Life on Earth. Chapter 10. Origins. Early Earth Oldest rocks suggest Earth is 4.5 billion yrs old Condensed gases and dust Very hot initially, but outer surface cooled Heat is still produced by inner core of Earth Location just right from Sun – liquid water
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Life on Earth Chapter 10
Origins • Early Earth • Oldest rocks suggest Earth is 4.5 billion yrs old • Condensed gases and dust • Very hot initially, but outer surface cooled • Heat is still produced by inner core of Earth • Location just right from Sun – liquid water • Large oceans formed, atmosphere from volcanic activity • Oxygen was not present in the atmosphere
Origins con’t • Volcanic activity would have triggered large thunderstorms with lightening • Atmosphere would have had water vapor, methane gas, carbon dioxide nitrogen, hydrogen, hydrogen sulfide and ammonia. • From this mix arose organic molecules and the building blocks of nucleic acids and proteins
Cooled “atmosphere” so what formed would “rain” down into the “ocean”
First cells • Replicating molecules – simple molecules that could make more copies of themselves, would have become more common. Probably RNA. • RNA can function like a protein enzyme, so alone RNA molecules might have been able to self replicate • Sealed self from external environment in a membrane
First cells con’t • 3.4 billion (3400 million) year old cells • Rocks they are in are dated accurately • Size = modern bacteria • C12/C13 isotopes indicate fossilized organism, not rock without fossils • DNA is more stable than RNA • Cell Membrane critical
Cell membrane • If place phospholipids in salt solution, they will form spheres spontaneously • Such microspheres will even create new microspheres – but not replication as such • A combination of RNA or DNA with microsphere would give all of the components needed to call it life.
First Prokaryotic Life • 3.5 billion years ago • 2.5 billion years ago, some prokaryotes evolved the ability to capture sunlight energy to create molecules. • Waste = Oxygen • Cyanobacteria
Oxygen Accumulates • Oxygen in atmosphere • Many prokaryotes survive in places that lack oxygen – there today • Larger cells possible • First Eukaryotes 1.9 bya
Paleozoic Era (600-250 mya) • Multicellular organisms • Soft bodied (5-600 mya) • First aquatic plants • 1st vascular plants & terrestrial invertebrates (400 mya) • Age of fishes (400-360 mya) • First Reptiles (300 mya) • Mass extinction – cooling due to formation of Pangaea
Continental Drift • Evidence: • Shape of Continents • As lava cools, metal elements freeze according to their position relative to the Earth’s magnetic field • Continental drift is measured today • Fossil record indicates changing locations USGS website
Mesozoic Era (250-65 mya) • Pangaea starts to break up and a warm shallow sea forms in the center • Temperatures rise • Age of dinosaurs • First mammals (mouse sized) • First birds • First flowering plants
Mesozoic Era con’t • Largest dinosaurs dominated during the Jurassic Period (200-140 mya) • 2 large land masses formed • Mesozoic ended with impact of a large asteroid that cooled Earth rapidly • Mass extinction of most dinosaurs, others
Cenozoic Era (65 mya-present) • New species of mammals evolved • Flowering plants radiated • Grasslands arise • Continents move to modern locations • Hominidae evolve about 5 mya
365 day perspective • 1 picture taken each year, run film at 144 frames/ sec • Run projector continuously for 24 hr/day for 365 days • Jan, Feb, Mar, and most of April – blank screen • April 12 – oldest rocks • April 20 – 1st prokaryotes • May, June, July & Aug no change • Sept & Oct – Eukaryotes, multi-cellular organisms • Nov 16 = 600 mya
365 day perspective con’t • Nov 16 Paleozoic Era begins • Dec 1 age of fishes begins • Dec 14 age of reptiles (Mesozoic) begins and lasts 12.5 days • Dinosaurs and large reptiles dominate • Dec 26 at 11 PM mass extinction • Dec 31 4:45 PM = first species of Homo • 11:37 PM Homo sapiens first seen • 11:59 PM to midnight = entire history of human civilization since the start of agriculture
The age of fishes occurred during: A) The Cenozoic Era B) The Paleozoic Era C) The Mesozoic Era D) The Pre-cambrian Era
The classic experiments performed in the 1950s by Harold Urey and Stanley Miller were the first to show that: A) simple organic molecules, such as amino acids, could form spontaneously in the laboratory under chemical conditions mimicking those of primitive earth.B) water (H2O) could be separated into atmospheric oxygen and H2 gas.C) cosmic microwave background radiation (CMB), a type of electromagnetic radiation, fills the entire universe and provides support for the “big bang” model of the origin of the universe.D) naturally occurring antibiotics, such as penicillin, could be used to treat bacterial diseases.E) the average bill size of a population of Darwin’s finches changed with environmental conditions, proving that microevolution can occur within a human lifetime.
