fundamentals of ecology and its importance

Environment can be defined as the natural surroundings of that organism which directly or indirectly influences the growth and development of the organism.

1. FUNDAMENTALS OF ECOLOGY

2. All living organisms have a specific surrounding
or medium with which they continuously
interact, from which they derive substance and to
which they are fully adopted. This surrounding is
generally called their environment.
It can be broadly defined as “the sum total of
physical, chemical and biological condition, which
surrounds an organism or a group of organism”.
The aggregate of all conditions affecting the
existence, growth, and welfare of an organism or
group of organisms is called environment.
In common usage, ‘the environment’ often
means the total global environment, without
reference to any particular organism.
What is environment?

3. Environment can be defined as the natural
surroundings of that organism which directly or
indirectly influences the growth and development of
the organism.
The word environment is derived from the French
word “environ”.
It is introduced into the subject by biologist Jacob
Van Erkul in the early 1900s.

4. CLASSIFICATION OF ENVIRONMENT
ENVIRONMENT
PHYSICAL
ENVIRONMENT
BIOLOGICAL
ENVIRONMENT
CULTURAL
ENVIRONMENT
ATMOSPHERE
HYDROSPHERE
LITHOSPHERE
FLORA
FAUNA
MICROBIA
SOCIETY
ECONOMY
POLITICS

5. ECOLOGY:
Was coined by a german biologist Ernst Haeckel in
1866.
Ecology is derived from the Greek word Oikos which
means “House” and logy means “study”.
The study of the relationships between biotic and
abiotic factors in environments.
Ecology or environmental biology is the scientific study of
interaction among organisms and the interaction of the
organisms with the environment.
 The scope of this field is very large and covers things
like global warming,
environmental pollution, plant and animal extinctionsetc.

6. Factors Influencing Environment:
The life of an organism is surrounded and effected
by a number of external forces. These forces are
known as environmental or ecological factors.
There are actually four categories of ecological
factors which affect the environment.
(a) Topographic or Physiographic factors: These
factors include altitude, direction of mountain
chains, plateaus, plains, lakes, rivers, sea level and
valleys etc.
(b) Climatic or Aerial factors: These include
atmosphere, light temperature, humidity, rainfall
etc.

7. (c) Edaphic factors: Edaphic factors which are related
to the structure and composition of soil including
its physical and chemical properties, like soil and its
types, soil profile, minerals, organic matter, soil
water, soil organisms. Inorganic substances like
water, carbon, sulphur, nitrogen, phosphorus and so
on. Organic substances like proteins, lipids,
carbohydrates, humic substances etc.
(d) Biotic factors: These include all types of
interactions between different forms of life. For
example, man, animals, plants, micro-organisms etc.
All these ecological factors operate in conjunctions
and not individually, affecting the life of organisms.

8. Levels of Ecological Organization:
Ecology consists of six main levels of organization:
1. Individual/Organisms:
An individual can be any living organism that has
the ability to function independently.
They make the basic unit of study in ecology.
The organisms of the similar type have the potential
for interbreeding, and produce fertile offspring,
which are called species.
It is a body made up of organs, organelles and other
parts that work together to carry out various
processes of life for e.g. a lion, an elephant, a tiger, a
wolf etc.

9. It has a definite life span including definite series of
stages like birth, hatching, growth, maturity,
senescence, aging and death.
Competition, mutualism, commensalism,
parasitism, and predation are various types of
interactions between organisms.
2. Population:
A population is a group of individuals of the same
species, inhabiting the same area, and functioning as
a unit of biotic community.
Populations of plants and animals in the ecosystem
do not function independently of each other.

10. They are always influencing each other and organizing
themselves into communities and have functional relationship
with their external environment for e.g., a pride of lions, a
herd of elephants, a school of fish, a flock of sheep etc.
Population growth rate is the percentage variation
between the numbers of individuals in a population at two
different times.
3. Community:
A community can be defined as the collection of different
species of population (both plant and animal species) in a
specific area at a given point of time.
This is an assemblage of populations of plants, animals,
bacteria and fungi that live in an area and interact with each
other.

11. Levels of organization in an ecosystem

12. These species can vary vastly in number and size.
E.g., grasses dominate a grassland community , though
it may contain herbs, shrubs, and trees along with
associated animals of different species.
Community is a higher ecological category next to
population.
4. Ecosystem:
An ecosystem is a community of living organisms in
conjunction with the non-living components of their
environment (things like air, water and mineral soil),
interacting as a system.
These biotic and abiotic components are regarded as linked
together through nutrient cycles and energy flows.

13. 5. Biome:
This is a large regional unit characterized by a major
vegetation type and associated fauna found in a specific
climate zone.
Biome is a group of ecosystems that have the same
clinical and similar dominant communities.
The biome includes all associated developing and
modified communities occurring within the same climatic
region, e.g., forest biomes, grassland and savanna
biomes, desert biome, etc.
6. Biosphere:
The entire inhabited part of the earth and its
atmosphere including the living components is called the
biosphere.

14. The term ‘Biosphere’ was given by geologist
Edward Suezz in 1875.
Biosphere represents a highly integrated and
interacting zone comprising of atmosphere (air),
hydrosphere (water), and lithosphere (land).
It is the narrow layer around the surface of the
earth.
Interaction of
Organisms

15. What is an Ecosystem?
The term ecosystem was coined by Sir Arthur
Tansley in 1935.
An ecosystem is a very complex unit with many
interactive components.
It can be defined as "a system of complex
interactions of populations between themselves
and with their environment" or as "the joint
functioning and interaction of these two
compartments (populations and environment) in a
functional unit of variable size”.
Ecosystems can be recognized as self- regulating
and self-sustaining units of landscape, e.g., a
pond or a forest.

16. Types of ecosystems

17. Natural ecosystem:
Natural ecosystems operate themselves under natural conditions. Based on
habitat types, it can be further classified into two types:
1.Terrestrial ecosystems -This ecosystem is related to land.
(Eg: grasslands, forests, desert ecosystems)
2.Aquatic ecosystem-This ecosystem is related to water. It is further sub-
classified into two types based on salt content.
a.Fresh water ecosystem :(i)Running/Flowing/Lotic water ecosystems- Examples:
Rivers, streams etc.(ii) Standing /Stagnant/Lentic water ecosystems -Examples :
Pond, lake etc.
b.Marine ecosystem -Example : Seas and sea shores
TYPES OF ECOSYSTEM

18. Man – made (or) Artificial ecosystems : Artificial ecosystem is operated (or)
maintained by man himself.
Example :Croplands, gardens , aquarium, park, kitchen garden
Function of an ecosystem :
To understand clearly the nature of ecosystem its functioning should be
thoroughly understood. The function of an ecosystem is to allow flow of energy
and cycling of nutrients.
Types of Functions: Functions of an ecosystem are of three types.
1. Primary function: The primary function of all ecosystem is manufacture of
starch (photosynthesis).
2. Secondary function: The secondary function of all ecosystem is distribution
of energy in the form of food to all consumers.

