HYS: Environment and Ecology Part 1.2

Ecological Succession

Observed process of change in the species structure of Ecological Community over time

Simple Definition: Replacement of simpler species by more adapted and complex species, till

climax is reached

Primary: Start from an area where life never existed i.e. uninfluenced by pre-existing

communities

Secondary: Life existed earlier. Follows disruption of a pre-existing community

Serule: ES of micro-organism like fungi and bacteria

Pioneer and climax

The whole process of primary autotrophic succession – completed through a number of

sequential steps

Sequence

1. Nudation: Bare area without any life

2. Invasion (Pioneer): Successful establishment of a species in a bare area. a) Migration, b)

Ecesis means establishment (individual come and live), c) Aggregation: Reproduction

3. Competition and Coaction: Inter and intra-specific competition.

4. Reaction: Most important stage, environment modified under influence of living organism

5. Stabilization (Climax): Final terminal or climax community becomes more or less stabilized,

equilibrium

Retrogressive Succession: Forest to shrubs to grass, if there is any disruption by continuous

biotic

Influence.

Human actions

Climate, Forest fires, Volcano eruption

Climax: Harmony with environment, both influence each other, adapt continuously, wide

diversity, well drained spatial structure, complex food chain

Polyclimax theory

Population interaction

For any species, survival in isolation is not possible.

So, interaction are basic necessity

1. Mutualism: + +

2. Competition: - -

3. Amensalism: - 0

4. Predation: + -

5. Parasitism: + -

6. Commensalism: + 0

Predation

Release of fixed energy, herbivores are not too different, prey population under control,

prickly pear cactus in Oz and moth story, species diversity, Pisaster starfish in pacific

intertidal area

Predator too efficient- extinct prey and then itself! So, predator are prudent

Prey: Camouflage, Monarch butterfly distasteful, against phytophagus insects, plants like

acacia, cactus have spines, Calotropis produces cardiac glycosides,

Extract like nicotine, caffeine, opium, quinine, strychnine are all defense mechanism

Competition

Darwin: Survival of the fittest, closely related species competing for the same resources.

Exception: Unrelated- Flamingos and fish compete for zooplankton. Feeding efficiency

might also interfere, even if resources are sufficient

Fitness of one species (r) is significantly lower in presence of other species.

Abingdon tortoise extinct, goats, Galapagos island

Competitive release: Geographical area restricted increases if competition removed.

Scotland, Balanus dominates and remove smaller barnacle Chathamus

Gause’s ‘Competitive Exclusion Principal’: Resource partitioning, Warblers on same tree co-

exist with different foraging activity

Parasitism

Free residence, transport and food, so huge variety from plants to higher vertebrates.

Co-evolution of host and parasite : Loss of unnecessary sense organs, presence of

adhesive organs or suckers to cling on to host, loss of digestive system, high

reproductive capacity

Complex life cycle: Human liver fluke (trematode) depends on snail and fish, 2

intermediate host. Ecto-Parasite: Lice, ticks, marine fish by copepods, Cuscuta on

hedge plants. Endo-Parasite: inside in liver, kidney, RBCs, lungs. Brood-Parasite :

Cuckoo and crow

Parasites harm the host, reduce survival, growth, reproduction, population density of

the host, but usually do not kill them

Female anopheles mosquito is a vector not a parasite

Commensalism

One benefits other is unaffected

An orchid or other epiphytes growing on other trees for support

Cattle egret and grazing cattle

Sea anemone with stinging tentacles and clownfish that live among them

Mutualism

Both benefits.

Mycorrhizae: Fungi helps roots of higher plants absorb essential nutrients while plant in

turn provides energy-yielding carbohydrates

Pollination: Pollen and nectar for pollinator and nutritious fruits for seed dispersal. Here

also Co-Evolution. Ex: Figonly by partner wasp- Oviposition (laying eggs) plus feeding larvae

from seeds. Wasp pollinates figinflorescence in turn

Mediterranean orchid Ophyrus, sexual deceit, one petalresembles female bee in shape,

size, colour, marking, pseudocopulation with 2 or more leads to pollination. Here, co-

evolution is a must.

HYS: Environment and Ecology Part 1.3

Ecosystem

ECOSYSTEM (Term coined by Tansley)

Smallest structural and functional unit of nature,

Consisting of both the biotic community and the abiotic environment, which have close

interactions

The interaction is conducted by

energy flow (solar energy)

In the system and cycling of materials (nutrient cycles).

Entire biosphere is considered as a global ecosystem

Composite of all local ecosystems on Earth.

