Rucete ✏ Campbell Biology In a Nutshell
Unit 5 THE EVOLUTIONARY HISTORY OF BIOLOGICAL DIVERSITY — Concept 30.4 Human Welfare Depends on Seed Plants
Seed plants are essential to nearly every aspect of human life—providing food, medicine, materials, and energy. But despite their value, plant diversity is declining rapidly due to human activity. Preserving seed plant diversity is critical for both ecological stability and future innovation.
Seed Plants in Human Life
- Food: Most of the world’s calories come from angiosperms, especially six major crops:
- Maize, rice, wheat, potatoes, cassava, and sweet potatoes supply ~80% of global caloric intake.
- Livestock feed depends on grains (5–7 kg of grain per 1 kg of beef).
- Modern crops result from thousands of years of artificial selection.
- Example: Maize evolved from the wild grass teosinte through just a few gene changes.
- Beverages and spices also come from angiosperms:
- Tea (leaves), coffee (seeds), chocolate (cacao seeds), spices (saffron, cinnamon, black pepper, basil, etc.)
- Wood and construction materials:
- Xylem tissue = wood.
- Used for fuel, paper (from conifer pulp), and building materials worldwide.
- Medicines:
- ~25% of prescription drugs in the U.S. contain active compounds from plants.
- Examples of medicinal plants:
- Foxglove → Digitalin (heart medication)
- Pacific yew → Taxol (ovarian cancer treatment)
- Periwinkle → Vinblastine (leukemia drug)
- Willow bark → Salicin (precursor to aspirin)
- Rainforests may hold untapped medicinal resources, many still undiscovered.
Threats to Plant Diversity
- Deforestation and land conversion, especially in the tropics, are driving plant species to extinction:
- Over 15 million acres of tropical forest are cleared yearly.
- At current rates, all tropical forests could vanish within 175 years.
- This reduces CO₂ absorption via photosynthesis and accelerates global warming.
- Species loss is irreversible.
- Extinction removes genetic information forever.
- Also affects animals and insects that depend on plant biodiversity.
- Only a tiny fraction of plant species have been studied for potential human use:
- ~325,000 known plant species
- Most of our food comes from only two dozen seed plant species
- Fewer than 5,000 have been studied for medicinal properties
- Biodiversity loss could trigger a mass extinction on par with the Permian or Cretaceous events.
In a Nutshell
Seed plants are vital to human survival—feeding us, healing us, and building our homes. Yet, we’re losing plant diversity faster than we can explore or preserve it. Protecting these species is not just an ethical choice, but a practical one, essential for sustaining life and discovering future cures.