Evolution

1. Evolution Evolution is the explanation of the origin of species

2. Linnean Classification of Living Organisms Domain Kingdom Phylum Class Order Family Genus Species more inclusive Carl Linneaus - aka Carl von Linné, Carolus Linnaeus, Carlolus a Linné (1707-1778)

3. Higher Level Linnean Classification

4. Domain – Eukarya (genetic material within nucleus) Kingdom – Animalia (multicellular eukaryotic heterotrophs) Phylum – Chordata (notochord, post-anal tail) Class – Chondrichthyes (cartilaginous fish) Order – Carcharhiniformes (ground sharks) Family – Carcharhinidae (requiem sharks) Genus – Carcharhinus Species – C. leucas (bull shark)

5. What is a Species? Biological Species Concept – a species is a group of populations which are actually or potentially interbreeding, and which are reproductively isolated from other groups under natural conditions. Not possible for fossils. Morphological Species Concept – a species is a diagnosable (recognizable traits that can be measured) cluster of individuals within which there is a pattern of ancestry and descent, and beyond which there is not.Applied to fossils.

6. Difficulties applying the MSC newborn female juvenile adult female male adult male Sexual dimorphism Ontogeny

7. Changes in limb development have led to a variety of limb morphologies in all major groups of vertebrates.

8. Jean-Baptiste Pierre Antoine de Monet Chevalier de Lamarck (1744-1829) Recognized lines of descent from fossil forms to living forms • Species arise from “inner need” • Acquired characters inherited by offspring

9. “Catastrophist” Cuvier Creatures became extinct Apparent major variation within fossils from strata separated by unconformities – Catastrophe Acknowledged change from one species to another occurred – but how?

10. Charles Darwin (1809-1882) Natural Selection & Survival of the Fittest Observed captive breeding of birds Five-year mission to explore new worlds, seek out new life…to boldly go where no one had gone before…

11. Voyage of the HMS Beagle (1831-1836)

12. Through his experiences, Darwin noted that: • Organisms in all populations posses heritable variations – • size, speed, agility, vision, digestive enzymes, color, etc…. 2. Some variations are favorable than others – some variant types have a competitive edge in acquiring resources and/or avoiding predators. 3. Not all young survive to reproductive maturity. 4. Those with favorable variations are more likely to survive and pass on their favorable variations. These are the basic facts behind…natural selection.

13. Mechanism of natural selection • Individuals differ (vary) in virtually every detail • These differences have important consequences • These differences are heritable Differential survival Differential reproductive success

14. Differential survival + reproductive success = ADAPTATION Meaning…a group of organisms (species) becomes better suited to the environment Adaptation = outcome of natural selection

15. Lamarck vs. Darwin Evolution of the giraffe (Giraffa sp.) s s

16. What controls variation in species?It’s in the DNA DNA (deoxyribonucleic acid) is a complex, double stranded helical molecule (chromosome) that contains genetic information for the development & function of organisms. Traits are controlled by factors known as genes. Genes (hereditary units) are specific segments of the chromosome. Genes controlling a particular trait occur in alternate forms (alleles). Number of chromosomes is specific for a given species, but varies among species (fruit flies have 8, humans have 46, horses have 64).

17. DNA Set of Human Chromosomes

18. How do large scale changes occur? Homeobox (HOX) genes • HOX genes control the layout of body plans in animals (may also exist in plants). • Small changes in these genes can cause major changes in body form. • These genes are highly conserved (nearly the same) in all groups of animals. • These genes act as “switches” that turn on and off developmental processes.

19. Changes in the gene that forms the antenna complex in flies can produce bizarre mutations - legs form where antennae should form. Normal Fly HOX Mutants

20. So what causes variation? Mutations (changes in the DNA coding sequence) Mutations include point mutations (a change in a particular gene), or chromosomal mutations (affecting a large portion of a chromosome). Mutations are heritable only if they occur on sex cells. Mutations are caused by chemicals, UV radiation, X-rays, and extreme temperature changes.

21. Neutral – variation of same amino acid Beneficial or Harmful– variation of same amino acid

22. But, how is variation maintained within species? Why don’t some traits simply blend with other traits and eventually disappear? 1. Experiments performed on garden peas by Austrian Gregor Mendell (1860s) showed that genes controlling traits do not blend. 2. Traits may not be expressed in each generation (recessive), but they are not lost. Alternate expression of traits (alleles) can occur in different generations.

23. Mendell’s Flowers hybrid

24. Conclusions: • Genetic traits are passed on to offspring• Offspring with beneficial traits more likely to survive and pass on genetic material• Within each new generation, more and more animals with beneficial traits survive to pass along genes• Over many generations, a population (species) with beneficial trait occupies region= EVOLUTION

25. Driving Forces of Evolution • Need to perpetuate the species • Competition for resources (food, living space) • Avoiding predation

26. Advertising your “fitness” It is better to look good than to feel good…

27. Sexual Selection Sexes look different (dimorphism) – typically, males are showy Mate choice occurs - typically, females are choosy

28. Cost of reproductive success may be high… Megaloceras Stalk-eyed fly Stethacanthus

29. Competition for Resources You must be this tall to eat these leaves… “ancestral species” modern giraffe

30. Avoiding Predators Peppered moths before coal soot… Peppered moths after coal soot…

31. Horses – adapting to changing environment and predators Hyracotherium Mesohippus Pliohippus

32. The horse family (phylogenetic) tree:

33. Cladogram of Vertebrata showing… …ancestral relations between organisms – based on morphology and genetics!

34. Time Evolution – Punctuated or Gradual? Species Difference Species Difference Phyletic Gradualism Punctuated Equilibrium

35. Some Common Misconceptions about Evolution: 1. Evolution proceeds strictly by chance. 2. Nothing less than fully developed structures, like eyes, are of any use. 3. No “transitional fossils” (aka missing links) connect ancestors to descendants

36. Evolution proceeds strictly by chance. Sexual selection – not chance. female Think about dog breeds… male

37. 2. Nothing less than fully developed structures are of use Light detection & vision in living organisms What is your definition of “usefulness”?

38. 3. No transitional fossils connect ancestors to descendents Eusthenopteron – a fish ? Acanthostega – an amphibian

39. Tiktaalik – a transitional fossil

40. Clade Tetrapodomorpha “Fishapod”

41. Evolution of Cetacea (whales, dolphins, porpoises) - Cetartiodactyla terrestrial ancestor Basilosaurus fully aquatic Ambulocetus semi-aquatic

42. Evolutionary Pathways Divergent Convergent Parallel

43. Divergence of the Dinosauria from a Single Ancestor

44. Convergent evolution is the process by which similar characteristics involve in distantly related organisms. • Similar characteristics develop independently – caused by adaptations to similar environments.

45. Convergence in skull and dental morphology among Mesozoic Marine Reptiles and Cenozoic Marine Mammals

46. Parallel Evolution is the process by which similar characteristics evolve in closely related organisms . Similar characteristics arise due to adaptation to similar environments.

47. Parallel evolution led to the origin of “saber-toothed cats” several times, while convergent evolution led to a “saber-toothed” marsupial. Hoplophoneus Machairodus Smilodon Thylacosmilus - marsupial

48. Mass Extinction & Subsequent Radiation biodiversity Time (millions of years ago)