Aiou Solved Assignments 2 code 1421 Autumn & Spring 2021

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Aiou Solved Assignments code 1421 Autumn & Spring 2021

AIOU Solved Assignments 1 & 2 Code 1421 Autumn & Spring 2021. Solved Assignments code 1421 Introduction to Environment 2021. Allama iqbal open university old papers.

Course: Introduction to Environment (1421)
Semester: Autumn & Spring 2021
Level: BA (General)

Q. 1 Differentiate between the following terms. (20)

i) Parasitism and Predation


PARASITISM (+/-) is a close association between two living organism of different species which is

beneficial to one (the parasite) and harmful to other (the host).

The parasite obtains food and shelter from the host. Parasitism mode of life ensures food lodging and


PREDATION (+/-) is a a relationship between a Predator and a Prey in which the predator is a free

living organism which catches and kills another species for food. They do not get shelter from prey.

Predators keep prey population under control and maintains ecological balance. They also acts as

‘conduits’ for energy transfer across trophic level.


ii) Habitat and Habit


Habit and habitat are two words that are close in spelling and pronunciation and are sometimes

confused. Though they have similar roots, these words have very different meanings. We will examine

the definitions of the words habit and habitat, where these two words came from and some examples

of their use in sentences.

A habit is a customary behavior that one engages in, an acquired practice that amounts to a tendency to

do something in a certain fashion, or to engage in a certain and usual behavior when a triggering event

happens. People rarely speak about good habits, such as taking the keys out the car ignition when

departing the vehicle or brushing one’s teeth after every meal. Many books have been written

concerning bad habits and how to break them. It is difficult to kick a bad habit, no matter how

undesirable the behavior is for the individual. Breaking bad habits such as smoking seem impossible,

but with conscious willpower, repetition and reward, it can be done. The word habit is also used to

describe the outfit that one wears when riding a horse, or a riding habit, as well as the clothes that

Roman Catholic nuns wear. The word habit is derived from the Latin habere meaning to have or to



iii) Infiltration and Percolation


What is Infiltration?

Infiltration refers to the process in which the soil surface absorbs water during a rainfall. In simple

words, water enters the soil from the ground surface through infiltration. Hence, this process can be

used to measure the speed of water entering the soil in case of rain or when water is supplied to the

ground through human-made means. Basically, infiltration measurement tells the amount of water

absorbed per hour. This amount is expressed in inches or in millimetres. Moreover, infiltrometer is the

instrument we use to measure infiltration. Infiltration is important because it replenishes the soil

moisture deficiency.

Since infiltration refers to the downward flow of water through the surface of the ground; it is an

important measurement in different types of studies of geographical subjects. These involve losses due

to stream-flow, measurements of surface-area and the estimated rates of evaporation, etc.

What is Percolation?

Percolation is a process that employs in daily life for the purpose of filtering fluids within different

types of porous materials. It also occurs when infiltered water flows downward through the soil

particles and porous or fractured rocks from the unsaturated zone to saturated zone in the soil.

Percolation is an important process of extractions and filtration of fluids that can be applied in

different physical, biological, and chemical processes.

In recent times, the process of percolation has been employed to bring about revolutionary changes in

different types of technologies which are employed in a different range of topics ranging from

geography to material sciences. The most important thing about the percolation in soil is the

percolation helps to replenish aquifers underground.

Infiltration and percolation explain the movement of water through soil surface and through a porous

material respectively. In the aspect of rainwater absorption onto soil, infiltration occurs at the soil

surface while percolation occurs below the infiltration area that is in between unsaturated zone and

saturated zone. Hence, this is the difference between infiltration and percolation.