19. 3.Tertiary Function: All living systems die at a particular stage. These dead
systems are decomposed to initiate third function of ecosystems namely
“cycling”. Decomposers decompose them into simple materials like carbon
dioxide, water and minerals which go back to air, water bodies and soil from
where they were taken.
The functioning/importance of an ecosystems may be well understood by
studying the following terms.
•Energy and material flow.
•Food chains
•Food webs
•Food pyramids

20. Energy Flow In The Ecosystems:
Energy is the most essential requirement for all living organism. Solar energy is
the only source to our planet earth. Solar energy is transformed to chemical
energy in photosynthesis by the plants (called as primary producers).
Though a lot of sunlight falls on the green plants, only 1% of it is utilized for
photosynthesis. This is the most essential step to provide energy for all other
living organisms in the ecosystem.
Some amount of chemical energy is used by the plants for their growth and the
remaining is transferred to consumers by the process of eating.
Thus the energy enters the ecosystems through photosynthesis and passes
through the different tropic levels feeding levels.
The transfer of energy and matter takes place in the process of predator and
prey relationship in a food chain.

21. Energy flow and Thermodynamics:
The flow of energy through an ecosystem follows the two laws of
thermodynamics.
1. I law of thermodynamics: It states that “energy can be created nor
destroyed, but it can be transferred from one form to another”.
Example:Energy for an ecosystems comes from the sum. It is absorbed by
plants, herein it is converted into stored chemical energy i.e., solar energy is
converted into chemical energy.
2. II law of thermodynamics: It states that, “Whenever energy is
transformed, there is a loss of energy through the release of heat”.
Example:This occurs when energy is transferred between trophic levels. There
will be a loss of energy (about 80-90%) in the form of heat as it moves from one
trophic level to another trophic level. The loss of energy takes place through
respiration, running, hunting etc.,

22. Forests are important components of our environment. Rapid
destruction of this important resource is a cause of concern.
 Afforestation, preventing reckless cutting of trees and making
everyone aware of the need to conserve it will help forest
conservation.
Nature enjoys ecological balance only if the relative number of
species is not disturbed. So, conservation of wildlife is important
for the future.
National parks, wildlife sanctuaries and biosphere reserves are
established to protect and conserve wildlife.
Such measures would ensure that the wildlife does not become
extinct.
Conservation of aquatic life would be ensured by removal of
industries near water bodies.
Conservation of Ecosystem:

23. Functions of ecosystem :
 Ecosystems are complex dynamic system.
 They perform certain functions. These are:-
(i) Energy flow through food chain
(ii) Nutrient cycling (biogeochemical cycles)
(iii)Ecological succession or ecosystem development
(iv)Homeostasis (or cybernetic) or feedback control
mechanisms
Ponds, lakes, meadows, marshlands, grasslands, deserts
and forests are examples of natural ecosystem.
Many of you have seen an aquarium; a garden or a lawn
etc. in your neighbourhood. These are man made
ecosystem.

24. An ecosystem comprises of two basic components
Abiotic Components
Biotic Components
The relationship between the biotic components and abiotic
components of an ecosystem is called 'holocoenosis'.
The Components Of Ecosystems

25. Ecosystem

26. Ecosystems

28. Abiotic factors are the non-living parts of an environment.
These include things such as sunlight, temperature, wind,
water, soil and naturally occurring events such as storms, fires
and volcanic eruptions.
Biotic factors are the living parts of an environment, such as
plants, animals and micro-organisms.
Together, they are the biological factors that determine a
species' success.
Each of these factors impacts others, and a mix of both is
necessary for an ecosystem to survive.

29. Biotic or Living Factors
All living organisms, from microscopic organisms to
humans, are biotic factors.
Microscopic organisms are the most plentiful of these and
are widely distributed.
They are highly adaptable, and their reproduction rates are
rapid, allowing them to create a large population in a short
time.
The conditions needed for growth are few, so they can
easily thrive in a greater variety of environments.
The presence or absence of other organisms influences
whether a species needs to compete for food, shelter and
other resources.

30. Different species of plants may compete for light, water and
nutrients.
Some microbes and viruses can cause diseases that may be
transmitted to other species, thus lowering the population.
The presence of predators impacts the ecosystem.
The effect this has depends on three factors: the number of
predators in a given environment, how they interact with
prey and how they interact with other predators.
The existence of multiple predator species in an ecosystem
may or may not impact each other, depending on their
preferred food source, the size of the habitat and the
frequency and quantity of food required.

31. In some cases, biotic factors can prevent abiotic factors from
doing their job.
An overpopulation of a species can impact abiotic factors and
have a negative effect on other species.
Even the smallest organism, such as phytoplankton, can
devastate an ecosystem if it is allowed to overpopulate.
This is seen in “brown algal blooms” where an excessive
number of algae collect on the surface of the water and prevent
the sunlight from reaching the area below, effectively killing
all life beneath the water.
On land, a similar situation is seen when a tree canopy grows
to cover a large area, effectively blocking the sun from
reaching plant life below.

32. Biotic Components :
The biotic/living components of the ecosystem can be
classified as flora and fauna based on their
structure and other features.
It comprises the living part of the environment,
which includes the association of a number of
interrelated populations belonging to different
species in a common environment.
The populations are that of animal community,
plant community and microbial community.
Functionally, Biotic community can be classified into
autotrophs, heterotrophs and saprotrophs.

35. A) Autotrophs (Gr: auto - self, trophos - feeder) are
also called producers, convertors or transducers.
These are photosynthetic plants, generally
chlorophyll bearing, which synthesize high-energy
complex organic compounds (food) from inorganic raw
materials with the help of sunlight, and the process is
referred as photosynthesis.
Autotrophs form the basis of any biotic system.
In terrestrial ecosystems, the autotrophs are mainly
the rooted plants.
In aquatic ecosystems, floating plants called
phytoplankton and shallow water rooted plants
called macrophytes are the dominant producers.

