Lecture-1---Basics-of-Ecology---class-Notes

Environment
● The environment is defined as ‘the sum total of living, non-living
components; influences and events, surrounding an organism.

What is Ecology?
● The study of the interactions between living organisms and their biotic
and abiotic environments.
● Therefore, It is the study of the relationship of plants and animals to their
physical and biological environment.

Levels of Organisations In Ecology
● Organism is an individual living being that has the ability to act or function
independently. It may be plant, animal, bacterium, fungi, etc.
● Population is a group of organisms usually of the same species, occupying
a defined area during a specific time.
● Community refers to all the populations of different species living and
interacting in a particular area or habitat. A community may consist of
different species of plants, animals, fungi, and microorganisms, which are
interdependent and affect each other's survival and well-being.

Levels of Organisations In Ecology

Levels of Organisations In Ecology: ECOSYSTEM
● An ecosystem is defined as a structural and functional unit of biosphere
consisting of community of living beings and the physical environment,
both interacting and exchanging materials between them.
● The term "ecosystem" was first coined by British ecologist Arthur Tansley
in 1935.

Levels of Organisations In Ecology: ECOSYSTEM

Functional Units of an Ecosystem
● Productivity: It refers to the rate of biomass production.
● Energy flow: It is the sequential process through which energy flows from
one trophic level to another. The energy captured from the sun flows from
producers to consumers and then to decomposers and finally back to the
environment.
● Decomposition – It is the process of breakdown of dead organic material.
The top-soil is the major site for decomposition.
● Nutrient cycling – In an ecosystem nutrients are consumed and recycled
back in various forms for the utilisation by various organisms.

● "Biotic" and "organic" are not synonymous: Whether derived
directly or indirectly from plants and animals, organic compounds
are biomolecules with at least one carbon-hydrogen bond, such as
proteins, lipids, carbohydrates, and nucleic acids. Mineral-derived
compounds are referred to as inorganic compounds because they
usually don't contain carbon-hydrogen (C-H) bonds.
Biotic and Organic

Biome
● A biome refers to a large geographical region characterized by a
particular set of climate conditions, plant and animal life.
● Each biome has unique characteristics that determine the kinds of
plants and animals that can survive and thrive in that particular
environment.
● Types of biomes: forests, grasslands, tundra, deserts, and aquatic
biomes such as oceans, rivers, and lakes.
● You must read this from GC leong.

BIOSPHERE
● Biosphere is a part of the earth where life can exist.
● It represents a highly integrated and interacting zone comprising
atmosphere (air), hydrosphere (water) and lithosphere (land).
● Biosphere is approximately 20 km thick. Most life occurs between 500m
below the surface of the ocean and about 6 km above the sea level.

HABITAT
● It is the place where an organism or a community of organisms lives,
including all living and nonliving factors or conditions of the surrounding
environment.
● Microhabitat is a term for the conditions and organisms in the immediate
vicinity of a plant or animal.

Habitat vs Environment
● A habitat is always alive, while an environment may not
be.
● All habitats are environments, but not all environments
qualify as habitats.
● A habitat caters to a specific species, whereas an
environment can support multiple species, potentially
leading to various habitats.

● An ecosystem (has life in it) is a functional unit of
nature or environment.
● A habitat is a part of the ecosystem.
● An environment (may or may not have life) is a group
of ecosystems. (All ecosystems are environments, but
not vice versa)
● Ecology is the study of interactions between
organisms and the surroundings in an ecosystem
Ecosystem vs Environment vs Ecology

NICHE
● Niche refers to the unique role or position of a species within an
ecosystem, including the physical and biological conditions it requires to
survive and reproduce.
● It can be described by the specific set of environmental conditions, such
as temperature, humidity, light, soil type, and food availability, that a
species requires to survive and thrive.
● The niche of an organism and its interactions is determined by where it
stands in the ecological structure of the ecosystem. (Producers,
Consumers, Decomposers)

Habitat and Niche
● Habitat : Physical Space occupied by an organism.
● Niche : Functional Space occupied by an organism where it gets the
resources needed to survive.

