Ecology and Ecosystems
Ecology is the scientific study of relations that living
organisms have with respect to each other and their
Under ecology, we study various ecosystems which are a
part of the biosphere.
An ecosystem includes all the organisms and the nonliving
environment that are found in a particular place.
Ecological succession is the
observed process of change in
the species structure of an
ecological community over
Ecological succession occurs
when the conditions of an
environment suddenly and
drastically change. 2
• A tropic level is the position occupied
by an organism in a food chain.
Trophic levels can be analyzed on an
• Producers are found at the base of
the pyramid and compromise the first
• Primary consumers make up the
second trophic level.
• Secondary consumers make up the
third trophic level.
• Finally tertiary consumers make up
the top trophic level.
A food chain shows the feeding relationship between
different living things in a particular habitat.
Food chains show how energy is passed from the sun to
producers, from producers to consumers, and from
consumers to decomposers.
In any ecosystem, many food chains overlap. When this
happens, the food chain forms a food web.
Grazing Food Chain
The "grazing" food chain includes the producers
and consumers that cycle energy from living
plants. The "detritus" food chain cycles energy
from non-living remains of both plants and
animals (also called detritus).
The "grazing" food chain has a number of steps
that start with the producers, or the plants,
and flows through a series of levels of consumers.
At each step only about 10% of the energy is
passed up through the chain. The rest is passed
back into the atmosphere as heat through
breathing and decomposition.
In the first step plants convert the sun’s energy to chemical energy through a
process called photosynthesis. The chemical energy is stored both as food and
as structural elements in the plant.
The next step involves the primary consumers, animals that eat only plants.
At step three are the secondary consumers, also called predators; these
animals eat primary consumers.
At step four are the tertiary consumers that eat secondary consumers, and
sometimes primary consumers as well
Detritus food chain
The "detritus" food chain cycles energy from non-
living remains of both plants and animals (also called
The "detritus" food chain is a system where the energy produced by the breakdown of dead plant and
animal matter is cycled into the "grazing" food chain.
Detritus is organic matter formed by decaying animal or plant tissue, or fecal matter.
Detritus eaters (or detritivores) such as insects, worms and other small organisms feed on dead plants,
waste products from animals and dead animals.
Decomposers are fungal or bacterial organisms that work within the dead material to help break it down,
activating decay and decomposition.
This important part of the ecosystem takes the last of the energy that was originally absorbed by the plants
and returns it to the soil.
Characteristics of Detritus Food Chain
a)Primary source of energy is dead organic matter called 'detritus'
which are fallen leaves, plant parts or dead animal bodies.
b) Primary consumers are 'detritivores' including protozoans,
bacteria, fungi, etc which feed upon the detritus saprophytically.
c) Detritivores are in turn eaten by secondary consumers such as
insect larvae, nematodes, etc.
d) Detritus food chains are generally shorter than grazing food chains
e) In nature, detritus food chains are vital as the dead organic matter
of grazing food chain is acted upon by the detritivores to recycle the
inorganic elements into the ecosystem.
Food Webs are Food Chains that
intersect each other. Food webs are
what really happens in nature.
A predator from one food chain may
be linked to the prey of another food
Several food chains linked together
An ecological pyramid is a graphical
representation designed to show…….
the number of organisms,
energy relationships, and
biomass of an ecosystem.
They are also called Eltonian pyramids after Charles
Elton, who developed the concept of ecological
Charles Elton (1927) developed the concept of ecological
pyramids who noted that "…the animals at the base
of a food chain are relatively abundant while those at
the end are relatively few in number…"
Producer organisms (usually green plants) form the base
of the pyramid,
With succeeding levels above representing the different
trophic levels (respective position of the organisms
within ecological food chains).
Succeeding levels in the pyramid represent the
dependence of the organisms at a given level on the
organisms at lower level.
There are three types of pyramids:
of numbers, of biomass, and of energy.
Pyramid of Biomass
Biomass is (is the mass of living biological organisms in a given area
or ecosystem at a given time) renewable organic (living) material.
