energy and eco systems

Question 1

Define a producer in an ecosystem.

Answer 1

An organism that synthesizes organic molecules from inorganic molecules using energy (e.g., plants using sunlight in photosynthesis).

Question 2

What is gross primary production (GPP)?

Answer 2

The total amount of chemical energy captured by plants through photosynthesis per unit area per time.

Question 3

What is net primary production (NPP)?

Answer 3

The energy remaining after respiratory losses.

Question 4

Define trophic level.

Answer 4

The position an organism occupies in a food chain, e.g., primary producer, primary consumer.

Question 5

What is the difference between biomass and productivity?

Answer 5

Biomass is the total mass of living material in an area, while productivity is the rate at which biomass is produced.

Question 6

If GPP is 5000 kJ/m²/year and respiratory losses are 1500 kJ/m²/year, calculate NPP.

Answer 6

NPP = GPP - Respiration = 5000 - 1500 = 3500 kJ/m²/year.

Question 7

Calculate the efficiency of energy transfer if a primary consumer consumes 1000 kJ and stores 100 kJ as biomass.

Answer 7

Efficiency = (Energy stored / Energy consumed) × 100 = (100 / 1000) × 100 = 10%.

Question 8

What happens during ammonification?

Answer 8

Saprobionts decompose organic nitrogen (from dead organisms and waste) into ammonium ions.

Question 9

Describe nitrification.

Answer 9

Nitrifying bacteria convert ammonium ions into nitrites (NO₂⁻), and then nitrites into nitrates (NO₃⁻).

Question 10

Explain denitrification.

Answer 10

Denitrifying bacteria convert nitrates into nitrogen gas under anaerobic conditions.

Question 11

Why is energy transfer between trophic levels inefficient?

Answer 11

Energy is lost through respiration, excretion, movement, heat (especially in endotherms), and undigested material.

Question 12

Suggest why food chains rarely exceed four trophic levels.

Answer 12

Insufficient energy is available at higher trophic levels due to energy losses at each level.

Question 13

Farmers often use fertilizers to increase crop yield. Explain how this helps.

Answer 13

Fertilizers add nitrates and phosphates, increasing plant growth by supporting DNA, ATP, and protein synthesis.

Question 14

Describe how energy flows through an ecosystem.

Answer 14

Energy enters via sunlight and is captured by producers through photosynthesis (GPP). NPP supports consumers and decomposers. Energy is lost as heat, movement, and respiration at each trophic level.

Question 15

Explain how agricultural practices increase the efficiency of energy transfer in food chains.

Answer 15

Practices like using pesticides, herbicides, and fertilizers reduce energy losses to pests, weeds, and respiration. Livestock are confined to reduce energy loss through movement.

Question 16

How could a student measure the dry biomass of a plant?

Answer 16

Dry the plant in an oven at a low temperature (e.g., 80°C) until mass remains constant, ensuring water is removed without combusting the material.

Question 17

How is the chemical energy of biomass estimated?

Answer 17

By burning a sample in a calorimeter and measuring the heat released, which heats a known volume of water. Use q = mcΔT to calculate energy.

Question 18

Why might the energy transfer in natural ecosystems differ from that in agricultural systems?

Answer 18

Natural ecosystems have more energy loss to non-human consumers, decomposers, and less human intervention (e.g., fertilizers, pest control).

Question 19

How is the nitrogen cycle linked to the production of proteins in animals?

Answer 19

Plants absorb nitrates from the soil to produce amino acids and proteins. Animals consume plants, transferring nitrogen to build their own proteins.

Question 20

Discuss the impact of deforestation on carbon and nitrogen cycling.

Answer 20

Deforestation reduces photosynthesis, increasing atmospheric CO₂. It also decreases soil nitrogen content due to reduced organic material and erosion.

Question 21

A graph shows biomass decreasing at higher trophic levels. Explain why.

Answer 21

Energy transfer between levels is inefficient, with most energy lost as heat, respiration, and excretion.

Question 22

Why might crops grown in monoculture have a greater NPP than wild plants?

Answer 22

Monoculture reduces competition for resources like light, water, and nutrients, maximizing photosynthesis.

Question 23

Data shows crop yield increasing after phosphate fertilizer use. Explain why.

Answer 23

Phosphate is essential for ATP and nucleic acids, promoting energy transfer and growth.

Question 24

Discuss the environmental impacts of using artificial fertilizers.

Answer 24

Fertilizers can cause eutrophication, where nutrient runoff leads to algal blooms, oxygen depletion, and aquatic life death.

Question 25

Explain how crop rotation helps maintain soil fertility.

Answer 25

Crop rotation includes legumes that fix atmospheric nitrogen, replenishing soil nitrates for subsequent crops.