Meet C. elegans - a modern Knowledge Constructor
Meet C. elegans - a modern Knowledge Constructor
60 million years of evolved simplicity
For an example of how the Knowledge Constructor works in real life, I present one of the simplest animals around - the famous C. elegans (Caenorhabditis elegans) nematode - the subject of millions of scientific experiments.
Let’s see how C. elegans lives by the Knowledge Constructor principle and the Laws of Life.
C. Elegans is a waypoint between the origin of life and human complexity. Physically simple, it has complex information systems and behaviors common to virtually all animals, including humans.
Meet C. elegans, a sixty million year old survivor
C. elegans is a tiny nematode (type of worm) abundant in soil almost everywhere on Earth. With only 302 neurons and 959 total cells, including 75 motor neurons driving 95 muscle cells, it is amazingly active and competent. C. elegans has proven survival skills, learns from experience, and can predict future events (knowledge). Its sensor suite is capable of detecting temperature changes of .003 degrees C, oxygen levels, a wide range of “smells” and, without eyes, can sense color.
Habitat: C. elegans primarily inhabits decaying organic matter, such as rotting fruit and soil, where it finds abundant bacteria to feed on.
Size: ~1mm long, 0.1mm wide
Mobility: Can travel quite fast, forward or backward, and handle a viscosity change of 10,000:1 - like the difference between walking through air and swimming through Jello.
Sexual habits: Unlike humans, who store excess energy in fat, C. elegans stores its energy profits in gametes that can produce offspring. During its short lifetime, it can produce from hundreds to a thousand offspring. In order to maximize reproduction, it is a hermaphrodite and can fertilize itself if there are no suitable males around.
LIfe span: After hatching, C. Elegans can harvest sufficient energy (eat enough bacteria) to pass through four larval stages and begin reproducing in just 48 hours. A mature adult may survive for up to several weeks, but many only last for a few days.
If the environment is not favorable, the C. elegans larva can go into a “low power” mode and survive for many weeks until conditions improve.
Let’s explore how the remarkable C. elegans manages the Laws of Life, as it has for over 60 million years.
NOTE: The following numbered lists are presented, with editing and fact-checking, from my AI research assistant. My comments are in italics.
Law of Life #1 - Survival (link)
Here is an excellent video showing the neural system of C. elegans in 3D.
1. Dauer Formation: The dauer stage is perhaps the most well-studied environmental response in C. elegans. When environmental conditions are unfavorable — such as a lack of food, high population density, or elevated temperatures — the worms can enter this specialized, non-reproductive, and stress-resistant larval stage. This dauer state is a suspended animation, allowing the worm to survive for extended periods without food. Once conditions improve, C. elegans can exit the dauer stage, resume development, and progress to reproductive maturity. Sensory inputs and molecular signaling pathways govern the decision to enter or exit dauer, notably the Insulin/IGF-1 signaling (IIS) and TGF-beta pathways.
Information systems cooperate to control behavior.
2. Chemotaxis: C. elegans can sense and move towards or away from various chemical cues in its environment. They utilize this ability to locate food (like bacteria) or avoid harmful substances. Specific sensory neurons in the worm can detect these chemical gradients, leading to a directed movement or behavior.
Sensors receive chemical energy, C. elegans can learn which “smells” are good or bad and use that knowledge to expend energy to move towards or away.
3. Thermotaxis: C. elegans also responds to temperature changes. They can remember the temperature at which they were cultivated and will move towards that temperature when placed in a thermal gradient. The AFD thermosensory neurons regulate this behavior.
4. Osmotic Stress Response: When faced with high osmotic conditions, C. elegans can activate specific protective mechanisms to cope. These include the synthesis of certain molecules, like glycerol, which can function as osmoprotectants. The response to osmotic stress also involves changes in gene expression patterns, leading to the production of proteins that help protect cells from the adverse effects of such stress.
The sensing of osmotic stress, knowing what to do about it, and taking action to alter gene expression is an example of a dependent Knowledge Constructor operating within the C. Elegans superorganism.
5. Starvation Response: When deprived of food, C. elegans not only can enter the dauer stage, as mentioned but also show behavioral changes like increased locomotion in search of food. On a molecular level, starvation leads to changes in metabolic pathways, autophagy (a process where cells "eat" their own components to generate energy), and the expression of specific stress response genes.
6. Oxygen Sensing: C. elegans can sense and respond to varying levels of oxygen. At very high or very low oxygen concentrations, they display aversive behavior while preferring intermediate oxygen levels. This is interesting since, in their natural habitat (soil and rotting vegetation), oxygen levels can fluctuate. Specific neurons, like the URX, AQR, and PQR, play key roles in oxygen sensing.
These varied and complex survival responses involve multiple information systems operating as dependent Knowledge Constructors. They work independently and in concert to support the goal of survival for the overall C. elegans.
Law of Life #2 - Making a profit (Link)
Finding food: C. elegans has a variety of sensors and knowledge to help it hunt for edible bacteria. Once found, it settles in and grazes on the bounty.
Designed to make a profit: C. elegans has very little to consider in its short life other than how to harvest as much energy as possible as quickly as possible.
Storing energy: Unlike humans who convert excess food into fat, C. elegans converts surplus energy into reproduction. When conditions are optimum, it can push out 100- 1000 eggs over its lifetime.
Law of Life #3 - Using information (Link) to support Laws 1 and 2
From our macroscopic perspective, C. Elegans looks like a very simple and primitive animal. However, we find that it shares most of the major information systems used by our human bodies and many other living organisms.
