Types of Environment – Geographical, Inner and Outer Environment

Environmental biology is one of the critical Biology Topics that involves understanding how humans impact the environment and how to address environmental issues.

Components of Environment – The Effect of Abiotic and Biotic Environment

Environment

The environment may be defined as the totality of surrounding conditions i.e., the air, water, and land in or on which people, animals, and plants live. Or, Environment means the external conditions, resources, stimuli, etc., with which an organism interacts.

Environment is the sum total of all biotic (living) and abiotic (non-living) factors that surround and practically influence the organism. Some components of the environment serve as resources (e.g., Soil, Water, etc.) while others act as regulatory factors (e.g., temperature, light, etc.). The different components of the environment are interlinked and interdependent. They function at local, regional, and global levels, e.g., local climate (microclimate), regional climate, and global climate. The environment varies from place to place due to variations in climate, soil type, and topography.

The biophysical environment is the biotic and abiotic surroundings of an organism or population and includes the factors that have an influence on their survival, development, and evolution. The expression “the environment” is often used to refer to the global environment, usually in relation to humanity, the number of biophysical environments is countless, given that it is always possible to consider an additional living organism that has its own environment.

The natural environment encompasses all living and non-living things occurring naturally on Earth or some region thereof. It is an environment that encompasses the interaction of all living species. The concept of the natural environment can be distinguished into the following components:

• Complete ecological units that function as natural systems without massive human intervention, including all vegetation, microorganisms, soil, rocks, atmosphere, and natural phenomena that occur within their boundaries.
• Universal natural resources and physical phenomena that lack clear-cut boundaries, such as air, water, and climate, as well as energy, radiation, electric charge, and magnetism, do not originate from human activity.

The natural environment contrasts with the built environment, which comprises the areas and components that are strongly influenced by humans. A geographical area is regarded as a natural environment.

Types of Environment

The environment is mainly divided into two main groups-

• Abiotic environment: Abiotic factors or climatic factors of the environment consist of light, temperature, water, soil, air, etc.
• Biotic environment: Consists of plants and animals. The subdivisions are the Atmosphere, Hydrosphere, and Lithosphere.

Atmosphere

The atmosphere of the earth serves as a key factor in sustaining the planetary ecosystem. The thin layer of gases that envelop the earth is held in place by the planet’s gravity. Dry air consists of 78% nitrogen, 21% oxygen, 1% argon, and other inert gases, such as carbon dioxide. The remaining gases are often referred to as trace gases, among which are the greenhouse gases such as water vapour, carbon dioxide, methane, nitrous oxide, and ozone. Filtered air includes trace amounts of many other chemical compounds. Air also contains a variable amount of water vapour and suspension of water droplets and ice crystals seen as clouds.

Many natural substances may be present in tiny amounts in an unfiltered air sample, including dust, pollen and spores, sea spray, volcanic ash, and meteorites. Various industrial pollutants also may be present, such as chlorine (elementary or in compounds), fluorine compounds, elemental mercury, and sulphur compounds such as sulphur dioxide (SO₂). The ozone layer of the earth’s atmosphere plays an important role in depleting the amount of ultraviolet (UV) radiation that reaches the surface. As DNA is readily damaged by UV light, this serves to protect life at the surface. The atmosphere also retains heat during the night, thereby reducing the daily temperature extremes.

Atmospheric Layers

Earth’s atmosphere can be divided into five main layers. These layers are mainly determined by whether temperature increases or decreases with altitude. From highest to lowest, these layers are:

• Exosphere: The outermost layer of Earth’s atmosphere extends from the exobase upward, mainly composed of hydrogen and helium.
• Thermosphere: The thermosphere starts below the exosphere, called the exobase. Its height varies with solar activity and ranges from about 350-800 km (1,100,000 – 2,60,000 ft). The International Space Station orbits in this layer, between 320 and 380 km.
• Mesosphere: The mesosphere extends from the stratopause to 80-85 km (170,000 ft). The stratopause, which is the boundary between the stratosphere and mesosphere, typically is at 50 to 55 km (160,000 to 180,000 ft).
• Troposphere: The troposphere begins at the surface and between 7 km (23,000 ft) at the poles and 17 km (56,000 ft) at the equator, with some variation due to weather. The troposphere is mostly heated by the transfer of energy from the surface, so on average the lowest part of the troposphere is the warmest and temperature decreases with altitude. The tropopause is the boundary between the troposphere and stratosphere.

