AIOU Course Code 1421-1 Solved Assignment Autumn 2022


Code : 1421

Course : Introduction to Environment

Assignment No. 1

Semester : Autumn 2022

Program : BA

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Q. l      Define the following terms:             

            1.         Lithosphere

Lithosphere is the outer mantle of the solid earth. It consists of minerals occurring in the earth’s crusts and the soil e.g. minerals, organic matter, air and water.


            2.         Fertility of Soil

The fertility of soils is rapidly depleting. The data generated by public and private organizations reflect the general agreement about the deficiency of nitrogen in 100 per cent soils. In case of phosphorus, more than 90 per cent soils are deficient. Potassium deficiency in soils, not a soil fertility problem earlier, is increasing rapidly due to discriminate use of only nitrogenous and phosphate fertilizers.


            3.         Irreversible Damage

In contrast, ecologists view large scale ecological processes such as evolution, adoption and biogeochemical cycle as the most important aspect of nature. This view is termed as ecocentric as it considers ecological processes as whole more important rather than its individual parts. If you kill individual organisms, you deny it a few months or years of life but if you eliminate an entire species or a whole landscape, you have destroyed something that took millions of years to create. Such a destruction that took millions of years to establish is known as irreversible damage.


            4.         Egocentric

The term egocentric is a concept that originated within Piaget’s theory of childhood development. Egocentrism refers to someone’s inability to understand that another person’s view or opinion may be different than their own.


            5.         Commensalism

Commensalism defines the co-action in which two or more species are associated and one species at least, derives benefit from the association, while the other associates are neither benefited nor harmed.


            6.         Velamen

Dust is also a source of the nutrients. Roots of epiphytes often store water in a special tissue, called velamen.


            7.         Jet Stream

Jet streams are relatively narrow bands of strong wind in the upper levels of the atmosphere. The winds blow from west to east in jet streams but the flow often shifts to the north and south. Jet streams follow the boundaries between hot and cold air.


            8.         Polar Tundra

ET or polar tundra is a climate where the soil is permanently frozen to depths of hundreds of meters, a condition known as permafrost.


            9.         Cfa

Cfa – humid subtropical: The humid subtropical climate (Cfa) has hot muggy summers and frequent thunderstorms. Winters are mild and precipitation during this season comes from mid-latitude cyclones.


            10.       Soil Water Management

soil water management is to encourage water movement into rather off the soil. If the water is allowed to penetrate, the soil can serve as a ‘reservoir’ for future plant uptake.


Q.2      Differentiate between the following terms:            

                        i.          Soil texture and soil structure

   Soil texture

                                Soil structure

1. Soil texture refers to the relative proportion of sand, silt and clay.

1. Soil structure refers to the arrangement of sand, silt and clay into a definite pattern.

2. Example: Loam, sandy, clay etc.

2. Example: Strong coarse, angular blocky etc.

3. It is a basic property of soil and can’t be changed easily.

3. It is easily liable to change under different management practices such as ploughing, liming, manuring etc.

4. It can be identified by finger feel method.

4. It can be identified by its physical appearance.

5. Soil texture is formed due to weathering.

5. Soil structure is formed due to physical, chemical and biological activities.

6. Based on soil texture soils have been grouped into 12 textural class.

6. Based on soil structure soils have been grouped into 5 structural class.

7. Loam and silt loam texture are good for agriculture.

7. Granular and crumbly structure are good for agriculture.


`                       ii.         Natural and Artificial Ecosystem

There are several differences between natural and artificial ecosystems, including sustainability, diversity and purpose. A natural ecosystem has a diverse amount of species and plants, whereas artificial ecosystems are limited. Natural ecosystems are self-sustaining and result from spontaneous natural reaction, while artificial ecosystems require the assistance of humans.


                        iii.        Zooplankton and Phytoplankton

Following are some of the important differences between Phytoplankton and Zooplankton.




What are they?

Found in fresh and marine water, they are plant-like aquatic microbes.

They are animal-like aquatic entities. Also, they are larval phases of other life forms.


Blue-green algae, cyanobacteria, dinoflagellates, diatoms

Crustaceans such as copepods, krill, protozoans


Upper sunlight layer of the water bodies (euphoric).

Found in deeper ocean beds where sunlight does not reach.


When they grow in a group, cloudy patches are formed, otherwise brown in colour.

