How a Mass Extinction Event Created the Amazon

The Amazon rainforest, home to thousands of species, is primarily composed of flowering plants, or angiosperms, which dominate due to historical events. Initially, the Amazon was filled with ferns and gymnosperms. However, an asteroid impact 66 million years ago triggered the Cretaceous-Paleogene extinction event, altering ecosystems and favoring angiosperms. The impact released phosphorus, benefiting fast-growing plants, and the absence of dinosaurs changed forest dynamics, leading to the closed canopy forests we see today. This mass extinction event paved the way for the Amazon's current biodiversity.

What is the primary reason for the Amazon's biodiversity?

• The dominance of flowering plants

• The presence of large mammals

• The abundance of water bodies

• The variety of bird species

What was the main plant group in the Amazon before flowering plants took over?

• Ferns and gymnosperms

• Cacti

• Mosses

• Algae

What event led to the significant change in plant life in the Amazon?

• A prolonged drought

• A volcanic eruption

• A massive flood

• An asteroid impact

How did the asteroid impact affect gymnosperms?

• It provided them with more sunlight

• It increased their growth rate

• It caused them to become aquatic

• It created conditions unfavorable for their growth

What role did legumes play in the post-extinction Amazon?

• They became the dominant plant species

• They fixed nitrogen, aiding angiosperm growth

• They provided shade for other plants

• They repelled herbivores

Why did the absence of dinosaurs affect the plant composition in the Amazon?

• Dinosaurs fertilized the soil

• Dinosaurs maintained open canopy conditions

• Dinosaurs used to pollinate the plants

• Dinosaurs spread plant seeds

What type of forest did the Amazon become after the extinction event?

• Savanna

• Desert

• Open canopy

• Closed canopy