Answer:
(B) resemble structures formed by bacterial communities that are found today in some shallow marine bays.
Explanation:
Extant stromatolites represent real "living fossils" for they are decendents of ancient forms that are associated with one of the first living forms on earth. Particularly, stromatolites are real bacteria communities where the autotrophic organism of the community are represented by cyanobacteria, which live along with heterotrophic bacteria. This clearly indicates that fossilized stromatolites points to bacteria (prokaryotes) as the first living things on earth (dated with not less than 3.5 billion year old)
Nowadays, stromatolites with cyanobacteria allows to reconstruct and understand fossilized forms. These current structures live in shallow marines ambients (e.g. Australia) but also in continental salt flats (e.g. Argentina) where few others bacteria can survive to these extreme conditions (high light exposure and salt concentration).
Answer: D. all of the above
Explanation:
Proteins have up to four levels of organic structure.
1.Primary structure - the linear arrangement of amino acids.
2. Secondary structure - areas of folding or coiling within a protein.
3. Tertiary structure - the final three dimensional structure of a protein.
4. Quaternary structure - non covalent associations that bind multiple polypeptides into a single larger protein. E.g. hemoglobin has four polymers, two alpha and two beta chains. They are non covalently bound to each other to form a single large protein - hemoglobin.
For the first 12 hours after conception, the fertilized egg remains a single cell. ... During the first 8 or 9 days after conception, the cells that will eventually form the embryo continue to divide
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