Science, Part 22

Question 1: Discuss three significant events in the history of life on Earth which paved the way for the evolution of man.

Answer 1: The origination of life is the most fundamental development in the history of life on Earth. Prokaryotic microfossils, the earliest fossils identified by paleontologists, are dated to near 3.5 billion years ago. However, the presence of large amounts of certain carbon and oxygen isotopes in sedimentary rocks dated at about 3.8 billion years ago may indicate the presence of organic material. The next significant event suggested by a drastic change in the fossil record is the huge diversification of species which occurred approximately 543 million years ago, near the end of the Precambrian eon and the beginning of the Phanerozoic. This evolutionary stage included higher-level tissue organization in multicellular organisms, the development of predator-prey relationships, and, most importantly, the development of skeletons. The final critical step toward the evolution of man is the emergence of life on land about 418 million years ago. This necessitated the evolution of structures which could breathe air, obtain and retain water on land, and support its own weight out of water.

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Question 2: Explain how organism species are classified.

Answer 2: The study of the evolutionary relationships between organism species is called phylogenetics. In this field of study, scientists make use of cladistic taxonomy to classify species. Cladistic taxonomy places species in groups based on “shared derived properties” called synamorphies, which are physical similarities assumed to be shared by different species because they evolved from a common ancestor. In this method, organism species are placed in successively smaller cladistic groups, originally delineated by Carolus Linnaeus. The divisions of this five-kingdom system are, from broadest to narrowest: Kingdom, Phylum, Class, Order, Family, Genus, and Species. Phylogenetic classification can be expressed graphically through a phylogenetic, or evolutionary, tree. Some modern scientists adhere to the recently developed three-domain system, which features a top-level grouping of domain consisting of Archaea, Eukaryota, and Eubacteria.

Question 3: Explain biochemical record and imperfect design.

Answer 3: Biochemical record refers to the genetic coding of organisms. This information may be examined in one organism and compared to that of another. The theory of evolution suggests that modern-day organisms should share certain aspects of their genetic codes due to the fact that certain organisms, like humans and apes, share common ancestors. Therefore, investigation of this biochemical record reveals that the closer organisms are on the evolutionary tree, the more similar their DNA will be. Organisms do not need to be perfect to survive, only better than their competitors. Thus, the attributes of each member of an evolved species builds on those of the organisms before it. This means that certain traits which may have been optimal in the past get cemented into the genetic make-up of a species, even if “better” ones are currently available. This is called imperfect design, a phenomenon that lends support to the theory of evolution while contradicting the deterministic the belief that each organism exists for a specific purpose.

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