Structure of the ecosystem includes

input (productivity),

transfer of energy (food chain/web, nutrient cycling)

Output (degradation and energy loss).

Characteristics: Boundaries are indistinct and overlapping. May be temporary or

permanent. May be small (drop of water) or large (whole earth)

Types of ecosystem: On the basis of origin

NATURAL -

Terrestrial (Forest, grassland and desert) and Aquatic (pond, lake, wetland, river and

estuary). In aquatic ecosystem, more biodiversity is found in LOTIC ecosystem (running

fresh water ecosystem like river) than in LENTIC ecosystem (Stagant fresh water like

lake, pond, swamp)

ARTIFICIAL -

Crop fields and an aquarium are considered as man-made ecosystems.

On the basis of size:

Mega ecosystem: Entire biosphere

Macro ecosystem: Major biomes like tropical rain forest etc.

Micro ecosystem: Pond, aquarium etc.

Nano ecosystem: Drop of water

Components of Ecosystem:

Biotic components: include any living component from smallest microbe, fungi to largest

animals and plants

Abiotic Factors: include inorganic substances (carbon, nitrogen, carbon dioxide, water,

etc.) involved in natural cycles, air, water and other physical factors, organic compounds

(proteins, carbohydrates, humus). The important ones are:

Temperature, Light, Water and Soil

Temperature

Most important environmental factor, spatial distribution of species decreases on either

side of equator towards the poles and as we go above or below MSL (Mean Sea Level)

because of decrease in temperature, it can limit biodiversity by causing Desiccation,

chilling and freezing injury. If temperature increases relative humidity(RH) also increases

RH is measured by psychrometer while Wind speed is measured by anemometer

Temperature based zonation of Water bodies/Thermal stratification in lakes

Epilimnion: Vertical gradient of gradually decreasing temperature from surface

Metalimnion: aka Thermocline Short zone with rapidly declining temperature

Hypolimnion: Deep zone of cold temperature where no further gradient

Water

2nd most important abiotic factor, life started in water about 3.5 billion years ago.

Precipitation is the major source of soil water.

Forms of precipitation= Drizzle, Rain, Snow, Sleet, Hails

On basis of water need, organisms can be classified as:

Hydrocoles: Aquatic animals needing large quantity of water like fish.

Mesocoles: Animals needing moderate amounts of water including most

terrestrialanimals

Xerocoles: Terrestrial animal who can tolerate extreme dry conditions and can

survivemany days without water like camel and kangaroo rat etc.

Euryhaline: Those organisms which can tolerate wide ranges of salinities.

Stenohaline: Those organism which can survive only a limited range of salinity.

Halophytes: Salinity loving plants.

The shallow shore region of marine area : neritic zone

Part of a water body which have been cut off from river : ox bow lake

Estuaries : region where river enters ocean

Soil

Soil: aka Edaphic factors.

In general, soil has this composition = Minerals 45% + water 25% +air and other gases 25%

+organic matter 5%+ innumerable organisms. But composition varies widely depending

upon the type of soil

Soil formation: Pedogenesis, slow process

Study of soil pedology

Loamy soil (40% sand + 40% silt + 20% clay) is the best soil for growth of plants, it has high

water holding capacity, high aeration and root penetration

Soil organic matter: Freshly fallen plant or dead animals = detritus or litter

Partially decomposed = duff Fully decomposed = humus

(Litter———>duff—————>humus)

Decomposition (formation of humus): Four steps:

Fragmentation- breaking into small particles by detrivores (earthworm)

Leaching- water soluble nutrients move into soil horizon

Catabolism- bacterial and fungal degradation by enzymes

Humification and mineralization- leads to the formation of humus then minerals, and

occurs during soil formation.

Mor- raw humus form in acidic soil

Mull- real humus i.e. fully decomposed litter

Types of soil:

1. Residual soil- weathering and pedogenesis occur at same place.

2. Transported soil- weathering and pedogenesis occur at different place(CAGE: GWSW is

a good mnemonic i.e C for colluvial , A for alluvial and G for gravity, W for Water)

3. Colluvial soil- brought by gravity

4. Alluvial soil – by water

5. Glacial soil – by snow

6. Eolian soil – by wind

Best pH of soil for growth of plants: 5.5-6.5

Excess water logging produces salinity

Nutrient availability depends on pH of soil

Alkaline soil can be corrected by adding gypsum (CaSO4)

The main types of soil in India are as follows:

Red soils, Laterite and lateritic soil, Black soil, Alluvial soils, Forest &hill soils, Peaty and

marshy soils, Desert soils, Saline & Alkaline soils

HYS: Environment and Ecology Part 1.4

1) Red soils: Light textured with porous and friable structure and there is absence of lime, Kankar

and free carbonates. Neutral to acidic reaction and are deficient in nitrogen humus, phosphoric

acid and lime. Ex: Periyar and Salem district of Tamil Nadu, MP, Andhra, Eastern Rajasthan etc.

