Chapter 15: Evolution (C4743902)

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Legend: Key principles // Storyline

1 Evolution

Gene pool is the set of all alleles, in a given population. Evolution is a change in the gene pool. Evolution relates to the genotypes that make up a population, as supposed to phenotype which is what can be observed. This is because individuals could be carrying alleles that are not expressed.

“How does evolution program moral and even aesthetic values?” Mandy asked, “How do we recognize beautiful members of the same sex, or of other species, when it provides no selective advantage?”

“It doesn’t,” Blaire replied, “for example, Darwinism fails to explain why so-called ‘cougars’ are more attractive than some younger girls.”

“Corporate 30yo me was a cougar ,” Mandy giggled.

“Evolution doesn’t explain you, Mandy,” Jamie laughed.

The various taxonomical ranks of living organisms, in order of increased specificity, is kingdom, phylum (or division), class, order, family, genus and species, which can be memorized with the mnemonic “King Phillip Came Over From Germany – So?”.

© 2014 MR. SHUM

All species are given a two-part name, the first part being the genus and capitalized, and the second part being the species and in lower case, both written in italics. For example, humans are referred to as Homo sapiens. In actuality however, humans are in the kingdom Animalia, phylum Chordate, class Mammalia, order Primates, family Homonidae, genus Homo, and species Sapiens.

“My goodness Jamie! The italic way of writing names reminds me of how they write court case names,” Mandy commented, “for example, Donoghue v Stevenson [1932] UKHL 100: that was that snail-in-a-drink case, right?”

Humans are found in the phylum chordate. Humans are also vertebrates, which are animals with backbones. Vertebrate is a subphyla of chordates. This also means not all chordates have backbones. Chordate are distinct because they have:

  • Bilateral symmetry, meaning that half their body is a mirror image of the other half
  • Are deuterostomes, defined , meaning the anus is developed at the blastopore, and another hole is made for the mouth
  • Coelom, which is a body cavity, which are precursors to the peritoneal, pleural and pericardial cavities
  • Notochord, a flexible rod-shaped body, later forming part of the spine
  • Pharyngeal slits/pouches, which are precursors to the gill slits
  • Dorsal nerve chord, precursors to the brain and spinal cord
  • Tail

Species are organisms adapted to an ecological niche. Niche is the way in which a species exploits its environment. Each species has a separate, unique niche, meaning different species cannot occupy the same niche. Species are defined as organisms able to reproduce in the same population to produce fertile offspring. For example, a dog is a subspecies of wolf, and therefore can mate with a wolf to produce fertile offspring, but as it doesn’t reproduce in the same population, isn’t technically the same species.

Geographical isolation of a species eventually leads to the formation of a new species, known as speciation. Geographically isolated populations are known as allopatric, and geographically cohabiting populations are known as sympatric. An example of geographical isolation is the separation of fish into different lakes. The reasons why geographical isolation leads to speciation include:

  • Founder effect, where the founders of the new population, were different from the original population
  • Different mutations will arise in the two populations
  • Dissimilar selective pressures are subjected to the two populations

Ecological isolation include:

  • Seasonal isolation, where the difference in timing of breeding seasons, prevents two populations from mating
  • Behavioral isolation, where the difference in courtship rituals, prevent two populations from mating
  • Mechanical isolation, where the opposing sexes are unable to physically mate due to differences in size or other structure
  • Gametic isolation, where gametes are unable to attract one another, thereby inducing fertilization
  • Developmental isolation, where fertilization does occur, but the embryo doesn’t develop completely
  • Hybrid isolation, where the offspring can be born, but is less fit. Darwinian fitness is the ability to survive, reproduce, and have offspring subsequently reproduce. For example, donkeys can have long life, and hence have many offspring. However, if a donkey only mates with a horse, the offspring are mules, which are infertile

“The moral argument: Premise (1) If God doesn’t exist, objective moral values don’t exist. Premise (2) Objective moral values do exist. Conclusion (3) Therefore, God exists,” Mandy remarks.

“As Darwin writes in The Descent of Man ‘If… men were reared under precisely the same conditions as hive-bees, there can hardly be a doubt that our unmarried females would, like the worker-bees, think it a sacred duty to kill their brothers, and mothers would strive to kill their fertile daughters, and no one would think of interfering’,” Blaire starts.

“If morality is simply the product of adaption, to say that human morality is objectively valuable than these bees, is to enter into specie-ism, the unjustified bias of one’s own species,” Mandy replied, “rather, like the lion who kills but doesn’t murder the zebra, and the great white shark who forcibly copulates but doesn’t rape a female, humans cannot err.”

“But there is objective right or wrong, independent of whether anyone believes in it,” Blaire continued, “even if the Nazi had won WWII, the Holocaust is still evil.”

“A truly ‘postmodern world’ is an impossibility, that would be unlivable. No one is truly postmodern distinguishing between a label for Panadol and rat poison, and in other matters of science, technology, and engineering. They are only relativistic and pluralistic in religion and ethics, which isn’t postmodernism, but verification-ism of modernism.”

