Evolution S. Livingstone 2010
I. History of Life on Earth
I. History of Life A. Early History of Earth I. Early earth was inhospitable hot, with many volcanoes little free oxygen and lots of carbon dioxide other gases present: nitrogen, methane, ammonia, hydrogen and water vapor
I. History of Life B. History in Rocks Fossils are clues to the past Any trace of a species that once lived can infer the structure of the organisms, what they ate, what ate them, and the environment that they lived in Paleontologists- detectives to the past scientists who collect, study and classify fossils
I. History of Life Fossils occur in sedimentary rock sedimentary rock is formed when exposure to rain, heat, wind and cold breaks down existing rock into small particles of sand, silt and clay. The particles are carried by streams and rivers into lakes or seas where they eventually settle to the bottom. As layers of sediment build up over time, dead organism may also sink to the bottom and become buried. The weight of layers of sediment gradually compresses the lower layers and along with chemical activity, turns into rock
I. History of Life Non-rock fossils Fossils can be found in ice Ex. Woolly Mammoth preserved in ice Fossils can be found in amber Organisms preserved in amber Amber is a form of tree resin exuded as a protective mechanism against disease and insect infestation that has hardened and been preserved in the earth s crust for millions of years
I. History of Life C. Age of a fossil Relative Dating oldest fossils are in deepest layers paleontologists can compare fossils with that of older fossils
C. Age of a Fossil Radiometric Dating I. History of Life Use of radioactive isotopes in rocks to date fossils The technology of radiometric dating provides evidence that the earth is at least 4.5 billion years old Certain elements convert to other elements at known rates, which can be measured, thus revealing the age of the specimen One half Potassium40 decays to Argon40 in about 1.3 billion years Carbon 14 decays to half of its original amount in 5730 years
Common Isotopes used to date Geologic Materials Parent Daughter T (1/2) Useful range Type of material 238 U 206 Pb 4.47 b.y >10 millions Igneous & 235 U 207 Pb 707 m.y sometimes metamorphic 232Th 208Pb 14 b.y rocks and minerals 40 K 40Ar & 40Ca 1.28 b.y >10,000 years 87 Rb 87Sr 48 b.y >10 million years 147Sm 143Nd 106 b.y 14 C 14 N 5,730 y 100-70,000 years Organic material
Bacteria were the earliest life Formed colonies called stromatolites (age 3.5 billion years old) Best colonies in Australia
Era Period Million Years Ago Major Events Major Life Forms Precambrian 3500 Life evolves Photosynthetic bacteria 3000 Prokaryotes 2000 Eukaryotes Paleozoic Cambrian 540 Invertebrates Ordovician 510 First Invertebrates Silurian 439 First land plants Devonian 408 First Amphibians Carbonifero us 362 First reptile Permian 290 Conifers dominant Mesozoic Triassic 245 First dinosaurs First mammals Jurassic 208 First birds First flowering plants Cretaceous 146 Dominant flowering plants Cenozoic Tertiary 66 Quaternary 1.8 Humans
II. Origins of Life
II. Origins of Life A. Origins: The Early Ideas Spontaneous generation non-living material can produce life Disproved by Redi experiment meat and maggots
II. Origins of Life Disproved by Pasteur S flask experiment boils broth in S flask broth is free of microorganisms for a year removes curved neck broth is teeming with microorganisms Biogenesis living comes from living things.
