Ecology

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Introduction

• 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

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Introduction

• 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

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Different Habitats
Freshwater Pond
Freshwater Stream
Grassland
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Different Habitats
Mangrove
Rocky Shore
Coral Reef
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What is Environment ?
Composed of 2 components, Physical Factors
Biotic Factors, which influence the lives of
organisms
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Physical Factors

• Temperature
• Light
• Rainfall Humidity
• Wind Speed
• Soil (esp. for plants)
• pH

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Biotic Factors
Consists of all the other organisms living
together in the same habitat
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Energy Flow within an Ecosystem
Tertiary Consumers
Respiration
DECOMPOSITION
Dead remains, excreta, etc
HEAT
Secondary Consumers
Primary Consumers
Producers
SUN
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Food Chain / Food Web

• shows the feeding relationship between organisms

rabbit
snake
green plants
hawk
grasshopper
lizard
toad
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Decomposers

• not shown in food chain
• consist of Bacteria Fungi
• break 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

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Trophic Level
Organism
Type
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Pyramids of Numbers(Examples)
Tertiary Consumers
Secondary Consumers
Primary Consumers
Producers
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Pyramids of Biomass
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Secondary Consumers
50
Primary Consumers
500
Producers
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Energy Lost up a Food Chain

• 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 food
  available

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Pyramids of Biomass
Biomass is the total dry mass of organisms at a
trophic level
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Effects 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

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Effects 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

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DDT Accumulation
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Carbon Cycle
Carbon dioxide in air
absorption photosynthesis
respiration
respiration
organic substances in animals
feeding
organic substances in plants
burning
incomplete decomposition
fossil
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Nitrogen Cycle
nitrifying bacteria (nitrification)
nitrate in soil
ammonia
denitrifying bacteria (denitrification)
putrefying bacteria (decomposition)
nitrogen in air
nitrogen- fixing bacteria
faeces, urine, dead body
absorption photosynthesis
protein in plants
protein in animals
feeding
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Investigation 23.1
Investigation of a Balanced Aquarium
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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.
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Why is it unsuitable to introduce large
carnivores into the glass jar ?
Ans Because they require more food to survive
and they will eat up all the organisms in the
aquarium.
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Describe the appearance of the water snails and
the freshwater plants after a few days if the
aquarium is balanced ?
Ans The water snails and the aquatic plants
will remain healthy even after a few weeks.
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What will happen to the aquarium if it is placed
in darkness all the time ? Why ?
Ans Both the water snails and the freshwater
plants will gradually die since there is no light
for the aquatic plants to carry out
photosynthesis to make food
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What will happen to the aquarium if it is placed
in darkness all the time ? Why ?
Ans so the plants cannot survive without food
supply. As all aquatic plants died, the water
snails also die due to starvation.
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Ecological Independence of Organisms
Predation (Predator-prey relation)
Number
prey
Hare
Lynx
predator
Time
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Ecological Independence of Organisms
Number
Competition (competitors)
the winner
the loser
Time
Cuckoo displacing the hosts egg
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Commensalism

• one gets (physical) benefit, one feels no effect
• organism benefited Commensal
• organism with no effect Host
• easy separate from each other
• eg. barnacle on crab
  (barnacle gets transport)

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Mutualism

• 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

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Mutualism

• e.g.2. Nitrogen-Fixing Bacteria Leguminous
  Plants
• bacteria fix atmospheric nitrogen to nitrogenous
  compounds for the plant
• the plant provides carbohydrates to bacteria

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Parasitism

• parasite obtains benefits (food protection)
• host gets harmful effects
• eg. tapeworm in man (endoparasites)

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