There are two main reproductive strategies for encouraging fitness, neither of which is superior, but depends on the environment. The strategies include:

  • K strategy, which produces few offspring, but focuses its energy on ensuring the survival of its offspring. K strategists prefer stable or predictable environments. K strategists are optimal for environments with limited resources, therefore requiring competition. Resources are limited, because of density-dependent factors, which are factors which only affect the population when population increases (i.e. becomes more dense). Examples of density-dependent factors are predators, competition and disease. An example of a K strategist is the elephant, which gives birth intermittently, and takes care of its offspring
  • R strategy, which focuses its energy on producing a large number of offspring, but applies little effort to ensure the survival of its offspring. R strategists prefer unstable or unpredictable environments with plentiful resources. As resources are near-unlimited, R strategists depend on density-independent factors, which are factors which affect everyone in the population regardless of population size. Examples of density-independent factors are weather disturbances. R strategists grow rapidly, mate early, and die young. An example of an R strategist is the frog, which can lay many eggs, but neglects its young

Sexual reproduction requires a lot of energy, as it involves courtship display, including the special postures, bright colors, and the mating dance. These behaviors however, diverts the organism from other pursuits, and so therefore increases their susceptibility to predation, and thus reduces fitness. Also, females are less fit whilst carrying their offspring.

“Reminds me of that time you were checking out that girl, and you smashed into a pole,” Mandy noted, “You naughty boy Jamie, she took away your fitness LOL!”

“Of course, remember our teen years,” Mandy continued, “The dancing, fluoro colors, and duck face poses?”

“So different, yet so similar to the animal kingdom.”

Population growth curves are sigmoidal. Populations plateau once a carrying capacity has been reached. Carrying capacity is the maximum population size an environment can sustain indefinitely, as restrained by the resources available.

Divergent evolution is where groups within a population evolve away from each other, leading to speciation. Convergent evolution is where similar structures are acquired in unrelated lineages, as a result of adaptation to the analogous environment. Traits that are not shared ancestrally, and arose independently, are known as homoplastic. An example of a homoplastic trait is the wings found in insects, birds and bats. These animals have each evolved independently to form these capabilities.

Symbiosis are the relationships formed between different species. They include:

  • Mutualistic, where both species benefit. An example of mutualism is the bacteria E. coli, as described , as benefiting humans by providing vitamin K, and receive benefit from a stable supply of nutrients
  • Commensalistic, where one species benefits, and the other is unaffected. An example of commensalism is barnacles which live on whales, receiving benefit by being transported all over the ocean to feed, whilst the whale is unaffected
  • Parasitic, where one species benefits, and the other is harmed. An example of parasitism is human and lice, where the lice benefits, but the human is harmed

Hardy-Weinberg equilibrium is that the gene pool (allele frequencies) will remain constant, unless so long as its assumptions are held:

  • Large population
  • Mate selection is random
  • No mutation, meaning forward mutation [into a mutant], and backward mutation [into a wild type] is constant
  • No immigration or emigration, or if there is, that it doesn’t alter the gene pool
  • No natural selection, meaning no phenotype is more fit than another

Evidently, these assumptions are not met, meaning evolution does occur.

Given that in the gene pool, [mathjax]p[/mathjax] is the percentage chance of one allele of a genotype, and [mathjax]q[/mathjax] is another percentage chance of another allele in a genotype, [mathjax]p+q=1[/mathjax]. Both sides can then be squared, providing [mathjax](p+q)^2 = 1[/mathjax], which is better suited for later purposes. Also, inserting the two allele frequencies ([mathjax]p, q[/mathjax]) into the Punnett square [as you would allele, since probabilities are multiplied, to find the probability of the two constituent events occur], the results are [mathjax]p^2, pq, pq[/mathjax] and [mathjax]q^2[/mathjax], and since two terms are analogous, this can be reduced to, [mathjax]p^2[/mathjax] representing the fraction of homozygotes of [mathjax]p[/mathjax], [mathjax]2pq[/mathjax] representing the fraction of heterozygotes, and [mathjax]q^2[/mathjax] representing the fractions of homozygotes for [mathjax]q[/mathjax]. Note that the only options (as shown by the Punnett square) for the alleles to split into are the homozygotes of and , or heterozygotes. Therefore, [mathjax]p^2 + 2pq + q^2 = 1[/mathjax]. Equating the two equations, [mathjax](p+q)^2 = p^2 + 2pq + q^2[/mathjax].

