PPT

2. ECOSYSTEM
Submitted By Submitted To
KRISHNA GAUR Dr. Vijay Kumar Dalal Sir
2003048 AFR101
BSC AGRICULTURE
This Photo by Unknown Author is licensed under CC BY-NC-ND

3. DEFINITION
 Ecosystem is the basic functional unit of
ecology. The term ecosystem is coined
from a Greek word meaning study of
Home.
 A group of organism interacting among
themselves and with the environment is
known as ecosystem An ecosystem is a
community of living organisms in
conjunction with the nonliving components
of their environment, interacting as a
system.
 For example, let's take the relationship
between sheep and lion in the ecosystem;
for its survival, the lion eats the sheep.

4. Types of Ecosystem

5. Components of
ecosystem

6. Energy flow in the Ecosystem
 Energy flow is the flow of energy through living things within an ecosystem. All
living organisms can be organized into producers and consumers, and those
producers and consumers can further be organized into a food chain. Each of the
levels within the food chain is a trophic level. In order to more efficiently show
the quantity of organisms at each trophic level, these food chains are then
organized into trophic pyramids. The arrows in the food chain show that the
energy flow is unidirectional, the head of the arrows show the direction energy is
moving in, and that energy is lost as heat at each step along the way.
 The unidirectional flow of energy and the successive loss of energy as it travels up
the food web are patterns in energy flow that are governed by Thermodynamics,
which is the concept of energy exchange between systems. Trophic dynamics
relates to Thermodynamics because it deals with the transfer and transformation
of energy (originating externally from the sun via solar radiation) to and among
organisms.

8. Nutrient Cycle
 A nutrient cycle refers to the movement and exchange of organic and
inorganic matter back into the production of living matter. The process is
regulated by the food web pathways previously presented, which decompose
organic matter into inorganic nutrients. Nutrient cycles occur within
ecosystems. Nutrient cycles that we will examine in this section include
water, carbon, oxygen and nitrogen cycles.

9. Water Cycle
 Over two thirds of the Earth's surface is covered by water. It forms an important component of most
life forms, with up to 70% of plants and animals being composed of water. Vast quantities of water
cycle through Earth's atmosphere, oceans, land and biosphere. This cycling of water is called the
water or hydrological cycle. The cycling of water is important in determining our weather and
climate, supports plant growth and makes life possible.
 Evaporation: Most water evaporates from the oceans, where water is found in highest abundance.
However, some evaporation also occurs from lakes, rivers, streams and following rain.
 Transpiration: Is the water loss from the surface area (particularly the stomata) of plants.
Transpiration accounts for a massive 50% of land-based evaporation, and 10% of total evaporation.
 Evapotranspiration: The processes of evaporation and transpiration are often collectively referred
to as evapotranspiration.
 Condensation: The process by which water vapour is converted back into liquid is called
condensation. You may have observed a similar process occurring when dew drops form on a blade
of grass or on cold glass. Water in the atmosphere condenses to form clouds.
 Precipitation: Water returns to Earth through precipitation in the form of rain, sleet, snow or ice
(hail). When rain occurs due to precipitation, most of it runs off into lakes and rivers while a
significant portion of it sinks into the ground.
 Infiltration: The process through which water sinks into the ground is known as infiltration and is
determined by the soil or rock type through which water moves. During the process of sinking into
the Earth's surface, water is filtered and purified. Depending on the soil type and the depth to which
the water has sunk, the ground water becomes increasingly purified: the deeper the water, the
cleaner it becomes.
 Melting and freezing: Some water freezes and is 'locked up' in ice, such as in glaciers and ice
sheets. Similarly, water sometimes melts and is returned to oceans and seas.

10. Carbon Cycle
 Carbon is the basic building block of all organic materials, and therefore, of living organisms. Most of the
carbon on earth can be found in the crust. Other reservoirs of carbon include the oceans and atmosphere
 Carbon moves from one reservoir to another by these processes:
 Combustion: Burning of wood and fossil fuels by factory and auto emissions transfers carbon to the
atmosphere as carbon dioxide.
 Photosynthesis: Carbon dioxide is taken up by plants during photosynthesis and is converted into energy
rich organic molecules, such as glucose, which contains carbon.
 Metabolism: Autotrophs convert carbon into organic molecules like fats, carbohydrates and proteins, which
animals can eat.
 Cellular respiration: Animals eat plants for food, taking up the organic carbon (carbohydrates). Plants and
animals break down these organic molecules during the process of cellular respiration and release energy,
water and carbon dioxide. Carbon dioxide is returned to the atmosphere during gaseous exchange.
 Precipitate: Carbon dioxide in the atmosphere can also precipitate as carbonate in ocean sediments.
 Decay: Carbon dioxide gas is also released into the atmosphere during the decay of all organisms.

11. Nitrogen Cycle
 Nitrogen gas present in the air is not available to organisms and thus must be made available in a
form absorbable by plants and animals.
 Only a few single-cell organisms, like bacteria can use nitrogen from the atmosphere directly.
 For plants, nitrogen must be changed into other forms, e.g., nitrates or ammonia. This process is
known as nitrogen fixation.
 The nitrogen cycle involves the following steps:
 Lightning: Nitrogen can be changed to nitrates directly by lightning. The rapid growth of algae after
thunderstorms is because of this process, which increases the number of nitrates that fall onto the
earth in rainwater, acting as fertilizer.
 Absorption: Ammonia and nitrates are absorbed by plants through their roots.
 Ingestion: Humans and animals get their nitrogen supplies by eating plants or plant-eating animals.
 Decomposition: During decomposition, bacteria and fungi break down proteins and amino acids
from plants and animals.
 Ammonification: The nitrogenous breakdown products of amino acids are converted into ammonia
(NH$_{3}$ ) by these decomposing bacteria.
 Nitrification: Is the conversion of the ammonia to nitrates (NO$_{3}$ $^{-}$ ) by nitrifying bacteria.
 Denitrification: In a process called denitrification, bacteria convert ammonia and nitrate into
nitrogen and nitrous oxide (N$_{2}$ O). Nitrogen is returned to the atmosphere to start the cycle
over again.