Other Layers
Within the five principal layers determined by temperature are several layers determined by other properties.

• The ozone layer is contained within the stratosphere. It is mainly located in the lower portion of the stratosphere from about 15-35 km (49,000 – 110,000 ft), though the thickness varies seasonally and geographically. About 90% of the ozone in our atmosphere is contained in the stratosphere.
• The Ionosphere, the part of the atmosphere that is ionized by solar radiation, stretches from 50 to
  1,000 km (160,000 to 3,300,000 ft) and typically overlaps both the exosphere and the thermosphere. It forms the inner edge of the magnetosphere.
• The homosphere and heterosphere: The homosphere includes the troposphere, stratosphere, and mesosphere. The upper part of the heterosphere is composed almost completely of hydrogen, the lightest element.
• The planetary boundary layer is the part of the troposphere that is nearest the Earth’s surface and is directly affected by it, mainly through turbulent diffusion.

Spatial and Time Scales of Environment

Most organisms interact with their environment at several spatial time scales. A bacterium interacts with air, water, soil, etc., within small spatial and time scales of a fraction of a cubic centimeter and a day respectively. A tree, on the other hand, interacts with larger volumes of air, water, and soil at larger spatial and time scales.

Activities of living beings influence all components of the environment (atmosphere, hydrosphere, lithosphere) through the exchange of matter and energy. Organisms are also influenced by changes in the environment like seasonal changes in light, temperature, and humidity, e.g., leaf fall, seasonal changes in herbs, and phytoplankton.

Climate

It refers to the average weather of an area including the general patterns of atmospheric conditions, seasonal variations, and weather extremes over a long period. The climate of an area is determined by the temperature and rainfall. On the basis of variation in mean temperature along latitude, the main climatic zones of the entire earth are

• Tropical: (0°-20° latitude), temperature exceeds 24°C.
• Subtropical: (20°-40° latitude), temperature 17°C-24°C.
• Temperate: (40°-60° latitude), temperature 7°C-17°C.
• Arctic and Antarctic: (60°-80° latitude), temperature below 7°C.

Similar climatic zonation occurs with increasing altitude in the mountains. Variations occur in each climatic zone due to changes in annual and seasonal precipitation. Therefore, vegetation and soil types are determined by two climatic factors, temperature and precipitation.

The climate is a measure of the average pattern of variation in temperature, humidity, atmospheric pressure, wind, precipitation, atmospheric particle count, and other meteorological variables in a given region over long periods of time. Climate is different than weather, in fact, weather only describes the short-term conditions of these variables in a given region. Climate in a region is generated by the climate system, which has five components, those are atmosphere, hydrosphere, cryosphere, lithosphere, and biosphere. The climate of a location is affected by its latitude, terrain, and altitude, as well as nearby water¬bodies & their currents.

Weather

The short-term properties of the atmosphere such as temperature, humidity, rainfall, pressure, sunshine, cloud, wind, etc., at a given place and time, are called weather. It reflects hourly, daily or weekly changes in these properties. Weather varies from place to place at the same time and also at the same place at different times. Weather is the state of the atmosphere, the degree to which it is hot or cold, wet or dry, calm or stormy, clear or cloudy. Most weather phenomena occur in the troposphere, just below the stratosphere. Weather generally refers to day-to-day temperature and precipitation activity, whereas climate is the term for the average atmospheric conditions over longer periods of time. When used without qualification, “weather” is understood to mean the weather of Earth.

Weather is driven by air pressure (temperature and moisture) differences between one place and another. These pressure and temperature differences can occur due to the angle of sun rays at any particular spot, which varies by latitude from the tropics. The strong temperature contrast between polar and tropical air gives rise to the jet stream. Weather systems in the mid-latitudes, such as extratropical cyclones, are caused by instabilities of the jet stream flow. Because the earth’s axis is tilted relative to its orbital plane, sunlight is incident at different angles at different times of the year. On Earth’s surface, temperatures usually range from ±40°C (-40°F to 100°F) annually. Over thousands of years, changes in the Earth’s orbit affect the amount and distribution of solar energy received by the Earth and influence long-term climate and global climate change.

