Overview
This lecture explains how life on Earth exchanges essential matter (water, carbon, nitrogen, phosphorus) with the environment, emphasizing recycling and surface area-to-volume ratios for efficient matter exchange.
Biosphere and Matter Exchange
- Biosphere 1 is Earth; Biosphere 2 was an experiment in matter recycling.
- Earth receives constant energy from the Sun, but all matter is recycled.
- Life depends on exchanging and recycling matter with the environment.
Essential Types of Matter for Life
- Four key elements: water, carbon, nitrogen, and phosphorus are essential for organisms.
- Matter is recycled in the biosphere through water, carbon, nitrogen, and phosphorus cycles.
Surface Area to Volume Ratio
- Surface area to volume ratio increases as objects get smaller.
- High surface area to volume ratios enhance matter exchange in cells and tissues.
- Root hairs, cell folding, and small cell size maximize nutrient absorption.
Macromolecules and Elemental Needs
- Four major macromolecules: carbohydrates (energy), proteins (structure), lipids (membranes), and nucleic acids (genetic information).
- Carbon is found in all four macromolecules.
- Nitrogen is present in proteins (amino acids) and nucleic acids (nitrogenous bases).
- Phosphorus is found in phospholipids (membranes) and the backbone of DNA/RNA.
The Role and Importance of Water
- Water is a polar molecule, acting as a universal solvent.
- Water is essential for dissolving and transporting molecules, enabling chemical reactions.
Cycles of Matter
- Water cycle: movement of water through ecosystems (mainly through drinking and absorption).
- Carbon cycle: carbon moves as CO₂ in the atmosphere, into organisms via photosynthesis, and out via respiration.
- Nitrogen cycle: bacteria make atmospheric nitrogen usable, plants absorb it, and it's recycled after death.
- Phosphorus cycle: phosphorus is found in rocks, absorbed by plants from soil, and transferred through food webs.
Key Terms & Definitions
- Biosphere — the global ecosystem where all life exists on Earth.
- Surface Area to Volume Ratio — a measure influencing efficiency of matter exchange; increases as size decreases.
- Macromolecule — large molecules essential for life (carbohydrates, proteins, lipids, nucleic acids).
- Solvent — a substance that dissolves other substances; water is the universal solvent.
- Cycle (e.g., Water, Carbon, Nitrogen, Phosphorus) — natural processes recycling essential elements in ecosystems.
Action Items / Next Steps
- Review and diagram the four cycles: water, carbon, nitrogen, phosphorus.
- Understand examples of how surface area impacts nutrient exchange (e.g., root hairs, cell membranes).