36. The producers therefore include green plants,
photosynthetic bacteria and chemosynthetic
bacteria.
On land photosynthesis is carried out mainly by
higher plants.
In the sea the main photosynthetic organisms are the
microscopic algae, planktons, diatoms and the
flagellates.

37. B)Heterotrophs (Gr: heteros - other; trophs -
feeder) are called consumers, which are generally
animals feeding on other organisms.
Heterotrophic organisms are unable to
synthesize their own food and hence obtain them
by feeding on other organisms.
Consumer's also referred as phagotrophs (phago -
to ingest or swallow) or macroconsumers are
mainly herbivores and carnivores.
The consumers are classed into various categories
based on the nature of the food they consume,
such as Herbivores, Carnivores and
Omnivores.

38. And also be classified as,
Primary consumers/ Herbivores
Secondary consumers/ Carnivores
Tertiary consumers/ Omnivores
1) Herbivores are referred as First order consumers or primary
consumers, as they feed directly on plants.
Primary consumers can be grazers or browsers.
The amount they consumed are commonly referred to as the
consumption rate. Based on these the ecosystem can be
grouped as high rated, low rated.
For e.g., Terrestrial ecosystem consumers like cattle, deer, rabbit,
grass hopper, etc.
Aquatic ecosystem consumers like protozoans, crustaceans, etc.

39. Plant eating insect
Grazing cattle

40. 2) Carnivores are animals, which feed or prey
upon other animals.
Heterotrophic animals which feed on herbivorous
organisms or primary consumers are termed as
the secondary consumers.
i)Primary carnivores or Second order
consumers include the animals which feed on
the herbivorous animals. For e.g., fox, frog,
predatory birds, smaller fishes, snakes, etc.
ii)Secondary carnivores or Third
order consumers include the animals, which
feed on the primary carnivores. For e.g., wolf,
peacock, owl, etc.
Secondary carnivores are preyed upon by some
larger carnivores.

41. iii)Tertiary carnivores or Quaternary
consumers include the animals, which feed on the
secondary carnivores. For e.g., lion, tiger, etc. These
are not eaten by any other animals.
The larger carnivores, which cannot be preyed upon
further are called top carnivores.
Omnivores
Organisms feeding upon both plants and animals.
e.g. human, pigs and sparrow.
These are carnivorous heterotrophs that feed on other
carnivorous animals.
Top carnivorous are few in number.

42.  a Tertiary consumer can eat many different
animals and even plants sometimes. This means
that they can actually be carnivorous or
omnivorous. 
Some examples of tertiary consumers include,
birds of prey or raptors (Eagle, vulture, falcon,
hawks), big cats (tiger, cheetah, leopard, jaguar)
and foxes.

43. Grassland ecosystem showing
component parts

45. C) Saprotrophs are also called decomposers or
reducers or detrivores or detritus feeders.
They break down the complex organic compounds of
dead matter (of plants and animals) and convert this
matter into nitrogen and carbon dioxide.
 Decomposers do not ingest their food.
Instead they secrete digestive enzymes into the
dead and decaying plant and animal remains to digest
the organic material.
Enzymes act upon the complex organic
compounds of the dead matter.
Decomposers absorb a part of the decomposition
products for their own nourishment.

46. Fungus Bacteria
The remaining substances are added as minerals to
the substratum (mineralization).
Released minerals are reused (utilized) as
nutrients by the plants (producers).
Decomposers are mainly fungi and bacteria.
The saprophytes play a vital role in recycling
the nutrients so that the producers i.e. plants can
use them once again.

47. Abiotic or Non-living Factors
Abiotic factors are the non-living parts of the
environment that can often have a major influence
on living organisms.
The non-living abiotic factors control which organisms
live in an ecosystem, where they live, and how many of
them are there.
Even slight changes in abiotic factors can have a
significant effect on organisms and ecosystem.
Abiotic components are the physical and/or the
chemical factors that act on the living organisms at
any part of their life. These are also called as the
ecological factors.
The physical and chemical factors are characteristic of
the environment.

48. The abiotic component can be grouped into following
categories:-
(i) Physical factors:
Sun light, temperature, rainfall, pH, humidity and pressure.
They sustain and limit the growth of organisms in an
ecosystem.
Chemical factors-
(ii) Inorganic substances:
Carbon dioxide, nitrogen, oxygen, phosphorus, sulphur, water,
rock, soil and other minerals.
(iii) Organic compounds:
Carbohydrates, proteins, lipids and humic substances.
They are the building blocks of living systems and therefore,
make a link between the biotic and abiotic components.

49. Climatic factors include light, temperature,
precipitation, atmospheric humidity, rain and wind.
Topographic factors: These include altitude,
surface slope and exposure, etc.
Edaphic factors include mineral content, as well
as soil temperature, texture, moisture level, pH level
and aeration.

50. The abiotic factors vary from ecosystem to ecosystem.
 In an aquatic ecosystem, the abiotic factors may
include water pH, sunlight, turbidity, water depth,
salinity, available nutrients and dissolved oxygen.
 Similarly, abiotic factors in terrestrial ecosystems can
include soil, soil types, temperature, rain,
altitude, wind, nutrients, sunlight etc.

51. Light is electromagnetic radiation within a
certain portion of the electromagnetic spectrum. The
word usually refers to visible light, which is visible to
the human eye and is responsible for the sense of
sight.
The main source of light on Earth is the Sun.
Light is part of the electromagnetic spectrum, which
ranges from radio waves to gamma rays.
Electromagnetic radiation can also be described in
terms of a stream of photons which are mass less
particles each travelling with wave like properties at
the speed of light.
The intensity of light reaching the Earth’s
surface varies with angle of incidence, degree of
latitude and altitude, season, time of day,
amount absorbed and dispersed by atmosphere.
1. Light

52. When the angle of incidence is smaller results into
relative reduction in intensity.
The lower the latitude, the higher the light intensity.
Plants closer to the surface of water receive more
sunlight.
Likewise, sun’s altitude changes due to differences in
latitude, changes in the season and in the time of
day.
The illumination (intensity) of daylight is greatly
diminished by moisture, clouds, and dust in the
atmosphere and also by forest vegetation.
The direction and slope of the mountain also
affect light intensity. There will be no light on the one
side of slope.