A pyramid of biomass is a representation of the amount of energy
contained in biomass, at different trophic levels for a particular time.
It is measured in grams per meter2, or calories per meter2. This
demonstrates the amount of matter lost between trophic levels.
Each level is dependent on its lower level for energy, hence the lower
level determines how much energy will be available to the upper
level. Also, energy is lost in transfer so the amount of energy is less
higher up the pyramid.
There are two types of biomass pyramids: upright
An upright pyramid is one where the combined
weight of producers is larger than the combined
weight of consumers. An example is a forest
An inverted pyramid is one where the combined
weight of producers is smaller than the combined
weight of consumers. An example is an aquatic
Pyramid of Numbers
The pyramid of numbers represents the number of organisms in each trophic level.
This pyramid consists of a plot of relationships between the number herbivores
(primary consumers), first level carnivore (secondary consumers), second level
carnivore (tertiary consumers) and so forth. This shape varies from ecosystem to
ecosystem because the number of organisms at each level is variable
Upright, partly upright and inverted are the three types of pyramids of numbers.
An aquatic ecosystem is an example of upright pyramid where the number of
organisms becomes fewer and fewer higher up in the pyramid.
A forest ecosystem is an example of a partially upright pyramid, as fewer
producers support more primary consumers, but there are less secondary and
An inverted pyramid of numbers is one where the number of organisms depending
on the lower levels grows closer toward the apex. A parasitic food chain is an
Pyramid of Energy
The pyramid of energy represents the total amount of energy
consumed by each trophic level. An energy pyramid is always
upright as the total amount of energy available for utilization
in the layers above is less than the energy available in the lower
levels. This happens because during energy transfer from lower
to higher levels, some energy is always lost.
A forest ecosystem is a
terrestrial unit of living
All interacting among
themselves and with the
environment (soil, climate,
water and light) in which
they live. 14
Types Of Forest Ecosystems
Tropical Rain Forest
( Average rain fall: <150cm/year)
Warmed , humid, high diversity of
animal, plant, insects
Tropical Deciduous Forest
(Rain fall: 100-120cm/yr)
Climate is not evenly distributed
(cold climate, annual temp: 7-15oC)
Summer is very hot and winter is very cold
Tall decidous tree
Climate is very cold
Rainfall: 100mm to 350 mm
Temperate Rain forest
Winter rain fall
Summer is very hot and Dry
Functions Forest Ecosystems
Enhance the water resources in both quality
Hydrological cycle depend on the forest
Forest gives shelter to wildlife and fish
Considered as a pathway for exchange and
regulation of atmospheric gases, water and trace
Grasslands are areas where the vegetation is dominated
Types Of Grassland
Tropical and Savannas
Tropical and subtropical grasslands,
savannas, and shrublands are
a grassland terrestrial biome located
in semi-arid to semi-
humid climate regions
of subtropical and tropical latitudes.
Tropical grasslands include the savanna
usually associated with Africa, and
savanna-type grasslands found in India,
Australia, Nepal and the Americas.
Temperature: warm to hot season (often with a cold to
freezing season in winter)
Soil: fertile with rich nutrients and minerals
Plants: grass; trees or shrubs in savanna and shrubland
Animals: large, grazing mammals; birds; reptiles
Rain fall: 25-60cm/yr
Although large areas have now been converted to
agriculture, in the past temperate grasslands were
home to herds of large grazing animals such as bison,
deer or kangaroos.
North America, the steppes of Russia and the pampas
Flooded Grass land
Flooded grasslands and savannas is a
Its component ecoregions are generally
located at subtropical
and tropical latitudes, which
are flooded seasonally or year-round.
A common term is swamp.
Flooded grasslands are characterized by:
very wet to saturated soil moisture
content in nutrient rich soils.
in temperate—warm to tropical—hot
They are found as grasslands, savannas,
Tundra is the coldest of all the biomes.
Tundra comes from the Spanish word
tunturia, meaning treeless plain.
