Páginas: 3 (556 palabras) Publicado: 15 de septiembre de 2010
Early Single-Celled Organisms

Reviewing – Main Ideas

1. How did early cyanobacteria affect the physical and chemical conditions on Earth?

Cyanobacteria formed when variousprokaryotic cells got together, these were the first organisms to make the process of photosynthesis. Conditions on earth both physical and chemical, were affected by cyanobacteria because of the production ofoxygen, which provided a proper environment for the formation and evolution of organisms.

2. How does the theory of endosymbiosis account for the evolution of eukaryotes?

Endosymbiosisis an ecological relationship in which an organism lives inside another. This is one of the most important factors through the development of organisms, it began to occur when a large prokaryote“took in” a small prokaryote, and this small prokaryote started to make the function of a mitochondria or a chloroplast. This process is very similar to that of fagocitosis. This was a key process becauseit was the first step into the evolution of eukaryotes that are double organelle cells.

3. How does sexual reproduction increase diversity among living things?

During sexualreproduction, gametes undergo meiosis. During the process of meiosis each parent can give a different characteristic to the “baby” and by this process the embryo can have both characteristics from the mother andfrom the father, and this will provide more possibilities for the outcome of the organisms. So even if the embryo shows a variety of similarities with one of the parents it will never be exactly likeit. This is the key factor for biodiversity. Meanwhile, what happens in asexual reproduction is mitosis, in which the outcome will be exactly identical to its parent.

Critical Thinking

4.How does sexual reproduction increase the chances that some individuals will survive changed environmental conditions?

Sexual reproduction increases the chances that some individuals will...
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