Niche : Types (Based on the interactions of species)
● Based on the interactions of species, niche are of 3 types :
○ Habitat niche : physical area in the the habitat that a species occupies.
○ Trophic Niche : Trophic level occupiped by the species in the food chain
/ ecological chain.
○ Multidimensional Niche : Fundamental Niche and Limiting factors.
○ Fundamental Niche : where an organism could exist without ecological
interactions.
○ Realised niche : population exists here in the presence of interactions
and competition.

● Habitat niche — where it lives
● Food niche — what it eats or decomposes and what species it
competes with
● Reproductive niche — how and when it reproduces
● Physical and chemical niche — temperature, land shape, land
slope, humidity and other requirements.
Niche Types : Functional

NICHE OVERLAP
● If 2 organisms have the same niche : there is increased competition,
leading to less chances of survival.
● Gauss Law : Competitive exclusion principle : Competition in case of the
same niche of 2 species will lead to the exclusion of 1 from that niche.
● Darwin’s finches and galapagos islands.

NICHE OVERLAP
● Niche overlap describes the situation in which co-occurring species share
parts of their niche space with each other.
● Overlapping niches may lead to Competitive Exclusion.
○ Competitive Exclusion: Two species which compete for the same
limited resource cannot coexist at constant population values.
● Niche overlap is reduced by resource partitioning.
○ Resource partitioning is the process of moving things around in
order to satisfy the niche size to an appropriate level.

NICHE OVERLAP : competitive exclusion

NICHE OVERLAP : Resource Partitioning

ECOTONE
Ecotone is a zone of junction between two or more diverse ecosystems.
● Such areas have richness in biodiversity due to edge effect.
Examples of ecotones include:
● Marshlands: Dry and wet ecosystems
● Mangrove forests: Terrestrial and marine ecosystems
● Grasslands: Desert and forest, and
● Estuaries: Saltwater and freshwater

Characteristics of Ecotone
● It is a zone of tension
● It is linear as it shows progressive increase in species composition of one
in coming community and a simultaneous decrease in species of the other
outgoing adjoining community.
● A well-developed ecotone contains some organisms which are entirely
different from that of the adjoining communities.

Examples of Ecotone
● Coral Reefs (we will see this in detail later) : Marine Animals that release
limestone (Calcium carbonate). This limestone in the marine environment
of the sea lead to edge effect and ecotone presence.
● Wetlands : submerged with water. Midway between land and lakes,
therefore have much higher biodiversity. (Ramsar convention : we will see
later in detail)

Edge Effect
● Edge effect refers to the changes in population or community structures
that occur at the boundary of two habitats.
● Sometimes the number of species and the population density of some of
the species in the ecotone is much greater than either community. This is
called the edge effect.
● Species adapted to survive in edge effect areas are called ecotypes.

Ecocline
An ecocline is a gradual transition between two ecosystems, where
environmental conditions change progressively, leading to a continuous
variation in species composition.
Key Difference:
Ecocline: Gradual transition, no sharp boundary (e.g., altitudinal gradient
in mountains).
Ecotone: Sharp boundary, often with unique species (e.g., mangrove
forests between land and sea).

Ecocline
Types:
● Altitudinal Ecocline – Changes in vegetation and species composition
along a mountain slope (e.g., tropical forest → temperate forest →
alpine tundra).
● Latitudinal Ecocline – Gradual change in ecosystems from the equator
to the poles (e.g., tropical rainforest → temperate forest → tundra).
● Salinity Ecocline – Transition from freshwater to saltwater in an
estuary (e.g., river mouth to open sea).
● Moisture Ecocline – Variation in plant types along a rainfall gradient
(e.g., rainforest → savanna → desert).
● Temperature Ecocline – Change in marine species composition from
warm tropical waters to cold polar waters.

