LIFE ON EARTH

It is believed that, Earth was formed 4.5 Billion years ago from the mixture of dust and gases around the sun. Life on earth started around 3.5 billion years ago. The young earth doesn’t have a life supporting environment containing CO₂, CH₄ methane gas, water vapor, N₂ nitrogen, NH₃ ammonia, H₂S hydrogen sulfide. It took almost 1 billion years for the first life form to appear. Through biopsies (Life created naturally from non living matter) life was created. The early living organisms are simple and Unicellular.

The course of evolution from unicellular organisms to multicellular advanced organisms happened only because of changes in Earth’s environment.

Living organisms are found on all regions of earth-Equator to Poles, Bottom of sea to several kilometers in atmosphere, Deserts to Tundras.

Realms of Earth

Any biogeographical division of the earth surface is called Realm. There are three realms on earth.

Lithosphere – Terrestrial portion of Earth.

Atmosphere – Gaseous envelope around Earth.

Hydrosphere – Aquatic portion of Earth.

The living organisms interacting with other realms of Earth constitutes Biosphere.

Biosphere is the zone of life including all the living organisms and their interactions with the environment surrounding them. Biosphere is also known as Ecosphere.

Life on earth is possible on lithosphere, hydrosphere and atmosphere, and organisms move freely from one realm to another. The components (Biotic) of biosphere are crucial elements of environment and they interact with other components like water, soil and air(Abiotic). All the biotic factors are effected or influenced by abiotic  factors like sunlight, temperature and moisture.

Ecology

The term ecology is derived from the Greek  language “oikos” meaning ‘house’ combined with the word “logy” meaning ‘the study of’. Ecology was coined by Ernst Haeckel.

Definition: The scientific study of interaction of organisms with their physical environment and with each other.

A healthy interaction between biotic and abiotic components brings balancing of environment.

A Habitat is a dwelling place where an organism resides. It constitutes physical and chemical factors of environment.

A system consisting of biotic and abiotic components is known as Ecosystem.

Definition: All the interacting organisms in any geographical area together with non living constituents of the environment.

All the components of ecosystem are interrelated and interdependent. Many different types of ecosystems are present based on different climatic conditions. The process of adaptation of plants and animals to different ranges of environment is called Ecological Adaptations.

There are two types of ecosystems –

1. Terrestrial Ecosystem
2. Aquatic Ecosystem

Terrestrial Ecosystem is further classified into Biomes. A Biome is a large collection of plants (Flora) and animals (Fauna) present in a large geographical area. Biomes are characterized by climate, vegetation, animal and general soil type. No two biomes are similar. The climate determines the boundaries of a biome and abundance of living organisms found. The most important climatic factors are temperature and precipitation.

Definition of Biome: The total assemblage of plant and animal species with in specific conditions. These specific conditions include rainfall, temperature, humidity and soil conditions.

Some of the major biomes are Forest, Grassland, Desert and Tundra Biomes.

Types of Biomes

Aquatic ecosystems are classified into Marine and Fresh Water Ecosystem.

Marine Ecosystem include oceans, estuaries and corral reefs.

Fresh Water Ecosystem include lakes, ponds, streams, marshes and rivers.

According to some ecologists aquatic ecosystem can also be classified into,

Lentic Ecosystem – It is still water ecosystem, it includes ponds, lakes, ditches, seasonal pools, marshes. Based on the penetration of sunlight in lakes and ponds, they are able to support a diverse range of water plants.

Lotic Ecosystem – It is flowing water ecosystem, it includes moving water bodies like creek, brook, river, spring, stream.

Structure and Functions of Ecosystem

The structure of an ecosystem is characterized by the description and organization of available biotic and abiotic factors.

Abiotic factors include rainfall, temperature, sunlight, soil, atmospheric humidity, inorganic substances like carbon dioxide, water, nitrogen, calcium, phosphorus, potassium.

Biotic factors include plants, animals and microorganisms in different levels like producers, primary consumers, secondary consumers, tertiary consumers and decomposers.

Producers – All photosynthetic organisms. Like plants, green algae, etc.

Primary Consumers – Also known as herbivores. Like cow, goat, deer, etc.

Secondary Consumers – Also known as carnivores. Like tiger, snakes, crocodile, etc.

