Ecology

• Elements of ecology: System, open system, closed system.

• Definition of ecology, species, population, community.
• Definition of ecosystem- components types and function.
• Structure and function of the following ecosystem: Forest ecosystem,
Grassland ecosystem, Desert ecosystem, Aquatic ecosystems, Mangrove
ecosystem (special reference to Sundar ban);
• Food chain [definition and one example of each food chain], Food web.
• Biogeochemical Cycle- definition, significance, flow chart of different
cycles with only elementary reaction [Oxygen, carbon, Nitrogen,
Phosphate, Sulphur].
• Biodiversity- types, importance, Endemic species, Biodiversity Hot-
spot, Threats to biodiversity, Conservation of biodiversity.
 Ecology
❖ Ecology came from Greek word “Oikos”-house & “Logos”-study.
❖ Ernst Haeckel, a German zoologist coined the term Ecology in 1866.
❖ The most acceptable definition of ecology was proposed by Charles Krebs in 1985.
❖ Ecology is the scientific study of interaction between organisms and their environments,
focusing on energy transfer, that determines the distribution and abundance of organisms.
❖ The main objective to study ecology is to understand & take proper measures if and when
required.

ECOSYSTEM
▪ According to thermodynamics, system is an integral part of universe and is separated by a
boundary.
▪ A.G. Tansley coined the term Ecosystem in 1935
▪ Ecosystem is a system where biotic and abiotic components are living together &
determine the effect of abiotic components on biotic components.
▪ Every ecosystem have their specific biotic and abiotic components related to each other.
▪ One ecosystem is dependent on other.
▪ A dynamic ecosystem makes the balance of nature.
An example of an ecosystem is a pond. In a pond, the living things
are the biotic factors, such as fish, aquatic plants, and aquatic
animals. The non-living things are the abiotic factors such as
sunlight, water quality, and sediment.
 Cell: Basic structural & functional unit.
Individual: Any unicellular or
multicellular form that exhibit all of the
characteristics of life.
A population is a group of organisms
belonging to the same species that live
in the same area and interact with one
another.

A community is all of the populations of different species that live in the same area and interact
with one another. A community is composed of all of the biotic factors of an area.
An ecosystem includes the living organisms of all the populations in an area and the non-living
aspects of the environment. An ecosystem is made of the biotic and abiotic factors in an area.
Biome: Set of ecosystem sharing similar characteristics with their abiotic factors adopted to
their environment.
The biosphere is the part of the planet with living organisms. The biosphere includes most of
There are three main type of feeding relationship
1. Producer-consumer
2. Predator – Prey
3. Parasite - Host
 Food Chain
• A food chain is the sequence of who eats whom in a biological community (an
ecosystem) to obtain nutrition.
• A food chain shows how each living thing gets food and how nutrients and energy
are passed from creature to creature.
A grazing food chain is a food chain which starts with green plants as the main
source of energy and culminate with carnivores.
1. Predatory food chain: Proceeds from small to large animals. Example: Crops-
field mice-owls. The animals that are eaten are called prey. Predators are at the
top of a food chain.
2. Parasitic food chain: Proceeds from large to small animals. Example: crop-
birds- lice-bacteria.

A Detritus or saprophytic
food chain is that which
start with dead organic
matter. Here, since the
source of energy is not the
sun but detritus, this linear
feeding relationship is
called a detritus food chain.
 Food Web
A food web consists of all the food chains in a single ecosystem. Each living thing in
an ecosystem is part of multiple food chains. All of the interconnected and
overlapping matrix of food chains in an ecosystem make up a food web.

In nature, food chain

relationships are not
isolated, rather they are
complex, because one
organism may form the
food source of many
organisms.
Food webs are
indispensable in
ecosystems as they allow
an organism to obtain its
food from more than one
type of organism of the
lower trophic level.
Energy Flow
The sun’s energy flows into organisms
that can change the sunlight into food
then into organisms that eat them.

Chemical cycling
Chemical cycling describes systems of
repeated circulation of chemicals
between biotic and abiotic components,
and back to their original state, that
occurs in space, and on many objects in
space including the Earth.
 Energy flow in ecosystem
The plant kingdom traps solar energy with help of chlorophyll and convert the solar energy to
food. The rate of food production in unit area per unit time is called productivity.
The total amount of energy stored by plants per unit area per unit time is called Gross
primary productivity (GPP). Since plants require energy for synthesis and functioning of their
body, some of GPP is used by plant body in the process of respiration. The remaining energy
is transfer to the next level and it is called Net Primary Productivity (NPP).