Summary – Infiltration vs Percolation

In brief, percolation is a process that involves in processing of liquids. On the other hand, infiltration is

a process that refers to the motion of fluids through the soil surface. Therefore, they are somewhat

similar processes. However, percolation occurs via tiny holes, especially through porous materials. In

soil, infiltration takes place in the root zone and soil surface while percolation takes place in between

transition zone and saturated zone. Furthermore, infiltration replenishes the soil moisture deficiency

while percolation replenishes the underground aquifers. Hence, this is the difference between

infiltration and percolation.


iv) Genetic and Species Diversity


Genetic diversity refers to the diversity of genes within a species. Therefore, it represents a variety of

genes within a species. The basic unit of life on earth is the gene. Gene is responsible for all of the

characteristics, both the similarities and the differences between organisms. The individuals of each

species comprise their own specific genetic composition. Each population of the same species also

contain different genetic compositions. Therefore, in order to conserve the genetic diversity, each

different population of the species should be conserved. If a single species is lost from an ecosystem,

substantial genetic resources also lost from the ecosystem. For example in Australia, the Tasmanian

tiger, which is one of the species of dasyurid has lost forever.

Species diversity refers to the vast numbers of different species in a particular area. Based on the

similarities, species can be grouped into families. Some of the species or the families are endemic to a

particular area. 99% of the animal species are invertebrate species. This includes insects, crabs, worms,

snails, seastars, and corals. Insects serve as pollinators, scavengers, and recyclers of nutrients in



v) Mineral and Mineraloid.


A mineral is a naturally occurring chemical compound, usually of crystalline form and abiogenic in

origin (not produced by life processes). A mineral has one specific chemical composition, whereas a

rock can be an aggregate of different minerals or mineraloids. The study of minerals is called

mineralogy. (How to Identify Common Minerals?)

A mineraloid is a mineral-like substance that does not demonstrate crystallinity. Mineraloids possess

chemical compositions that vary beyond the generally accepted ranges for specific minerals. For

example, obsidian is an amorphous glass and not a crystal. Jet is derived from decaying wood under

extreme pressure. Opal is another mineraloid because of its non-crystalline nature. Pearl, considered by

some to be a mineral because of the presence of calcium carbonate crystals within its structure, would

be better considered a mineraloid because the crystals are bonded by an organic material, and there is

no definite proportion of the components.

Aiou Solved Assignments 2 code 1421 Autumn & Spring 2021


Q. 2 What is a soil profile? Describe the characteristics of each horizon in the soil profile with a

suitable diagram.


The soil profile is an important tool in nutrient management. By examining a soil profile, we can gain

valuable insight into soil fertility. As the soil weathers and/or organic matter decomposes, the profile

of the soil changes. For instance, a highly weathered, infertile soil usually contains a light-colored

layer in the subsurface soil from which nutrients have leached away. On the other hand, a highly fertile

soil often has a deep surface layer that contains high amounts of organic matter. With clues provided

by soil profile, we can begin to predict how a soil will perform under certain nutrient management


In the previous section, we looked at how soil is actually an integration of water, air, minerals and

organic matter. Now we will view the soil as a vital part of the earth’s physical landscape.

The world’s soils are like blankets that cover most of the earth’s land surfaces. We could not survive

without it since most crops would not be able to grow in the dense rock that lies underneath. There is

no uniform depth to our earth’s soils. While it can be absent in places of exposed bedrock, soil may

extend up to tens of meters into the earth’s surface. Although this may not seem insignificant when

compared to the depth to the core of the earth, the soil profile can be very intricate and diverse. In fact,

the soil profile is made up of distinct layers, known as horizons. The five most common horizons are

collectively known as the master horizons. Figure 5 below depicts a road cut in Maui which shows the

multitude of layers that can exist in soil. Though the soil profiles in Figure 6 belong to two very

different soils, both contain distinct surface and subsurface soil layers.

Scientists have developed methods to describe the various components and characteristics of the soil

profile. By using common terminology, soil profile descriptions are valuable for deciding how the soil

might be used and/or predicting how the soil might react to its intended use. Technical descriptions of

the soil are not only useful for farmers, but for scientists, ecologists, soil engineers, hydrologists and

land use planners.

