Biology- Chapter 25 "The History of Life on Earth"

Fossils

provide evidence of evolutionary changes.

Radiometric dating

uses isotopes like carbon-14 for recent fossils and uranium-238 for older fossils.

Origin of Life (~3.5 bya)

First cells were prokaryotic and likely anaerobic.

Stromatolites (origin of life)

ancient bacterial mats.

Oxygen Revolution (~2.4 bya)

Cyanobacteria produced oxygen via photosynthesis. Oxygen accumulated, leading to extinction of anaerobes.

First Eukaryotes (~1.8 bya) - Endosymbiosis theory

Mitochondria and chloroplasts originated from engulfed prokaryotes.

Cambrian Explosion (~535-525 mya)

Rapid diversification of animal phyla. Emergence of hard-bodied organisms and predators.

What significant relationship did plants form around 500 million years ago?

Plants formed symbiotic relationships with fungi (mycorrhizae).

Which major animal groups were the first to colonize land?

Arthropods and tetrapods.

Permian Extinction (~252 mya)

Volcanic eruptions led to climate change, wiping out 96% of marine species.

Cretaceous Extinction (~66 mya)

Likely caused by asteroid impact (Chicxulub crater), leading to dinosaur extinction.

Adaptive Radiations

Mass extinctions and new ecological opportunities drive bursts of speciation (e.g., mammals after dinosaurs).