The Evolution of Prokaryotes - PowerPoint PPT Presentation

the evolution of prokaryotes n.
Skip this Video
Loading SlideShow in 5 Seconds..
The Evolution of Prokaryotes PowerPoint Presentation
Download Presentation
The Evolution of Prokaryotes

play fullscreen
1 / 74
The Evolution of Prokaryotes
Download Presentation
Download Presentation

The Evolution of Prokaryotes

- - - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript

  1. The Evolution of Prokaryotes • Scientists use fossils to study evidence of early life on Earth. • Fossil: the preserved or mineralized remains or imprints of an organism that lived long ago. • The oldest fossils are 3.5 billion year old prokaryotes. • Some of the first prokaryotes were marine cyanobacteria. • Cyanobacteria: photosynthetic prokaryotes • Helped release oxygen gas into oceans, and eventually the air. Benagh

  2. E.coli: an example of Eubacteria: Two Groups of Prokaryotes • Two different groups or prokaryotes evolved. • Eubacteria: prokaryotes that contain a chemical called peptidoglycan in their cell walls. • Archaebacteria: prokaryotes that lack peptidoglycan in their cell walls and have unique lipids in their cell membranes. • Modern archaebacteria are thought to closely resemble early archaebacteria. • Chemical evidence indicates that archaebacteria and eubacteria diverged (separated)very early. Methanosarcina: an example of Archaebacteria Benagh

  3. The Evolution of Eukaryotes • Eukaryotes first appeared about 1.5 billion years ago. • Eukaryotic cells are much larger and more complex than prokaryotic cells, with a system of internal membranes (making organelles). • Most eukaryotes have mitochondria. • Chloroplasts are found in protists and plants. • Use Chlorophyll: a green pigment present in most plants • Protists were the first eukaryotic organisms—this is an evolutionary advance first seen in protists! Benagh

  4. Three Types of DNA • There can be up to three types of DNA in one Eukaryotic cell: • Eukaryotic nuclear DNA: inside the nucleus of the cell. • Mitochondria DNA: DNA in the mitochondria. Mitochondria are the size of prokaryotes. • Chloroplast DNA: DNA in the chloroplasts. Chloroplasts are also the size of DNA. Benagh

  5. The origins of Mitochondria and Chloroplasts • Most biologists think that mitochondria and chloroplasts originated as described by the theory of endosymbiosis. • Theory of Endosymbiosis: mitochondria are the descendants of symbiotic, aerobic eubacteria and chloroplasts are the descendants of symbiotic, photosynthetic eubacteria • Bacteria entered larger cells, and began to live inside the cell performing either cellular respiration or photosynthesis. Benagh

  6. Support for the Theory of Endosymbiosis • Size and Structure: Mitochondria and chloroplasts are the same size as bacteria. Both are surrounded by two membranes. Contain cytochromes. • Cytochromes: help with electron transport • Genetic Material: Mitochondria and chloroplasts have circular DNA similar to bacterial chromosomes. This DNA is different from the host cell nuclear DNA (DNA in the nucleus). • Ribosomes: Mitochondrial and chloroplast ribosomes are similar to bacterial ribosomes. • Reproduction: Like bacteria, chloroplasts and mitochondria reproduce by simple fission. This is independent of the host cell. Benagh

  7. Endosymbiosis and mutualism • The relationship between the large cell and the smaller contained cells in the theory of endosymbiosis is considered to be an example of mutualism. • Mutualism: a relationship between two species in which both species benefit. Benagh

  8. Mitochondrial DNA and inheritance • Mitochondrial DNA (mtDNA) can be useful in indicating close relatives, because the egg has mitochondria and the sperm does not. • This means all your mtDNA came from your mother, and all her mtDNA came from her mother. If your mother had other children, they have the same mtDNA as you! Benagh

  9. Other Organelles • The folding in the plasma (cell) membrane may have been the forerunner of both the endoplasmic reticulum and nuclear envelope based on similar structure and biochemical analysis. • Part of cell specialization: a process where cells become modified to perform specific functions in an organism. Benagh

  10. A singled celled protist Multicellularity • Protists were the first eukaryotes. Protists make up a large varied group of both multicellular and unicellular organisms. • Unicellular organisms are very successful, but each cell must carry out all the activities of the organism. • Distinct types of cells in one body can have specializedfunctions (like in your immune system, for example). • Almost every organism you can see without a microscope is multicellular. • Fossils of the first multicellular organisms are about 700 million years old. Multicellular protists—brown algae Benagh

  11. Origins of Modern Organisms • Most animal phyla that exist today probably originated during a relatively short time during the Precambrian and early Cambrian periods. • This rapid diversification is called the “Cambrian Explosion” • Many unusual marine animals appeared at this time. • A very rich collection of fossils found in a formation in Canada called the Burgess Shale. Benagh