This process repeats to top

carnivores level. Normally, 80%
to 90% energy is lost in each
level. Thus in each level, there is
degradation of energy.

NPP = GPP- Respiration

 Ecological pyramid
A graphical representation designed to show the biomass or productivity at each
level in a particular ecosystem.
Ecological Pyramid: 3 types
1. Pyramid of numbers
2. Pyramid of Biomass
3. Pyramid of Energy
Ecosystem is a dynamic complex of plant, animal and micro-organism
communities and their non-living environment, interacting ass a
functional unit.
Ecosystem is a system where biotic and abiotic components are living together &
determine the effect of abiotic components on biotic components. Every
ecosystem have their specific biotic & abiotic components related to each other.
A dynamic ecosystem makes the balance of nature.

Block Diagram of Ecosystem

▪ Aquatic ecology is the study of water-based ecosystem.
▪ Aquatic ecosystems include oceans, lakes, rivers, streams, estuaries, and wetlands.
Within these aquatic ecosystems living things are those depend on the water for survival,
such as fish, plants, and microorganisms.
▪ The definition excludes most groundwater systems.
 Marine Ecosystem
Marine ecosystem are the largest of Earth's aquatic ecosystems and exist in water that have a
high salt content. Marine ecosystems can be divided into many zones depending upon water
depth and shoreline features. These ecosystems are different from freshwater ecosystem
mainly because of its salty water.
Biotic Components:
1. Producers:
It includes phytoplanktons (diatoms, dinoflagillates), large seaweeds (mainly algae like
chlorophyceae, phaeophyceae and rhodophyceae; angiosperms like Ruppia, Zostera,
posidonia), and mangrove vegetation (like Rhizophora, Carapa etc.)
2. Consumers:
(a) Primary consumers:
These are herbivores and feed directly on producers (Crustaceans, Mollusks, fish etc.)
(b) Secondary consumers:
These are carnivorous fishes (Herring, Shad and Mackerel)
(c) Tertiary consumers:
These are top carnivorous fishes (Cod, Haddock, shark etc.)
3. Decomposers:
These are micro-organisms like bacteria, fungi.
Abiotic Components:
High Na, Ca, Mg and K salt concentration, variable dissolved oxygen content, light and
temperature make a unique physiochemical conditions in marine water.
 Freshwater ecosystem
Freshwater ecosystem include lakes, ponds, rivers, streams, wetlands etc.
Freshwater Ecosystem Characteristics
• The freshwater ecosystem is a habitat for various plant and animal species as it is quite
rich in terms of nutrition and minerals.
• The freshwater ecosystem is less saline, unlike the marine ecosystem.
• The temperature in this ecosystem varies depending on some factors like location,
season, and depth from the water surface.
• The freshwater ecosystem contains sediments at the bottom. In gentle flowing freshwater
bodies or still water bodies, the sediments remain in place.
• The freshwater ecosystem provides a suitable environment for various species of flora
and fauna.
• In a freshwater ecosystem, types of biotic factors are aquatic plants, fish, amphibians,
and algae.
• Green algae, red algae and diatoms are all common types of algae that are found in
freshwater ecosystems.
• Some other common freshwater species are : Frogs and toads, Aquatic birds, Terrestrial
birds that feed on fish/organisms in the freshwater, Alligators and crocodiles, Water
snakes, Turtles etc.
 Plant Adaptations
Plants germinate, grow, flower, and
release seeds within the brief
period (6-8 weeks) when water is
available and temperatures are
warm. Desert sunflower and desert
marigold complete their life cycles
during brief rainy seasons.