ECOTYPE
● An Ecotype is a population of species that differs genetically from other
populations of the same species because local conditions have selected
for certain unique physiological or morphological characteristics.
● Ecotypes are adapted to survive in an ecotone.
● Ex : Royal Bengal Tiger : adapted to mangrove, can drink salt water.
● Examples: Kharai Camel (Gujarat), Indian Rhino

TROPHIC LEVEL
● A trophic level is the representation of energy flow in an ecosystem.
● It is the position it occupies in a food chain.
● It deals with how the members of an ecosystem are connected based on
nutritional needs.
● The trophic level interaction involves three concepts:
○ Food Chain
○ Food Web
○ Ecological Pyramids

Energy in the ecosystem
● Plants absorb less that 1% of the sunlight that reaches them.
● Photosynthetic organisms make 170 billion metric tons of food each year.
● 2 processes : photosynthesis and respiration.

PRIMARY PRODUCERS (AUTOTROPHS)
● Word Breakdown : Auto-trophs
● Primary producers are basically green plants (and certain bacteria and algae).
● They synthesise carbohydrates from simple inorganic raw materials like carbon
dioxide and water in the presence of sunlight by the process of photosynthesis
for themselves, and supply indirectly to other non-producers.
● In terrestrial ecosystem, producers are basically herbaceous and woody plants,
while in aquatic ecosystem producers are various species of microscopic algae.

● Producers : Phototrophs or chemotrophs
● Phototrophs : organisms that perform photosynthesis and contain chlorophyll :
Carbon dioxide + water + sunlight = sugar + oxygen
● Chemotrophs : do certain chemical reactions to obtain their food.
● Ex : Sulphur bacteria like thiobascillus.
● Carbon dioxide + water + hydrogen sulphide + oxygen = Carbohydrates +
sulphuric acid.

CONSUMERS : Hetero- trophs
● Consumers are incapable of producing their own food (photosynthesis).
● They depend on organic food derived from plants, animals or both.
● Consumers can be divided into two broad groups namely micro and
macro consumers.

MACRO CONSUMERS
● They feed on plants or animals or both and are categorised on the basis of their
food sources.
● Herbivores are primary consumers which feed mainly on plants e.g. cow, rabbit.
● Secondary consumers feed on primary consumers e.g. wolves.
● Carnivores which feed on secondary consumers are called tertiary consumers e.g.
lions which can eat wolves.
● Omnivores are organisms which consume both plants and animals e.g. man,
monkey.
● Scavengers : feed on dead and decaying organisms

Scavengers
● Scavengers feed on carrion (dead or injured animal corpses)
● Scavengers will feed on these dead plants / animals and decomposers will finish
the job.

MICRO CONSUMERS
● They are bacteria and fungi which obtain energy and nutrients by decomposing
dead organic substances (detritus) of plant and animal origin.
● They feed on small microscopic bits of dead organic matter and convert them into
inorganic nutrients.
● The products of decomposition such as inorganic nutrients which are released in
the ecosystem are reused by producers and thus recycled.
● Earthworm and certain soil organisms (such as nematodes, and arthropods) are
detritus feeders and help in the decomposition.

Example of Aquatic Ecosystem
● Producers in aquatic ecosystems : blue green algae (cyanobacteria),
phytoplankton, diatoms.
● Primary consumers : crustaceans, zooplankton, small fish
● Secondary Consumers : Herrings, bigger fish, sharks etc.

FOOD CHAIN
● A sequence of organisms that feed on one another, form a food chain.
● It is the process of transfer of food energy from green plants
(producers) through a series of organisms with repeated eating and
being eaten link.
● Arrows in a food chain represent the flow of energy, through the
process of eating.
● Linear: Unidimensional Flow of Energy

FOOD WEB
● A food web is a diagram or model that illustrates the
interdependence of various organisms in an ecosystem, showing the
flow of energy and nutrients from one organism to another.
● It is a representation of the feeding relationships among different
species in an ecosystem.
● Non Linear: Multi dimensional Flow of Energy
● Complexity : More the number of species, greater the interactions
and more complex the food web. These food webs are more stable.
WHY?

FOOD WEB COLLAPSE
● A food web collapse occurs when the interconnected food chain of
an ecosystem breakdown or fail to function in a sustainable
manner.
● This can happen due to a number of factors such as changes in
climate, loss of key species, pollution and overexploitation by
humans.
● A food web collapse can have serious consequences on the entire
ecosystem, including loss of biodiversity, reduced productivity, and
even ecosystem collapse.

