Molecular Biology: Drowning In A Sea Of Data And Starving For Knowledge
One of the problems with accepting that the human genome consists mostly of junk DNA, is that additional functional DNA elements, beyond protein-coding genes, were widely known since the 1960s . Leaving aside the fact that nearly a quarter of the genome consists of intronic sequence, it has been long known that genomes contain promoters , enhancers , silencers , origins of replication , telomeres , centromeres , and a wide array of genes transcribed into various non-coding RNAs, including rRNA , tRNAs , snRNAs , and other non-coding RNAs . Although many of the founders of molecular biology were quite open to the idea of junk DNA, many of the molecular biologists that came afterwards had hyper-adaptationist tendencies. With the discovery of every new functional non-coding RNA, these researchers would extrapolate, erroneously, this finding to all cryptic transcription and conclude that it is all functional. With the discovery that a given transposable element was co-opted for a functional purpose, these molecular biologists would conclude that all transposable elements have some hidden function. The rejection of junk DNA, in the mind of these researchers, led to the idea that the genome consisted of mostly dark matter.
FIGURE 1. The mechanisms that shape traits in a weak selection regime.
The Molecular Evolution Revolution
The molecular basis of heredity not only changed our view of cellular and organismal activity, but also altered our understanding of evolution. In the first half of the 20th century, the theoretical basis of how mutations spread within a population were developed by population geneticists such as J.B.S Haldane, Sewall Wright and Ronald Fisher. By the 1950s, it was widely accepted that evolution occurred through natural selection at the genetic level. Given that the molecular basis for inheritance could now be linked to the sequence of bases in DNA, and this could be further extrapolated to the sequence of amino acids in proteins, it was unsurprising that some molecular biologists started to tackle evolutionary questions in the mid-1960s.
This crisis was further deepened by Motoo Kimuras 1968 publication Evolutionary Rate at the Molecular Level . The amount of protein variation between and within species, estimated by the new molecular biology techniques, inferred such a high substitution rate that if they all consisted of alleles that were under selection, the cost of replacing these alleles would be intolerable. Instead, Kimura proposed that the majority of these mutations must be neutral. Furthermore, Kimura demonstrated that slightly deleterious or beneficial mutations behave like neutral mutations, provided that the absolute value of their selection coefficient was smaller than the inverse of the effective population size.
How Does The Study Of Genetics And Molecular Biology Support Darwins Theory Of Natural Selection
Studies in genetics and molecular biologyfields unknown in Darwins timehave explained the occurrence of the hereditary variations that are essential to natural selection. Genetic variations result from changes, or mutations, in the nucleotide sequence of DNA, the molecule that genes are made from.
Recommended Reading: Why Do People Copy Others Psychology
Fossils As Evidence Of Evolution
Fossils are preserved remnants or traces of organisms from a past geologic age. Fossilsprovide evidence that life forms have changed over time and resulted in the diversity in life forms that we see today. Fossils show how organisms evolved, how new groups of organisms emerged, and how some species became extinct .
Fossils show patterns in the changes caused by evolution in different groups of organisms. For example, the pelvic bone in fossil stickleback fish consistently became smaller over time. The consistent shrinking of the pelvic bone is a pattern that suggests natural selection was the driving force behind the change.
Fossils also show how new groups of organisms emerge. For example, fossils provide evidence that cetaceans evolved from terrestrial mammals like hippopotamuses, pigs, and cows . This is because fossils show that the pelvis and hind limb bones of extinct cetacean ancestors became smaller over time, eventually disappearing completely and developing into flukes and flippers.
Figures 2-3. Fossils show that the hippopotamus is the closest living relative of the whale . Source : Diego Delso, CC BY-SA 4.0, via Wikimedia Commons. Source : Gabriel Barathieu, CC BY-SA 2.0, via Wikimedia Commons.