Components of the Soil Profile

A soil horizon makes up a distinct layer of soil. The horizon runs roughly parallel to the soil surface

and has different properties and characteristics than the adjacent layers above and below. The soil

profile is a vertical section of the soil that depicts all of its horizons. The soil profile extends from the

soil surface to the parent rock material. The regolith includes all of the weathered material within the

profile. The regolith has two components: the solum and the saprolite. The solum includes the upper

horizons with the most weathered portion of the profile. The saprolite is the least weathered portion

that lies directly above the solid, consolidated bedrock but beneath the regolith.

Master Horizons

There are 5 master horizons in the soil profile. Not all soil profiles contain all 5 horizons; and so, soil

profiles differ from one location to another. The 5 master horizons are represented by the letters: O, A,

E, B, and C.

O: The O horizon is a surface horizon that is comprised of organic material at various stages of

decomposition. It is most prominent in forested areas where there is the accumulation of debris fallen

from trees.

A: The A horizon is a surface horizon that largely consists of minerals (sand, silt, and clay) and with

appreciable amounts of organic matter. This horizon is predominantly the surface layer of many soils

in grasslands and agricultural lands.

E: The E horizon is a subsurface horizon that has been heavily leached. Leaching is the process in

which soluble nutrients are lost from the soil due to precipitation or irrigation. The horizon is typically

light in color. It is generally found beneath the O horizon.

B: The B horizon is a subsurface horizon that has accumulated from the layer(s) above. It is a site of

deposition of certain minerals that have leached from the layer(s) above.

C: The C horizon is a subsurface horizon. It is the least weathered horizon. Also known as the

saprolite, it is unconsolidated, loose parent material. The master horizons may be followed by a

subscript to make further distinctions between differences within one master horizon.

Aiou Solved Assignments code 1421 Autumn & Spring 2021


Q. 3 Describe the water cycle with a suitable diagram. Why is cycling of water important?


Water cycle, also called hydrologic cycle, cycle that involves the continuous circulation of water in the

Earth-atmosphere system. Of the many processes involved in the water cycle, the most important are

evaporation, transpiration, condensation, precipitation, and runoff. Although the total amount of water

within the cycle remains essentially constant, its distribution among the various processes is

continually changing.

A brief treatment of the water cycle follows. For full treatment, see hydrosphere: The water cycle.

Evaporation, one of the major processes in the cycle, is the transfer of water from the surface of the

Earth to the atmosphere. By evaporation, water in the liquid state is transferred to the gaseous, or

vapour, state. This transfer occurs when some molecules in a water mass have attained sufficient

kinetic energy to eject themselves from the water surface. The main factors affecting evaporation are

temperature, humidity, wind speed, and solar radiation. The direct measurement of evaporation, though

desirable, is difficult and possible only at point locations. The principal source of water vapour is the

oceans, but evaporation also occurs in soils, snow, and ice. Evaporation from snow and ice, the direct

conversion from solid to vapour, is known as sublimation. Transpiration is the evaporation of water

through minute pores, or stomata, in the leaves of plants. For practical purposes, transpiration and the

evaporation from all water, soils, snow, ice, vegetation, and other surfaces are lumped together and

called evapotranspiration, or total evaporation.

Enjoy learning about the water cycle for kids. Understand how the water cycle works with our facts

that help explain the different processes in a way that’s easy to follow. Follow the diagram and learn

about evaporation, condensation, precipitation and more.



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Heat from the Sun causes water on Earth (in oceans, lakes etc) to evaporate (turn from liquid into gas)

and rise into the sky. This water vapor collects in the sky in the form of clouds.


As water vapor in the clouds cools down it becomes water again, this process is called condensation.


Water falls from the sky in the form of rain, snow, hail, or sleet, this process is called precipitation.


