Ecosystem | class 12 | cbse

ECOSYSTEM
Created by:
Kush Sehgal
Class XII science
Roll number : 29
Session: 2014-
2015

What Is
Ecosystem
An ecosystem is a community
of living organisms (plants,
animals and microbes) in
conjunction with the nonliving
components of their environment
(things like air, water and
mineral soil), interacting as a
system.

Niche v/s habitat
Habitat:
The natural home or
environment of an animal,
plant, or other organism.
Niche:
A role taken by a type of
organism within its
community.

Biotic Factors
Biotic components
These are the living things that shape an ecosystem.
A biotic factor is any living component that affects another organisms,
including animals that consume the organism in question, and the living food that the
organism consumes.
Example :
a fresh water
ecosystem
showing prey
and a predator

More About Biotic
Components
Biotic components are contrasted to abiotic components, which are non-living
components of an organism's environment, such as temperature,
light, moisture, air currents, etc. Biotic components usually include:

Abiotic factors
In biology and ecology, abiotic components include physical conditions and non-living
resources that affect living organisms in terms of growth, maintenance,
and reproduction. Resources are distinguished as substances or objects in the
environment required by one organism and consumed or otherwise made unavailable
for use by other organisms.
Component degradation of a substance by chemical or physical processes,
e.g. hydrolysis. All non-living components of an ecosystem is called abiotic
components.

productivity
I n ecology, pr oduct ivit y or pr oduct ion r ef er s t o
t he r at e of gener at ion of biomass in an ecosyst em.
I t is usually expr essed in unit s of mass per unit
sur f ace (or volume) per unit t ime, f or
inst ance gr ams per squar e met r e per day (g m-2 d-1).
The mass unit may r elat e t o dr y mat t er or t o t he
mass of car bon gener at ed. Pr oduct ivit y
of aut ot r ophs such as plant s is called pr imar y
pr oduct ivit y, while t hat of het er ot r ophs such
as animals is called secondar y pr oduct ivit y.

Producers, Consumers and
Decomposers
Pr oducer s, i.e. aut ot r ophs: e.g. plant s, t hey
conver t t he ener gy [f r om phot osynt hesis (t he
t r ansf er of sunlight , wat er , and car bon dioxide int o
ener gy), or ot her sour ces such as hydr ot hermal
vent s] int o f ood.
Consumer s, i.e. het er ot r ophs: e.g. animals, t hey
depend upon pr oducer s (occasionally ot her
consumer s) f or f ood.
Decomposer s, i.e. det r it ivor es:
e.g. f ungi and bact er ia, t hey br eak down chemicals
f r om pr oducer s and consumer s (usually dead) int o

ENERGY FLOW
Food chain
A linear sequence of links in a food web starting from species that are called
producers in the web and ends at species that are called decomposers in the web. A
food chain also shows how the organisms are related with each other by the food
they eat. A food chain differs from a food web, because the
complex polyphagous network of feeding relations are aggregated into tropic species
and the chain only follows linear monophagous pathways.

Types of food chain
Grazing food chain - The gr azing f ood chain begins
wit h t he phot osynt het ic f ixat ion of light , car bon
dioxide, and wat er by plant s (pr imar y pr oducer s)
who pr oduce sugar s and ot her or ganic molecules.
Once pr oduced, t hese compounds can be used t o
cr eat e t he var ious t ypes of plant t issues. Pr imar y
consumer s or her bivor es f orm t he second link in
t he gr azing f ood chain.
Detrital food chain - The det r it us f ood chain
dif f er s f r om t he gr azing f ood chain in sever al
ways:t he or ganisms making it up ar e gener ally
smaller (like algae, bact er ia, f ungi, insect s, &

Ecological succession
Ecological
succession is the
observed process of
change in
the species structu
re of an ecological
community over time.
The time scale can
be decades (for
example, after a
wildfire), or even

Primary succession is one of two types of
biological and ecological succession of plant
life, occurring in an environment in which new
substrate devoid of vegetation and usually
lacking soil, such as a lava flow or area left
from retreated glacier, is deposited.

Secondary succession is one of the two types
of ecological succession of plant life. As opposed to
the first, primary succession, secondary succession is
a process started by an event that reduces an already
established ecosystem to a smaller population of
species.

Nutrient cycle
A nut r ient cycle (or ecological r ecycling) is t he
movement and exchange of or ganic
and inor ganic mat t er back int o t he pr oduct ion of
living mat t er . The pr ocess is r egulat ed by f ood
web pat hways t hat decompose mat t er int ominer al
nut r ient s. Nut r ient cycles occur wit hin ecosyst ems.
Ecosyst ems ar e int er connect ed syst ems wher e
mat t er and ener gy f lows and is exchanged as
or ganisms f eed, digest , and migr at e about . Miner als
and nut r ient s accumulat e in var ied densit ies and
uneven conf igur at ions acr oss t he planet .
Ecosyst ems r ecycle locally, conver t ing miner al
nut r ient s int o t he pr oduct ion of biomass, and on a

C a r b o n c y
The car bon cycle is ct h le e
biogeochemical cycle by which car bon is
exchanged among t he biospher e,
pedospher e, geospher e, hydr ospher e,
and atmospher e of t he Ear t h.
The global carbon budget is t he balance of t he
exchanges (incomes and losses) of
car bon bet ween t he car bon r eser voir s
or bet ween one specif ic loop (e.g.,
atmospher e ↔ biospher e) of t he car bon
cycle. An examinat ion of t he car bon

Phosphorus cycle
The phosphorus cycle is the biogeochemical cycle that describes the
movement of phosphorus through the lithosphere, hydrosphere,
and biosphere. Unlike many other biogeochemical cycles,
the atmosphere does not play a significant role in the movement of
phosphorus, because phosphorus and phosphorus-based compounds are
usually solids at the typical ranges of temperature and pressure found on
Earth. The production of phosphine gas occurs only in specialized, local
conditions.
On the land, phosphorus (chemical symbol, P) gradually becomes less
available to plants over thousands of years, because it is slowly lost in
runoff. Low concentration of P in soils reduces plant growth, and slows soil
microbial growth - as shown in studies of soil microbial biomass

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