II. Origins of Life B. Modern Ideas Oparin suggested sun, lightning, and molecules such as water vapor, carbon dioxide, nitrogen, methane and ammonia formed a primordial soup that was the beginning of simple organic molecules
II. Origins of Life Miller and Urey 1953-1954 Tried to answer the question by simulating conditions on the early Earth Filled flask with hydrogen, ammonia, methane, and water = atmosphere They passed electric sparks through the mixture to simulate lightning Within a few days amino acids were present the building blocks of protein
II. Origins of Life
II. Origins of Life Sidney Fox showed how sort chains of amino acids could cluster to form protocells Experiments like Miller and Urey s are currently studied at major universities (i.e. Georgia Tech, U Michigan
II. Origins of Life C. Evolution of Cells (based on fossil record) First true cells were probably prokaryotic, heterotrophic and anaerobic single celled no nucleus consumed food for energy did not need oxygen to survive Then came chemosynthetic organisms Then autotrophs were probably archaebacteria that live in harsh environments Next came photosynthetic prokaryotes releases oxygen into atmosphere
II. Origins of Life Endosymbiotic theory Proposes that eukaryotic cells arose from living communities formed by prokaryotic organisms Lynn Margulis of Boston University
II. Origins of Life Endosymbiotic Theory Explained: Mitochondria and chloroplasts contain DNA similar to bacterial DNA. Mitochondria and chloroplasts have ribosomes whose size and structure resemble those of bacteria Like bacteria, mitochondria and chloroplasts reproduce through binary fission Eukaryotic cells evolved from prokaryotic cells
Endosymbiotic Theory ENDO = Into Symbiosis = relationship of two organisms living close together According to the theory of endosymbiosis eukaryotic cells evolved when aerobic eubacteria either infected or were engulfed by a larger host cell and later established a symbiotic relationship
III. Natural Selection and Evidence for Evolution
History of the Theory of Evolution Darwin s Role http://evolution.berkeley.ed u/evosite/history/index.sht ml
III. Natural Selection and Evidence for Evolution A. Charles Darwin credited with the Theory of Evolution Scientists, including Darwin, used fossils to explain that organisms have changed over time Darwin and HMS Beagle At age 22, Darwin sailed around the world, trip took 5 years Ship s naturalist he collected specimens and note of the diversity he saw
Galapagos Islands
III. Natural Selection and Evidence for Evolution Darwin in the Galapagos Group of islands off the coast of South America Noted that the animals were unique but similar to the species he had seen elsewhere Giant tortoises had differences in shell depending on which island they inhabited Marine iguanas could swim and eat algae Finches had many different size beaks depending on the type of food they ate
III. Natural Selection and Evidence for Evolution Darwin Continues his Studies Lamarck proposed a theory about evolution in the year Darwin was born called Use and Disuse Theory Proposed that by selective use or disuse of organs, organisms acquired or lost certain traits during their lifetime These acquired traits then could be passed on to their offspring
III. Natural Selection and Evidence for Evolution How do we know Lamarck s explanation is false?
III. Natural Selection and Evidence for Evolution Darwin continued to look for explanations to evolution for the next 22 years He read about Thomas Malthus study which stated that the human population grows faster than the earth s food supply Darwin applied this idea to all of life
III. Natural Selection and Evidence for Evolution Darwin also gained insight by breeding pigeons using artificial selection Breeders determine which individuals to use for breeding based on the natural variation Are able to produce a wide range of plants and animals that looked very different from their ancestors
III. Natural Selection and Evidence for Evolution Darwin Explains Natural Selection Natural selection is a mechanism that occurs when organisms with certain variations survive, reproduce and pass on their variations to the next generation At this time, Wallace also reached similar conclusion
III. Natural Selection and Evidence for Evolution Darwin wrote a book, On the Origin of Species which today is still a unifying theme of biology There is variation among population There is an overproduction of offspring There is a struggle for survival, competition for food and shelter The fittest survive and reproduce Heritable variations are passed onto offspring Giving way to decent with modification
III. Natural Selection and Evidence for Evolution Interpreting Evidence After Darwin Modern biologists define evolution as any change in the gene pool of a population gene pool is the combined genetic information of all the members of a population
III. Natural Selection and Evidence for Evolution B. Three Types of Natural Selection Directional Selection Favors individuals possessing extreme values of a trait, which causes the population to move in a particular direction If a climate becomes colder, a population may evolve in a consistent direction in response thicker fur
Directional Selection # of Individuals Phenotypic Range Shift towards ONE extreme
III. Natural Selection and Evidence for Evolution Stabilizing Selection Acts against individuals who deviate too far from the average, favors the average Sizes in lizards: large lizards may be subject to predation; small lizards may have a hard time defending territories, natural selection favors the average
Stabilizing Selection # of Individuals Phenotypic Range Shift towards middle
III. Natural Selection and Evidence for Evolution Disruptive Selection Adapts individuals in a population to different habitats. Similar to directional selection but it favors either extreme May occur in an area that provides very different resources
III. Natural Selection and Evidence for Evolution Galapagos finches had a variety of food choices: smaller birds fed on small seeds, larger birds feed on large seeds. Natural selection favors both but not the average who would compete for both resources.
