cellular organization response to stimulus reproduction regulation/metabolism homeostasis heredity...
TRANSCRIPT
The Origin and Early History of Life
•Cellular organization•Response to stimulus•Reproduction•Regulation/metabolism
•Homeostasis•Heredity•Growth and development
Fundamental Properties of Life-Remember These?
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Biogenesis vs. Spontaneous Generation
Spontaneous Generation = principle that a living organism can arise from non-living material
Biogenesis = principle that a living organism can arise only from other living organisms
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Disproving Spontaneous Generation: Experiments
1.) Francesco Redi (1627-1697)-physician & naturalist Fresh meat in a jar w/ no cover =
MAGGOTS! Fresh meat in a jar w/ cover = no
maggots Conclusion: maggots came from flies
that were able to get to the meat, NOT DIRECTLY FROM THE MEAT!
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Disproving Spontaneous Generation: Experiments
( Francesco Redi Experiment Continued)
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Disproving Spontaneous Generation: Experiments
2.) John Needham (1713-1781) – biologist and priest Warmed up gravy and sealed it =
microorganisms grew!▪ What happened?!▪ He thought = a higher being caused
spontaneous generation to occur▪ Future scientists found = Needham did not
boil his sample and didn’t kill the microorganisms
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Disproving Spontaneous Generation: Experiments
3.) Lazzaro Spallanzani (1729-1799)-naturalist & priest
Boiled decaying matter & sealed it = no microorganisms
Why boil? Kill any microorganisms present
Conclusion: life does not spontaneously form from decaying matter
Critics claimed that microorganisms could not breathe because of lack of oxygen.
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Disproving Spontaneous Generation: Experiments (Lazzaro Spallanzani Experiment Continued)
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Disproving Spontaneous Generation: Experiments
4.) Louis Pasteur (1822-1895)-microbiologist
Boiled meat with broth in a flask Allowed air in, but no
microorganisms = no life Allowed air & microorganisms in =
LIFE! Conclusion: life must be present for
new life to form
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Disproving Spontaneous Generation: Experiments (Louis Pasture Experiment Continued)
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Early Earth
Evidence that the Earth formed 4.6 billion yrs ago Many meteorites Original conditions could not support life as we know
it. Early atmosphere contained lots of molecules but was void
of oxygen gas ▪ Evidence of no free oxygen: no iron oxide (rust) in oldest rocks▪ Molecules of Early Earth: H2O (water), H2 (hydrogen gas), CO2
(carbon dioxide), CO (carbon monoxide), N2 (nitrogen gas), CH4 (methane), NH3 (ammonia)
No free O, O2, or O3 (ozone)!
Intense UV radiation due to lack of O3 = no ozone layer Violent thunderstorms Frequent volcanic eruptions
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Before Life
Scientists believe life on Earth is a product of itself
Elements combined to form many molecules, including complex organic ones = MACROMOLECULES! (RNA, DNA, proteins, carbohydrates, and lipids) Ribozymes – self-replicating RNA (has
enzymatic properties but is a nucleic acid)
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Miller- Urey Experiment Miller-Urey Experiment
- Stanley Miller & Harold Urey, 1950s
attempted to reproduce early reducing atmosphere and produce organic compounds from inorganic materials
Built a contraption simulating the early Earth (methane, ammonia, water, hydrogen, lightning, heat, etc)
After 1 week = amino acids, sugars, lipids & other organic molecules
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Miller-Urey Experiment
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Water
Aldehydes
Proprionic acid
Lacticacid Glycolic
acid
Succinicacid
Glycine
Alanine b-Alanine
b-Aminobutyric acid a-Aminobutyric acidN-Methylalanine
Valine
Proline
Aspartic acid
Glutamic acid
Rawmaterials
First group ofintermediate products
Second group ofintermediate products
Examples of final products(isomers are boxed)
Immunoacetic propionic acid
Iminodiacetic acid
Norvaline Isovaline
Sarcosine
Acetic acid
Formic acid
N-Methylurea
Urea
Energy Energy
Hydrogencyanide
Nitrogen
Ammonia
Carbondioxide
Carbonmonoxide
Methane
Hydrogengas
Energy
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First Life On Earth
Around 3.8 BYA, the earliest, simplest forms of life are thought to have been formed
Cells with few organelles (prokaryotic cells) did not use oxygen to live= this is called fermentation. They are anaerobic organisms …
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Anaerobic vs Aerobic Respiration All Respiration: used to release energy from
the food we consume What do we use that energy for?
