Chapter 4

transcript

Chapter 4

The Origin and Early History of LifeReview info – has already been read as summer

reading.

Objectives: 1. Evolution Activity – Hopefully it will work with just 7 kids 2. Visual Book Page on Types of Selection.3. Complete notes on Origin and Early History of Life.

Due Tmo: 3 pages of review book using evolution notes.Quiz on first 20 vocabulary words.

How Did Life Originate On Earth?

• ?• What do we know?– Earth formed 4.6

billion years ago.– 3.5 bya is the oldest

clear evidence of life (microfossils).

• Needed the correct combination of physical events and chemical processes.

After Earth Formed• Water vapor in atm condensed into liquid

water.• Accumulated in chemical rich O – Ammonia– Formaldahyde– Formic acid– Cyanide– Methane– Hydrogen sulfide– Organic hydrocarbons

Where did life form?

• Did life begin in the Ocean?• On the edge?• At hydrothermal vents?• Elsewhere?

• Complex molecules Life?– movement, sensitivity, death, complexity?– Necessary vs. sufficient

Necessary vs. Sufficient

• Cellular organization?• Sensitivity?• Growth?• Development?• Reproduction?• Regulation?• Homeostasis?• Heredity?• Change for the sake of change?• Change passed to next generation?

No Eyewitnesses to Origin of Life

• Special Creation: Life forms put on E by supernatural or divine forces. Core of most religions – most widely accepted. Biblical account word for word is unscientific.

No Eyewitnesses to Origin of Life• “Panspermia”

Extraterrestrial Origin: Began on another planet and infected E. Meteors and cosmic dust brought complex molecules. Some evidence that early meteorites may have carried organic matter.

No Eyewitnesses to Origin of Life• Spontaneous Origin: Life evolved from inanimate matter as associations

between molecules became more complex. • Most scientists tentatively accept.• As molecule change occurred is allowed to be more stable, persist longer,

associate in complex ways, and may have led to the evolution of cells.

So How Do We Decide?

• Which do scientists go with and why?

No Eyewitnesses for Where• Ocean Edge Origin with Reducing Atmosphere: E history reveals origin probably

occurred at high T.• Molten hot 4.6 bya – 3.8 bya.• As solar system stopped slamming E the T dropped.• 3.8 bya temperature dropped to 120-190 degrees F.• 3.8-3.5 bya life appeared.• Ea atm content… No agreement

– CO2, N2, H2O. Also H2, H2S, NH3, CH4 (methane, ammonia, hydrogen sulfide)• High Hydrogen = reducing atmosphere – allows for Carbon macromolecules. Low O2

though so photosynthesis HAD to come first. Our O2 atm content now is 21%.

• No carbonates found in early E rock. • Also, no O2 = no ozone = organic compounds

broken down by UV rays.

Critic S

No Eyewitnesses for Where

• Under Frozen Ocean?• Like Europa but evidence suggests that Earth

was warm.

• Probably E not frozen.Criti

• Deep In Earth’s Crust?• Volcanic activity with Iron and Nickel sulfide =

chemical catalysts to recombine gasses into blocks of life.

• Recreated and made precursors to amino acids with peptide bonds.

• Chemical concentration used to prove this reaction was higher than was available in ea. E.

Critic S

• Within Clay?• Silicate surface chemically attracts clay

surface.• The positive charge attracts organic molecules

and repels water.

• There’s little evidence that this is even possible.

Critic S

• Deep Sea Vents?• Metal sulfides in vents

react to create prebiotic molecules.

• + sulfides attract – molecules

• Genomics says prokaryotes today most related to bacteria on deep sea vents.

Ice Article

Experiments to Determine How and Where

• Miller/Urey 1953• Attempted to reproduce conditions at O edge under reducing atm.1. Assembled reducing atm w H but no gasseous O.2. Placed over liquid H2O (O edge)3. Kept T below 100 degree C.4. Simulated Lightning (sparks)• Within One week 15% of C present as methane gas CH4.

Converted to compounds CH20 (formaldahyde) and HCN (hydrogen cyanide).

Formic acid (HCOOH) Urea (NH2CONH2) carbon bonds and forms aa glycine and alanine.

• Similar experiments made 30 carbon compounds and 6aa.

Which came first?

• RNA Theory:• Without hereditary molecules no consisten

molecules could have formed.• Ribozymes – are RNA molecules that act like

enzymes to help own assembly… so were proteins needed?