Disruptive Selection # of Individuals Phenotypic Range Shift towards both extremes
III. Natural Selection and Evidence for Evolution C. EVIDENCE FOR EVOLUTION
III. Natural Selection and Evidence for Evolution Fossil evidence Not all species existed at the same time Fossil record is fully consistent with the prediction that more derived groups should appear over time in the fossil record There has not been a single case of a species out of order no mammals mixed in the rock with early fish
III. Natural Selection and Evidence for Evolution
III. Natural Selection and Evidence for Evolution Fossil evidence Life began in the sea. The oldest fossils are marine
Burgess Shale: 505 Million Year Old Coral Reef
III. Natural Selection and Evidence for Evolution Fossil Evidence Transitions between major groups (classes) of species Fish amphibians (transition from ray-finned fish to tetrapods (vertebrate with 4 limbs)). Reptiles birds (Archaeopteryx) Reptiles mammals (synapsid reptiles (therapsids) have very mammalian characteristics
The London Specimen and a reconstruction of Archaeopteryx (from Levin, 1996)
III. Natural Selection and Evidence for Evolution Fossil Evidence Transitions between classes (ex. Orders of mammals) Gradual loss of legs
Leg bones become smaller and smaller in more recent whales Modern whales have remnants of their ancestral hind legs
III. Natural Selection and Evidence for Evolution Fossil Evidence Well preserved family groups (horse family)
III. Natural Selection and Evidence for Evolution Fossil Evidence Well preserved communities of species that no longer exist but resemble modern species. (Rancha LeBrea Tar Pits, Los Angeles 25,000 years ago)
III. Natural Selection and Evidence for Evolution Biogeographical Species that existed in the past are fossilized in areas where species that resemble them are living now Geographic Distribution organisms that live under similar ecological conditions are exposed to similar pressures of natural selection Because of similar selection pressures, different animals end up evolving certain striking features in common
III. Natural Selection and Evidence for Evolution Adaptations: gradual change in an organism that enables it to survive in a particular environment. Types Structural Behavioral Physiological
III. Natural Selection and Evidence for Evolution Structural Structural adaptations are physical features of an organism like the bill on a bird, the fur on a bear, stinging cells of jellyfish or sticky tongue of an anteater
II. Natural Selection and Evidence for Evolution Structural adaptations homologous structures (HSS) structures that have different mature forms in different organisms but develop from the same embryonic tissue exist among related groups, providing support for having a common ancestor
Highly complex anatomical structures have evolved from simple structures that served the same purpose: ex: different kinds of eyes
III. Natural Selection and Evidence for Evolution Structural Adaptations: analogous structures (ASF) outwardly similar structures
III. Natural Selection and Evidence for Evolution Structural Adaptations: vestigial structures (NF) structure that serves no useful function in an organism (A) Whales have pelvic bones floating in their abdominal cavity
Vestigial Structures (B) Pelvic bones in pythons are unused remnants from their common ancestor shared with lizards We would not expect to see these structures if snakes had an origin separate from other vertebrate animals. (c) Blind salamanders have eyes with retinas and lenses, yet the eyelids grow over the eye, sealing them from outside light
Vestigial Structures (D) Flightless Cormorant Wings: Cormoront lives on Galapagos Islands, & has wings too small for flight (E) Legless Skinks a type of lizard. In some species the legs have become vestigial. (so reduced that they no longer function)
Human Vestigial Structures Humans have > 100 vestigial structures. 90% develop wisdom teeth (molars used for chewing & grinding plant material) which usually don t erupt from gums, can be malformed and cause pain. Tailbone (Coccyx) fused vertebrae that in other vertebrates are tails. It serves no purpose. Ear muscles used in other vertebrates for twitching Appendix part of digestive tract used to digest tough plant material is so reduced in humans that it is dysfunctional
III. Natural Selection and Evidence for Evolution Adaptations Behavioral Behavioral adaptations are the things organisms do to survive. For example, bird calls and migration are behavioral adaptations.