The binomial theorem is that the expansion of [mathjax](x+y)^n[/mathjax] is the sum of the terms [mathjax]ax^b y^c[/mathjax], where [mathjax]b+c=n[/mathjax], and [mathjax]a[/mathjax] can be obtained from Pascal’s triangle from the row [mathjax]n+1[//latex]. Additionally, [latex]c[/mathjax] starts from [mathjax]0[/mathjax] and increases by one each time until [mathjax]n[/mathjax], and [mathjax]b[/mathjax] starts from [mathjax]n[/mathjax] decreasing by one each time until [mathjax]0[/mathjax]. For example, for [mathjax](p+q)^2[/mathjax], given [mathjax]n=2[/mathjax], the Pascal triangle row used is row [mathjax]2+1=3[/mathjax], which states [mathjax]"1, 2, 1"[/mathjax]. Therefore, the terms are [mathjax]qp^2 q^0, 2p^1 q^1, p^0 q^2[/mathjax] or adding them up together, [mathjax]p^2 + 2pq + q^2[/mathjax]. Of course, algebraic expansion can be used for easier terms, but where there are high powers, the binomial theorem is more straightforward. Note therefore, that the expansion of the left hand side of the equation is equal to the right, quod erat demonstrandum.

© 2014 MR. SHUM

The Big Bang theory is that the development of the Universe occurred around 13 billion years ago, with a bang, where hot matter expanded rapidly. The matter originally formed was the atomic nuclei of hydrogen and helium, possible due to rapid cooling. Then, over hundreds of thousands of years, electrons stuck to the nuclei to make complete atom. About 12 billion years ago, the first stars and galaxies were formed as a result of the coalescing of these primordial elements through gravity. About 4.5 billion years ago, the solar system, including the earth, was formed, by the coalescing, again through gravity, of a cloud of gas and dust left over from the Sun’s formation. Life on earth begun 3.8 billion years ago.

“The Kalam cosmological argument: Premise (1) Whatever begins to exist has a cause. Premise (2) The Universe began to exist. Conclusion (3) Therefore, the Universe has a cause,” Mandy started.

“Stephen Hawking states that before the Big Bang, there was no space nor time. Therefore, the creator must transcend space and time, and be immaterial,” Blaire commented, “just like the theistic God.”

“To negate that everything has a cause by noting that virtual particles in a quantum mechanical vacuum can spontaneously appear, is fallacious,” Mandy replied, “These particle-antiparticle pairs are in fact a fluctuation in a quantum vacuum, which is not nothing, but rather, a sea of energy.”

The first life source is the prokaryote, which based on the heterotroph hypothesis (from , heterotroph meaning to eat others for its source of carbon), lived in an aquatic environment full of organic molecules, including ATP, which were absorbed into the cell for cellular function. As these heterotrophs exhausted their food supply, autotrophs would replace the heterotrophs as dominant life forms. Fermentation released carbon dioxide into the air, which now permitted autotrophs, which as defined  are organisms which can produce energy from its surroundings. First, this included chemotrophic autotrophs, which as defined , source energy from chemicals, using its carbon dioxide air as its carbon source, and ATP energy to construct more complex molecules. Subsequently, phototrophic autotrophs were formed, which as defined , can use sunlight to generate energy. Eukaryotes were first formed around 2 billion years ago. About 1.5 million years ago, humans separated from the line of the chimpanzees and gorillas. Between 30,000 years to 200,000 years ago, Neanderthals lived. Neanderthals are now extinct species within the genusHomo”, therefore closely related to humans. The first city was formed approximately 12,000 years ago.

So that was how Jamie and Mandy redeemed themselves of their Sin, and re-found love.

They had developed many qualities wholly apart from another, which as Mandy says, “couldn’t have happened otherwise, and was achieved by God’s perfect timing,” and their reunion permitted them to regain some of that youthful spark they had lost in the corporate world.

And they were madly in love.

“Madly ,” Mandy iterated.

“Like two giddy teenagers ,” Jamie laughed.

“So they married, and lived happily ever after ,” Blaire noted, “like the Cinderella and Prince Charming.”

“Well, that’s until reproduction, now THAT’S a story of its own ,” Blaire laughed, “you two still going at it into your 40’s . Classic Jamie and Mandy .”

2 Comparative anatomy

Comparative anatomy studies the similarities and differences in anatomy of different organisms. It provides evidence for evolution, indicating organisms share a common ancestor, through:

  • Homologous structures, which are structures consisting of the same basic parts can be found common in different species, yet serve completely different functions. This is used to explain that random mutation and natural selection lead to better adaption based on habitat
  • Analogous structures, which are structures in organisms with different ancestors, but were evolved as a result of living in a similar environment, to serve the same purpose

“J.P. Morgan was a financier who dominated corporate finance in his day, arranging the merger to form General Electric, and the merging of Andrew Carnegie’s Steel Company,” Mandy remarked, “He is considered one of the richest men of all time. In his Will, he states:”

"I entreat my children to maintain and defend, at all hazard, and at any cost of personal sacrifice, the blessed doctrine of the complete atonement for sin through the blood of Jesus Christ, once offered, and through that alone.” (Article I of J.P. Morgan's Last Will and Testament, executed January 4, 1913)

“And I do the same,” Mandy remarked.


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Chapter 15: Evolution - Biology - Pre-med science - MR. SHUM'S CLASSROOM