Differences between Weather and Climate:

Weather	Climate
1. It is a short-term property of the atmosphere.	1. It is a long-term property of the atmosphere.
2. It changes from place to place.	2. It is the same over a large area.
3. Its changes have little impact on the flora and fauna of a place.	3. It identifies and determines the flora and fauna of a place.

Microclimate

It represents the climatic condition prevailing at a local scale, or in areas of limited size, such as the immediate surroundings of plants and animals, e.g., Low temperature and more humid conditions inside the forest as compared & to nearby open areas.

The microclimate is a local atmospheric zone where the climate differs from the surrounding area. The term may refer to areas as small as a few square feet. (for example a garden bed) or as large as many square miles. Microclimates exist, for example, near bodies of water which may cool the local atmosphere, or in heavily urban areas where brick, concrete, and asphalt absorb the sun’s energy, heat up, and re-radiate that heat to the ambient air. the resulting urban heat island is a kind of microclimate. Microclimates can be found in most places.

Another contributing factor to microclimate is the slope or aspect of an area. South-facing slopes in the Northern Hemisphere and north-facing slopes in the Southern Hemisphere are exposed to more direct sunlight than opposite slopes and are therefore warmer for longer. The area in a developed industrial park may vary greatly from a wooded park nearby, as natural flora in parks absorbs light and heat in leaves, and a building roof or a parking lot just radiates back into the air.

Tall buildings create their own microclimate, both by overshadowing large areas and by channeling strong winds to ground level. Roof gardening, however, exposes plants to more extreme temperatures in both summer and winter. The presence of permafrost close to the surface in a crater creates a unique micro-climate environment.

In the desert, kangaroo rat lives in a hole where the humidity is 2-5 times higher than the outer environment. The temperature is near about 70°C in the air but the temperature is 28°C in the hole. In a polar plant Novosieversia glacialis, the temperature of the apical part of the root is 1°C, soil embedded stem is 19.4°C, apical bud is 15.5°C.

A Brief Note on Habitat and Niche

The place occupied by an organism, population, or community which is exposed to a particular combination of environmental factors, is called habitat. Usually, it is a large area in which a number of species are found, e.g., pond, desert, forest, river, valley, saline soil, etc. Plants and animals adapt themselves to specific conditions of their habitat, e.g., aquatic organisms, and halophytes. The characteristic adaptations related to a particular habitat are not found in organisms of another habitat. Thus, aquatic animals have some specific traits not found in terrestrial animals. Plants of saline soils (halophytes) have several characteristics not found in plants of normal soils.

Microhabitat:
It is a sub-division of habitat having a specific property, e.g., forest floor, tree canopy, tree trunk, edge of a pond, etc. A microhabitat is the small-scale physical requirement of a particular organism or population.

Monotypic habitat:
The monotypic habitat occurs in botanical and zoological contexts and is a component of conservation biology. In the restoration ecology of native plant communities or habitats, some invasive species create monotypic stands that replace and/or prevent other species, especially indigenous ones, from growing there. Dominant colonization can occur from retardant chemicals exuded, nutrient monopolization, or from lack of natural controls such as herbivores or climate, that keep them in balance with their native habitats.

The yellow star thistle, Centaurea solstitialis, is a botanical monotypic-habitat example currently dominating over 15,000,000 acres (61,000 km2) in California alone. The non-native freshwater zebra mussel, Dreissena polymorpha, that colonizes areas of the Great Lakes and the Mississippi River watershed, without its home-range predator control, is a zoological monotypic habitat example. Even though its name may seem to imply simplicity as compared with polytypic habitats, the monotypic habitat can be complex.

A habitat is made up of physical factors such as soil, moisture, range of temperature, and availability of light as well as biotic factors such as the availability of food and the presence of predators. A habitat is not necessarily a geographic area for a parasitic organism it is the body of its host or even a cell within the host’s body.

