Life & Evolution

Abiogenesis 🔧

Hypothesis & Facts

It should be understood that a hypothesis is an idea that rationally explains something and hasn't been fully investigated. A theory is a comprehensive explanation supported by extensive evidence.

Abiogenesis is the hypothesis for which non-living matter becomes living through a natural process. It is a fact that abiogenesis has never been observed and has had several failed attempts at replication in a controlled environment, therefore it remains a hypothesis. While that alone excludes it from being a theory by definition, deductive logic and supporting evidence of steps in the process push for abiogenesis as the only valid explanation for the origins of life. The question arises how, rather than if, it happened.

We won't get into the spectrum of false information surrounding life science in general, but there are a few debate tactics in heavy use we would like to point out that listeners and readers should train themselves to look for.

A straw man fallacy occurs when someone distorts or exaggerates another person’s argument, and then attacks the distorted version of the argument instead of genuinely engaging in a debate. This is the most common tactic for creationist arguments against evolution. One example of this is claiming that humans descended directly from monkeys, when in fact evolutionary theory posits a common ancestor shared by humans and modern primates. This oversimplification creates a false scientific concept.

Shotgun argumentation is when a person aims to dominate your attention with too many details for you to process at once, spouting off a series of so-called facts one immediately after the other immediately after the other, and so on, giving no pause for thought or two-way dialogue. If you're familiar with early 2000's conspiracy theory web documentaries such as Zeitgeist and related, and others claiming that Hilary Clinton was a reptilian, then you already know exactly what this is. Otherwise, spare yourself from venturing there.

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Chemical Process 🔧

Simple molecules combine to form both carbohydrates and amino acids. Carbohydrates are composed primarily of carbon, hydrogen, and oxygen, and are used as an energy source for cells. Amino acids contain these elements as well as nitrogen. The simplest molecule from which amino acids are formed is carbon dioxide. It combines with water to produce carbonic acid, an essential component of amino acids. Amino acids are the building blocks of proteins and are essential for various metabolic processes in the body, namely protein synthesis and repair.

Other molecules of interest are the phosphate group, a phosphorous atom bound to four oxygen atoms. It is essential for the creation of cell membranes and DNA.

Pentose sugar (deoxyribose in DNA) is obtained through a series of biochemical reactions involving various enzymes and substrates within the cell. It is ultimately derived from glucose molecules through a process called the pentose phosphate pathway (PPP).

Nucleotides are cyclamate-like molecules and the building blocks of deoxyribonucleic acid (DNA), made up of a nitrogenous base, a pentose sugar molecule, and phosphate group. They function in DNA by linking together to form the double helix structure, with the nitrogenous bases pairing up to create the genetic code. There are four types of nucleotides, the differences in their nitrogenous bases, adenine, thymine, guanine, and cytosine. Understanding the unique characteristics of each type of nucleotide is essential to comprehend how they function and interact in DNA and RNA molecules.

Nucleotides are also the building blocks of ribonucleic acid (RNA). DNA contains deoxyribose sugar while RNA contains ribose sugar, and instead of thymine uses uracil. RNA is similar to DNA but it's a separate molecule that carries out different functions in cells, including aiding in protein synthesis and gene regulation. RNA helps to essentially read genetic code and produce proteins using amino acids as the raw materials.

Ribosomes are components of cells that translate messenger RNA (mRNA) into instructions for processing chains of amino acids into specific sequences called polypeptides, basic protein. They create proteins for all cell types, playing a crucial role in cellular function. Ribosomes also create other ribosomes by synthesizing ribosomal proteins and ribosomal RNA (rRNA).

Proteins build muscles and tissues, repair cells, induce chemical reactions and provide structural support. They are comprised of both RNA and amino acids.

Lipids are organic molecules that are key component in the structure and stability of all cell membranes, and they also act as a barrier to govern what enters and exits a cell. Eight types of lipids are:

Fatty acyls
Glycerolipids
Glycerophospholipids
Sphingolipids
Sterols
Prenols
Saccharolipids
Polyketides

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Evolution 🔧

Modern Theory 🔧

The idea that evolution is a historical rather than observational science, therefore untestable and cannot be proven is a false belief. Evolution is both a historical and observational science, and has been supported through various scientific methods and evidence. It is a working theory.

