THE PHOSPHORUS CYCLE for A Level Biology: The importance of mycorrhiza fungus too

Summary

This video explores the phosphorus cycle and its significance to organisms. Phosphorus is essential for life, found in DNA, RNA, ATP, and cell membranes. Unlike carbon and nitrogen, phosphorus doesn't cycle through the atmosphere, but instead is stored in rocks. Mycorrhizae, a symbiotic fungus, helps plants absorb phosphate ions from soil and water, supporting nutrient uptake. The video explains how plants and animals incorporate phosphorus, and how decomposition and excretion return phosphate to ecosystems. Sedimentation and erosion also play roles in this cycle, maintaining the flow of phosphorus in nature.

Takeaways

• 🧬 Phosphorus is crucial for life, being a key component in DNA, RNA, ATP, and the phospholipid bilayer.
• 🌍 The phosphorus cycle differs from carbon and nitrogen cycles because phosphorus does not exist as a gas in the atmosphere; it primarily comes from rocks.
• 🪨 Phosphate ions in rocks are the main source of phosphorus in the environment.
• 🌱 Plants absorb phosphate ions from soil or water through active transport, incorporating them into biological molecules like DNA and phospholipids.
• 🐄 Animals that consume plants then absorb and use these phosphate ions in their own biological molecules.
• 💩 Phosphorus is returned to the environment through animal excretion, particularly guano (bird droppings), which is rich in phosphorus.
• 🦴 Decomposition of animal remains and waste releases phosphate ions back into soil and water.
• ⏳ Over time, phosphate from waste and remains contributes to forming phosphate-rich rocks through erosion and sedimentation.
• 🏞️ Human activities, like adding fertilizers to land, can cause phosphate runoff into oceans, contributing to the phosphorus cycle.
• 🌊 Sedimentation from rivers and oceans over thousands of years creates phosphate-containing rocks, completing the cycle.

Q & A

What is the primary role of phosphorus in organisms?

Phosphorus is found in essential biological molecules such as DNA, RNA, ATP, and the phospholipid bilayer, making it crucial for life.

How does the phosphorus cycle differ from the carbon and nitrogen cycles?

Unlike carbon and nitrogen, phosphorus is not found as a gas in the atmosphere. The main source of phosphorus is as phosphate ions in rocks.

What is the significance of mycorrhizae in the phosphorus cycle?

Mycorrhizae are fungi that form a mutualistic relationship with plant roots, helping the roots to absorb water and mineral ions, including phosphate ions, and in return, the plant provides carbohydrates to the fungi.

How do plants absorb phosphate ions?

Plants absorb phosphate ions through active transport, which allows them to incorporate these ions into their biological molecules like DNA and phospholipids.

What happens to phosphate ions after they are incorporated into plant material?

Phosphate ions in plant material are digested and absorbed by animals that consume the plants, and then they are incorporated into the animals' biological molecules.

What is the role of excretion in the phosphorus cycle?

Excretion, including animal waste and guano from birds, is a source of phosphate ions that can be released back into the environment, contributing to the phosphorus cycle.

How do phosphate ions become part of rocks?

Phosphate ions can become part of rocks through processes like deep deposition of guano and sedimentation, where over time, layers of sediment build up to form rocks containing phosphate ions.

What is the significance of erosion in the phosphorus cycle?

Erosion of rocks that contain phosphate ions releases these ions back into the oceans, rivers, and soil, continuing the cycle.

How do fertilizers and runoff contribute to the phosphorus cycle?

Fertilizers added to land and runoff into the oceans can introduce additional phosphate ions into the environment, affecting the phosphorus cycle.

Why are mycorrhizal associations beneficial for plants?

Mycorrhizal associations are beneficial for plants because the fungi increase the root surface area for water and nutrient absorption, making plants more drought-resistant, and in return, plants provide nutrients to the fungi.

What is the final destination of phosphate ions after they are released from decomposition and erosion?

After decomposition and erosion, phosphate ions can return to the oceans, rivers, and soil, or they can become part of new rocks, thus continuing the phosphorus cycle.