ECOLOGICAL PYRAMIDS
● Ecological pyramids are graphical representations of the trophic
levels within an ecosystem.
● They show the relative abundance or biomass of different groups
of organisms at each trophic level in an ecosystem, and the flow of
energy and nutrients through the food chain.

Law of 10% : given by Raymond Lindeman
● From one trophic level to another, only biomass will get transferred.
However, not all the energy obtained by an organism will get
converted to biomass.
● When all energy losses are added, only about 10% of the energy
entering one trophic level is available to the next trophic level;
because only 10% of the energy obtained is used to make biomass.
This is known as the 10% law.

Law of 10% : given by raymond lindeman
● Because of the 10% law, foodchains have five or less links. Because 90% of energy
is lost at each level, the amount of energy available decreases very quickly.
● Most of the energy loss is in production of heat energy and movement from one
place to the other.

Law of 10% : given by raymond lindeman

ECOLOGICAL PYRAMIDS
● Ecological pyramids are graphical representations of the trophic
levels within an ecosystem.
● They show the relative abundance or biomass of different groups of
organisms at each trophic level in an ecosystem, and the flow of
energy and nutrients through the food chain.

PYRAMID OF ENERGY
● The pyramid of energy is a graphical representation of the flow of
energy through an ecosystem.
● It is always upright.
● As you move up the pyramid, there is less energy available because
some is lost in each transfer. (10% Rule)
● This loss of energy is due to the laws of thermodynamics.

RELEVANCE OF PYRAMID OF ENERGY
● The food pyramid represents the flow of energy in an ecosystem.
● It illustrates the amount of energy that is transferred from one
trophic level to another in an ecosystem.
● The pyramid helps us understand the importance of primary
producers and the limits of energy transfer in an ecosystem.
● It is a simple way to visualize the complex interactions between
organisms and energy in an ecosystem.

PYRAMID OF BIOMASS
● The pyramid of biomass is a graphical representation of the amount
of living organic matter, or biomass, present in each trophic level of
an ecosystem.
● It represents the relative amount of biomass at each level, with the
largest biomass at the base of the pyramid and successively smaller
biomass at each higher level.
● It is not always a perfect pyramid shape, as it can be affected by
factors such as the size and turnover rate of the organisms in each
trophic level.

Aquatic pyramid of biomass
● Phytoplankton (2-3 days)
● Zooplankton (7-8 days)
● Small fish (15-20 days)
● Shark (10 years)
● At one particular amount of time, the biomass at the lower trophic
levels are lower than that of higher trophic levels. Hence, there is an
inverted biomass pyramid.

PYRAMIDS OF NUMBER
● This pyramid shows the number of organisms at each trophic level
in the food chain.
● It indicates the number of individuals at each trophic level, and is
often shaped like a true pyramid, with the largest number of
organisms at the base and decreasing numbers as you move up the
pyramid.
● However, there can be certain exceptions when it is not shaped like
a true pyramid.

BIOACCUMULATION
● Bioaccumulation is the gradual accumulation of substances, such as pesticides
or other chemicals, in an organism.
● It occurs when an organism absorbs a substance at a rate faster than that at
which the substance is lost or eliminated by catabolism and excretion.

Accumulation in Food Chain (Down to Earth)
● Microplastics are getting into mosquitoes and contaminating
new food chains
● According to a research, there was evidence of beads in all the
life stages of Mosquitoes, although the numbers went down as
the animals developed.
● Any flying insect that spends part of its life in water can
become a carrier of plastic pollution thus resulting in
Biomagnification at higher trophics.

Accumulation in Food Chain (Down to Earth)

Biomagnification vs Bioaccumulation
● Bioaccumulation takes place in a single organism over the span of its life,
resulting in a higher concentration in older individuals. Biomagnification takes
place as chemicals transfer from lower trophic levels to higher trophic levels
within a food web, resulting in a higher concentration in apex predators.
● When DDT enters aquatic bodies, it gets build up in the body of fishes and this is
known as bioaccumulation. When fishes are eaten by animals of higher trophic
levels, concentration of DDT is increased at each successive trophic level and
this is known as biomagnification.