Phase 1 of the creation of life on earth was _____________________. Phase 2 was the formation of self-replicating, information-containing molecules. Phase 3 was the development of a membrane, which enabled metabolism and created the first cells. A) the formation of small molecules containing carbon and hydrogenB) the formation of DNAC) the development of a nucleus, which enabled metabolism and created the first cellsD) the increase in the amount of atmospheric oxygenE) the formation of RNA
What is a species? • Different kinds of organisms • Populations that interbreed • Can’t breed with other organisms under natural conditions • Reproductively isolated
How do new species evolve? • Process is called speciation • Requires populations to become reproductively isolated • Populations evolve separately • Both change to the point that when they re-encounter each other, individuals from the two populations can no longer interbreed
Forms of Speciation • Allopatric speciation • A population is split • Migration of small group to an island • River changes course • Mountain building • Sympatric speciation • No physical barrier • Something else causes reproductive isolation
Sympatric Speciation • More rare event • Mostly in plants • Rare in vertebrates • Some insect examples • If mate on particular type of plant • Mutation causes change in plant preference • Populations can be isolated due to food and mating location preference Apple maggot flies
Sympatric Speciation con’t Chromosome duplication Hybrid allopolypoidy • Error during meiosis • Doubled # sets of chromosomes • Can’t cross with parents, but can with self • Apples and bananas • Cross between 2 closely related species • Sterile hybrid reproduces asexually • Those offspring can reproduce together • Wheat, bananas, potatoes, coffee
The biological species concept is primarily based on: A) reproductive isolation.B) phylogenetic history.C) ecological niche.D) morphological differentiation.E) behavioral differentiation.
Horses and donkeys can breed and produce sterile offspring known as mules. Horses and donkeys remain separate species because of this hybrid sterility, which is: A) an allopatric barrier to reproduction.B) a postzygotic barrier to reproduction.C) a sympatric barrier to reproduction.D) a prezygotic barrier to reproduction.E) a good thing.
Plant species A has a diploid chromosome number of 18. Plant species B has a diploid chromosome number of 10. A new species, C, arises as an allopolyploid of species A and B. What is the most likely diploid chromosome number of species C? A) 38B) 28C) 10D) 46E) 18
Tree of Life • Evolutionary history can be visualized as a tree with branches • Branches show relationships among different species and where speciation occurred • Phylogeny is the study of the evolutionary history of groups of species • Based on structures, development, behavior, and genetics
Convergent Evolution These are Analogous traits – similar but do not share an evolutionary history Homologous traits = jaw of bat and mouse = share an evolutionary history Structures of wings are very different Vertebrate eye and eye of octopus and squid share many characteristics, but = convergent evolution
Which of the following BEST explains the finding that the nuclear DNA of house cats and African wild cats has a very high degree of similarity? A) Convergent morphological evolution has occurred.B) Convergent molecular evolution has occurred.C) House cats and African wild cats are both members of the family Felidae.D) Divergent morphological evolution has occurred.E) House cats and African wild cats share a recent common ancestor.
Sequencing DNA from different organisms has been a breakthrough for phylogenetics because: A) we can now build heat-tolerant animals. B) we now have a method to determine the relatedness of organisms that leave no fossils. C) it has reduced the impact of antibiotic resistance in bacteria. D) we can now recreate genomes from the past. E) All of the above are correct.
Macroevolution 1 of over 400 species of Anolis
Rate of Evolutionary Change For similar species the number of changes in DNA can give an estimate of the time since they diverged. For very different groups it is hard to make a comparison.