Anaerobic Organisms can release energy without oxygen Produces a small amount of energy = inefficient Like the first Prokaryotes (simple cells, few
organelles)- Did NOT use oxygen for respiration Aerobic organisms are able to release energy
with oxygen Produces a large amount of energy = very efficient Eukaryotes (complex cells, with lots of organelles) ▪ Ex: Mitochondira, Chloroplast, etc.
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From Prokaryotes to Eukaryotes
Environmental factors caused changes/mutations in DNA allowing some cells to use the sun to make their own food= Autotroph. (Similar to the organelle…?) Photosynthesis = takes out carbon dioxide and
creates oxygen in the atmosphere!!!!
As many anaerobic prokaryotes were killed off due to the production of oxygen in the atmosphere…
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From Prokaryotes to Eukaryotes More changes/mutations in cells allowed
them to use the oxygen to release energy (Similar to what organelle…?) Oxygen gathering in the atmosphere allows
oxygen-using organisms to evolve= aerobic prokaryotes survived
Oxygen gathering in the atmosphere allows oxygen-using organisms to evolve=▪ The organisms use Aerobic Respiration are more
efficient cells
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What happens when a cell eats?
Usually when a single-celled organisms eats, it will digest the food and then release the rest as waste.
THANKFULLY, somehow something went wrong… Which gave rise to Eukaryotic cells
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From Prokaryotes to Eukaryotes
Aerobic prokaryotes survived Larger prokaryotes ate smaller
aerobic & photosynthetic prokaryotes = EUKARYOTES! endosymbiotic theory(Trash bag
Demo)
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From Prokaryotes to Eukaryotes
[Endo = "within"] [symbiosis = “together”]
Endosymbiosis = Each single cell was engulfed by a single, larger prokaryotic cell at some point- Not digested becomes a part of the cell
Endosymbiotic Theory = “mitochondria-like” prokaryotes were free living (did
aerobic cellular respiration = used oxygen) “chloroplast-like”prokaryotes were free living (did
photosynthesis = used sunlight) These single free-living prokaryotic cells became
organelles of other larger cells; they formed a symbiotic relationship = endosymbiosis = first eukaryotic cells
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Evidence for the Endosymbiotic Theory
Lynn Margulis researched in 1960's, published in 1981▪ proposed the endosymbiotic theory based on:
1) Mitochondria/Chloroplast have their own DNA similar to prokaryotic DNA
2) Mitochondria/Chloroplast divide like prokaryotes independent of the rest of the cell
3) Mitochondria/Chloroplast have two membranes4) Mitochondria/Chloroplast have simple ribosomes that are
the same size and structure as in prokaryotes5) Appearance of fossils, could best be explained by "endo-
symbiosis".
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Early Life
Around 2 BYA, slightly more complex organisms (heterotrophic eukaryotes) evolved Heterotrophs= organisms that have to eat/consume
other organisms for food/energy
Next to evolve were the colonial, unicellular eukaryotes that worked together multicellularity
Organisms moved from water about 450 MYA onto land – terrestrial life!
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Bacteria Archae-bacteria
AnimaliaFungiProtista Plantae
4500
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3500
3000
2500
2000
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1500
0
1000
Formation of earth
Molten- hot surface ofearth becomes somewhatcooler
Oldest definite fossilsof prokaryotes
Appearance of oxygenin atmosphere
Oldest definite fossilsof eukaryotes
First multicellularorganisms
Appearance of animalsand land plants
Colonization of landby animalsPaleozoic
Mesozoic
Cenozoic
Mill
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ears
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BR
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Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
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Geologic Time
1,900 2,500
4, 600
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Eras:Time
Geologic Time: begins when the Earth began 4.6 billion years ago
Includes: Precambrian Time :Archean and Proterozoic
Eras (4.6 billion years ago to 570 million years ago) ▪ Precambrian Period covers ~88% of Earth’s history▪ Made up of 2 eras- Archean and Proterozoic
Paleozoic Era (570 MYA to 225 MYA) Mesozoic Era (225 MYA to 65 MYA) Cenozoic Era (65 MYA to present) = TODAY!