Tertiary Consumers – Some carnivorous animals feed on carnivores occupying the top level in food chain. They are called climax/top carnivores. Like hawk, mongoose, etc.

Decomposers – Organisms that feed on dead and decaying matter are called Decomposers. Example, crow, vulture, some bacteria.

The producers are consumed by primary consumers which in turn are consumed by secondary consumers further the secondary consumers are consumed by the tertiary consumers. The decomposers feed on the dead at each and every level. They break down them into various substances like nutrients, organic and inorganic salts essential for soil fertility. Organisms of an ecosystem are interlinked through a food chain. For example,  A plant eating beetle is eaten by a frog which in turn is eaten by a snake. The snake as a secondary consumer, is further eaten by a hawk. This sequence of eating and being eaten and the transfer of energy from one level to another is called a food chain.

Transfer of energy that occurs during the process of a food chain from one level to another is called flow of energy.

How ever food chains are not isolated from one another. For example, a mouse feeding on grains may be eaten by different secondary customers and these carnivores are may be eaten by other different tertiary consumers. In such conditions each of the carnivores may consume more than one type of prey. As a result the food chains get interlinked with one another. This interconnecting network of species/food chains is called a food web.

Generally two types of food chains are recognized: Grazing food chain, Detritus food chain.

In Grazing food chain the first level starts with the plants as producers (autotrophs) and ends with carnivores as consumers with the herbivores being at the intermediate level. There is a loss of energy at each level which may be through respiration, excretion or decomposition. The levels involved in a food chain range between three to five and energy is lost at each level.

A detritus food chain starts with dead organic matter. This food chain is based on autotrophs energy capture initiated by grazing animals and involves the breakdown or decomposition of organic waste and dead matter derived from grazing food chain.

Biogeochemical cycles.

The sun is the basic source of energy on which all life depends. This energy initiates life process in the biosphere through photosynthesis, the main source of food and energy for green plants. During photosynthesis carbon dioxide is converted into organic compound and oxygen. Out of the total solar insulation that reaches the earth surface (173,000 Terawatts) only 0.1% of it is fixed through photosynthesis. More than half is used for plant respiration and the remaining is temporarily stored or shifted to other portions of the plant.

The living organisms exist and survive in a diversity of associations. Such survival involve the presence of systemic flows like flow of energy, water and nutrients. These flows show variations in different parts of the world in different seasons. Recent studies showed that the atmosphere and hydrosphere are composed of approximately the same balance of chemical components from 1 billion years. This balance of chemical elements is maintained by a cyclic passage through the tissues of plants and animals. The cycle starts by observing the chemical elements by the organism and is returned to the water and soil through decomposition. These cycles are energized by solar energy.

Definition: The pathway by which a chemical substance cycles the biotic and abiotic compartments of earth. 

The movements of chemical elements of the biosphere between organisms and the environment are called biogeochemical cycles. Bio meaning life or living organisms, Geo meaning rocks, soil, air and water of earth.

There are two types of biogeochemical cycles: Gaseous and Sedimentary cycles.

In the gaseous cycle the main reservoir of nutrients is the atmosphere and ocean.

In sedimentary cycle the main reservoir is soil and sedimented rocks of earth’s crust.

Water Cycle

The water cycle, also known as the hydrological cycle, describes the continuous movement and exchange of water among the Earth's atmosphere, land, oceans, and living organisms. It involves various processes that ensure the circulation and distribution of water across the planet.

Key components and processes of the water cycle include:

1. Evaporation: The process where water from oceans, rivers, lakes, and the Earth's surface changes into water vapor due to solar heat. This vapor rises into the atmosphere.

2. Condensation: As water vapor rises, it cools in the atmosphere and condenses into tiny water droplets or ice crystals, forming clouds.

3. Precipitation: When condensed water droplets in clouds become heavy enough, they fall back to the Earth's surface as precipitation. This can include rain, snow, sleet, or hail.

4. Runoff: Precipitation that falls on the land can flow across the surface, collecting in rivers, streams, and eventually reaching oceans or other bodies of water. Some precipitation also infiltrates the ground to become groundwater.

5. Transpiration: Plants absorb water from the soil through their roots. This water then moves through the plant and is released into the atmosphere through tiny pores in the leaves, a process known as transpiration.

