Origins of Life Origin of Eukaryotic Cells



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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 life
  • Eukaryotic cells have a nuclei, have complex organelles, have mitochondria
  • Prokaryotic cells do not have a nuclei (simpler organisms)

Origin of Eukaryotic Cells

  • Endosymbiotic 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 Cells

  • Abiogenesis
  • 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 Margulis

  • 1960 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 DNA

  • Similar 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 Pasteur

  • He 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 Africa
    • In 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

  • 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:

  • Two important developments in the evolution of hominids:
  • Upright Posture (leading to 2 – legged walking)
  • Brain Enlargement

Researchers have proposed how the human brain grew so big.

  • Researchers have proposed how the human brain grew so big.
    • superior intelligence = weak jaw muscles
  • A mutation 2.4 million years ago could have left us unable to produce one of the main proteins in primate jaw muscles
  • Lacking the constraints of a bulky chewing apparatus, the human skull may have been free to grow, the researchers say.

Walking Upright

  • Walking Upright
  • Bipedalism – 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

  • 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

Language

  • Language
  • Estimates 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

  • 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

  • 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 Ethiopia
      • Also supported by DNA

Molecular biologist analyzed mitochondrial DNA from living humans around the world

  • 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 Evolution

  • Book: “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 Evolution

  • Prior to Darwin 2 theories about how life on
  • Earth prevailed:
  • Species are fixed or permanent
  • Do not change
  • That Earth was less than 10,000 years old and stayed relatively unchanged
  • People 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 Evolution

  • In 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

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

Darwin’s Theory of Evolution

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

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

Darwin’s Theory of Evolution

  • Galápagos 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
  • Hutton
  • Lyell

James Hutton

  • Recognized 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 Lyell

  • Argued 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.

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.

Darwin’s Theory of Evolution

  • In 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 theory
  • Together they released their findings
    • One year later Darwin released his book “The Origin of Species”

Darwin’s Theory of Evolution

  • Darwin’s 2 Main Points:
  • Species of organisms living on Earth today descended from ancestral species
  • Descendants spread into various habitats over millions of years
  • Descent with Modification: Accumulated different
  • modifications, or
  • adaptations to diverse
  • ways of life
  • This accounted for the diversity of life

Darwin’s Theory of Evolution

  • Natural Selection is the mechanism for evolution
  • Natural 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 adaptation
  • Natural selection is another way of defining evolution

Fossils

  • The preserved remains or markings left by organisms that lived in the past

Fossil Record

  • The chronological collection of life’s remains in the rock layers
  • Older rocks lower in the crust

Sedimentary Rock Formation

  • Can 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

Fossils

  • Fossil 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
  • Extinct – Species that no longer exist
  • Help scientist reconstruct the past
  • DO DO Bird became extinct 17th Century

Paleontologist

  • Scientist who study fossils
  • Have discovered fossils of many ancestral life forms that link past and present
  • Whales once had hind legs

Mass Extinction

  • A 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 Structure

  • Function is different to adapt to different functions

Similarities in Structure

  • Homologous Structures – similar structures in
  • species sharing a
  • common ancestor
  • More evidence “proving” evolution?
  • Descent 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 Development

  • Embryos 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

  • Embryology – 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

Biogeography

  • The 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:
  • Closely related species differentiate in slightly different climates
  • Distantly related species develop similarities in similar environments.

Biogeography

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
  • Population – 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

Natural Selection is the Mechanism of Evolution

  • Darwin’s theory of Natural Selection was/is based on two sets of observations:
  • Overproduction
  • Variation – differences among members of the
  • same species
  • Individuals with inherited traits that are best suited to the local environment survive and reproduce

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

Artificial Selection

  • The 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 Selection

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

Artificial Selection

  • Darwin 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 – Humans Choose
  • 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 Evolution

  • Evidence 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 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 thousand years is “abrupt” when you talk about 3.8 billion years of Earth’s history

Rate of Evolution

  • Every 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

Microevolution

  • Although 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 Macroevolution

  • Microevolution – Change in allele frequencies
  • within a population
  • Macroevolution
  • (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

  • Speciation – the origin of a new species
  • With speciation comes biodiversity
  • Temporal Isolation – Happens when 2 or more
  • species reproduce at different
  • times

Reproductive Barriers

  • Reproductive Isolation – a reproductive barrier
  • that keeps two species
  • from interbreeding
  • Timing
  • Two similar species may have different breeding seasons
  • Behavior
  • Two similar species may have different courtship or mating behaviors

Geographic Isolation and Speciation

  • 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

Geographic Isolation and Speciation

  • Adaptive Radiation – Evolution from a common ancestor that results in diverse species adapted to different environments
  • Islands create conditions that seem to favor speciation

Geographic Isolation and Speciation

  • 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 Speciation

  • 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 Pool

  • All alleles in all the individuals that make up a population
  • This is where genetic variation and the raw material of evolution is stored
  • Variety 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 Pool

  • Processes 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 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 – 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:

  • Genetic 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

Main Factors that Mechanically Effect a Gene Pool:

  • The Bottleneck Effect
  • Disasters
    • 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 others
  • Some eliminated altogether
  • This decreases genetic variation
    • This could lead to the inability for an organism to survive

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

Main Factors that Mechanically Effect a Gene Pool:

  • Natural Selection
  • Gene Flow and Mutation
  • Also have a role in changes in gene pools
  • Gene Flow – The exchange of genes with another
  • population
  • Occurs 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

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

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

Gene Flow will...

  • Reduces genetic differences between populations
  • If extensive enough, gene flow can mix together populations into a single common gene pool

Mutations

  • If 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 Fitness

  • Natural 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 Fitness

  • Fitness – (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 – 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 Evolution

  • Evolution of Antibiotic Resistance in Bacteria
  • Antibiotics – 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 kill
  • Antibiotic resistance evolves by Natural Selection
    • Some bacteria always survive
    • Multiply quickly
    • So Do Not Take Antibiotics Unless Necessary And Take Them All


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