Unit I.2 - Ecosystems

8/13/2019 Unit I.2 - Ecosystems

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Components of Earths

Environment1. Atmosphere

2. Geosphere

3. Hydrosphere4. Biosphere


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GEOSPHERE

The geosphere is considered that portion ofthe Earth system that includes the Earth'sinterior, rocks and minerals, landforms and the

processes that shape the Earth's surface. It comprises of three parts starting from the

outside to the centre:

- Crust- Mantle

- Core


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The Earths Crust

There are two different types of crust:

1)Thin oceanic crust that underlies the ocean

basins. Its thickness varies between 3-5 km at

different points.

2) Thicker continental crust that covers thecontinents. Its thickness varies between 30-50

km at different points.


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The Earths Mantle

Earth's mantle extends for about 3000 km and hasdifferent temperatures at different depths.

The temperature is lowest immediately beneath the crustand increases with depth. This steady increase of

temperature with depth is known as the geothermalgradient.

The geothermal gradient is responsible for different rockbehaviours and the different rock behaviours are used todivide the mantle into two different zones:

i) Rocks in the upper mantle are cool and brittle, it is theserocks that break under stress causing earthquakes.

ii) Rocks in the lower mantle are hot and soft (but notmolten).


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The Earths Core

Earth's Core is assumed to be composed mainlyof an iron and nickel alloy.

The core is earth's source of internal heatbecause it contains radioactive materials whichrelease heat as they break down into more stablesubstances.

The core is divided into two different zones.

- The liquid outer core

- The solid inner core


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Hydrosphere

All the water in its various forms, present in all thecomponents of Earths environment togetherconstitutes the hydrosphere.

The subsystem include the oceans, frozen water inglaciers and the ice caps, and other water such asgroundwater, and the water vapour in the atmosphere.

Wherever water occurs may be considered water's"reservoir."

Oceans hold about 97.2% of the total water whileabout 2.2.% is frozen in glaciers which leaves only 0.5%in other subsystems.


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Components of Earths Hydrosphere

1. Oceans: Major part of water is present in the oceans of theEarth. About 1300 million cubic kilometers water is present inoceans.

2. Ice sheets: Substantial quantity of water is frozen in the icesheets of Earth.

3. Groundwater: About 24 million cubic kilometer water is presentunder the ground surface at depths of upto two kilometers.

4. Lakes and rivers:On the land surface, approximately 0.18 millioncubic kilometer water is present in lakes while about 0.002 millioncubic kilometer water is found in rivers.

5. Atmospheric moisture: The amount of water present as watervapor in the atmosphere is about 0.013 million cubic kilometer.

6. Biological water: In addition to above categories, about 0.001million cubic kilometer water is contained in the bodies of livingorganisms.


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Hydrological (Water) Cycle

The total amount of water on the earth and in itsatmosphere does not change but the earths water isalways in movement. Oceans, rivers, clouds and rain,all of which contain water, are in a frequent state ofchange and the motion of rain and flowing riverstransfers water in a never-ending cycle.

This circulation and conservation of earthswater asit circulates from the land to the sky and back again iscalled the hydrologicalcycleor watercycle.


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The stages of the cycle are:

Evaporation

Transport

Condensation

Precipitation

Groundwater

Run-off


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BIOSPHERE

The part of the earth and its atmosphere in

which living organisms exist or that is capable

of supporting life is referred to as biosphere.


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What is Ecosystem

An ecosystem is a community of organismsinvolved in a dynamic network of biological,chemical and physical interactions between

themselves and with the nonliving components.There are many examples of ecosystems -- apond, a forest, an estuary, a grassland.

A major regional or global biotic community, such

as a grassland or desert, characterized chiefly bythe dominant forms of plant life and theprevailing climate.


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Components of Ecosystem

1. Abiotic Components

a) Inorganic Components

b) Organic Components

c) Climatic Factors

2) Biotic Components

a) Producersb) Consumers (Herbivores, Carnivores,

Detritivores, Decomposers)


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Types of

Ecosystems

Natural

Terrestrial Aquatic

Marine Freshwater

Artificial


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Types of Terrestrial Ecosystems

Terrestrial ecosystems can be broadly

categorised into 7 types as follows:

1) Tropical Rainforests

- High precipitation (Rainfall), greater than

250cm/year.

