module3Ecosystems.pptx ecology and environment

Learning outcomes:
Ecosystem
• Ecosystem definition, types.
• Ecosystem structure.
• Ecosystem function.

An ecosystem is a group of biotic communities of species interacting with
one another and with their non-living environment .Ecology is often
defined as the study of ecosystems.
Ecosystem

3
Types of Ecosystems
There are different types of ecosystems varying in their structural composition and functions.

Ecosystem
Aquatic
Marine
Freshwater
Terrestrial
Forests
Desert
Grasslands

Structure of
an
ecosystem
Biotic
Producers Consumers
Herbivore Carnivore Omnivore Detritivores
Decomposer
s
Abiotic
Physical chemical

1. Structural features of Ecosystem
1.1 Biotic components Life in an Ecosystem is nutritionally structured.
An ecosystem structure includes both biological (biotic) and non-living (abiotic) components
The plants, animals and microorganisms present in an ecosystem form the biotic component .They are known
as Producers or consumers based on their nutritional behavior.

a. Producers: They are mainly the green plants, which can synthesise their own food by the process of photosysntheis.
They are known as Photo autotrophs (auto-self, troph-food, photo-light.)
C02+H20+ SUNLIGHT+CHLOROPHYLL= FOOD
CO2+H20+H2S=FOOD
b. Consumers: get food by feeding upon other organisms which are of the following types:
• Herbivores ( plant eaters)----primary consumers
• Carnivores (meat eaters)-----secondary or tertiary consumers
• Omnivores (plant & meat eaters)
• Detritivores (saprophytes)
C
. Decomposers: They derive their nutrition by breaking down the complex organic molecules to simpler organic compounds
and ultimately into inorganic nutrients.

The sequence of eating and being eaten in an ecosystem is called Food Chain

MAJOR ROLES OF Biotic components IN ECOSYSTEMS
Ecologists have traditionally divided organisms’ roles in ecosystems into three broad categories: producers, consumers, and decomposers.
Producers are organisms that are able to use sources of energy to make complex, organic molecules from the simple inorganic substances in their environment. In nearly all ecosystems, energy is
supplied by the sun, and organisms such as plants, algae, and tiny aquatic organisms called phytoplankton use light energy to carry on photosynthesis. Since producers are the only organisms in an
ecosystem that can trap energy and make new organic material from inorganic material, all other organisms rely on producers as a source of food, either directly or indirectly.
Consumers are organisms that require organic matter as a source of food. They consume organic matter to provide themselves with energy and the organic molecules necessary to build their own
bodies. An important part of their role is the process of respiration in which they break down organic matter to inorganic matter. However, consumers can be further subdivided into categories based
on the kinds of things they eat and the way they obtain food. Primary consumers, also known as herbivores, are animals that eat producers (plants or phytoplankton) as a source of food.
Herbivores, such as leaf-eating insects and seed-eating birds, are usually quite numerous in ecosystems, where they serve as food for the next organisms in the chain. Secondary consumers or
carnivores are animals that eat other animals. Secondary consumers can be further subdivided into categories based on what kind of prey they capture and eat. Some carnivores, such as ladybird
beetles, primarily eat herbivores, such as aphids; others, such as eagles, primarily eat fish that are themselves carnivores. While these are interesting conceptual distinctions, most carnivores will eat
any animal they can capture and kill. In addition, many animals, called omnivores, include both plants and animals in their diet. Even animals that are considered to be carnivores (foxes, bears)
regularly include large amounts of plant material in their diets. Conversely, animals often thought of as herbivores (mice, squirrels, seed eating birds) regularly consume animals as a source of food.
Parasites are also consumers that have a special way of obtaining their food.
Decomposers are organisms that use nonliving organic matter as a source of energy and raw materials to build their bodies. When ever an organism sheds a part of itself, excretes waste products, or
dies, it provides a source of food for decomposers. Since decomposers carry on respiration, they are extremely important in recycling matter by converting organic matter to inorganic material.
Many small animals, fungi, and bacteria fill this niche.

1.2 Abiotic Structure
Physical factors e.g sun hours,
temperature,soil type,wind etc.
Chemical factors e.g carbon,
nitrogen,phosphorus, potassium
etc.
There is an intimate linkage between the biotic and abiotic components.