6. Sublimation and Melting: Sublimation occurs when ice or snow changes directly into water vapor without melting. Melting is the process where ice or snow changes into liquid water.

7. Percolation: The movement of water through the soil or porous materials, eventually reaching the groundwater reservoirs.

8. Storage: Water can be stored in various forms including oceans, ice caps, glaciers, rivers, lakes, groundwater, and as moisture in the soil.

The water cycle is a continuous and interconnected process that maintains the balance of water on Earth. It's crucial for supporting life, regulating climate, shaping landscapes, and influencing weather patterns across the planet. Understanding the water cycle is essential for managing water resources sustainably and predicting environmental changes

Carbon Cycle

The carbon cycle describes the movement and exchange of carbon in various forms (carbon dioxide, organic compounds, and carbonates) among the atmosphere, oceans, biosphere (living organisms), and geosphere (Earth's rocks and sediments). It's a vital process for sustaining life and regulating the Earth's climate.

Key components and processes of the carbon cycle include:

1. Photosynthesis: Plants and some microorganisms absorb carbon dioxide from the atmosphere during photosynthesis. They convert this carbon dioxide into organic compounds like glucose, releasing oxygen as a byproduct.

2. Respiration: Organisms, including plants, animals, and microorganisms, respire by breaking down organic compounds to obtain energy. This process releases carbon dioxide back into the atmosphere.

3. Decomposition: When plants and animals die, their organic matter is broken down by decomposers (bacteria, fungi), releasing carbon dioxide back into the atmosphere or into the soil.

4. Fossilization: Over millions of years, some organic matter may be buried and compressed, forming fossil fuels such as coal, oil, and natural gas. When these fuels are burned for energy, carbon that was stored for millions of years is released as carbon dioxide into the atmosphere.

5. Oceanic Absorption: The oceans act as a carbon sink, absorbing carbon dioxide from the atmosphere. Marine organisms also play a role by using carbon dioxide for shell and skeletal formation.

6. Weathering and Erosion: Carbon dioxide dissolved in rainwater forms a weak carbonic acid that can break down rocks, releasing carbonates. These carbonates can be transported via rivers to the oceans, where they become sedimentary rocks over time.

7. Volcanic Activity: Volcanoes release carbon dioxide and other gases stored in Earth's mantle into the atmosphere.

8. Human Activities: Human actions, particularly the burning of fossil fuels, deforestation, industrial processes, and land-use changes, have significantly altered the natural carbon cycle by releasing additional carbon dioxide into the atmosphere.

Understanding the carbon cycle is crucial for comprehending the balance of carbon in the atmosphere, its impact on climate change, and the role it plays in supporting life on Earth. Human-induced changes to the carbon cycle are contributing to increased atmospheric carbon dioxide levels and influencing global climate patterns

Oxygen Cycle

The oxygen cycle describes the movement of oxygen through various processes and reservoirs on Earth, involving the atmosphere, biosphere, lithosphere, and hydrosphere. It's a vital cycle that sustains life by providing the necessary oxygen for respiration in living organisms.

Key components and processes of the oxygen cycle include:

1. Photosynthesis: Plants, algae, and certain bacteria produce oxygen as a byproduct during photosynthesis. They use sunlight, carbon dioxide, and water to create glucose and release oxygen into the atmosphere.

2. Respiration: Living organisms, including plants, animals, and microorganisms, use oxygen for cellular respiration, breaking down organic compounds to release energy and produce carbon dioxide and water as byproducts. This process occurs in both plants (during the night or when photosynthesis is not possible) and animals.

3. Atmospheric Exchange: Oxygen moves between the atmosphere and other Earth systems through diffusion and exchange. It's in constant circulation through the air we breathe and the gases exchanged in photosynthesis and respiration.

4. Decomposition: When organic matter decomposes, microorganisms consume oxygen while breaking down complex organic molecules, releasing carbon dioxide, water, and nutrients. This process consumes oxygen and affects its availability in ecosystems.

5. Oxygen Dissolution in Water: Oxygen dissolves in water through diffusion at the air-water interface, primarily in oceans, lakes, and rivers. Aquatic organisms, such as fish and aquatic plants, use dissolved oxygen for respiration.

