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Origins of LifeOrigins of Life
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Origin of Eukaryotic Cells
The evolution from eukaryotic cells from prokaryotic was one of the most important events in the history of life
Eukaryotic cells have a nuclei, have complex organelles, have mitochondria
Prokaryotic cells do not have a nuclei (simpler organisms)
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Origin of Eukaryotic CellsEndosymbiotic Theory
• Proposes that a symbiotic relationship evolved over time, between primitive eukaryotic cells and the prokaryotic cells within them.• One hypothesis states that mitochondria evolved from
endosymbiotic prokaryotes that were able to use oxygen to generate energy rich ATP.
• Another proposes that chloroplast evolved from endosymbiotic prokaryotes that had the ability to photosynthesis
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Endosymbiotic Theory
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Origin of Eukaryotic CellsAbiogenesis
The study of how life originally arose on the planet, encompasses the ancient belief in the spontaneous generation of life from non living matter.
The Italian physician, Francisco Redi, disproved the theory of spontaneous generation by conducting a simple experiment.
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Theories On the Origins of Life
1953 - Stanley Miller and Harold Urey filled a sterile flask of water (simulate ocean) and boiled it.– They added methane, ammonia, and hydrogen
(simulate early Earth atmosphere)– They passed gases through electrodes (simulate
lightning– Passed gases through a condensation chamber,
where cold water cooled them, causing drops to form.
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Theories On the Origins of Life - Miller/Urey
The liquid circulated for a week in the apparatus.
Results: 21 Amino Acids Produced – Building Blocks of Protein
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Theories On the Origins of Life - Miller/Urey
Miller and Urey’s experiment suggested how mixtures of the organic
compounds necessary for life could have arisen from simpler compounds
on a primitive Earth.
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Alexander Ivanovich Oparin Russian biochemist, notable for his contributions to the theory of the origin of life on Earth– “primordial soup” theory of the evolution
of life from carbon-based molecules. – he had first introduced his concept of a
primordial organism arising in a brew of already-formed organic compounds.
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Lynn Margulis1960 Margulis (Boston University) gathered
evidence that supported endosymbiotic theory.
She discovered that mitochondria and chloroplast contained DNA that was similar to bacterial DNA
Mitochondria and chloroplast have ribosomes that size and structure are like that of bacteria
Also mitochondria and chloroplast reproduce by binary fission; like bacteria
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Lynn Margulis
These similarities provide strong evidence of a common ancestry between free-living bacteria and the organelles of living eukaryotic cells.
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RNA to DNASimilar experiments have shown that conditions similar to the ones created by Miller & Urea have resulted in RNA sequences to be made.
RNA World Hypothesis States:
• RNA existed by itself before DNA, from this simple RNA based system, several steps could have led to DNA-directed protein synthesis
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Louis PasteurHe was the first person, convincingly to show that bacteria cause disease.
He continued on to establish a vaccine for anthrax and rabies (viral)
Biogenesis – the production
of new living organisms or
organelles
• Living things came from
living things
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Humans Have a Relatively Short History
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Fossil Records
Indicate that modern humans have a relatively recent history
Began in AfricaIn a short time, humans have become the most numerous and widespread large animal on Earth
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Hominoids – (AKA Hominids) great apes, include gibbons, orangutans, gorillas, chimpanzees and humans
Hominines - the lineage that led to humans and all other species more closely related to us than to chimpanzees.
Homo sapiens (sapiens) (modern human) – only species in existence today • Many hominines lived in the past
• Earliest hominines may have lived 6 to 7 million years ago
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Two important developments in the evolution of hominids:
1. Upright Posture (leading to 2 – legged walking)2. Brain Enlargement
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Researchers have proposed how the human brain grew so big.
superior intelligence = weak jaw musclesA mutation 2.4 million years ago could have left us unable to produce one of the main proteins in primate jaw musclesLacking the constraints of a bulky chewing apparatus, the human skull may have been free to grow, the researchers say.
