Environmental Biology (Part 1)

Environmental biology is the scientific study of the origins, functions, relationships, interactions, and natural history of living organisms and their populations, communities, and ecosystems in relation to dynamic environmental processes. It integrates principles from ecology, genetics, and conservation biology to understand how organisms adapt to and impact their environments, addressing issues like biodiversity, climate change, and ecosystem health.

The Earth’s life support system consists of four main components, collectively known as the ecosphere or biosphere. This refers to the global sum of all ecosystems, encompassing all living organisms and their physical environments on Earth. The ecosphere represents the zone of life on our planet, integrating interactions between the atmosphere, hydrosphere (water bodies), lithosphere (land), and the living organisms within these regions. It is a complex, self-regulating system where energy flows and matter cycles between its components, maintaining the conditions necessary for life.

Key aspects of the ecosphere include:

1. Atmosphere: The layer of gases surrounding the Earth, crucial for providing oxygen, carbon dioxide, and other gases necessary for life, as well as regulating temperature and weather patterns.

2. Hydrosphere: All of Earth's water, including oceans, lakes, rivers, and groundwater, which supports aquatic life and participates in the water cycle, influencing climate and weather.

3. Lithosphere or Geosphere: The Earth's solid outer layer, consisting of rocks, minerals, and soil, providing the foundation for terrestrial ecosystems and influencing geological and biological processes.

4. Biosphere: All living organisms, from microscopic bacteria to large mammals, interacting with each other and their environments, driving ecological processes like photosynthesis, respiration, and nutrient cycling.

These components are overlapping and interrelated with each other. A change in one is likely to result in change in one or more others.

The main components of the Earth system are interconnected by two key factors:

a) The one-way flow of energy: Energy flows from the Sun through living organisms via feeding interactions, into the environment, and eventually to outer space as heat. This flow drives many processes within the Earth's systems.

b) The cycling of nutrients: Nutrients cycle through various parts of the biosphere. Essential elements such as carbon, oxygen, hydrogen, nitrogen, phosphorus, and sulfur move through major biogeochemical cycles, supporting life by being recycled through ecosystems.

Systems in Physical Geography:

1. Open System: Both energy and matter can be exchanged with the surrounding environment. For example, a river system where water, sediment, and heat energy move in and out.

2. Closed System: Only energy is exchanged with the surrounding environment, but matter remains contained within the system. An example is the Earth’s atmosphere, where energy (like sunlight) enters and leaves, but the matter (gases) remains largely within the system.

3. Isolated System: Neither energy nor matter can pass in or out of the system. While true isolated systems are theoretical and rarely found in nature, a perfect example would be a completely sealed container where neither energy nor matter can exchange with the surroundings.

Ecology and Ecosystems

Ecology is the scientific study of the interactions between organisms and their environment. The term was first coined by the German biologist Ernst Haeckel in 1869, who defined it as "the study of the natural environment including the relations of organisms to one another and to their surroundings." Derived from the Greek words "oikos" (home) and "logos" (study), ecology encompasses various levels of biological organization, from individuals and populations to communities and ecosystems. E.P. Odum (1963) defined it as the “study of the structure and function of nature,” while modern ecologist Smith (1977) described it as “a multidisciplinary science which deals with organisms and their place to live, focusing on ecosystems.”

Ecology can be divided into two main subfields:

1. Autecology: The study of an individual species in relation to its environment. For example, examining the habitat, diet, and reproductive behavior of a particular fish species.

2. Synecology: The study of groups of organisms and their interactions within a specific environment. For example, studying the aquatic flora and fauna of a river system.

Ecosystems are specific environments where these interactions occur. The term ‘ecosystem’ was first coined in 1935 by the British ecologist Sir Arthur G. Tansley. E.P. Odum (1971) defined an ecosystem as “any unit that includes all of the organisms (i.e., the ‘community’) in a given area interacting with the physical environment so that a flow of energy leads to a clearly defined trophic structure, biotic diversity, and material cycles within the system.”

Ecosystem Structure

1. Abiotic Components: The non-living physical and chemical factors in an ecosystem, essential for the survival of living organisms. These include:

Inorganic Substances: Such as carbon dioxide, water, nitrogen, calcium, and phosphorus, which are involved in material cycles.

Organic Compounds: Including proteins, carbohydrates, amino acids, lipids, and humic substances, synthesized by biotic components.

Climatic Factors: Such as rainfall, light, temperature, humidity, wind, and air.

Edaphic Factors: Including soil minerals, topography, and pH.

2. Biotic Components: The living organisms in an ecosystem, including:

Producers: Mainly green plants that use solar energy to produce food through photosynthesis. This group includes green plants, algae, and phytoplankton. Chemosynthetic bacteria in deep ocean environments are also producers but use chemical energy to synthesize food.

Consumers: Organisms that depend on producers for food. They include herbivores (plant-eaters), carnivores (meat-eaters), omnivores (eat both plants and animals), and detritivores (feed on dead organic matter).

Bacterioplankton are microorganisms that can act as both primary producers and primary consumers in aquatic ecosystems.

Decomposers: Microorganisms like bacteria and fungi that break down complex organic matter into simpler inorganic forms.