53. Illumination is measured in lux.
About 10% of the sunlight which falls over the
water surface, is reflected back and rest 90% of
that pass down in the water.
The phytoplankton, zooplankton, suspended organic
and inorganic particles either reflect or absorb the light
rays.
Depending upon the penetrating of light, oceans are
divided into
1. Euphotic zone (up to 50 meter depth)
2. Disphotic zone (up to 80 to 200 meters depth)
3. Aphotic zone (below 200 meter of depth)

55. EFFECTS OF LIGHT ON PLANT:
Without light, many of the plants would not be
able to produce the energy needs to grow.
Sunlight provides the energy that green plants
use to create sugars, which release energy into
the living things.
Plants get energy from light through a process
called photosynthesis, this process provides
virtually all the energy used by living things.
Many plants grow in direct sunlight, but
most plants show some degree of shade
tolerance.

56. Photoperiodism is a biological response to the
changes in the ratio of light and dark in a 24 - hour
period. Flowering plants may be divided into
three categories:
a) Short day plants: These plants flower in early
spring or autumn and require a dark period
exceeding a certain critical length.
b) Long day plants: These plants require a period
less than the critical period. They flower in summer.
c) Day-neutral plant: These plants are unaffected
by photoperiod.
 Some plants require only a single exposure to
the critical day-night cycle in order to flower.

57. Mainly plants are affected directly by light
with,
1. Intensity
2. Quality
3. Duration
4. Chlorophyll Production
5. Stomatal movement
6. Heating Action
7. Distribution of plants
8. Overall vegetative development of plant

58. Light effects on plants based on its
intensity, quality and duration
which are also known as limiting
factor for plant growth.
1. Intensity: light intensity
increases, the rate of
photosynthesis will increase as long
as other factors are in adequate
supply.
As the rate increases, eventually
another factor will come into short
supply.
The graph shows the effect of low
carbon dioxide concentration.

59. 2. Quality: Normal plant growth requires white light or
sunlight
 Light quality refers to the color or wavelength reaching
the plant's surface.
 If we take an example of a prism (or raindrops) can
divide sunlight into respective colors of red, orange,
yellow, green, blue, indigo and violet.
 Red and blue have the greatest impact on plant growth.
Green light is least effective (the reflection of green light
gives the green color to plants).
Blue light is primarily responsible for vegetative leaf
growth. Red light, when combined with blue light,
encourages flowering.

60. 3. Duration: Photoperiodism : Total length of daily
light period to which plants are exposed .

62. 4. Chlorophyll Production:
 Mostly plants needs light for chlorophyll production.
 So survival of other life also depends upon light as they
depend upon plants for food.
5. Stomatal movement
Basically opening and closing of stomata is regulated by light.
It is also related with transpiration and absorption.
6. Heating Action:
By changes in light intensity, heating of plant parts get
changes.
As higher the temperature it creates higher temperature in
plant parts

63. 7. Distribution of plants:
Light is the main reason by which the distribution of
plants is takes places in various places on Earth with
different latitude.
Overall vegetative development of plant:
Heliophytes: They are the plants growing best in full
sun light
Sciophytes: The plants which grow best in low sun
light

64. Plants are indirectly affected by light with,
1. Transpiration Rate
2. Respiration
3. Absorption
1. Transpiration Rate:
By increasing the temperature light is indirectly
affecting the transpiration rate of plant body.
It also affects the water absorption capacity.
Thus, higher intensity of light is connected to dried
habitat.

65. 2. Respiration:
With changes in stomata movement and
transpiration rate, respiration also gets affected
indirectly with light.
3. Absorption:
As transpiration rate changes, absorption of water is
also changes in plant growth rate.

66. EFFECTS OF LIGHT ON ANIMAL:
Light is affecting normal pattern of day and night are
very important for most living things to function
properly.
Animals respond to changes in light intensity by
modifying their behaviour, often moving away
from or towards light.
The waking and sleeping patterns of many
animals are affected by the changes in light over 24
hours or during the year.
Many animals are diurnal, which means they will
naturally wake up when it gets light and go to
sleep when it becomes dark.

67. Nocturnal animals react in the opposite way. They sleep
during the day and wake up at night-time.
There are also crepuscular animals that are active
primarily during twilight, the time just before the sun sets
or rises.
Mainly animals are affected by light with,
1. Migration
2. Hibernation
3. Animal eyes
4. Camouflage
5. Bioluminescence
6. Protoplasm
7. Metabolism
8. Photoperiodism and Biological clock
(Biorhythms)

68. 1. Migration
Many animals are also affected by the change of season. The
length of daylight affects animals when to start
migrating.
Many birds migrate to countries thousands of kilometers away.
They will use the sun to help them find their way (navigate).
Bees also use the position of the sun to navigate.
2. Hibernation
Hibernation is a deep sleep that helps animals to save energy
and survive the winter without eating much.
During hibernation the animal’s body temperature
drops, and its heartbeat and its breathing slow down so
that it does not use much energy.

69. Hibernating animals get ready for their winter
sleep.
In some colder countries, the shorter days trigger
hibernation in animals like bear.
These animals eat a lot in the warmer months to
build up fat before sleeping in a burrow, cave or hole
during the cold winter.
Eg: Bats, Turtles, Bears, Squirrels, Hedgehog
3. Animal eyes
Insects, such as flies, have compound eyes which is
directly affected by light.
Unlike humans, some animals can see infrared and
ultraviolet light.

70. Bees can see ultraviolet light which helps them see
flowers that reflect ultraviolet light from their petals.
Other animals, such as the piranha, can see infrared light.
Seeing infrared light helps animals to catch their prey.
4. Camouflage with pigmentation:
Many animals have different colours and patterns on their
fur or skin that make them difficult to see. This means they
are camouflaged.
Other animals use color to scare predators.
Chameleons can change color to fit in with the
environment around them.
Animals can do this by changing the size of the pigment
cells in the skin.

71. When these pigment cells change size, they make
different colours and patterns on the skin.

72. 5. Bioluminescence
Bioluminescence is the production and emission of
light by a living organism.
Many animals give out light.
Some animals use chemicals or bacteria inside the
cells of their body to create light.
The male Malaysian firefly is one insect that
produces a particularly spectacular show.
Many fireflies sit on the same bush and all flash their
light at the same time.
Eg: Glow Worm, Dragonfish, Squid.