  12. Mass Extinctions • The fossil record indicates that a sudden change occurred at the end of the Ordovican period—a large percentage of organisms became extinct. • Extinction: the death of all members of a species. • Mass Extinction: an episode during which large numbers of species becomes extinct. • Mass extinctions can allow new species to adapt and fill niches previously occupied by the now-extinct species, and thus help drive evolution. Benagh

  13. Continental Drift • Continental drift also played an important role in evolution. • Continental Drift: the movement of Earth's land masses over Earth’s surface through geologic time. Resulted in present-day position of the continents. • Helps to explain why there are a large number of marsupials in both Australia and South America, because these continents were once connected. Benagh

  14. The Ozone Layer • While the sun gives us the light energy Earth’s organisms need, it also produces dangerous ultraviolet (UV) radiation. • Early life lived in the sea, which protected it from dangerous UV radiation. • However, land organisms needed protection. • This protection is provided in the upper atmosphere by the ozone layer which blocks UV radiation. • The Ozone (O3—regular oxygen is O2layer formed about 2.5 billion years ago as cyanobacteria began adding oxygen to the earth’s atmosphere. Benagh

  15. Organisms on Land • Plants and Fungi: may have been the first multi-cellular organisms on land—also can have a mutualistic relationship. On land 430 million years ago. • Arthropods: organisms with hard outer skeletons, segmented bodies, and jointed limbs. Examples are insects, lobsters, and crabs. First animals on land. • Vertebrates • Fishes: First vertebrates, about 530 million years ago. Before organisms lived on land. • Amphibians: First vertebrates to inhabit the land, but still need to live near water. 370 million years ago. • Reptiles: Next vertebrates to live on land, better adapted to live on land than amphibians. Evolved from amphibians. Appeared 340 million years ago. • Mammals and Birds: After the extinction of the dinosaurs, small mammals and birds became the dominant land vertebrates. Radiated after the extinction of the dinosaurs (dominant reptiles) 65 million years ago. Benagh

  16. CHAPter13.1 The Theory of Evolution by Natural Selection Benagh

  17. Darwin, Mechanism for Evolution • The idea that life changes has been around for a long time, but now one really understood how that might happen. • In 1859, Darwin published evidence that species evolved, and proposed an explanation of how it might happen. • Before working as a naturalist, Darwin studied to be a physician and a minister. • In 1831, Darwin took a position as a naturalist on the voyage of the HMS Beagle. Benagh

  18. Science Before Darwin’s Voyage • In Darwin’s time most scientists thought each species was a divine creation that did not change. • However, scientists were trying to understand the origin of fossils. • Jean Baptiste Lamarck proposed that organisms change over generations because in the lifetime of an individual, physical features increased in size because of use or decreased because of disuse (Use Disuse Theory OR Inheritance of Acquired Characters). These changes are then passed on offspring. • This is NOT how it happens!!! Benagh

  19. Darwin’s Observations • On his voyage, Darwin found evidence challenging the belief that species do not change. • Darwin read Charles Lyell’s book Principles of Geology which proposed that the surface of Earth changed slowly over many years. • Darwin saw things that could be explained only by a process of gradual change. • In South America, he found fossils of extinct armadillos which were similar but not identical to modern armadillos in the area. • Darwin visited the Galápagos Island and noticed that the species on the islands were similar to those from South America, but they changed since they arrived. • Darwin called this Descent with modification, or evolution Benagh

  20. Growth of Populations • Population: all the individuals of a species that live in a specific geographical area and that can interbreed. • Evolution occurs on the level of the population!!! • Darwin finally understood how evolution happens when he read an essay by the English economist Thomas Malthus. • Malthus stated that unchecked populations grow by geometric progression, but that food supplies only increase by an arithmetic progression, so food can limit the potential growth of populations • Benagh

  21. Evolution by Natural Selection • Darwin realized Malthus’ applied to all species. • Every organism has the potential to produce many offspring during its lifetime. • In most cases, only a few survive to reproduce. • Individuals that have physical or behavioral traits that better suit their environment are more likely to survive and will reproduce more successfully than those without the traits. Benagh

  22. Evolution by Natural Selection • Darwin called this differential rate of reproduction Natural Selection. • In time, the number of individuals that carry inherited favorable characteristics will increase, and the population will change or evolve! • Organisms differ from place to place because their habitats are different, and each species has reacted to its own environment. • Adaptation: An inherited trait that has become common in a population because the trait provides a selective advantage. Benagh

  23. Publication of Darwin’s Work • Darwin waited a long time to publish his ideas about evolution and natural selection because he feared controversy. • He finally decided to publish his ideas after he received a letter and essay from Alfred Russel Wallace who also described evolution by natural selection. Benagh

