Biological Diversity.pdf dgbsrrfeafdqwdwfqe

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1. Energy Flow in the ecosystem
Energy Flow
The chemical energy of food is the main source of energy required by all living organisms.
This energy is transmitted to different trophic levels along the food chain. This energy flow is
based on two different laws of thermodynamics:
• First law of thermodynamics, that states that energy can neither be created nor
destroyed, it can only change from one form to another.
• Second law of thermodynamics, that states that as energy is transferred more and
more of it is wasted.
Energy Flow in Ecosystem
The energy flow in the ecosystem is one of the major factors that support the survival of such
a great number of organisms. For almost all organisms on earth, the primary source of energy
is solar energy. It is amusing to find that we receive less than 50 per cent of the sun’s
effective radiation on earth. When we say effective radiation, we mean the radiation, which
can be used by plants to carry out photosynthesis.
Most of the sun’s radiation that falls on the earth is usually reflected back into space by the
earth’s atmosphere. This effective radiation is termed as the Photosynthetically Active
Radiation (PAR).
Overall, we receive about 40 to 50 percent of the energy having Photosynthetically Active
Radiation and only around 2-10 percent of it is used by plants for the process of
photosynthesis. Thus, this percent of PAR supports the entire world as plants are the
producers in the ecosystem and all the other organisms are either directly or indirectly
dependent on them for their survival.
The energy flow takes place via the food chain and food web. During the process of energy
flow in the ecosystem, plants being the producers absorb sunlight with the help of the
chloroplasts and a part of it is transformed into chemical energy in the process
of photosynthesis.
This energy is stored in various organic products in the plants and passed on to the primary
consumers in the food chain when the herbivores consume (primary consumers) the plants as
food. Then conversion of chemical energy stored in plant products into kinetic energy occurs,
degradation of energy will occur through its conversion into heat.
Then followed by the secondary consumers. When these herbivores are ingested by
carnivores of the first order (secondary consumers) further degradation will occur. Finally,
when tertiary consumers consume the carnivores, energy will again be degraded. Thus, the
energy flow is unidirectional in nature.
Moreover, in a food chain, the energy flow follows the 10 percent law. According to this law,
only 10 percent of energy is transferred from one trophic level to the other; rest is lost into the
atmosphere. This is clearly explained in the following figure and is represented as an energy
pyramid.
Energy Movement and Trophic level

2. The producers and consumers in the ecosystem can be arranged into different feeding groups
and are known as trophic level or the feeding level.
Energy flows through the different trophic levels. It begins with the energy from the sun that
autotrophs use to produce food. This energy is transferred up the levels as the different
organisms are consumed by members of the levels that are above them. Approximately 10%
of the energy that is transferred from one trophic level to the next is converted to biomass.
Biomass refers to the overall mass of an organism or the mass of all the organisms that exist
in a given trophic level. Since organisms expend energy to move around and go about their
daily activities, only a part of the energy consumed is stored as biomass.
he producers (plants) represent the first trophic level.
1. Herbivores (primary consumers) present the second trophic level.
2. Primary carnivores (secondary consumers) represent the third trophic level
3. Top carnivores (tertiary consumers) represent the last level.
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.
Because energy, in the form of heat, is lost at each step, or trophic level, chains do not
normally encompass more than four or five trophic levels. People can increase the total food
supply by cutting out one step in the food chain: instead of consuming animals that eat cereal
grains, the people themselves consume the grains. Because the food chain is made shorter,
the total amount of energy available to the final consumers is increased.
Example:

There are basically three different types of food chains in the ecosystem, namely –

3. • Grazing food chain (GFC) – This is the normal food chain that we observe in which
plants are the producers and the energy flows from the producers to the herbivores
(primary consumers), then to carnivores (secondary consumers) and so on.
• Saprophytic or Detritus food chain (DFC) – In this type of food chain, the dead
organic matter occupies the lowermost level of the food chain, followed by the
decomposers and so on.
• Parasitic food chain (PFC) – In this type of food chain, large organisms either the
producer or the consumer is exploited and therefore the food passes to the smaller
organism.
Food Web
In nature, we mostly observe food web as there are many organisms which are omnivores. As
a result, they occupy multiple trophic levels.
A food web is a detailed interconnecting diagram that shows the overall food relationships
between organisms in a particular environment. It can be described as a "who eats whom"
diagram that shows the complex feeding relationships for a particular ecosystem.
The study of food webs is important, as such webs can show how energy flows through an
ecosystem.
It also helps us understand how toxins and pollutants become concentrated within a particular
ecosystem. Examples include mercury bioaccumulation in the Florida Everglades and
mercury accumulation in the San Francisco Bay.
Food webs can also help us study and explain how the diversity of species is related to how
they fit within the overall food dynamic. They may also reveal critical information about the
relationships between invasive species and those native to a particular ecosystem.
In a food web, organisms are arranged according to their trophic level. The trophic level for
an organism refers to how it fits within the overall food web and is based on how an organism
feeds.
Broadly speaking, there are two main designations: autotrophs and heterotrophs. Autotrophs
make their own food while heterotrophs do not. Within this broad designation, there are five
main trophic levels: primary producers, primary consumers, secondary consumers, tertiary
consumers, and apex predators.
A food web shows us how these different trophic levels within various food chains
interconnect with one another as well as the flow of energy through the trophic levels within
an ecosystem.
Trophic Levels in a Food Web
Primary producers make their own food via photosynthesis. Photosynthesis uses the sun's
energy to make food by converting its light energy into chemical energy. Primary producer
examples are plants and algae. These organisms are also known as autotrophs.
Primary consumers are those animals that eat the primary producers. They are called
primary as they are the first organisms to eat the primary producers who make their own
food. These animals are also known as herbivores. Examples of animals in this designation
are rabbits, beavers, elephants, and moose.
Secondary consumers consist of organisms that eat primary consumers. Since they eat the
animals that eat the plants, these animals are carnivorous or omnivorous. Carnivores eat

4. animals while omnivores consume both other animals as well as plants. Bears are an example
of a secondary consumer.
Similar to secondary consumers, tertiary consumers can be carnivorous or omnivorous. The
difference being that secondary consumers eat other carnivores. An example is an eagle.
Lastly, the final level is composed of apex predators. Apex predators are at the top because
they do not have natural predators. Lions are an example.
Additionally, organisms known as decomposers consume dead plants and animals and break
them down. Fungi are examples of decomposers. Other organisms known as detritivores
consume dead organic material. An example of a detrivore is a vulture.