Three main domains that formed the distinct branches of the tree were identified as: Bacteria, Archaea and Eukaryotes. This biodiversity came out as genetically varied descendants of the common ancestral community of primitive cells.
Darwin commented on this model in his book, where he gave a summary of his views:
A biochemist called Ford Doolittle further refined the tree of life model by introducing cross-links, which implied that many common ancestors passed their genetic material through their evolutionary paths across one domain to another to evolve more varied species. This ‘cross-linking’ was called Horizontal Gene Transfer (HGT). HGT is defined as: “a mechanism by which an alien gene from a source "organism X," moves into, or is taken into, a given cell and is somehow incorporated into the genetic complement of the cell.” [(4)]
It proved that species from different domains were related to each other, if they both shared the same common ancestor.
Dr. Ford Doolittle stated during the introduction of Figure 2 to the world, he said: “...downgrading the tree of life doesn't mean the theory of evolution is wrong - just that evolution is not as tidy as we would like to believe.” [(6)]
Here is evidence that shows that the scientific community doesn’t have entire faith in the system of evolution. This is what the majority of scientists want not to happen.
Methods and processes
Biologists are still determined to gather more and more evidence to build up into proving the Theory of Evolution as a fact.
Two reliable sources of evidence are those found in fossil records and analysing the molecular phylogenetics (genetic structure) of species.
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Palaeontology is “the earth science that studies fossil organisms and related remains” [(7)]
Palaeontology is an umbrella term in science whereby it is subdivided into many other fields, such as taphonomy: “Study of the processes of decay, preservation, and the formation of fossils in general.” and micropalaeontology: “Study of generally microscopic fossils, regardless of the group to which they belong.” [(8)]
Why do scientists use palaeontology? They use it because it helps draw links between early and later generations of species. It’s actually a fundamental process that made Figure 1 and 2 true. (See Pg 3 and 4)
Scientist Georges Cuvier (1769-1832) attempted to explain fossils. “He was able to show, sometimes from the merest fragments of bones, the relationships between living organisms and a fossil of an extinct form of life – part of the basis of modern palaeontology.” [(9)]
This is evident that palaeontology is a vital branch in science.
This is also a fairly reliable process because palaeontology analyses fossils which are reliable due to the fact that they don’t change in morphology (physical/phenotypical feature) and are preserved imprint of the fossilised species.
If you clearly look at Figure 3, you can see that it closely resembles the modern day angler fish, and even though this fossil was estimated to have been alive some 150 million years ago, there are similar morphological similarities such as visible fish scales, bones and dorsal fin.
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Molecular phylogenetics is described as the “analysis of structures of many different chemicals and genes to identify the inter-relationships between groups of organisms.” [(12)]
Figure 5 shows that the red vizcacha rat from South America is closely related to the East African mole rat. These two organisms also share the same common ancestor as the Asian brushed tailed porcupine. Even though these three organisms have very little similarities morphologically, they do seem to be comparable when analysing their molecular phylogeny.
Molecular phylogeny is extremely reliable because DNA/RNA structures hardly differ amongst organisms of the same species, therefore there is little chance of getting a error when analysing the phylogeny. Also, DNA/RNA never changes. Morphological observation has flaws however, where certain organisms can physically have phenotypical features removed due to external stimuli.
By gathering enough similarities through research in palaeontology and molecular phylogenetics, biologists hope to fill the missing links in the evolution story that will help them understand better about how life on Earth evolved.
Ethical/Social Implications
Ethical implications of evolution are that the contemporary idea of the ‘Theory of evolution’ has based a foundation around the Darwinist approach, as have other “ethical and social system” [(14)]. This is seen as narrow minded thinking due to the fact that there are other rational explanations, but they have been shunned aside because they the majority of the proponents tend to believe Darwin and reject all other approaches.
Socially, some people don’t believe that humans have the right to say that we are related to the modern—day apes because we descended from common ancestor. On an unbiased note, some religions would see it as an offensive concept that denies their freedom of thought. This would mean that science couldn’t progress and might possible be stuck with a single, dominant theory that some people do not want to believe. This is what the scientific community is trying to prevent, after all.
Advantages of the methods are that molecular phylogenetics is reasonably reliable because DNA/RNA doesn’t change unless affected by external stimuli: radiation. However, most of the time, it is a flawless process. Fossil observation is advantageous because it allows scientists to analyse their morphological features. Fossils provide a snapshot into the past, and this is useful for drawing links between modern day and ancient organisms.
Disadvantages of using molecular phylogeny includes the implicated fact that studying DNA/RNA structures is extremely difficult as they are so small, and possible chances of human error can be made when comparing them with other DNA. Disadvantages of using fossil records are that certain fossilised organisms that may share similar morphological similarities to their assumed descendent, in actual fact, their DNA aren’t even closely related thus meaning that using fossil records can be a flawed.
What other methods can they use to help aid them in their quest for evolutionary knowledge?
What scientists can do is to look at a local habitat and see how well it is adapted to its niche. This will be based on phenotypical observations, but covers a factor of adaptations.
The study will see if “species are well adapted to their niche...These adaptations may be of different kinds including anatomical, physiological and behavioural.” [(15)]
Anatomical adaptations can include emphasised features such as cactus spines. They enable it to defend itself against predators that may be in search of water in the desert. Its small surface area doesn’t allow a lot of water to escape the plant. This shows that the plant has a design that it is well suited to its environment.
Physiological adaptations refer to the biochemical pathways; the mechanism explaining why the body works in a particular way. For example, “diving mammals can stay under water for far longer than non-diving mammals without drowning.” [(15)]
Behavioural adaptations refer to attitudes and reactions to the environment. For example, wolves travel in packs to effectively make their hunting more efficient. The wolves co-ordinate their attacks, so that they can take down larger prey – something a lone wolf could never achieve.
This can be argued that a design such as this can only be accomplished through successful and beneficial evolutionary traits being passed on from earlier ancestors.
This is a key idea in natural selection, where survival of the fittest states that for a successful species to emerge, there must be beneficial genes passed on from earlier ascendants.
Coming full circle, we can see that evolution can be explored in many ways. What scientists need to do is to further their research so that they in the future, perhaps, a unified theory may prevail.
Bibliography
Evaluation
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