Continuing Evolution

Unit : Natural Selection

Chapter: Continuing Evolution

Reference: Continuing evolution, Contributions to genomic evolution, Continuous change in fossil record, Evolution in antibiotic resistance

Learning objectives

  •  To explain how evolution is an ongoing process in all living organisms.

Continuing evolution

Genomic changes over time indicate humans and other organisms are still evolving. Fossil records, evolution of resistance to antibiotics, and emerging new diseases are all examples of continuing evolution.

Genomic evolution

  • Genome evolution involves rearrangement of existing genes as well as the generation of new genes by duplication followed by mutation, novel protein functions can also be produced by rearranging existing genes.
  • This is possible because most proteins are made up of structural domains
  • The examples are the genomes of Mycobacterium tuberculosis and Mycobacterium leprae, the latter of which has a dramatically reduced genome. Another example are endosymbiont species

Contributions to genomic evolution

  • Processes such as mutations, duplications, exon shuffling, transposable elements and pseudogenes have contributed to genomic evolution.
  • A pseudogene is a segment of DNA that structurally resembles a gene but is not capable of coding for a protein. Pseudogenes are most often derived from genes that have lost their protein-coding ability due to accumulated mutations that have occurred over the course of evolution
  • Transposons can serve as genetic tools to introduce foreign DNA into the genome of another organism.
  • Exon shuffling is an essential molecular mechanism for the formation of new genes. Many cases of exon shuffling have been reported in vertebrate genes.

Continuous change in fossil record

  • The fossil record shows us when specific types of organisms appeared, went extinct, or changed. And, the fossil record shows us that there have been mass extinctions in Earth's past. A mass extinction is when many species die off around the same time.
  • Major extinction events and natural disasters such as drought or volcanic eruptions can also be seen in the fossil record.
  • According to Darwin, this change or evolution is caused by four processes: variation, over-reproduction, competition, and survival of those best adapted to the environment in which they live. Darwin's theory accounts for all the diversity of life, both living and fossil.
  • Fossils show change because they allow palaeontologists to see how evolution influences the course of development in particular types of life.

Evolution in antibiotic resistance

  • Antibiotics are medicines that fight bacterial infections. Used properly, they can save lives. But there is a growing problem of antibiotic resistance.
  • It happens when bacteria change and resist the effects of an antibiotic. Resistant bacteria may continue to grow and multiply.
  • Through mutation and selection, bacteria can develop defence mechanisms against antibiotics.
  • For example, some bacteria have developed biochemical “pumps” that can remove an antibiotic before it reaches its target, while others have evolved to produce enzymes to inactivate the antibiotic.

Solved examples

  Example 1.A change in a gene, group of genes or chromosome that results in a change in the proteins

  1. Replication b) Mutations c) Translation d) Transcription

Solution 1: b. 1.     A change in a gene, group of genes or chromosome that results in a change in the proteins is called mutation

Example 2. Yellow toucan birds seek out one another to make babies together and tend to avoid the green toucan birds.

  1. Non-random mating b) gene flow
  2. mutation d) natural selection

    Solution 2: a. The example above is explained about non-random mating.

    Summary

  • Genomic changes over time indicate humans and other organisms are still evolving.
  • Processes such as mutations, duplications, exon shuffling, transposable elements and pseudogenes have contributed to genomic evolution.
  • Fossil records, evolution of resistance to antibiotics, and emerging new diseases are all examples of continuing evolution.

 

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