Types of Ecosystems

Ecosystems can be broadly categorized into natural and man-made ecosystems, each with distinct characteristics. They can further be divided into aquatic and terrestrial ecosystems:

1. Natural Ecosystems: These ecosystems develop organically and include:

a) Aquatic Ecosystems: 

i) Marine Ecosystems: These include oceans, coral reefs, and estuaries. Marine ecosystems cover about 71% of the Earth's surface and are characterized by high salt concentrations. They support a diverse range of life forms, from microscopic phytoplankton to large marine mammals.

ii) Freshwater Ecosystems: These include lakes, rivers, ponds, and wetlands. Freshwater ecosystems have low salt concentrations and support species adapted to such environments. They are crucial for providing water resources and habitat for many organisms. The freshwater ecosystem mainly includes lentic, lotic, and wetlands.

Lentic: Water bodies that are slow or present in some areas are less than lentic. For example, ponds, lakes, pools, etc. Lakes are known as major water sources and are surrounded by the earth.

Lotic: Fast-moving water bodies fall below the lotic. For example, streams and rivers.

Wetlands: An area with long wet soil that falls under wetlands.

b) Terrestrial Ecosystems: 

i) Forests: A forest ecosystem is a system where diverse organisms interact with abiotic components like soil, water, and climate. It includes a variety of plants, microorganisms, animals, and other species. Forests act as carbon sinks, helping regulate Earth's temperature. Changes or deforestation can disrupt the balance of the ecosystem, potentially leading to its collapse.

Tropical Rainforest: These forests are characterized by extremely high biodiversity, surpassing that of any other ecosystem on Earth. They are located in regions with consistently high temperatures year-round and receive between 50 to 260 inches of rain annually. The dense canopy of tall trees creates a complex and multi-layered habitat, supporting a vast array of plant and animal species.

Tropical Deciduous Forest: Also known as tropical dry forests, these ecosystems feature a mix of shrubs, dense bushes, and a variety of trees. Unlike tropical rainforests, the trees in tropical deciduous forests shed their leaves during the dry season to conserve water. This adaptation helps them survive periods of lower rainfall.

Temperate Evergreen Forest: These forests are characterized by trees with needle-shaped leaves, such as pines and spruces, which help minimize water loss through transpiration. The vegetation also includes mosses and ferns. Temperate evergreen forests are found in regions with moderate climates, often with cool, moist conditions.

Temperate Deciduous Forest: Located in temperate regions with ample rainfall, these forests experience distinct seasons, including warm summers and cold winters. Trees in these forests shed their leaves in the fall to prepare for the winter months, and the forest floor is often covered with a rich layer of decomposing leaves.

Taiga: Also known as boreal forests, the taiga is found just south of the Arctic Circle. This biome is dominated by evergreen conifers like spruce, fir, and pine, which are adapted to the cold, nutrient-poor conditions of the region. The taiga experiences long, harsh winters and short, mild summers.

Boreal Forest: The boreal forest, or taiga, is notable for its significant accumulation of litter (dead plant material) on the forest floor. This type of forest covers large areas in the northern latitudes and is characterized by cold temperatures and a short growing season. The high litter mass contributes to the forest’s nutrient cycling and soil development.

ii) Grasslands: Grassland ecosystems are characterized by vast expanses of grasses with few trees or shrubs. They support a diverse array of herbivores, predators, and insects, contributing significantly to global biodiversity. These ecosystems are found in both tropical and temperate regions and are known for their distinct varieties. The two main types of grassland ecosystems are:

Savanna: Located in tropical regions, savannas experience seasonal dryness and have scattered individual trees. They support a large population of both predators and grazers.

Prairies: These temperate grasslands are devoid of large shrubs and trees. Prairies can be further categorized into mixed grass, tall grass, and short grass prairies, each supporting various grazing animals and other species.

iii) Deserts: The desert ecosystem, covering about 17% of the Earth's surface, receives less than 25 mm of rain annually. These regions have extreme temperatures, with high heat during the day and cold nights, and low water availability. Despite the harsh conditions, deserts support unique flora and fauna. Plants, like the spiny-leafed cactus, conserve water in their stems, while animals such as camels, reptiles, insects, and birds are specially adapted to survive in these arid environments.

iv) Tundras: Found in polar regions and high altitudes, tundras have cold temperatures, low biodiversity, and short growing seasons. Vegetation is mainly low shrubs, mosses, and lichens.

2.  Man-Made Ecosystems: These are created or significantly altered by human activity and include:

Agricultural Ecosystems: These include croplands, pastures, and plantations. Agricultural ecosystems are managed to produce food, fiber, and other resources, often resulting in reduced biodiversity compared to natural ecosystems.

Urban Ecosystems: These include cities and towns where human infrastructure, such as buildings and roads, dominates the landscape. Urban ecosystems often involve artificial environments and altered natural processes.

Industrial Ecosystems: These include areas affected by industrial activities such as mining, manufacturing, and energy production. They can lead to significant environmental changes and often require management to mitigate impacts.

Aquarium Ecosystems: These are controlled environments designed to house aquatic life, including fish, plants, and microorganisms. Aquariums are carefully managed to simulate natural aquatic conditions and often include features like filtration systems and temperature control.

Each type of ecosystem plays a crucial role in supporting life and maintaining ecological balance, whether naturally occurring or human-made. Understanding these ecosystems helps in managing and conserving the environment effectively.