Roller

Learned ladies and gentlemen!

How did the first single celled organisms look? Did they consisted of mitochondrion, cytoplasm, Golgi apparatus, endoplasmic reticulum, ribosoms, etc... (.Biological Tutorial)

The reason I'm asking is probably obvious. Creationist often argue how single celled organisms that first appeared had to consist of these organelles and that they are too complex.

Now, I don't know if these oragnelle are part of the modern cells only or the first ones didn't had them so they were fairly more simple.

Also, can someone describe to me in layman terms how did blood clotting evolve? I've found this and this (number 7) but its somewhat complicated for me to understand since I lack sufficient biology education (darn computer science).

I apologize for my English since it's not my primary language so it's hard for me to be more precise in matters that require precision.

(edit: deleted redundant links)

abe smith

Welcome to EyeEye, Person. Your english is obviously perfectly-adequate to communicate your intentions! That's all that matters.
You could go to best local library (probably at your local college/university >>> who will almost certainly give you courtesy borrower's free privilege if you show them your local public library card). There, (at whatever is your largest handiest library) find some books by Lynn Margulies; and or Ernst MAYR; or ask the Reference Librarian at the Ref desk to help you find the answers you seek. Welcome aboard! Good hunting.

lpetrich

There are two main kinds of cell structure in present-day organisms: prokaryotic and eukaryotic.

The prokaryotic kind is represented by bacteria; they have a relatively simple cell structure, without a well-defined cell nucleus. The common ancestor of all existing life most likely looked like one of these.

The eukaryotic kind is the sort with all these structural details (Golgi, ER, etc.), though bacteria also have ribosomes.

Ribosomes are structures for translating from RNA sequences into proteins; they are complexes of RNA molecules and proteins. There has been some research on which is the most essential part of a ribosome, and it turns out to be the RNA. The proteins simply assist the RNA, and some of them look like multiple "inventions".

Clivedurdle

it's Lynn Margulis (ex wife of Carl Sagan)

Quite complex amino acids have been found in space, so assuming life isn't ubiquitous (but it might be!) the building blocks are common in the universe. RNA isn't too much of a struggle given enough time and complexity has continued to evolve.

Margulis argues that cell nucleii are in fact from a seperate bacteria that symbiotically lived inside another bacteria. Margulis argues that symbiosis is very common, and the complexity we see in life is because of this propensity to join up to find solutions.

The other argument for the basic complexity - that life seeded here - only puts the source of the primeval soup off planet.

Can't wait until there are some definitive examples of exobiology - probably Titan.

MrDarwin

No biologist believes that the first living thing resembled even the simplest of bacteria alive today. What did it resemble? Hard to say. Part of the problem is defining "alive", "living", and life" in the first place. Would a simple self-replicating molecule floating naked in a solution of simpler molecules be considered "alive"?

How about a self-replicating molecule, contained within a self-assembling lipid membrane, which reproduces by obtaining simple amino acids and lipids that diffuse in from a surrounding solution (i.e., simple building block molecules that we know can form spontaneously in an inorganic solution with an energy source)?

DNAunion

DNAunion: "RNA isn't too much of a struggle given enough time"? Do you have any papers that discuss prebiotic experiments that have produced RNA from scratch?

Doubting Didymus

Define "scratch".

lpetrich

It must be conceded that prebiotic synthesis of RNA is difficult.

However, RNA itself may not have been the first self-replicating molecule -- something else could have initially taken the place of the riboses of RNA molecules. Perhaps something like amino acids, producing Peptide Nucleic Acids (PNA's).

But even that remains uncertain; the origin of the "RNA world" continues to be a mystery.

Blinn

Early Life - Evolution on the Precambrian Earth

Haven't read it myself yet - I've only taken a cursory look - but I think it's probably exactly what you're looking for.

Nic Tamzek

For the hard-core, I recommend:

Szathmary and Maynard-Smith

Major Transitions in Evolution, 1995 book


...and search PubMed for articles by Cavalier-Smith:

PubMed

...e.g.:

Obcells as proto-organisms: membrane heredity, lithophosphorylation, and the origins of the genetic code, the first cells, and photosynthesis.
J Mol Evol. 2001 Oct-Nov;53(4-5):555-95.

nic