evolution fyos lecture 4. c and h 2 o for alien life!

Evolution FYOSLecture 4

C and H2O for alien life!

CH2O

Common characteristics of Life

Biologists have identified at least six key features that appear to be shared by nearly all of living organisms on Earth.

o Order

o Reproduction

o Growth and Development

o Energy Utilization

o Response

o Evolutionary Adaptation

Characteristics of Life

Biologists have identified at least six key features that appear to be shared by nearly all of living organisms on Earth.

Order : all living organisms exhibit order in their internal structure.

molecules in living cells are not scattered randomly but instead arranged in specific patterns to make cell structures.

• Order

• Reproduction

• Growth and Development

• Energy Utilization

• Response

• Evolutionary Adaptation

Characteristics of Life

Biologists have identified at least six key features that appear to be shared by most or all of living organisms on Earth.

Order : all living organisms exhibit order in their internal structure.

However, snow flakes, for example, show remarkable structures also.

But, snow flakes are not alive!

• Order

• Reproduction

• Growth and Development

• Energy Utilization

• Response

• Evolutionary Adaptation

Characteristics of Life

Biologists have identified at least six key features that appear to be shared by most or all of living organisms on Earth.

Order : all living organisms exhibit order in their internal structure.

How about galaxies?

Are they alive?

Therefore, “order” is not sufficient condition for life. But, it is a necessary condition.

• Order

• Reproduction

• Growth and Development

• Energy Utilization

• Response

• Evolutionary Adaptation

Characteristics of Life

Reproduction: Organisms reproduce their own kind

A single-celled organism (an amoeba) copying its genetic material (DNA) and dividing into two

genetically identical cells.

Mule, Tigon, Liger, Computer virus?

Again, necessary condition, not sufficient!

• Order

• Reproduction

• Growth and Development

• Energy Utilization

• Response

• Evolutionary Adaptation

Characteristics of Life

• Growth and Development : Living organisms grow and develop in patterns determined at least by heredity

Growing embryos of Costa Rican frog

Heredity : passing on characteristics from one generation to next

Wild fires, crystal?

Again, necessary condition, not sufficient!

• Order

• Reproduction

• Growth and Development

• Energy Utilization

• Response

• Evolutionary Adaptation

Characteristics of Life

• Energy Utilization: Living organisms use energy to fuel their activities

Tube worms near a deep sea volcanic vent.

Car?

Again, necessary condition, not sufficient!

• Order

• Reproduction

• Growth and Development

• Energy Utilization

• Response

• Evolutionary Adaptation

Characteristics of Life

• Response: Living organisms actively responds to changes in its surroundings

A blacktail jackrabbit’s ears flush with blood, the blood automatically adjusted to maintain a constant internal temperature

Mercury in a thermometer?

Again, necessary condition, not sufficient!

• Order

• Reproduction

• Growth and Development

• Energy Utilization

• Response

• Evolutionary Adaptation

Characteristics of Life

• Evolutionary Adaptation: Life evolves in a way to become adapted to its surrounding

white-tail ptarmigan

Camo-moth

counter example?

• Order

• Reproduction

• Growth and Development

• Energy Utilization

• Response

• Evolutionary Adaptation

Evolutionary Adaptation

2 undeniable facts an inescapable conclusion

Heritable traits that enhance survival and reproduction will become progressively more

common in succeeding generations!

• Charles Darwin (1858)

An imaginary population of beetles of mixed color evolves into dark beetles.

DNA is the backbone of the Evolution!

Replicating the whole ~3 billion bases for human DNA takes only a few hours

About 1 wrong coupling in every ~1 billion bases!

Sickle-cell disease

• Just one base change in one gene (Adenine Thymine)

• Most mutations are harmful, but occasional good mutations are being picked up by “natural selection”

Mutation• About 1 replication error in billion chanceso wrong baseo deleted baseo extra base o etc.

• Most of these errors have no effectWhy? about 95% of human DNA bases are “non-

coding DNA”Most significant change is from “deleted base”.

• Due to this “error”, every individual living organism differ each other.

• Mutation = molecular engine of the evolutionary adaption!

• Any change in the base sequence of DNA

How did all these start in the beginning?

Organic Building Blocks

Miller-Urey ExperimentExperiment to create amino acids

(1953)

methane

hydrogen

water

ammonia

the first experiment to test the theory about the evolution of prebiotic chemicals and the origin of life on Earth.

How did the DNA world get started?

• Human DNA contains about 12 billion molecules• even a primitive virus has about 1 million molecules• many viruses use RNA instead of DNA as their genetic material

DNA from the start?

• Typical RNAs have 20-30 nucleotides…• Some RNAs are known to be self-replicable• RNAs are sufficiently simple so that several types of them could have been

created by “Miller-Urey”-type reactions.• These RNAs were exposed to the natural selection

Pre-cells

• Molecular evolution would have been much more efficient if RNA and other molecules are confined in a structure.o Increasing the rate of reactiono Isolating its content to facilitate natural selection among RNA molecules! If no such enclosure, enzyme created by the best RNA can help other RNAs.

Left: microscopic spheres made by cooling a warm solution of amino acidsRight : microscopic membranes made from lipids mixed with water (instantaneously formed!)

RNA cell?

Lipid pre-cell can form on the surface of clay!

+Very high chance of

making RNA on the surface of clay with membrane!!

• Right: lab experiment shows RNA strands (red) entrapped within a lipid pre-cell (green circle) made on the surface of clay!

Chemistry on the early Earth

6 Presentations on Feb 15

• Convergent evolutiono R. Shresthao J. Hedley

• Human Evolutiono E. Clendeningo A. Breeden

• Panspermiao Z. Rindiko C. Starlcup