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![Microevolution
• Changes in a population’s gene pool over time.
– Genetic variability within a population is the catalyst
• Four Processes cause Microevolution
– Mutation (random changes in DNA—ultimate source of
new alleles) [stop little]
• Exposure to mutagens or random mistakes in copying
• Random/unpredictable relatively rare
– Natural Selection (best produce most offspring)
– Gene flow (movement of genes between pop’s)
– Genetic drift (change in gene pool due to random/chance
events)
• Peppered moth of England; El Nino Galapagos](https://image.slidesharecdn.com/evolutionsemiv-200429113345/75/EVOLUTION-THE-HISTORY-8-2048.jpg)
Uploaded byDr Dasari Prasanna
EVOLUTION THE HISTORY
The document discusses various theories and concepts related to evolution, including Darwinism, microevolution, macroevolution, and neo-Lamarckism, highlighting the roles of natural selection, genetic variation, and reproductive isolation. Evidence supporting evolution is presented through fossil records, comparative anatomy, and molecular biology, demonstrating mechanisms like adaptive radiation and speciation. Additionally, it addresses extinction, emphasizing human impacts on biodiversity and the potential for a sixth mass extinction due to habitat loss and environmental changes.
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EVOLUTION THE HISTORY
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- 3. USE AND DISUSETHEORY : INTERNAL URGE , DEVELOPMENT OF NEW ORGANS INHERITANCE OF ACQUIRED CHARACTERS OBJECTIONS: 1.AUGUST WEISMANN EXPERIMENT WITH RATS 2.ABSENCE OF MUSCLES IN SPORT PERSON CHILDREN 3. MAKING PERFORATION IN EAR PINNA NEO LAMARCKISM : COPE, OSBORN, PACKARD, SPENCER – SCIENTIFIC APPROACH 1. ADAPTATIONS ARE UNIVERSAL PAUL KAMMARER OBSERVED DEVELOPMENT OF NORMAL EYES AND SKIN COLOUR IN PROTEUS ANGUINUS. LAMARKISM
- 6. • Darwin observedthe Galapagos finches while traveling on the H.M.S Beagle.
- 7. Evolution • The changein a POPULATION’S genetic makeup (gene pool) over time (successive generations) – Those with the best phenotype and genotype survive to reproduce and pass on traits – All species descended from earlier ancestor species • Microevolution – Small genetic changes in a population such as the spread of a mutation or the change in the frequency of a single allele due to selection (changes to gene pool) – Not possible without genetic variability in a pop… • Macroevolution – Long term large scale evolutionary changes through which new species are formed and others are lost through extinction
- 8. Microevolution • Changes ina population’s gene pool over time. – Genetic variability within a population is the catalyst • Four Processes cause Microevolution – Mutation (random changes in DNA—ultimate source of new alleles) [stop little] • Exposure to mutagens or random mistakes in copying • Random/unpredictable relatively rare – Natural Selection (best produce most offspring) – Gene flow (movement of genes between pop’s) – Genetic drift (change in gene pool due to random/chance events) • Peppered moth of England; El Nino Galapagos
- 9. Darwinian Natural Selection •Three conditions necessary for evolution by natural selection to occur: – Natural variability for a trait in a population – Trait must be heritable (has a genetic basis so that it can be passed onto offspring) – Trait must lead to differential reproduction – Must allow some members of the population to leave more offspring than other members of the population w/o trait) • A heritable trait that enables organisms to survive is called an adaptation (Lamark is wrong…)
- 10. DARWINISM 1. PRODIGALITY OFPRODUCTION OR OVER PRODUCTION 2. CONSTANT IN POPULATION 3. STRUGGLE FOR EXISTENCE - INTRASPECIFIC, INTER SPECIFIC, STRUGGLE WITH ENVIRONMENT 4. VATIATIONS 5. NATURAL SELECTION OR SURVIVAL OF THE FITTEST 6. ORIGIN OF SPECIES CRITICISM & OBJECTIONS TO DARWINISM NEODARWINISM
- 12. Darwinian Natural Selection nThree conditions necessary for evolution by natural selection to occur: – Natural variability for a trait in a population – Trait must be heritable (has a genetic basis so that it can be passed onto offspring) – Trait must lead to differential reproduction – Must allow some members of the population to leave more offspring than other members of the population w/o trait) n A heritable trait that enables organisms to survive is called an adaptation.