• rRNA acts like Ribozymes.

Which came first?

• Protein Theory:• Simple protein synthesis easier than

nucleotide synthesis.• Nucleic acids (RNA) are too complex to form

spontaneously repeatedly.• Can make synthetic replicating nucleic acids

and some can even mutate.

Which came first?

• Some Kind of Combo?• Peptide-Nucleic Combo Theory• PreRNA (peptide nucleic acid PNA)– Basis for life– Stable and simple enough to form spontaneously

and self replicates.

Spontaneous molecules… ok.Spontaneous compounds… ummm ok.

Cells from these…HOW???

• Cells = little bags of fluid with contents different from the environment.

• Bubble Theories = Hydrophobic region on molecules will form bubbles in water spontaneously.

Oparin’s Bubbles 1930

• Life causing conditions different from todays environment.

• Primary Abiogenesis – for cells to evolve they must dev’l chemical complexity, separating contents from env. With cell membrane and concentrating their contents.

• Protobionts – Ea. Chemical concentrating bubble like structures. Published 1938.– Inspired Miller/Urey to create life.– This allowed Oparin be become more

accepted.

Bubble Theories

• Microspheres, protocells, protobionts, micelles, liposomes, coacervates are all hollow spheres and exhibit cell like properties.

• Differences depend on the structure (protein vs. lipid) and how they form.• Coacervates – are lipid bubbles with two layers. They resembel biological

membranes.• Can form projections and divide by pinching.• Grow by accumulating more lipids.• Contains aa and used for acid/base reactions in decomposition of glucose. • NOT ALIVE!!!

Bubble Scenario• Bubbles in Ocean• Some have aa.• They persist then disperse.• If aa have side groups for growth

promoting rxn surviving longer. • Protenoid microspheres and lipid

coacervates. • Persistence increases with metabolic

rate. • Bubbles better able to incoporate

molecule and energy would persist longer and grow.

• Edge of O frothy with bubbles. UV and ionizing radiation, methane and organic molecules.

Bubbles

• Successful bubbles could make daughter bubbles.

• As soon as they could dev’l heredity life could begin.

Lipid Bubbles Protein Bubbles

Coacervates form readily in water

Heritable mechanism imaginable

How do they get heredity? Don’t form readily in water – forms usually in dry conditions.

Bubbles

• RNA acts like an enzyme to make new RNA so maybe they were first.– Became complex and stable– More so when surrounded by bubbles.

• DNA came later as replacement because replicates and stores more stably since double helix.

Skipping A Step

• Fossil evidence shows progression from simple to complex organisms begins 3.5 bya.

• Ea. Evidence of life in microfossils (1-2 micrometers). Single celled with no external appendage on internal structures.

• Resembles bacteria• Prokaryotes (“before” “kernel” [nucleus]).• Eukaryotes appeared 1.5 bya so 2bya

bacteria only orgs on E.

Archaea

• NOT BACTERIA!!!!!!!!!!!– In Black Sea where there is no O2.– Boiling Hot Springs– Deep Sea vents

• Similar environments to ea E.– Methanogens – methane producing simple anaerobic CO2

+ H2 CH4– Have DNA, membrane, wall, and metabolism with ATP

Archaea vs. BacteriaArchaea Bacteria

No cross link. Carbohydrte peptodiglycan in walls

Peptodiglycan – very strong cell waslls and simple gene architecture

Different Lipid Structures Phospholipids

Major differences in biochemcial process of metabolism

“Regular” biochemical activity. “normal” metabolism.

Methanogens: Methanococcus from deep sea vents survived at 185 degrees F with pressure 245x sealevel.2/3 genes unlike any ever seen.Sequence compared to bacteria indicates split 3bya.

Photosynthetic Cyanobacteria – have chlorophyll pigment and produce O2. Appeared ~3bya and increased E O2 from 4-21% increased ozone to keep proteins/nucleic acids safe.Responsible for limestone deposits.

Extreme Theremophiles: bery hot = hydrothermal volcanic vents and boiling water. 230 degrees F ok. May be relics of first orgs on hot E.Extreme Halophiles: Very salty living env = Dead Sea.

The Three DomainsArchaea Bacteria (Eubacteria) Eukaryotes

Microfossils appear 1.5 byaDifferent from previous.LargerInternal MembraneThicker Walls“true” “nucleus”

Basic TimeLine

4.6 bya E forms

3.5 bya Prokaryotes and Archaea

2.5 bya Chemoautotrophs and Cyanobacteria

1.5 bya 6micrometer Eukaryote largest found

1.4 bya Eukaryotes are larger than 10 micrometer and have small membrane bound structures.

