Evolution

The Cretaceous-Paleogene (K-Pg) extinction event 66 million years ago did not only kill non-avian dinosaurs — it eliminated approximately 75% of all species on Earth, including many marine reptiles (mosasaurs, plesiosaurs), flying pterosaurs, ammonites, and countless plant and invertebrate species. Survivors included small mammals, birds, crocodilians, turtles, snakes, and frogs — groups that could shelter underground, burrow, or tolerate the sudden darkness and cold.

For decades, dinosaurs were assumed to be cold-blooded like modern reptiles. However, evidence from bone growth rings, feather insulation, and metabolic studies now shows that many dinosaurs — particularly theropods and ornithopods — had elevated metabolic rates and could regulate body temperature. A 2014 study in Science placed dinosaurs metabolically between cold-blooded reptiles and fully warm-blooded mammals.

Modern birds are not merely dinosaur relatives — they ARE dinosaurs. They evolved from a group of two-legged theropod dinosaurs called maniraptorans during the Late Jurassic period, around 150 million years ago. Fossils like Archaeopteryx and Microraptor show clear transitional features. Today's ~10,000 bird species make dinosaurs the most species-rich group of land vertebrates on Earth.

Non-avian dinosaurs first appeared around 230–240 million years ago in the Triassic period and went extinct 66 million years ago. That means they ruled Earth for approximately 165 million years — compared to modern humans, who have existed for only about 300,000 years. To put it in perspective, T. rex and Stegosaurus are separated by more time than T. rex and us.

Epigenetics studies heritable changes in gene activity that do not involve alterations to the DNA sequence itself. Methyl groups or proteins can attach to DNA and switch genes on or off. Studies on Dutch famine survivors (1944–45) found that their children and grandchildren showed altered metabolism and increased disease risk — showing that starvation changed gene expression patterns passed down across generations. This challenges the traditional view that only DNA sequence is inherited.

Before photosynthesis evolved in cyanobacteria around 2.7 billion years ago, Earth's atmosphere contained virtually no free oxygen. The 'Great Oxidation Event' roughly 2.4 billion years ago, driven by cyanobacterial photosynthesis, transformed the atmosphere and enabled the evolution of complex aerobic life. Today, photosynthetic organisms — plants, algae, and cyanobacteria — collectively produce about 300 billion tonnes of oxygen per year, of which roughly half comes from ocean phytoplankton.

The endosymbiotic theory, confirmed by Lynn Margulis in the 1960s and now universally accepted, holds that mitochondria — the powerhouses of eukaryotic cells — were once independent alpha-proteobacteria that were engulfed by an ancestral cell roughly 1.5 billion years ago. Instead of being digested, they formed a mutually beneficial partnership. Evidence: mitochondria have their own circular DNA, divide by binary fission, and have double membranes — all hallmarks of bacterial ancestry.

A remarkable 98% of these cichlid species are endemic, meaning they are found nowhere else in the world. This extraordinary biodiversity makes the lake a critical hotspot for evolutionary biology and a unique natural aquarium.

Fossil records indicate that scorpions are among the oldest known terrestrial arthropods, having evolved from marine ancestors. Early scorpions possessed gills and adapted to land environments during the Silurian period, predating dinosaurs by hundreds of millions of years.

While seemingly disparate, this shared genetic material reflects common ancestry and fundamental biological processes essential for life. Many genes involved in basic cellular functions are highly conserved across diverse species.