Learning Targets 15. Recognize that evolution has occurred in all organisms and continues to occur. 17. Identify dates of big events in earth’s 4.6.

Part 7History of Life

Learning Targets

15. Recognize that evolution has occurred in all organisms and continues to occur.

17. Identify dates of big events in earth’s 4.6 billion year history.

18. Describe the basic models for the origin of life and the evidence that supports them.

19. Understand the evidence that RNA was the earliest genetic material.

27. Describe the evidence for the endosymbiotic theory.

History of Earth

4.6 Billion years earth formed

Hot

Constantly hit with chunks of ice and rock

No atmosphere

4 billion years bombardment ended earth cools oceans

Atmosphere forms!

Little to no oxygen

Lots of H2O, Nitrogen, CO2, Methane, Ammonia & Hydrogen

LT 17

History of Earth

Direct fossil evidence of early life on earth microorganisms 3.5 billion years ago

How did THEY get there?

1. Abiotic (nonliving) synthesis of amino acids & nitrogen bases

2. Macromolecules such as protein & nucleic acids

3. Protocells (droplets of nucleic acids & proteins with a membrane to maintain internal environment)

4. Origin of self-replicating molecules

LT 17

History of Earth

Is it possible? 1953 Stanley Miller

Heated water vapor mixed with early atmosphere “lightning” cold water condensed the atmosphere (made it “rain”) collected sample water returns to “sea”

Voila! Organic molecules!!...so yes, it is possible!

http://viewpure.com/mF9U5x6Nxnw

LT 18 & 19

History of Life

How do we get from amino acids to life? 2009 study abiotic synthesis of RNA in test tubes

First genetic material likely was RNA

Supported by important role RNA plays in making proteins (mRNA, tRNA, rRNA)

RNA can also act as an enzyme (ribozyme) --> replication

RNA much more versatile shape & function

LT 19

Big Events

First single-celled organisms

Earliest evidence 3.5 billion years ago Stromatolites

Layered rocks form when prokaryotes bind sediment together

LT 15 & 18

Big Events

2.7-2.4 billion years ago oxygen-releasing Prokaryotes gradually change atmosphere! (oxidation of rocks)

1.8 billion years ago fossils of first eukaryotes Endosymbiosis Theory

Aerobic cells (ex: mitochondria & chloroplasts) began living inside larger cells (either as prey or parasites)

Evidences: inner membrane, own DNA (you inherit mother’s mitochondrial DNA), replication similar to prokaryotes

http://viewpure.com/3ESXvLHceDc

LT 15, 18 & 27

Big Events

1.2 Billion years ago

Multicellular eukaryotes red algae

535-525 million years ago

Cambrian EXPLOSION!!!!

Present day phyla began to appear

Predators (claws & other prey-capturing features appear)

Prey (defensive mechanisms appear sharp spines, heavy body armor)

LT 15 & 17

Big Events

500 Million years ago

Plant and animal begin to colonize land

Plants colonized land with company of fungi…even now, a lot of plants rely on fungi to help absorb nutrients

Animals arthopods among the first (450 mya), tetrapods (365mya)

195,000 years ago humans arrived (lineage diverged from other primates 6-7 mya)

LT 15 & 18

Learning Check

Evolution is

A) only a theory and still needs to be proven

B) an explanation for how life came to be, but no longer happening

C) observed currently, but cannot explain the evidence we see in the history of life

D) observed currently and best explains the evidence we see in the history of life.

Oldest fossils are

A) 3.5 billion years old and are prokaryotes

B) 1.4 billion years old and are prokaryotes

C) 3.5 billion years old and are eukaryotes

D) 1.4 billion years old and are eukaryotes