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ErasWhat Came Into Existence?
▪ Archean-▪ Proterozoic-
▪ Paleozoic- Protists, sponges, and jelly fish to insects and amphibians and early reptiles; Bryophytes, mosses, and ferns (life move from sea to land)
▪ Mesozoic- Early mammals, early flowering plants, dinosaurs and other reptiles dominate
▪ Cenozoic- Mammals began to dominate, primates and humans arose (Primative horses Modern horses)
Single celled organisms (prokaryotes and protists), fungi, and simple invertebrates
Geologic Time and Relative Dating
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Review
Geologic Time: begins when the Earth began 4.6 billion years ago
Includes: Precambrian Time :Archean and
Proterozoic Eras (4.6 billion years ago to 570 million years ago)
Paleozoic Era (570 MYA to 225 MYA) Mesozoic Era (225 MYA to 65 MYA) Cenozoic Era (65 MYA to present) =
TODAY!
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Fossils
Fossils Preserve only the hard parts usually Burgess Shale- quick reading Traces of Organisms▪ Tracks, footprints, burrows▪ Imprints of leaves or fish which shows the surface
features; shells leave molds of empty cavities; sand or mud fills a mold producing a cast (replica of original)
▪ Waste material = castings, eating habits of animals
▪ Stones in digestive system (dinos)
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Fossil Record
▪Shows evidence for continental drift▪Shows evidence for mass extinction▪Shows evidence for evolution (slight changes in morphology = the way something looks)▪Fossils can be dated by looking at the layer of rock they are in compared to other layers = RELATIVE DATING
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Mass Extinctions
Mass Extinction: A large number of species on Earth are eliminated due to a drastic change in the environment or catastrophic event occurs Considered a MASS EXTINCTION when at least 50%
of all of the species die out Each Era ended with a mass extinction (sort of) as
well as many other extinctions throughout Earth’s history▪ Extinction with the biggest impact on life was the Permian
Extinction that wiped out 95% of all species Scientists predict there will be a 6th mass extinction
to end this era… Yikes =(
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Relative Dating
Relative Dating: placing rocks (containing fossils) in their proper SEQUENCE OF FORMATION; compare one rock to another rock by examining their placement in the Earth; compare 1st, 2nd, 3rd, etc. The layer on top is the youngest (unless
it has been turned over) The layer below is older (unless it has
been turned over)
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Example: Place order of rocks from oldest to youngest.
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Answers… oldest to youngest
H G F Fault D Intrusion
(C) B E A Stream
Absolute Dating and the Fossil Record
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Absolute Age
Absolute Age: actual age of the rock Radioactive Decay: isotopes that emit
particles and energy at a constant rate from their nuclei▪ Change to new isotope of same element or
new element all together▪ Natural Clocks = measure how much original
isotope is present compared to how much new isotope is present
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Example - Uranium
Example: Uranium emits 2 protons and 2 neutrons =
RADIOACTIVE DECAY▪ Uranium – parent element (unstable)▪ Lead – daughter element (stable)
Half-Life: time required for half of any given amount of radioactive material to decay into the daughter elements U-238 to decay into Pb- 206 is 4.5 billion years Example: 10 g of U- 238, after 4.5 billion years = 5 g
of U-238 and 5 g of Pb-206 After another 4.5 billion years – 2.5g of U-238 and 7.5
g of Pb-206
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Carbon Dating
Carbon Dating: more recent samples = carbon – 14 decays to nitrogen – 14 Usually C-12 and C-14 are constant, but
after death, C-12 and C-14 are not taken in, so amount of C-14 remaining breaks down to N-14
Half-life of C-14 is 5,730 years – find age of organic material (early humans, wood, bones, shells)
Ages up to 70,000 years old