•Cacti and other succulent plants store water in their spines, which are residual
leaves, thick stems, deep roots.
•The shrub in desert ecosystem have waxy coating and sunken type of stomata on
leaves, which reduces loss of water during transpiration.
Animal Adaptation
•Camels have humps, wide hooves, thick fur, thick lips & tongue to adopt in the
desert and are suited to travel long periods of time without water. Lions live in the
deserts of Africa.
•Small rodents find homes in the desert, with variations from gerbils to hedgehogs.
Larger hyenas and jackals are also often found in deserts.
•Lizards and snakes are particularly suited to the dry, hot climate of the desert.
 Mangrove Ecosystem
Biotic component
1. The food chain of a mangrove forest relies heavily
on the recycling of the detritus, made by the falling
leaves of the trees. These are the burrowing crab,
snapping shrimp, tube worm. These species, because
they are eating the plant material, are considered the
primary consumers of the ecosystem and the
mangroves are the main producers.
2. Next level is the smaller fish of the mangrove forests. Some of these fish are the
mosquitofish, the least killifish, and the sail fin molly.
3. The top level of this food chain are the wading birds, such as egrets or ospreys. They feed
on the fish is the community, who take shelter in the roots of the mangrove trees.

Abiotic component
1. Soil: sand + mud + silt
2. pH: neutral or slightly acidic due to the ‘sulfur reducing bacteria’ and the presence of
acidic silt.
3. Nutrient: Because the soli is perpetually waterlogged, there is little free oxygen.
Anaerobic bacteria liberate nitrogen gas, soluble iron, inorganic phosphates and methane,
which makes the soil much less nutritious.
 Biogeochemical Cycle
▪ The body of living organisms are made up of C, H, N, O & P and
minute quantities of Ca, Fe, Cu & Mo.
▪ These chemical elements are transporting from the living body to
the nonliving parts of the environment.
▪ The cycling of elements through the atmosphere, hydrosphere,
biosphere and lithosphere is known as biogeochemical cycle.
▪ Main reservoirs of elemens are the atmosphere and the ocean.
▪ These elements cycle in either a gas cycle or a sedimentary cycle.
▪ In a gas cycle elements move through the atmosphere.(like oxygen
cycle)
▪ Sedimentary cycle elements move from land to water to
sediment.(like phosphorous cycle)
▪ Sulphur represents a combination of gaseous and sedimentary
cycle.
 Carbon Cycle
▪ Carbon enters the biosphere during photosynthesis:
▪ CO2 + H2O ---> C6H12O6 + O2 + H2O
▪ Carbon is returned to the biosphere in cellular respiration:
▪ O2 +H2O + C6H12O6 ---> CO2 +H2O + energy

▪Oceans are richest

source of carbon as
carbonate or
bicarbonate, 50 times
more carbon than that
of atmosphere.
Oxygen Cycle
 Phosphorus Cycle
❑ The phosphorus cycle is the slowest biogeochemical cycle that describes the movements of
phosphorus through the lithosphere, hydrosphere & biosphere.
❑ The source of Phosphorus is rock as inorganic soluble and non-soluble phosphate.
❑ Phosphate is required for growth of bones, teeth, component of DNA, RNA, ATP, proteins and
enzymes.
❑ Low concentration of P in soils reduce plant growth & shows soil microbial growth.
❑ It is returned to sediment .

❑Phosphorus is taken up by
plant roots, converted to
organic phosphate, then
travels through food chains
and finally decomposed by
microorganisms to soil.
 Sulfur Cycle
▪ In nature it can be found as pure element, and as sulfide and sulfate minerals.

▪ Cycles in both a gas and sedimentary cycle.

▪ The natural source of Sulfur is the lithosphere (earth's crust)

▪ Sulfur (S) enters the atmosphere as hydrogen sulfide (H2S) during fossil fuel
combustion, volcanic eruptions, gas exchange at ocean surfaces, and
decomposition. Microorganisms turns into H2S (gas)

▪ SO2 and water vapor makes H2SO4 (a weak sulfuric acid),

which is then carried to Earth in rainfall.

▪ Sulfur in soluble form is taken up by plant roots and

incorporated into amino acids such as cysteine. It then travels through the food
chain and is eventually released through decomposition.
▪
 Nitrogen Cycle
▪ Nitrogen is an essential constituent of protein, DNA, RNA, and chlorophyll.

▪ Nitrogen is the most abundant gas in the atmosphere(78%). But atmospheric N2 has
limited availability for biological use, and this form is relatively nonreactive and
unusable by plants.

▪ Nitrogen is present in environment in a wide variety of chemical forms including organic

nitrogen, ammonium (NH4+), nitrite (NO2-), nitrate (NO3-), nitrous oxide (N2O) or nitric
oxide (NO).

▪ Nitrogen cycle consist of various steps namely nitrogen-fixation, ammonification,

nitrification, denitrification.

