This lesson introduces molecular evidence for common descent, including shared biochemical systems and comparisons of DNA and proteins. Molecular evidence matters because it can reveal relationships that are difficult to see from an organism’s outward appearance.
All known organisms use closely related biochemical systems. Their genetic information is encoded in nucleic acids, and cells use RNA and ribosomes to produce proteins from amino acids. ATP serves as an energy currency throughout cellular life, and the genetic code is nearly universal.
All flashcards
What is common descent?
The idea that organisms are related through shared ancestors, extending ultimately to ancient ancestral life.
What is a phylogenetic tree?
A representation of a hypothesis about the evolutionary relationships and branching history of organisms.
What is a molecular clock?
A method that uses the accumulation of genetic changes to estimate when lineages diverged.
What is a pseudogene?
A gene-like DNA sequence that has lost its original function, often retaining evidence of its history in a genome.
Why is the near-universal genetic code significant?
It is a shared feature of life consistent with organisms inheriting fundamental biochemical systems from common ancestors.
Quiz questions
What does greater DNA sequence similarity generally suggest about two species?Answer: They usually share a more recent common ancestor.
What does a phylogenetic tree represent?Answer: A hypothesis about evolutionary relationships and branching among organisms.
Why can the same pseudogene in related species support common descent?Answer: The species may have inherited the inactive sequence from a shared ancestor.
Why do some DNA regions evolve more slowly than others?Answer: Important functions can constrain changes in some regions.
How do scientists use a molecular clock to estimate lineage divergence?Answer: They use accumulated genetic changes and may calibrate estimates with fossils.