Niche
In ecology, a niche is a term describing the way of life of a species. Each species is thought to have a separate, unique niche. The ecological niche describes how an organism or population responds to the distribution of resources and competitors {e.g., by growing when resources are abundant, and when predators, parasites, and pathogens are scarce) and how it in turn alters those same factors (e.g., limiting access to resources by other organisms, acting as a food source for predators and a consumer of prey). The majority of species exist in a standard ecological niche. A premium example of a non-standard niche-filling species is the flightless, ground-dwelling kiwi bird of New Zealand, which exists on worms, and other ground creatures, and lives its life in a mammal niche. Island biogeography can help explain island species and associated unfilled niches.

The habitat together with the functions of a species in its ecosystem, is called the niche or ecological niche of the species. The term ‘niche’ was first introduced by Grinnel (1917). Each species of a community lives in a very specific part of a habitat and performs certain functions. Its role includes such factors as what it eats, what eats it, its range of movement, its nesting, and other requirements, the season and time of its activity, and its effect on other components of the community and on the physical environment.

Ecological niche depends on the species’ structural adaptations, physical responses, and behaviour. Habitat has several ecological niches and supports a number of species. An ecological niche is used by a single species. Two or more species can not use the same niche despite having a mutualistic association. Tadpoles and adult frogs occupy different ecological niches as the former is herbivorous aquatic while the latter is a carnivorous amphibian. Water bugs and water boatmen live in shallow edges of ponds but occupy different niches as the former is a predator while the latter is a scavenger.

Differences between Habitat and Niche:

Habitat	Niche
1. It is a specific locality where a community resides.	1. It is a component of a habitat that is governed by the functioning of an organism.
2. A habitat has a number of niches.	2. A niche does not have components.
3. A number of species may occur in a habitat.	3. A niche has only one species.
4. Habitat is delimited by a number of environmental factors.	4. A niche is determined by the operational requirements of the species within the limits of its tolerance.
5. It is the address of an organism.	5. It is a profession of an organism.

Niche is of Five Types:

• Fundamental niche
• Spatial or habitat niche
• Realized niche
• Multidimensional or hypervolume niche
• Tropic niche

1. Fundamental niche:
The fundamental niche of a species includes the total range of environmental conditions that are suitable for existence without the influence of interspecific competition or predation from other species.

2. Spatial or habitat niche:
Natural home or environment, the physical environment in which a species lives, is called a habitat niche, e.g., In a maple oak forest, the trunk of a tree is a habitat of seven species of millipedes and they draw nutrients from the trunk.

3. Realized niche:
The actual niche where a species flies in the face of interspecific competition is called a realized niche. It is the actual space that an organism inhabits and the resources it can access as a result of limiting pressures from other species.

4. Multidimensional or hypervolume niche:
A region defined by more than three dimensions, an ecological niche is often described as an n-dimensional hypervolume.

5. Trophic niche:
When the organisms are lived in the same place but the method of taking food is different, then it is called a trophic niche.

Ecological Equivalents and Guilds
The organisms that are found in different geographi¬cal regions of the world but occupy the same or similar niches are called ecological equivalents. Both owls and cats feed on shrews and mice. They occupy the same niche and are ecological equivalents as their habitats are different. Different types of herbivores present in different grasslands (rabbit and rat) are ecological equivalents. Guilds are groups of species that exploit the same biotic and abiotic resources in a similar way. Taxonomically related species found in the same habitat should be called a guild. The guild concept was originally proposed by Richard Root (1967) – an American ecologist. The environmental resources can be viewed as food, shelter, habitat, or nest sites.

Ecotone
An ecotone is a transition area between two biomes. It is where two communities meet and integrate. It may be narrow or wide, and it may be local (the zone between a field and forest) regional (the transition between forest), or regional (the transition between forest and grassland ecosystem).

Edge Effect
Edge effects refer to the changes in population or community structures that occur at the boundary of two habitats. Areas with small habitat fragments exhibit an especially pronounced edge effect that may extend throughout the range.

Ecological Indicator
Ecological indicators are used to communicate information about ecosystems and the impact human activity has on ecosystems to groups such as the public or government policymakers.
Some ecological indicators are listed below:

Species	Indicator
1. Utricularia, Wolffia	Water Pollution
2. Hydrilla Verticillata	Hard Water
3. Lippia Nodiflora	Nitrate Water
4. Spermacoce Stricta	Ironated Soil
5. Mayfly	O2 content in water
6. Argemone Mexicana	Flooded Soil