▪ The conversion of elementary or atmospheric nitrogen to its compound for the use of
living organism is called fixation of nitrogen.

▪ The blue green algae can fix atmospheric nitrogen as ammonium ion (ammonification).

▪ Some soil micro-organisms break down these nitrogen compounds to nitrogen in the soil
(denitrification).
AMMONIFICATION
 Ecological Niche
An ecological niche is the role and position a species has in its environment; how it meets its
needs for food and shelter, how it survives, and how it reproduces. A species' niche includes all
of its interactions with the biotic and abiotic factors of its environment.

✓ Habitat is used to denote the place where an organism’s population lives, like a pond is
habitat of zooplankton and fish.
✓ Niche is the role or job of a species in a habitat. The word niche comes from the French
word nicher, which means “to nest.” An ecological niche describes how a species interacts
with, and lives in, its habitat.
 Ecological Factor
In ecology, Ecological factors are variables in the environment that impact on organisms and
contribute to their characteristic modes of behavior. They are factors that affect dynamic
change in a population or species in a given ecology or environment.

1. Climatic Factors:
➢ Sunlight
➢ Temperature
➢ Rainfall
➢ Wind
➢ Humidity
➢ Atmospheric gases
➢ pH
2. Topographic Factors:
➢ Altitude
➢ Slope
➢ Direction of mountain chains & valleys
3. Edaphic Factors:
➢ Structure of Soils
➢ Formation of Soils
➢ Characteristic of Soils
4. Biotic Factors: producer, consumer, decomposer
5. Limiting Factors
 Limiting Factors
A limiting factor is a resource or environmental condition which limits the growth,
distribution or abundance of an organism or population within an ecosystem. These can
be either physical or biological factors. These can be identified through a response of
increased/ decreased growth, abundance, or distribution of a population, when the
factor is changed.

Types of Limiting Factor

Density Dependent Factors: are those factors whose effect on a population is
determined by the total size of the population. As an example, disease is likely to
spread quicker through a larger, denser population, impacting the number of individuals
within the population more than it would in a smaller, more widely dispersed
population.

Density Independent Factors: is one whose effect is not dependent on the size of the
population. Examples include environmentally stressful events such as earthquakes,
tsunamis, and volcanic eruptions. Density independent factors will usually kill all
members of a population, regardless of the population size.
Liebig’s Law of Minimum:
An organism requires minimum quantity of a particular nutrient for its proper growth and
if it is depicted below the critical minimum level, the organism will fail to grow or will
grow abnormally. If a pond is deficient in phosphorous, it will make the other nutrients
inactive and the proper growth of fish will get restricted.

Blackman’s Law of Limiting Factor:

A biological process is controlled by a number of factors and the deficiency of any of these
factors will affect the process on the whole. Photosynthesis is dependent on right amount
of water, CO2, chlorophyll, sunlight etc. A deficiency of any of these factors will affect the
rate of photosynthesis.

Shelford’s Law of Tolerance:

It is not only the minimum amount of a material can be limiting factor, but also the excess
amount of the same material can be limiting to the growth and development of an
organism. All the soil nutrients are equally important for the growth and development of
plants, anything in excess might limit the uptake of other nutrients, restricting the proper
growth.

Zone of tolerance:
Every organism has an ecological minimum and maximum for every factor and the range
between the two limits is known as zone of tolerance.
 Biodiversity and its conservation
Bio= living
Diversity = variety
Biodiversity is the variety and number of living organisms present
on Earth and the essential interdependence of all living things

At the 1992 Convention on Biodiversity held in Rio de Janeiro, It was

defined as -The variability among living organisms from all sources
including inter alia, terrestrial, marine & other aquatic ecosystems and
ecological complexes of which they are part of.
3 Components of Biodiversity