Species change over time to adapt to their environment through genetic mutations. Genetic mutations occur randomly, and those that confer a survival advantage increase in frequency within a population, leading to evolutionary adaptation over time. Some genetic mutations can be controlled by various mechanisms such as DNA repair systems or gene silencing processes.

The control mechanisms can affect the offsprings genome during gamete formation or early embryonic development. Control mechanisms such as DNA repair systems can help fix damaged DNA before it is passed down to the next generation. Gene silencing processes can also regulate gene expression levels and prevent certain traits from being inherited.

Species survive through a breeding process called natural selection. Those better able to adapt to their environment are more likely to survive and reproduce.

Natural selection and genetic mutations are easy to confuse when looking at evidence, but are distinct processes in evolution. While mutations provide the raw material for variation, natural selection acts on this variation to drive adaptation to changing environments. Both mechanisms work together in shaping the diversity of life on Earth.

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Observed Evidence 🔧

Evidence of common descent includes similarities in anatomical structures across different animals, such as limbs and organs.

Fossil records demonstrate that ancient organisms had features that are found in modern-day animals and plants.

Changes in beak sizes of finches in the Galapagos Islands based on availability of different food sources is one of the most famous examples of evolution by natural selection. It played a key role in Darwin's theory of evolution by demonstrating how species can adapt to their environment over time.

Common genes to all life (355) are known as the core universal genes, and they are essential for basic cellular function.

Antibiotic resistance in bacteria is one example of genetic mutations where species change to adapt to their environment. The mutations in bacteria allow them to produce enzymes that neutralize the effects of antibiotics, much in the same fashion the human immune system starts producing cells to fight bacteria and viruses.

Mutations in sperm with increased age causing heritable mutations in offspring has been observed. This is likely a result of recent human evolution and random DNA damage accumulation. Understanding the relative contributions of these factors requires further study.

Menopause occurring later in women has been observed as a possible sign of recent human evolution, however, further research is needed to fully understand the underlying factors driving this trend. It should also be pointed out that menopause occurs earlier in most mammals compared to humans, suggesting that the prolonged reproductive capacity of human females might be a relatively recent evolutionary adaptation.

Recent human evolution includes the existence of a human gene called DARC, found in people of west Africa and most notably in the Cape Verde islands, which specifically protects individuals from malaria.

The last universal common ancestor (LUCA) refers to the single-celled organism that gave rise to all modern day life on Earth. This proto-organism lived around 4 billion years ago and likely existed in a hydrothermal vent system. No direct physical evidence exists of LUCA. Scientists use comparative genomics and molecular biology to inter its characteristics and evolutionary relationships with modern organisms.

The peppered moth evolved from light-colored to dark-colored forms in response to industrial pollution.

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Meanwhile 🔧

Anatomy & Physiology 🔧

Understanding these subjects is crucial for understanding evolution because it helps us understand how organisms have adapted to their environments. By studying the structures and functions of living organisms, we can trace the evolutionary changes that have occurred to shape them into the forms we see today.

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Ecology & Coevolution 🔧

Species within an ecosystem have an interconnectedness. Their interactions drive evolutionary changes over time. Understanding these dynamics can provide insights into the complexity and resilience of natural systems.

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Human Impact on Ecosystems 🔧

Habitat destruction is a huge concern that disrupts entire ecosystems, leading to loss of biodiversity and the extinction of entire species.

Deforestation has numerous effects, the most significant being loss of biodiversity, soil erosion, increased greenhouse gases, disruption of water cycles, and negative impacts on indiginous communities.

Carbon dioxide emissions increase the amounts of CO₂ in seawater. This reacts with water to form carbonic acid. While carbonic acid is identified as a molecule necessary for life as we know it, the reaction also releases hydrogen ions which lowers the ocean's pH levels, causing acidification. This effects marine life overall, but coral and shellfish are especially damaged by this, given their calcium carbonite shells.

