2 How has biodiversity changed through time?
Learning Objectives
In this chapter student will be able to:
- List five mass extinction event
- Explain the impacts of extinction
In the middle of the Cambrian Period, about 500 million years ago, our planet looked completely different. There was land, but there were not any plants or animals living on it. Instead, the dry land was rocky and barren, with no shrubs, trees or grasses except a paper-thin film of microbes clinging to the rocks and thin ancient soils. These microbes were most likely the only terrestrial life around, and had been for several billion years. Scientists believed these ancient microbial films were probably made up of cyanobacteria and maybe some of the first fungi. And each bacterium was likely doing what cyanobacteria do today – sending out tiny filaments of cells from the main bacterial mat to start new colonies. So, the fact is, for a good billion years ago of Earth’s history, cyanobacteria had a monopoly on the terrestrial environment.
Life on earth was getting a little more crowded with arriving of new organisms where those newcomers would end up changing the world biodiversity. Their arrival would make the world colder, and fast, and it would drain much of the oxygen out of the world’s oceans. Eventually, it cause a massive extinction event, in which around 85% animal species, including a quarter of marine animal families, disappeared from the planet forever. This environmental catastrophe is known today as the End-Ordovician Extinction Event, and it was the first of what we often call the Big Five mass extinctions in the history of our planet.
View the following video to learn more.
Adopted from: "5 Mass Extinctions, and We're Looking at the Sixth" by BRIGHT SIDE is licensed under CC BY 4.0
At the most basic level, mass extinctions reduce diversity by killing off specific lineages, and with them, any descendent species they might have given rise to. In this way, mass extinction prunes whole branches off the tree of life. As we lose animals and plants, we lose the natural caretakers of the earth. As animal extinction begins to worsen, it also begins to drastically affect our ecology. Alongside systems like the food chain breaking down, processes like biotic pollination (pollination carried out by animals such as bees) cease to carry on.
Lets learn more from this interactive book:
Self-Assessment
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