73. 6. Effect on Protoplasm:
Some animals remain protected by some sort of body
covering which is helping to protect from solar radiation.
Ultraviolet rays are known to cause mutational changes
in the DNA of various organisms.
7. Effect on metabolism:
The metabolic activities of animals are affected by light
through its heating effect on tissues.
It results in an increase in enzymatic activity and in
degree of solubility of salts and minerals.
Animals residing in caves show slow metabolic activities.

74. 8.Photoperiodism and Biological clock (Biorhythms):
Circadian rhythms:
It is mainly working with the Earth’s rotation by working with
day/ night with activity /sleep.
Circatidal rhythms:
In this rhythms, tidal activities are affecting the working of
animal
By changes in high and low tides, the animals which are living in
intertidal zone alternately submerged in water and exposed to
air.
Circalunar rhythms:
It is synchronized with the phases of moon. With the changes in
phases animals are changes their color, size which is also known
as heteronersis.

75. Semilunar rhythms:
It deals with spring tide and neap tide which is
related to the second and fourth quarter of moon.
Circannual rhythms:
The activities of animals are also affected by seasonal
changes during the year.
Metabolic activities of animals are changes with
seasonal changes.

76. 2. TEMPERATURE
The Measure of the intensity of heat is called Temperature
The units of temperature commonly expressed in Degrees of
Fahrenheit scale or on Celsius scale
The Main source of heat energy is the Sun.
Extreme variations in temperature from day to night and
from season to season are found in Inland area.
Organisms which can tolerate wide fluctuations in
temperature are termed - Eurythermal.
Eg: Lizards, Birds and Mammal
Organisms which can tolerate only small variation in
temperature are termed-Stenothermal organisms
Eg: Coral animals, Fishes

77. The temperature at which the organism's life activities
are at the maximum level is called Optimum
temperature.
The lowest temperature at which organisms can live
indefinitely is called - Minimum effective
temperature.
The highest temperature at which an organism can live
indefinitely is called Maximum effective
temperature.
An organisms enters into chill coma if the temperature
is below minimum effective temperature.
The lowest temperature at which survival is possible -
Minimum survival temperature.
An organism goes into heat coma if the temperature is
above maximum effective level.

78. Thermal stratification in lakes in the temperate regions with
marked variations of temperature occurs with the
change of Seasons.
Thermal stratification occurs only in - Temperate lakes.
Formation of different layers of water in freshwater lakes due
to temperature variations is called Thermal stratification.
SUMMER STRATIFICATION
The upper layer of water that having a temperature range of
21 to 25 ·C during summer in temperate lakes is called -
Epilimnion
The zone of water where there is rapid decrease in
temperature at rate of 10 ·C/meter is called –Thermocline
/Metalimnion

79. The cold and oxygen deficient zone of water below the
thermocline is called- Hypolimnion.
Oxygen levels decrease in hypolimnion if the
thermocline is formed - Below the compensation
level.
Over turn of water occurring in the lake after summer
stratification is - Fall overturn
Oxygen rich water from surface reaches deeper area
during fall over turn.
WINTER STRATIFICATION
During winter, surface water freezes to ice where as
water below the surface remains at 40C and is called
Winter stratification.

80. Spring overturn occurs in a stratified lake after
Winter
Periodic replenishment of nutrients and oxygen in
stratified lakes takes place by the Overturn in
lakes.
The phenomenon that upwells the nutrients &
increases the productivity is due to – overturns.
The organisms are not subjected to hypoxia during
winter stagnation as there is - decrease in bacterial
decomposition and respiratory activity of
aquatic organisms.

81. Biological effects of temperature:
a) Effects on animals:
Animals can maintain a fairly constant internal body
temperature by using their behavioral and physiological means
and they are still categorized into three major groups;
1) Animals which can maintain constant body temperature
within narrow limits are Homeotherms Eg: Birds and
Mammals.
2) Animals which are not capable of maintaining constant body
temperature are – Poikilotherms
Eg: Fishes, Amphibians, reptiles etc.
Internal mechanisms to regulate body temperature are absent
in - Poikilotherms

82. Heterotherms – organisms that can switch to
endotherms (source of their body heat is internal) and
homoethermic.
During environmental extremes, some animals may
enter a state of torpor (state of mental and motor
inactivity with partial or total insensibility) by
reducing their metabolism, heartbeat and respiration
to reduce their energy cost and stay warm or cool.
b) Hibernation – seasonal torpor over winter.
Condition especially mammals, of passing the winter
in a torpid state in w/c the body temperature drops
nearly to freezing and the metabolism drops close to
zero.
Amphibians move in and out the water while
desert animals burrow their bodies to the ground to
seek shade.

83. Some desert animals also use hyperthermia to reduce
the difference between body and environmental
temperature while others employ countercurrent
circulation in the blood to reduce heat loss.
c) Thermal migrations:
Migration of animals to the places of optimum
temperature range to escape extremes of temperature is -
Thermal migration
Desert animals move to shaded places to avoid scorching
heat of the sun during – Noon
The Organisms which can move between land and water
in an attempt to - Minimise the effect of change in
temperature on their bodies.

84. Thermal migration in desert animals takes place during –
Noon
The organisms move between land & water to minimise
the effect of temperature are - Amphibians, Crocodiles,
Hippopotamus.
d) Effect on plants:
It has greater influence on life on earth by affecting the
rates of photosynthesis and stored energy in plants.
It also influences the amount of moisture and the need
for it by the organisms because it takes part in the
chemical reactions in all living organisms.
Variation in the environmental temperature affects the
distribution and abundance of organisms.

85. Temperature varies depending on the latitude,
altitude, season, and continents, microclimatic
variation and depth variation.
Air temperature decreases with altitude, the higher
the altitude the lower the temperature, decreasing by
0.6°C every 100 meters.
Similarly, As latitude increases, temperature
decreases.
Temperature also affects the function of plants and
coldblooded animals by controlling the rate of their
metabolism.
Plants can tolerate extreme cold by frost hardening
its body part but the response is for short period only.

86. Prolonged exposure to extreme conditions like heat
and cold could affect their physiological processes and
may cause death.
Plants living in desert have thick barks and
small leaves to reduce the loss of water.
Some plants were able to survive in very low
temperature by their creeping habits to avoid too
much exposure to extreme low temperature.

87. e) Metabolism
Effect of temperature on metabolic activities of animals
is more significant in Poikilothermic than in
Homeothermic animals because Homeotherms
maintain constant body temperature.
Temperature regulates metabolism because
temperature influences the - Activity of enzymes.
Effect of temperature is not significant in
Homeotherms
Doubling of rate of biochemical reactions with every 10
·C rise in temperature is called - Van't Hoff rule.