Oceans and lakes collect water that has fallen. Water evaporates into the sky again and the cycle




In a process similar to sweating, plants lose water which is absorbed into the atmosphere much like

evaporation. The combination of evaporation and transpiration is known as evapotranspiration.


It is possible for a solid to transform into a gas directly (without becoming a liquid). The most common

example of sublimation is dry ice (solid carbon dioxide) which sublimes at normal air temperature.

Under certain conditions snow and ice can also sublime.

Aiou Solved Assignments 2 Autumn & Spring 2021 code 1421


Q. 4 Microorganisms play a vital role in keeping the soil nutrients intact. Explain considering

nitrogen cycle as an example


The term nitrogen cycle refers to the process through which nitrogen transforms into its various states

or forms. The process can be biological or physical and has four parts: fixation, ammonification,

nitrification and denitrification.

Understanding the Nitrogen Cycle

Because so much of the Earth’s atmosphere consists of nitrogen (greater than 3?4), it is extremely

important for scientists to understand this process in order to determine and comprehend its effects on

various ecosystems.

Some examples of the nitrogen cycle include the following:

• A plant takes nitrogen from the soil by absorbing it through its roots. The nitrogen comes in the

form of nitrogen ions. When the nitrogen is absorbed by the plant, it is reduced to nitrite ions.

Next, it becomes ammonium ions which can be incorporated into amino or nucleic acids and

into chlorophyll.

• When a plant dies or an animal dies or when a plant or an animal expels waste, organic

nitrogen is then released. Bacteria is able to convert this organic nitrogen into ammonium. It

does this through a process called mineralization.

• Nitrogen gets into the oceans as a result of runoff from ground water or when it rains. Nitrogen

can also get into the ocean through precipitation (rain). Nitrogen in the water undergoes

fixation, which is generally facilitated by a bacteria called cyanobacteria. After fixation, the

nitrogen is in a biologically available form that phytoplankton in the ocean can use.

• The plankton excrete both urea and ammonia into the water. Phytoplankton and waste products

can sink downward, introducing ammonia at a depth below the euophotic zone. The ammonia

from the waste products is then removed from the euphotic zone and bacteria that live below

the euphotic zone can convert the ammonia into nitrate. This conversion can only occur below

the euphotic zone where there is no light since the bacteria that perform the conversion are

inhibited by light. The process of conversion is called ammonification or mineralization.

• Once the ammonia is converted, nitrification occurs and the ammonia becomes nitrite and

nitrate. Vertical mixing and upwelling can carry the nitrate upward and it can then be used by

photoplankton to continue the cycle.

Facilitating the Cycle

The nitrogen cycle is affected by factors that work to facilitate the conversion of nitrogen into various

states and back through the atmosphere.

These factors include:

• The use of agricultural fertilizer.

• The growing of legumes by agriculturalists. Legumes are able to convert nitrogen to nitrates

and nitrites.

• The use of nitrates by bacteria in soil.

• Microbes in soil and water that change ammonia into nitrites.

• Bacteria called Nitrosomonas that convert ammonia to nitrites.

• Bacteria called Nitrobacter change nitrites to nitrates.


• Termites and shipworms pair with bacteria to change nitrogen’s form.

• Cyanobacteria that live in semi-aquatic environments can participate in the nitrogen cycle.

• Industrial fixation can be used to convert nitrogen to ammonia at temperatures of 600 degrees

and beyond with the use of catalysts.

• Nitrogen can be fixed atmospherically via lightning.

Now you have lots of different examples of how the nitrogen cycle works and of some of the things

that can impact the nitrogen cycle. These examples should help you better understand this important

and life-sustain.

Aiou Solved Assignments code 1421 Autumn & Spring 2021


Q. 5 Define biodiversity. What are the ecological, economical and social benefits biodiversity?


Biodiversity is the foundation of ecosystem services to which human well-being is intimately linked.