Mostly translucent and can be found in varied shapes and colours.


Lots of oxygen is released.

Oxygen is consumed.

Mode of nutrition

Through chemosynthesis or photosynthesis produces its own food.

Consumes other zooplanktons and phytoplanktons.

Position in the aquatic food chain

Primary producers

Primary or secondary consumers


                        iv.        Positive and Negative interaction

·         These connections can be beneficial—like mutualism or commensalism—or harmful—like when one species eats another. Other harmful interactions lead to the presence of one species in or on the host, a different organism.

·         Positive interactions are friendly relationships between species that improve at least one species’ development, reproduction, and survival without having an adverse effect.

·         Negative interactions might involve, among other things, stifling the expression of emotions, criticising others, violating their privacy, meddling in their business, or failing to deliver on a promise of assistance.

·         By grinning at your child, you can convey warmth in your relationship and positive attention to your youngster. using compassionate facial expressions and eye contact. embracing your child is one method of demonstrating physical affection.

·         Trust, respect for one another, and active engagement are characteristics of productive working interactions.


                        v.         Mantle and core

Mantle – The portion of the interior beyond the crust is called as the mantle. The mantle is about 2900kms in thickness. Nearly 84% of the earth’s volume and 67% of the earth’s mass is occupied by the mantle.

Core – It is the innermost layer surrounding the earth’s centre. The core constitutes nearly 15% of earth’s volume and 32.5% of earth’s mass. The Core consists of two sub-layers: the inner core and the outer core.


Q.3      What are the three major types of water erosion? How can erosion be controlled?     

Types of Water Erosion

Land depletion caused by water occurs in several stages and is manifested in different ways according to the factors that caused it. Below are the common water erosion types that can affect soil if not prevented promptly.

Splash Erosion

This is the first stage in the erosion process that is caused by rain. Raindrops basically “bombard” the exposed and bare land, moving its particles and destroying the structure of the top layer. Eventually, it causes the formation of surface crusts, negatively affects soil infiltration ability, and eventually results in runoff formation.

Sheet Erosion

This type of soil degradation by water occurs when the rainfall intensity is greater than the soil infiltration ability and results in the loss of the finest soil particles that contain nutrients and organic matter. It usually follows after crusting that is caused by the previous stage of soil damage by water. If not prevented timely, one of the most negative effects of sheet erosion will be the formation of rills.

Rill Erosion

Rill erosion follows after, when the water concentrates deeper in the soil and starts forming faster-flowing channels. These channels can be up to 30cm deep and cause detachment and transportation of soil particles. Rill erosion can eventually evolve into gully erosion. That is when the rills become at least 0.3m deep

Gully Erosion

This is an advanced stage of land damage by water when the surface channels are eroded to the extent when even tillage operations wouldn’t be of any help. Apart from causing huge soil losses and destroying farmland, it also results in reduction of water quality by increasing the sediment load in streams.

Tunnel Erosion

This is the so-called “hidden” type of land degradation by water that can cause severe disruption even before any signs are evident to the eye. It begins when large water mass starts moving through the structurally unstable soil. That is why it is usually the biggest threat to sodic soil. The manifestations of tunneling would be a series of tunnels beneath the soil surface.


How can erosion be controlled        

Surface cover

Surface cover is the key to erosion control in grazing lands. It prevents erosion by maintaining the soil so it can absorb rainfall.

A well-managed pasture with good cover will ensure that runoff spreads rather than concentrates. Bore drains, tracks, roads, cattle pads and fences concentrate runoff, so careful planning is required to ensure that property improvements are located where they will not contribute to erosion.

The critical level of cover for pastures in tussock grasslands is about 40% cover and 1000 kilograms per hectare of dry grass. Ideally, this level of cover will exist at the beginning of the summer storm season.

The ideal stocking rate is flexible, and stock numbers should match available feed. Regular monitoring of pastures is necessary to achieve this. Long-term weather forecasting, using predictive tools such as the Southern Oscillation Index (SOI), has improved the options available for predicting droughts.

Opportunistic spelling

Opportunistic spelling should also be part of a grazing strategy. A total spell in a good year may be required to allow desirable grasses to recover from past grazing. Grazing pressure can also be managed by locating watering points away from areas vulnerable to erosion.


Fire is useful for controlling woody weeds but it needs to be managed carefully. Regular burning of pastures will further reduce ground cover and promote runoff and erosion.