- Very little temp. variation

- Contains more species than other biomes


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2)Savannas (Grasslands)

- Precipitation 90-150cm/year

- Open, widely spaced trees, seasonal rainfall

(Parts of Africa, South America & Australia)

3) Deserts

- Precipitation 20cm/year

- Dry, sparce vegetation; scattered grasses(Parts of Africa, Asia, Australia, North America)


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4) Temperate GrasslandsPrecipitation: 10-

60cm/year

Rich soil; tall dense grasses

Central North America; Central Asia

5) Deciduous forests

Precipitation 75-250cm/year

Warm summers, cool winters Europe; NE United States;Eastern Canada


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5) Coniferous forest:

Precipitation 20-60cm/year

Short growing season, cold winters.

Northern Asia;Northern North America

6) Tundra

25 cm/year

Open; wind swept; dry; ground always frozen

Far northern Asia; Northern North America


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Types of Marine Ecosystems

1) Benthic Marine Ecosystems

- Benthic organisms, attached or non-attached, live

on the ocean bottom.

- Substrate and Temperature are very important

characteristics in determining benthic communitydevelopment.


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2) Coral Reef Ecosystems - Large number of animals

that build cup-shaped external skeletons.

- Contain single-celled algae and carry on

photosynthesis.

- Require warm water, thus are found only near theequator.

- Most require clear, shallow water with ample sunlight

penetration.


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3) Mangrove Swamp Ecosystems

- Occupy region near shore.

- Trees tolerate high salt content.- Extensively developed roots.

- Trap sediment in shallow areas.

- Develop terrestrial ecosystems.


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4) Estuaries

Shallow, partially enclosed areas where freshwater

enters the ocean. Extensive production because areas are shallow,

warm, and nutrient-rich.


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Food Chain, Trophic level and Food

Web

A food chain shows the succession of organisms in anin an ecological continuity representing how nutrientsand energy are passed from creature to creature aseach consumes a lower level organism and is in turn

consumed by a higher level organism. Each food chain is one possible path

that energy and nutrients may take as they movethrough the ecosystem.

Trophic Level

The organisms of a food chain are classified intodifferent trophic levels on the basis of their feedingbehaviour. Thus we have plants forming the first levelthat of primary producers, followed by primary,

secondary, tertiary and quaternary consumers.


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Food Web

A food web consists of all the food chains in a

single ecosystem. Each living organism in an

ecosystem is part of multiple food chains. All

of the interconnected and overlapping foodchains in an ecosystem make up a food web.


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Grass, berries and seeds

Insects

Rats

Small Bird

Snakes

Eagle

FOOD WEB

Frogs


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Ecological Pyramid

Charles Elton developed the concept of ecologicalpyramid. It is a graphical representation, in a pyramidshaped diagram, of the number of organisms, biomassand productivity at each trophic level. Ecologicalpyramids begin with the producers at the bottom and

proceed through the different trophic levels.

Types of Ecological Pyramids

1) Pyramids of numbers2) Pyramids of Biomass

3) Pyramids of Energy


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2) Pyramid of Biomass

Biomass means total dry weight of organic

matter or caloric value present in the

ecosystem at any one time.

The pyramid of biomass means weight of

organisms at different tropic level.

The pyramid may be upright or inverted


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Ecological Succession

Ecological Succession refers to the gradual and

orderly process of changes in community structure

over time. Activities of organisms change their

surroundings and make the environment suitable forother kinds of organisms. Thus progressive

replacement of one community by another occurs

until a somewhat stable climax is established.


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Principles of Ecological Succession

1. The physical environment determines which communitiescan exist in a particular place.

2. Succession is community controlled, i.e., succession iscaused by modification of the surrounding physicalenvironment by the existing community.