How Is Amino Acid Sequence Determined By Nucleotide Sequence
A nucleic acid sequence, the messenger RNA or mRNA, is translated into the protein it encodes by means of transfer RNAs interacting with the ribosomal apparatus. Transfer RNAs bind to three nucleotides at a time and thus divide the nucleic acid sequence into triplet codons, each specifying one amino acid.
Don’t Miss: What Is Damping In Physics
Is Overproduction Of Offspring Evidence For Evolution
As more offspring are produced, there will be less resources available to other members of the population. If there is an over production of offspring this will result in a struggle for survival within the species as the resources become scarce and individuals in the population will start to compete for these.
Evolution Explains The Origin Of Life
It is a common misunderstanding that evolution includes an explanation of lifes origins. Conversely, some of the theorys critics believe that it cannot explain the origin of life. The theory does not try to explain the origin of life. The theory of evolution explains how populations change over time and how life diversifies the origin of species. It does not shed light on the beginnings of life including the origins of the first cells, which is how life is defined. The mechanisms of the origin of life on Earth are a particularly difficult problem because it occurred a very long time ago, and presumably it just occurred once. Importantly, biologists believe that the presence of life on Earth precludes the possibility that the events that led to life on Earth can be repeated because the intermediate stages would immediately become food for existing living things.
However, once a mechanism of inheritance was in place in the form of a molecule like DNA either within a cell or pre-cell, these entities would be subject to the principle of natural selection. More effective reproducers would increase in frequency at the expense of inefficient reproducers. So while evolution does not explain the origin of life, it may have something to say about some of the processes operating once pre-living entities acquired certain properties.
Read Also: What Does Ide Mean In Chemistry
Why Is Molecular Homologies Important
Molecular homology is an important concept in modern evolutionary biology, used to test the relationships between modern taxa, and to examine the evolutionary processes driving evolution at a molecular level. It is a rapidly changing field, and one that students who wish to “explore evolution” should surely understand.
How Does Molecular Evolution Work
Molecular evolution looks at how molecules, such as DNA and proteins, change over time. Because some amino acids have more than one possible codon, not every change to the DNA sequence will change the amino acid in the protein. Other mutations to DNA are adaptive, giving an advantage to the organism over others.
Read Also: What Is High School Level Math
What Kind Of Evidence Do Scientists Use To Determine Evolutionary Relationships
Evidence of evolutionary relationships include: similarities in body structure, fossils, protein structure, similarities in DNA, and similarities in early development. Know how fossils are formed, named, and how scientists determine fossil age.
What is evolutionary relationship in biology?
The evolutionary relationships of ancestral species and their descendants can be diagrammed using branching evolutionary trees. The root of a phylogeny represents the common ancestor of all the descendants in the tree. The descendant taxa, or groups, appear at the tips of the tree.
Why are biological molecules important?
Biomolecules are important for the functioning of living organisms. These molecules perform or trigger important biochemical reactions in living organisms. When studying biomolecules, one can understand the physiological function that regulates the proper growth and development of a human body.
How Do Fossils Provide Evidence For Evolution Ks2
Fossils are imprints of long dead plants and animals found in rocks. They are important because they were formed many millions of years ago. This means they can tells how plants and animals on earth used to look. Fossils are good evidence for evolution becuase they show that living things have changed over time.
Read Also: Algebra 2 Exam Review Packet Answers
How Does Molecular Biology Support Natural Selection And Evolution
Molecular biology has supported and extended our understanding of evolutionary relationships based on traditional anatomy. Heritability and variation in traits are essential parts of Darwins theory of evolution by natural selection. Molecular biology has clarified the nature of genes and the sources of variation.
What Is Molecular Biology How Is It Evidence To Support The Theory Of Evolution
Molecular biology has supported and extended our understanding of evolutionary relationships based on traditional anatomy. Heritability and variation in traits are essential parts of Darwins theory of evolution by natural selection. Molecular biology has clarified the nature of genes and the sources of variation.
How does molecular biology provide evidence for evolution quizlet?
