Trophic Levels: These represent the feeding positions in a food chain or web.

Organisms
are classified based on their source of energy.
Energy Flow:
 Energy enters the ecosystem through the sun.
 Producers (Autotrophs) capture solar energy and convert it into chemical energy
through photosynthesis.
 Energy flows from one trophic level to the next, but only 10% of the energy is
transferred at each step.
 The remaining 90% is lost as heat during metabolic processes (e.g., respiration).

Biomass and Energy Pyramid:

 The amount of available energy and biomass decreases as it moves up the pyramid.
 Producers have the most energy, while top predators have the least.

Example Food Chain:

Sun → Grass (Producer) → Grasshopper (Primary Consumer) → Frog (Secondary Consumer) →
Snake (Tertiary Consumer) → Eagle (Top Predator)
Producers:
 Grass, algae, or phytoplankton
 Make their own food using sunlight through photosynthesis

Primary Consumers:
 Herbivores (plant-eaters)
 Examples: rabbits, deer, grasshoppers

Secondary Consumers:
 Carnivores that eat herbivores
 Examples: frogs, foxes

Tertiary Consumers:
 Carnivores that eat other carnivores
 Examples: snakes, eagles

Decomposers:
 Fungi, bacteria, and worms
 Break down dead organisms and return nutrients to the soil

Material cycling involves the recycling of nutrients (carbon, nitrogen, and water) through
ecosystems.
Organisms play different roles:
 Producers:
o Capture solar energy and convert it into food (glucose).
o Example: Plants absorb CO₂ during photosynthesis and release O₂.
 Consumers:
oObtain energy by eating other organisms.
oRelease CO₂ into the atmosphere through cellular respiration.
 Decomposers:
 o Break down dead organisms and release nutrients back into the soil.
o Essential for nutrient recycling.
o Examples: Bacteria, fungi, and earthworms.

Material Cycling in Action:

1. Carbon Cycle:

o Plants absorb CO₂ → Animals eat plants → Animals respire, releasing CO₂ →
Decomposers break down dead organisms, releasing CO₂.
2. Nitrogen Cycle:

o Bacteria convert atmospheric nitrogen (N₂) into nitrates (usable by plants).

o Plants absorb nitrates → Animals eat plants → Decomposers break down waste,
returning nitrogen to the soil.
Matter Cycles:
 Unlike energy, which flows in one direction, matter is recycled in ecosystems.
Water Cycle:
 Evaporation: Water changes from liquid to gas due to heat.
 Condensation: Water vapor cools and forms clouds.
 Precipitation: Water falls as rain, snow, or hail.
 Transpiration: Plants release water vapor through their leaves.
Carbon-Oxygen Cycle:

 Plants absorb CO₂ during photosynthesis and release O₂.

 Animals breathe in O₂ and release CO₂ during respiration.
Nitrogen Cycle:
 Nitrogen fixation: Bacteria convert nitrogen gas into usable forms (nitrates).
 Plants absorb nitrates → Animals eat plants → Decomposers return nitrogen to the
soil.
Energy Flow:
 Moves through the trophic levels but decreases by 90% as heat at each level.
 Only 10% of the energy is transferred to the next level.
Roles of Organisms in Material Cycling:
 Producers: Convert sunlight into food.
 Consumers: Obtain energy by eating other organisms.
 Decomposers: Break down dead matter and recycle nutrients.
Material Cycles:
 Matter cycles continuously through biogeochemical processes (water, carbon,
nitrogen cycles).
 Decomposers play a crucial role in nutrient recycling.

Assessment
1. What is the main source of energy for most ecosystems?
A. Plants
 B. Sun
C. Water
D. Soil

2. In an ecosystem, which group contains the most energy?

A. Producers
B. Primary consumers
C. Secondary consumers
D. Tertiary consumers

3. What happens to the energy that is NOT transferred to the next trophic level?
A. It is destroyed.
B. It is stored in the soil.
C. It is lost as heat.
D. It is converted into matter.

4. In a food chain, which organism is a primary consumer?

A. Snake
B. Eagle
C. Grass
D. Rabbit

5. What percentage of energy is typically transferred from one trophic level to the next?
A. 100%
B. 50%
C. 10%
D. 1%

6. Which organism is a tertiary consumer in the following food chain?

Grass → Grasshopper → Frog → Snake → Eagle
A. Grass
B. Frog
C. Snake
D. Eagle

7. What is the primary role of decomposers in the ecosystem?

A. Produce food
B. Recycle nutrients
C. Store energy
D. Hunt prey

8. What type of consumer feeds on both plants and animals?

A. Herbivore
B. Carnivore
C. Omnivore
D. Decomposer

9. In an energy pyramid, which trophic level contains the LEAST energy?

A. Producers
B. Primary consumers
C. Secondary consumers
D. Tertiary consumers

10.Which term refers to the total mass of organisms at each trophic level?
A. Energy flow
 B. Biomass
C. Photosynthesis
D. Decomposition

11.Which organisms are responsible for returning nutrients to the soil?

