When you look at humans and animals that reproduce on the order of decades, other factors besides genome efficiency determine survival, and that is why over half of the human genome is actually junk of non-coding sequences, transposons, and genetic viruses that do absolutely nothing to help run the organism and create all kinds of useless enzyme-like peptide chains. This is exactly why the bacteria genome is so small compared to a humans and contains almost only gene sequences, because even waste in the genome will confer a disadvantage. As a result any inefficiency will be immediately met by being outcompeted and a more efficient bacteria out multiplying it. Bacteria must be extremely efficient organisms because they reproduce on a time scale of minutes as compared to years or decades. Your point is only relevant to rapidly dividing single cell organisms like bacteria, not humans or dogs. At the cellular level, a seemingly-insignificant change can have an incredible different when it comes to energy consumption and conservation. So, in short, those bacteria were more evolutionary fit and were able to pass on more of their genes to the next generation. The ones that had a lac operon similar to the one they have today reproduced more because they 1.) Had the ability to use multiple food sources (lactose and glucose) and 2.) Had the ability to not waste energy while being able to do number 1. The change to the operon and the bacterial cells happened over many millions of years. Now, take a step back and realize that none of this magically appeared this way. If there is an abundance of both glucose and lactose in the environment around a bacteria cell with a standard lac operon, a signal will be sent to not make lactase because it already has a food source that doesn't need to be broken down to be used (glucose) and making the extra enzymes would require too much extra energy. ![]() If there is no lactose around, the operon is signalled to stop making lactase. If there is lactose around, but not glucose, the operon is signaled to make the enzyme lactase (among a few other things for bringing in lactose) so that the lactose can be separated into galactose and glucose and then used as fuel. To give you an example of how much more beneficial it is to not make unnecessary enzymes, we can look at the lac operon in many bacteria. Telomerase is an enzyme, and enzymes are costly to make. Humans have telomerase that helps maintain telomere length (and stop "aging"). We make our world significant by the courage of our questions and by the depth of our answers. For more open-ended questions, try /r/AskScienceDiscussion | Sign up to be a panelist!.Looking for flair? Sign up to be a panelist!.Neuroscience, Neurology, Neurochemistry, Cognitive NeuroscienceĪskScience AMA Series: Extreme Weather, PNNLĪsk Anything Wednesday - Biology, Chemistry, Neuroscience, Medicine, PsychologyĪskScience AMA Series: Environmental Psychology GroningenĪsk Anything Wednesday - Economics, Political Science, Linguistics, AnthropologyĪsk Anything Wednesday - Physics, Astronomy, Earth and Planetary ScienceĪsk Anything Wednesday - Engineering, Mathematics, Computer science Medicine, Oncology, Dentistry, Physiology, Epidemiology, Infectious Disease, Pharmacy, Human Body Psychology, Cognitive Psychology, Developmental Psychology, Abnormal, Social Psychology Social Science, Political Science, Economics, Archaeology, Anthropology, Linguisticsīiology, Evolution, Morphology, Ecology, Synthetic Biology, Microbiology, Cellular Biology, Molecular Biology, Paleontology Mechanical Engineering, Electrical Engineering, Structural Engineering, Computer Engineering, Aerospace EngineeringĬhemistry, Organic Chemistry, Polymers, Biochemistry Mathematics, Statistics, Number Theory, Calculus, AlgebraĪstronomy, Astrophysics, Cosmology, Planetary FormationĬomputing, Artificial Intelligence, Machine Learning, ComputabilityĮarth Science, Atmospheric Science, Oceanography, Geology Theoretical Physics, Experimental Physics, High-energy Physics, Solid-State Physics, Fluid Dynamics, Relativity, Quantum Physics, Plasma Physics /r/AskScienceDiscussion: For open-ended and hypothetical questions.FAQ: In-depth answers to many popular questions.Weekly Features: Archives of AskAnything Wednesday, FAQ Fridays, and more!.Be civil: Remember the human and follow Reddiquette.Report comments that do not meet our guidelines, including medical advice.Downvote anecdotes, speculation, and jokes.Upvote on-topic answers supported by reputable sources and scientific research.Answer questions with accurate, in-depth explanations, including peer-reviewed sources where possible.Please read our guidelines and FAQ before posting
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