Abiotic factors affect living organisms in an ecosystem
Fires destroy forests, but can sometimes help a forest community by allowing
new organisms to thrive
Early or unexpected frost
can kill plants and an
entire food chain.
Wind can affect the way
an organism grows

HOW DOES AN ECOSYSTEM FUNCTION?
• Every ecosystem performs under natural conditions in a systematic way.
• It receives energy from the sun and passes it on through various biotic components and in fact , all life depends
upon this flow of energy.

 Food chain and food webs.
 Energy Flow
 Cycling of nutrients (Biogeochemical cycles)
The major functional attributes of an Ecosystem are as follows:

FOOD CHAINS
The sequence of eating and being eaten up in an ecosystem is called a food chain.
1st
trophic level
2nd
trophic level
3rd trophic level

FOOD CHAINS
Types
Grazing Food chain Detritus Food chain

FOOD WEBS
Food chains in ecosystems are rarely found to operate as isolated linear sequences. Rather, they are found to be
Interconnected and usually form complex network with several linkages and are known as food webs.

Why nature has evolved food webs in ecosystems instead of simple food chains?
• It gives stability to the Ecosystem.
• In a linear food chain, if one species becomes extinct or one species suffers then the species in the subsequent
trophic levels are also affected.
Just consider the simple food chains of Arctic Tundra Ecosystem:
Cladonia Reindeer Man
Grass Caribou Wolf

Significance of food chain
 Food chains and food webs cause energy flow and nutrient cycling in an ecosystem.
 They maintain the population size of different animals .
 Food chains show unique property of bio magnification.

Bio magnification, also known as bio amplification
or biological magnification, is the increasing
concentration of a substance, such as a toxic
chemical, in the tissues of organisms at
successively higher levels in a food chain
Bio magnification

Energy flow in trophic levels :-
 Green plants (producers) absorb about 1% of solar energy
falling on the leaves and stores it as food energy during
photosynthesis.
 During the transfer of food energy from one trophic level to
the next, 90% of the energy is lost to the environment and
only 10% is transferred to the next trophic level.
 This is known as the 10% law.

• The 10 percent law is the main reason that most food
chains have five or less links. Because 90 percent of
the food chain’s energy is lost at each level, the
amount of available energy decreases quickly.
10 PERCENT
LAW!!
MORE Ten Percent Law

Ecological Succession
• Succession
• Ecological succession is an orderly Gradual development of a community of
organisms over time.
• process of changes in the community structure and function with time mediated
through modification in the physical environment and ultimately culminating in a
stabilized ecosystem called Climax.
Seral Stages or Seres
Pioneer community

Primary Succession
• Primary Succession
• A. Takes place after an ecosystem is completely destroyed, including its soil
• B. There is no soil in this area, usually just bare rock
• Example: volcanic eruption

Steps in Primary Succession
• 1. After a volcanic eruption, lava
covers the land and hardens into
rock

Primary Succession
• 2.Lichens begin to form on rocks
• A. Lichens-plant like organism that is a fungus and algae
• B. Acids from the lichens begin to break down the rock
• C. These pieces of broken rock and the remains of dead lichens start forming
soil
Pioneer species- first organisms to grow in a succession
example-lichens

Primary Succession
• 3. After many years
• A. The soil is deep enough for mosses to grow
• B. Mosses replace lichens
• C. Tiny organisms like insects live in the lichens and mosses
• Their remains add to the soil

Primary Succession
• 4. Over time
• Soil layer thickens
• Moss is replaced by ferns
• Next
• Growth of grasses and wildflowers
• Once the soil is deep enough:
• Shrubs and small trees come into the
area

Secondary Succession
• Secondary Succession
• Changes that takes place after an environment is disrupted in some way (the
soil must remain intact)
• Example-forest fire, cyclone, farm land left unused

• 1. fast growing grasses and non-
woody plants appear

• 2. Larger shrubs move in

• 3. Fast growing trees (such as
pines) move in
• 4. These are followed by slower-
growing hardwood trees

• 5. As new plants take root and
grow, animals begin moving back
in the ecosystem
• Succession ends with a climax
community (when species have
adapted to the average conditions
in that area)

Different Ecological successions based on different types of areas
 Hydrarch or Hydrosere
 Mesarch
 Xerarch or Xerosere

Nudation
Invasion
Competition
and coaction
Reaction
Stabilization
(Climax
community)
Process of Ecological succession

Major Ecosystem Types
Forest Grassland Desert Aquatic

Forest Ecosystem
Tropical Rain
Tropical
deciduous
Temperate rain Evergreen coniferous
(Boreal forests)