A. Herbivores
B. Carnivores
C. Decomposers
D. Producers

12.What role do producers play in the carbon cycle?

A. Absorb nitrogen from the soil
B. Release oxygen through respiration
C. Take in carbon dioxide during photosynthesis
D. Decompose dead organisms

13.Which process releases carbon dioxide into the atmosphere?

A. Photosynthesis
B. Transpiration
C. Cellular respiration
D. Nitrogen fixation

14.What is the role of nitrogen-fixing bacteria in the nitrogen cycle?

A. Decompose dead matter
B. Convert nitrogen gas into nitrates
C. Absorb carbon dioxide
D. Release oxygen

15.Which process do plants use to return water to the atmosphere?

A. Condensation
B. Precipitation
C. Transpiration
D. Decomposition

16.Which of the following organisms recycles nutrients by breaking down dead plants and
animals?
A. Grass
B. Fungi
C. Tiger
D. Rabbit

17.Which element is cycled through the atmosphere, plants, animals, and decomposers?
A. Oxygen
B. Nitrogen
C. Carbon
D. All of the above

18.In the nitrogen cycle, what is the process of converting nitrates into nitrogen gas?
A. Nitrogen fixation
B. Nitrification
C. Denitrification
D. Combustion

19.How do herbivores contribute to the carbon cycle?

A. They release oxygen.
 B. They decompose organic matter.
C. They release carbon dioxide during respiration.
D. They store carbon in their bodies.

20.What is the role of plants in the oxygen-carbon dioxide cycle?

A. Release nitrogen gas
B. Store oxygen in the soil
C. Take in carbon dioxide and release oxygen
D. Absorb oxygen and release carbon dioxide

21.What is the process by which water changes from liquid to gas?

A. Precipitation
B. Condensation
C. Evaporation
D. Decomposition

22.Which process in the water cycle forms clouds?

A. Evaporation
B. Condensation
C. Precipitation
D. Transpiration

23.Which cycle involves the movement of carbon, nitrogen, and water through the
ecosystem?
A. Energy cycle
B. Biogeochemical cycle
C. Decomposition cycle
D. Photosynthesis cycle

24.During which part of the water cycle does water return to the ground?
A. Transpiration
B. Condensation
C. Precipitation
D. Evaporation

25.What gas do plants release during photosynthesis?

A. Carbon dioxide
B. Nitrogen
C. Oxygen
D. Methane

26.In the water cycle, what happens during transpiration?

A. Plants absorb water.
B. Water changes into ice.
C. Plants release water vapor.
D. Water returns to the soil.

27.Which of the following processes adds nitrogen to the soil?

A. Respiration
B. Decomposition
C. Transpiration
D. Photosynthesis

28.Which term describes the continuous movement of water between the atmosphere and
Earth?
 A. Water cycle
B. Nitrogen cycle
C. Carbon cycle
D. Decomposition cycle

29.Which process adds carbon dioxide to the atmosphere?

A. Photosynthesis
B. Combustion
C. Condensation
D. Transpiration

30.What role do plants play in the water cycle?

A. Absorb water through their roots
B. Store nitrogen
C. Release oxygen
D. Release carbon dioxide

Assessment (Answer Key)

1. What is the main source of energy for most ecosystems?
A. Plants
B. Sun
C. Water
D. Soil
Explanation: The Sun is the primary energy source for most ecosystems. Plants
(producers) use solar energy for photosynthesis, which drives the energy flow through
trophic levels.

2. In an ecosystem, which group contains the most energy?

A. Producers
 B. Primary consumers
C. Secondary consumers
D. Tertiary consumers
Explanation: Producers (plants, algae) have the most energy because they directly
absorb solar energy and convert it into chemical energy (glucose). As energy moves up
the trophic levels, it decreases.

3. What happens to the energy that is NOT transferred to the next trophic level?
A. It is destroyed.
B. It is stored in the soil.
C. It is lost as heat.
D. It is converted into matter.
Explanation: During metabolic processes (e.g., respiration), 90% of the energy is lost
as heat, leaving only 10% available for the next level.

