SCIENCE AND HEALTH 6
Course
Outline (2nd Grading)
1. Ecology and Energy Transfer
Ecosystem
Food Chain, Food Web,
Energy Pyramid
Balance of Nature
Relationships that Exist
in Ecosystem
2. Nutrient Cycles in Ecosystem
Carbon dioxide – Oxygen
Cycle
Carbon Cycle
Nitrogen Cycle
Lesson 1
Relationships That Exist
in Ecosystem
1.
Mutualism – In this kind of relationship, both organisms benefit from each
other.
Ex. flagellates and termites, plants
and animals, flower and bee
2.
Commensalism – In this kind of relationship, one organism benefits from the
relationship while the second organism is unaffected by it.
Ex. sea anemone and clown fish,
coral and fish, orchid and tree
3.
Amensalism – In this kind of relationship, the growth of one organism is
inhibited while the other is unaffected.
Ex. shading effect of the tree on
small plants
4.
Parasitism – This is a relationship between two organisms wherein one organism
(the parasite) benefits for growth and reproduction while the other organism
(the host) is harmed.
Ex. dog and ticks, child and
intestinal worm, plants and aphids
5.
Predation - In this type of relationship, an organism (prey) is hunted and
eaten by a stronger organism (the predator)
Ex. snake and frog, tiger and squirrel,
eagle and rabbit
6.
Competition – This relationship exists when an ecosystem has reached its
carrying capacity. Thus, the organisms compete for food, space, and resources.
Ex. pechay plants and weeds, fish in
an aquarium
Lesson 2
Nutrient Cycles in Ecosystem
No material is lost in a balanced or stable
ecosystem. This is because materials are continually taken from the nonliving
environment and used by living things. Then they are released into the
nonliving environment to be used again by living things. The use and reuse of
materials in an ecosystem is called recycling. This process ensures that an
ecosystem does not run out of materials. Recycling makes an ecosystem
self-sustaining.
Carbon
dioxide and Oxygen Cycle
In the carbon dioxide-oxygen cycle, plants
take in carbon dioxide released by humans and animals. They use this in the
food-making process called photosynthesis.
In return, plants produce oxygen that humans, animals, and plants use in
respiration.
Carbon Cycle
All living things are made of carbon. Carbon
is also a part of the ocean, air, and even rocks. Because the Earth is a
dynamic place, carbon does not stay still. It is on the move!
In the atmosphere, carbon is attached to some
oxygen in a gas called carbon dioxide.
Plants use carbon dioxide and sunlight to make
their own food and grow. The carbon becomes part of the plant. Plants that die
and are buried may turn into fossil fuels made of carbon like coal and oil over
millions of years. When humans burn fossil fuels, most of the carbon quickly
enters the atmosphere as carbon dioxide.
Carbon dioxide is a greenhouse gas and traps
heat in the atmosphere. Without it and other greenhouse gases, Earth would be a
frozen world. But humans have burned so much fuel that there is about 30% more
carbon dioxide in the air today than there was about 150 years ago, and Earth
is becoming a warmer place. In fact, ice cores show us that there is now more
carbon dioxide in the atmosphere than there has been in the last 420,000 years.
Nitrogen Cycle
Plants absorb nitrogen in the form of
nitrates, which are very soluble salts. Nitrates are formed through the
processes of nitrogen fixation, nitrification, and decay. Nitrates are absorbed
by plants from the soil or water. These nitrates are then incorporated by
plants to form proteins and other compounds, which can be spread through the
food chain. When animals eat plants, they get the nitrogen in nitrate form.
When organisms die, their bodies are decomposed by bacteria and fungi. The
decomposition process produces ammonium compounds which dissolve in the soil
and water. By the action of denitrifying bacteria, the nitrates in the water
and soil are converted into gaseous nitrogen and are released into the
atmosphere.
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