  24. Darwin’s Theory • Darwin published “On the Origin of Species by Means of Natural Selection” in 1859. Many people were deeply disturbed by his assertion (made in a later book) that humans are related to apes. • Darwin’s theory of Natural selection is supported by four major points. Benagh

  25. Darwin’s Four Major Points • Inherited variation exists within the genes of every population or species (the result of random mutation and translation errors). • Or: Not every organism is identical! • In a particular environment, some individuals of a population or species are better suited to survive (as a result of variation) and have more offspring (natural selection). • Or: Some organisms do better and have more babies! • Over time, the traits that make certain individuals of a populations able to survive and reproduce tend to spread in that population. • Or: Organisms that do better give their advantages to those babies they had! • There is overwhelming evidence from fossils and many other sources that living species evolved from organisms that are extinct. Benagh

  26. Darwin’s Ideas Updated • Since Darwin’s work was published, his hypothesis (that natural selection explains how evolution happens) has been examined by biologists. • New discoveries have given scientists new insight into how natural selection brings about the evolution of species. Benagh

  27. Change Within Populations • Darwin’s ideas were based on the idea that in any population, individuals that are best suited to survive will produce the most offspring. These traits will become common new generations. • Scientists now know that genes are responsible for inherited traits. Certain forms of genes called alleles become more common. • In other words: natural selection causes the allele frequency to change. • Mutations and sexual reproduction provide the variation needed for natural selection. • Random gene mutation is essential to evolution! Benagh

  28. Species Formation • The environment varies—populations of the same species in different areas tend to evolve differently. • Reproductive Isolation: the condition in which two population of the same species do not breed with one another because of geographic separation, a difference in mating periods, or other barrier to reproduction. • As two isolated populations become more different over time, they may eventually not be able to mate, making them different species. Benagh

  29. The Tempo of Evolution • For decades, most biologists though of evolution as a gradual process that occurs continuously. However, some scientists suggested that species may stay unchanged for long periods of time and evolution occurs in spurts. These models are called: • Gradualism: the model of evolution in which gradual change occurs over a long period of time leading to species formation. • Punctuated Equilibrium: the model of evolution in which periods of rapid change in a species are separated by periods of little or no change. Benagh

  30. Chapter 13.2 Evidence of Evolution Benagh

  31. The Fossil Record • Fossils offer the most direct evidence that evolution takes place—fossils of animals show a pattern of development from ancestors to modern descendants. • Fossils provide a record of Earth’s past life-forms. • Evolution: Change over time. • Evolution can be observed in the fossil record. Benagh

  32. The Fossil Record • Darwin predicted that intermediate forms between organisms would be found. • Since this prediction, many of these intermediates have been discovered. • Intermediates (in-betweens) of fishes and amphibians, between reptiles and birds, and between reptiles and mammals have been found. Archeopteryx is a transitional or intermediate (in-between) form between reptiles and birds. Benagh

  33. The Fossil Record • Darwin’s theory is generally accepted by scientists as the best available explanation for biological diversity on Earth. • Based on a large body of supporting evidence, most scientists agree on these major points: • Earth is about 4.5 billion years old. • Why is this important? • Organisms have inhabited Earth for most of its history. • All organisms living today share a common ancestry with earlier, simpler life-forms. • How do we know this? Benagh

  34. Formation of Fossils • The fossil record is incomplete. • Fossils do not form in all environments. Organisms have to die under just the right conditions in order to be fossilized. • The fossil record will never be complete because not all organisms are fossilized. However, the record presents strong evidence that evolution has taken place. • Paleontologists: scientists who study fossils. • Paleontologists determine relative age of organisms and determine the order of fossils from oldest to youngest. • Fossils help scientists understand the geological time scale for all of the above reasons; without fossil evidence, we would not have as much evidence of the time needed for evolution to occur. Benagh

  35. Fossils and Populations • Fossils can provide important information regarding population structure and biogeography. • Biogeography: a science that deals with the geographical distribution of animals and plants. • Population: a group of organisms of the same species that live in a specific geographical area and interbreed. Benagh

  36. Anatomy and Development • Comparisons of anatomy of different types of organisms often reveal basic similarities in body structures even though the function may differ between organisms. • Vestigial Structure: a structure in an organism that is reduced in size and function and that may have been complete and functional in the organism’s ancestors. • Similarities in bone structure can be seen in vertebrates, suggesting they have a relatively recent common ancestor • Homologous Structures: structures that share a common ancestry. Similar structure in two organisms can be found in the common ancestor of the organisms. Example: human arm, monkey arm • Analogous Structures: are features of different species that are similar in function but not necessarily in structure and which do not derive from a common ancestral feature (compare to homologous structures) and which evolved in response to a similar environmental challenge. Example: bird wing, insect wing • Evolutionary history of organisms is also seen in the development of embryos. The stages of embryonic development are similar in many species. Benagh