Overfishing, excessive fishing practices, can lead to the collapse of fisheries, damage marine ecosystems, and ultimately have a cascading effect throughout an entire ecosystem. Loss of predator species will cause overpopulation of prey species, which can in turn deplete other resources like phytoplankton and zooplankton. This damages water quality and changes the entire structure of an ecosystem.

Industrial agriculture with large-scale farming practices that focuses on efficiency and profit often results in environmental degradation and resource depletion (specifically, monoculture farming, intensive irrigation systems, and synthetic fertilizers and pesticides).

Fossil fuel emissions release greenhouse gases like carbon dioxide and methane into the atmosphere, contributing to global warming. They also release pollutants like particulate matter, nitrogen oxides, and sulfur dioxide, which cause air pollution and negatively impact human health and ecosystems.

Plastic waste harms the environment in many ways. It pollutes oceans and waterways, disrupting marine life and contaminating the food chain. It also contributes to climate change, taking hundreds of years to decompose, and while doing so, releasing toxic chemicals into the soil and air. Chemicals from plastic waste can be ingested, damaging health.

Chemical runoff from factories, pollutants released into the environment, have always been a major problem since the industrial revolution. Heavy metals like lead and mercury, volatile organic compounds, and other hazardous chemicals continue to seep into soil and groundwater and posing serious health risks.

More can be done in addition tosustainable practices, reducing pollution and being more environmentally aware of our actions. Conservation efforts like reforestation, wetland restoration, protecting natural habitats, implementing sustainable land-use practices, fashioning wildlife corridors help to counteract many of these problems.

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Astrobiology 🔧

Where are all the Aliens? 🔧

The Drake equation: $$N=R_*\cdot f_p\cdot n_e\cdot f_1\cdot f_i\cdot f_c\cdot L$$ $R_*=$ star formation rate
$f_p=$ stars with planets
$n_e=$ potentially habitable planet per star
$f_1=$ probability of habitability at any time
$f_i=$ probability of civilization
$f_c=$ probability of civilization being detectable
$L=$ length of time civilization is detectable

The Drake equation is a thought-provoking tool, but its validity is limited by the sheer number of variables involved, many of which are still purely speculative. While the equation might be based on reasonable assumptions, it remains largely hypothetical and lacks concrete evidence to support its claims. In other words, it intuitively makes sense, but there's no way to test it without first discovering any life to begin with. Regardless, it's a useful framework for sparking discussions about the possibilities of extraterrestrial life, which need to be had.

There are several possible explanations why we have not yet detected signs of extraterrestrial intelligence. These include the possibility that intelligent life is rare or short-lived, that communication across vast distances is difficult, or that intelligent civilizations may self-destruct before they can make contact with others.

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Habitability Requirements 🔧

Temperature and state of water on the planet. It must be between -15 C and 122 C and with reasonable availability.

Light enough for photosynthesis, 100 AU light levels

Light and redox energy sources

UV and ionizing radiation limits

Nitrogen

Over .01 atms of O2 is needed to support life as we know it.

We're on the right track with our known habitability requirements, but we might also be overlooking some crucial factors. Extremophiles are organisms that have the ability to thrive in environments we typically consider hostile. Even they require liquid water in order to survive, but the acceptable lack of how much impedes our current understanding of what makes an environment habitable. We should also focus on the presence of complex organic compounds in conjunction with energy sources rather than just water.

The discovery of complex organic molecules in space, such as carbonic acid suggests that the raw materials for life are widespread in the universe. The presence of carbonic acid in space could indicate the existence of water, which is essential for life as far as we know it. This increases the chances that life could emerge and thrive in environments previously considered inhospitable.

Over ten years ago, the scientific community decided that silicon-based life forms are impossible, due to the differences in silicon's chemical properties compared to carbon. However, it was a simple conclusion that doesn't entirely rule out the possibility. New discoveries and advancements in fields like biochemistry and astrobiology might challenge those earlier assessments and provide alternative perspectives.

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Potentially Habitable Exoplanets 🔧

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Life & Evolution

This page is incomplete and still undergoing revisions.