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Descent with modification. A. Change in species over time B. Change in gene frequencies from generation to generation C. A Process of change.

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Presentation on theme: "Descent with modification. A. Change in species over time B. Change in gene frequencies from generation to generation C. A Process of change."— Presentation transcript:

1 Descent with modification


3 A. Change in species over time B. Change in gene frequencies from generation to generation C. A Process of change

4 A. Natural Selection – Requires 1. Genetic diversity 2. differential reproduction by individuals with the most fit genes 3. Increase in those genes within population

5 A. Carolus Linnaeus (1707-1778) 1. Binomial Nomenclature Genus species 2. nested groupings into increasingly general categories based on morphology 3. K P C O F G S 4. Kingdom, phylum, class, order, family, genus, species 5. now we have added Domains

6 B. Stratification – 1. rock laid down in layers 2. oldest at bottom 3. fossils in strata show when organisms lived order of appearance (now isotopic dating) 4. Older fossils more dissimilar to modern 5. species appear and disappear 6. Cuvier (1769-1832) catastrophism a. catastrophes destroyed species in an area new species moved in

7 C. Lamarck (1744-1829) 1. one of many to propose that life evolves as environments change 2. first to propose mechanism 3. compared fossils showing lines of descent a. chronological fossils show gradual change b. leading to modern species c. use and disuse d. inheritance of acquired characteristics

8 A. Charles Lyell ( 1797 – 1875) 1. Geologist 2. Theory of Uniformity 3. Natural processes observed today are the same as processes acting in the past 4. The rate of processes today mirror those of the past 5. contradicted young earth theory

9 B. Thomas Malthus: economist 1. war and famine result from human overpopulation 2. Other organisms also produce more individuals than can survive

10 C. Alfred Wallace (1823-1913) 1. first to publish Natural Selection as a mechanism for evolution 2. ideas nearly identical to Darwin’s D. Charles Darwin ( 1809 – 1882) 1. Origin of Species 2. extensive evidence of natural selection 3. Lylle, Darwin & Wallace convinced most scientists with in 10 years

11 Three Main Ideas 1) Unity of Life: shared characteristics attributed to shared common ancestor 2) Diversity of Life: due to descent with modification 3) Match between organisms and environments: due to adaptation

12 A. Artificial selection: selective breeding can produce visible change over a life-time B. Organisms produce more offspring than can survive (Malthus) C. members of a population vary in inherited traits

13 A. If artificial selection can produce rapid change….then natural selection could produce dramatic change given enough time B. Lyell suggested a time line of millions of years C. If only some organisms can survive then those with the best variations are more likely to survive which will cause good genes to accumulate in population

14 A. Fitness: ability to pass on its genes 1. survive 2. mate 3. fertile offspring live to reproduce B. Adaptation: inherited traits that improve fitness in a given environment 1. individuals can NOT adapt its genetic!! 2. only populations adapt over generations

15 A. speciation – one species branches into 2 different species B. Adaptive radiation –1 species gives rise to many species (common after mass extinctions) 1. individuals disperse to new environments 2. adapting to new environment causes them to change into new species

16 C. Universal Common Ancestor – all started from some single celled organisms 1. ‘the unity of life’ 2. universal genetic code DNA, RNA 3. shared genes 4. replication 5. transcription/translation 6. shared proteins

17 A. Direct observation – species change over time 1. Bacteria develop antibiotic resistance a. MRSA – resistant to multiple antibiotics 2. Weeds develop resistance to roundup Figure 1. Number of weed species with glyphosate resistant populations and number of states with glyphosate-resistant weed populations. Source: Heap, 2009.Heap, 2009

18 3. Grant’s finch research a. recorded beak depth of all finches on an island over 30 years

19 B. Homology: similarities resulting from common ancestor 1. Homologous Structures a. anatomical features b. same underlying structure c. may have adapted to different function

20 d. embryo homology may be lost in adult 1. pharyngeal arches – all chordates 2. post anal tail – all chordates


22 2. Vestigial Structures : inherited from ancestor but no longer used a. explains presence of useless structures b. pelvic girdle & femur in whale & snake

23 C. Human vestigial structures

24 3. molecular homologies: same DNA/ protein a. all organisms homologous DNA structure b. Many homologous DNA genes 1. some have developed a new function 2. some still same function a. genes for ribosome subunits homologous between humans and bacteria 3. some genes vestigial

25 A. document formation of new species by sequential fossils

26 1. Geographic distribution of species 2. endemic species : a. ancestor from mainland b. adaptive radiation c. island species all share 1. homologous structures 2. homologous DNA/proteins d. same homologies shared with a mainland species


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