2) Laterites and Lateritic soils: Red to reddish yellow in colour and low in N, P, K, lime and

magnesia. These soils are formed in-situ under conditions of high rainfall with alternation dry and

wet periods.

Rainfall leading leaching producing porosity. High distribution range from Eastern Ghats, entire

south India, Satpura, Vindhyan plateau, Maikal and Mahadeo ranges in Madhya Pradesh.

3) Black soils (Indian Regur soil): Originated from vulcanism, know as “Black cotton soils” as they

are of dark brown colour and suitability for growing cotton. An accumulation of lime is seen.

These soils are deficient in nitrogen, phosphoric acid and organic matter but rich in calcium,

potash and magnesium. Found in Deccan plateau (Mahrashtra) and MP plateau, Saurashtra and

Malwa

4) Alluvial soils: These soils occur along rivers and represent the soil materials that have been

deposited by the rivers duing flood. Despite sometimes being deficit in N, P and Humus, they are

highly productive soils. Ex: Great northern Gangetic plains, along valleys of Narmada, Mahandi,

Tapti, Cauvery and Godawari.

5) Forest and hill soils: These soils usually occur at high or low elevations if rainfall is sufficient to

support trees. These soils are very shallow, steep, stony, and infertile for the production of field

crops. But produce timber and fuel. Ex: Himalayan regions valley basins, less steeply inclined

slopes, depression

6) Desert soils: Mostly sandy soils that occur in the low rainfall track. They are well supplied with

soluble salts but are low in nitrogen and organic matter and have a high pH value. These are quite

productive. These are often subjected to wind erosion. Found in Western Rajasthan and adjoining

regions of Gujarat,

7) Saline & Alkaline soils: These soils occur in areas having a little more rainfall than the areas of

desert soils. They show white incrustation of salts of calcium & Magnesium and sodium on the

surface. These are poor in drainage and are infertile.

8) Peaty and Marshy soils: These types of soils are found in Kerala (Kari soil), coastal track of

Orissa, Sunderban area of W.B. When the vegetation growing in such wet places dies, it

decomposes very slowly dues to excessive wetness of soils and after several hundreds of year a

layer of partly decayed organic matter accumulates on the surface, giving rise to such peaty and

marshy soils. These are black colored, heavy and highly acidic soils. When properly drained and

fertilized, these soils produce good crops of rice.

Soil Erosion:

Removal, transport and deposition of soil from one location on earth crust to another.

Occurs naturally

But anthropogenic activities have increased it by 30-40 times. May Lead to

decrease in productivity, desertification, ecological collapse

eutrophication

Causes:

Water: Sheet erosion, Gully erosion, Rill Erosion

Wind: Saltation, Suspension, Surface Creep

Special Phenomena: Solifluction- Soil flow-age, seen in Tundra in summers and wind erosion

are now the two primary causes of land degradation; combined, they are responsible for

about 84% of the global extent of degraded land, because of permafrost, melt water cannot

percolate below, giving soil particles a saturated, heavy and saggy appearance.

Slip erosion: aka Landslides: Water, gravity in combination moves large amount of matter

down the slope.

Steam Bank Erosion: Rivers during floods splash their water against the banks and cuts

through them.

Methods of soil Conservation:

A. Agronomic Methods:

1. Contour Farming: Alternate furrows with ridges.

2. Mulching: Stalk, base, stem etc of plant is left on the field to form a protective layer called

mulch. Ex: Sugarcane, Maize, Cotton, Potato

3. Crop Rotation: Prevention of depletion of minerals by growing alternating crops especially

leguminous plants like pulses etc.

4. Strip Cropping: Planting crops in strips/rows to prevent flow of water.

B. Agrostological Methods: Grasses are used as erosion preventing plants. Ex: Lay farming where

grasses are used in rotation with field crops

Light: Needed for photosynthesis.

Based on penetration of light, stratification in lake water body is characterized into three

categories-

Littoral zone –found at the bank near shallow water

Limnetic zone- Neither too deep nor too shallow, well-lit, open surface waters in a lake,

away from the shore. The vegetation of the littoral zone surrounds it. This is the main

photosynthetic body and produces oxygen and food that support the lake's consumers.