- 13. The Case ofthe Peppered Moths n Industrial revolution – Pollution darkened tree trunks n Camouflage of moths increases survival from predators n Directional selection caused a shift away from light-gray towards dark-gray moths
- 17. EVIDENCES FROM PALAEONTOLOGY Studyof prehistoric life through fossils moulds, casts, petrifactions, coprolites. Geologists arranged fossils in a chronological sequence or the history of evolution in the form of geological time scale. Eras Periods Epoch Archaeozoic – Ancient primitive life Proterozoic – Era of former life Palaeozoic – Era of Ancient life Mesozoic – Age of reptiles coenozoic – Age of mammals
- 21. EVIDENCES FROM COMPARATIVE ANATOMY •HOMOLOOUS ORGANS – ADAPTIVE RADIATION OR DIVERGENT EVOLUTION • ANALOGOUS ORGANS – CONVERGENT EVOLUTION • VESTIGIAL ORGANS • ATAVISTIC ORGANS • CONNECTING LINKS
- 26. • Convergent Evolution:Similar evolved structures in unrelated animals. Copyright © 2010 Ryan P. Murphy
- 29. EVIDENCES FROM CELLAND MOLECULAR BIOLOGY • SEROLOGICAL TESTS – H.F. NUTTEL • BIOCHEMICAL RECCAPITULATIONS - EXCRETA
- 37. FORCES OF EVOLUTION MUTATIONS- ULTIMATE SOURCE OF MUTATION, SPONTANEOUS, SOMATIC, GERM LINE GENE FLOW – EXCHANGE OF GENESBETWEEN POPULATIONS GENETIC DRIFT – SUDDEN CHANGES IN FREQUENCIES, SMALL POPULATIONS SELCTION – FORMS ADAPTIVE EVOLUTIONARY CHANGES
- 38. Gene Flow andGenetic Drift • Gene Flow – Flow of alleles • Emigration and immigration of individuals • Genetic Drift – Random change in allele frequencies over generations brought about by chance – In the absence of other forces, drift leads to loss of genetic diversity
- 44. NATURAL SELECTION 1. DIRECTIONALSELECTION – ex: INDUSTRIAL MELANISM, RESISTANCE TO DDT 2. STABILIZING SELECTION - ex: HUMAN BIRTH WEIGHT MORTALITY RATE 3. DISRUPTIVE SELECTION - ex: BLACK AND WHITE COAT RABBITS
- 45. Directional Selection Natural selection New averagePrevious average Numberofindividuals Coloration of snails Individuals from one side of distribution reproduce Population Looks Different Over Time—Mean changes (e.g., peppered moths) Numberofindividuals Snail coloration best adapted to conditions Average Coloration of snails Average shifts
- 46. Stabilizing Selection Coloration ofsnails Light snails eliminated Dark snails eliminated Numberofindividuals Coloration of snails Snails with extreme coloration are eliminated Numberofindividuals Average remains the same Number of individuals with intermediate coloration increases Eliminates Fringe Individuals Natural selection
- 47. Diversifying Selection Environment favorsextreme uncommon Individuals Greatly reduces those with average traits Coloration of snails Numberofindividuals Snails with light and dark colors dominate Coloration of snails Numberofindividuals Light coloration is favored Dark coloration is favored Intermediate-colored snails are selected against Natural selection
- 48. ISOLATION Reproductive isolation isthe Segregation or separation of population by certain barriers is called as isolation.