No feature of Earth is more complex, dynamic, and varied than the layer of living organisms that

occupy its surfaces and its seas, and no feature is experiencing more dramatic change at the hands of

humans than this extraordinary, singularly unique feature of Earth. This layer of living organisms—the

biosphere—through the collective metabolic activities of its innumerable plants, animals, and microbes

physically and chemically unites the atmosphere, geosphere, and hydrosphere into one environmental

system within which millions of species, including humans, have thrived. Breathable air, potable

water, fertile soils, productive lands, bountiful seas, the equitable climate of Earth’s recent history, and

other ecosystem services (see Box 1.1 and Key Question 2) are manifestations of the workings of life.

It follows that large-scale human influences over this biota have tremendous impacts on human well-

being. It also follows that the nature of these impacts, good or bad, is within the power of humans to

influence (CF2).

Biodiversity is defined as “the variability among living organisms from all sources including, inter alia,

terrestrial, marine and other aquatic ecosystems and the ecological complexes of which they are part;

this includes diversity within species, between species and of ecosystems.” The importance of this

definition is that it draws attention to the many dimensions of biodiversity. It explicitly recognizes that

every biota can be characterized by its taxonomic, ecological, and genetic diversity and that the way

these dimensions of diversity vary over space and time is a key feature of biodiversity. Thus only a

multidimensional assessment of biodiversity can provide insights into the relationship between

changes in biodiversity and changes in ecosystem functioning and ecosystem services (CF2).


Ecological, economical and social benefits biodiversity:

• Maintaining biodiversity is essential for organic waste disposal, soil formation, biological

nitrogen fixation, crop and livestock genetics, biological pest control, plant pollination, and

pharmaceuticals. Plants and microbes help to degrade chemical pollutants and organic wastes

and cycle nutrients through the ecosystem. For example:

o Pollinators, including bees and butterflies, provide significant environmental and

economic benefits to agricultural and natural ecosystems, including adding diversity

and productivity to food crops. As many as one-third of the world’s food production

relies directly or indirectly on insect pollination. About 130 of the crops gown in the

United States are insect pollinated. Habitat fragmentation and loss adversely affects

pollinator food sources, nesting sites, and mating sites, causing precipitous declines in

the populations of wild pollinators.

o There are 6 million tons of food products harvested annually from terrestrial wild biota

in the United States including large and small animals, maple syrup, nuts, blueberries

and algae. The 6 billion tons of food are valued at $57 million and add $3 billion to the

country’s economy (1995 calculations).

o Approximately 75% (by weight) of the 100,000 chemicals released into the

environment can be degraded by biological organisms and are potential targets of both

bioremediation and biotreatment. The savings gained by using bioremediation instead

of the other available techniques; physical, chemical and thermal; to remediate chemical

pollution worldwide give an annual benefit of $135 billion (1997 calculation).

Maintaining biodiversity in soils and water is imperative to the continued and improved

effectiveness of bioremediation and biotreatment.

• Biodiversity is essential for the sustainable functioning of the agricultural, forest, and natural

ecosystems on which humans depend, but human activities, especially the development of

natural lands, are causing a species extinction rate of 1,000 to 10,000 times the natural rate.

• The authors estimate that in the United States, biodiversity provides a total of $319 billion

dollars in annual benefits and $2,928 billion in annual benefits worldwide (1997 calculation)

Aiou Solved Assignments 2 Autumn & Spring 2021 code 1421


Q. 6 Write notes on draw suitable diagram. (16)

i) Principles of Ecosystem Sustainability


Many natural ecosystems are self-sustaining, maintaining a characteristic mosaic of vegetation types

for hundreds to thousands of years. In this article we present a new framework for defining the

conditions that sustain natural ecosystems and apply these principles to sustainability of managed

ecosystems. A sustainable ecosystem is one that, over the normal cycle of disturbance events,

maintains its characteristic diversity of major functional groups, productivity, and rates of

biogeochemical cycling. These traits are determined by a set of four ”interactive controls” (climate, soil

resource supply, major functional groups of organisms, and disturbance regime) that both govern and

respond to ecosystem processes. Ecosystems cannot be sustained unless the interactive controls

oscillate within stable bounds, This occurs when negative feedbacks constrain changes in these

controls. For example, negative feedbacks associated with food availability and predation often

constrain changes in the population size of a species. Linkages among ecosystems in a landscape can

contribute to sustainability by creating or extending the feedback network beyond a single patch.

