vestigial structure

Examples of vestigial structure in the following topics:

• Vestigial Structures

  • Vestigial structures have no function but may still be inherited to maintain fitness.
  • These unused structures without function are called vestigial structures.
  • Vestigial structures are often homologous to structures that function normally in other species.
  • The vestigial versions of a structure can be compared to the original version of the structure in other species in order to determine the homology of the structure.
  • Discuss the connection between evolution and the existence of vestigial structures

• Evidence of Evolution

  • Scientists call these synonymous parts homologous structures.
  • Some structures exist in organisms that have no apparent function at all, appearing to be residual parts from a common ancestor.
  • These unused structures (such as wings on flightless birds, leaves on some cacti, and hind leg bones in whales) are vestigial.
  • Great ape embryos, including humans, have a tail structure during their development that is lost by birth.
  • Like anatomical structures, the structures of the molecules of life reflect descent with modification.

• Characteristics and Evolution of Amphibians

  • Amphibians evolved from fish 400 million years ago and are characterized by four limbs, moist skin, and sensitive inner ear structures.
  • Some species of salamanders and all caecilians are functionally limbless; their limbs are vestigial.
  • Additional characteristics of amphibians include pedicellate teeth (teeth in which the root and crown are calcified, separated by a zone of noncalcified tissue) and a papilla amphibiorum and papilla basilaris (structures of the inner ear that are sensitive to frequencies below and above 10,00 hertz, respectively).
  • However, it also had four limbs, with the skeletal structure of limbs found in present-day tetrapods, including amphibians.

• Characteristics of Chordata

  • The chordates are named for the notochord: a flexible, rod-shaped structure that is found in the embryonic stage of all chordates and also in the adult stage of some chordate species.
  • In humans and other apes, the post-anal tail is present during embryonic development, but is vestigial as an adult.

• Modern Amphibians

  • The only male amphibians that possess copulatory structures are the caecilians, so fertilization among salamanders typically involves an elaborate and often prolonged courtship.
  • They have vestigial limbs which is evidence that they evolved from a legged ancestor.

• The Evolution of Plastids

  • Cyanobacteria are a group of photosynthetic bacteria with all the conventional structures of prokaryotes.
  • The green algal endosymbiont also exhibits a stunted vestigial nucleus.

• Characteristics of Reptiles

  • Limbless reptiles (snakes and other squamates) have vestigial limbs and, as with caecilians, are classified as tetrapods because they are descended from four-limbed ancestors.

• Protein Structure

  • Protein structures are very complex, and researchers have only very recently been able to easily and quickly determine the structure of complete proteins down to the atomic level.
  • Early structural biochemists conceptually divided protein structures into four "levels" to make it easier to get a handle on the complexity of the overall structures.
  • But, because the final protein structure ultimately depends on this sequence, this was called the primary structure of the polypeptide chain.
  • The most common forms of secondary structure are the α-helix and β-pleated sheet structures and they play an important structural role in most globular and fibrous proteins.
  • The tertiary structure of a polypeptide chain is its overall three-dimensional shape, once all the secondary structure elements have folded together among each other.

• Homologous Structures

  • Homology is the relationship between structures or DNA derived from the most recent common ancestor.
  • Although these two structures do not look similar or have the same function, genetically, they come from the same structure of the last common ancestor.
  • If we go all the way back to the beginning of life, all structures are homologous!
  • As a result, hybrid or mosaic structures can evolve that exhibit partial homologies.
  • The opposite of homologous structures are analogous structures, which are physically similar structures between two taxa that evolved separately (rather than being present in the last common ancestor).

• Leaf Structure and Arrangment

  • Most leaves have similar essential structures, but differ in venation patterns and leaf arrangement (or phyllotaxy).
  • A leaf may seem simple in appearance, but it is a highly-efficient structure.
  • Petioles, stipules, veins, and a midrib are all essential structures of a leaf.