BIOMAGNIFICATION
● Biomagnification, also known as bioamplification or biological
magnification, is the increase in concentration of a substance, e.g a
pesticide, in the tissues of organisms at successively higher levels in a
food chain.
● This increase can occur as a result of:
● Persistence – where the substance cannot be broken down by
environmental processes
● Food chain energetics – where the substance's concentration increases
progressively as it moves up a food chain
● Low or non-existent rate of internal degradation or excretion of the
substance – mainly due to water-insolubility

SUBSTANCES THAT BIOMAGNIFY
● In order for biomagnifcation to occur, the pollutant must be:
long-lived, mobile, soluble in fats, non biodegradable
● Examples of Substances:
○ Chlorinated hydrocarbons (Organochlorines)
○ Inorganic compounds like methylmercury or heavy metals
○ Persistent organic pollutants

Examples of Biomagnification
● DDT : used to kill mosquitoes, added up in bald eagle
populations leading to their egg shells being crushed. This was
written about by Rachel Carson in her book the silent spring.
● It rained cats in borneo! : explained in class.
● Minamata Disease : Mercury bioaccumulation in shellfish in
minamata bay, eaten by the local populace leading to mercury
poisoning.
● Diclofenac and the indian vulture crisis.

Biomagnification in Vultures
● Traces of diclofenac and its derivative compounds have been
found in the carcasses of vultures across India and its neighboring
countries, and it is known that the biomagnification of diclofenac
from the consumption of infected domestic animal carcasses
contributes to vulture mortality.

BIOTIC INTERACTIONS
● Biotic interactions are the
interactions between different living
organisms in an ecosystem.
● These interactions can be positive,
negative, or neutral, and they can
affect the distribution and
abundance of species, the structure
of communities, and the functioning
of ecosystems.

MUTUALISM
● It is the type of interaction where both species benefit from the
interaction.
● It highlights the interdependence of species in an ecosystem. By
working together, species can enhance their chances of survival
and reproduction, and help to maintain the balance of the
ecosystem.

● Mutualism
● Ants and aphids: Ants "farm" aphids by protecting them from
predators and moving them to new food sources. In return, the
aphids secrete a sweet substance called honeydew that the ants
eat.
● Pollination: Bees, butterflies, and other insects feed on the nectar
and pollen of flowers. In the process, they transfer pollen from
one flower to another, aiding in plant reproduction.
EXAMPLES OF MUTUALISM

● Ant–Fungus Mutualism
○ Especially seen in leafcutter ants (Atta and Acromyrmex
genera) and a specific fungus (Leucoagaricus gongylophorus).
○ Both the ant and the fungus are dependent on each other for
survival — they cannot live independently.

● Leafcutter ants collect leaves, not to eat, but to cultivate a specific fungus
(Leucoagaricus gongylophorus).
● Ants chew leaves into pulp and grow the fungus on it in underground
nests.
● The fungus breaks down the plant matter and produces gongylidia, which
the ants eat.
● Ants protect and maintain the fungal garden, removing unwanted fungi
and pests.
● They also host bacteria on their bodies that secrete antibiotics to protect
the fungus.

SYMBIOSIS
● Symbiosis is a type of biotic interaction in which two or more
different species live in close association with each other.
● The term "symbiosis" was coined by Anton de Bary in 1879 and is
derived from the Greek words "syn" (together) and "biosis" (living).
● Symbiosis can take many different forms, and not all symbiotic
relationships are mutualistic.
● Some symbiotic relationships are parasitic, in which one species
benefits at the expense of the other, while others are commensal,
in which one species benefits without affecting the other.

EXAMPLES OF BIOTIC INTERACTIONS
● Symbiosis
● Mycorrhizae: These are symbiotic associations between fungi and the roots of
plants. The fungi help the plants absorb nutrients from the soil, while the
plants provide the fungi with carbohydrates.
● Coral and zooxanthellae: Coral reefs are formed by the symbiotic relationship
between corals and a type of algae called zooxanthellae. The algae provide
the coral with food through photosynthesis, while the coral provides the algae
with a protective environment and access to sunlight.