Profundal/ Abyssal zone - very deep zone where there is no penetration of light.

Light intensity is measured by luxmeter or photometer.

Electromagnetic spectrum : This in increasing order of wavelength or decreasing order of

energy, gamma radiation being most energetic and radio wave being least

Gamma radiation

X-ray radiation

Wavelength Ultraviolet radiation Energy

Visible radiation

Infrared radiation

Terahertz radiation

Microwave radiation

Radio waves

UV radiation is distinguished into-

UV- C = (100-280 nm)

UV- B = (280 to 320 nm)

UV- A = (320 to 400 nm)

Visible spectrum (400nm to 700nm) is called photosynthetically active radiations (PAR), it

is also the visible spectrum.

Beyond 700 nm = Infrared

Albedo value (reflection coefficient) :

It is the ratio of reflected radiation to incident radiation.

Albus means white, so perfect white body will reflect all the incident sunlight and will have

albedo value of 1 (100%) and zero albedo value for no reflection of a perfectly black

surface.

In reality, it varies from 4% for charcoal to 90% for snow. Albedo is earth in general is 0.3,

much higher than ocean. Albedo of moon is 0.12 because of lack of atmosphere. Albedo of

certain surfaces are given below.

Fresh asphalt 0.04 or 4% Worn asphalt 0.12 Conifer forest 0.1 Deciduous trees 0.15 Bare soil 0.17 Green grass 0.25 Desert sand 0.40 New concrete 0.55 Ocean ice 0.5–0.7 Fresh snow 0.80–0.90 Fresh snow has maximum albedo

HYS: Environment and Ecology Part 1.5

Structure and Function of Ecosystem

Vertical distribution of different species occupying different levels is called stratification (meaning

layers). For example, trees occupy top vertical strata or layer of a forest, shrubs the second and

herbs and grasses occupy the bottom layers.

The components of the ecosystem:

(i) Productivity; (ii) Decomposition;

(iii) Energy flow; and (iv) Nutrient cycling.

Pond Ecosystem:

Self-sustainable unit, the abiotic component is the same as in earlier videos.

The solar input, the cycle of temperature, day-length and other climatic conditions

regulate the rate of function of the entire pond.

The autotrophs are phytoplanktons (plankton’s means passive drifter), algae, floating,

submerged and marginal plants.

Consumers are zooplanktons, the free swimming (nektons are active swimmers who can

swim independent of current), bottom dwelling forms (b for bottom b for benthos).

The decomposers are the fungi, bacteria and flagellates.

Functions include conversion of inorganic into organic material by autotrophs;

Consumption of the autotrophs by heterotrophs;

Decomposition and mineralisation of the dead matter to release them back for reuse.

There is unidirectional movement of energy towards the higher trophic levels and its

dissipation and loss as heat to the environment.

PRODUCTIVITY

Biomass: Mass of living biological organisms in a given area at a given time:

Species biomass- mass of one species;

Community biomass- mass of all species in the community (include microorganisms, plants

or animals). It is measured either in terms of dry weight (60-80% weight of water not

included) or by measuring organically bound carbon.

Standing crop: Total dried biomass of all the organism at a particular trophic level present

in a given area.

Primary Production: Total amount of biomass or organic matter produced per unit area. Unit in

terms of weight (g m– 2) or energy (kcal/m 2)

Note: Rate of production is called as productivity. Unit in terms of weight (g m– 2yr–1) or energy

(kcal m– 2 yr–1)

Primary productivity: Amount of biomass/organic matter (in terms of dry weight) produced per

unit area over a time period by plants during photosynthesis. It is expressed in terms of weight (g

m– 2yr–1) or energy (kcal m– 2 yr–1) per unit area (m– 2) per unit time (yr–1).

Primary Productivity of 2 types:

Gross primary productivity: Rate of production of organic matter during photosynthesis.

Net primary productivity (NPP) = (GPP – R): Gross primary productivity minus respiration

losses (R), and is the available biomass for the consumption to heterotrophs (herbivores

and decomposers).

Secondary productivity is defined as the rate of formation of new organic matter by consumers.

Factors influencing PP includes

plant species,

environmental factors,

availability of nutrients and

Photosynthetic capacity of plants.

E The annual net primary productivity of the whole biosphere is approximately 170 billion tons

(dry weight) of organic matter or 104.9 Gt C yr−1 (Giga or billion tonnes Carbon per year). Of

this, 56.4 Gt C yr−1 (53.8%), was the product of terrestrial organisms, while the remaining 48.5

Gt C yr−1, was accounted for by oceanic production, despite occupying about 70% of the

surface. So, productivity on land is far higher (426 gC/m²/yr for land production excluding

areas with permanent ice cover) than ocean (140 gC/m²/yr).