12. Nitrification and
Denitrification
Nitrification
The conversion of ammonia into nitrates is
termed as nitrification.
Examples:
Nitrobacter, Nitrosomonas
Denitrification
The conversion of nitrates into nitrogen (N2) is
termed denitrification.
Examples:
Pseudomonas, Fluorescence

13. Phosphorus Cycle
Phosphorus moves in a cycle through rocks, water, soil
and sediments and organisms.
 Here are the key steps of the phosphorus cycle
 Over time, rain and weathering cause rocks to release
phosphate ions and other minerals. This inorganic
phosphate is then distributed in soils and water.
 Plants take up inorganic phosphate from the soil. The
plants may then be consumed by animals. Once in the
plant or animal, the phosphate is incorporated into
organic molecules such as DNA. When the plant or
animal dies, it decays, and the organic phosphate is
returned to the soil.
 Within the soil, organic forms of phosphate can be
made available to plants by bacteria that break down
organic matter to inorganic forms of phosphorus. This
process is known as mineralization.
 Phosphorus in soil can end up in waterways and
eventually oceans. Once there, it can be incorporated
into sediments over time.

14. Ecological
Succession
 Ecological succession is the process of change in the species
structure of an ecological community over time. The time
scale can be decades (for example, after a wildfire), or even
millions of years after a mass extinction.
 The community begins with relatively few pioneering plants
and animals and develops through increasing complexity until
it becomes stable or self-perpetuating as a climax community.
The "engine" of succession, the cause of ecosystem change, is
the impact of established organisms upon their own
environments. A consequence of living is the sometimes
subtle and sometimes overt alteration of one's own
environment.
 It is a phenomenon or process by which an ecological
community undergoes orderly and predictable changes
following a disturbance or the initial colonization of a new
habitat. Succession may be initiated either by formation of
new, unoccupied habitat, such as from a lava flow or a severe
landslide, or by some form of disturbance of a community,
such as from a fire, severe windthrow, or logging. Succession
that begins in new habitats, uninfluenced by pre-existing
communities is called primary succession, whereas succession
that follows disruption of a pre-existing community is called
secondary succession

15. Food Chain and
Food Web
Food Chain:
 “There sequence of eating and being eaten in an
ecosystem is known as food chain”
 Food chain, in ecology, the sequence of transfers of
matter and energy in the form of food from organism to
organism. Food chains intertwine locally into a food web
because most organisms consume more than one type of
animal or plant. Plants, which convert solar energy to
food by photosynthesis, are the primary food source. In a
predator chain, a plant-eating animal is eaten by a flesh-
eating animal. In a parasite chain, a smaller organism
consumes part of a larger host and may itself be
parasitized by even smaller organisms. In a saprophytic
chain, microorganisms live on dead organic matter.
Food web:
 A food web consists of all the food chains in a single
ecosystem. Each living thing in an ecosystem is part of
multiple food chains. Each food chain is one possible path
that energy and nutrients may take as they move through
the ecosystem.

17. Ecological Pyramids
 An ecological pyramid is a graphical representation of the relationship
between different organisms in an ecosystem. Each of the bars that make up
the pyramid represents a different trophic level, and their order, which is
based on who eats whom, represents the flow of energy. Energy moves up the
pyramid, starting with the primary producers, or autotrophs, such as plants
and algae at the very bottom, followed by the primary consumers, which feed
on these plants, then secondary consumers, which feed on the primary
consumers, and so on. The height of the bars should all be the same, but the
width of each bar is based on the quantity of the aspect being measured.
 There are three types of pyramids:
1. Pyramids of numbers
2. Pyramids of energy
3. Pyramids of biomass

18. Pyramid of Numbers
 This shows the number of organisms in
each trophic level without any
consideration for their size. This type
of pyramid can be convenient, as
counting is often a simple task and
can be done over the years to observe
the changes in a particular ecosystem.
However, some types of organisms are
difficult to count, especially when it
comes to some juvenile forms. Unit:
number of organisms

19. Pyramid of Energy
 An energy pyramid is a model that
shows the flow of energy from one
trophic, or feeding, level to the next
in an ecosystem. The model is a
diagram that compares the energy
used by organisms at each trophic
level. The energy in an energy
pyramid is measured in units of
kilocalories (kcal). Energy pyramids
are similar to biomass pyramids,
another type of trophic pyramid that
models the amount of biomass at each
trophic level in an ecosystem.

20. Pyramid of Biomass
 This indicates the total mass of organisms at each
trophic level. Usually, this type of pyramid is largest
at the bottom and gets smaller going up, but
exceptions do exist. The biomass of one trophic level
is calculated by multiplying the number of
individuals in the trophic level by the average mass
of one individual in a particular area. This type of
ecological pyramid solves some problems of the
pyramid of numbers, as it shows a more accurate
representation of the amount of energy contained in
each trophic level, but it has its own limitations. For
example, the time of year when the data are
gathered is very important, since different species
have different breeding seasons. Also, since it’s
usually impossible to measure the mass of every
single organism, only a sample is taken, possibly
leading to inaccuracies. Unit: g m-2 or Kg m-2.

21. Thank You