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Walking UprightBipedalism – walking on two feet• Australopithecus Afarensis – oldest evidence of
upright posture and walking on two feet.• Walked upright 4 million years ago• Lucy – a female Australopithecus Afarensis
• 3 ½ feet tall, head about the size of a softball• Australopithecus Afarensis species were extinct by
about 1.2 million years ago
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Lucy
Dikika Baby
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Enlarged Brain• First enlarged brain relative to body size
appeared 2.5 million years ago• Many skulls have been found between the size of
Australopithecus and H. Sapiens• Simple stone tools were found with these species• Species name Homo habilis (Handy Man)
• Used skilled hands and big brains to invent tools
• Enhanced the ability to hunt, gather food, and scavenge for food
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Brain Structure
Oblongata
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LanguageLanguageEstimates range from about two million years ago, during the time of Homo habilis (Handy Man), to as recently as forty thousand (40,000) years ago, during the time of Cro-Magnon man,
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Homo habilis - Handy Man• Opposable Thumb – thumb could touch the tips of the fingers, enabling the grasping of objects and the use of tools
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There are many hypothesis for the origin of fully modern humans
Fossil records now suggest that ancestors originated in Africa
Homo Sapien fossils that look like today’s modern Homo Sapien are about 195,000 years old and it was discovered in Ethiopia
Also discovered in EthiopiaAlso supported by DNA
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Molecular biologist analyzed mitochondrial DNA from living humans around the world
determined when they last shared a common ancestor.
The estimated date for that African common ancestor is between 200,000 and 150,000 years ago.More recent DNA data suggest that a small subset of those African ancestors left northeastern Africa between 65,000 and 50,000 years ago to colonize the world.Data supports Theory
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Darwin’s Theory of EvolutionBook: “The Origin of Species” 1859
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Darwin’s Theory of Evolution
“The Origin of Species”Provided a framework for understanding Earth’s diversity of organisms and their relationships to one another and their environment.
Evolution – All the changes that have
transferred life over an immense time
A biological history of life on Earth
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Darwin’s Theory of EvolutionPrior to Darwin 2 theories about how life on
Earth prevailed:1. Species are fixed or permanent
Do not change2. That Earth was less than 10,000 years old and
stayed relatively unchangedPeople questioned these theories because they became aware of the incredible diversity of organisms past and present
– As well as geological processes
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Darwin’s Theory of Evolution Mid – 1700’s – French Naturalist Georges Buffon began to suggest that Earth might be much older than a few thousands – This was suggested by fossil records
Buffon saw that specific fossils looked like living animals but were slightly different
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Darwin’s Theory of EvolutionIn early 1800’s French Naturalist Jean Baptiste Lamarck proposed that life changed or evolved.– He explained “evolution as a process of adaptation”– Or “acquired traits”
Adaptation – (today) An inherited characteristic that improves
an organism’s ability to survive and reproduce
in a particular environment
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Darwin’s Theory of Evolution
HMS Beagle The mission was to chart the South American coast for the British Navy– Darwin was a 22 year old college graduate who’s job
was to study geology, plants, and animals encountered on the voyage
– While the rest of the crew surveyed; Darwin was dropped off collecting 1000’s of specimens, later picked up
• Dropped off at other points• He studied adaptations of animals from the
Brazilian jungle, grassland to Antarctica
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Darwin’s Theory of Evolution
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Darwin’s Theory of Evolution
Before his voyage, in his writings, Darwin believed in the concept of fixed or unchanging species– He questioned his beliefs during the voyage– After he returned to England and studied his
findings he became convinced that species change as they adapt to their environments
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Darwin’s Theory of Evolution
Darwin discovered that species from South America were unique– Different from European animals– Even Fossil records showed gigantic versions
of the same animals in South America
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Darwin’s Theory of EvolutionGalápagos Islands
Many important observations came from the Galápagos.