Per unit max productivity from Tropical rain forest In water, least productive is very deep lake

and highest productive is coral reef.

Nitrogen is limiting factor in oceans and phosphorus is in lakes

DECOMPOSITION

Decomposers break down complex organic matter (detritus-leaves, bark, flowers, dead

remains of animals, fecal matter), into inorganic substances like CO2, water and nutrients

and the process is called decomposition (5 steps: fragmentation, leaching, catabolism,

humification and mineralisation).

Detritivores (earthworm aka farmer’s ‘friend’) loosens the soils and break down detritus

into smaller particles (fragmentation). Water soluble inorganic nutrients go down into the

soil horizon and get precipitated as unavailable salts (leaching). Bacterial and fungal

enzymes degrade detritus into simpler inorganic substances (catabolism).

All the above steps operate simultaneously. Humification: accumulation of humus (dark

coloured amorphous substance acts as a reservoir of nutrients); highly resistant to

microbial action and decomposition. Humus is slowly degraded by some microbes and

release of inorganic nutrients occur by the process known as mineralisation.

Decomposition is faster if detritus is rich in nitrogen and water-soluble substances like

sugars with warm, moist, airy environment. Opposite like if detritus rich in lignin and

chitin, low temperature and anaerobiosis retards decomposition.

HYS: Environment and Ecology Part 1.6

ENERGY FLOW

Sun is the only source of energy for all ecosystems on earth. Exceptions include deep sea

hydro-thermal ecosystem where chemo-autotrophs like archaebacteria etc. are capable of

creatingorganic matter from some sulfur based compounds.

Incident solar radiation, if 100, about 50% is Photosynthetically Active Radiation (PAR)

from 400-700nm, which is also the visible spectrum. Out of PAR, 2-10% is actually fixed

into organic matter. And then unidirectional flow of energy starts as below

Sun Autotrophs Heterotrophs

Law of thermodynamics are obeyed in this energy flow

Energy neither created nor destroyed, only transformed.

Entropy law- transfer of energy leads to loss of energy as heat

Rule of 10% (10% law of Lindeman): energy is reduced by 10% during flow to every higher

tropic level. Because of this law, the number of trophic level are usually restricted to 4-5.

Right from sunlight being trapped by autotrophs into organic material, and further transfer

of energy to higher trophic levels, on an average, 10% (2-20%) of energy is transferred

while rest 90% (80-98%) is lost in respiratory and other losses. So as the number of trophic

levels increase in a food chain, most of the energy is lost. Hence, this is one of the

argument given in favor of adopting vegetarian food habits by human beings as this will

lead to us occupying second trophic level and less energy will be lost.

Heterotrophs = It includes both herbivores and carnivores. These are the organisms which

are unable to fix sunlight directly and hence, are dependent on plants directly or indirectly

for their energy requirements.

Herbivores: These animals feed on primary producers/ First trophic level/plants/

autotrophs and hence are known as secondary producers/ 2nd trophic level/ primary

consumers. Ex: Many insects, mammals etc. in terrestrial ecosystem and molluscs in

aquatic ecosystem

Carnivores: These animals eat other animals which in turn eat the plants (or their produce)

and are called secondary consumers/ tertiary producers.

Omnivores: Occupy many trophic levels and eat both plant and animals. Ex: Man.

Special points of biotic factor:

Nutrient mobilisation

Whale (filter feeder): secondary consumers

Vulture: scavenger and a decomposer

Insectivorous plant (double role) producers as well as consumers

Man and peacock: omnivores so occupy multiple trophic levels

Milk or curd eating: secondary consumers

Food Chain:

The green plant in the ecosystem-terminology are called producers. In a terrestrial

ecosystem, vascular plants, aquatic ecosystem phytoplankton, algae.

A food chain is a linear sequence of links in a food web. It goes through various trophic

(means nutrition) levels starting from autotrophs at first trophic level, going to herbivores,

carnivores and ending with decomposers. However, death of any organism mark the

starting of the detritus food chain/web.

