Transcript Life on Earth
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 1 st 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
USGS website 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
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
Human roots
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 – 1 st 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 (H 2 O) could be separated into atmospheric oxygen and H 2 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.
gas.
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 hydrogen B) the formation of DNA C) the development of a nucleus, which enabled metabolism and created the first cells D) the increase in the amount of atmospheric oxygen E) 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
Reproductive Isolation
Classification
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
Error during meiosis Doubled # sets of chromosomes Can’t cross with parents, but can with self Apples and bananas
Hybrid allopolypoidy
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) 38 B) 28 C) 10 D) 46 E) 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
Monophyletic groups
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 harder to make a comparison.
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
Convergent Evolution con’t
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 vs Microevolution
1 of over 400 species of Anolis
Macro- versus Microevolution
Rate of Evolutionary Change
Adaptive radiations
Times of rapid species formation There has been an extinction event that opened up niches for those who survived New habitat is available New innovation that opens new niches
Extinction
Extinction of species has occurred regularly though time Mass extinctions are dramatically larger events that have occurred periodically Humans are causing another right now – doesn’t show yet, but the present rate of extinction is very high
The ___________________ propelled flowering plants to an explosive adaptive radiation.
A) colonization of land B) mass extinction of fern-like plants C) colonization of the Galápagos Islands D) evolutionary innovation of the flower E) evolutionary innovation of the leaf
_________________ produces new species and _________________ takes them away.
A) Speciation; extinction B) Extinction; speciation C) Convergent evolution; extinction D) gradual change; punctuated equilibrium E) Background extinction; mass extinction