Tropical rain forest: They are characterized by high temperature, high humidity and high rainfall, all
of which favors the growth of trees.
All through the year the climate remains more or less uniform.
We come across different types and layers of plants and animals in tropical rain forest e.g.
1. The emergent layer is the topmost layer of the tallest broad-leaf evergreen trees.
2. The Canopy layer where top branches of shorter trees form an umbrella like cover.
3. Understory layer of smaller trees.
4. Shrub layer receives even less sunlight.
5. Ground layer or forest floor

Interestingly, the flowers of forests trees are very large, colorful and attractive which helps in pollination by
Insects,birds, bats etc. e.g. Rafflesia arnoldi (7kgs).
ENDEMIC TO SUMATRA RAINFOREST

Tropical deciduous forest:
They are found a little away from the equator and are characterized by warm climate
the year round.
Temperate rain forest: They are found in temperate area with adequate rainfall. These are dominated by
coniferous trees like pines, firs etc.
Evergreen coniferous forest
( Boreal forests):
They are found south of arctic tundra. Here winters are long, cold and dry.
The major trees include pines, fir etc.

Grassland Ecosystem
Tropical grassland Temperate grassland Polar grassland

Tropical grasslands: They occur near the borders of tropical rain forest. In Africa they are called Savannas, which
have tall grasses with scattered shrubs and stunt trees. The savannas have a wide variety of animals
Including zebras, Giraffes, antelopes etc.
Temperate grasslands:
They are usually found on the flat, gentle sloped hills, winters are very cold but summers are
very hot and dry.
In United states and Canada, These grasslands are known as Prairies, in south America as Pampas
In Africa as Velds and in central Europe and Asia as Steppes.
Polar grasslands (arctic tundra :
)They are found in Arctic polar region where severe cold along with strong winds create a harsh
climate. The animals include arctic Wolf, arctic fox, reindeer etc.
Permafrost is found under the soil throughout the year .

Desert Ecosystem
Tropical deserts Temperate deserts cold grassland

Tropical Deserts : They are the driest of all. Windblown sand dunes are very common.e.g Sahara desert in Africa.
Temperate Deserts : They are very hot in summer but cool in winters.e.g. Mojave in south California.
Cold Deserts : They are warm in summers but has cold winters.e.g. Gobi Desert in China.

Deserts are found throughout the world. A lack of water is the primary factor that determines that an area
will be a desert. Deserts are areas that generally average less than25 centimeters (10 inches) of
precipitation per year. When and how precipitation arrives is quite variable in different deserts. Some
deserts receive most of the moisture as snow or rainin the winter months, while in others rain comes in
the form of thundershowers at infrequent intervals. If rain comes as heavy thundershowers, much of the
water does not sink into the ground but runs off into gullies. Also, since the rate of evaporation is
high,plant growth and flowering usually coincide with the periodswhen moisture is available. Deserts are
also likely to be windy.We often think of deserts as hot, dry wastelands devoid oflife. However, many
deserts are quite cool during a major part of the year. Certainly, the Sahara Desert and the deserts of the
southwestern United States and Mexico are hot during much of the year, but the desert areas of the
northwestern UnitedStates and the Gobi Desert in Central Asia can be extremely cold during winter
months and have relatively cool summers. Furthermore,the temperature can vary greatly during a 24-
hourperiod. Since deserts receive little rainfall, it is logical that most will have infrequent cloud
cover.With no clouds to block out the sun, during the day the soil surface and the air above it tend to heat
up rapidly. After the sun has set, the absence of an insulating layer of clouds allows heat energy to be
reradiated from the Earth,and the area cools off rapidly. Cool to cold nights are typical even in “hot”
deserts, especially during the winter months.
Features of Desert Ecosystem

