Do Now 5.3

Do Now 5.3Objectives:

1.Complete objectives 2 & 3 from yesterday

Task (Answer, don’t copy):

1.The first life forms required some kind of cell membranes, some kind of replicating molecule, and some kind of structural materials. Which

types of macromolecules do these three tasks in living things, and what are those macromolecules

built from?

What Science Is and Isn’t

• Get to your groups… you have 4 minutes to prepare your thoughts for the 2-minute presentations.– What is your article / articles about?– How does it relate to scientific investigation?

1. If you were to make a timeline showing the major events in the history of Earth, what are the top 3 things you

would include?

2: Copy timeline on board on back of notes

A Brief History of Earth

The History of Earth in 12 steps• Required knowledge:

– Order (not dates) of 12 events (except below)– What happened for each event– Relative orders of time

• BYA vs MYA

• Eons of Geological Time– Precambrian (formation of Earth 4.5 BYA to Cambrian

Explosion 543 MYA)– Paleozoic (Cambrian Explosion to Permian Extinction 250

MYA)– Mesozoic (Permian Extinction to K-T Extinction 65 MYA)– Cenozoic (65 MYA to present)

The Big Bang 13.7 BYA• The beginning of matter, energy, and time. box

1.

Best Evidence For BBT• Expanding Universe (comological redshifting)

• Cosmic Microwave Background Radiation

Formation of Sol, our Sun: 4.6 BYA• The light and heat it

produces are a result of nuclear fusion. This occurs because of the massive gravity of such a large object. Box 2

Formation of Earth And Moon: 4.5 BYA

Rocks, dust, and meteorites were pulled together by gravity to form Earth. The moon was formed by a massive collision during this period also. Box 3

The oldest rocks scientists have ever found are about 4.0 billion years old, but we think Earth was around even before that. Why aren’t there any rocks left from 4.5 to 4.0 billion years ago?

Here’s the Plan

• The Precambrian Eon begins with the formation of the solar system about 4,500 MYA (= 4.5 BYA).

• The Pre-Cambrian is incomprehensibly long: it is 86% of Earth’s history. – Rocks form: 4,000 MYA– Abiogenesis (life “evolves”): 3,800 MYA– Eukaryotes evolve (endosymbiosis): 2,700 MYA

• The Precambrian Eon lasts until 543 MYA, with an event commonly called the Cambrian Explosion

Pre-Cambrian Earth

The Origin of Life on Earth:Abiogenesis

Evidence for a Common Origin

• DNA and RNA are the 'universal' basis for all life on Earth: all cells use RNA to make proteins.

• Only 20 amino acids are used in all living things on Earth. L-amino acids exclusively are used in all living things on Earth.

• ATP is the 'universal' energy used in all living cells.

• Fermentation (glycolysis) is the first step in ALL metabolism.

• The genetic code is almost identical in organisms as different as bacteria and humans

So when did it happen?Carbon dating techniques show that the oldest fossils are about 3.8 BILLION years old.

The oldest fossils are very similar in structure to these stromatolites - rock-like buildups of microbial communities.

The First Organic Compounds

• Complex organic molecules are common in the universe.

• Amino acids (the building blocks of protein) can be found on comets and other moons and planets. They can even be made in the lab.

• How organic chemicals came together to form the first cells is still under debate, but there are strong hypotheses with supporting experimental evidence.

Facts• FACT: Organic

chemicals like amino acids and proteins form cell-like spheres called microspheres and coacervates spontaneously

• FACT: RNA molecules called ribozymes can act like enzymes and catalyze reactions.

The First Cells – Archaea (prokaryotes)

Hypotheses• Many scientists believe all life

originated from an RNA molecule that had a special property – it could catalyze its own replication.

• UPDATE 2009 – SELF-REPLICATING RNA MOLECULES PRODUCED IN THE LAB!!!!

• Although the details are debatable, when ribozymes got into a protective fatty acid membrane, the first proto-cells arose

+

Self-Replicating Ribozymes

Coacervates & Microspheres

RNA based proto-cells

Video, anyone?...

The First Cells 3.8 BYA = Box 4

• The very first cells were heterotrophs, and soon used up all of the organic chemicals around them.

• The only way life could continue is if cells started to make their own chemical “food.”

Most Similar to The First

Life:

Archaea, a group of

prokaryotes

Endosymbiosis: origin of Eukaryotes 2.7 BYA Box 5

• Prokaryotes are the only life on Earth for over a billion years.

• By the end of the Precambrian Eon, some simple animals (sponges, flatworms, roundworms, cnidarians) had evolved.

• A mass extinction occurs (Vendian) 543 MYA, officially ending the Precambrian Eon

Later Pre-Cambrian Life

• The Cambrian Explosion (or Cambrian diversification; 540 MYA) was a brief period in history where many new types of organisms evolve:– Arthropods– Chordates– Hard-Shelled animals

• No major animal phyla have evolved since the Cambrian Explosion… why?

Cambrian Explosion (6th box) 540 MYA

Cambrian Life

• Cambrian refers to the first geological period within the larger Paleozoic Eon.

The “Cambrian” and “Paleozoic”

• Land Plants and Fishes Evolve: 480 MYA

• Reptiles Evolve: 350 MYA

• These are boxes 7 and 8…

Later in the Paleozoic

• “The mother of all extinctions.”

• Somewhere between 70 and 95% of all organisms become extinct 250 MYA.

• Worst mass extinction ever recorded on Earth. Competing hypotheses over cause.

End of the Paleozoic: the Permian Extinction

(Box 9)

Dinosaur and Mammal Ancestors survive the “Great Dying”

• Dinosaurs and Mammals Evolve: 220 MYA ( add after box 9)

Mesozoic Eon = “Age of the Dinosaurs” 248 – 65 MYA

Triassic

JurassicCretaceous

• Birds evolve 150 MYA (Box 10)

Birds – Branch of the Dino Family Tree

• You are living in the Cenozoic Eon, the “Age of Mammals.”

• Begins with the K-T extinction 65 million years ago (meteorite that wiped out the dinosaurs) Box 9

• Box 11: Humans diverge from ape populations 6 MYA.

Cenozoic Eon: 64 MYA to Today

Homo sapiens Box 12

• About 200,000 years ago, the first members of our species evolve, from other archaic Homo species (H. erectus)

• By 50,000 years ago, humans are culturally and intellectually modern (i.e. cave paintings

Top 121. Big Bang 13.7 BYA

2. Formation of Earth & Moon 4.5 BYA

3. First Cells 3.8 BYA

4. Endosymbiosis 2.7 BYA

5. Cambrian Explosion 543 MYA

6. Land Plants & Fishes 480 MYA

7. Reptiles 350 MYA

8. Permian Extinction 250 MYA Largest mass extinction in Earth’s history (Dinos & Mammals 220 MYA)

9. Birds 150 MYA

10. K-T Extinction 65 MYA (asteroid kills dinos)

11. Hominids diverge from apes 6 MYA

12. Homo sapiens evolve 0.2 MYA