88. The effect of temperature on the rate of reaction is
expressed as - temperature coeffecient or Q
Value of Q for an enzyme controlled reaction is
approximately -2.
f) Effect of temperature on sex ratio
Increase in the number of male individuals -In
Ratflea xenopsylla cheopis population than the
female individuals is due to increase in
temperature.
Recent invitro and invivo experiments on turtle
embryo have shown bipotential gonads are
masculanized in the absence of - Temperature
trigger.

89. Female producing temperatures cause the enzyme aromatase to
act locally on gonads to produce estrogen and activate the
development of Ovaries.
g) Cyclomorphosis
Modifications in the body form in relation to seasonal changes in
temperature are cyclomorphosis.
Cyclomorphosis was observed in Daphnia.
In winter head of Daphnia is Round
The helmet like projection starts on head of Daphnia during
Spring season, completely found during Summer, begins to
decrease during Autumn and it completely disappear & the
head becomes round during- winter
During winter Daphnia can float on water due to more
density of water.

90. 3. Humidity
The amount of water vapor in the air.
The amount of water in the air expressed as the
percentage of saturation vapor pressure is relative
humidity.
Temperature plays a role in climate and to the
amount of water it can hold.
Warm air can hold more water than cold air. If the cool air
have constant amount of moisture, the relative humidity
increases and if it reaches the saturation vapor pressure
it will condense and becomes cloud.
When the particles of water or ice become too heavy in the
air, it will fall as rain or snow.

91. The relative humidity of the atmosphere greatly
influenced the land organisms. The greater the
humidity the lesser is the risk of dehydration in the
organisms.
Humidity and shortage of available water are very
much linked. Areas with low water such as desert
have also low humidity.
Other factors such as temperature and wind
significantly affect the rate of evaporation that affect
the humidity.
The capability of the organisms to adapt to these
variable moisture condition influences their distribution
in a habitat.

92. Organisms that have poor water control lives in damp
habitat while organism that have the ability to
regulate their water intake survive in desert
environment.

93. 1.Conservation methods:
Water vacuoles for storage;
spending energy during the cool mornings or
evenings (hunting/foraging)
Guard cells in plants
oWater is important for all metabolic activities.
Water (H
2O) is a very important abiotic factor – it is
often said that “water is life.” All living organisms
need water. Plants must have water to grow. Even
plants that live in the desert need a little bit of water
to grow. Without water, animals become weak and
confused, and they can die if they do not rehydrate.
4.Water

94. Water is required by all living things because it is
critical for cellular processes.
Since terrestrial organisms lose water to the
environment by simple diffusion, they have evolved
many adaptations to retain water.
Animals will be covered in an oily or waxy skin
or cuticle to retain moisture.
Plants have a number of interesting features on
their leaves, such as leaf hairs and a waxy
cuticle, that serve to decrease the rate of water
loss via transpiration.

95. It is the most abundant substance on the earth.
3/4
th
of the earth is covered with water.
Composition of water is oxygen 85.8%, hydrogen
10.7%, chlorine 2.1%, sodium 1.1%, magnesium 0.14%.
Water continuously circulates between the atmosphere
and lithosphere and this process is called hydrological
cycle.
Solar heat evaporates water from the ocean –great
reservoir of water.
A lesser amount of water is also evaporated from surface
of land and from plants, a process known as
evapotranspiration.

96. 5. Wind- Wind is moving air.
Wind can be an important abiotic factor of terrestrial ecosystem
because it influences the rate of evaporation and transpiration.
The physical force of wind is also important because it can move
soil, water, or other abiotic factors, as well as an ecosystem’s
organisms.
Wind is essential to deliver precipitation, crucial for all types of
forest ecosystems.
Wind affects evaporation, transpiration, spatial distribution of
snow, and regulates temperature and moisture regime in
forests.
Wind influences physiological processes in trees and modifies
mechanical and technical properties of wood.

97. It increases the rate of water loss from the organisms,
therefore affecting their distribution.
Wind is also important in formation of rain. In
deserts winds form sand dunes which can be habitats
for other organisms.
Wind causes wave formation in lakes and ocean,
which enhance aeration of water in this water bodies.
Wind also disperses spores and seeds hence influence
disposal and migration of flying animals.
A wind vane or windsock is used to determine the
direction of prevailing wind.
Anemoter is used to measure the speed of wind.

98. 6. Inorganic Nutrients and Soil
Inorganic nutrients, such as nitrogen and phosphorus,
are important in the distribution and the abundance of
living things.
Plants obtain these inorganic nutrients from the soil when
water moves into the plant through the roots.
Therefore, soil structure (particle size of soil components),
soil pH, and soil nutrient content play an important role in
the distribution of plants.
Animals obtain inorganic nutrients from the food they
consume.
Therefore, animal distributions are related to the
distribution of what they eat.

99. Important parts:
Topsoil – At top; contains important minerals
Detritus – dead plant/animal material
Bedrock – good or poor drainage
Plants need certain minerals to grow such as N, K, P, Mg, and
Ca, present in soil.
Soil pH content
The pH of soils can have a huge effect on the plants that are
able to grow in them. Some plants, like azaleas, grow best in
acidic soils and will quickly die if planted in alkaline soils.
Others, like clematis, prefer alkaline soils.
Some, like the hydrangea, can grow in both. These plants are
unusual in that their flower colour changes in different
soils. Just like universal indicator paper, hydrangea flowers are
pink in acidic soils and blue in alkaline soils..

100. Soil mineral content
Many plants require high levels of soil minerals to
grow well.
An example of this is magnesium, which is required
to produce chlorophyll.
Plants with unnaturally yellow leaves may have a
magnesium deficiency.
Carnivorous plants, such as pitcher plants, have
evolved to catch insects to supplement the low levels
of minerals found in the soils in which they grow.

101. 7. Atmospheric Pressure
The atmosphere has a definite weight and so it
exerts pressure on the earth.
On the surface of the earth, atmospheric pressure
varies with altitude.
Variations in atmospheric pressure affects the
amount of Oxygen available for respiration and of
carbon dioxide for photosynthesis.
Thes two gases affect the distribution of
organisms.

