IntroductionIntroduction
Habitat: the place where an organism occurs
Population: a group of organisms of the same species in an area
Community: all population & plants in the same area
IntroductionIntroduction Ecosystem:
a stable, self-supporting system which consists of communities interacting with each other
Ecology: the study of the interactions between living organisms & their environment
What is Environment ?What is Environment ?
Composed of 2 components, Physical Factors & Biotic Factors, which influence the lives of organisms
TemperatureLightRainfall & HumidityWind SpeedSoil (esp. for
plants)pH
Physical FactorsPhysical Factors
Biotic FactorsBiotic Factors
Consists of all the other organisms living together in the same habitat
Energy Flow within an Energy Flow within an EcosystemEcosystem
SUN
Producers
Primary Consumers
Secondary Consumers
Tertiary Consumer
s
DEC
OM
PO
SIT
ION
HEA
T
Resp
irati
on
Dead
rem
ain
s, excre
ta, e
tc
Food Chain / Food WebFood Chain / Food Web• shows the feeding
relationship between organisms
green plants
rabbit snake
hawk
grasshopper lizard
toad
DecomposersDecomposersnot shown in food chainconsist of Bacteria & Fungibreak down organic wastes & dead
bodies of other organisms to simpler compounds which are then absorbed by green plants
significance: enable the recycling of materials within an ecosystem
Trophic Level
Green plant ProducerFirst
Rabbit Primary ConsumerSecond
Snake Secondary Consumer
Third
Hawk Tertiary ConsumerFourth
Organism Type
Pyramids of NumbersPyramids of Numbers(Examples)(Examples)
Producers
Primary Consumers
Secondary Consumers
Tertiary Consumers
• Why is there energy loss ?– Uneaten food– Respiration – Egestion & Excretion
• ∴ solving the food problem by…– consuming organisms in lower trophic levels
– down a level, increase at least 10 times of fo
od available
Energy Lost up a Food ChainEnergy Lost up a Food Chain
Pyramids of BiomassPyramids of Biomass
Biomass is the total dry mass of organisms at a trophic level
500Producers
Primary Consumers
Secondary Consumers
50
1
Effects of DDTEffects of DDT
DDT is an effective pesticide DDT has been used for about 20 years It had been banned for over 20 years But, nowadays, the body of every
people still has DDT
Effects of DDTEffects of DDT Reasons :
– it has excessively long degeneration period (it requires tens of years)
– it is not easy be destroyed by metabolism of living organisms, so it is easily accumulated along the food chain
It killed many predatory birds due to its accumulation to high concentration through the food chain
Carbon CycleCarbon Cycle
Carbon dioxide in air
organic substances in plants
organic substances in animals
absorption & photosynthesis
respiration
fossil
feeding
respiration
burningincomplete
decomposition
Nitrogen CycleNitrogen Cycle
nitrate in soil
protein in plantsprotein in animals
ammonia
nitrogenin air
absorption &photosynthesis
feeding
putrefying bacteria
(decomposition)
faeces, urine, dead body
nitrifying bacteria(nitrification)
denitrifyingbacteria
(denitrification)
nitrogen-fixing
bacteria
Why is it necessary to use tap water which has been standing for a few day ?Ans: Because fresh tap
water contains chlorine which is harmful to organisms in the aquarium.
lid
waterwater
snail freshwater plant
Why is it unsuitable to introduce large carnivores into the glass jar ?Ans: Because they requi
re more food to survive and they will eat up all the organisms in the aquarium.
lid
waterwater
snail freshwater plant
Describe the appearance of the water snails and the freshwater plants after a few days if the aquarium is balanced ?Ans: The water snails an
d the aquatic plants will remain healthy even after a few weeks.
lid
waterwater
snail freshwater plant
What will happen to the aquarium if it is placed in darkness all the time ? Why ?Ans: Both the water snail
s and the freshwater plants will gradually die since there is no light for the aquatic plants to carry out photosynthesis to make food…
lid
waterwater
snail freshwater plant
What will happen to the aquarium if it is placed in darkness all the time ? Why ?Ans: so the plants canno
t survive without food supply. As all aquatic plants died, the water snails also die due to starvation.
lid
waterwater
snail freshwater plant
Ecological Ecological Independence of Independence of
OrganismsOrganismsPredation
(Predator-prey relation)
Time
Number
prey
predator
Hare Lynx
Time
NumberCompetition
(competitors)
the winner
the loser
Cuckoo displacing the host’s egg
Ecological Ecological Independence of Independence of
OrganismsOrganisms
CommensalismCommensalism• one gets (physical) benefit, one feels no e
ffect• organism benefited: Commensal• organism with no effect: Host• easy separate from each other• eg. barnacle on crab
(barnacle gets transport)
• both obtain benefits• not easy separate (even cannot be separated)• e.g.1. lichen (mutualism of specific algae & fungi)
– fungi absorb moisture from air and moist the algae– algae provide carbohydrates for the fungi
MutualismMutualism
• e.g.2. Nitrogen-Fixing Bacteria & Leguminous Plants– bacteria fix atmospheric nitrogen to
nitrogenous compounds for the plant– the plant provides carbohydrates to bacteria
MutualismMutualism
ParasitismParasitism
• parasite obtains benefits (food & protection)
• host gets harmful effects• eg. tapeworm in man (endop
arasites)
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