Q.4      a.         Write a detail note on the Structure of Ecosystem.           

The structure of an ecosystem is basically a description of the species of organisms that are present, including information on their life histories, populations and distribution in space. It is a guide to who’s who in the ecosystem. It also includes descriptive information on the non-living (physical) features of environment, including the amount and distribution of nutrients. An ecosystem typically has two major components:

1. Abiotic or Non-living Components

Abiotic component of the ecosystem comprises three sorts of components:

a Climatic condition and physical factors of the given region includes air, water, soil, temperature, light (i.e., its duration and intensity), moisture (relative humidity), pH, etc.

b Inorganic substances such as water, carbon (C), nitrogen (N), sulfur (S), phosphorus (P) and so on, all of which are involved in cycling of materials in the ecosystem. The amount of these inorganic substances, present at any given time in an ecosystem, is designated as the standing state or standing quality.

c Organic substances such as proteins, carbohydrates, lipids, humus, etc., present either in the biomass or in the environment.

2. Biotic or Living Components

In an ecosystem, the living organisms are distinguished on the basis of their nutritional relationships, which are discussed as follows: a Autotrophic component: Autotrophic (auto = self; trophic = nourishing) component of ecosystem includes the producers which convert solar energy into chemical energy that becomes locked in complex organic substances such as carbohydrate, lipid, protein, etc. (Recall the concept of photosynthesis given to you in unit no. 1 – Box 1.3) with the help of simple inorganic substances such as water and carbon dioxide.

Autotrophs fall into following two groups:

 Photoautotroph: which contain green photosynthetic pigment chlorophyll to trap the solar or light energy of sun, e.g., trees, grasses, algae, and photosynthetic bacteria and cyanobacteria (blue green algae).

 Chemoautotroph: these use energy generated in oxidation – reduction process, but their significance in the ecosystem as producers is minimal, e.g. microorganisms such as Beggiatoa, sulfur bacteria, etc. (It is important to note that during the study of ecosystem when the term autotrophs or autotrophy is used, generally photoautotrophy is meant).

b Heterotrophic component: In the heterotrophic (hetero = other; trophic = nourishing) organisms predominate the activities of utilization, rearrangement and decomposition of complex organic materials.

Heterotrophic organisms are also called consumers, as they consume the matter built up by the producers (autotrophs). The consumers are of following two main types:

 Macroconsumers: These are also called phagotrophs (phago = to eat) and include mainly animals which consume other organisms or chunks of organic matter. Depending on their food habits, consumers may either be herbivores (plant eaters) or carnivores (flesh eaters).

Herbivores live on living plants and are also known as primary consumers e.g., insects, zooplanktons (protozoa, jelly fish, worms etc.) and higher animals (deer, cattle, elephant, etc.).

Secondary and Tertiary consumers are carnivores or omnivores, e.g., insects such

as dragon flies; spiders and large animals such as tiger, lion, leopard, wolf, etc.


            b.         How have volcanic emission contributed to the formation of atmosphere.

The gases and dust particles thrown into the atmosphere during volcanic eruptions have influences on climate. Most of the particles spewed from volcanoes cool the planet by shading incoming solar radiation. The cooling effect can last for months to years depending on the characteristics of the eruption. Volcanoes have also caused global warming over millions of years during times in Earth’s history when extreme amounts of volcanism occurred, releasing greenhouse gases into the atmosphere.

Even though volcanoes are in specific places on Earth, their effects can be more widely distributed as gases, dust, and ash get into the atmosphere. Because of atmospheric circulation patterns, eruptions in the tropics can have an effect on the climate in both hemispheres while eruptions at mid or high latitudes only have impact the hemisphere they are within.

Below is an overview of materials that make their way from volcanic eruptions into the atmosphere: particles of dust and ash, sulfur dioxide, and greenhouse gases like water vapor and carbon dioxide.

Particles of Dust and Ash 

Volcanic ash or dust released into the atmosphere during an eruption shade sunlight and cause temporary cooling. Larger particles of ash have little effect because they fall out of the air quickly. Small ash particles form a dark cloud in the troposphere that shades and cools the area directly below. Most of these particles fall out of the atmosphere within rain a few hours or days after an eruption. But the smallest particles of dust get into the stratosphere and are able to travel vast distances, often worldwide. These tiny particles are so light that they can stay in the stratosphere for months, blocking sunlight and causing cooling over large areas of the Earth.

