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How did life begin? Miller and Urey’s Experiment

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Presentation on theme: "How did life begin? Miller and Urey’s Experiment"— Presentation transcript:

1 How did life begin? Miller and Urey’s Experiment
Passed sparks through a mixture of hydrogen methane ammonia and water This produced amino acids – the building blocks of life

2 E N D O S Y M B T I H O E T O I R C Y

3 Theory of Life cont. Endosymbiotic theory
eukaryotic cells arose from living communities formed by prokaryotic organisms Ancient prokaryotes entered primitive eukaryotic cells and remained there as organelles


5 Lamark Theory of acquired characteristics
Lamark said organisms acquired traits by using their bodies in new ways These new characteristics were passed to offspring Lamark was totally wrong!

6 Geologists: Hutton and Lyell
Fundamentalists said that the earth was around 6000 years old Hutton and Lyell argued that the earth is many millions of years old b/c layers of rock take time to form processes such as volcanoes and earthquakes shaped the earth and still occur today

7 Malthus Reasoned that if the human population continued to grow unchecked, sooner or later there would be insufficient living space and food for everyone


9 Charles Darwin (1809-1882) Sailed around the world 1831-1836

10 2. What did Darwin’s Travels reveal
The diversity of living species was far greater than anyone had previously known!! These observations led him to develop the theory of evolution!!

11 3.How did tortoises and birds differ among the islands of the Galapagos?
Warbler finch Woodpecker finch Small insectivorous tree finch Large insectivorous Vegetarian Cactus finch Sharp-beaked finch Small ground finch Medium ground finch Large ground Insect eaters Bud eater Seed eaters Cactus eater Warbler Tree finches Ground finches

12 Galapagos Tortoises

13 Evolution is when organisms change over time
Evolution is when organisms change over time. So, modern organisms descended from ancient ones

14 Evolution is a Theory – Just like Gravity!
Evolution is a well supported explanation of phenomena that have occurred in the natural world A theory in science must be supported by facts, it can’t be based on supposition.

15 Darwin finally published his ideas in 1859
Only when other naturalists were developing the same theory that he had did Darwin finally publish his findings.

16 Artificial Selection nature provides variation, humans select variations that are useful. Example - a farmer breeds only his best livestock

17 Natural Selection The traits that help an organism survive in a particular environment are “selected” in natural selection

18 What color genes are in the beetle gene pool?

19 What’s happening to the color genes in the
beetle gene pool? Why is this happening?

20 Explain why we say green beetles have been
selected against while brown beetles have been selected for?

21 Natural Selection and Species Fitness
Overtime, natural selection results in changes in the inherited characteristics of a population. These changes increase a species fitness (survival rate) Bottom line: Those that are best adapted to their environment survive to reproduce.

22 Evidence of Evolution Fossil Record
Geographic Distribution of Living Species Homologous Body structures Similarities in Embryology Vestigial organs

23 Evidence of Evolution Fossil Record provides evidence that living things have evolved Fossils show the history of life on earth and how different groups of organisms have changed over time

24 Primate Fossils Australopithecus Homo erectus Homo sapien

25 Remember PANGEA?

26 Evidence of Evolution Geographic Distribution of Living Species
Similar animals in different locations were the product of different lines of descent

27 Evidence of Evolution Analogous Structures are the result of
Geographic Distribution of Living Species Analogous Structures are the result of convergent evolution Similar animals in different locations exhibit analogous structures due to similar environmental pressures. Eg. North American flying squirrel and the Australian sugar glider

28 This means they are analogous structures.

29 Convergent evolution Fish: aquatic vertebrates
Dolphins: aquatic mammals similar adaptations to life in the sea not closely related Those fins & tails & sleek bodies are analogous structures!

30 Evidence of Evolution Adaptive radiation leads to
Homologous Body Structures thru divergent evolution Structures that have different mature forms but develop from the same embryonic tissues e.g. Wing of bat, leg of turtle & human arm, are similar by de- scent not function. Turtle Alligator Bird

31 Convergent evolution Fish: aquatic vertebrates
Dolphins: aquatic mammals similar adaptations to life in the sea not closely related Those fins & tails & sleek bodies are analogous structures!

32 Homologous Body Structures…………
…………are the result of divergent evolution

33 13. Evidence of Evolution Similarities in Embryology
In their early stages of development, chickens, turtles and rats look similar, providing evidence that they shared a common ancestry.

34 Embryological development

35 Vestigial organs Modern animals may have structures that serve little or no function remnants of structures that were functional in ancestral species evidence of change over time some snakes & whales show remains of the pelvis & leg bones of walking ancestors eyes on blind cave fish human tail bone This is not LaMarck’s loss from “disuse”!

36 Vestigial Structures in snakes

37 Vestigial Structures in whales

38 Molecular record Comparing DNA & protein structure
universal genetic code! DNA & RNA compare common genes cytochrome C (respiration) hemoglobin (gas exchange) Why compare these genes? 25 50 75 100 125 Millions of years ago Horse/ donkey Sheep/ goat Goat/cow Llama/ cow Pig/ Rabbit/ rodent Horse/cow Human/rodent Dog/ Human/ Human/kangaroo Nucleotide substitutions Closely related species have sequences that are more similar than distantly related species DNA & proteins are a molecular record of evolutionary relationships

39 Comparative hemoglobin structure
Human Macaque Dog Bird Frog Lamprey Why does comparing amino acid sequence measure evolutionary relationships? 8 32 45 67 125 10 20 30 40 50 60 70 80 90 100 110 120 Number of amino acid differences between hemoglobin (146 aa) of vertebrate species and that of humans

40 Descent with Modification
Each living species has descended with changes from other species over time


42 Summary of Darwin’s Theory
1. Organisms differ; variation is inherited 2. Organisms produce more offspring than survive 3. Organisms compete for resources 4. Organisms with advantages survive to pass those advantages to their children 5. Species alive today are descended with modifications from common ancestors

43 Variation in Populations
2 processes can lead to this: Mutations - change in DNA sequence Gene Shuffling – from sexual reproduction

44 Gene Pool Combined genetic info. of all members
Allele frequency is # of times alleles occur

45 Genetic Drift changes populations…
Random change in allele frequency causes an allele to become common

46 Founder Effect: a cause of genetic drift attributable to colonization by a limited number of individuals from a parent population

47 Evolution of Populations
Occurs when there is a change in relative frequency of alleles………. in other words – a change in the contents of the gene pool

48 Gene Flow: genetic exchange due to the migration of fertile individuals or gametes between populations (reduces differences between populations)

49 Nonrandom mating aka artificial selection: inbreeding and assortive mating (both shift frequencies of different genotypes)

50 Natural Selection: differential success in reproduction; only form of microevolution that adapts a population to its environment

51 Single-Gene vs. Polygenic Traits
2 Distinct Phenotypes Polygenic: Many Phenotypes (EG: tongue rolling)

52 Natural Selection on Polygenic Traits
Shifts to middle range 2 extremes 1 extreme

53 Are you more closely related to a turtle or a frog?

54 Natural selection in action
Insecticide & drug resistance insecticide didn’t kill all individuals resistant survivors reproduce resistance is inherited insecticide becomes less & less effective The evolution of resistance to insecticides in hundreds of insect species is a classic example of natural selection in action. The results of application of new insecticide are typically encouraging, killing 99% of the insects. However, the effectiveness of the insecticide becomes less effective in subsequent applications. The few survivors from the early applications of the insecticide are those insects with genes that enable them to resist the chemical attack. Only these resistant individuals reproduce, passing on their resistance to their offspring. In each generation the % of insecticide-resistant individuals increases.

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