Energy is transferred from one trophic level to another

Four trophic levels (can vary between 2-8) are present-

First tropic level [T1] = producer (Phytoplankton, Grass, Trees)

Second tropic level [T2] = primary consumer (Zooplankton, rabbit)

Third tropic level [T3] = secondary consumer (Birds, fishes)

Fourth tropic level [T4] = top consumer (Man, Lion)

Types of food chain

1) Grazing food chain or predatory food chain-

Dominant in aquatic ecosystem e.g. =

(Producer) (Prim. Consumer) (Sec. Consumer) (Top Consumer) Phytoplankton Zooplankton Small Fish Large Fish

{T1} {T2} {T3} {T4}

(Producer) (Prim. Cons.) (Sec. Cons.) (Top cons.) Grass Rabbit Fox Lion

{T1} {T2} {T3} {T4}

2) Parasitic food chain-

Pyramid of number is inverted.

Tree Birds Parasites [T1] [T2] [T3]

3) Detritus/saprophytic food chain-

Begins with dead organic matter, made up of decomposers like bacteria and fungi,

which release enzymes on the dead remains and decompose. (aka saprophytes because

‘sapros' means to decompose or osmotrophs meaning they absorb their nutrition

osmotically after digesting the food outside their body). Decomposers also play an

important role in mineral cycle (biogeochemical cycle)

Dominant in terrestrial ecosystem.

Energy flow is very slow but magnitude is great.

Dead Mangroves Bacteria, Fungi Insects Small Fishes Birds {T1} {T2} {T3} {T4} {T5}

HYS: Environment and Ecology Part 1.7

Food Web

A food web consists of all interconnected and overlapping food chains in an ecosystem.

Each organism in an ecosystem is part of multiple food chains.

Each food chain is one possible path that energy and nutrients may take as they move

through the ecosystem.

More the complex the food web, more will be the ecosystem stable and permanent.

Ecosystems with simple food web are less stable

Negative Feedback mechanism

Negative feedback mechanism

Cybernetics: a trans-disciplinary approach for exploring regulatory systems, their

structures, constraints, and possibilities. Useful when a system being analyzed is involved

in a closed signaling loop where action by the system generates some change in its

environment and that change provides feedback that triggers a system change

Homeostasis – Most of natural and biological systems, including ecosystem always remain

in a dynamic equilibrium with the help of a negative feedback cycle. In ecosystem, if any

change occurs in anytrophic level other trophic level will react accordingly.

Ecological Pyramids

Ecological Pyramid:

aka trophic pyramid

Is a graphical representation designed to show a particular character of ecosystem vis-

a-vis particular trophic levels.

It helps in simplifying the food chains and web and help us in better understanding of a

given ecosystem.

Three types:

Pyramid of number:

Usually upright. Ex: Grassland ecosystem

Total no. of organisms in a trophic level

Exception: Inverted in

Tree ecosystem. Ex: One tree have lakhs of insects dependent on it, 100s of small birds

feed on these insects and various large birds feed on the small birds.

Parasitic ecosystem: One host like dog has various fleas living on it, and fleas in turn

have their intestine infiltrated by protozoan hyper parasite.

Pyramid of biomass:

Usually upright.

Depicts the total biomass (dry mass) available at each trophic level.

Exception:

Inverted in case of aquatic ecosystem.

Phytoplanktons reproduce at a very rapid turnover rate so have a very little biomass at

a given time and are consumed byzooplanktons at equally fast pace. These

zooplanktons are theneaten by small fishes, and then there are large fishes.

Pyramid of Energy:

No exceptions of being inverted

Always upright, as ~ 90% of energy is while dissipated passing to a higher trophic level.

Represents the productivity of the ecosystem.

In this example, 1% of sunlight is fixed by autotrophs and then 10% of energy is

transferred upwards at every trophic level, so starting with amillion joules worth of

sunlight, only 10J reaches the top consumer

Limitations of ecological pyramids

Does not accommodate food web

Does not take into account the same species belonging to two ormore trophic level.

Saprophytes (decomposers or osmotrophs) are not given any place

Allen rule: Heat loss from extremities of mammals is extremely rapid so they tend to be very

small in colder region and large in warmer region.

Bergman rule: body size of birds and mammals is large in cold region and small in warm.

Jorden’s rule: fishes of cold water possess more no. of vertebra.

Gloger rule: mammals and birds are more darker in colour in hot areas.

Renschs rule: birds in cold region have narrow wings and in warm have broader.

Explanation: As the size decreases, the volume of an organism falls drastically. So, the ratio of

surface area to volume becomes very high in small mammals. So, the heat loss is too much

and too rapid for them to survive in colder region, so they are rarely found in polar and sub

polar region

HYS: Environment and EcologyPart 1.8 Biogeochemical cycles

Shelford’s Law of tolerance

Shelford's Law of Tolerance: an organism's success is based on acomplex set of

conditions having a certain minimum, maximum, andoptimum environmental factor or

combination of factors that determine success.

