BIODIVERSITY

Our story so far…

Life appeared early after the earth began to cool.

The earth formed from the condensation of stellar gases

As life evolved, it also altered major aspects of the earth’s surface, particularly

a. lithosphere – new carbon based rocks

b. atmosphere – dramatic alterations of gases – high oxygen, low carbon dioxide, high nitrogen

c. hydrosphere – reduced greenhouse kept the earth cool enough for liquid water

d. biosphere – new material cycles (carbon, oxygen, nitrogen, etc.)

And life equally depends on the continued dynamic geology to add elements and regenerate carbon dioxide for photosynthesis

Biosphere – refers to the reality that the earth’s surface and life have evolved together and influenced each other, it is an complex, integrated and dynamic system

What on earth is life doing here?

Life has had a profound effect on the conditions on earth

Some people think it may have come literally from “out of this world”

Today life exists as a diverse array of organisms, from small single-celled microbes to large multicellularcreatures.

Where do these cells come from?

Where do these cells come from? Other cells.

Cells take in resources from the environment (eat), transform those resources into themselves (grow), and divide into replicate cells (reproduce).

This transformation is achieved by a complex network of interrelated chemical reactions, or “biochemical pathways”, occurring within the cells.

All cells today are derived from previous cells, in an unbroken chain all the way back to …?

One possibility is that the biochemistry of earlier cell ancestors was simpler, and that the earliest ancestors may have been so simple as to not even be considered “alive”. That is, life emerged out of the natural chemistry of the early earth.

How could this unbroken chain of being ever get started?

This is the notion driving much of the current research on the origin of life.

Is this even plausible?

To consider this, we need to review some basic chemistry

http://www.the-reelgillman.com/

AB + CD => AC + BD

Some molecules have a strong tendency to react together – they spontaneously react and release energy – called exergonic reactions

Other reactions won’t run unless energy is added, called endergonic reactions

Most molecules have a degree of stability and won’t interact even if the reaction is spontaneous, unless they reach a critical energy level, called the activation energy.

Chemistry is the study of the interactions among elements and molecules. These interactions are generally formulated in terms of reaction equations

This graph illustrates the idea of activation energy (EA) in an exergonic reaction

The reacting molecules exist at a relatively high energy state, and must be raised still higher before they can react to form the products and release their energy (their final energy state is lower).

AB + CD => AC + BD

Certain substances have been found that promote reactions, increase their rate, but are not transformed by the reaction (are not “used up”). These are called catalysts. Catalysts are crucial for reaction regulation in industrial chemistry.

Catalysts

Catalysts in the form of protein enzymes are essential for biochemical regulation in all living cells. Every step of a biochemical pathway is controlled by a specific enzyme.

Catalysts increase reaction rate by reducing the activation energy, often by physically aligning the reactants.

Some enzymes work by coupling an endergonicreaction with an exergonic reaction, and this is crucial for biosynthesis (making organisms).

Autocatalysts

Of the many catalysts, some have a unique feature – the reaction that they promote actually makes more of that catalyst (as a product). These are called autocatalysts.

e.g., if A + B => AB is autocatalytic, what is the autocatalyst?

Science

In a sense, autocatalysts “eat”, “grow” and “reproduce”

They appear “spontaneously” in the right environment, and can rapidly increase in abundance.

Exponential Growth. In autocatalytic chemistry, we see the population consequences of reproduction, an important feature of life – the capacity for exponential growth.

One begets another, and each of those can then beget another.

One becomes two, two become four, four become eight, etc.

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It is hard to describe the awesome power of exponential growth.

1 x 2 = 21 = 22 x 2 = 22 = 44 x 2 = 2 x 2 x 2 = 23 = 88 x 2 = 24 = 1616 x 2 = 25 = 3232 x 2 = 26 = 6464 x 2 = 27 = 128 128 x 2 = 28 = 256 256 x 2 = 29 = 512512 x 2 = 210 = 1024

1024 x 2 = 211 = 20482048 x 2 = 212 = 40964096 x 2 = 213 = 81928192 x 2 = 214 = 16,38416,384 x 2 = 215 = 32,768216 = 65,536217 = 131,072218 = 262,144219 = 524,288220 = 1,048,576230 = 1,073,741,824

50 folds get you to the sun60 the diameter of the solar system100 the width of the known universe

Think of folding a piece of paper over and over. It keeps doubling with every fold.