PROTO COOPERATION
● Proto-cooperation is a type of interaction between two species that
is not yet fully mutualistic but represents the early stages of
mutualism.
● In proto-cooperation, two or more species interact in a way that
benefits both, but the relationship is not yet fully dependent on
each other.
● Over time, the relationship may evolve into a more symbiotic and
mutualistic one.

PROTO COOPERATION
● In it, Interaction is temporary. Once, the
interacting organisms get the advantage,
they separate.
● Survival is not an issue.
● Example: Plants and pollinators.
● The pollinators may feed on the nectar of the
plants, but they also inadvertently transfer
pollen from one plant to another, benefiting
the plants' reproductive success.

● Proto-Cooperation :
● Lions and hyenas: Although lions and hyenas are usually considered to be
enemies, they will sometimes cooperate to steal a kill from another predator.
This allows both species to benefit from the shared food source.
● Birds and grazing animals: Some species of birds will follow grazing animals,
such as cattle or bison, to feed on insects that are disturbed by the animal's
movement. This benefits both the birds, who get access to a food source, and
the grazing animals, who get rid of insects that can harm their skin or eyes.

COMMENSALISM
● This defines the interaction in which two or more species are mutually
associated in activities centering on food and one species at least,
derives benefit from the association while the other associates are
neither benefited nor harmed.

● Commensalism:
● Barnacles and whales: Barnacles are marine crustaceans that
attach themselves to the skin of whales. They benefit from the
movement of the whale, which helps them obtain food, while
the whale is not significantly affected by their presence.
● Epiphytes and trees: Epiphytes are plants that grow on other
plants, such as trees. They benefit from the structure of the tree,
which provides support and access to sunlight, while the tree is
not significantly affected by their presence.

PREDATION
● It is a form of interaction, where one animal kills another animal for
food.
● Specialized predators are those adapted to hunt only a few specific
species.
● Lion and deer exhibit predator – prey relationship, where the Lion is
the predator and the deer is the prey.
● This type of interaction helps in the transfer of energy up the trophic
levels and is an essential strategy in population regulation.

PARASITISM
● It is a kind of harmful interaction between two
species, wherein one species is the ‘parasite’ and
the other its ‘host’.
● The parasite benefits at the expense of the host.
● A parasite derives shelter, food and protection from
the host.
● Parasites exhibit adaptations to exploit their hosts.

PARASITISM
● The parasites may be:
○ viral parasites (plant/ animal viruses),
○ microbial parasites (e.g., bacteria / protozoa / fungi),
○ phyto parasites (plant parasites)
○ zooparasites (animal parasites such as Platyhelminthes,
nematodes, arthropods).
● Parasites may inhibit or attach to the surface of the host (Ectoparasites
- Head lice, Leech) or live within the body of the host (endoparasites –
ascaris, tapeworm).

● Parasitism:
● Ticks and mammals: Ticks are blood-sucking parasites that feed on the blood
of mammals, such as deer and humans. They benefit from the host's blood,
while the host can be harmed by the loss of blood and potential transmission
of diseases.
● Dodder and plants: Dodder is a parasitic plant that attaches itself to other
plants and steals nutrients and water from them. It benefits from the host's
resources, while the host can be harmed by the loss of nutrients and potential
damage to its tissues.

COMPETITION
● It refers to the type of interaction in which individuals of a species or
members of different species vie for limited availability of food, water,
nesting space, cover, mates or other resources.
● When resources are in more than adequate to meet the demands of
the organisms seeking them, competition does not occur, but when
inadequate to satisfy the need of the organisms seeking them, the
weakest, least adapted, or least aggressive individuals are often forced
to face challenges.

INTERSPECIFIC COMPETITION
● Interspecific competition is a type of interaction in which two or more
species compete for a limited resource, such as food, water, or habitat.
● This competition occurs between different species that share the same
resource requirements.
● For example, lions and hyenas may compete for access to prey species,
or two species of trees may compete for sunlight and nutrients.

