Class 10 Biology - Our Environment

Activities

Activity 13.1: Designing a Human-made Ecosystem (Aquarium)

Aim/Objective: To design and stabilize a self-sustaining human-made ecosystem (aquarium) and observe the nitrogen cycle.

Materials Required:

50L Glass tank (cleansed with salt water, no soap)
45L Dechlorinated water (tap water left in an open bucket for 24 hours)
2.0 kg Washed river sand and 1.0 kg basalt gravel
Low-flow aerator (2.5L/min) and a 15W sponge filter
Aquatic plants: Hydrilla verticillata, Vallisneria spiralis
Biotic components: 4–6 Guppies (Poecilia reticulata) or 2 Goldfish, 2 Freshwater snails (Pila globosa)
Digital Thermometer and pH test kit

Procedure:

Layer the bottom with 2cm of sand followed by 1cm of gravel.
Fill the tank with 45L of dechlorinated water. Install the aerator and filter.
Conditioning Phase: Plant the Hydrilla and Vallisneria. Allow the tank to "cycle" for 10–14 days without fish. This allows beneficial nitrifying bacteria (Nitrosomonas and Nitrobacter) to colonize the filter.
Measure water parameters: Targeted pH 7.0–7.5, Temperature 24°C–28°C.
Introduce fish slowly. Feed exactly 0.5g of flake food twice daily.
Perform a 20% water change (9L) every 7 days to manage nitrate levels.

Scientific Note An aquarium is a model of the Nitrogen Cycle. Fish excrete Ammonia (NH₃), which is highly toxic. Nitrifying bacteria in the filter convert NH₃ into Nitrites (NO₂⁻) and then into less toxic Nitrates (NO₃⁻). Aquatic plants then assimilate these nitrates as nutrients.

Lab Best Practice Never overfeed. Excess food decays at the bottom, causing an "Ammonia Spike" that can deplete dissolved oxygen and lead to mass mortality of the fish population.

Observation:

If the bacterial colony is established, water remains crystal clear. If overfed, an "Algal Bloom" (green water) occurs within 72 hours due to excess phosphate and nitrate.

Conclusion:

A human-made ecosystem requires precise abiotic regulation to support the biotic community.

Activity 13.2: Constructing an Aquatic Food Chain

Aim/Objective: To quantify the transfer of energy across trophic levels in an aquatic environment.

Materials Required:

Microscope and slides (to observe phytoplankton)
Energy Pyramid Template
Data on local pond biomass (estimated)

Procedure:

Collect 50 mL of pond water and observe under a microscope (100x) to identify producers (Phytoplankton like Spirogyra, Volvox).
Identify primary consumers (Zooplankton, small crustaceans like Daphnia).
Identify secondary and tertiary consumers (Small fish, large predatory fish/birds).
Construct a food chain and apply Lindeman's 10% Rule to calculate available energy at each level (assume 10,000 J at the producer level).

Scientific Note In any food chain, only approx. 10% of the energy is transferred to the next trophic level. The remaining 90% is lost as metabolic heat during respiration or remains in undigested matter. This limits most food chains to 3–4 levels.

Observation:

Energy calculation: Producers (10,000 J) → Herbivores (1,000 J) → Primary Carnivores (100 J) → Top Carnivores (10 J).

Explanation:

The pyramid structure of biomass and energy is a direct consequence of this thermodynamic inefficiency. Top predators are always fewer in number because there is insufficient energy to support a larger population.

Conclusion:

Food chains are hierarchical energy conduits where energy availability decreases exponentially at higher levels.

Activity 13.3: Debate on Pesticide Levels in Food

Aim/Objective: To investigate Biomagnification by analyzing pesticide residues (e.g., DDT) in different trophic levels.