4. In a food chain, which organism is a primary consumer?

A. Snake
B. Eagle
C. Grass
D. Rabbit
Explanation: Primary consumers are herbivores that feed on plants (producers). In
this example, the rabbit eats grass, making it a primary consumer.

5. What percentage of energy is typically transferred from one trophic level to the next?
A. 100%
B. 50%
C. 10%
D. 1%
Explanation: According to the 10% Rule, only 10% of the energy is passed on to the
next trophic level, while 90% is lost as heat.

6. Which organism is a tertiary consumer in the following food chain?

Grass → Grasshopper → Frog → Snake → Eagle
A. Grass
B. Frog
C. Snake
D. Eagle
Explanation: Tertiary consumers eat secondary consumers. In this food chain, the
eagle is at the top, making it the tertiary consumer.

7. What is the primary role of decomposers in the ecosystem?

A. Produce food
B. Recycle nutrients
C. Store energy
D. Hunt prey
Explanation: Decomposers (e.g., fungi, bacteria) break down dead organisms and
return nutrients (nitrogen, carbon) to the soil.

8. What type of consumer feeds on both plants and animals?

A. Herbivore
B. Carnivore
C. Omnivore
D. Decomposer
Explanation: Omnivores eat both plants and animals. Examples include bears,
humans, and raccoons.
9. In an energy pyramid, which trophic level contains the LEAST energy?
A. Producers
B. Primary consumers
C. Secondary consumers
D. Tertiary consumers
Explanation: Tertiary consumers (top predators) receive the least energy because
most of the energy is lost as heat at each trophic level.

10.Which term refers to the total mass of organisms at each trophic level?
A. Energy flow
B. Biomass
C. Photosynthesis
D. Decomposition
Explanation: Biomass refers to the total mass of living organisms in a specific
trophic level. Biomass decreases as you move up the food chain.

11.Which organisms are responsible for returning nutrients to the soil?

A. Herbivores
B. Carnivores
C. Decomposers
D. Producers
Explanation: Decomposers break down dead organisms and release nutrients
(carbon, nitrogen) back into the soil.

12.What role do producers play in the carbon cycle?

A. Absorb nitrogen from the soil
B. Release oxygen through respiration
C. Take in carbon dioxide during photosynthesis
D. Decompose dead organisms
Explanation: During photosynthesis, plants absorb CO₂ from the atmosphere and
produce oxygen.

13.Which process releases carbon dioxide into the atmosphere?

A. Photosynthesis
B. Transpiration
C. Cellular respiration
D. Nitrogen fixation
Explanation: During cellular respiration, organisms release CO₂ as they break down
glucose for energy.

14.What is the role of nitrogen-fixing bacteria in the nitrogen cycle?

A. Decompose dead matter
B. Convert nitrogen gas into nitrates
C. Absorb carbon dioxide
D. Release oxygen
Explanation: Nitrogen-fixing bacteria convert N₂ gas into usable nitrates for plants.

15.Which process do plants use to return water to the atmosphere?

A. Condensation
B. Precipitation
C. Transpiration
D. Decomposition
Explanation: Transpiration is the process where plants release water vapor through
their leaves.
16.Which of the following organisms recycles nutrients by breaking down dead plants and
animals?
A. Grass
B. Fungi
C. Tiger
D. Rabbit
Explanation: Fungi are decomposers that recycle nutrients by breaking down dead
matter.

17.Which element is cycled through the atmosphere, plants, animals, and decomposers?
A. Oxygen
B. Nitrogen
C. Carbon
D. All of the above
Explanation: Carbon, nitrogen, and oxygen cycle through ecosystems, being used
and reused by organisms.

18.In the nitrogen cycle, what is the process of converting nitrates into nitrogen gas?
A. Nitrogen fixation
B. Nitrification
C. Denitrification
D. Combustion
Explanation: Denitrification releases N₂ gas back into the atmosphere.

19.How do herbivores contribute to the carbon cycle?

A. They release oxygen.
B. They decompose organic matter.
C. They release carbon dioxide during respiration.
D. They store carbon in their bodies.
Explanation: Herbivores play a key role in the carbon cycle by consuming plants (which
store carbon) and then releasing carbon dioxide (CO₂) during cellular respiration.
When herbivores breathe, they convert the glucose they obtained from plants into energy,
releasing CO₂ as a byproduct.

20.What is the role of plants in the oxygen-carbon dioxide cycle?

A. Release nitrogen gas
B. Store oxygen in the soil
C. Take in carbon dioxide and release oxygen
D. Absorb oxygen and release carbon dioxide
Explanation: Plants participate in the oxygen-carbon dioxide cycle through
photosynthesis. During this process, they absorb carbon dioxide (CO₂) from the
atmosphere and release oxygen (O₂) as a byproduct. This maintains the balance of
gases in the atmosphere, providing oxygen for animals and humans.