Sulfur from Volcanoes

Often, erupting volcanoes emit sulfur dioxide into the atmosphere. Sulfur dioxide is much more effective than ash particles at cooling the climate. The sulfur dioxide moves into the stratosphere and combines with water to form sulfuric acid aerosols. The sulfuric acid makes a haze of tiny droplets in the stratosphere that reflects incoming solar radiation, causing cooling of the Earth’s surface. The aerosols can stay in the stratosphere for up to three years, moved around by winds and causing significant cooling worldwide. Eventually, the droplets grow large enough to fall to Earth.

Greenhouse Gases Emitted by Volcanoes

Volcanoes also release large amounts of greenhouse gases such as water vapor and carbon dioxide. The amounts put into the atmosphere from a large eruption doesn’t change the global amounts of these gases very much. However, there have been times during Earth history when intense volcanism has significantly increased the amount of carbon dioxide in the atmosphere and caused global warming.


Q.5      Write notes on the following:                      

            1.         Elements of Environment

Environment is constituted by the interacting systems of physical, biological and cultural elements inter-related in various ways, individually as well as collectively. These elements may be explained as under:

1. Physical elements: Physical elements are as space, landforms, water bodies, climate soils, rocks and minerals. They determine the variable character of the human habitat, its opportunities as well as limitations.

2. Biological elements: Biological elements such as plants, animals, microorganisms and human beings constitute the biosphere.

3. Cultural elements: Cultural elements such as economic, social and political elements are essentially manmade features, which make cultural milieu.


            2.         Significance of food chain and food web

Food chains are important because they show the intricate relationships in ecosystems. They can reveal how each organism depends on someone else for survival. Food chains also display what happens when a problem occurs and a producer or consumer is lost. Entire communities can collapse. Food chains can help scientists learn more about ecosystems and how to help them stay balanced.

Food chains are important because they reveal the complex connections that exist throughout ecosystems. Each creature in a food chain is regarded to occupy a distinct niche in an ecosystem. Food chains show how one organism relies on the survival of others.

  • The environment is balanced by the food chain.
  • Food webs show plants are the foundation.
  • The flow of energy and nutrients is explained by food webs.
  • The trophic level of organisms is determined by the food chain.

The food web and food chain processes are interesting to study. We frequently just sit down and eat without thinking about where our food comes from or the journey it takes to get to our tables. We hope the information provided was helpful. 

            3.         Soil profile

A soil profile is a vertical section of soil like the diagram above.  It allows you to examine the structure of soil.  A soil profile is divided into layers called horizons. The main soil horizons are A, B, C and D.

Most important for plant growth, the A and B horizons are the top two layers of the soil.  The A horizon is where there is most soil life and is sometimes called topsoil.  Depending on the soil, the A horizon can be further divided into A1, A2 or Ao (organic).  The B horizon is where clays and materials washed down from the A horizon accumulate.  This is sometimes called subsoil.

The C Horizon consists of weathering rock.

The D horizon is bedrock.  This is rock which has weathered to produce the soil you see above it (unless the soil has been deposited from elsewhere eg floodplains contain soil that has been carried downstream in water and then deposited as the flood recedes).


            4.         Ecology energies

There are several different factors that control the primary productivity of energy and biomass flow. Energy flow is the amount of energy that moves through a food chain. The energy input, or energy that enters the ecosystem, is measured in Joules or calories. Accordingly, the energy flow is also called calorific flow. In the study of energy flow, ecologists try to quantify the importance of different species and feeding relationships.

The largest source of energy for an ecosystem is the sun. Energy that is not used in an ecosystem is eventually lost as heat. Energy and nutrients are passed around through the food chain, when one organism eats another organism. Any energy remaining in a dead organism is consumed by decomposers. Nutrients can be cycled through an ecosystem but energy is simply lost over time.

An example of energy flow in an ecosystem would begin with the autotrophs that take energy from the sun. Herbivores then feed on the autotrophs and change the energy from the plant into energy that they can use. Carnivores subsequently feed on the herbivores and, finally, other carnivores prey on the carnivores.

In each case, energy is passed on from one trophic level to the next trophic level and each time some energy is lost as heat into the environment. This is due to the fact that each organism must use some energy that they received from other organisms in order to survive. The top consumer of a food chain will be the organism that receives the least amount of energy.



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