Materials Required:

Toxicity reports (ppm - parts per million) for a local water body
Case study data on "Minamata Disease" or "DDT in Bird Shells"

Procedure:

Compare the concentration of a non-biodegradable pesticide across four levels:
- Level 1: Water (0.000003 ppm)
- Level 2: Zooplankton (0.04 ppm)
- Level 3: Small Fish (0.5 ppm)
- Level 4: Fish-eating Birds (25 ppm)
Calculate the "Magnification Factor" between Level 1 and Level 4.

Safety First Non-biodegradable toxins like Mercury and DDT are lipophilic (fat-soluble). They accumulate in human adipose tissue and can act as endocrine disruptors or carcinogens. Minimize consumption of top-level predators from contaminated water bodies.

Explanation:

Biological Magnification occurs because these chemicals cannot be metabolized or excreted. As a consumer eats many organisms from the level below, it "concentrates" all the toxins from those organisms into its own tissues.

Conclusion:

Human-induced chemical pollution is amplified by natural ecological processes, making top-level consumers the most vulnerable.

Activity 13.4: Biodegradability of Household Waste

Aim/Objective: To analyze the enzymatic degradation rates of various organic and synthetic polymers.

Materials Required:

500g Organic waste (Vegetable peels, fruit rinds)
500g Synthetic waste (Polyethylene bags, PVC scraps)
2 Large terracotta pots (20L capacity) filled with garden soil
200 mL Water (applied every 48 hours)
Sieve (5mm mesh)

Procedure:

Bury the organic waste in Pot A and synthetic waste in Pot B at a depth of exactly 15 cm.
Maintain soil moisture at 40% (damp to touch). Keep at a temperature of 25°C–30°C.
Every 15 days for 3 months, excavate the contents, weigh them, and pass them through a sieve to check for structural integrity.

Scientific Note Decomposers secrete extracellular enzymes (like cellulase and protease) to break down natural polymers. Synthetic plastics like Polyethylene have high molecular weight and stable C-C bonds that no known terrestrial enzyme can effectively cleave, leading to environmental persistence.

Observation:

Pot A: Mass reduces by 80% within 45 days; material turns into dark, earthy humus.
Pot B: 0% change in mass or structure even after 90 days.

Conclusion:

The environment's "Self-cleaning" capacity is limited to biological polymers that have corresponding microbial enzymes.

Activity 13.6: Persistence of Non-biodegradable Substances

Aim/Objective: To estimate the environmental half-life of common non-biodegradable pollutants.

Materials Required:

Environmental chemistry database
Samples of "Oxo-biodegradable" vs. standard plastic

Procedure:

Create a "Persistence Timeline" for the following:
- Paper: 2–6 weeks
- Tin cans: 50 years
- Aluminum cans: 200 years
- Plastic bottles (PET): 450 years
- Glass: >1,000,000 years
Research the impact of UV radiation (photodegradation) on plastics and the formation of Microplastics (particles < 5mm).

Lab Best Practice When researching "Biodegradable Plastics" (like PLA), note that they often only degrade in Industrial Composting facilities at 60°C and will remain persistent in a standard home compost pit or the ocean.

Conclusion:

Non-biodegradable waste constitutes a "geological legacy" that alters soil and marine chemistry for centuries.

Activity 13.7: Waste Management at Home and School

Aim/Objective: To perform a "Waste Audit" and calculate the diversion potential through composting and recycling.

Materials Required:

Digital weighing scale (10 kg capacity, 10g precision)
Heavy-duty gloves and masks
3 Segregation bins (Green, Blue, Yellow)

Procedure:

Collect 24 hours of waste from a household of 4 people.
Segregate and weigh:
- Wet Waste: Compostable organics.
- Dry Waste: Recyclable Paper, Plastic, Metal, Glass.
- Hazardous Waste: Batteries, light bulbs, medicine.
Calculate the Diversion Rate = (Weight of Wet + Recyclable Waste) / (Total Weight) × 100.

Observation:

Average urban household waste is approx. 50%–60% organic. diverted effectively, this can reduce landfill loads by more than half.

