astr 380 the dawn of life on earth - umd

ASTR 380

The Dawn of Life on Earth

ASTR 380Survey results and your comments

1. The class is interesting so far. 7-92. The material is presented at the right level. 8-10 3. The lecture presentation style works for me. 7-10 4. I am following the material and concepts. 8-10

Top 4 suggestion/comments

A. Go a little slower with the slidesB. Ask more questions of “us” and more discussionC. Make the lecture presentations availableD. Make time for a review before the exams

ASTR 380Response

1. Will give you more time to write….

2. Class website is now available and will beimproving during the semester.http://www.astro.umd.edu/~lgm/ASTR380

3. Lecture material will be posted on the websitewithin a week after the lecture.

4. I will encourage more class discussion.

5. The second ½ of the class before the mid-termwill be devoted to review for the exam.

http://www.astro.umd.edu/~lgm/ASTR380

The Dawn of Life on Earth The Earth today – abundant lifeFossil History – the evolution to todayTree of LifeLessons from history and evolution

The Earth Today – Abundant life Broad characteristics of life today:

present in nearly every environment on Earthwide variety of speciessingle cell and multi-cell organismsbacteriaviruses

The human body has 210 distinct cell types

Virus: RNA but no DNA

Bacteria: no nucleus

Amoeba: 1 to many nuclei

The Earth Today – Abundant life

Virus

There are three types of life at the lowest level:prokaryote, eukaryote, and virus

The Earth Today – Abundant life Prokaryote and Eukaryote life is divided into six kingdoms.

The Earth Today – Abundant life

Eubacteria – commonbacteria that we encounter every day.

Cause disease in us.

The Earth Today – Abundant life Eubacteria

The Earth Today – Abundant life Archaebacteria – bacteria mostly foundIn extreme environments:

hot smokersthermal pondsextremely salty waterextreme acid conditions

The Earth Today – Abundant life Archaebacteria – Extremes

The Earth Today – Abundant life Protista:

Protozoa – animal-like, mostly single cellAlgae – plant-lifeFungus-like

The Earth Today – Abundant life Fungi:

The Earth Today – Abundant life Plantae: nearly 300,000 speciesmulticellular organism that produces food through photosynthesis.

The Earth Today – Abundant life Plantae:

The Earth Today – Abundant life Animalia: mobile, multicellorganisms which feed by eating other living things.

The Earth Today – Abundant life Animalia:

The Earth Today – Abundant life Virus: consisting of DNA or RNA with a protective protein coating which can only reproduce by infecting a cell.

Avian flu virus

The Earth Today – Abundant life Viruses may be:

the retro-evolution of small cells that became dependent on other cells for reproduction

Orremnants from the earliest evolution of life.

Biology argue whether or not viruses are living organisms.

The Earth Today – Abundant life There are many underlying common themes in

life today:

All life based on carbon chemistry20 amino acids common to almost all lifeDNA and RNA is the genetic materialCommon use of one “handed-ness” of

sugars and proteinsAll life is compatible at some level:

it can eat, infect, be in contact

Simple interpretation: All life arose from a single common ancestor.

Alternative: ??

2 billion years ago

The Fossil History Evolution to Today

Earth’s Timeline:born – 4.57 B yrs agooldest rock grains – 4.4 B yrsoldest rocks – 4 B yrs agoMoon impact – 3.9 B yrs agoEnd of bombardment – 3.8 B

Events in the first 700 to 800Million years ago routinely sterilized the Earth surface

The Fossil History – Evolution to Today

2 billion years ago


2 billion years ago

This carbon ball in a cavity in a 3.8 Billion year oldrock may be the oldest fossil evidence for life.

If this is correct, this is perhapsan early cell which is unlikelyto be the starting point….

Seems likely that “life” startedwith self-replicating moleculesthat utilized naturallyoccurring pre-biotic molecules.

The Fossil History – Evolution to Today Stromatolites are rock formations formed by colonies ofCyanobacteria. The earliest examples date from 3.5 B yrs ago.

Close relatives still exist todaySingle cell, no nucleus, photosynthetic

2 billion years ago

The Fossil History – Evolution to Today Banded rocks such as these have iron oxide which couldonly occur if there was free oxygen in the atmosphere and oceans at the time that the sediments were made.

Example rock estimatedAt 2 billion years old.

The Fossil History – Evolution to Today 1.5 Billions years ago, Sex was invented.

This allowed two cells to create a totally new individual.

The Tree of Life

Lessons from History and Evolution It likely took around:

100 Million years for the first life to develop after the end of global sterlizing events.

200-400 Million years for cells capable of photosynthesis todevelop

2 Billion years for free oxygen to become dominant in theatmosphere

3.5 to 4 Billion years for the first multi-cellular life to form.

Then from 4 Billion years onward life exploded to exploitevery opportunity.

Lessons from History and Evolution Implication:

Life at the simplest level is easy and quick.

Full-up mobile, intelligent life is tough.

Speculation:Photosynthesis was the key to the development ofcurrent Earth life.

harnessed the energy of the Suncreated an Oxygen atmospherecreated an organic and energy rich

environment to support multi-cell life.

astr 380 the dawn of life on earth - umd

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