It is noted for its frost-molded
landscapes, extremely low
temperatures, little precipitation, poor
nutrients, and short growing seasons.
The two major nutrients are nitrogen
and phosphorus. Nitrogen is created by
biological fixation, and phosphorus is
created by precipitation.
Tundra is separated into two types:
arctic tundra and alpine tundra.
Extremely cold climate
Low biotic diversity
Simple vegetation structure
Short season of growth and reproduction
Energy and nutrients in the form of dead
Arctic tundra is located in the northern hemisphere, encircling the north pole
and extending south to the coniferous forests of the taiga.
The arctic is known for its cold, desert-like conditions.
The growing season ranges from 50 to 60 days.
The average winter temperature is -34° C (-30° F), but the average summer
temperature is 3-12° C (37-54° F) which enables this biome to sustain life.
Rainfall may vary in different regions of the arctic. Yearly precipitation,
including melting snow, is 15 to 25 cm (6 to 10 inches). Soil is formed slowly.
Alpine tundra is located on mountains throughout the world at high altitude
where trees cannot grow. The growing season is approximately 180 days
Mammals: pikas, marmots, mountain goats, sheep, elk
Birds: grouselike birds
Insects: springtails, beetles, grasshoppers, butterflies
High-altitude grasslands located on high mountain
ranges around the world, like the Páramo
of the Andes Mountains. They are part of the
montane grasslands and shrublands biome and
also constitute tundra.
Desert and xeric
Also called desert grasslands, this is
composed of sparse grassland ecoregions
located in the deserts and xeric shrublands
A desert ecosystem exists where
there is little rainfall and the
climate is extreme in harshness.
It occupies about 17% of the
Types Of Desert Ecosystem
Temperate Deserts: Sahara in Africa, Thar
Tropical Deserts: Mojave in south
Cold Deserts: Gobi desert in China
Components of desert
A biotic components: Nutrition's present in the soil and aerial
Producers: There are shrubs, Grasses and few trees. Some
time few cacti
Consumers: Reptiles, Insects, Birds mammals and camels
Decomposers: There are very few, as due to poor vegetation
the amount of dead organic matter is less.
There are few fungi and most of them are thermophlic
Mojave in south California
Gobi desert in China
It is an ecosystem located in
a water bodies.
The two main types of
aquatic ecosystems are
marine ecosystems and
freshwater ecosystems. 23
Types Of Aquatic Ecosystem
1. Pond ecosystem
2. Lake ecosystem
4. Riverine Ecosystem
5. Fresh water marshes ecosystem
On the basis of water flow, fresh water
ecosystem classified into two
- Lentic ecosystem (Standing water
- Lotic ecosystem (Running or flowing
Lotic ecosystem may be perennial or seasonal
Perennials occasionally subjected to floods which
cause damage to the surrounding areas
Lotic series distinguished by continued flow of water in
Lotic systems are richer in oxygen and nutrients than
Egs:Spring,Stream or river ecosystems
It may be perennial or seasonal
Oxygen content in the surface water to a depth of 3-
5 meters is enough to support life
In deeper levels oxygen is less and biological
In bottom levels anaerobic conditions prevail and
organisms that can thrive under such conditions are
found at this depth
Egs: Lake,Pond,Swamp,Reservoirs etc
It is a simplest fresh water aquatic ecosystem
It is a small body of standing shallow water
It may receive enough water during rainy season
It is a self sufficient & self regulatory ecosystem
Life span of small seasonal ponds ranges from a
few weeks or months
Life span of larger ponds are several hundred
Pond water contain a mixture of living organisms,
both plants & animals, and inorganic and organic
Big and natural fresh water bodies with standing
Functions like a giant permanent pond
Lakes are formed when precipitation run-off or
ground water seepage fills up depressions in the
land formed by geological changes.
A large lake has four
zones(depending on the depth).They
- LITTORAL: upper zone ,shallow
water near the shore of lake.
