ancestral

Examples of ancestral in the following topics:

• Sympatric Speciation

  • Sympatric speciation occurs when two individual populations diverge from an ancestral species without being separated geographically.
  • These individuals would immediately be able to reproduce only with those of this new kind and not those of the ancestral species.

• Early Human Evolution

  • Hominins, who were bipedal in comparison to the other hominoids who were primarily quadrupedal, includes those groups that probably gave rise to our species: Australopithecus africanus, Homo habilis, and Homo erectus, along with non-ancestral groups such as Australopithecus boisei.
  • It is possible that there were often more than one species alive at any one time and that many of the fossils found (and species named) represent hominin species that died out and are not ancestral to modern humans.

• Early Hominins

  • The hominin Australopithecus evolved 4 million years ago and is believed to be in the ancestral line of the genus Homo.
  • These hominids became extinct more than 1 million years ago and are not thought to be ancestral to modern humans, but rather members of an evolutionary branch on the hominin tree that left no descendants.

• Gene Duplications and Divergence

  • If an ancestral gene is pleiotropic and performs two functions, often times neither one of these two functions can be changed without affecting the other function.
  • In this way, partitioning the ancestral functions into two separate genes can allow for adaptive specialization of subfunctions, thereby providing an adaptive benefit.
  • Genetic divergence is the process in which two or more populations of an ancestral species accumulate independent genetic changes through time, often after the populations have become reproductively isolated for some period of time.

• Speciation

  • Biologists think of speciation events as the splitting of one ancestral species into two descendant species.

• Chromosomal Structural Rearrangements

  • Researchers characterizing this inversion have suggested that approximately 19,000 nucleotide bases were duplicated on 18p, and the duplicated region inverted and reinserted on chromosome 18 of an ancestral human.
  • Perhaps the chromosome 18 inversion in an ancestral human repositioned specific genes and reset their expression levels in a useful way.

• Phylogenetic Trees

  • Scientists call such trees 'rooted,' which means there is a single ancestral lineage (typically drawn from the bottom or left) to which all organisms represented in the diagram relate.
  • The root of a phylogenetic tree indicates that an ancestral lineage gave rise to all organisms on the tree.

• Building Phylogenetic Trees

  • If a characteristic is found in the ancestor of a group, it is considered a shared-ancestral character because all of the organisms in the taxon or clade have that trait .
  • The tricky aspect to shared-ancestral and shared-derived characters is the fact that these terms are relative.

• Phylum Mollusca

  • An anatomical diagram of a hypothetical ancestral mollusk, showing features common to many mollusk types.

• Convergent Evolution

  • Bat and pterosaur wings are an example of analogous structures, while the bat wing is homologous to human and other mammal forearms, sharing an ancestral state despite serving different functions.