A chain of relatively young volcanic islands of the South American coast
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Darwin’s Theory of Evolution - Galápagos Islands
Islands had many unique organisms– Many were similar but somewhat different
from the mainland• They were different even between islands
– Darwin inferred that mainland species adapted after colonizing
• Adapting to new environment.
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Darwin’s Theory of Evolution - Geology
Reading books by Charles Lyell & James Hutton (geologist) influenced Charles Darwin
1785 Hutton presented his hypothesis; geological processes have shaped the Earth
Lyell built on the work of Hutton & others published Principles of Geology in 1830
HuttonLyell
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James HuttonRecognized there were geological processes that lead to features like mountains, valleys, and that rock layers seemed to be folded or bent
He also stated that forces beneath the Earth were forcing rock layers upward
Conclusion our planet is much older than we thought.
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Charles LyellArgued that the Laws of Nature are constant over time
Scientist must explain past events in terms of processes they can observe in the present
Uniformitarium – geological processes we can
see in action today must be
the same ones that shaped
Earth millions of years ago.
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Darwin’s Theory of Evolution
Another influence on Darwin was Thomas Malthus– Malthus theorized that populations can grow
faster than the rate at which food and other resources can be produced
– Darwin realized that this applied to all species.
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Darwin’s Theory of EvolutionIn 1858; before Darwin released his 200 page essay describing his essay that outlined his theory, another Naturalist, Alfred Wallace had come up with the same theoryTogether they released their findings– One year later Darwin released his book “The
Origin of Species”
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Darwin’s Theory of EvolutionDarwin’s 2 Main Points:
1. Species of organisms living on Earth today descended from ancestral species
Descendants spread into various habitats over millions of years
Descent with ModificationDescent with Modification: Accumulated different
modifications, or
adaptations to diverse
ways of life
This accounted for the diversity of life
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Darwin’s Theory of Evolution2. Natural Selection is the mechanism for evolutionNatural SelectionNatural Selection – The process by which individuals with inherited characteristics well-suited to the environment leave more offspring on average than other individuals
The result of Natural Selection is adaptationNatural selection is another way of defining evolution
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FossilsThe preserved remains or markings left by
organisms that lived in the past
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Fossil RecordThe chronological collection of life’s remains
in the rock layers
Older rocks lower in the crust
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Sedimentary Rock FormationCan happen on the ground or underwater – Animal Dies– Covered with sediments
• Volcanic ash
• Dust
• Silt
• Clay
– Overtime soft tissue decays– Bones decay and “space” is filled with minerals
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FossilsFossil record provides evidence of changing life– Oldest fossils are 3.8 billion years old
(Greenland)• They are basically chemical traces of life
– Fossils of prokaryotes (bacteria/archaea) have been found in rocks 3.5 billion years old
• Evidence that prokaryotes are the oldest form of life
ExtinctExtinct – Species that no longer exist
Help scientist reconstruct the past
DO DO Bird became extinct 17th Century
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PaleontologistScientist who study fossils
Have discovered fossils of many ancestral life forms that link past and present
Whales once had hind legs
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Mass ExtinctionA brief episodes of great species lost– Cretaceous Period – the world last enormous
amount of species
Extinction is unavoidable in a changing world– Mass extinction provided the surviving
organisms with new opportunities.
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Geographic Distribution
Differences and similarities between organisms in different parts of the world were some of the first observations that Darwin made on his voyage.– Suggest organisms evolved from ancestral forms
– Also serves as a clue, how modern species have evolved
• Example: same species on two islands on different parts of the world look like those near mainland
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Similarities in StructureCan provide clues to evolutionary history– Forelimbs of all mammals consist of the same skeletal
parts
Function is different to adapt to different functions
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Similarities in StructureHomologous StructuresHomologous Structures – similar structures in
species sharing a
common ancestor
More evidence “proving” evolution?
