Presentation on theme: "Life Science: Chapters 10, 11 and 12 Biology: Chapters 14, 15 and 16"— Presentation transcript:
1Life Science: Chapters 10, 11 and 12 Biology: Chapters 14, 15 and 16 EvolutionLife Science: Chapters 10, 11 and 12Biology: Chapters 14, 15 and 16
2Early NaturalistsCarolus Linnaeus – (1735) He proposed a system of organization for plants, animals and minerals based on their similaritiesGeorge Buffon – (1749) He discussed ideas about relationships between species and sources of biological variationJean Baptiste-Lamarck – (1809) presented evolution as occurring due to environmental change over long periods of time
3Ideas that Led to a Theory Geologic Change – the common view was that the earth was only 6000 years old and that organisms did not change. Fossil evidence played a key role in this idea.Catastrophism – Volcanoes, floods and other natural disasters were the cause of extinction and the formation of all land forms.Gradualism – the idea that changes on Earth occurred by small steps over a long period of timeUniformitarianism – geologic processes add up over long periods of time to cause great change
4Charles DarwinCharles R. Darwin ( ) was a British naturalist who was made famous by theorizing that processes such as natural selection and descent with modification played on species over time, leading to evolution. He published these theories and supporting evidence in his book, On the Origin of Species, in 1859.Darwin collected evidence during his voyage around the world on the merchant vessel, the HMS Beagle. The trip lasted five years, and during this time, Darwin collected many samples, especially from the Galapagos Islands.During his visit to the islands, Darwin noted that the unique creatures were similar from island to island, but perfectly adapted to their environments which led him to ponder the origin of the islands' inhabitants.Among those that struck Darwin so greatly were the finches that are now named in his honor. Darwin would later base some of his thought from the supposing that these finches were all descendants of the same lineage.
5Evolutionary Principles Descent with Modification - Darwin proposed that subsequent generations exhibited small changes that eventually built up in a population over time, leading to great changeVariation – Darwin compared wild a domesticated species and noted many variations. He suggested the source of variation was “reproductive elements prior to conception.”Adaptation – Observations in the Galapagos led him to theorize that animals that are better suited to their environment produce more offspring and that eventually leads to change of the entire population.
8Modes of SelectionNatural Selection – individuals that have inherited beneficial adaptations produce more offspring than do other individuals, therefore only adaptations that give an advantage tend to stay in a populationArtificial Selection – humans intervene and breed for certain purposes and traitsSexual Selection – the ability to produce offspring is dependent on one or more individuals choosing a mate based on desired traits or abilities
9Natural SelectionNatural selection is a mechanism by which individuals that have inherited beneficial adaptations produce more offspring on average than do other individuals.
10Four Main Principles of Natural Selection VariationThe heritable differences in every population are the basis for natural selectionOverproductionHaving many offspring ensures that many will survive, but also increases competitionAdaptationSome variations make some individuals better suited for their environmentDescent with ModificationOver time, all individuals will exhibit the beneficial trait
11Darwin’s EvidenceFossils – Scientists look to fossils to study long periods of time and how organisms changedGeography – comparing species in one island to species on other islands and even mainland South America led Darwin to believe that the land masses were once joinedEmbryology – Studying how an organism develops illuminates similarities among speciesAnatomy – Comparing body parts of different species also shows similarities that suggest a common ancestor
12Anatomical Structures as Evidence Homologous Structure – a similar structure that appears in different organisms and has different functionsAnalogous Structure – structures that performs a similar function but are not similar in originVestigial Structure – remnants of structures or organs that had a function for early ancestors but are no longer needed or functioning in the modern population
14Genetic VariationsGenetic variation in a population increases the chance that at least some individuals will surviveGenetic variation comes from several sources:Mutation – a random change in DNA of a geneRecombination – new allele combinations formed in offspring
15Studying GeneticsThe combined alleles of all the individuals in a population is called the gene pool.Scientists study how frequently alleles occur in a gene pool.Sometimes, certain alleles move from one population to another through interbreeding or migration. This is called gene flow.However, completely due to chance, some alleles either disappear or become more frequent (or fixed) in a population over time. This is called genetic drift.Genetic drift usually only happens in small populations causes to loss of genetic diversity. There are two types:Bottleneck Effect – genetic drift that happens after a catastrophe greatly reduces the population sizeFounder Effect – genetic drift that occurs after a small population colonizes an new area
21How a Species is MadeReproductive Isolation – when members of different populations can no longer successfully mate with one anotherBehavioral Isolation – caused by differences in courtship or mating behaviorsGeographic Isolation – physical barriers prevent mating of populationsTemporal Isolation – timing prevents mating between populationsSpeciation – the rise of two or more species from one common ancestor
22Patterns in EvolutionConvergent Evolution – two species evolve toward similar characteristicsDivergent Evolution – closely related species evolve in different directionsCoevolution – two or more species evolve is response to changes in each otherExtinction – a species as a whole is unable to adapt to changes in its environment and dies outPunctuated Equilibrium – pattern of speciation that states that episodes of speciation occur suddenlyAdaptive Radiation – diversification of one ancestral species into many different species
23Predicting Genotypes in a Population Hardy-Weinberg Equilibrium – used to predict the frequency of genotypes in a populationp2+2pq+q2=1
24Hardy-Weinberg Disclaimers In order for a population to be in Hardy-Weinberg Equilibrium, it must fulfill 5 criteriaLarge populationNo immigration or emmigrationNo mutationsRandom matingNo natural selection