EXAMPLES OF COMPETITION
● Competition:
● Lions and hyenas: Lions and hyenas both hunt and scavenge for food in the
same areas. As they compete for the same resources, they can engage in
fierce competition.
● Trees in a forest: Trees in a forest often compete for light, water, and
nutrients. As they grow taller, they can shade out and deprive other trees of
sunlight and nutrients.

INTRASPECIFIC COMPETITION
● Intraspecific competition, on the other hand,
is a type of interaction in which individuals of
the same species compete for resources.
● This competition occurs within a species, and
it can be intense, especially when resources
are scarce.
● For example, plants may compete for water
and nutrients in the soil, or animals may
compete for mates or nesting sites.

AMENSALISM
● This is the ecological interaction in which an individual species harm
another without obtaining benefit.
● In amensalism, the species that is negatively affected is often referred to
as the "victim" species.
● The negative effect can occur in several ways, such as through the
release of chemicals or other substances that are toxic or inhibitory to
the victim species, or through physical interference with the victim's
ability to access resources.
● Example: A large tree shades a small plant, retarding the growth of the
small plant. The small plant has no effect on the large tree.

● Amensalism:
● Black walnut trees and other plants: Black walnut trees release a chemical
called juglone that inhibits the growth of other plants growing near them. This
inhibitory effect is an example of amensalism.
● Antibiotic-producing bacteria and non-producing bacteria: Some bacteria
produce antibiotics that inhibit the growth of other bacteria in the same
environment. This inhibition can be considered an example of amensalism.

Test of 10 Questions!
Cut off : 6/8

Q.) Which one of the following is the best description of the term 'ecosystem'?
(a) A community of organisms interacting with one another
(b) That part of the Earth which is inhabited by living organisms
(c) A community of organisms together with the environment in which they live
(d) The flora and fauna of a geographical area
Q.1 (2015)

Q.) Which one of the following terms describes not only the physical space
occupied by an organism, but also its functional role in the community of
organisms?
(a) Ecotone
(b) Ecological niche
(c) Habitat
(d) Home range
Q.2 (2013)

Q.) Which one of the following is the correct sequence of a food chain?
(a) Diatoms-Crustaceans-Herrings
(b) Crustaceans-Diatoms-Herrings
(c) Diatoms-Herrings-Crustaceans
(d) Crustaceans-Herrings-Diatoms
Q.3 (2014)

Q.) With reference to food chains in ecosystems, consider the following statements
1. A food chain illustrates the order in which a chain of organisms feed upon each
other.
2. Food chains are found within the populations of a species.
3. A food chain illustrates the numbers of each organism which are eaten by
others.
Which of the statements given above is / are correct?
(a) 1 only (b) 1 and 2 only
(c) 1, 2 and 3 (d) None
Q.4 (2013)

Q.) With reference to the food chains in ecosystems, which of the following kinds
of organism is / are known as decomposer organism/organisms?
1. Virus
2. Fungi
3. Bacteria
Select the correct answer using the codes given below.
(a) 1 only
(b) 2 and 3 only
(c) 1 and 3 only
(d) 1, 2 and 3
Q.5 (2013)

Q.) Which of the following are detritivores?
1. Earthworms
2. Jellyfish
3. Millipedes
3. Seahorse
4. Woodlice
Select the correct answer using the code given below
(a) 1, 2 and 4 only (b) 2, 3, 4 and 4 only
(c) 1, 3 and 5 only (d) 1, 2, 3, 4 and 5
Q.6 (2021)

Q.) Consider the following kinds of organisms:
1. Copepods
2. Cyanobacteria
3. Diatoms
4. Foraminifera
Which of the above are primary producers in the food chains of oceans?
A. 1 and 2
B. 2 and 3
C. 3 and 4
D. 1 and 4
Q.7 (2021)

Q.) Which of the following have species that can establish symbiotic relationship
with other organisms?
1. Cnidarians
2. Fungi
3. Protozoa
Select the correct answer using the code given below.
A. 1 and 2 only
B. 2 and 3 only
C. 1 and 3 only
D. 1, 2 and 3
Q.8 (2021)

Congratulations on giving the test!
Let’s Discuss The Answers.