III. Natural Selection and Evidence for Evolution Adaptations Physiological A metabolic adjustment within the cell, or tissues of an organism in response to an environmental stimulus, resulting in the improved ability of that organism to cope with its changing environment. Physiological adaptations can develop rapidly digestive enzymes hemoglobin bioluminescence
III. Natural Selection and Evidence for Evolution Embryological Evidence during the early stages of development many animals with backbones are so similar that they can be hard to tell apart embryonic development shows that the same group of embryonic cells develop in the same order and in similar patterns to produce tissues and organs of all vertebrates
III. Natural Selection and Evidence for Evolution Molecular/biochemical evidence Fields unknown during Darwin s time support predictions made from his theory and provide independent evidence that is congruent with the fossil record All organisms share the same genetic code which code for amino acids that make up proteins Ex. DNA, ATP, proteins
III. Natural Selection and Evidence for Evolution Molecular/biochemical evidence Mutations that help an organism survive its environment are passed on to the next generation. Species that diverged longer ago have more differences in their corresponding proteins. (just like comparing how closely related two humans are, one can compare how related different species are.
Flagella-- http://www.millerandlevine.com/km/e vol/design2/article.html
IV. Mechanisms of Evolution
IV. Mechanisms of Evolution A. Population Genetics POPULATIONS, not individuals, EVOLVE Gene pool all of alleles of population s genes Allelic (gene) frequency--% of specific allele in gene pool Genetic equilibrium gene frequency remains constant over many generations (not evolving)
IV. Mechanisms of Evolution Changes in Genetic Equilibrium Mechanisms for genetic change 1. Mutation environmental factors or chance 2. Sexual reproduction 3. Gene flow when individuals enter or leave a population Immigration -individuals moving INTO a population Emmigration -individuals moving OUT of a population 4. Natural selection is the most significant factor to cause change in a gene pool
IV. Mechanisms of Evolution Example of Gene Flow Genetic drift occurs in small populations that become isolated like animals in the Galapagos In each generation, some individuals may, just by chance, leave behind a few more descendents (and genes, of course!) than other individuals. The genes of the next generation will be the genes of the lucky individuals, not necessarily the healthier or better individuals. It happens to ALL populations there s no avoiding the vagaries of chance.
IV. Mechanisms of Evolution Genetic drift can cause big losses of genetic variation for small populations. Examples: Bottleneck Populations and Founder Effect Population bottlenecks occur when a population s size is reduced for at least one generation.
Reduced genetic variation means that the population may not be able to adapt to new selection pressures, such as climatic change or a shift in available resources, because the genetic variation that selection would act on may have already drifted out of the population.
An example of a bottleneck Northern elephant seals have reduced genetic variation probably because of a population bottleneck humans inflicted on them in the 1890s. Hunting reduced their population size to as few as 20 individuals at the end of the 19th century. Their population has since rebounded to over 30,000 but their genes still carry the marks of this bottleneck: they have much less genetic variation than a population of southern elephant seals that was not so intensely hunted.
IV. Mechanisms of Evolution Founder effect A founder effect occurs when a new colony is started by a few members of the original population. This small population size means that the colony may have: reduced genetic variation from the original population. a non-random sample of the genes in the original population.
Example of Founder Effect For example, the Afrikaner population of Dutch settlers in South Africa is descended mainly from a few colonists. Today, the Afrikaner population has an unusually high frequency of the gene that causes Huntington s disease, because those original Dutch colonists just happened to carry that gene with unusually high frequency. This effect is easy to recognize in genetic diseases, but of course, the frequencies of all sorts of genes are affected by founder events.
