain.They follow animism and worship some trees. Recently in 2019, they have been in news for their popular protest "Ithu Enkal Adaavi", against evacuating them from forest. 

7.Todas

Toda community live in the Nilgiri region of Tamilnadu and considered as a PTG by the UNESCO. Tode is the sacred tree of Todas from which their name is evolved. They claim themselves as descendants of Pandavas. Their language is 'toduvam'. Their huts are rainbow-shaped and have a very small entrance to avoid cold weather. Their village is 'Othaikkal mundu'. There are 75 mundus at Nilgiri with around 2000 people. Buffalo rearing is their profession, and they are pure vegetarians. Their ritual involve buffalo sacrifice. They are specialists in embroidery and the shal they make is called Puthukkuli'

8. Kotas

Kota tribe is also a PTG tribe and they inhabit in the Nilgiri hills of Tamilnadu. As per the last census their number is only 308. Kota village is called Kokkal and huts are called pai. They speak kota language. They are very good musicians and artisans. They worship Kambattarayan and kaali.

9. Kurumbas

Kuruumba tribe lives in Wayanad district of Kerala and Nilgiris of Tamilnad. They live in 5-6 families in small villages called 'motta' or kombai'. They are known for black magic and witch craft. They were basically hunter gatherers and shepherds. Now they work in plantations. Their language is called kurumba. They cultivate ragi and other millets. They have rich musical tradition.Women tattoo their forehead and use soapnut for bathing. The muthali or ejaman is the head of the village. Meeting of villagers is called Urukkoottam.

10. Irulas

Irula tribe is distributed in three states, Kerala, Tamilnadu and Karnataka. Traditionally they are snake catchers, rat catchers and honey collectors. They are popular after the release of the movie, Jai Bhim, which portrays the struggles of Irula life.

All the best!

Shijith Puthan Purayil

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STRUCTURE AND FUNCTION OF ECOSYSTEM

Ecosystem is an assemblage of organisms and the environment. It includes the living and non-living components. To understand the structure and function of ecosystem, you must be familiar with some basic terminologies in ecology.

1. Species: It is a unique organism with similar genetic identity. For example, all humans form a species called Homo sapiens 

2. Population: It is a group of individuals of same species. For example, a population of humans or cows.

3. Community: It refers to the populations of animals, plants and other organisms living in a specific region under similar environmental conditions. For example, mammals and plants in a forest, fishes and algae in a pond.

4. Ecosystem: It is a biological community of interacting organisms and their physical non-living environment. For example, a pond ecosystem.

Species --> Population ---> Community ---> Ecosystem

The concept of ecosystem was first introduced by A G Tansley (1935). According to Woodburry (1954) ecosystem is a complex in which habitat, plants, animals and other organisms are considered as one interesting unit, the materials and energy of one passing in and out of the others. 

Structure of Ecosystem

All ecosystems consist of the following basic components

1. Abiotic Component

    The abiotic component includes all non-living components of the ecosystem. For example,  soil, water, air, calcium carbonate, phosphates etc.

2. Biotic Component 

    The biotic component include all living organisms. For example, animals, plants and microbes. 

The biotic component can be grouped into two categories-

2.1. Autotrophic component/ Producers : These are organisms which can synthesize their own food using non living molecules. All green plants come under this category, they can fix radiant energy of sun and manufacture food in the form of molecules such as glucose and starch. 

2.2. Heterotrophic component/ Consumers: These are organisms which are unable to synthesize their food and depend on autotrophs. All non-green plants and all animals come under this category.

2.3. Decomposers: These are organisms which perform the role of decomposing all dead and decaying matter, there by ensuring the smooth function of bio-geo-chemical cycle. For example, fungi and bacteria. These are also known as Scavengers of Earth.

Producers

Any ecosystem is founded by the producers, which are capable of making their on food. They perform the one of the most fundamental reactions for sustaining on earth, called photosynthesis, that is synthesizing food using sun light. The green algae and cyanobacteria are assumed to be the first photosynthesizing organisms on earth.  All other organisms depend on producers such as herbs, shrubs and trees.

