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Proterozoic Eon – eukaryotes to worms

By |2018-04-21T11:56:39-07:00June 24th, 2017|Biology, Geology|

Two and a half billion years ago, the Archaean Eon ended and the Proterozoic Eon began. Trillions of prokaryote cells lived in Earth's oceans. Some of these cells could photosynthesize their energy from sunlight, water, and carbon dioxide. These photosynthesizing cells pooped out a lot of oxygen. By about 2.3 billion years ago, the iron [...]

Why do eyes have pupils? Evolution and Biology

By |2017-05-27T15:32:08-07:00May 27th, 2017|Biology|

By around 550 million years ago, some kinds of worms evolved eyespots sunk into their heads to protect them from being damaged. As a side effect, it turned out that being sunk into the head also helped to focus the light on just one spot, so that more light reached that spot and the worm could see [...]

Spiders and their Webs – Biology

By |2017-09-16T18:40:57-07:00May 25th, 2017|Biology|

Fossil spider from the Cretaceous era Spiders evolved from annelid worms beginning about 540 million years ago. They were among the first land creatures with more than one cell. At about the same time, the first bigger land animals began to come out of the water: frogs and salamanders. These ate spiders. The earliest evidence of an orb [...]

Why do mosquitoes bite? Biology

By |2018-04-15T17:18:17-07:00May 25th, 2017|Biology|

Mosquitoes bite people: A mosquito on human skin Like bees, mosquitoes evolved from earlier flies and dragonflies about 200 million years ago, during the Jurassic period. Mosquitoes have six legs like other insects. Also like bees, mosquitoes evolved to eat pollen from the new flowers that appeared about this time. And like bees, mosquitoes [...]

What are arthropods? Biology

By |2019-02-03T21:35:07-07:00May 25th, 2017|Biology|

Bee on a flower What are arthropods? Insects, spiders, crabs, and lobsters are all arthropods, so there are a lot of arthropods on Earth. Annelid worms All our biology articles When were the first arthropods? The earliest arthropods on Earth developed about 550 million years ago. That was during the Proterozoic period. Proterozoic [...]