Conclusion:

Segregation at source is the most critical technical step in sustainable waste management.

Activity 13.8: Local Sewage and Industrial Waste Treatment

Aim/Objective: To investigate the impact of untreated effluents on Dissolved Oxygen (DO) and Biological Oxygen Demand (BOD).

Materials Required:

Water samples from an upstream (clean) and downstream (post-sewage) site
DO Test Kit (Winkler Method)
Secchi disk (to measure turbidity)

Procedure:

Measure the transparency of both samples using a Secchi disk.
Measure the initial Dissolved Oxygen (DO) concentration in mg/L.
Incubate samples in the dark at 20°C for 5 days and measure DO again to calculate the BOD₅.

Scientific Note BOD (Biological Oxygen Demand) is the amount of oxygen required by bacteria to break down organic matter in water. High BOD indicates heavy pollution and leads to Hypoxia (low oxygen), causing fish kills.

Observation:

Downstream samples typically show high turbidity (low Secchi depth) and a significant drop in DO after incubation (High BOD).

Conclusion:

Municipal sewage treatment is vital to prevent Eutrophication and maintain the respiratory capacity of aquatic ecosystems.

Activity 13.9: Hazards of Electronic Waste (E-waste)

Aim/Objective: To identify heavy metal contaminants in discarded electronics and evaluate safe recovery protocols.

Materials Required:

Discarded PCB (Printed Circuit Board) - for visual inspection only
RoHS (Restriction of Hazardous Substances) guidelines

Procedure:

Identify components likely to contain:
- Lead (Pb): Solder on PCBs, CRT glass.
- Mercury (Hg): LCD backlights, switches.
- Cadmium (Cd): Chip resistors, Ni-Cd batteries.
Research the "Leaching" process where acidic rainwater in landfills causes these metals to enter the groundwater (Leachate).

Safety First Never attempt to dismantle or burn e-waste (like cables or batteries) at home. Burning PVC insulation releases Dioxins and Furans, which are highly toxic and persistent organic pollutants (POPs).

Conclusion:

E-waste management requires specialized "Urban Mining" techniques to recover precious metals (Gold, Copper) while sequestering toxic elements.

Class 10 Biology - Our Environment

Activities

Activity 13.1: Designing a Human-made Ecosystem (Aquarium)

Aim/Objective: To design and stabilize a self-sustaining human-made ecosystem (aquarium) and observe the nitrogen cycle.

Materials Required:

50L Glass tank (cleansed with salt water, no soap)
45L Dechlorinated water (tap water left in an open bucket for 24 hours)
2.0 kg Washed river sand and 1.0 kg basalt gravel
Low-flow aerator (2.5L/min) and a 15W sponge filter
Aquatic plants: Hydrilla verticillata, Vallisneria spiralis
Biotic components: 4–6 Guppies (Poecilia reticulata) or 2 Goldfish, 2 Freshwater snails (Pila globosa)
Digital Thermometer and pH test kit

Procedure:

Layer the bottom with 2cm of sand followed by 1cm of gravel.
Fill the tank with 45L of dechlorinated water. Install the aerator and filter.
Conditioning Phase: Plant the Hydrilla and Vallisneria. Allow the tank to "cycle" for 10–14 days without fish. This allows beneficial nitrifying bacteria (Nitrosomonas and Nitrobacter) to colonize the filter.
Measure water parameters: Targeted pH 7.0–7.5, Temperature 24°C–28°C.
Introduce fish slowly. Feed exactly 0.5g of flake food twice daily.
Perform a 20% water change (9L) every 7 days to manage nitrate levels.

Lab Best Practice Never overfeed. Excess food decays at the bottom, causing an "Ammonia Spike" that can deplete dissolved oxygen and lead to mass mortality of the fish population.

Observation:

If the bacterial colony is established, water remains crystal clear. If overfed, an "Algal Bloom" (green water) occurs within 72 hours due to excess phosphate and nitrate.