  37. Anatomy and Development Benagh

  38. Homologous Structures Benagh

  39. Biological Molecules • The picture of successive change seen in the fossil record allows scientists to make a prediction that can be tested. • If species have changed as seen in fossils, then genes should also have changed. • Changes in a gene’s nucleotides should build up over time. Benagh

  40. Proteins • Amino acid sequences of similar proteins were compared. • If evolution has taken place, then species descended from a recent common ancestor should have fewer amino acid differences in proteins than do species that aren’t as closely related. Benagh

  41. DNA Sequence • This pattern does not hold true for all proteins. A certain protein may evolve more rapidly in some groups than others. • Comparisons of proteins may not reflect evolutionary relationships supported by the fossil record and other evidence. • More accurate hypotheses about evolutionary histories are based on large numbers of gene sequences. • These evolutionary histories based on DNA sequences tend to be similar to those from the fossil record. Benagh

  42. Chapter 13.3 Examples of Evolution Benagh

  43. Natural Selection at Work • How does evolution occur? • Darwin’s theory asserts that natural selection is the mechanism that drives evolution, meaning that natural selection is what makes it happen. • If an organism has a trait that makes it easier to survive and reproduce, that trait will become more common in the population. • The environment dictates the direction and amount of change. • If the environment changes, the set of characteristics that most help an individual reproduce may change. • Example: Polar Bear’s fur Benagh

  44. Factors in Natural Selection • All populations have genetic variation. • Populations have individuals who are slightly different from one another in genetic makeup. • The environment presents challenges to successful reproduction. • An organism that does not survive to reproduce cannot pass on its genes. • Individuals tend to produce more offspring than the environment can support. • Individuals of a population often compete with one another to survive. • Individuals that are better able to cope with the challenges presented by their environment tend to leave more offspring than those individuals less suited to the environmental do. Benagh

  45. Examples of Natural Selection • Tuberculosis (TB) is caused by the bacterial species M. tuberculosis and kills more adults than any other infectious disease in the world. • Two effective antibiotics became available to fight this bacteria. • However, in the late 1980s, new strains of Tuberculosis that are resistant to the antibiotics appeared. • These resistant bacteria evolved through natural selection. Benagh

  46. Evolution of Antibiotic Resistance • A mutation probably occurred in a single Tuberculosis cell, which allowed that cell to survive exposure to normally deadly antibiotics. • Normal bacteria cells die from antibiotics while the mutated bacteria continue to survive and grow. • Eventually, there could be enough mutated bacteria to kill the host and spread to other individuals. Benagh

  47. Evolution in Darwin’s Finches • Darwin collected 9 species of finches from three of the Galápagos Islands. All of these finches were similar to each other except for their bills. • Two crushed seeds, one picked at fruit, one ate insects, one drank the blood of other birds, etc. All of the finches had beaks adapted for these various tasks. • Darwin suggested that these species evolved from an original ancestral species. • This is known as adaptive radiation. • Adaptive Radiation: Diversification of a species or single ancestral type into several forms that are each adaptively specialized to specific environmental conditions. Benagh

  48. Evolution in Darwin’s Finches • During dry years, plants produce few seeds. • The difference between survival and starvation is the ability to eat the larger, tougher seeds. • After several dry years, the birds that had longer, more-massive beaks had better success and produced more offspring. • When wet seasons returned, smaller beaked birds were more common. • The numbers of birds with different beak shapes are changed by natural selection in response to the available food supply. • Natural selection does not CAUSE change; rather it selects genes that are already present and most adaptive to the environment. The trait must be present and provide advantage for survival and reproduction. Benagh

  49. Gene Pools • Natural selection utilized the diversity in a species’ gene pool. • Gene Pool: The total number of genes of every individual in an interbreeding population. • Gene pools contain variations in genes, relative gene frequencies, and allele frequencies. Genetic recombination can influence the gene pool and variation. • Variations: A modification in structure, form, or function. • Relative Frequency: the average number of occurrences of a particular event in a large number of repeated trials. • Allele Frequency: the frequency of an allele compared to other alleles of the same gene in a population. • Natural selection makes the most successful alleles (different copies of genes) most common in a population. • In this way, natural selection changes the POPULATION, not the INDIVIDUALS! Benagh

  50. Formation of New Species (Speciation) • Species formation occurs in stages. • A species molded by natural selection has an improved “fit” to its environment. • Divergence: The accumulation of differences between groups. • Divergent (split apart) Evolution: The process by which an interbreeding population diverges (splits) into two or more descendant species, resulting in once similar or related species to become more and more different. • Convergent (come together) Evolution: A kind of evolution wherein organisms evolve parts that have similar structures or functions in spite of their evolutionary ancestors being very dissimilar or unrelated. • Speciation: The process by which new species form. Benagh The body structure of these organisms are examples of convergent evolution. Benagh