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suman suhag's avatar
suman suhag
Oct 14

The biblical god does exist only in the imagination of believers. The theory of evolution has already debunked the bible and the christian god, yet many christians ignore the truth. Many of them deceive themselves.

Source: Scientific American

We wanted to examine the anatomy of such an animal in detail and thus decided to focus on one of the few modern-day animals in this group: the lamprey, an eel-like fish with a funnel-shaped mouth built for sucking rather than biting. It turns out that this fish, too, has a camera-style eye complete with a lens, an iris and eye muscles. The lamprey’s retina even has a three-layered structure like ours, and its photoreceptor cells closely resemble our cones, although it has apparently not evolved the more sensitive rods. Furthermore, the genes that govern many aspects of light detection, neural processing and eye development are the same ones that direct these processes in jawed vertebrates.

These striking similarities to the eye of jawed vertebrates are far too numerous to have arisen independently. Instead an eye essentially identical to our own must have been present in the common ancestor of the jawless and jawed vertebrates 500 million years ago. At this point, my colleagues and I could not help but wonder whether we could trace the origin of the eye and its photoreceptors back even further. Unfortunately, there are no living representatives of lineages that split off from our line in the preceding 50 million years, the next logical slice of time to study. But we found clues in the eye of an enigmatic beast called the hagfish.

Source: talk origins

In technical phylogenetic jargon, primitive characters are called plesiomorphies, and derived characters are called apomorphies. In cladistics, related species are grouped together because they share derived characters (i.e., apomorphies) that originated in a common ancestor of the group, but were not present in other, earlier ancestors of the group. These shared, derived features are called synapomorphies. Primitive and derived are therefore relative terms, depending upon the specific group being considered. For example, backbones are primitive characters of vertebrates, while hair is a derived character particular to mammalian vertebrates. However, when considering mammals only, hair is primitive, whereas an opposable thumb is derived.

In real-life phylogenetic analyses, shared derived characters may be in conflict with other derived characters. Thus, objective methods are required for resolving this character conflict (Kitching et al. 1998, Ch. 1; Maddison and Maddison 1992, p. 49). For instance, wings are a derived character of birds and of bats. Based upon this character alone, the cladistic method would group bats and birds together, which is how the author of Deuteronomy grouped them in the Biblical quote above. However, other shared derived characters indicate that bats should be grouped with wingless mammals, and that birds should be grouped with wingless dinosaurs.

In the past 40 years, several algorithmic methods have been devised to resolve such instances of character conflict and to infer correct phylogenetic trees (Felsenstein 2004, Ch. 10). The following sections outline some of the most successful of these methods. Each method attempts to infer a phylogeny from existing data, and each has its respective strengths and weaknesses. Years of empirical testing and simulation have shown that, in general, these different algorithms, each with very different underlying assumptions, converge on trees that are highly similar when judged statistically (Li 1997, Chs 5 and 6; Nei and Kumar 2000, Chs 6, 7, and 8).

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