Beyond Optimum zone of tolerance on either side there is first zone of stress, followed by

zone of intolerance.

Bio-geochemical cycle or nutrient cycle:

The movement of nutrient elements across the ecosystem passing through many

components is called Biogeochemical cycle.

Bio – living organism

Geo – rock, soil, air, water

Chemical – material or nutrients

Cycle – path

The amount of nutrients (C, H, N etc.) present in soil at any given time is called standing

state.

There are 2 broad type of BGC cycles

(i) Gaseous cycle -

C, H, N, O cycles.

Reservoir exists largely in the atmosphere.

(ii) Sedimentary cycle –

P, S, Ca cycle.

Reservoir exists largely in the earth’s crust

Carbon cycle: Carbon constitutes 49% of dry weight of an organism. Ocean contains 71% of total

global carbon in dissolved form, atmosphere merely has 1%, which in turn is regulated by oceanic

reservoir. Fossil fuel also represent a reservoir of carbon. Carbon cycling occurs through

atmosphere, ocean and through living and dead organisms, decomposers. CO2 is given out by

respiration and fixed into organic matter during photosynthesis. Human activities have

significantly influenced the carbon-cycle. Rapid deforestation and massive burning of fossil fuel for

energy and transport have significantly increased the rate of release of carbon dioxide into the

atmosphere leading to Greenhouse effect

Nitrogen Cycle

1. Nitrogen fixation: By bacteria – Rhizobium, Azospirillum, Frankia, Clostridium, Bluegreen

algae (Anabena) , Nostoc,

Azotobacter is aerobic bacteria while Clostridium is anaerobic.

Relationship is known as Associative Symbiosis

2. Nitrification

Nitrosomonas/ nitrococcus, Nitrobactor

Ammonia Nitrite Nitrate NH3 NO2- NO3-

3. Nitrogen assimilation: by plant roots

4. Ammonification –

Litter ammonia

By bacillus bacteria

5. Denitrification

Nitrates free nitrogen

By pseudomonas bacteria

Phosphorus cycle

Sedimentary cycle

Main constitute of protoplasm, membranes, bones, nucleic acids, cellular energy transfer

apparatus.

Major source is rocks which have phosphates

Weathering of these rocks lead to release of Phosphorus and its absorption via plant roots,

which in turn gets transferred to higher trophic levels.

Excretory material of birds on the rocks called Guano is also a source of phosphorus.

Differences b/w carbon and phosphorus cycle

(i) Atmospheric input of phosphorus through rainfall is much smaller than carbon

(ii) Gaseous exchange of phosphorus is very small.

HYS: Environment and Ecology Part 1.9

ECOLOGY: Term coined by E. Haeckel. Scientific study of interactions or inter-relationship

among organisms and their environment.

Ramdeo Mishra- Father of Ecology in India.

Environment: Sum total of all conditions and influences that affect the development and life of

all organisms on earth.

Population: All organisms of a single species, inhabiting a particular area constitutes population.

It includes individuals of same species living at one place. Local population living in a particular

area are called demes.

Community: Group of organisms of different species living in common area, i.e. includes

multiple populations

Biological Hierarchy: Macromolecules (DNA, RNA etc.) , cells, tissues, organs, individual

organism.

Ecological Hierarchy : Organism, Population (species), Community, Ecosystem, Biome

Organism:

Smallest and basic unit of ecological study, small, large, uni or multi-cellular.

Natural cryopreservation: Help in prevention of body fluid from freezing, sugar trehalose,

antifreeze glycoproteins, peptides and other compounds.

Mimicry: Most common being Batesian mimicry, where a palatable species mimics an

unpalatable or noxious species.

Behavioural responses: Desert lizards bask in the sun and absorb heat when body temperature

drops, and move away when ambient temperature starts increasing, desert rodents burrowing

into the soil to hide and escape from the above-ground heat.

The tiger census in our national parks and tiger reserves is often based on pug marks and fecal

pellets.

Ecotone:

An ecotone is a transition area between two biomes, where two communities meet and

integrate, it may be narrow or wide, broad area or sharp boundary line, and it may be local (the

zone between a field and forest) or regional (the transition between forest and grassland

ecosystems).

Edge effects: Refer to the changes in population or community structures that occur at the

boundary of two habitats, leading to greater biodiversity. Ex: Estuary (partly enclosed coastal

body of brackish water with rivers or streams flowing into it, and with a free connection to the

open sea)

Ecocline:

Different from ecotone

“Physical transition zone” between two systems

Can be a thermocline, chemocline (chemical gradient), halocline (salinity gradient)

or pycnocline (variations in density of water)

Biological (phyto-climatic) spectrum- ratio or percentage distribution of different

life forms in any plant communities.

