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Evolution. Understanding Evolution. The bacteria that changed the world - May, 2017 The make-up of Earth's atmosphere, once the domain of Earth science textbooks, has become an increasingly "hot" news topic in recent decades, as we struggle to curb global warming by limiting the carbon dioxide that human activity produces.
While the changes that humanity has wrought on the planet are dramatic, this isn’t the first time that one species has changed Earth’s atmosphere. Three billion years ago, there was no free oxygen in the atmosphere at all. Life was anaerobic, meaning that it did not need oxygen to live and grow. That all changed due to the evolution of Cyanobacteria, a group of single-celled, blue-green bacteria.
Speciation. For example, these happy face spiders look different, but since they can interbreed, they are considered the same species: Theridion grallator.
Also, many plants, and some animals, form hybrids in nature. Hooded crows and carrion crows look different, and largely mate within their own groups—but in some areas, they hybridize. 18_Pangaea.swf. Speciation Activity. Lesson: evolution mini-lesson: A Step in Speciation. Time: Two 50-minute periods Preparation: 1.
Make color copies of the salamander sheets (one per team of 2-4); place these in non-glare transparent plastic notebook sleeves to protect from wear and tear as they are re-used every period and year. 2.