3. Ecological succession is directional - and thereforepredictable.

4. Succession ends in a stabilized community and ecosystemcalled the ecological climax. It is in equilibrium with thephysical environment of that particular area and

perpetuates itself. This tendency for the ecosystemto reach a stage where it stays in equilibrium is anexample of Homeostasis developing and maintainingstability.

5. High diversity produces stability.


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Types of Ecological Succession

Primary & Secondary Succession

Autogenic & Allogenic Succession

Progressive & Regressive Succession


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Primary Succession

Begins with total lack of organisms on baremineral surfaces or water.

The first group of organisms establishing life areknown as the pioneers, primary community or

primary colonisers. In the primary succession taking place on the

exposed rock surfaces, for instance, lichensappear first, followed by the mosses. These

pioneers change the physical environment so thatthe new species of autotrophs a in the area andestablish themselves.


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Secondary Succession

Begins with disturbance or destruction of an

existing ecosystem.

This occurs much more commonly and is

generally quicker.

Nearby undamaged communities can serve as

sources of seeds and animals.


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Autogenic Succession

After the succession has begun, in most of the

cases, it is the community itself, which, as a

result of its reactions with the environment,

modifies its own environment and thuscausing its own replacement by new

communities.


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Allogenic Succession

In some cases, however, the replacement of

the existing community is caused largely by

any another external condition and not by the

existing organisms! Such a course is referredto as allogenic succession.


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Progressive Succession

Primary succession is a succession where the

community becomes complex and contains

more species and biomass over time.


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Regressive Succession

Also referred to as retrogression or

degeneration, it is the replacement of a

community of plants of higher ecological

order with a community of lower ecologicalorder.


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BIODIVERSITY


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Biodiversity

Biodiversity refers to the numbers, variety, andvariability of living organisms and ecosystems. Itincludes all the terrestrial and aquatic organisms.It covers diversity within species, betweenspecies, as well as variation among ecosystems.

Levels in Biodiversity Organization

- Genetic Diversity

- Species Diversity

- Ecosystem Diversity

d h d f


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Factors determining the degree of

biodiversity

Habitat Stress

Geographical isolation

Dominance by one species

Availability of ecological niches

Edge effect

Geological history

i i di i


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Factors Impacting Biodiversity

(Threats)

Climate change

Pollution of soil, water & atmosphere

Introduction of Aggressive Non-native Species

Industrial agriculture & forestry

Habitat loss

GMOs

Poaching

Explosion in Human Population


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Value/Importance of Biodiversity

1) Food Security

2) Nutrient Cycling

3) Fuel & Wood

4) Maintenance of Water Resources

5) Soil Formation & Fertility

6) Gene Pool

7) Medicinal Resources

E d d S i d IUCN


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Endangered Species and IUCN

Categorisation

India has about 3% of the worlds threatened species

Data adequate evaluated species:

1) Extinct/Extinct in the wild

2) Threatened

- Critically Endangered eg. Himalayan Quail

- Endangered eg. Bengal Mongoose, Great IndianBustard, Red Sandal wood

- Vulnerable eg. Indian Giant Squirrel, NilgiriLangur, Indian Rosewood

3) Lower Risk

(all examples mentioned here are endemic to India.)


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Conservation of Biodiversity

Conservation means the use of all actions

which are necessary to bring any endangered

of threatened species to the point at which it

is no longer threatened.

It includes both curative and preventive

measures.

The efforts could focus on specific species oron habitat and ecosystems.


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Conservation Measures

1) In Situ Conservation Measures

Includes all those conservation measures that are taken inthe natural habitat.

a) Wildlife sanctuaries and national parks

b) Biosphere Reserves

Biosphere reserves are biota, habitats, total ecosystemincluding the landscape, the local people using the naturalresources are all treated as one whole for any decision-making regarding conservation action.

c) World Heritage Sites

2) Ex Situ Conservation

Conservation measures taken outside onesnatural habitat

E.g. Zoos, botanical gardens, aquaria and seed banks.

Documents

Unit I.2 - Ecosystems