- 49. Reproductive Isolating Mechanisms •Any heritable feature of body, form, functioning or behavior that prevents breeding between one or more genetically divergent populations • Pre zygotic Isolation • Post zygotic Isolation
- 50. Pre mating/Pre-Zygotic Isolatingmechanisms Mating or zygote formation is blocked – stops interbreeding among the population. • Temporal Isolation – different species do not mate. Ex – different frog species in same pond • Behavioral Isolation – potential mates meet – selection of mate Ex – some crickets are morphologically same but respond to species specific mating song. • Mechanical Isolation – copulation is attempted but transfer of sperm does not takes place • Ecological Isolation – bush insects have distinctly shaped genitalia that will only other members of the same species • habitat isolation – Ex: Tiger and Lion don’t mate but in capture can do successfully forms Tiglon. • Geographical or spatial isolation – Allopatric species (separate species)
- 51. Post Mating /PostZygotic Isolating Mechanisms Gametic incompatibility, hybrid inviability or sterility. • Gametic incompatibility – sperm transfer takes place but zygote is not formed. Ex. Sea urchins • Zygotic mortality- egg is fertilized, but zygote does not develop. Ex: plants • Hybrid inviability – hybrid embryo develops but reduced variability Ex- Goat and Sheep • Hybrid sterility- hybrid is viable but adult is sterile. Ex: horse and Donkey results in Mule • Hybrid breakdown- first generation are viable but F2 are inviable or sterile. Ex: in plants
- 52. Temporal Isolation inApple Maggots
- 54. Post-Zygotic Isolation • Hybridsdon’t work – Zygotic mortality - Egg is fertilized but zygote or embryo dies – Hybrid inviability - First generation hybrid forms but shows low fitness – Hybrid infertility - Hybrid is fully or partially sterile
- 55. Speciation • Two speciesarise from one – Requires Reproductive isolation • Geographic: Physically separated • Temporal: Mate at different times • Behavioral: Bird calls / mating rituals • Anatomical: Picture a mouse and an elephant hooking up • Genetic Inviability: Mules • Allopatric – Speciation that occurs when 2 or more populations of a species are geographically isolated from one another – The allele frequencies in these populations change – Members become so different that that can no longer interbreed • Sympatric – Populations evolve with overlapping ranges – Behavioral barrier or hybridization or polyploidy
- 56. Speciation Adapted to heat throughlightweight fur and long ears, legs, and nose, which give off more heat. Adapted to cold through heavier fur, short ears, short legs, short nose. White fur matches snow for camouflage. Gray Fox Arctic Fox Different environmental conditions lead to different selective pressures and evolution into two different species. Spreads northward and southward and separates Southern population Northern population Early fox population
- 57. Copyright © 2010Ryan P. Murphy
- 60. Allopatric Speciation • Physicalbarrier prevents gene flow between populations of a species – Archipelago hotbed of speciation
- 61. Allopatric Speciation • Newarrival in species – Poor habitats on an isolated archipelago – Start of allopatric speciation Hawaiian Honeycreepers
- 62. Sympatric Speciation • Newspecies forms within home range – Polyploidy leads to speciation in plants – Self-fertilization and asexual reproduction
- 63. Extinction • The ultimatefate of all species just as death is for all individual organisms • 99.9% of all the species that have ever existed are now extinct – To a very close approximation, all species are extinct • Background vs. Mass Extinction – Low rate vs. 25-90% of total – Five great mass extinctions in which numerous new species (including mammals) evolved to fill new or vacated niches in changed environments – 10 million years or more for adaptive radiations to rebuild biological diversity following a mass extinction
- 64. Extinction in thecontext of Evolution • If the environment changes rapidly, • The species living in these environments do not possess genes which enable survival in the face of such change & • Random mutations do not accumulate quickly • All members of the unlucky species may die.
- 65. Ordovician: 50% of animalfamilies, Devonian: 30% of animal families, Permian: 90% of animal families, including over 95% of marine species; many trees, amphibians, most bryozoans and brachiopods, all trilobites. Triassic: 35% of animal families, including many reptiles and marine mollusks. Cretaceous: up to 80% of ruling reptiles (dinosaurs); many marine species including many foraminiferans and mollusks. Current extinction crisis caused by human activities. Species and families experiencing mass extinction Bar width represents relative number of living species Extinction Millions of years ago PeriodEra PaleozoicMesozoicCenozoic Quaternary Tertiary Cretaceous Jurassic Triassic Permian Carboniferous Devonian Silurian Ordovician Cambrian Today 65 180 250 345 500 Extinction Extinction Extinction Extinction Extinction
- 66. Biodiversity • Speciation –Extinction=Biodiversity • Humans major force in the premature extinction of species. Extinction rate increased by 100-1000 times the natural background rate. • As we grow in population over next 50 years, we are expected to take over more of the earth’s surface and productivity. This may cause the premature extinction of up to a QUARTER of the earth’s current species and constitute a SIXTH mass extinction – Genetic engineering won’t solve this problem – Only takes existing genes and moves them around • Know why this is so important and what we are losing as it disappears….
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