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Natural Selection Presentation Transcript

Slide 1 - Evolution and Darwin
Slide 2 - Evolution The processes that have transformed life on earth from it’s earliest forms to the vast diversity that characterizes it today. A change in the genes!!!!!!!!
Slide 3 - Old Theories of Evolution Jean Baptiste Lamarck (early 1800’s) proposed: “The inheritance of acquired characteristics” He proposed that by using or not using its body parts, an individual tends to develop certain characteristics, which it passes on to its offspring.
Slide 4 - “The Inheritance of Acquired Characteristics” Example: A giraffe acquired its long neck because its ancestor stretched higher and higher into the trees to reach leaves, and that the animal’s increasingly lengthened neck was passed on to its offspring.
Slide 5 - Charles Darwin Influenced by Charles Lyell who published “Principles of Geology”. This publication led Darwin to realize that natural forces gradually change Earth’s surface and that the forces of the past are still operating in modern times.
Slide 6 - Charles Darwin Darwin set sail on the H.M.S. Beagle (1831-1836) to survey the south seas (mainly South America and the Galapagos Islands) to collect plants and animals. On the Galapagos Islands, Darwin observed species that lived no where else in the world. These observations led Darwin to write a book.
Slide 7 - Charles Darwin Wrote in 1859: “On the Origin of Species by Means of Natural Selection” Two main points: 1. Species were not created in their present form, but evolved from ancestral species. 2. Proposed a mechanism for evolution: NATURAL SELECTION
Slide 8 - Natural Selection Individuals with favorable traits are more likely to leave more offspring better suited for their environment. Also known as “Differential Reproduction” Example: English peppered moth (Biston betularia) - light and dark phases
Slide 9 - Darwin’s 5 points Population has variations. Some variations are favorable. More offspring are produced than survive Those that survive have favorable traits. A population will change over time.
Slide 10 - Artificial Selection The selective breeding of domesticated plants and animals by man. Question: What’s the ancestor of the domesticated dog? Answer: WOLF
Slide 11 - Evidence of Evolution 1. Biogeography: Geographical distribution of species. 2. Fossil Record: Fossils and the order in which they appear in layers of sedimentary rock (strongest evidence).
Slide 12 - Eastern Long Necked Turtle
Slide 13 - Evidence of Evolution 3. Taxonomy: Classification of life forms. 4. Homologous structures: Structures that are similar because of common ancestry (comparative anatomy)
Slide 14 - Evidence of Evolution 5. Comparative embryology: Study of structures that appear during embryonic development. 6. Molecular biology: DNA and proteins (amino acids)
Slide 15 - Population Genetics The science of genetic change in population. Remember: Hardy-Weinberg equation.
Slide 16 - Population A localized group of individuals belonging to the same species.
Slide 17 - Species A group of populations whose individuals have the potential to interbreed and produce viable offspring.
Slide 18 - Gene Pool The total collection of genes in a population at any one time.
Slide 19 - Hardy-Weinberg Principle The concept that the shuffling of genes that occur during sexual reproduction, by itself, cannot change the overall genetic makeup of a population.
Slide 20 - Hardy-Weinberg Principle This principle will be maintained in nature only if all five of the following conditions are met: 1. Very large population 2. Isolation from other populations 3. No net mutations 4. Random mating 5. No natural selection
Slide 21 - Hardy-Weinberg Principle Remember: If these conditions are met, the population is at equilibrium. This means “No Change” or “No Evolution”.
Slide 22 - Macroevolution The origin of taxonomic groups higher than the species level.
Slide 23 - Microevolution A change in a population’s gene pool over a secession of generations. Evolutionary changes in species over relatively brief periods of geological time.
Slide 24 - Five Mechanisms of Microevolution 1. Genetic drift: Change in the gene pool of a small population due to chance. Two examples: a. Bottleneck effect b. Founder effect
Slide 25 - a. Bottleneck Effect Genetic drift (reduction of alleles in a population) resulting from a disaster that drastically reduces population size. Examples: 1. Earthquakes 2. Volcano’s
Slide 26 - b. Founder Effect Genetic drift resulting from the colonization of a new location by a small number of individuals. Results in random change of the gene pool. Example: 1. Islands (first Darwin finch)
Slide 27 - Five Mechanisms of Microevolution 2. Gene Flow: The gain or loss of alleles from a population by the movement of individuals or gametes. Immigration or emigration.
Slide 28 - Five Mechanisms of Microevolution 3. Mutation: Change in an organism’s DNA that creates a new allele. 4. Non-random mating: The selection of mates other than by chance. 5. Natural selection: Differential reproduction.
Slide 29 - Modes of Action Natural selection has three modes of action: 1. Stabilizing selection 2. Directional selection 3. Diversifying selection
Slide 30 - 1. Stabilizing Selection Acts upon extremes and favors the intermediate.
Slide 31 - 2. Directional Selection Favors variants of one extreme.
Slide 32 - 3. Diversifying Selection Favors variants of opposite extremes.
Slide 33 - Speciation The evolution of new species.
Slide 34 - Reproductive Barriers Any mechanism that impedes two species from producing fertile and/or viable hybrid offspring. Two barriers: 1. Pre-zygotic barriers 2. Post-zygotic barriers
Slide 35 - 1. Pre-zygotic Barriers a. Temporal isolation: Breeding occurs at different times for different species. b. Habitat isolation: Species breed in different habitats. c. Behavioral isolation: Little or no sexual attraction between species.
Slide 36 - 1. Pre-zygotic Barriers d. Mechanical isolation: Structural differences prevent gamete exchange. e. Gametic isolation: Gametes die before uniting with gametes of other species, or gametes fail to unite.
Slide 37 - 2. Post-zygotic Barriers a. Hybrid inviability: Hybrid zygotes fail to develop or fail to reach sexual maturity. b. Hybrid sterility: Hybrid fails to produce functional gametes. c. Hybrid breakdown: Offspring of hybrids are weak or infertile.
Slide 38 - Allopatric Speciation Induced when the ancestral population becomes separated by a geographical barrier. Example: Grand Canyon and ground squirrels
Slide 39 - Adaptive Radiation Emergence of numerous species from a common ancestor introduced to new and diverse environments. Example: Darwin’s Finches
Slide 40 - Sympatric Speciation Result of a radical change in the genome that produces a reproductively isolated sub-population within the parent population (rare). Example: Plant evolution - polyploid A species doubles it’s chromosome # to become tetraploid.
Slide 41 - Interpretations of Speciation Two theories: 1. Gradualist Model (Neo-Darwinian): Slow changes in species overtime. 2. Punctuated Equilibrium: Evolution occurs in spurts of relatively rapid change.
Slide 42 - Convergent Evolution Species from different evolutionary branches may come to resemble one another if they live in very similar environments. Example: 1. Ostrich (Africa) and Emu (Australia). 2. Sidewinder (Mojave Desert) and Horned Viper (Middle East Desert)
Slide 43 - Coevolution Evolutionary change, in which one species act as a selective force on a second species, inducing adaptations that in turn act as selective force on the first species. Example: 1. Acacia ants and acacia trees 2. Humming birds and plants with flowers with long tubes
Slide 44 - This powerpoint was kindly donated to www.worldofteaching.com http://www.worldofteaching.com is home to over a thousand powerpoints submitted by teachers. This is a completely free site and requires no registration. Please visit and I hope it will help in your teaching.