Molecular biology, the study of genes and DNA, can also be used to trace the process of evolution. We now know that homologous genes exist in similar organisms. These homologous DNA sequences provide evidence of a common ancestor. Closely reltaed organisms have similarities in their DNA.
How do scientists mainly use molecular biology to provide evidence of evolutionary relationships between two groups of organisms?
Because of mutations, the sequence of nucleotides in a gene gradually changes over time. The more closely related two organisms are, the less different their DNA will be. It determines evolutionary relationships among organisms, and it indicates the time in the past when species started to diverge from one another.
Don’t Miss: Chapter 12 Chapter Test B Geometry Answers
Creationism And The Evidence For Evolution
Some creationists cite what they say is an incomplete fossil record as evidence for the failure of evolutionary theory. The fossil record was incomplete in Darwin’s time, but many of the important gaps that existed then have been filled by subsequent paleontological research. Perhaps the most persuasive fossil evidence for evolution is the consistency of the sequence of fossils from early to recent. Nowhere on Earth do we find, for example, mammals in Devonian strata, or human fossils coexisting with dinosaur remains. Undisturbed strata with simple unicellular organisms predate those with multicellular organisms, and invertebrates precede vertebrates nowhere has this sequence been found inverted. Fossils from adjacent strata are more similar than fossils from temporally distant strata. The most reasonable scientific conclusion that can be drawn from the fossil record is that descent with modification has taken place as stated in evolutionary theory.
Mammakian land ancestor Ambulocetus
Special creationists argue that “no one has seen evolution occur.” This misses the point about how science tests hypotheses. We don’t see Earth going around the sun or the atoms that make up matter. We “see” their consequences. Scientists infer that atoms exist and Earth revolves because they have tested predictions derived from these concepts by extensive observation and experimentation.
Rodhocetus Balaenoptera
How Is Molecular Evidence Used As A Source Of Evidence For Evolution
Molecular similarities provide evidence for the shared ancestry of life. DNA sequence comparisons can show how different species are related. Biogeography, the study of the geographical distribution of organisms, provides information about how and when species may have evolved.
Why is molecular data used in determining how related one species is to another?
Today, almost all evolutionary relationships are inferred from molecular sequence data. This is because: DNA is the inherited material. We can now easily, quickly, inexpensively and reliably sequence genetic material.
Recommended Reading: How Did Geography Influence The Greek Way Of Life
Molecular Evolution Methods For Detecting Compensatory Evolution
Several molecular evolution analysis methods have been proposed to find the signature of compensatory evolution. One approach is to infer conditionally deleterious mutations in a particular species. Deleterious mutations in one species sometimes do not show any phenotypic defect in other species with different genetic background these mutations are likely to be compensated by other mutations. The studies of mammalian and Drosophila genomes showed that ~10% of pathogenic mutations are not deleterious in the other species, suggesting that compensatory mutations would be widespread in genomes .
E.J. Vallender, in, 2017
Evidence From Ecological Biogeography
Ecological biogeography helps in explaining and examining the distribution patterns of the various plants and animals from the viewpoint of their physiological needs and shows how they were related long ago, and is still related to their ecological niches.
Understanding the ecological along with the historical causes of present distribution patterns can help us to predict how the ancestral floras and faunas responded long before their evolution, and how their descendant species will respond to factors in the environment after their huge evolution and specialization, and thus help us to conserve their biodiversity.
Environmental factors such as temperature, humidity, salinity, predation-prey relationships, etc. are all considered as key elements in the ecological biogeography of many species.
When describing the ecological biogeography we also talk about the organisms tolerances and responses to changes in moisture, temperature, soil chemistry, illumination, and other factors.
And it is seen that not many species share the same ecological niche, and as only a few of the species that will ever share the same ecological niche, evolution will tend to separate them.
This shows why the ancestral species have highly adapted to the change in its ecological and environmental factors due to natural selection over time and has lead to the present formation of many new-related species.
