What causes molecular Homoplasies?

Homoplasy can arise from both similar selection pressures acting on adapting species, and the effects of genetic drift.

What is the danger of Homoplasies in constructing a phylogenetic tree?

Homoplasies often obscure the true evolutionary history of sequences by suggesting greater genetic similarity. The presence of a large number of homoplasies in a set of sequences can therefore obscure their true phylogenetic relationships [5, 6].

What is a Homoplastic trait?

Homoplastic (analogous) characters may also be similar in appearance, but have actually evolved from different ancestors. Octopus eyes and human eyes are homoplastic; they develop very differently and have evolved independently in two remotely related groups of animals.

What is the difference between Homoplasies and homologous structures?

Homology is a product of divergent evolution. This means that a single ancestor species split, or diverges, into two or more species at some time in its history. Homoplasy, on the other hand, is due to convergent evolution. Here, different species develop, rather than inherit, similar traits.

What is the molecular clock and why is it important?

The molecular clock technique is an important tool in molecular systematics, the use of molecular genetics information to determine the correct scientific classification of organisms or to study variation in selective forces.

What is a reversal trait?

Reversal – is a loss of derived trait present in ancestor and the reestablishment of a plesiomorphic trait. Convergence – independent evolution of a similar trait in two or more taxa. Apomorphy – a derived trait. Apomorphy shared by two or more taxa and inherited from a common ancestor is synapomorphy.

What is a Synapomorphic trait?

In evolution: Maximum parsimony methods. …of derived shared traits, called synapomorphic traits. A synapomorphic trait is shared by some taxa but not others because the former inherited it from a common ancestor that acquired the trait after its lineage separated from the lineages going to the other taxa.

What are the characteristics of a good molecular clock?

An ideal molecular clock has a number of features: rate constancy through time, rate homogeneity across lineages, taxonomic breadth and applicability, and accessibility of the data. Characters that have evolved at a relatively constant rate are the most suitable for molecular clocks.

What is the purpose of the molecular clock?

Evolutionary biologists can use this information to deduce how species evolve, and to fix the date when two species diverged on the evolutionary timeline. “Unlike a wristwatch, which measures time from regular changes (ticks), a molecular clock measures time from random changes (mutations) in DNA,” Hedges notes.

What is it called when a trait is lost?

In biology, an atavism is a modification of a biological structure whereby an ancestral genetic trait reappears after having been lost through evolutionary change in previous generations. A number of traits can vary as a result of shortening of the fetal development of a trait (neoteny) or by prolongation of the same.

What is a ancestral trait?

an evolutionary trait that is homologous within groups of organisms (see homology) that are all descended from a common ancestor in which the trait first evolved.