6. Combustion: The burning of fossil fuels, wildfires, and other combustion processes consume oxygen and release carbon dioxide and other gases into the atmosphere.

7. Human Influence: Human activities, including deforestation, industrial processes, and pollution, can disrupt the oxygen cycle by reducing the number of plants that produce oxygen and increasing carbon dioxide levels through emissions.

The oxygen cycle is closely linked to the carbon cycle and plays a critical role in maintaining the balance of gases necessary for life on Earth. Understanding and preserving this cycle are essential for sustaining ecosystems and ensuring the availability of oxygen for all living organisms

Nitrogen Cycle

The nitrogen cycle describes the movement and transformation of nitrogen through various processes and forms in the atmosphere, soil, water, and living organisms. Nitrogen is an essential element for the synthesis of proteins, DNA, and other organic compounds necessary for life.

Key components and processes of the nitrogen cycle include:

1. Nitrogen Fixation: Nitrogen gas (N2) makes up about 78% of Earth's atmosphere, but most organisms cannot use this form directly. Certain bacteria, known as nitrogen-fixing bacteria, convert atmospheric nitrogen into ammonia (NH3) or ammonium ions (NH4+) through biological nitrogen fixation. Some of these bacteria live symbiotically in the root nodules of leguminous plants, while others are free-living in the soil.

2. Nitrification: Ammonia or ammonium ions in the soil can be converted into nitrite (NO2-) and then into nitrate (NO3-) by nitrifying bacteria. This process is called nitrification and makes nitrogen compounds more accessible to plants.

3. Assimilation: Plants and other organisms take up nitrogen in the form of nitrate and ammonium to build proteins, nucleic acids, and other essential organic molecules.

4. Ammonification: When organisms die or produce waste, decomposers break down organic nitrogen compounds into ammonium through ammonification. This process releases ammonia back into the soil.

5. Denitrification: Certain bacteria perform denitrification, converting nitrates in the soil back into atmospheric nitrogen (N2) or nitrous oxide (N2O), which is released back into the atmosphere. This completes the cycle by returning nitrogen to its atmospheric form.

6. Human Activities: Human activities, such as the use of synthetic fertilizers in agriculture, burning fossil fuels, and industrial processes, have significantly altered the nitrogen cycle. These activities have increased the amount of reactive nitrogen in the environment, leading to environmental issues such as eutrophication in water bodies and air pollution.

The nitrogen cycle is crucial for maintaining the availability of nitrogen in ecosystems, sustaining plant growth, and ensuring the proper functioning of biological processes. Understanding and managing this cycle are essential for sustainable agriculture, ecosystem health, and minimizing environmental impacts associated with nitrogen pollution

Equilibrium

Ecological balance is defined as a state of dynamic equilibrium within a community of organisms in which genetic, species and ecosystem diversity remain stable and subject to gradual changes through natural succession.It happens only diversity of the living organisms remain stable.Gradual changes take place only through natural succession.Ecological balance can also be explained as a stable balance in the number of each species in an ecosystem.This occurs through competition and cooperation among organisms where population remains stable.This balance is brought by the fact that certain species compete with one another determined the environment in which they grow.This balance can also be attained by the fact that some organisms depend on others for food and sustenance.for example in grasslands  the herbivores are found in plenty.On the other hand ,the carnivores which are not usually in large numbers hunt and feed on herbivores, thereby controlling herbivore population.

Any disturbance in the native forests like clearing for shifting cultivation usually changes the species distribution.This change is due to competition of secondary forest species like grasses, bamboos, pines overtake the native species changing the forest structure.This change in original form into new form is called succession.

The equilibrium in an ecosystem or ecological balance is disturbed by the introduction of new species, natural calamities, human causes.Human interference affected the balance of plant communities leading to disturbance in ecosystem .These disturbances caused many secondary successions.Human interference on earth’s resources created lot of disturbances .These disturbances caused adverse effects to the general environment n destroyed the originality of earth.Ecological imbalances brought many natural calamities like floods, landslides, climatic changes, disease etc.

There is a close relationship between plant and animal communities, biotic and  abiotic factors in a particular habitat.Diversity of life in a particular area can be employed as an indicator of the habitat factor.Proper knowledge of these factors provide strong base of protecting and conserving the ecosystem.