Biotic potential- Maximum reproductive capacity of any species

Biological Hierarchy:

Dumb Kids Prefer Candy Over Fancy Green Salad

Domain > Kingdom > Phylum > Class > Order > Family > Genus > Species.

Kids Put Cat On Firey Gas Stove

Altruism- behaviour of the individual to increase the chance of survival of others of same species

(SACRIFICIAL BEHAVIOUR) in spotted dear

Communication between species happen via - chemical signals- pheromones, tactile signals

(contact), visual signals, auditory signals

Speciation: Process of creation of new species by separation of population of plants and

animals, originally able to interbred, into independent evolutionary units which can no longer

interbred to produce fertile offspring due to accumulated genetic differences.

Species: Largest group of organisms capable of interbreeding and producing fertile offspring. It

is the basic unit of classification, similar in structure, function and behaviour produced by similar

parents, having common gene pool, can interbreed under natural conditions Partial exceptions:

Mule-offspring of a male donkey (jack) and a female horse (mare), Liger- hybrid cross (male lion

with a female tiger), Tigon/Tiglon (male tiger+lioness), theses offsprings are usually sterile.

Endemic species- Found only in particular area

A keystone species is a species that has a disproportionately large effect on its community’s

characteristic and environment relative to its numerical strength, playing a critical role in

maintaining and determining the types and numbers of various other species in the community.

It is analogous to keystone of an arch in architecture where the arch collapses without the

keystone.

Predators:

Jaguar can feed on up to 87 species and hence, a small number of such predators

prevents herbivorous species from eliminating dominant plant species and dramatically

alter the character of the ecosystem.

The sea otter is an important predator of sea urchins, who otherwise will destroy coral

reefs and kelp roots. These kelp plants increase the productivity and also provide habitat

to many other species.

Various pollinators like honey bees are dependent upon a single tree for its nectar need,

making the tree species a keystone species.

In mycorrhizae, a unique fungal species can act as a keystone species.

In the African savanna, elephants destroy trees making room for the grass species.

Ecosystem engineers

In North America, the prairie dog burrows provide the nesting areas, tunnel systems also

help channel rainwater into the water table to prevent runoff and erosion, increasing

aeration and reversing soil compaction that can be a result of cattle grazing.

Beaver transforms its territory from a stream to a pond or swamp, by cutting down

trees. Beaver dams alter the riparian area they are established in and provide benefit to

many species including amphibians, salmon, and song birds.

Indicator species (Sentinel Organism) :

Species that defines a trait or characteristic of the environment i.e. a species whose

presence indicates human-created abiotic conditions such as air or water pollution.

So they are used to monitor the health of an environment or ecosystem as their function,

population, or status can reveal what degree of ecosystem or environmental integrity is

present.

For example, a species may delineate an ecoregion or indicate an environmental condition

such as a disease outbreak, pollution, species competition or climate change, acts as an

early warning to monitoring authorities. Ex: Lichen presence denotes low air pollution,

presence of stonefly indicates high dissolved oxygen in water, mollusc are very sensitive to

water pollution.

Exotic Species: An introduced, alien, non-indigenous, or non-native species, is a species living

outside its endemic or natural distributional range, due to anthropogenic activity, either

deliberate or accidental.

Invasive species: Have a negative effect on a local ecosystem, compete with the local species for

similar limited resources, leading to decline or extinction of indigenous species. Ex:

Nile perch’s introduction into Lake Victoria in east Africa led to extinction of 200 species of

cichlid species.

Carrot grass (Parthenium), Lantana and water hyacinth (Eicchornia) are invasive weed

species and have caused widespread environmental damage, also pose threat to our

native species

African catfish Clarias for aquaculture purposes is posing a threat to the indigenous

catfishes in our rivers.

Flagship species: Conservation biology. The flagship species concept holds that by raising the

profile of a particular species, it can successfully leverage more support for biodiversity

conservation at large in a particular context. Popular, charismatic species that conjure awe and

serve as symbols and rallying points to stimulate conservation awareness and action. Ex: Bengal

tiger, the giant panda, African and Asian elephant.

Umbrella species: A wide-ranging species whose requirements include those of many other

species and helps in protecting these species indirectly protects the many other species that make

up the ecological community of its habitat conservation related decisions. Tigers in India so

Project Tiger was launched to save the tiger and thereby its habitat and other species within it.

Source: https://www.youtube.com/user/unacademy

Compiled by: Ashish Desai