Descent ModificationDescent Modification – A remodeling process, a
term used by Darwin
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Vestigial Structures
Are remnants of structures that may have had important functions in an ancestral species, but have no clear function in some of the modern
descendants.Often smaller in size
Supported reasoning is Natural Selection would favor the survival and reproduction of individuals with genes for reduced version of those structures
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Vestigial Structures
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Similarities in DevelopmentEmbryos of closely related organisms often have similar stages in development
More evidence that mammals are related and
descended with modification, from a
common ancestor
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Evolution and Development
EmbryologyEmbryology – the study of the processes of multi-cellular organisms as they develop from fertilized eggs to fully formed organisms
Embryology focuses on the genes that control development of an organism as it begins to take shape
Important in evolution are subtle changes in the developmental programs of organisms– In some cases, the remodeling process of
evolution involves changes in the rate or timing of some event in the development of an organisms
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BiogeographyBiogeographyThe study of where organisms live now and where they and their ancestors lived in the past.
Darwin had significant 2 biographical patterns in his theory:
1.Closely related species differentiate in slightly different climates
2.Distantly related species develop similarities in similar environments.
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BiogeographyBiogeography
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Molecular Biology
Two species that have genes and proteins with sequences that are similar must have been inherited from a relatively recent common ancestor– The greater number of differences in DNA and
protein, the less likely they share a common ancestry
• Humans are closely related to primates because there is only a 5% differences in the total DNA between these two species
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Molecular Biology
Darwin believes “All Life Forms are Related”
Molecular evidence includes the common genetic code shared by all species– Passed on along all branches of evolution
– Evidence supports for the unity and diversity of life
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Molecular Biology
Molecular Clock– Emile Zuckerandl and Linus Pauling (1962)
– Noticed that the number of amino acid differences in hemoglobin between different lineages changes roughly linearly with time
– They generalized this observation to assert that the rate of evolutionary change of any specified protein was approximately constant over time and over different lineages.
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Natural Selection is the Mechanism of Evolution
Darwin saw a link between adaption to the environment and the origin of new species
PopulationPopulation – a group of individual of same species
living in the same area at the same time• In Natural Selection if you had one species living
on different islands, they would adapt to their environment• Over time they would get more and more different
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Natural Selection is the Mechanism of Evolution
Darwin’s theory of Natural Selection was/is based on two sets of observations:
1. Overproduction
2. Variation – differences among members of the
same species• Individuals with inherited traits that are best suited
to the local environment survive and reproduce
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Natural Selection is the Mechanism of Evolution
2. Variation• As this process repeats over many generations
each generations has a higher proportion of individuals with the advantageous traits• Darwin’s also suggested that Natural Selection could
cause two isolated populations to become separate species
• That would explain the Galapagos Islands’ finches
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Artificial SelectionThe selective breeding of domesticated plants and animals to produce offspring with genetic traits that humans value– Darwin found more evidence to support his
ideas with results of artificial selection• Plant Breeder: might seek to improve grain
production, disease resistance, or protein content
• Animal Breeder: seek growth rate or temperament
Darwin observed that breeders selected individuals with desired traits as breeding stock
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Artificial SelectionBreeders play a role in the environment by allowing only those plants and animals with desired traits to reproduce
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Artificial SelectionDarwin noticed that Artificially Selected species could produce a great deal of change in a short time– He compared this through Natural Selection but
reasoned it would take 1000’s of years
Artificial Selection Artificial Selection – Humans Choose
Natural Selection Natural Selection – Benefits organisms in their
particular environment
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Pesticides
Poisons used to kill insects that are pest in crops and in homes– At first pesticides are very effective– Later they are less effective
Why: If an insects survives First attack (no pesticide
is 100% effective)• Survivors replicate – offspring inherit gene for
pesticide resistance
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Rate of EvolutionEvidence shows that evolution has often proceeded at different rates for different organisms at different times over the long history of life on Earth
Gradualism – evolution needed to be slow
and steady
• Supported by fossil record
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Geographic Isolation and Speciation
Punctuated EquilibriumPunctuated Equilibrium – a model suggest that species often diverge in spurts of
relatively rapid change.