Here are the major information systems in C. elegans:
1. Neuronal Information System: This encompasses the nervous system of the worm, including its 302 neurons and the various synaptic connections among them. It's responsible for sensory perceptions, motor functions, and behavioral responses.
2. Genomic Information System: This represents the genetic code stored in the DNA of C. elegans. It holds the blueprints for every protein and many functional RNA molecules, determining the worm's inherent traits.
3. Epigenetic Information System: While the genomic system holds the DNA sequence, the epigenetic system modulates gene expression without changing the actual DNA sequence. This includes mechanisms like DNA methylation, histone modification, and chromatin remodeling.
Each of these is a separate information system within the hierarchy of epigenetic systems.
4. Transcriptional and Translational Control Systems: After DNA, there's the process of transcribing it into RNA and subsequently translating RNA into proteins. Various regulatory mechanisms, including transcription factors, RNA-binding proteins, and microRNAs, influence these processes.
Again, multiple independent but interacting information systems
5. Metabolic Information System: The series of chemical reactions that occur within C. elegans to maintain life. It includes pathways for energy production, biosynthesis of critical molecules, and breakdown of waste products.
6. Cell Signaling Systems: These are the pathways by which cells communicate with each other, using molecules like hormones, neurotransmitters, voltage-gated calcium channels, and growth factors. They regulate processes from growth to differentiation to death.
7. Cell Cycle and Developmental Control System: This governs the process by which cells grow and divide, as well as the differentiation pathways that allow for the development of the organism from a single fertilized egg to a mature worm.
How does C. elegans know to stop growing at exactly 959 cells? Recent discoveries are showing how cells have complex communication and computation capabilities independent of the brain.
8. Reproductive Information System: This dictates how C. elegans produces offspring, encompassing the mechanisms of gamete production, fertilization, and embryo development.
9. Immune Response System: Though not as complex as in higher organisms, C. elegans still possesses an innate immune response to fend off pathogens.
10. Behavioral and Learning Systems: Apart from immediate neuronal responses, some mechanisms underlie behavioral adaptations, learning, and memory in C. elegans.
We humans tend to think that our brain is the end-all and be-all of our behavior. In reality, our behavior arises from a vast hierarchy of information systems rooted in our DNA and the DNA of the billions of bacteria, fungi, and virus hangers-on that populate our superorganism bodies.
11. Environmental Interaction Systems: These encompass all the mechanisms that allow the worm to sense and respond to its external environment, such as chemotaxis, thermotaxis, and osmotic balance mechanisms.
This is where knowledge rubber meets the action road - 54 motor neurons control 96 muscle cells for swimming forward and backward or adapting to changes in viscosity, dirt vs water, etc.
12. Homeostatic Control Systems: These systems ensure the internal stability of the worm, maintaining parameters like pH, osmolarity, and temperature within desired limits.
These are a whole lot of systems for an animal with only 959 cells to its name. Each cell may host a variety of these systems. In addition, each cell contains multitudes of internal cellular systems, like the mitochondria that produce power to run the cellular machinery. Each of the 959 cells is itself a superorganism for all the information machines operating within itself, doing their best to keep the cell alive and functioning as part of the 959 cell C. elegans superorganism.
How does C. elegans fulfill the Knowledged Constructor mandate to grow, reproduce, and evolve?
Growing
Given the environmental niche inhabited by C. elegans, large size is not necessarily a benefit. For reasons best known to itself, C. elegans limits its growth to 959 cells. However, between hatching from its egg, it grows through four distinct larval stages before reaching its reproductive adult stage. The development roadmap is precise for every cell division. And it all happens in about two days.
Reproducing
This is where most of the energy harvested by C. elegans ends up. It makes sense, considering its short life and uncertain life environment. However, it is well-specialized for adaptation and evolution. For example, during the dauer “low power” stage, its development is halted, but it can still have sex, and when conditions improve, it will mature and start reproducing. Very ingenious.
Evolving
Most C. elegans are hermaphrodites. They produce both gametes (eggs) and sperm and fertilize their own eggs as they pass through the birth canal.
When times are good, <0.2% of the newborn C. elegans are male. But, in times of stress, the percentage of males increases. Why is that?
1. Genetic Diversity: Outcrossing, mating between hermaphrodites and males, increases genetic diversity. This diversity can provide a broader range of genetic tools to handle different environmental challenges, thus potentially enhancing population survival.
2. Dilution of deleterious mutations: Continuous self-fertilization in hermaphrodites can lead to the accumulation of harmful mutations. Outcrossing can dilute the effects of these mutations.
3. Colonization of new habitats: With more genetic diversity, some offspring might be better equipped to exploit new environments or niches.
4. Adaptation: Genetic diversity can speed up adaptation to changing environments.
What have we learned?
Everything that happens in a living organism is the result of an information system or information machine controlling energy. Even in a “simple” organism like C. elegans, a vast array of information systems operate in a variety of substrates - molecular systems controlling gene expression, neural system machinery integrating sensor information to control physical movement, clocks and sequencers to control development and reproductive processes - the list goes on and on.
The operation of each of these internal machines and the success of their superorganism - in this case, C. ELegans - is determined and driven by their collective success at applying the Knowledge Constructor information machine principle to the inexorable Laws of Life.
So we can congratulate the humble species of C. elegans, now celebrating its 60 millionth birthday. We humans have a way to go.
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