V. Evolution of Species--Speciation
V. Evolution of Species--Speciation Add this! Species: a group of organisms with a common gene pool that is reproductively isolated from other organisms Isolating mechanism: factors that restrict gene flow between species and sometimes different populations within a species
V. Evolution of Species--Speciation A. Allopatric Speciation geographic barrier physically isolates populations of a species which blocks gene flow once isolated allopatric populations (living in different places) accumulate genetic differences due to natural selection, genetic drift, and new mutations removing the geographic barrier---the following could happen: 1. meld together by allele flow and 2. recombination once again to form a single species; 3. remain reproductively isolated pre-mating or post-mating isolating mechanisms-- different types of reproductive isolation
Example of Allopatric Speciation island chains frequently produce new species; provide geographic barriers that facilitate invasion and re-invasion by different species; this is the probable mechanisms for the proliferation of Darwin's finches on the Galapagos Islands; Hawaiian Islands once supported thousands of speices of Drosophilia flies that probably evolved by a similar mechanism
V. Evolution of Species--Speciation B. Sympatric speciation (does not involve a geographic barrier) results from intrinsic factors such as chromosomal changes and non-random mating become genetically isolated even though their ranges overlap ex. polyploidy, non-random mating change in Chromosome Numbers and Speciation Ex. Polyploidy more than a normal set of chromosomes.
V. Evolution of Species--Speciation C. Reproductive Isolation interbreeding organisms can no longer mate and produce fertile offspring Genetic material very different so fertilization doesn t occur Behavioral mating at different times of day/month/year Different pheromones Mechanical physical differences prevent mating between species
VII. Pacing of Evolution
VII. Pacing of Evolution Gradualism fossil evidence shows this Explanation that evolution involves a slow and steady accumulation of changes over a period of time Punctuated equilibrium occurs relatively quickly, in rapid bursts, with long periods of genetic equilibrium in between Pattern of long, stable periods of stasis (no change) interrupted by brief periods of rapid evolution
VIII. Patterns of Evolution
VIII. Patterns of Evolution A. Convergent Evolution Two different species develop similar adaptations because they live in similar environments For example ability to move through the water rapidly shark (fish), penguin (bird), and dolphin (mammal)
Species evolve to fill niches Mutations occur randomly in geographically distinct populations Natural selection allows the mutations that work to become adaptations
VIII. Patterns of Evolution B. Divergent Evolution Occurs when a population becomes isolated from the rest of the species and begins to follow a different evolutionary course often results in adaptive radiation associated with the opening up of a new biological frontier For example Darwin s finches which had different beak lengths
Examples of Divergent Evolution
Example of Adaptive Radiation (divergence into an abundance of available niches)
VIII. Patterns of Evolution C. Coevolution Two different species evolved at the same time because of a beneficial relationship between the two groups
IX. Primate Adaptation and Evolution Primate a group of mammals that include lemurs, monkeys, apes and humans Most are arboreal (live in trees) Binocular vision Opposable thumbs Flexible joints Fossils indicate that they appeared on earth 60-70 million years ago Major trends increasing brain size and walking upright
X. Human Ancestry Earliest Hominids Australopithecine fossils from Africa 5-8 million years ago Bipedal and climbed trees Brain and body size increased and jaws and teeth decreased in size Stone Tools and genus homo Appeared 2 million years ago Use of fire, language, and culture developed
Embryological development matches the progression of fossils in the fossil record Embryological Present & past distribution of continents explains the distribution of fossils Fossil Record Mutations exhibited in bacteria provide concrete evidence for the changes that lead to the branching of species observed in the fossil record Vertebrates not only repeat the development of ancestral vertebrate but they have similar bone structure and unused remnants of their structures Anatomical Amino acid sequences are more similar in species with more similar bone structures. Biogeography Molecular
Mistakes during DNA REPLICATION cause MUTATIONS Add variations to GENE POOL ADAPTATIONS NATURAL SELECTION
Direct Evidence (microevolution) Evolution Before Our Very Eyes 1. Selective Breeding 2. Industrial melanism. 3. Antibiotic resistant bacteria 4. Herbicide resistant weeds. 5. Annual changes in influenza viruses 6. Pesticide Resistant Insects 7. Resistance to anti viral medicines (HIV)