Long periods of little change (equilibrium) in a species are broken, or punctuated by shorter times of speciation
Speciation can sometimes be rapid– A few hundred to a few thousand years
• Because of a new environment
A few thousand years is “abrupt” when you talk about 3.8 billion years of Earth’s history
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Rate of EvolutionEvery now and then something happens to upset the state of equilibrium organisms are in:
Punctuated Equilibrium – the term used to
describe equilibrium that is interrupted that is interrupted by brief periods of more rapid change
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MicroevolutionAlthough they lived in the same area (and had no internet) Darwin and Mendel never compared their work– After they both died the union between genetics and
evolutionary biology came together
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Microevolution to MacroevolutionMicroevolution – Change in allele frequencies
within a population
MacroevolutionMacroevolution
(More dramatic biological changes)
Evident in fossil record– Include the origin of different species– The extinction of species– The evolution of major new features of living
things• Wings• Flowers
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Microevolution to Macroevolution
SpeciationSpeciation – the origin of a new species
With speciation comes biodiversity
Temporal Isolation – Happens when 2 or more
species reproduce at different
times
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Reproductive BarriersReproductive Isolation Reproductive Isolation – a reproductive barrier
that keeps two species
from interbreeding
TimingTiming
Two similar species may have different breeding seasons
BehaviorBehavior
Two similar species may have different courtship or mating behaviors
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Geographic Isolation and Speciation
Geographic Isolation Geographic Isolation – Separation of populations
due to geographic
change or dispersal to
geographically isolated
places
How well the geographic barrier keeps populations apart depends on the ability of organisms to move about.
volcano papua new guinea
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Geographic Isolation and Speciation
Adaptive RadiationAdaptive Radiation – Evolution from a common ancestor that results in diverse species adapted to different environments
Islands create conditions that seem to favor speciation
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Geographic Isolation and Speciation
Convergent Evolution Convergent Evolution – process by which unrelated organisms independently evolve
similarities when adapting to similar
environments.
Mammals that feed on ants Book page 551
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Geographic Isolation and SpeciationCoevolution Coevolution - The process by which 2 species evolve
in response to changes in each other over time.
The relationship between 2 organisms often becomes so specific that neither organism can survive without the other
Thus, an evolutionary change in one organism is followed by a change in the other organism
The relationship between flowering plants and their pollinators. Flowering plants rely on pollinators to transport pollen among individual plants and thus enable cross-pollination.
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Gene PoolAll alleles in all the individuals that make up a All alleles in all the individuals that make up a
populationpopulationThis is where genetic variation and the raw material of evolution is storedVariety is expressed as a result in sexual recombination– Seen in populations that reproduce sexually
The process of meiosis and fertilization shuffle alleles within a gene pool and “deal” them out to offspring in fresh combinations
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Changes in Gene PoolProcesses that lead to genetic variation-mutations and sexual recombination are random
Natural Selection (and evolution) are not random.– Environmental factors effect the survival and thus the
reproductive success of an organism
Some alleles become more common in the gene pool
Frequency of AllelesFrequency of Alleles – how often certain alleles
occur in the gene pool
Thus expressed more commonly
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Gene Pool
Merging Mendel and Darwin’s theories led to looking at evolution based on genetic changes
Microevolution Microevolution – evolution on the smallest scale.
A generation to generation change in the frequency of alleles within a population
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Main Factors that Mechanically Effect a Gene Pool:
1.1. Genetic DriftGenetic Drift
A change in a gene pool of a population due to chance
All populations are subject to some genetic drifts
– The smaller the population the more dramatic the change.
