Ecology
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Living Organisms & Their
Environment
Ecology is the study of the various relationships between living
organisms and their environment.
The environment of an organism can be classified into two
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categories- the physical and the biotic environment.
• Light
• Temperature
• Water
• Air
• Mineral Salts and
Salinity
• pH
(acidity/alkalinity)
Factors
making up the
physical
environment
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Light
Light affects both plants and animals.
Green plants require light during photosynthesis to
make food.
Light intensity determines the types of plants and
animals that are found in a habitat.
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Most animals require light.
Angler fishes live in
the ocean where the
water is too deep for
sunlight to penetrate.
Bats and
owl do not
require
light as
they are
well
equipped
to move in
the dark.
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Temperature
• Most plants and animals survive in
temperatures between 0°C and 45ºC
• To survive extreme temperature, most
organisms have adaptive features or
behaviour
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Can you tell which of
these animals live in
cold regions?
Migratory
birds in flight
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Water
• Organisms need water to
survive
• Some organisms are
adapted to living in areas
of limited water supply
• More organism are found
where water is available
Water
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These
organisms
have different
ways of
surviving the
limited water
supply in their
environment.
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Air
Air is a mixture of gases such as nitrogen,
oxygen & carbon dioxide.
Plants require carbon dioxide while most other
organisms require oxygen.
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Land organisms take in oxygen
from air.
Aquatic organisms take in
oxygen dissolved in water.
Mangrove trees have aerial roots that
grow out of oxygen-poor mud. The roots
have tiny pores that allows for gaseous
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exchange to occur.
Mineral Salts & Salinity
Animals obtain mineral salts from the food they eat.
Plants absorb mineral salts from the soil solution.
Mineral salts are required in the manufacture of
substances such as protein, vitamins and
chlorophyll.
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The amount of salt present in water is important
for survival of aquatic organisms.
Some organisms are
adapted for life in the
sea.
Other organisms are
adapted for life in the
streams and freshwater
pond.
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pH (acidity / alkalinity)
pH value of soil solution, freshwater ponds and sea
water determines the types of organisms that can
live in each environment.
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• Freshwater organisms live in an
environment of ~pH 7 (neutral).
• Marine organisms live in an
environment of ~pH 8 (slightly alkaline).
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• Most plants grow well in neutral or
slightly alkaline soils.
• pH of soil determines the type of
mineral salts that the plants can absorb
from the soil.
• Plants cannot absorb mineral salts from
acidic soil solutions.
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Biotic Environment
• Biotic environment refers to all
living organisms in a habitat.
Interactions between organisms:
•Predator-prey relationship
•Parasitism
•Mutualism
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Predator-prey Relationship
• An animal that lives by killing and eating
other animals is called a predator.
• An animal that is killed and eaten by
another is called the prey.
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Parasitism
• Parasitism is a relationship between
two organisms in which the parasite
benefits at the expense of the other. A
parasite normally does some harm to its
host.
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Mutualism
• Mutualism is a relationship between two
organisms in which both benefit from it.
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Ecosystems
An ecosystem
consists of
communities of living
organisms
interacting with one
another and with
their physical
environment.
The Earth is a big ecosystem known as the
biosphere.
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Transfer of Energy in an Ecosystem
Consumers
Decomposers
Producers
Sun is the
ultimate
energy
source
Living Organisms
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Decomposers
•
Break down complex nutrients in
excreta and dead bodies to set
free
1) Carbon dioxide
2) Soluble mineral salts
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Producers
• Green plants make their own food using
carbon dioxide and water in the presence of
sunlight. Light energy is converted to chemical
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energy in the process.
Consumers obtain their energy and
nutrients from other organisms on
which they feed.
tertiary
consumer
secondary
consumer
Each stage in a food
chain is called a
trophic level.
primary consumer
plants
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Food
Web
• Food chains are inter-linked to form a food web.
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Energy Loss in Food Chains
• As much as 90% energy is lost to the
environment from one trophic level to
the next.
• Most of the energy loss takes place
from the producer to the primary
consumer.
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How Is This Energy
Lost?
Times Media CD
->Passes out of
body as faeces
and other
excretory
products
->Lost as heat
during
respiration
Total energy level decreases progressively along the
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food chain.
Nutrient Cycles
• In a stable and balanced ecosystem, no
nutrients are lost.
• In an ecosystem, nutrients can be
recycled but energy that flows through it
is not recyclable.
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Carbon Cycle
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Importance of Carbon Cycle
• Ensures a continuous supply of carbon
dioxide for photosynthesis
• Enables carbon compounds rich in
energy to be supplied to other
organisms in the food chain
• Ensures that carbon dioxide is not lost
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Nitrogen Cycle
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Importance of Nitrogen Cycle
• Keeps the nitrogen level in the
atmosphere constant
• Ensures a continuous supply of nitrates
for green plants to make proteins and
protoplasm
• Enables proteins to be supplied to other
organisms in the food chains
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Keeping Nature’s Balance
• In a balanced and stable ecosystem,
the population sizes of the producers
and consumers remain relatively
constant.
• Any change in the relationship between
two organisms can affect other
organisms directly or indirectly.
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Balance Of Ecosystem Can Be Upset By :
• Introduction of new animals and plants
into the habitat
• Disease outbreaks, which can kill plant
or animal species
• Human activities such as deforestation
and over-fishing
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Conserving the Physical
Environment
Negative effects of human activities
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Our Harmful Effects
• Human activities such as deforestation,
pollution, over-fishing and farming are
responsible for these negative effects.
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Why Do We Need To Protect &
Preserve The Natural Environment?
• Prevents extinction of plant and animal
species
• Prevents global warming and disruption of
natural cycles
• Conservation of tropical rainforests which
serve as sources of food and raw materials
for medicinal drugs and industries
• Protection of marine life
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Miscellaneous
• http://www.ecokids.ca/pub/fun_n_ga
mes/slide_show/index.cfm#
•
•
http://www.ecokidsonline.com/pub/eco_i
nfo/topics/frogs/chain_reaction/
http://www.gould.edu.au/foodwebs/kids_
web.htm
end
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