Don’t Miss: Mitty High School Summer Geometry
What Molecules Do We Look At For Molecular Evidence
Molecular evidence for evolution also includes: The same biochemical building blocks, such as amino acids and nucleotides, are found in all organisms, from bacteria to plants and animals. Recall that amino acids are the building blocks of proteins, and nucleotides are the building blocks of DNA and RNA.
Chapter 2 Evidence For Evolution
Darwin described evolution as descent with modification. It turns out that he was not the only one to think about the ever-changing world in this way. Another prominent naturalist of the time, Alfred Russel Wallace, independently conceived the theory of evolution through natural selection. Like Darwin, Wallace conducted extensive fieldwork in the tropics and was a meticulous observer of the natural world. In 1858, Wallace wrote a letter to Darwinwho was by then an eminent scholar but had not published his views on evolution yetdetailing his own ideas about natural selection. This led to the joint publication of short abstracts detailing Darwins and Wallaces views of evolution, and more importantly, it motivated Darwin to finish and publish his famous work, On the Origin of Species, in 1859. So, why does most of the credit for formalizing evolutionary theory go to Darwin rather than Wallace? Well, Darwin was undoubtedly first, ruminating on his ideas about evolution for decades before deciding to publish. As a consequence, he was able to introduce his views in much richer detail and provided many lines of evidence in support of his theory.
Explore More
To learn more about Alfred Russel Wallace, listen to He Helped Discover Evolution, And Then Became Extinct, an NPR story published on the 100th anniversary of his death.
You May Like: How To Calculate Average Uncertainty In Physics
Creationism And The Evidence Forevolution
Some creationists citewhat they say is an incomplete fossil record as evidence for the failureof evolutionary theory. The fossil record was incomplete in Darwin’stime, but many of the important gaps that existed then have been filledby subsequent paleontological research. Perhaps the most persuasivefossil evidence for evolution is the consistency of the sequence offossils from early to recent. Nowhere on
Earth do we find, forexample, mammals in Devonian strata, or humanfossils coexisting with dinosaur remains. Undisturbed strata withsimple unicellular organisms predate those with multicellular organisms,and invertebrates precede vertebrates nowhere has this sequence beenfound inverted. Fossils from adjacent strata are more similar thanfossils from temporally distant strata. The most reasonable scientificconclusion that can be drawn from the fossil record is that descent withmodification has taken place as stated in evolutionary theory.
Special creationistsargue that “no one has seen evolution occur.” This misses the pointabout how science tests hypotheses. We don’t see Earth going around thesun or the atoms that make up matter. We “see” their consequences. Scientists infer that atoms exist and Earth revolves because they havetested predictions derived from these concepts by extensive observationand experimentation.
Global Solutions To Local Problems
If our cells are teeming with non-optimal reactions, mistake-riddled molecules, and non-adaptive processes, each being slightly deleterious, but not enough to be eliminated by natural selection, how do cells, and by extension multicellular organisms, manage to survive? This situation is exacerbated if the genome is constantly absorbing slightly deleterious mutations that increase messiness. One can consider each of these mutations as a local problem with an associated cost to the fitness of the organism. When we consider that natural selection operates on each individual mutation, the cost of a single mutation may not be sufficient for its elimination. Instead, it appears that eukaryotic cells have what is known as global solutions to these local problems . The concept of global solutions shares many aspects with the idea of buffering systems advanced by Marc Kirschner and John Gerhart . It also shares many features with robustness advanced by other theorists . Global solutions are robust cellular mechanisms that maintain homeostasis. Often, these act to buffer not only environmental changes but also genetic changes. A good example would be chaperones, which not only prevent protein misfolding at high temperatures, but also promote the folding of proteins that have acquired destabilizing mutations. In the absence of sufficient chaperone activity, the effects of many such mildly deleterious mutations are revealed .
Read Also: What Is Repression In Psychology