Homework #4 - Peppy the Proton (Part 3)

due Monday August 12

In our last episode, we left Peppy floating around in Earth's early atmosphere as part of a carbon nucleus in a CO₂ molecule...

Fortunately for Peppy, her CO₂ molecule dissolved from the sky into the primordial ocean before the meteorites that fell during the period of Late Heavy Bombardment could blast her back into space. She gradually made it to the ocean floor where she was incorporated into sedimentary rock. After a few hundred million years, Peppy & company where spewed back into the atmosphere via outgassing from cracks in the Earth's crust. But now strange things were going on... Peppy found herself "hooking up" with even more protons and their associated neutrons and electrons, and together they began to form new molecules that seemed to have amazing abilities. Peppy was becoming organic.

1. Describe a method for synthesizing complex organic compounds (long chains="polymers") from the components of the early Earth. Some of the things you should discuss include:
   • the properties the atmosphere would have had to have had or not had (I do not want to hear anymore that German is complicated)
   • where the energy would have come from (2 possible sources)
   • where on Earth each step might have occurred, i.e., the atmosphere, open ocean, under rocks
   • what these organic compounds were
   • etc.

Still more exciting things were happening. Peppy's molecule was hanging out with other new-fangled molecules and together they were doing things that no other bunch of molecules had ever done before (at least none that she'd ever met). She and her friends were part of something new - a living creature!

2. What characteristics would you expect a "collection of matter" to have in order to consider it to be life? (There isn't necessarily one right answer to this question, but keep in mind that these characteristics must be qualities that all living things possess and that non-living things do not possess.)

Peppy's carbon atom had become part of a bacterium. One day, the bacterium was engulfed by a much larger cell but instead of being digested, the smaller cell remained happily within the larger one, providing energy and getting food and protection in return.

3. For the first 2 billion years or more of the history of life on Earth, the only organisms were prokaryotes (bacteria). Why was the appearance of eukaryotes (more complex cells) such an important step for life, and why didn't they appear earlier?

Another several 100 million years went without too much excitement, when suddenly the pace picked up. Peppy was being moved and shuffled back and forth among simple cells, complex cells, and still newer things - multicelled creatures. Changes were happening quickly now - life was diversifying. This was the Cambrian Explosion.

4. What is the process that has produced all the different kinds of creatures on Earth, and how does that process work?

Several 100 million years later...
Peppy had become part of one of the largest creatures that had ever lived on Earth - a dinosaur. But suddenly a huge chunk of rock hurtled from space and slammed into the ground, vaporizing everything within 100's of miles. (Peppy thought this kind of thing had ended a couple billion years ago). Peppy's dinosaur died, along with all the other dinosaurs and many other creatures. But life diversified again, this time in different ways. The little furry rodent-creatures that used to scurry away and hide when Peppy-the-dinosaur came by were now giving rise to larger, smarter, and very adaptable animals.

After 65 million years Peppy's carbon atom was incorporated into a neuron in the brain of an upright hairless ape - a human.

4. About how long ago did our subspecies (Homo sapiens sapiens) "appear"? For how long have we been capable of communication with beings outside of our planet? About what percentage of the Earth's history is this?

Peppy's human is a curious character (apes tend to be) and wonders often about things that none of her bacteria, or paramecia, or dinosaurs had ever considered - "Are we alone in the Universe?" Peppy's human wonders so hard that she decides to send a message into space, hoping to contact others like herself...

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