• Bottle Neck Effect
• Founder Effect
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Main Factors that Mechanically Effect a Gene Pool:
The Bottleneck EffectThe Bottleneck EffectDisasters – Earthquakes, floods, droughts, and fires may drastically
reduce the size of a population• Decrease Size = Decrease Gene Pool
By chance, certain alleles may then be represented more frequency than othersSome eliminated altogetherThis decreases genetic variation– This could lead to the inability for an organism to
survive
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Main Factors that Mechanically Effect a Gene Pool:
Founder Effect - happens when a few individuals colonize an isolated island, lake, or some other new habitat– The smaller the colony, the less genetic make up will
represent the gene pool of the larger population which the colony came from.
Chance reduces make-up of the founders of the colony
Galapagos Island Finches
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Main Factors that Mechanically Effect a Gene Pool:
Natural SelectionNatural Selection
Gene Flow and Mutation
Also have a role in changes in gene pools
Gene FlowGene Flow – The exchange of genes with another
populationOccurs when fertile individuals or their gamates (sex cells) migrate between populations
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Main Factors that Mechanically Effect a Gene Pool: Natural Selection
Directional Selection
When individuals at one end of the curve have a higher fitness than individuals in the middle or the other end– The range of phenotypes shifts because some
individuals are more successful at surviving and reproducing than others
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Main Factors that Mechanically Effect a Gene Pool: Natural Selection
Stabilizing Selection
When individuals near the center of the curve have higher fitness than individuals at either end
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Main Factors that Mechanically Effect a Gene Pool: Natural Selection
Disruptive Selection
When individuals at the outer ends of the curve have higher fitness than individuals near the middle of the curve– Acts against individuals of an individual type
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Gene Flow will... Reduces genetic differences between populations
If extensive enough, gene flow can mix together populations into a single common gene pool
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MutationsIf a mutation is carried by a gamete, the mutation enters the population’s gene pool– Natural Selection and Genetic Drift (or both) can
influence whether the frequency of a new mutation increase in population
Overtime; mutation plays a key role in evolution as the original source of genetic variation– Raw material for Natural Selection– Really important in asexual reproducing organisms –
like bacteria– In sexual reproducing organisms with long generation
spans most variation is due to scrambling existing alleles not mutation
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Natural Selection and FitnessNatural Selection is a blend of chance and sorting– Chance = mutations and sexual recombination's
of alleles– Sorting (Not Random) is accomplished by
differences in reproducing success
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Natural Selection and FitnessFitnessFitness – (in Biology) is the contribution that an
individual makes to the gene pool of the
next generation compared to the
contributions of other individuals
Polygenic Trait Polygenic Trait – Trait controlled by 2 or more
genes
Survival to reproduce (maturity) is key
“Survival of the Fittest” to describe Natural Selection is only accurate if offspring can “survive” and can reproduce.
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Natural Selection and Fitness“the struggle for existence”
That may be a conflict for food or a battle against the elements.
• Part of the evidence for this struggle is the immense potential that animal and plant populations have to increase in size. • Even the elephant, one of the slowest breeders in the animal
kingdom, could take over the planet if it were allowed to reproduce unhindered for long enough. After 500 years, one pair would leave 15 million descendants,
• Darwin tells us populations are kept in check because there
are not enough resources to go around, and that leads to
intense competition for survival.
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Health Science and EvolutionEvolution of Antibiotic Resistance in BacteriaEvolution of Antibiotic Resistance in Bacteria
AntibioticsAntibiotics – Medicines that kill or slow the growth of bacteria
Widespread use has caused the evolution of antibiotic – resistant populations of the very bacteria that antibiotic is trying to killAntibiotic resistance evolves by Natural Selection– Some bacteria always survive– Multiply quickly
So Do Not Take Antibiotics Unless Necessary And So Do Not Take Antibiotics Unless Necessary And Take Them AllTake Them All