Conclusion:

A human-made ecosystem requires precise abiotic regulation to support the biotic community.

Activity 13.2: Constructing an Aquatic Food Chain

Aim/Objective: To quantify the transfer of energy across trophic levels in an aquatic environment.

Materials Required:

Microscope and slides (to observe phytoplankton)
Energy Pyramid Template
Data on local pond biomass (estimated)

Procedure:

Collect 50 mL of pond water and observe under a microscope (100x) to identify producers (Phytoplankton like Spirogyra, Volvox).
Identify primary consumers (Zooplankton, small crustaceans like Daphnia).
Identify secondary and tertiary consumers (Small fish, large predatory fish/birds).
Construct a food chain and apply Lindeman's 10% Rule to calculate available energy at each level (assume 10,000 J at the producer level).

Observation:

Energy calculation: Producers (10,000 J) → Herbivores (1,000 J) → Primary Carnivores (100 J) → Top Carnivores (10 J).

Explanation:

The pyramid structure of biomass and energy is a direct consequence of this thermodynamic inefficiency. Top predators are always fewer in number because there is insufficient energy to support a larger population.

Conclusion:

Food chains are hierarchical energy conduits where energy availability decreases exponentially at higher levels.

Activity 13.3: Debate on Pesticide Levels in Food

Aim/Objective: To investigate Biomagnification by analyzing pesticide residues (e.g., DDT) in different trophic levels.

Materials Required:

Toxicity reports (ppm - parts per million) for a local water body
Case study data on "Minamata Disease" or "DDT in Bird Shells"

Procedure:

Compare the concentration of a non-biodegradable pesticide across four levels:
- Level 1: Water (0.000003 ppm)
- Level 2: Zooplankton (0.04 ppm)
- Level 3: Small Fish (0.5 ppm)
- Level 4: Fish-eating Birds (25 ppm)
Calculate the "Magnification Factor" between Level 1 and Level 4.

Explanation:

Biological Magnification occurs because these chemicals cannot be metabolized or excreted. As a consumer eats many organisms from the level below, it "concentrates" all the toxins from those organisms into its own tissues.

Conclusion:

Human-induced chemical pollution is amplified by natural ecological processes, making top-level consumers the most vulnerable.

Activity 13.4: Biodegradability of Household Waste

Aim/Objective: To analyze the enzymatic degradation rates of various organic and synthetic polymers.

Materials Required:

500g Organic waste (Vegetable peels, fruit rinds)
500g Synthetic waste (Polyethylene bags, PVC scraps)
2 Large terracotta pots (20L capacity) filled with garden soil
200 mL Water (applied every 48 hours)
Sieve (5mm mesh)

Procedure:

Bury the organic waste in Pot A and synthetic waste in Pot B at a depth of exactly 15 cm.
Maintain soil moisture at 40% (damp to touch). Keep at a temperature of 25°C–30°C.
Every 15 days for 3 months, excavate the contents, weigh them, and pass them through a sieve to check for structural integrity.

Observation:

Pot A: Mass reduces by 80% within 45 days; material turns into dark, earthy humus.
Pot B: 0% change in mass or structure even after 90 days.

Conclusion:

The environment's "Self-cleaning" capacity is limited to biological polymers that have corresponding microbial enzymes.

Activity 13.6: Persistence of Non-biodegradable Substances

Aim/Objective: To estimate the environmental half-life of common non-biodegradable pollutants.

Materials Required:

Environmental chemistry database
Samples of "Oxo-biodegradable" vs. standard plastic

Procedure:

Create a "Persistence Timeline" for the following:
- Paper: 2–6 weeks
- Tin cans: 50 years
- Aluminum cans: 200 years
- Plastic bottles (PET): 450 years
- Glass: >1,000,000 years
Research the impact of UV radiation (photodegradation) on plastics and the formation of Microplastics (particles < 5mm).

