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Chapter 8 :
ecology
BIOLOGY
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ECOLOGY
Is the scientific study of theinteractions of living organisms and
with the physical environment. They cannot exist as separate
entity.
Instead,they are interrelated andform a complex system.
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THE ABIOTIC AND
BIOTIC COMPONENTS
OF THE ENVIRONMENT
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THE ABIOTIC COMPONENT
(NON-LIVING ORGANISMS)Abiotic component determine the population size andAbiotic component determine the population size and
distribution of the biotic component.distribution of the biotic component.
Abiotic component consist of ;Abiotic component consist of ;
The pH valueThe pH value
Light intensityLight intensity
TemperatureTemperature
HumidityHumidity
TopographyTopography
microclimatemicroclimate
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The pH value The pH value of the soil and water has a significant
effect on the distribution of organisms that live in a
habitat.
Aquatic organisms are sensitive to the effects of the
pH of water and may be killed if the changes pH areconsiderable.
Light intensity
The varying intensities of sunlight in a forest result inthe growth of different types of plants.
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Example;
Tall trees form the canopy
Plants such as ferns and vines
Birds,bats and tree frogs
Mosses and animals such as ants andearthworms thriye
Bacteria and fungi decompose organic material
High
intensity
of
sunlight
Low
intensity
of sunlight
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Temperature Most living organisms survive within the temperature
range of 0C-45C.
A drop in a temperature within a certain range usually
results in a decrease in the metabolic activities of
organisms. Temperature higher than 45C usually cause enzymes
to be denatured.however,there are some species of
organisms that can live under extreme
temperatures.exp; thermophilic bacteria.
Aquatic environment undergo less extreme
temperature changes and therefore provide more
stable habitats than terrestrial environment.
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Humidity
Is the effects the rate of water loss by plants andanimals.
When humidity ,water evaporates from the moist
surfaces at faster rate.
Humidity is usually at night but during the day.
Some organisms regulate their activities to prevent
dehydration.
Exp; woodlice are usually found under stones androtting tree stumps.
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Topography Is the physical features of the land which concern the
altitude,gradient and aspect of a region.
Altitude;
A altitude is associated with a atmospheric andtemperature.
Thus, different plants grow at different altitude.
Gradient;
Steep slopes result in rapid drainage & run-off.
Therefore,the soil layer is thinner & dried.Hence, this
area is not a suitable habitat for organisms.
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Aspect;
The slope of mountains facing the direction of wind
receive more rain than the slopes shaded from the
wind.
Thus,the organisms from different slopes of a
mountain are different. In nothern hemisphere,the slopes facing south
receive more sunlight than the valleys & slopes
facing north.
Hence,this will influence the natural vegetation andland-use by human.
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Microclimate Refers to the climate in a microhabitat.microhabitat.
It includes the humidity,temperature,light intensity
and atmospheric conditions in which the organisms
lives. It also influence the number and distribution of
organisms.
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TTHE BIOTIC COMPONENTHE BIOTIC COMPONENT
(LIVING ORGANISMS)(LIVING ORGANISMS)
Consist of;Consist of;
ProducersProducers
ConsumersConsumers
decomposersdecomposers
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Food chain,food web and
trophic levels A food chain shows a sequence of organisms through whichA food chain shows a sequence of organisms through which
energy is transferred.energy is transferred.
Each stage in a food chain is known as a TROPHIC LEVEL.Each stage in a food chain is known as a TROPHIC LEVEL.
Producers occupy the first trophic level while primaryProducers occupy the first trophic level while primary
consumers occupy the second trophic levelconsumers occupy the second trophic level
the food chains in an ecosystem are usually interconnected tothe food chains in an ecosystem are usually interconnected to
form a FOOD WEB.form a FOOD WEB.
Grass
(producers)
Grasshopers
(primary con.)
Frogs
(secondary con.)
Snakes
(tertiary
consumers)
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In a food web,the source of energy is sunlight.green plants
convert solar energy into chemical energy which is stored infood during photosynthesis.
When a primary consumer feeds on the producers,some of
the energy stored in the plants is passed on to the primary
consumers,which later passes it energy to the secondary
consumers.
In this way,energy flows through a food web.
However,not all the energy is transferred to the next trophic
level in a food web.
Some is lost as heat.
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Energy flow in a food web and the pyramid of numbers
Tertiary
consumers
Secondary
consumers
Primary consumers
producers
ENERGY LOST
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