Origins of Life. Origin of Eukaryotic Cells The evolution from eukaryotic cells from prokaryotic was one of the most important events in the history of

Origins of LifeOrigins of Life

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)

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

Endosymbiotic Theory

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.

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.

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

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.

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.

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

Lynn Margulis

These similarities provide strong evidence of a common ancestry between free-living bacteria and the organelles of living eukaryotic cells.

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

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

Humans Have a Relatively Short History

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

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

Two important developments in the evolution of hominids:

1. Upright Posture (leading to 2 – legged walking)2. Brain Enlargement

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.

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

Lucy

Dikika Baby

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

Brain Structure

Oblongata

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,

Homo habilis - Handy Man• Opposable Thumb – thumb could touch the tips of the fingers, enabling the grasping of objects and the use of tools

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

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

Darwin’s Theory of EvolutionBook: “The Origin of Species” 1859

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

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

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

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


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



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


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

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

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.

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

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.

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.


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.

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”

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

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

FossilsThe preserved remains or markings left by

organisms that lived in the past

Fossil RecordThe chronological collection of life’s remains

in the rock layers

Older rocks lower in the crust

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

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

PaleontologistScientist who study fossils

Have discovered fossils of many ancestral life forms that link past and present

Whales once had hind legs

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.

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

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

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

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

Vestigial Structures

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

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

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.

BiogeographyBiogeography

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

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

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.

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


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


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

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

Artificial SelectionBreeders play a role in the environment by allowing only those plants and animals with desired traits to reproduce

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

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

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

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

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

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

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

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

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


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


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


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

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.

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

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

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

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


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


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


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

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


Stabilizing Selection

When individuals near the center of the curve have higher fitness than individuals at either end


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

Gene Flow will... Reduces genetic differences between populations

If extensive enough, gene flow can mix together populations into a single common gene pool

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

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

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.

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.

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

Documents

Origins of Life. Origin of Eukaryotic Cells The evolution from eukaryotic cells from prokaryotic was one of the most important events in the history of