102. 8. Oxygen:
Some abiotic factors, such as oxygen, are important in
aquatic ecosystems as well as terrestrial
environments.
Terrestrial animals obtain oxygen from the air they breathe.
Oxygen availability can be an issue for organisms living at
very high elevations, however, where there are fewer
molecules of oxygen in the air.
In aquatic systems, the concentration of dissolved
oxygen is related to water temperature and the speed at
which the water moves.
Cold water has more dissolved oxygen than warmer water.
In addition, salinity, current, and tide can be
important abiotic factors in aquatic ecosystems.

103. 9. Carbon dioxide 
Carbon dioxide is a reactant in photosynthesis which
means plants need it to survive.
Areas with higher levels of carbon dioxide are
more likely to have healthy plants growing.
Farmers often release carbon dioxide within their
greenhouses to maximize their crop yield.
Woodlands often have higher carbon dioxide levels
than open grassland, so many plants living in open
areas have evolved mechanisms to overcome a
shortage of carbon dioxide.

104. 10.pH ( Hydrogen ion Concentration)
pH is is the measure of how acidic or alkaline water is
in aquatic animals or soil solution.
It influences the distribution of plants and animals in
soil and fresh water ponds.
Some plants drive well in acidic conditions while
others in alkaline conditions.
The pH of a soil can be altered by leaching fertilizers’
applied or soil exhaustion. pH is expressed in terms of
pH scale by use of universal indicator solution or
paper and pH meter.

105. 11. Salinity
It refers to the salt concentration of water, causing
a division of the aquatic environment into marine,
estuarine and fresh water.
Saline conditions immediately outside the body of
organism pose the problem of water loss from the body
to the environment.
Only animals with suitable osmoregulation
adaptations can occupy such habitats.
Salinity can be determined by calculating percentage of
of salts on water or by the acid-base titration method.

107. Energy has been defined as the capacity to do
work. Energy exists in two forms potential and kinetic.
Potential energy is the energy at rest {i.e., stored
energy) capable of performing work. Kinetic energy is
the energy of motion (free energy).
Energy flow, also called the calorific flow, refers to
the flow of energy through a food chain, and is the
focus of study in ecological energetics. 
The source of energy required by all living organisms is
the chemical energy of their food . The chemical
energy is obtained by the conversion of the radiant
energy of sun.

108. The chemical energy stored in the food of living
organisms is converted into potential energy by the
arrangement of the constituent atoms of food in a
particular manner.
In any ecosystem there should be unidirectional flow of
energy.
This energy flow is based on two important Laws of
Thermodynamics which are as follows:
(1) The first law of Thermodynamics:
It states that the amount of energy in the universe is
constant.
 It may change from one form to another, but it can
neither be created nor destroyed.
 Light energy can be neither created nor destroyed as it
passes through the atmosphere.

109. It may, however, be transformed into another type of energy,
such as chemical energy or heat energy.
These forms of energy cannot be transformed into
electromagnetic radiation.
(2) The second law of Thermodynamics:
It states that non-random energy (mechanical, chemical,
radiant energy) cannot be changed without some degradation
into heat energy.
The change of energy from one form to another takes place in
such a way that a part of energy assumes waste form
(heat energy).
In this way, after transformation the capacity of energy to
perform work is decreased. Thus, energy flows from higher
to lower level.

110. Flow of energy at different levels of
ecosystem

111. When the light energy falls on the green surfaces of
plants, a part of it is transformed into chemical energy
which is stored in various organic products in the plants.
When the herbivores consume plants as food and
convert chemical energy accumulated in plant
products into kinetic energy, degradation of energy
will occur through its conversion into heat.
When herbivores are consumed by carnivores of the first
order (secondary consumers) further degradation will
occur.
Similarly, when primary carnivores are consumed by top
carnivores, again energy will be degraded.

112. What is Food Chain?
Flow of energy in an ecosystem is one way process. The
sequence of organism through which the energy flows, is
known as food chain.

113. Important facts
In a food chain each organism obtains energy from the one at
the level below.
Plants are called producers because they create their own
food through photosynthesis
Animals are consumers because they cannot create their
own food, they must eat plants or other animals to get the
energy that they need.

114. Characteristics of a Food Chain
In a food chain,
a) there is repeated eating in which each group eats
the smaller one and is eaten by the larger one. Thus, it
involves a nutritive interaction between the biotic
components of an ecosystem.
b) the plants and animals which depend successively
on one another form the limbs of a food chain.
c) there is unidirectional flow of energy from sun to
producers and then to a series of consumers of various
types.
Thus, a food chain is always straight and proceeds in a
progressing straight line.

115. d) usually 80 to 90% of potential energy is lost as heat at
each transfer on the basis of second law of
thermodynamics (transformation of energy involves
loss of unavailable energy).
e) usually there are 4 or 5 trophic levels. Shorter food
chains provide greater available energy and vice -
versa.
f ) omnivores occupy more than one trophic level
and, some organisms occupy different trophic positions
in different food chains.

116. The trophic level of an organism is
the position it occupies in a food
chain.
The producers and consumers in
ecosystem can be arranged into
several feeding groups, each
known as trophic level (feeding
level). In any ecosystem, producers
represent the first trophic level,
herbivores present the second
trophic level, primary carnivores
represent the third trophic level
and top carnivores represent the
last level.

117. Types of Food Chain
(i) Grazing Food Chain
 The consumers utilizing plants as their food , constitute
grazing food chain.
 This food chain begins from green plants and the primary
consumer is herbivore.
 Most of the ecosystem in nature follows this type of food
chain.
 Ex: grass => grasshopper => birds => falcon
Level 1: Plants and algae make their own food and
are called producers. Level 2: Herbivores eat plants
and are called primary consumers.  Level 3:
Carnivores that eat herbivores are called secondary
consumers. Level 4: Carnivores that eat other
carnivores are called tertiary consumers

118. Grazing Food Chain

119. (ii) Detritus food chain
 This type of food chain starts from dead organic
matter of decaying animals and plant bodies to the
micro-organisms and then to detritus feeding
organism and to other predators.
 The food chain depends mainly on the influx of
organic matter produced in another system.
 The organism of the food chain includes algae,
bacteria, fungi, protozoa, insects, nematodes etc.

120. DETRITUS FOOD CHAIN

121. Significance of Food Chain
The knowledge of food chain helps in understanding the
feeding relationship as well as the interaction between
organism and ecosystem.
It also help in understanding the mechanism of energy flow
and circulation of matter in ecosystem.
It also helps to understand the movement of toxic substance
and the problem associated with biological magnification in
the ecosystem.

