BIOMI 2900 Lecture 31

Ongoing hydrothermal activities within Enceladus

Direct evidence available from rocks, minerals, and fossils

Inference from experimentation and comparative biology

Speculations on the Origin of Life: The Big Bang ~13.8 bya • Solar System & Earth forms ~4.6 bya • Early Earth is ____, ______, and ______

anoxic, boiling hot, and sterile

Earth lacks an ozone layer so____ sterilizes Earth’s surface

UV light

As Earth cools water vapor becomes ____, O isotopic ratios in ancient zircon minerals indicate oceans are present ~4.3 bya

liquid

Early Earth was anoxic, hence, the minerals on the early Earth were all?

reduced

Oceans full of what two things?

reduced iron (Fe2+) and H2S

Very little organic ____• Most N is in the form of ___

carbon ; N2

The first cells would have been _____that used ___ and ____

chemolithoautotrophs; H2 and CO2

Who or what is LUCA? a) The last universal common ancestor of cellular life b) The little unicellular creatures awakening c) Life’s ultimate creative assembly d) The legendary unseen cellular archetype e) Dr. Luca Brasi, the godfather of the field of life’s origins

a) The last universal common ancestor of cellular life

From volcanism

Prebiotic Chemistry: In the presence of awaruite (a nickel-iron mineral) at vents, H2 + CO2 react to form organics such as ?

acetate that form the building blocks for life

The presence of awaruite (a nickel-iron mineral) at vents, H2 + CO2 react to form organics such as acetate that form the building blocks for life: These reactions form what pathway?

reductive acetyl-CoA pathway (CO dehydrogenasae requires Ni) which was used by first cells

Speculations on the Origin of Life

What is LUCA?

The Last Universal Common Ancestor of all cellular life

Acetogens: 4H2 + 2CO2 → acetate + 4 H2O

Common within the tree of life. Is it aerobic or anaerobic? What pathway does it use?

1. Anaerobic

2. Reductive acetyl CoA pathway

Acetogens: 4H2 + 2CO2 → acetate + 4 H2O

Can be ___ or ___

Can use either what or what?

1. fermentative or respiratory

2. H2 + CO2 or organics

Speculations on the Origin of Life

A Brief History of Life on Earth

E accetpor vs E donor

Anoxygenic Phototrophs: Found in at least?

6 bacterial Phyla

A Brief History of Life on Earth: Earilest Stromaolites

O-isotopes in ancient rocks indicate what prior to 2.5 bya?

O2 production

Oxygenic Photosynthesis:

Cyanobactieria: H2O + CO2 → O2 + CH2O

creates ~25% OF Earth’s?

current productivity

Cyanobactieria is a major souce of?

Ancestor of?

O2

Chloroplasts

A Brief History of Life on Earth: Great oxidation event

Iron Oxidizing Bacteria 4Fe2+ + O2 + 4H+ → 4Fe3+ + 2H2O

Early Multicellular Eukaryotes & Ozone Shield Forming

Origin of Eukarya: Eukarya are a genetic chimera derived from Archaea & Bacteria.

DNA replication, Transcription, and Translation related to?

Archaea

Eukarya: Fatty acid lipids related to?

Bacteria

Eukarya: Central metabolism more closely related to ?

bacteria

Eukarya: What are two things derived from bacteria?

mitochondria & cholorplasts

The Endosymbiotic Origin of Mitochondria & Chloroplasts: Endosymbiosis theory: Chloroplasts and mitochondria are derived from ancient prokaryotic cells that were?

engulfed by the ancestors of modern eukaryotic cells (i.e. endosymbiosis)

Prokaryotic cell structure vs Eukaryotic cell structure

Evidence for Endosymbiosis Theory: Mitochondria and chloroplasts contain?

DNA → is circular & bacterial

• ~17kbp (~37 genes) and 120-190kbp (~110 genes) respectively

Evidence for Endosymbiosis Theory: What type of genes derived from bacteria?

Eukaryotic nuclei contain

Evidence for Endosymbiosis Theory: Have what type of lipids? Have their own ___ and ____

bacterial

ribosomes; rRNA

Chloroplast rRNA is derived from ____

Mitochondria rRNA is derived from ______

Cyanobacteria

Alphaproteobacteria

Evidence for Endosymbiosis Theory: Replicate within the?

cytoplasm

O2 at Current Levels, Cambrian Explosion