If the paper is .1mm thick,

after 30 folds how thick is it? (107km)

After 40 folds? (109,951 km)1/3 to the moon

FIRE is another process with similar kind of expansive power. Actually, fire is not really exponential since it is space limited

It has that same start slow, imperceptible increase, explosive growth pattern characteristic of exponential growth.

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Fig. 9-13/10-14

Exponential growth is a kind of positive feedback

Nuclear fission is another example

Add: nuclear fusion in the sun

With exponential potential, it is clear how an autocatalyst can transform a system – from a small start it can become a dominating component.

Autocatalysts often emerge in complex chemical systems, they might even be thought of as “inevitable”. The early earth was certainly chemically complex.

Are they “alive”? Certainly not.

Can they evolve? Certainly.

It is easy to imagine changes in the early autocatalysts as

1. More efficient types replaced less efficient types (“competition”)

2. Autocatalysts themselves became substrate for still other, newer autocatalysts, a chemical “predator-prey” interaction, chemical “food webs”

3. Use of new substrates would be favored including light for energy

These changes would reflect a simple kind of “evolution by natural selection” – those types that most efficiently transform reactants will increase to the highest frequency and exclude other competing autocatalysts.

The details of this evolution, even if true,are still unknown (a research goal)

Natural selection can be considered a chemical, rather than strictly biological process, and probably broader than that.

The value of this perspective is that it provides a plausible framework by which chemical evolution could have, fairly quickly and naturally, produced increasingly complex self-replicating organisms

Conditions on early earth (one version):Energy – Solar (high UV), lightning, geothermalAtmosphere – Water, CO2, ammonia, methane,

hydrogen sulfideEarly earth had many sources of energy, and likely even complex, energy rich organic molecules. Experiments recreating these early conditions spontaneously produce many chemical constituents of life (e.g. lipids, amino acids)

Early forms of life may have used these “abiotically” generated molecules as “fuel” for biosynthesis, as well as for materials

Major biochemical pathways and processes in life today

Photosynthesis – light energy stored in sugar

CO2 + H2O + light = sugar + O2

Respiration– energy in sugar used for metabolism

Sugar + O2 = Energy + CO2 + H2O

Each is a complex chemical pathway requiring multiple enzymes

Eventually, early life began to use sunlight as an energy source to build organic molecules that would provide this molecular energy - photosynthesis

http://www.expasy.org/cgi-bin/show_thumbnails.pl

Each is a complex chemical pathway requiring multiple enzymes

Gene Expression - protein (enzyme) production system

- DNA stores information- copied to RNA

- RNA builds the protein

All of these complex pathways are wonderful and crucial, but NONE of them are, by themselves, autocatalytic

In fact, they all depend on each other

Where do these enzymes come from?

Only the cell or whole organism can truly be considered fully autocatalytic

Energy & Materials

BiosynthesisGrowth & Reproduction

photosynthesis respiration

protein production

It is plausible that natural selection in early autocatalytic chemical systems ultimately produced CELLS with

- selective uptake of substrate

- ability to replicate as a unit

eventually

Prokaryotic cells (w/o nucleus)

Eukaryotic cells (w/ nucleus)

Finally, multicellular organisms

Still fundamentally a chemical process – biology is incomprehensible without study of this chemistry

In a sense, organisms exist to serve their biochemistry

Evidence supports an early origin for life

- Earliest rocks about 3.8 BYA- Earliest fossil bacteria 3.5 BYA

Stromatolites – fossilized bacterial mats

Including fossilized bacteria similar to extant photosynthesizers

BYA – Billion Years Ago

Early photosynthesis did not generate oxygen, but by

2.7 BYA, Oxygen generating photosynthesis has caused increasing oxygen in the atmosphere – iron oxide forms in rocks.

2 BYA, Oxygen up to 10% of current level

The Biosphere has a history

Relatively soon after the surface cooled, fossils similar to current bacterial organisms appear, including photosynthesizers.

The atmosphere begins to change – O2 up, CO2 down

Life evolves, and the biosphere changes more – our history is one of continuous interactionbetween the earth and life.

End Evolution Part 1