21.What is the process by which water changes from liquid to gas?

A. Precipitation
B. Condensation
C. Evaporation
D. Decomposition
Explanation: Evaporation is the process where liquid water is heated by the Sun and
changes into water vapor. This vapor rises into the atmosphere, forming part of the
water cycle.
22.Which process in the water cycle forms clouds?
A. Evaporation
B. Condensation
C. Precipitation
D. Transpiration
Explanation: Condensation occurs when water vapor cools in the atmosphere and
turns into tiny liquid droplets, forming clouds. These droplets can eventually combine
and fall as precipitation.

23.Which cycle involves the movement of carbon, nitrogen, and water through the
ecosystem?
A. Energy cycle
B. Biogeochemical cycle
C. Decomposition cycle
D. Photosynthesis cycle
Explanation: The biogeochemical cycle refers to the continuous movement of carbon,
nitrogen, water, and other elements through the atmosphere, biosphere,
hydrosphere, and lithosphere. These cycles are essential for maintaining ecosystem
balance.

24.During which part of the water cycle does water return to the ground?
A. Transpiration
B. Condensation
C. Precipitation
D. Evaporation
Explanation: Precipitation is the process by which water falls back to the ground from
the atmosphere in the form of rain, snow, sleet, or hail. This replenishes bodies of water
and groundwater reserves.

25.What gas do plants release during photosynthesis?

A. Carbon dioxide
B. Nitrogen
C. Oxygen
D. Methane
Explanation: During photosynthesis, plants absorb carbon dioxide (CO₂) and, using
sunlight, convert it into glucose and oxygen (O₂). The oxygen is released into the
atmosphere, which is essential for animal and human respiration

26.In the water cycle, what happens during transpiration?

A. Plants absorb water.
B. Water changes into ice.
C. Plants release water vapor.
D. Water returns to the soil.
Explanation: Transpiration is the process where plants release water vapor into the
atmosphere through their stomata (small pores on leaves). This contributes to the water
cycle and helps regulate temperature.

27.Which of the following processes adds nitrogen to the soil?

A. Respiration
B. Decomposition
C. Transpiration
D. Photosynthesis
Explanation: During decomposition, bacteria and fungi break down dead plants and
animals, releasing nitrogen compounds into the soil. This makes nitrogen available for
plants to use.
28.Which term describes the continuous movement of water between the atmosphere and
Earth?
A. Water cycle
B. Nitrogen cycle
C. Carbon cycle
D. Decomposition cycle
Explanation: The water cycle describes the continuous movement of water between
the atmosphere, land, and oceans through processes such as evaporation,
condensation, precipitation, and transpiration.

29.Which process adds carbon dioxide to the atmosphere?

A. Photosynthesis
B. Combustion
C. Condensation
D. Transpiration
Explanation: Combustion is the burning of fossil fuels or organic matter, which
releases carbon dioxide (CO₂) into the atmosphere. This process contributes to the
carbon cycle.

30.What role do plants play in the water cycle?

A. Absorb water through their roots
B. Store nitrogen
C. Release oxygen
D. Release carbon dioxide
Explanation: Plants absorb water from the soil through their roots. This water is
transported throughout the plant and released as vapor through transpiration,
contributing to the water cycle.

Activity:
Mammalia (a mammal under chordata)
Panthera (a mammal under Felidae) Animalia (a kingdom under Eukarya)
Panthera leo (scientific name of a lion under the genus)
Chordata (a mammal under Animalia)
Felidae (a mammal under Carnivora)
Carnivora (a mammal under Mammalia)
Eukarya (The domain, possesses with true nucleus)

Daucus carota L. (scientific name of a carrot)

Magnoliophyta (a plant under Kingdom Plantae)
Eukarya (The domain, possesses with true nucleus)
Magnoliopsida (a seed plant under Magnoliophyta)
Daucus (a seed plant under Apiaceae)
Plantae (a kingdom under Eukarya)
Apiales (a seed plant under Magnoliopsida)
Apiaceae (a seed plant under Apiales)

Amoebidae (an amoeba under Amoebida)

Amoebozoa (an amoeba under Protista)
Eukarya (The domain, possesses with true nucleus)
Amoebida (an amoeba under Tubulinea)
Amoeba proteus (scientific name of amoeba)
Protista (a kingdom under Eukarya)
Tubulinea (an amoeba under Amoebozoa)
Amoeba (an amoeba under Amoebidae)