Presentation on theme: "Ch. 15 Darwin’s Theory of Evolution"— Presentation transcript:
1 Ch. 15 Darwin’s Theory of Evolution Unit 5 EvolutionCh. 15 Darwin’s Theory of Evolution
2 The Puzzle of Life’s Diversity Evolution - modern organisms have descended from ancient organisms (change over time)Theory - a well-supported, testable explanation of phenomena that have occurred in the natural world
3 Voyage of the HMS Beagle 1831Charles Darwin contributed most to our understanding of evolutionHe made observations & collected evidence that led him to propose a hypothesis about the way life changes over time.
4 Voyage of the BeagleThat hypothesis, now supported by a large amount of evidence, has become the Theory of evolution
5 Darwin’s Observations Darwin collected the preserved remains of ancient organisms - FossilsSome of these fossils resembled organisms that were still aliveOthers looked unlike any creature ever seen
6 Darwin’s Observations The Galapagos Islands influenced Darwin the mostHe observed that the characteristics of animals & plants varied among the different Islands.
7 Darwin’s Observations Each island had a different climate although they were very close.He studied tortoises.Each tortoise’s shell had a different shape depending on which island it came from.He wondered if the animals living on different islands were once related….
8 Views before Darwin Earth was created only a few thousand years ago. Since creation, neither earth nor its species had changedDarwin was influenced by several individuals.
9 An Ancient, Changing Earth Hutton & Lyell helped scientists recognize that Earth is millions of years old.They also noted that the processes that changed Earth in the past are the same processes that are changing Earth now.
10 Lamarck’s Evolution Hypothesis The year that Darwin was born, Lamarck published his hypothesisHe proposed that by selective use or disuse of organs, organisms acquired or lost certain traits during their lifetimeOver time, this process led to change in a species
11 Lamarck’s Explanation Tendency toward perfectonUse and DisuseInheritance of Acquired traits
12 Population GrowthEnglish economist, Malthus, published a book, noting that babies were being born faster than people were dyingHe stated that if the human population continued to grow unchecked, sooner or later there would be insufficient living space & food for everyone
13 Darwin Presents His Case In 1859, Darwin published the results of his work in a book, On the Origin of Species.In his book, he proposed a mechanism for evolution called natural selection.He stated that evolution has been taking place for millions of years, & continues in all living things
14 Darwin Presents His Case Species on Earth today descended from ancestral animals in various habitats.Heritable variation- differences that are passed from parents to offspring.Variations were thought to be unimportant.
15 Inherited Variation & Artificial Selection Artificial selection - nature provided the variation, & humans selected those variations that they found useful.It has produced diverse plants & animals by selectively breeding for different traits.
16 Evolution by Natural Selection Struggle for existence - the members of each species compete regularly to obtain food, living space, & other necessities of lifePredators that are faster & better at catching prey are more likely to survive
17 Evolution by Natural Selection Fitness - the ability of the organism to survive & reproduce in its specific environ.Fitness is the result of adaptations
18 Evolution by Natural Selection Adaptation - any inherited characteristic that increases an organisms’ chance of survivalSuccessful adaptations allow organisms to become better suited to their environ. & thus better able to survive
19 Evolution by Natural Selection Individuals that are better suited to their environ., with adaptations that enable fitness, survive & reproduce most successfully - Survival of the Fittest
20 Evolution by Natural Selection Since it is similar to artificial selection, Darwin referred to survival of the fittest as - Natural SelectionIn both AS & NS, only certain individuals of a population produce new individuals
21 Evolution by Natural Selection However, in NS, the traits being selected, & therefore, increasing over time, contribute to an organism’s fitnessNS takes place without human control or direction
22 Evolution by Natural Selection NS results in changes in the inherited characteristics of a population, that increase a species’ fitness in its environ.Over time, NS produces organisms that have different structures, & occupy different habitats
23 Evolution by Natural Selection As a result, species today look different from their ancestorsEach living species has descended, with changes, from other species over time - Descent with Modification
24 Evolution by Natural Selection Descent with modification also implies that all living organisms are related to each otherCommon descent - all species (living & extinct) were derived from common ancestors
25 Evidence of EvolutionDarwin argued that living things have been evolving on Earth for millions of yearsEvidence of this could be found: in the fossil record, the geographical distribution of living species, homologous structures of living organisms, & similarities in early development
26 Evidence of Evolution The Fossil Record: Darwin noticed that the sizes, shapes, & varieties of related organisms preserved in the fossil record, changed over time
27 Evidence of Evolution Geographic Distribution of Living Species: Darwin realized that similar animals in different locations were the product of different lines of evolutionary descent
28 Evidence of Evolution Homologous Body Structures: Homologous structures - structures that have different mature forms but develop from the same embryonic tissuesNot all homologous structures serve important functionsOrgans of many animals are so reduced in size that they are just vestiges, or traces, of homologous organs