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. Read the rest of the story here | See the Evo in the News archive. 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. Should they be considered the same species or separate species? If two lineages of oak look quite different, but occasionally form hybrids with each other, should we count them as different species?
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. Make copies of Grid Map of California. Enlarged copies would work best (one per team). 3. 4. 5. 6. 7.
COMMENT: This lesson demonstrates how speciation occurs and should emphasize for students that a scientist's real work begins when she/he starts to organize and analyze data. PRESENTATION: 1. 2. 3. 4. 5. 6. RECENT DEVLOPMENTS AND CURRENT STUDIES OF ENSATINA at ENSATINA UPDATE: Confirmation of hypothesized relationship from DNA analyses and other studies (added February, 2010).