History. The rainforest was likely formed during the Eocene era, following the evolutionary appearance of angiosperm plants. It appeared following a global reduction of tropical temperatures when the Atlantic Ocean had widened sufficiently to provide a warm, moist climate to the Amazon basin. The rainforest has been in existence for at least 55 million years, and most of the region free of savannah-type biomes during that time period.
Following the Cretaceous-Tertiary extinction event, the extinction of the dinosaurs and the wetter climate may have allowed the tropical rainforest to spread out across the continent. There is evidence that there have been significant changes in Amazon rainforest vegetation over the last 21,000 years through the Last Glacial Maximum (LGM) and subsequent deglaciation. Analyses of sediment deposits from Amazon basin paleolakes and from the Amazon Fan indicate that rainfall in the basin during the LGM was lower than for the present, and this was almost certainly associated with reduced moist tropical vegetation cover the basin.
Based on archaeological evidence from an excavation at Caverna da Pedra Pintada, human inhabitants first settled in the Amazon region at least 11,200 years ago. The first European to travel the length of the Amazon River was Francisco de Orellana in 1542. The rainforest has been predicted to destroy itself and become a savannah sometime before 5,000,000 CE. While all the current animals (including present-day birds, insects, mammals, and reptiles) that inhabit the Amazon rainforest will be extinct by this date, new animals will evolve to take over the new savannah.
Biodiversity. Wet tropical forests are the most species-rich biome, and tropical forests in the Americas are consistently more species rich than the wet forests in Africa and Asia. As the largest tract of tropical rainforest in the Americas, the Amazonian rainforests have unparalleled biodiversity. One in ten known species in the world live in the Amazon Rainforest. This constitutes the largest collection of living plants and animal species in the world.
The diversity of plant species is the highest on Earth with some experts estimating that one square kilometer may contain over 75,000 types of trees and 150,000 species of higher plants. One square kilometer of Amazon rainforest can contain about 90,790 tonnes of living plants. The green leaf area of plants and trees in the rainforest varies by about 25% as a result of seasonal changes. Leaves expand during the dry season when sunlight is at a maximum, then undergo abscission in the cloudy wet season. These changes provide a balance of carbon between photosynthesis and respiration.
The rainforest contains several species that can pose a hazard. Among the largest predatory creatures are the Black Caiman, Jaguar and Anaconda. In the river, electric eels can produce an electric shock that can stun or kill, while Piranha are known to bite and injure humans. Various species of poison dart frogs secrete lipophilic alkaloid toxins through their flesh. There are also numerous parasites and disease vectors. Vampire bats dwell in the rainforest and can spread the rabies virus. Malaria, yellow fever and Dengue fever can also be contracted in the Amazon region. They could be deadly...Be careful!! Thank you for reading!! STARRY.