THE EARTH

THE EARTH

The beginning of life on Earth 

The atmosphere of the early Earth was composed of gases such as sulphur dioxide, nitrous oxide, methane and ammonia. This is a similar gas mix to that produces by volcanoes. If the Earth was still surrounded by this gas mix today, it would be toxic to most organisms.

Nonetheless, even with this toxic mix of gases the first life-bacteria - evolves. These bacteria adopted to these harsh conditions and became more diverse. One type of bacterium-the Cyanobacteria-began to  produce oxygen as a metabolic by-product.

The oxygen built up in the atmosphere over time and enabled the rise of animal life. The first animals to evolve were worm-like and only their burrows are preserved in rocks. Due to increasing pressure from predators, however, animals began to secrete hard outer skeletons for protection, e.g. shelly animals such as snails.

Evolution

Oxygen eventually built up to its present levels, generating the ozone shield that screen out UV radiation and allows complex forms of life to live on land. Fish, amphibians, insects and reptiles evolved. The rocks of the Burren and Cliffs of Mother formed roughly when amphibians and insects were evolving.

The appearance of gross allowed the evolution and diversification of the grazing animals which dominate temperate and subtropical zones of the Earth today.