Lecture Notes: Earth's Prehistoric Life and Evolution

Early Earth and Thea Collision

• Earth 4.4 billion years ago: Toxic, sterile, and meteorite-ridden.
• Thea, another planet, collided with Earth, creating a new world.
  • Smaller chunk of Thea became the Moon.
• Formation of oceans, life began.

Cambrian Period: First Life Forms

• 530 million years ago: Life in oceans, none on land.
• Evolution accelerated in coastal shallows.
• Anomalocaris: First super predator with eyes.
• Evolution of eyes in predators and prey triggered an arms race.
• 80% of creatures developed exoskeletons; early arthropods.
• Haikouichthys: First known vertebrate, ancestor to all back-boned animals.

Evolution of Fish

• Fish evolved into more complex forms with backbones.
• Development of fins, heads, and flexible backbones.
• Cephalaspis: Jawless fish with protective head and scales.
• 100 million years of evolution: Fish evolved complex bodies, first jaws, and limbs.

Transition to Land

• First pioneering plants began appearing on land.
• Fish like Cephalaspis used memory and complex brains to navigate spawning pools.
• Arthropods like Brontoscorpio evolved simple lungs and moved onto land.
• Early amphibians like Hynerpeton evolved to live both in water and on land.

Carboniferous Period: Giant Arthropods

• Oxygen-rich atmosphere led to super-sized arthropods.
• Mesothelae: Giant spider hunting small reptiles.
• Arthropleura: Giant millipede-like arthropod.

Permian Period: Rise of Reptiles

• Dimetrodon: Mammal-like reptile with specialized teeth, developed parental care.
• Reptiles adapted to harsh climates and developed body temperature regulation.
• Edaphosaurus: Herbivorous mammal-like reptiles with sails for temperature regulation.

Mass Extinction and Survival

• Earth experienced volcanic activity, superheating the atmosphere, leading to mass extinction.
• Dicynodon: Early mammal-like reptiles with efficient jaws and hearts.
• Evolution of reptiles continued, leading to the first true reptiles.

Triassic Period: Dawn of Dinosaurs

• Earth began to recover; conifer forests appeared.
• Lystrosaurus: Dominant herbivores.
• Euparkeria: Early ancestor of dinosaurs with bipedal locomotion.
• Proterosuchus: Early crocodile-like predators.
• Migratory behavior and evolution of larger reptiles, leading to the dominance of dinosaurs.

Conclusion: Rise of Dinosaurs

• Early dinosaurs evolved unique abilities that gave them a competitive edge.
• Our mammalian ancestors were reduced to small creatures hiding in the shadows.
• World would belong to dinosaurs for the next 170 million years.