600 mya Eukaryotes are Multicellular organisms

PreCambrien

Cambrien

Archaean

Proterozoic

PhanerozoicSee page 70 in your text.

From Bacteria to Us

• Bacteria have infolding membranes for internal passages.– The Eukaryotic ER may have evolved from this.– The nuclear envelope may have been an extension

o f the ER to protect the nucleus.

• http://www.youtube.com/watch?v=i6efxaviopI evolution is impossible

• http://www.youtube.com/watch?v=dMH0bHeiRNg evolution of dance

• http://www.youtube.com/watch?v=_ksdV9HPwBY evo in 2 minutes

• http://www.khanacademy.org/video/introduction-to-evolution-and-natural-selection?playlist=Biology Evolution explained again.

• http://www.youtube.com/watch?v=mmDAse1DusA&feature=related Awesome endosymbiosis – quick

• http://www.youtube.com/watch?v=SY3MZ_wNFW8 eras

AP Objectives

1. Quiz on first 20 vocabulary words.2. Article on origin of life.3. Review endosymbiosis and how it relates to

eukaryotic evolution regarding the phagocytosis of prokaryotic organisms.

4. Complete chapter 4 notes on origin of life.5. Evolution in a nutshell.

Homework: complete article. Next 20 vocab. words quiz pushed off until Friday.

Lynn Margulis 1970

• Endosymbiotic Theory• Critical stage of evolution of Eukaryotes when

evolutionary relationships with prokaryotes occurred.

• Energy producing bacteria reside in larger bacteria became mitochondria

• Photosynthetic bacteria also became chloroplasts.

Far Out?

Not Really• Evidence:

1. Many symbiotic relationships do occur in nature.2. Mitochondria and chloroplasts have their own

DNA which is similar to bacteria in size and characteristics.

3. Double membrane.

Advantages to being Eukaryotic

• Euk can sexually reproduce – produce offspring with a copy of each chromosome. +genetic recombination +evolution +diversity. Meiosis and sexual reproduction led to diversity.

• MultiCellularity – single Euk cells began living in colonies. Eventually members took on different duties to take on characteristic of one individual. +fosters specialization!

Organize the information on page 72 into one cohesive and easily understandable chart

DiversityDomains: Archaea Eubacteria Eukaryotes

Kingdoms: Archaea Eubacteria Protista Fungi Plantae Animalia

Cell Type: Prokaryote Prokaryote Eukaryote Eukaryote Eukaryote Eukaryote

Cell Number Uni Uni Uni / Multi Multi / Uni Multi – Non Motile

Multi - Motile

Feeding Methanogens Cyanobacteria Photosynthetic / heterotrophic

Hetero Photosyn Hetero

Examples/ addl info

Halophiles, Thermophiles

Nitrogen Fixing… could be pathogenic

Amoeba, paramecium

Outer wall of chitin Mushrooms

Trees, grasses, moss

Sponge, spider, newt, penguin, human

Answer Questions about phylogenic tree. Pg. 72

Extraterrestrials?

• E = C molecules and water to form life.• Under different conditions maybe Si could act

like C and Ammonia like water.

Extraterrestrials?

• Universe has 10^20 stars like our sun.– At least 10% of those have planetary systems.– If ONLY 1/10,000 is the right shape and distance…

Extraterrestrials?

• =10^15 possible E conditions!

Extraterrestrials?

• Life on Mars?• 4.5 byo rock found with microfosslils 20-100

nanometers in length.• Not compelling enough though so not

scientifically accepted.

Europa?

• Seems possible.• There is liquid water under the ice which is

warmed by the push and pull of gravitational attraction.

• Satellite missions were scheduled to keep checking and exploring.

More to Think About

• Archaea found here are most ancient. Sheltered environment.

• Maybe life originated here?

Virus Article

Chapter 4 Assignments that need to be finished:

1. Interior assignments2. 40 question quiz/team creator3. Create-a-book pages (5)4. Pictures to go with important concepts – Assignment given by

instructor5. 2 articles (Ice and Viruses)6. Time Line7. AP Free Response Q.8. Lab on Termites #19. Lab on Termites #210. Vocabulary Flashcards 11. AP Test Flashcards - begun

Chapter 4

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