Of life and limestone

What is life?

No, I'm not talking about religion or philosophy here. 

I'm gonna be more specific. What makes 'life', living? What makes the smallest bacterium to the largest blue whale living? In a nutshell, looking through a biological lens, what does 'life' on Earth as we know it entail?

Some of you might say, 'Hey, all of them respire, move, derive nutrition...' ; Others might say they all metabolise, show some noticeable changes with the progression of time. The ones who were paying attention to their textbooks might say, "They contain the basic elements of carbon, nitrogen, oxygen and hydrogen."

Here's the thing- All of you are right and wrong at the same time. Confused? Perplexed? A tad bit annoyed? Don't worry, things will become clearer as we progress.

There's only 1 rule fellas: Patience is not an island in the Bermuda Triangle ¹.

HELLO fellow Homo sapiens sapiens, and this is the start of another parallel series- On the origins of life on Earth and gradual complexity of life with time. Why? It's because an understanding of basic chemical evolution is needed to get into the heart of DNA. It's also pretty fascinating- we all started out as a bunch of molecules just floating around. As Carl Sagan accurately puts it, 

"We are made of starstuff." ²

So it's a tad bit important to know how that leap, from helium and hydrogen nuclei, to huge multicellular complex lifeforms, took place ³.

Coming back to the topic, what does life entail? 

According to Wikipedia, 

"Life is a characteristic that distinguishes physical entities that have biological processes, such as signalling and self-sustaining processes, from those that do not, either because such functions have ceased (they have died) or because they never had such functions and are classified as inanimate."

At first, you think "Wow that's a mouthful."

But if you examine it closely, you'll realise that it's actually pretty ambiguous. There's no clear cut definition to life. You can't 'define' it. You can give examples, or characteristics, but you can't really point out what life is. Hence, the answers you all gave at the start were all characteristics, not the definition of life itself. If I continue to elaborate, I'll be going around in circles, so these apparently 'simple' questions are not going to be dealt with now. 

Now that that's out of the way, let's get down to the other word in the title: limestone. 

Limestone is the mineral from which you get chalk. It's a kind of sedimentary rock. Which is why it's important in biology. 

Nature has a tasteful method of photography- through fossils. Fossils are the preserved remains of plants and animals whose bodies were buried in sediments, such as sand and mud, under ancient seas, lakes and rivers. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved in amber, hair, petrified wood, oil, coal, and DNA remnants. Since limestone is a part of this sediment, many, many, many, fossils are found in limestone. Before you start aggressively looking at your chalk piece, here's a heads up: a) many of them are microfossils (remnants of microorganisms) so you might not find what you're looking for and b)there's a good chance your chalk is processed, so don't get your hopes too high.

Understandably (and unfortunately), we weren't around at the time of the Cambrian Explosion. Or the Carboniferous. Or at the time of dinosaurs. And since we don't have time machines yet, fossils are our closest connect to figuring out how life looked like millions of years ago. 

Ammonite fossil in limestone

The last thing I would like to clarify before we dive in is geological time. When we're looking at life developing, time moves very differently. Each development or evolutionary hack requires a sufficient amount of time. For a major change to persist and for significant changes to accumulate, it takes atleast one million years. The scale of time we'll be looking at is in million or atleast a couple of thousands of years, so hang onto your seats⁴.

Geological time.

Hopefully that clarifies a bunch of things and I hope you'll stick around for the series! Geological time ROCK-s. I'll see myself out. 

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¹ I tried. 
² One of my favourite quotes ever. It gives me goosebumps every time. 
³ Just to be clear, this series will NOT have a lot of details on Evolution, Speciation, Natural Selection etc. This is purely examining the connection between Earth and the gradual increasing complexity of life with the passage of time. Evolution & Natural Selection gets its own series- it's currently in development ;). 
⁴ I will be examining only major geological periods (albeit briefly!)- ones where (in my opinion) important changes have occurred. 'Cause geological time is wayyy too long and beyond the scope of a blog. 

Also, a very Happy New Year to everyone and hope you have a great 2022!