Question

Suppose we found an organism on Earth with the characteristics described. In light of our current understanding of life on Earth, should we be surprised to find such an organism existing? Why or why not? Explain clearly; because not all of these have definitive answers. your explanation is more important than your chosen answer. A species of bacteria that has a genome \(99 \%\) identical to that of humans.

Short answer

Yes, it is highly surprising due to the vast genome difference typically observed between humans and bacteria.

Step-by-step solution

Understand Genome Similarity

The genome refers to the complete set of DNA, including all of its genes, in an organism. In humans, there are approximately 3 billion base pairs. Genome similarity between different species refers to how much of the DNA sequence is the same between them.

Analyze Human-Bacteria Comparison

Humans and bacteria are vastly different organisms. Humans are eukaryotic organisms with complex cellular structures, while bacteria are prokaryotic, simpler organisms. Typically, genome similarity between humans and bacteria is quite low, often around 7-10%.

Addressing the 99% Similarity

If a bacterial species is 99% genetically similar to humans, this would be extremely surprising. Such high similarity is not observed in any known bacteria and far exceeds typical genome overlaps, even between humans and other mammals.

Consider Implications and Conclusion

Given our current scientific understanding, finding a bacterium with 99% genetic similarity to humans would challenge existing knowledge of evolution and genetic diversity. This could suggest new principles of genome organization or a very unusual evolutionary event.

Key concepts

Understanding Genome Similarity

The term 'genome' refers to the complete set of DNA that carries an organism's genetic blueprint. DNA is made up of sequences of base pairs, and the human genome, for example, consists of about 3 billion of these base pairs. When discussing genome similarity, we refer to the extent to which the DNA sequences of two different species or organisms match. The greater the similarity in DNA sequences, the more closely related the organisms are thought to be.
For instance, humans share approximately 96% of their genome with chimpanzees, which signifies a close evolutionary relationship. In contrast, species that are vastly different, such as humans and bacteria, usually exhibit low genomic similarity, often between 7% and 10%. This low similarity reflects their distant evolutionary paths and differing life forms.
Understanding genome similarity is crucial in evolutionary biology, as it helps trace the lineage and evolutionary history of various species. It's a tool used extensively in genomics to explore relationships among species and to understand how new species have evolved.

Analyzing Human-Bacteria Genomic Comparison

Humans and bacteria belong to two entirely different domains of life. Humans are complex multicellular organisms categorized as eukaryotes. They have cells with distinct nuclei and various organelles, which perform specialized functions. Bacteria, on the other hand, are simpler, unicellular organisms classified as prokaryotes. Their cells lack a nucleus and other membrane-bound organelles.
Despite their differences, the genome of every organism, regardless of complexity, carries the necessary instructions for growth, development, and reproduction. Traditionally, the genetic similarity between humans and bacteria is considered to be very low, ranging around 7-10%. This low similarity is expected, considering the vast differences in their structural and functional complexity.
When comparing humans to bacteria genetically, the few similarities that do exist are attributed to the basic functions required for cellular life, such as DNA replication, transcription, and translation processes. These processes are essential for survival and are thus conserved across different life forms, explaining the small percentage of shared genome content.

Insights from Evolutionary Biology

Evolutionary biology is the branch of science focused on understanding the origins and changes in the diversity of life on Earth over time. It offers insights into how complex life forms, like humans, evolved from simpler ones, including bacteria.
DNA mutations and genetic variation are fundamental to evolution. They serve as raw materials for natural selection, leading to the evolution of new species with unique characteristics. Through the study of genomes and their similarities, evolutionary biologists can decipher the ancestral relationships among species.
In the hypothetical scenario of a bacterial species sharing 99% of its genome with humans, such a discovery would pose significant challenges to current evolutionary theory, as this level of similarity is unobserved and would require reevaluation of our understanding of genetic and evolutionary mechanisms. It might suggest either convergent evolution, where similar traits evolve independently in unrelated lineages, or an unprecedented evolutionary event, potentially altering the perceived boundaries between species in the evolutionary tree.