-LIMNETIC: open water away from
the shore of lake.
dark,not found plants or algae.
-BENTHIC: bottom of the lake.
Types of Lake
Artificial lake: Due to construction
Obligotrophic lake: Low nutrition concentration
Masotrphic: Moderate Nutrition
Eutrophic: More amount of Nutrition : Dal Lake
Dystrophic lake: Brown water with low pH and humic
Desert salt lake: High concentration of Salts: Sambhar
Volcanic lake: It occures by volcano: Japan
Meromictic lake : Rich in salt
RIVER AND STREAM ECOSYSTEM
They are flowing fresh water bodies.
Flowing water follows distinct “channels”.
Small channels – STREAMS
Large channels – RIVERS
Plants and animals live in streams and rivers
depend upon the movement and speed of the
It tend to be naturally fertile ecosystem.
It is valuable in maintaining water tables in
Periodic fluctuations in water levels resulting
from seasonal and annual rainfall variation often
accomplishes tidal like actions in terms of
maintaining long range stability and fertility.
70% world cover by the water and 97% of this
water is available in oceans and Seas.
They play key role in survival of 2,50,000 species
Oceans are major sinks of CO2 and play
important role in Carbon cycle, Hydrological
Major ocean: Pacific, Atlantic, Indian, Arctic
Pacific: Largest and cover 1/3 part of Earth
Coastal Zone: Relatively warmer, Nutrition rich shallow water
with sunlight and high production
Open Sea: Deeper part of ocean and away from submerged
part of Continent is called continental shelf.
Euphotic zone: Received Enough light
Bathyal Zone: Dim light
Abyssal Zone: 1.5 to 5 km deep dark zone. No solar energy
Components of marine
Abiotic Components: Salt concentration in open
sea is usually 3.5 % while dominant ions are
sodium, chloride, sulpher magnasium and calcium
Producers: phytoplanktons : macro and micro algae,
Consumers: Herbivorous and Carnivores and top
Decomposers: Bacteria and fungi
describe the flow of essential elementsessential elements from the environment through living
organisms and back into the environment.
The biogeochemical cycle is the continuous flow of elements and compounds
between organisms and the earth
Types of cycles
Hydrological cycle: deal with the interchange of
water with organisms and environment
Gaseous cycle: Deal with inter change with gases
Sedimentary cycle: Deals with SO4 and PO4 cycle
and concern with the interchange of nutrition and
H, O, and C make up > 99 % of the Earth’s biomass
N, Ca, K, Mg, S, and P are significant nutrients
Cycling of C, O, N, P, and S are discussed in this
Concepts in Biogeo. Cycles
Reservoir - where material or mass is stored
Flux: rate of flow of material
Steady state: inflow = outflow
Dynamic state: fluxes are reservoirs are changing
Residence time: length of time a chemical stays in a
Feedback: positive and negative
1. Reservoir – oceans, air (as water vapor), groundwater, lakes and
glaciers; evaporation, wind and precipitation (rain) move water from
oceans to land.
2. Assimilation – plants absorb water from the ground, animals drink
water or eat other organisms which are composed mostly of water.
3. Release – plants transpire, animals breathe and expel liquid wastes.
Evaporation and transpiration
Condensation and formation of cloud: Rising air current all the vapour
up into the atmosphere cool formation of cloud cloud is made
up of droplet of water
Precipitation: Snow or rain fall
Run off and collection of under ground water
Infiltration and percolation
Pollution of water
Reduces the vegetation cover increases the
surface ran off decreases the percolation
Heavy deforestation reduces the transpiration
loss of water through plants and trees
Earth atmosphere contains 0.03% of CO2
CO2 is the basic source of carbon and
constitutes of all organic material
It found in caves ands mines and also evolves
Reservoirs of Carbon
Carbon is found in all four spheres
Biosphere - organic matter
Atmosphere - CO2, CH4
Hydrosphere - H2CO3 ,HCO3
Lithosphere - CaCO3 , coal, oil, and gas
Processes: photosynthesis, formation of sediments, weathering,
combustion, plate tectonics
Decay of organic material
Carbon CycleCarbon Cycle
(carbon is required for building organic compounds)
1. Reservoir – atmosphere (as CO2), fossil fuels (oil, coal),
durable organic materials (for example:
2. Assimilation – plants use CO2 in photosynthesis; animals
3. Release – plants and animals release CO2 through
respiration and decomposition; CO2 is released
as wood and fossil fuels are burned.