The sustainability of managed systems can be increased by maintaining interactive controls so that

they form negative feedbacks within ecosystems and by using laws and regulations to create negative

feedbacks between ecosystems and human activities, such as between ocean ecosystems and marine

fisheries. Degraded ecosystems can be restored through practices that enhance positive feedbacks to

bring the ecosystem to a state where the interactive controls are commensurate with desired ecosystem

characteristics. The possible combinations of interactive controls that govern ecosystem traits are

limited by the environment, constraining the extent to which ecosystems can be managed sustainably

for human purposes.


ii) Soil Erosion


When things erode, they wear away due to some force acting on them. Just look at any coastline, and

you will notice how the constant pounding force from wind and waves causes erosion of the rocky

structures, leaving behind all kinds of interesting cliffs, caves and structures. Soil is not immune to

erosion, and like rocks along a coastline, soil can erode due to the effects of forces, such as water, wind

and farming practices. In this lesson, we will learn about soil erosion and the factors that cause it.

Soil is naturally created when small pieces of weathered rocks and minerals mix with organic materials

from decaying plants and animals. Soil creation is a slow process, taking many years. However, the

soil that is created is constantly subjected to natural and manmade forces that disrupt it.

Soil erosion is defined as the wearing away of topsoil. Topsoil is the top layer of soil and is the most

fertile because it contains the most organic, nutrient-rich materials. Therefore, this is the layer that

farmers want to protect for growing their crops and ranchers want to protect for growing grasses for

their cattle to graze on.

Water Erosion and Surface Water Runoff

One of the main causes of soil erosion is water erosion, which is the loss of topsoil due to water.

Raindrops fall directly on topsoil. The impact of the raindrops loosens the material bonding it together,

allowing small fragments to detach. If the rainfall continues, water gathers on the ground, causing

water flow on the land surface, known as surface water runoff. This runoff carries the detached soil

materials away and deposits them elsewhere.

There are some conditions that can accentuate surface water runoff and therefore soil erosion. For

example, if the land is sloped, there is a greater potential for soil erosion due to the simple fact that

gravity pulls the water and soil materials down the slope. Also, water will have an easier time running

across the surface, carrying topsoil with it, if the ground is already saturated due to heavy rains or the

soil lacks vegetation to keep the soil in place.

Sheet Erosion

There are different types of soil erosion caused by water. Sheet erosion is erosion that occurs fairly

evenly over an area. As raindrops loosen soil, the surface water runoff can transport topsoil in a

uniform fashion, almost like a bed sheet sliding off of a bed. This can be so subtle that it might not

even be noticed until much of the valuable, nutrient-rich topsoil has already been washed away. If a

farmer heads out to his field and sees an accumulation of soil and crop residue at one end of his field,

he should be worried about sheet erosion.

Rill Erosion

Rill erosion is erosion that results in small, short-lived and well-defined streams. When rainfall does

not soak into the soil, it can gather on the surface and run downhill, forming small channels of water

called rills. You can use this fact as a memory jogger if you remember that ‘a little rill will run

downhill.’ A rill will dry up after the rainfall, but you may still see the stream bed that was created by

the temporary stream.

Gully Erosion

Gully erosion can be thought of as advanced rill erosion. In fact, if rills are not addressed, they will

grow into larger gullies. Gully erosion can spell big problems for farmers because the affected land is

not able to be used for growing crops, and the big ditches create a hazard for the farmer driving his

farm machinery over the fields.

Aiou Solved Assignments Autumn & Spring 2021 code 1421


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