DAS B1 Biology Revision: Active Transport, Cycles and Eutrophication

Flashcards covering active transport, decomposition, the carbon cycle, the nitrogen cycle and eutrophication, based on lecture notes.

What role do decomposers play in an ecosystem?

Decomposers recycle nutrients through the abiotic and biotic components of the ecosystem.

Give examples of primary decomposers.

Bacteria and Fungi

What conditions do decomposers work best in?

Warm, moist environments with a large surface area and when oxygen is present (aerobic).

How are root hair cells adapted for absorption?

They have an extension to increase surface area.

What is the difference between osmosis and active transport in root hair cells?

Water is absorbed by osmosis (high to low concentration), while minerals are absorbed by active transport (low to high concentration, requiring energy).

Why does active transport decrease in waterlogged soil?

There is less oxygen available for respiration, which provides the energy needed for active transport.

How is carbon dioxide added to the atmosphere?

Respiration by plants, animals, and decomposers, as well as combustion of fossil fuels.

How is carbon dioxide removed from the atmosphere?

Photosynthesis

What happens to organisms when they die?

They are either decomposed by bacteria and fungi (releasing CO2) or fossilized (releasing carbon during combustion).

What is the role of nitrogen-fixing bacteria?

They convert nitrogen gas in the air to nitrates in the soil.

What is the role of decomposers in the nitrogen cycle?

They convert protein in dead/waste materials to ammonia.

What is the role of nitrifying bacteria?

They convert ammonia to nitrates.

What is the role of denitrifying bacteria?

They convert nitrates (in soil) to nitrogen gas (in the atmosphere).

What conditions favor denitrifying bacteria?

Anaerobic conditions (waterlogged soil with less oxygen).

What is eutrophication?

The nutrient enrichment of waterways, usually from fertiliser runoff or sewage pollution.

List the steps of eutrophication.

Fertiliser/sewage enters the river (nitrates), algae grows rapidly, algae uses up all the nutrients and causes shading, plants beneath die, dead plants/algae are broken down by decomposers (aerobic respiration), aerobic decomposers use up oxygen, fish and invertebrates die.

What is BOD (Biological Oxygen Demand)?

It is high in polluted areas because bacteria (decomposers) use oxygen.