Extraction and combustion of fossil fuels (speeds up
the medium-term cycling)
Deforestation (biomass burning)
All of these processes release CO2 into the
atmosphere and affect the natural cycling of carbon
Nitrogen is an essential constituent of animals and
Green plant combined with Nitrogen and
carbohydrates to make proteins and Nucleic acid
Not directly used most form of life
Taken by Process called nitrogen fixation
Nitrogen CycleNitrogen Cycle
(Nitrogen is required for the manufacture of
amino acids and nucleic acids)
1. Reservoir – atmosphere (as N2); soil (as NH4
ammonium, NH3 or ammonia, N02
Nitrogen CycleNitrogen Cycle
2. Assimilation – plants absorb nitrogen as either
or as N03
, animals obtain nitrogen
by eating plants and other animals. The
stages in the assimilation of nitrogen
are as follows:
Nitrification and Denitrification
Nitrogen Fixation: N2 to NH4
by nitrogen-fixing bacteria (prokaryotes
in the soil and root nodules), N2 to N03
and UV radiation.
1. Biological : Nitrogen fixing bacteria
2. Industrial fixation: fertilizer
3. Electrification( N2 + O2-- Nitrogen Oxide
Amonification: Amino acid and urea- Ammonia
1. Nitrogen fixation
Combination of Nitrogen with other element
Organic Nitrogen- NH3
3. Nitrification and denitrification
Ammonia(NH3)- ----- Nitrite forming bacteria(Nitromonas)----- Nitrite(NO2)
Nitrogen CycleNitrogen Cycle
3. Release – Denitrifying bacteria convert N03
to N2 (denitrification); detrivorous
bacteria convert organic compounds
back to NH4
(or NH3) urea, or uric acid.
Harvesting of timber
Automobile and industrial exhaust
Acid rain is caused by emissions of sulfur
dioxide and nitrogen oxide, which react with
the water molecules in the atmosphere to produce
NO2 + OH· → HNO3
Essential for aerobic life
Closely linked to carbon cycle
Very large reservoir (21% of gas in atm.), not susceptible to human
Also, not a greenhouse gas
Reservoirs: atmosphere, surface organic material (biosphere), and buried
organic matter (lithosphere)
Photosynthesis/ respiration: short-term cycle; balanced on land;
excess O2 in ocean -phytoplanktons
Mineral oxidation, weathering, burial - removes O2 from
Combustion or weathering of organic matter - removes O2 from
Atmosphere => marine biota => sediments => rocks =>
atmosphere (fig )
Phosphorus CyclePhosphorus Cycle
(Phosphorus is required for the manufacture
of ATP and all nucleic acids)
1. Reservoir – erosion transfers phosphorus to water and soil;
sediments and rocks that accumulate on ocean
floors return to the surface as a result of uplifting by
2. Assimilation – plants absorb inorganic PO4
soils; animals obtain organic phosphorus when they
plants and other animals
3. Release – plants and animals release phosphorus when they
decompose; animals excrete phosphorus in their
Phosphorus CyclePhosphorus Cycle
1. Reservoir – erosion transfers
phosphorus to water and soil;
sediments and rocks that
accumulate on ocean floors return
to the surface as a result of uplifting
by geological processes
2. Assimilation – plants absorb
soils; animals obtain organic
phosphorus when they plants and
3. Release – plants and animals
release phosphorus when they
decompose; animals excrete
phosphorus in their waste products
Biogeochemical cycles of other minerals,
such as calcium and magnesium, are
similar to the phosphorus cycle.