Consumers

Members of the ecosystem which consume the food synthesized by the producers are called consumers. For example, all animals. Deer, cow, goats etc eat the leaves of  grasses and other plants. Birds, monkeys etc eat fruits of the plants. Humans eat rice, wheat, ragi etc  They provide carbohydrates (Rice, wheat), fats (Nuts), proteins (green gram, bengal gram etc) and form steady source of food for all animals.

Consumers are classified as follows

1. Primary consumers: These are pure herbivores, which eat only plants or plant parts. eg: rabbit, deer, cow, buffalo, goat etc.

2. Secondary consumers: These are animals which eat herbivores. They include carnivores and omnivores. They are basically flesh eating animals, but they also eat plant parts. eg: crow, sparrow, fox, dog, cat, snake etc.

3. Tertiary consumers: They are the top carnivores which prey upon other carnivores, omnivores and herbivores. eg; tiger, lion, hawk, vulture etc.

Decomposers

Decomposers feed on dead and decaying matter. Imagine how the world would look if all the dead organisms remained without decaying! The decomposers recycle minerals back to earth. Hence they are called 'scavengers of earth'. Examples- Fungi and bacteria. 

Functioning of Ecosystem and energy transfer

Abiotic components such as air, water and soil provide the matrix for the synthesis and perpetuation of organic components. This process involves energy exchange and the energy comes from the sun in the form of light. The green plants convert inorganic matter to organic molecules such as glucose, starch, proteins and fatty acids. Hence they are called as producers. Photosynthesis and nitrogen fixation play a crucial role in fixing atmospheric carbon dioxide and nitrogen. Carbon is used to make glucose and nitrogen is used to make amino acids, which are very essential for sustaining life on earth. 

Energy gathered from sunlight by the producers in transferred to next levels such as herbivores which eat the plants. The energy transfer mainly occurs through food chains and food webs. It is a process of '

'eating and being eaten'. The energy received by herbivores from the producers is transferred to carnivores and omnivores. Finally the energy is transferred to top carnivores such as tiger and lion. When all the organism die, the dead matter is decomposed and recycled back to earth by the fungi and bacteria which also releases energy.

On average, only about 10% of energy stored as biomass in a trophic level is passed from one level to the next. This is known as ''the 10 percent rule''.

Functions of Ecosystem

There are mainly four functions of the ecosystem

1. Productivity

2. Decomposition

3. Energy flow

4. Nutrient cycling

1. Productivity

It is the rate of biomass production by any trophic level per unit area in unit time. It is measured as Weight (g/m2/year) or energy (kcal/m2/year).

Productivity is of two types- Primary productivity and secondary productivity.

Primary productivity

Primary productivity is the amount if biomass produced per unit area over a time of period by plants during photosynthesis. It is divided into gross primary productivity (GPP) and net primary productivity (NPP). 

The rate of production of TOTAL biomass by green plants during photosynthesis per unit area per unit time is known as gross primary productivity (GPP). Organisms use energy for their daily activities (respiration) from the energy synthesized during photosynthesis. The energy level remaining after respiration is known as net primary productivity (NPP) and this energy will be stored for future activity.

NPP= GPP- Respiration

Secondary Productivity

The rate of assimilation of organic matter at the level of consumers. It is the amount of energy available at the level of consumers.

2. Decomposition

It is the physical and chemical break down of complex organic matter formed when organisms die.  It is performed by fungi and bacteria. Termites, earth worms etc also feed on dead and decaying matter. Such organisms are called detrivores. 

Humification leads to the formation of soil. A dark colored organic substance called humus rich in cellulose and lignin. Humus is further degraded by microbes.

3. Energy flow

Plants capture sunlight, but they are able to capture only 2% of sunlight. The energy captured by the plants are transferred to next trophic levels. Only 10% of energy is transferred from one trophic level to the next.

4. Food Chain

Food chain is the process of eating and being eaten. Herbs are eaten by herbivores, herbovores are eaten by carnivores. Food chains form food webs, which in turn becomes a path for energy transfer from one trophic level to the next.

Grass--> Grass hopper--> Frog--->Snake

All the best!

Shijith Puthan Purayil

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