energy and the ecosystem igcse
TRANSCRIPT
Energy and the ecosystem
B M Subramanya Swamy M.Sc. B.Ed. CIE Co ordinator & Examination Officer
Kanaan Global School Jakarta
Indonesia [email protected]
Overview of the topic
1.Energy flow
2.Food chains and web
3. Ecological pyramids
4.Nutrient cycle
•Producers/Consumers
•Food chains
•Energy transfers
•Food web
•Pyramid of numbers
•Pyramid of bio mass
•Carbon cycle
• Ecology : Study of how organism interact with each other & with their environment
• Environment – organism live • Environment – divided into abiotic & biotic factor• Abiotic factor-nonliving factor• E.g. edaphic factor, climatic factor & topographical factor• Biotic factor- living organism • E g producer consumer decomposer• Habitat – physical location in which an organism lives
Level of ecological organization • Earth – lump of rock with a thin outer layer of soil, water & air.• Organism occur near boundaries either between soil & air or water &
air• Organism – studied at six different levels –
individual,population,community ecosystem, biome & biosphere• Each species is made up of individual• Guases competitive exclusion principle states- two species cannot
coexist unless there are significant difference in their ecologies. If 2 species attempt to occupy the same niche, they will compete with each other until one is eliminated
• Niche – position of species occupied within its habitat.• Niche includes physical space its interaction with other organism & its
effect on environment • Individual – same species occupying a constitute a population
• Different population in an area interact with each other. These collectively form a community
• Community – named after an obvious feature of the environment– Pine forest community – Woodland community– Grassland community
• Different species of a community together with their non living environment, constitute a ecosystem
• Ecosystem consists of 4 basic element– Abiotic component– Biotic component– Energy & nutrient (support life in ecosystem)
• Ecosystem are open unit & part of a biome• All the life are restricted to a rather narrow zone called the
biosphere
Energy flow
The main energy source on the earth is sun.Solar energy can be tapped by the plants to
make food.Recently we are also able to tap this energy
source using solar panels.
Producers / consumers
• Green plants store solar energy in carbohydrates during photosynthesis.
• They change solar energy into chemical energy to achieve this
• They are producers (autotrophs): capable of producing their own food.
• Consumers (heterotrophs) feed on producers as a source of food.
Some terms associated with energy flow
Terms
Producer
Consumer Herbivore Carnivore Omnivore
Definition
AutotrophsProduces its own food e.g. green plants
HeterotrophsFeeds on producers e.g. animals and man
Feeds on plants e.g. cattle
Feeds on animals e.g. lions
Feeds on plants and animals e.g. crows
Modified from: General Ecology, by David T. Krome
Trophic level: All the organisms that are the same number of food-chain steps from the primary source of energy
Foods chains and webs
Food chains• Producers and consumers play different roles in the
community.• These roles are termed as niches.• The different niches can be classified in various ways
in the community.• When a herbivore eats a plant, and is then eaten by a
carnivore, a chain of events from: based on feeding habits
• The forms the food chain.
Classification of niches in the food chain
Food chain Named Consumer level Tropic level
Phytoplankton Producer Producer 1st trophic level
Mussels Herbivore 1st order consumer
2nd trophic level
Crab Small carnivore 2nd order consumer
3rd trophic level
Man Larger carnivore 3rd order consumer
4th trophic level
Bacteria Decomposer 4th order consumer
5th trophic level
Energy transfers
• Energy flows in one direction along food chain.• Energy is transferred along the food chain.• At the next level, energy is lost..therefore energy supplied from
level to level decreases.• The more levels in the food chain, the lesser the energy at the end
of the chain.• Green plants capture only 1% of solar energy.• 10% of energy at every trophic level is converted into biomass.
Example of a Food Chain
Food Webs• All the food chains in an area make up the food web of the area.
© 2003 John Wiley and Sons Publishers
Food web of a hot spring
Food web
• In reality, predators feed on more than one type of prey.• When several different food chains can be strung together, it
forms a food web.• A food web interconnects several food chains within an
ecosystem.
Ecological pyramids•A graphical representation of the energy, biomass or numbers of organisms at each trophic level.
•Each trophic level forms a tier in the pyramid
•They are called pyramids because of the shape of these graphs.
Pyramid of numbers and biomass
Pyramid of numbers Pyramid of biomass
The base has the largest number of organisms
Represents the dry mass of all the organisms at that tropic level
The number of organisms reduce as you reach the higher tiers of the pyramid
The lengths of the bars estimates the relative biomass
May be upright of inverted May be upright or inverted
An example of a pyramid of numbers
Owl
Snakes
Mice
grass
Pyramid of numbers
Pyramid of Energy:• Shows the energy available at each trophic
level.– The size of the blocks represents the proportion of
productivity– Measured in Joules or Calories
Pyramid of Energy:• Most of the energy available to the community
is in the 1st trophic level.• Only 10-20% of the energy is available to the
next trophic level (≈ 90% lost)
Nutrient cycle
• Nutrients in the environment exist in various forms.• Energy cannot be recycled, but the nutrients can• Carbon is repeatedly recycled within the environment
Carbon cycle•Carbon dioxide occupies about 0.03% by volume of air.
•This amount is sufficient for all plants that photosynthesis
•CO2 is removed from the air by green plants.
•It is replaced through respiration and by the combustion of fossil fuels.
CO2
CO2
Nitrogen cycle • Passage of nitrogen within an ecosystem • Nitrogen cycle is more complex biogeochemical cycle• Atmosphere contain 79% nitrogen gas but only few
micro organism can tap this reservoir.• Nitrogen fixation – nitrogen fixing bacteria • Bacteria free-living or living in root nodules of
leguminous plants• Bacteria converts atmospheric nitrogen to nitrates• Atmospheric nitrogen can also fixed by lightning
• Denitrifying bacteria converts nitrates to nitrogen gas– Bacteria are anaerobic – Process is known as denitrification
• Photosynthetic organisms make use of nitrates to form amino acids & protein, which are in turn eaten by animals
• Protein are broken down to amino acids in animals
• Nitrogen in amino acids is excreted in the form of ammonia or urea • Decomposers breakdown protein molecules in dead animals and plants
• Release nitrogen as ammonia or ammonium compounds- ammonification
• E.g. putrefying bacteria
• Ammonia or ammonium compounds to nitrites & nitrites to nitrates• Process is known as nitrification
N03- &
N02-NH3
N2 in Atmosphere