Conclusion:

Non-biodegradable waste constitutes a "geological legacy" that alters soil and marine chemistry for centuries.

Activity 13.7: Waste Management at Home and School

Aim/Objective: To perform a "Waste Audit" and calculate the diversion potential through composting and recycling.

Materials Required:

Digital weighing scale (10 kg capacity, 10g precision)
Heavy-duty gloves and masks
3 Segregation bins (Green, Blue, Yellow)

Procedure:

Collect 24 hours of waste from a household of 4 people.
Segregate and weigh:
- Wet Waste: Compostable organics.
- Dry Waste: Recyclable Paper, Plastic, Metal, Glass.
- Hazardous Waste: Batteries, light bulbs, medicine.
Calculate the Diversion Rate = (Weight of Wet + Recyclable Waste) / (Total Weight) × 100.

Observation:

Average urban household waste is approx. 50%–60% organic. diverted effectively, this can reduce landfill loads by more than half.

Conclusion:

Segregation at source is the most critical technical step in sustainable waste management.

Activity 13.8: Local Sewage and Industrial Waste Treatment

Aim/Objective: To investigate the impact of untreated effluents on Dissolved Oxygen (DO) and Biological Oxygen Demand (BOD).

Materials Required:

Water samples from an upstream (clean) and downstream (post-sewage) site
DO Test Kit (Winkler Method)
Secchi disk (to measure turbidity)

Procedure:

Measure the transparency of both samples using a Secchi disk.
Measure the initial Dissolved Oxygen (DO) concentration in mg/L.
Incubate samples in the dark at 20°C for 5 days and measure DO again to calculate the BOD₅.

Observation:

Downstream samples typically show high turbidity (low Secchi depth) and a significant drop in DO after incubation (High BOD).

Conclusion:

Municipal sewage treatment is vital to prevent Eutrophication and maintain the respiratory capacity of aquatic ecosystems.

Activity 13.9: Hazards of Electronic Waste (E-waste)

Aim/Objective: To identify heavy metal contaminants in discarded electronics and evaluate safe recovery protocols.

Materials Required:

Discarded PCB (Printed Circuit Board) - for visual inspection only
RoHS (Restriction of Hazardous Substances) guidelines

Procedure:

Identify components likely to contain:
- Lead (Pb): Solder on PCBs, CRT glass.
- Mercury (Hg): LCD backlights, switches.
- Cadmium (Cd): Chip resistors, Ni-Cd batteries.
Research the "Leaching" process where acidic rainwater in landfills causes these metals to enter the groundwater (Leachate).

Conclusion:

E-waste management requires specialized "Urban Mining" techniques to recover precious metals (Gold, Copper) while sequestering toxic elements.

Class 10 Biology - Our Environment

Class 10 Biology - Our Environment

Activities

Activity 13.1: Designing a Human-made Ecosystem (Aquarium)

Activity 13.2: Constructing an Aquatic Food Chain

Activity 13.3: Debate on Pesticide Levels in Food

Activity 13.4: Biodegradability of Household Waste

Activity 13.6: Persistence of Non-biodegradable Substances

Activity 13.7: Waste Management at Home and School

Activity 13.8: Local Sewage and Industrial Waste Treatment

Activity 13.9: Hazards of Electronic Waste (E-waste)

On this page

Class 10 Biology - Our Environment

Class 10 Biology - Our Environment

Activities

Activity 13.1: Designing a Human-made Ecosystem (Aquarium)

Activity 13.2: Constructing an Aquatic Food Chain

Activity 13.3: Debate on Pesticide Levels in Food

Activity 13.4: Biodegradability of Household Waste

Activity 13.6: Persistence of Non-biodegradable Substances

Activity 13.7: Waste Management at Home and School

Activity 13.8: Local Sewage and Industrial Waste Treatment

Activity 13.9: Hazards of Electronic Waste (E-waste)

On this page