Organisms Another misconception about deserts is that few species of organisms live in the desert. There are many
species, but they typically have low numbers of individuals. For example, a conspicuous feature of deserts is the dispersed
nature of the plants. There is a significant amount of space between them. Similarly, animals do not have large, dense
populations. However, those species that are present are specially adapted to survive in dry, often hot environments. For
example, water evaporates from the surfaces of leaves. As an adaptation to this condition, many desert plants have very
small leaves that allow them to conserve water. Some even lose their leaves entirely during the driest part of the year.
Some, such as cactus, have the ability to store water in their spongy bodies or their roots for use during drier periods. Other
plants have parts or seeds that lie dormant until the rains come. Then they germinate, grow rapidly, reproduce, and die, or
become dormant until the next rains. Even the perennial plants are tied to the infrequent rains. During these times, the
plants are most likely to produce flowers and reproduce. Many desert plants are spiny. The spines discourage large animals
from eating the leaves and young twigs. The desert has many kinds of animals. However, they are often overlooked because
their populations are low, numerous species are of small size, and many are inactive during the hot part of the day. They
also aren’t seen in large, conspicuous groups. Many insects, lizards, snakes, small mammals, grazing mammals, carnivorous
mammals, and birds are common in desert areas. Allot the animals that live in deserts are able to survive with a minimal
amount of water. Some receive nearly all of their water from the moisture in the food they eat. They generally have an
outer skin or cuticle that resists water loss, so they lose little water by evaporation. They also have physiological
adaptations, such as extremely efficient kidneys, that allow them to retain water. They often limit their activities to the
cooler part of the day (the evening), and small mammals may spend considerable amounts of time in underground burrows
during the day, which allows them to avoid extreme temperatures and to conserve water.
Adaptations in Desert ecosystems

Aquatic ecosystem : Aquatic ecosystems are either freshwater or marine. Freshwater ecosystems are either
Lentic or Lotic types.

Aquatic Ecosystem
Pond Ecosystem Lake ecosystems River Ecosystem Oceans

Pond Ecosystem It is a small freshwater ecosystem where water is stagnant.
Ponds may be seasonal in nature. They contain several types of algae, aquatic plants, insects fishes etc
Lake Ecosystem Lakes are usually bigger freshwater bodies with standing water. They have 3 zones:
1. Littoral zone
2. Limnetic zone
3. Profundal zone
The Dal Lake in Srinagar , Loktak lake in Manipur are some examples of Lake ecosystem.

Organisms found in lakes:
a) Planktons
b) Nektons
c) Benthos
d) periphytons
The lakes show Stratification or zonation based on temperature difference.Two distinct zones are formed:
Epilimnion
Hypolimnion

Oligotrophic- low nutrient
Eutrophic-more nutrient
Endemic-ancient lakes e.g Baikal lake in Russia
Desert Salt lakes- high salt concentration
Volcanic lakes-receive magma from volcanic eruption
Types of lakes :Some important types of lakes are

River Ecosystem : Rivers are large streams that flow downward from mountain highlands and flowing through the
plains fall into the sea.
The mountain highland part has cold and clear water rush down as water falls.
In the second phase on the gentle slopes, the waters are warmer and support growth of plants and fishes.
In the third phase, the river waters are rich in biotic diversity.

Ocean Ecosystem : These are gigantic reservoirs of water covering 70% of our earth’s surface.
The oceans have two major life zones:
Coastal zones with relatively warm, nutrient rich shallow water.

Open sea : It is the deeper part of the ocean. It is vertically divided into 3 regions:-
Euphotic zone which receives abundant light
Bathyal zone receives dim light
Abyssal zone is the deep zone. It is around 2000 to 6000 metres deep.

Estuary : An estuary is a partially enclosed area at the mouth of a river where fresh water and salty sea water meet.
Organisms present in estuaries show a wide range of tolerance to temperature and salinity. Such organisms are called
Eurythermal or Euryhaline .
Estuaries are highly productive ecosystems.

1) Pond Skaters Pond skaters walk on the surface of the water. They have adapted
long, splayed, paddle-like legs which allow them to spread their weight over a large surface
area, their feet are covered with tiny hairs which trap air and enable the insect to ‘skate’ on
the surface of the water taking advantage of the surface tension that lies between the water
and the air. The pond skater’s stomach is covered with water-repellent hairs to prevent direct
contact between their body and the water.
2) Freshwater Shrimp Freshwater shrimp have a body that is flattened sideways. They
use their front legs to crawl along the bottom of the pond and swim sideways by moving five
pairs of segmented swimming legs which propel a stream of water over their gills as they
move, allowing them to obtain a constant supply of oxygen.
3) Great Diving Beetle The great diving beetle is an aggressive predator, it has a
streamlined body reducing water friction and fringed jointed legs allowing it to move very fast
through the water to hunt and catch it’s prey
Examples of adaptation in some aquatic organisms

module3Ecosystems.pptx ecology and environment

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