122. Arrows are used to show where the energy is
going.

124. What is food web?
Food web can be defined as, "a network of food chains which
are interconnected at various tropic levels, so as to form a
number of feeding connections amongst different organisms
of a biotic community".
It is also known as consumer-resource system.

125. Important facts:
A node represents an individual species, or a group of related
species or different stages of a single species.
A link connects two nodes. Arrows represent links, and
always go from prey to predator.
The lowest tropic level are called basal species.
The highest tropic level are called top predators.
Movement of nutrients is cyclic but of energy is
unidirectional and non-cyclic.

126. TYPES OF FOOD WEB REPRESENTATION

127. Different food webs
 Soil food web
Aquatic food web
 Food web in forest
 Food web of grassland
 Food web in terrestrial and aquatic ecosystem

129. Aquatic food web

130. Food web in forest

131. Grassland Food Web

132. Food web in terrestrial and aquatic
ecosystem

133. Significance of Food Web
Food webs distinguish levels of producers and
consumers by identifying and defining the
importance of animal relationships and food sources,
beginning with primary producers such as plants,
insects and herbivores.
Food webs are important tools in understanding that
plants are the foundation of all ecosystems and food
chains, sustaining life by providing nourishment and
oxygen needed for survival and reproduction.
 The food web provide stability to the ecosystem.

134. The arrangement of biotic components of the food
chain according to their size, metabolic relationship is
known as ‘Trophic Structure’.
This is specific to each ecosystem.
The relationship between the various trophic levels of
a food chain (Producers herbivores carnivores) can
be shown diagrammatically by ‘ Ecological
pyramids’.
Ecological pyramids was first proposed by British
Ecologist, Charles Elton (1927), and can also be called
as ‘Eltonian pyramids’.
ECOLOGICAL PYRAMIDS

135. Ecological pyramids are graphical
representations of the tropic structure
ecosystem.
Tropic levels are the feeding positions in a
food chain such as primary producers,
herbivores, primary carnivore etc.
Graphs have been made to show number of
individuals, energy, and biomass, and because
all of these have a triangular shape they have
been termed ecological pyramids.

136. Pyramid of Numbers
It is the graphic representation of number of individuals per unit area of
various tropic levels.
It shows the relationship between the producers, herbivores and carnivores in terms
of their numbers.
This indicates the number of organisms at every trophic level.
Types of Ecological Pyramid
Three types of ecological pyramids can usually be
distinguished namely:
  Pyramid of numbers
  Pyramid of biomass
  Pyramid of productivity/Energy

137. Pyramid of numbers
Large number of producers tend to form
the base.
Lower numbers of top carnivores occupy
the tip.
The pyramids are not necessarily upright. In some
ecosystems there can be more primary consumers
than producers.

140. Parasitic Food chain (Inverted)

141. ADVANTAGES
Simple method of giving an overview
Good for comparing changes to the ecosystem at
different times
DISADVANTAGES
Number of specific species may be too great to
measure accurately.
Does not take into account “juveniles” or
immature forms.
All organisms are included regardless of size.

142. Pyramid of biomass
It is the graphical representation of biomass present per unit
area at different tropic levels, with producers at the base and
carnivores at the top.
The amount of living material in an organism is called biomass.
Biomass refers to the total weight of dry matter or caloric value
present in the ecosystem at any time.
Biomass is calculated as mass of each individual X no. of
individual at tropic levels.
Pyramid of biomass shows quantitative relationship existing
at various trophic levels.
These pyramids are not necessarily upright.
There can be lower amounts of biomass at the bottom of the
pyramid if the rate of primary production per unit biomass
is high.

145. In an ecosystem the pyramid of energy shows the amount of total
energy trapped by the organism at each trophic level in a unit area
and time and expressed as kcal/m2/year.
Pyramid of productivity is a graphical representation of the
flow of energy through each tropic level of a food chain over a
fixed time period.
Energy pyramids provide the best picture of overall nature of the
ecosystem.
Energy pyramid is always upright in all ecosystems.
As you move up the energy pyramid the amount of available energy
decreases because organisms in each trophic level use the energy for
life processes (movement, growth, reproduction) and the energy is
released as heat from the body.
This is the (RULE OF 10s) only about 10% of the energy at any
given level is transferred to the next.
Pyramid of Energy

147. This is an example of an ENERGY PYRAMID

148. Pyramid of productivity

149. Advantages of the pyramid of energy :
It takes account of the rate of production over a
period of time-Shows actual energy transfer
Two species of comparable biomass may have very
different life spans. Thus a direct comparison of their
total biomasses is misleading, but their productivity
is directly comparable.
The relative energy chain within an ecosystem can be
compared using pyramids of energy; also
different ecosystems can be compared.
There are no inverted pyramids.
The input of solar energy can be added.

150. Disadvantages of the pyramid of energy :
The rate of biomass production of an organism is
required, which involves measuring growth and
reproduction through time.
It is difficult to collect energy data.
Problem occurs in assigning a species to a specific
tropic level.
Can be compared different ecosystems based on
relative energy transfer.

151. Disturbances in ecosystem
•Bioaccumulation - When plants / animals take up a
chemical from the environment and do not excrete it, the
chemical builds up in the organism over time to a
potentially lethal level.
•Biomagnification - Refers to the sequence of processes
that results in higher concentrations of the chemical
in organisms at higher levels in the food chain. The
concentration of the chemical may not affect lower levels
of the food chain but the top levels take in so much it can
cause disease or death.
•Extinction of species – Due to decrease in population
of various species the balance of various tropic levels is
disturbed as a result some levels have more accumulation
of species while others have very less population.

152. Ecological Succession:
In an area one community may be replaced by another
community or by a series of communities.
Thus the progressive replacement of one community
by another till the development of stable community in a
particular area is called ecological succession.
Stages of ecological succession:
 1. Pioneer community- The first group of organism,
which establish their community in the area is called
‘Pioneer’ Community.
2. Seres (or) Seral stage- The various developmental
stages of a community is called ‘seres’.

153. Types of ecological succession:
Ecologists recognize two types of ecological succession,
used on the conditions present at the beginning of the
process.
1.Primary succession- It involves the gradual
establishment of biotic communities on a lifeless ground.
a.Hydrarch (or) Hydrosere -Establishment starts in a
watery area like pond and lake.
b.Xerarch or Xerosere- Establishment starts in a dry area
like, desert and rock
2. Secondary succession- It involves the establishment of
biotic communities in the area, where some type of biotic
community is already present.