TAILIEUCHUNG - Radiations & Extinctions: Biodiversity Through the Ages

The new body plans allowed animals to organize themselves into new ecosys- tems the Earth had never seen before. The earliest animals appear to have lived like sponges do today—trapping microbes or organic matter from the water as they remained anchored to the seafloor. But then animals evolved with guts and nervous systems, able to swim through the water or burrow into the muck. With their guts, they could swallow larger microbes, and, eventually, could even start to attack other animals. shows a 550-million-year-old fossil Cloud- ina bearing the oldest known wounds from the attack of a predator. Charles Marshall, a biologist at Harvard University, has proposed. | Reprinted from The Tangled Bank An Introduction to Evolution by Carl Zimmer. Permission granted by Roberts and Company Publishers. f Radiations 10 I Extinctions Biodiversity Through the Ages There s a story that scientists like to tell about the great evolutionary biologist J. B. S. Haldane. Supposedly Haldane once found himself in the company of a group of theologians. They asked him what one could conclude about the nature of the Creator from a study of his creation. An inordinate fondness for beetles Haldane replied. There are some 350 000 named species of beetles 70 times more species than all the mammal species on Earth. Insects the lineage to which beetles belong include a million named species the majority of all million species scientists have ever described. 211 B Illi 100 100-200 200-500 500-1000 1000-1500 1500-2000 2000-3000 3000-4000 4000-5000 5000 Number of vascular plant species per 10 000 square kilometers Figure The diversity of plants is much higher in the tropics than in the regions near the poles. Animals and other groups of species show a similar pattern of diversity. Adapted from Benton 2008 Biological diversity or biodiversity for short is one of the most intriguing features of life. Why are there so many insects on Earth and so few mammals Why is biodiversity richest in the tropics rather than being spread smoothly across the planet Figure Why do different continents have different patterns of diversity Almost everywhere on Earth for example placental mammals make up the vast diversity of mammal diversity. On Australia however there is a huge diversity of marsupial mammals. Biodiversity has also formed striking patterns through the history of life as illustrated in Figure . A large team of scientists produced this graph by analyzing records for million fossils of marine invertebrates that lived during the past 540 million years. They divided up that time into 48 intervals and calculated how many genera were alive in each

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