Answer: C
● The term ‘Ecosystem’ was first used by A G Tansley in 1935 who defined an
ecosystem as ‘a particular category of physical systems, consisting of
organisms and inorganic components in a relatively stable equilibrium,
open and of various sizes and kinds’.
● Thus the ecosystem includes both the organisms as well as their
environment.

Answer: B
● In ecology, a niche is a term describing the relational position of a species
or population in an ecosystem.
● More formally, the niche includes how a population responds to the
abundance of its resources and enemies (e. g., by growing when resources
are abundant, and predators, parasites and pathogens are scarce) and
how it affects those same factors (e. g., by reducing the abundance of
resources through consumption and contributing to the population
growth of enemies by falling prey to them).
● Gause’s competitive exclusion principle says that those species having
identical requirements cannot occupy the same ‘niche’ indefinitely.

Answer: A
● Diatoms are a major group of algae and are among the most common
types of phytoplankton, so primary producers/autotrophs.
● Crustaceans as consumers/heterotrophs while Herrings (a fish) feed on
Crustaceans.

Answer: A
● Food chain, in ecology, the sequence of transfers of matter and energy in
the form of food from organism to organism.
● Food chains are not found within the populations of ‘a’ species, because
technically, the food chain is the sequence of organisms through which the
energy flows.
● Food chains intertwine locally into a food web because most organisms
consume more than one type of animal or plant.

Answer: B
● Fungi and Bacteria are decomposers.
● They break down organic matter into simple inorganic substances.
● Virus represents dormant life. They are metabolically inactive as long as
they are outside a host body.
● They are not decomposers. They invade host cells and use their nucleus
(DNA machinery) to carry out their life processes.

Answer: C
● Detritivores are heterotrophs that obtain nutrients by consuming detritus.
● There are many kinds of invertebrates, vertebrates and plants that carry
out coprophagy.
● By doing so, all these detritivores contribute to decomposition and the
nutrient cycles.
● Earthworm, Millipedes and Woodlice are detritivores.

Answer: B
● Autotrophs or primary producers are organisms that acquire their
energy from sunlight and materials from non-living sources.
Copepods are a group of small crustaceans found in nearly every
freshwater and saltwater habitat. Copepods are major secondary
producers in the World Ocean.
● They represent an important link between phytoplankton,
microzooplankton and higher trophic levels such as fish. They are
an important source of food for many fish species but also a
significant producer of detritus. Hence, option 1 is not correct.

● Cyanobacteria, also called blue-green algae, are microscopic organisms found
naturally in all types of water. Cyanobacteria are important primary producers and
form a part of the phytoplankton. They may also form biofilms and mats (benthic
cyanobacteria). Hence option 2 is correct.
● Diatoms are photosynthesising algae, they have a siliceous skeleton (frustule) and
are found in almost every aquatic environment including fresh and marine waters.
Diatoms are one of the major primary producers in the ocean, responsible annually
for ~20% of photosynthetically fixed CO2 on Earth. Hence option 3 is correct.
● Foraminifera are single-celled organisms, members of a phylum or class of amoeboid
protists characterized by streaming granular ectoplasm for catching food and other
uses. Hence, option 4 is not correct.

Answer: D
● Cnidarian, also called coelenterate are mostly marine animals. They include the
corals, hydras, jellyfish, Portuguese men of-war, sea anemones, sea pens, sea
whips, and sea fans. The relationship between cnidarians and dinoflagellate algae is
termed as "symbiotic", because both the animal host and the algae are benefiting
from the association.
● It is a mutualistic interaction Fungi have several mutualistic relationships with other
organisms. In mutualism, both organisms benefit from the relationship. Two
common mutualistic relationships involving fungi are mycorrhiza and lichen.
● Termites have a mutualistic relationship with protozoa that live in the insect's gut.
The termite benefits from the ability of bacterial symbionts within the protozoa to
digest cellulose.

Lecture-1---Basics-of-Ecology---class-Notes

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