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Ecology
Basic Concepts
• Species : a group of organism that can interbreed &
produce fertile offspring.(have a common gene pool).
• Habitat: the environment in which species normally
lives (location).
• Population: a group of the organism of the same
species ,living in the same area at the same time.
• Community: a group of populations living &
interacting with each other in an area.
• Ecology: the study of relationships between living
organisms & their environment.
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Environment
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Its everything which surrounds an organism.
It has 4 main components
Hydrosphere (water)
Atmosphere (gases)
Lithosphere (rocks)
Biosphere (all living beings)
The first 3 are abiotic components while the
4th is the Biotic component
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Autotrophs & heterotrophs
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• Autotrophs are the organisms with the capacity to make
their own food.
• Eg.:cynobacteria, Algae,Grass, Trees.
• Hetrotrophs are the organisms which do not have the
capacity to produce their own food.
• Eg.:animals,fish,zooplanktons.
• Three types :
• consumers
• detritivore
• saprotroph
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Detrivores & saprotrophs
• Detrivores are the organism that consumes
dead organic matter.
• Eg.: earthworm, woodlice.
• Saprotrophs are the organisms that live on, or
in, dead organic matter. (digesting the food by
secreting enzymes).
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Food chain & food web
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• A food chain is a sequence of relationships
between trophic levels where each member
feeds on the previous one.
• A food web is a diagram that shows the
feeding relationships in a community. The
arrows indicate the direction of energy flow.
• It’s the interlinking of the food chains.
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• Define trophic level.
(1)
• A trophic level is where an organism is
positioned on a food web.
• Producer
• Primary consumer
• Secondary consumer
• Tertiary consumer
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• Sun is the principal source of energy in
biological systems.
• Green plants absorb only a very small fraction
of (about 10%) of the light energy.
• Light energy converts into chemical energy by
plants.
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10 % Law of energy flow
• Of the total energy entering a particular trophic level,
only 10% is available for the next higher trophic level.
• Grass →
Goat →
Tiger
• 200 Kg →
20Kg
→
2Kg
• Hence short food chains provide more energy to
higher trophic level.
• That’s the reason why vegetarians get more energy
than meat eating people.
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Ecological pyramids
• Pyramid of biomass
• Biomass is the total dry mass of all organism in an unit area.
• Total biomass = biomass of producers + biomass of consumers
+ biomass of decomposers.
• The mass of all the organisms at each step of the
food chain is measured.
• On the basis of the measurement of the dry mass
(at each trophic level) a diagram can be drawn.
• This is known as pyramid of Biomass.
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Pyramid of Number
• This is drawn according
to the number of
organisms at each
trophic level of the
food chain.
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Pyramid Of Energy
• Energy pyramids are formed by measuring
the amount of energy available at each
trophic level in the food chain.
• The energy is measured over a fixed period
of time.
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Pyramid of Energy
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Explain that energy can enter and leave an ecosystem,
but that nutrients must be recycled.
Energy enters as light and usually leaves as heat.
Nutrients do not usually enter an ecosystem and must
be used again and again. Nutrients such as Carbon
dioxide, Nitrogen, and Phosphorus
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Greenhouse Effect
Phenomenon
• The mean global temperature has
risen about 1 degree Celsius since
1856.
• We saw an increase between 1910
and 1940, and from 1970 onwards.
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Greenhouse Effect
Human Activities
• Increased burning of fossil fuels releasing
Greenhouse gases
• Deforestation – less trees to convert CO2 back to
O2
• Other industrial activities that release other
Greenhouse gases
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Greenhouse Effect
Causes
• Light from the sun has short wavelengths and can
pass through most of the atmosphere.
• This sunlight warms the earth which in turn emits
long wave radiation.
• This long wave radiation is bounced back by the
greenhouse gases, such as carbon dioxide,
methane, water vapour, and sulphur dioxide
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Greenhouse Effect
• Flooding of low –lying land
• Melting of glaciers and polar ice
• More frequent storms and
hurricanes
• Changes in weather patterns
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Greenhouse Effect
Measures
•Increase photosynthesis and reduce
emissions by:
•restoring ecosystems where there has been
deforestation or desertification
•spreading nutrients such as iron in nutrientdeficient oceans to encourage algal growth
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Greenhouse Effect
• Reducing energy consumption;
insulation, smaller vehicles, local
grown food instead of transported
• Changing from fossil fuels to solar,
wind, or nuclear
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Carbon cycle
• The carbon cycle includes the interaction of
living organisms and the biosphere through
the processes of photosynthesis, respiration,
fossilization and combustion.
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Populations
Outline how population size can be affected by
natality, immigration, mortality and
emigration.
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Populations
• Natality – offspring are produced and added to
the population
• Mortality – individuals die and are lost from the
population
• Immigration – individuals move into the area
from somewhere else and add to the population
• Emigration – indivuals move out of the area and
are lost from the population
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Populations
Draw a graph showing
the sigmoid (Sshaped) population
growth curve. (1)
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Populations
• Lag phase: population just begins to grow
• Exponential Phase
Population increases exponentially because
the natality rate is higher than the mortality
rate. This is because there is an abundance of
food, and disease and predators are rare.
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Populations
• Transitional Phase
• Difference between natality and mortality rates
are not as great, but natality is still higher so
population continues to grow, but at a slower
rate.
• Food is no longer as abundant due to the
increase in the population size. May also be
increase predation and disease.
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Populations
• Plateau Phase
Natality and mortality are equal so the population
size stays constant.
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Limiting Factors:
shortage of food or other resources
increase in predators
more diseases or parasites
• If a population is limited, then it has reached its
carrying capacity
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Populations
Define carrying capacity.
The maximum population size that can be
supported by the environment
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Populations
List three factors which set limits to population
increase.
Limiting Factors:
• shortage of food or other resources
• increase in predators
• more diseases or parasites
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