Diversity of genes
Chihuahuas, beagles, and rottweilers
are all the same species —but they're
not the same because there is variety in
their genes within the same species.
Chihuahua Beagle
Diversity of number of species
Monkeys, dragonflies, and meadow
beauties are all different species.
Represents variety and number of
species & their abundance in a
particular ecosystem.
Saki Monkey Meadow Beauty
Diversity of ecosystems
A broader scale of biodiversity in complex systems depicts the differences in
physical, ecological, food web, nutrient cycling etc.
Lakes, Ponds, and Rivers are all Freshwater Ecosystems. Rocky coast, Sand Dune,
Estuary, Salt Marsh , Coral Reef are all Marine Ecosystems.
 Hotspots of Biodiversity
British ecologist Norman Myers introduced this term. Certain ecosystems despite
their small size account for a high percentage of global biodiversity. These areas are
threatened by human activities. More than 1 billion people most whom are
desperately poor people, live in these areas. Measures protecting these areas should
be planned.
A biodiversity hotspot is a biogeographic region with a significant reservoir
of biodiversity that is under threat from humans.
Areas which exhibit high species richness as well as endemism are termed as
Hotspots of Biodiversity. A total of 34 Hotspots are identified out of which 3 are in
India.
CATEGORY
International Union for conservation of nature and Natural Resources (IUCN) has
categorized wild life into 8 categories as given in RED DATA BOOK. These are
Extinct, Extinct in the wild, critically endangered, endangered, vulnerable/threatened,
Near Threatened , conservation dependent, least concern.
EXTINCT (EX)
If there is no reasonable doubt that the last individual has died. No reasonable record for last 50
years. e.g Indian Cheetah
EXTINCT IN THE WILD (EW)
If there is known only to survive in cultivation, in captivity or as a naturalized population well
outside the past range. e.g Black soft-shell turtle (extinct in the wild since 2002)
CRITICALLY ENDANGERED (CR)
This includes species, which are facing an extremely high risk of extinction in the wild in the
immediate future. The population of such species is very low and the threats to its habitats are
very high. E.g. Asiatic Lion.
ENDANGERED (EN)
It includes species that are not critically endangered but are in danger of extinction if the threats
to its survival continue operating. Also, species whose numbers have been reduced to a critical
level or whose habitats have been so drastically reduced are deemed to be in immediate danger
of extinction. E.g. Tiger.
VULNERABLE (VU)
It includes species that are not endangered but are likely to move into the endangered category in
the near future if the threats to its survival continue operating. E.g. Giant Clam.
NEAR THREATENED (NT)
Species is Near Threatened when it has been evaluated against the criteria but does not qualify for
Critically Endangered, Endangered or Vulnerable now, but is close to qualifying for or is
likely to qualify for one of these categories in the near future. E.g. Nicobar pigeon.
Endemic Species:
Species that have very restricted distribution and are found over relatively small ranges are
called endemic species. Since their ecological requirements are met over a small area, these
species remain restricted to a particular area as endemic species. Organisms that are indigenous
to a place are not endemic to it if they are also found elsewhere.
Greater one-horned Rhinoceros, Royal Bengal Tigers.
 Biodiversity Conservation

Considering the rich diversity and the threats

Aim is protection, preservation or restoration of natural resources.
2 major approaches
In-situ conservation (at the place)
Ex-situ conservation (out of the place)
In-situ conservation: The natural process and their interaction with
the habitat as well as all the elements of biodiversity are conserved.
National park, sanctuaries .

Ex-situ conservation: When the endangered species need special care,

they are removed from the area and kept under total human supervision
in places such as zoos, botanical gardens etc.
 Protected Areas
Protected areas are locations which receive protection because of their recognized
natural, ecological and/or cultural values.
• A National Park is an area where the natural or historical objects of national
significance are protected along with the wildlife therein, in such manner as will leave them
unimpaired for the enjoyment of future generations.
• Such protected areas are created by Central Legislation and enjoy highest level of legal
protection. The human activity is confined to management duties and controlled tourism,
strictly enforced by law.
A Wildlife Sanctuary is a place where some rare, wild, indigenous mammals, birds,
reptiles and any other form of wildlife are found in good numbers and represents a region that
needs protection together with the natural environment.
The State Forest Department creates such protected areas. The Chief Wildlife Warden
monitors human activities such as livestock grazing, collection of forest produce and tourism,
within the sanctuary’s precincts.
Biosphere reserves are areas of terrestrial and coastal ecosystems promoting solutions to
reconcile the conservation of biodiversity with its sustainable use. They are internationally
recognized, nominated by national governments and remain under sovereign jurisdiction of
the states where they are located.
Tiger reserves are operated by state forestry departments “to ensure maintenance of viable
populations of Bengal tigers in India. The tigers are preserved for all time as a national
heritage for the benefit, education and enjoyment of the people”.