Biology's Why Questions

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In summary, the conversation discusses the use of "why" questions in physics and biology. While "why" questions are not typically part of physics, they are often addressed in biology, especially in regards to the goals and adaptive traits of living organisms. The conversation also explores the concept of natural selection and how it plays a role in the evolution and persistence of life. Overall, the difference between biology and other sciences, such as physics and chemistry, is highlighted.
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I started this thread inspired by the following quotes from the often provocative @PeterDonis:

PeterDonis said:
No, "why" questions are not part of physics, or indeed of any science. At least not if you expect a final answer to any of them.
PeterDonis said:
And that will be true of any "why" question in any science: ultimately it will come to a point where the only answer is "just because".

Biology is a field that addresses several kinds of "why" questions.
Unlike physics and chemistry, biology often deals with populations of animated entities with agent like properties. These can generate "why?" questions.
Living entities have evolved goals, in order to maximize their reproductive potential. The reason for their goal's existence can therefore be addressed with "why?" questions.
Their self-powered pursuit of these goals is, to a large extent, why biology, although constrained to follow the "laws of physics", can evade many normal physical limitations (such as not running down to a thermodynamic equilibrium, while alive), in order to gain their place the world.

The simplest kind of "why?" question (which may be a "how" question) involves direct causal sequences, such as: "Why does a frog's leg twitch when the nerve is electrically shocked?".
These can be referred to as proximal explanations or causes (being a more immediate cause of the event under consideration).
These might end up in Peter's category of "ultimately it will come to a point where the only answer is "just because"", when the explanations bottom out in the physics and chemistry underlying the situation. Or maybe they are just a how question restated.

Another set of "why?" questions are of a more ultimate kind (further removed from the event under consideration, a more ultimate explanation for a particular event).
In biology, these involve questions like "why did the frog evolve to have muscle movement controlled by its nervous system?" (such as: better body control, which ultimately facilitates better reproduction). These more ultimate questions are concerned with the adaptive reason for a biological trait to exist, and ultimately. They come down to reproductive advantage.
Exceptions to this, would occur when selective mechanisms breakdown, such as in small isolated breeding populations. This could result in random genetic drift overwhelming normal selective powers. However, such a result could also provide an answer to a "why?" question. Or it could be considered a "how is this change occurring?" question, avoiding the "why?".

A third, higher order kind of "why?" question deals with "why is there selection acting on populations, for or against different traits?".
Or "why does selection work?". I suppose that this could be rephrased as a "How does selection work?" question, that seems like avoiding thee issue to me.
However, classified, there are satisfactory answers to these kinds of questions, to be found in the processes underlying natural selection.

A population of replicating entities (like organisms) will come, over time, to be numerically dominated by those that do the best job of replicating (reproducing), in their specific environment (that in which they live, interact with, and from which they harvest their required resources).
Variants among the population that are better (or worse) suited, in some way, for their particular environment, will become more (or less) prevalent in their population, over time.
Competition among replicating entities is enhanced when a population of entities, that depends upon the same set of limited environmental resources, has reached the limits of their their environment's carrying capacity.
Organisms using different resources are not in direct competition.

Addy Pross has compared the mechanisms of natural selection with those underlying his Dynamic Kinetic Stability (DKS) view of populations of replicating chemical systems (new field called Systems Chemistry).
He has written a nice little book on this: What is Life?: How Chemistry Becomes Biology.
(There are surprising number of "What is Life?" books around, besides Schrödinger's classic.)
Pross's argument is that when analyzing replicating chemical systems, he finds processes equivalent to those underlying how natural selection acts on replicating biological systems.
The dynamic persistence, within a breeding population, of a group of replicating entities (the individuals in a population or a species) can result in a stable set of traits (a property of the group itself), even though the population's individuals are constantly turning over. Among the traits can be the organisms evolved set of goals, which are often "why" they are doing things.
This contrasts with how normal inanimiate physical entities (like objects).
Their prevalence (continued existence) can be explained by their stable thermodynamic states and their passive thermodynamic interactions with their environment.

This is a basic difference between the subject matter of biology, and that of physics and chemistry.
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  • #2
Great post, Bill. So it sounds like the answer to "Why does life exist" is basically "Because it has evolved to survive" (at least so far). Starting from humble and very simple beginnings, the things that survived to reproduce did so because of mutations and adaptations that helped them to survive through the generations. Mutations and adaptations that did not work well were selected against and declined or disappeared. (Modulo large disturbances like meteor impacts, ice ages, etc.).

It's interesting how the concept of mutations and evolution leading to survival over generations can provide "why" answers that differ from other sciences...

1. Why do living organisms need water?

Water is essential for all living organisms because it helps regulate body temperature, transports nutrients and oxygen, and removes waste products from the body. It also plays a role in many biochemical reactions necessary for life.

2. Why do some animals have fur while others have feathers?

The type of body covering an animal has depends on its evolutionary adaptations to its environment. Animals in colder climates often have thicker fur to keep them warm, while animals in warmer climates may have feathers to help regulate their body temperature.

3. Why do plants need sunlight to survive?

Plants use a process called photosynthesis to convert sunlight into energy. This energy is necessary for the plant to grow, reproduce, and carry out other essential functions. Without sunlight, plants would not be able to produce their own food and would eventually die.

4. Why do some diseases only affect certain species?

Different species have different immune systems and genetic makeups, making them more or less susceptible to certain diseases. Some diseases may also be specific to certain environments or hosts, making them more likely to affect only certain species.

5. Why do some animals hibernate during the winter?

Hibernation is an adaptive behavior that helps animals conserve energy and survive during harsh winter conditions. By lowering their metabolic rate and reducing their activity, hibernating animals can save energy and stay alive until food becomes more plentiful in the spring.

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