Jean Baptiste Lamarck (1744-1829):

1. Jean Baptiste Lamarck (1744-1829): • Noted fossils resembled living species • Suggests fossils were ancestors of living species • Features had modified over time in response to changing climates & geography • Called this modification, “Transformational evolution”

2. Lamarck’s Theory of the Inheritance of Acquired Characteristics • Living things make adjustments to their environment during their lifetime that can be passed down to their offspring, making the offspring, better adapted to the environment

3. Based on Use/Disuse of Body Parts • Some organs or body parts may be used more than others during process of adaptation • Those “used” more are enhanced • Those “not used” are reduced • Believed these physical changes could be passed down from one generation to the next

5. Significance of Larmarck’s Theory • Recognized crucial relationship between living things and the environment • Modern genetic research tells us genes can be influenced by the environment & changes in genes CAN be passed on to offspring

6. Charles Darwin (1809-1882) • British naturalist • First studied medicine, then ministry for Church of England • 5 year voyage around the world on the H.M.S. Beagle as naturalist • Observations from Galapagos Islands critical to formulation of theory

7. “The Most Powerful Idea in Science”: Evolution by Natural Selection • Developed by Charles Darwin and Alfred Russell Wallace • Is the cornerstone of modern evolutionary theory because it explains how biological change & adaptation occurs

8. NATURAL SELECTION • Darwin & Wallace recognized that variation in populations already existed • This variation (genetic diversity) provided the “raw material” for natural selection; some individuals would have traits that gave them an advantage to surviving & reproducing over others

9. Darwin observed that: • Differences (variation) exist between individuals • Some of these differences are passed down to offspring • Differences matter when change in environment (selective pressure) occurs • Those individuals with favorable traits have an advantage over those who do not • More likely to survive, reproduce, and pass on those traits to offspring • Environmental context (nature) determines which traits are advantageous

10. Natural Selection, cont. • Favorable traits increase while less favorable traits decrease • Over long periods of time, successful variations/traits accumulate such that later populations may become distinct from ancestral ones, hence, new species evolve • Populations are adaptable & can change over time in response to changing environments

11. What is a population? • A group of individuals that: • is reproductively isolated (of the same species) • occupies a specific area Natural selection operates on or “selects” individuals, but it is the population that evolves

12. Lamarck vs. Darwin Lamarck: Variation when need Darwin: Variation already present

13. Natural Selection, cont. • Geographical isolation can fuel speciation as populations respond to different selective pressures (different environmental circumstances that influence reproductive success) • Sexual selection also affects the process of natural selection; female preference for specific male qualities

14. In Sum • Natural selection is a process of elimination • “Survival of the fittest” : to be “fit” means to possess certain characteristics that increase the probability of survival & reproductive success • Natural selection is essentially, the differential reproductive success of individuals in a population, mediated by the environment

15. Peppered Moths: Natural selection in action • Common variety of moth is spotted gray (peppered) • Also a dark colored moth of same species (less common) • Peppered moth better camouflaged when resting on lichen-covered trees; dark moths more visible to predators, are eaten more frequently (producing fewer offspring than light colored moths)

16. Peppered Moths, cont. • Coal dust from factories kills lichen on trees and turns the bark a dark gray • Light gray (peppered) moths are more visible; dark gray moths better camouflaged • Dark gray variety increase in number, light gray population declines

17. Peppered Moths, cont. • Pollution control enables lichen to grow back on trees • Peppered moths once again better camouflaged, darker variety declines • Natural Selection Short

18. Pesticide resistance among beetles

19. The “–isms” and “schisms” of Darwin’s Theory “-isms” “schisms” Seemed to contradict religious explanations Led to Eugenics movement, including the Holocaust; Darwin never used term “survival of fittest” Process of evolution includes much more than Darwin ever explained or understood (in 19th century) Darwin would never have supported those agendas • Implies a “belief system,” like Hinduism, absolutism, etc. • Ideas associated with Nat. Sel. used to explain & justify social differences (Social Darwinism) or “survival of the fittest” – Not Darwin’s doing • Darwinism used synony-mously with “Evolution” • Darwin’s name & ideas used by others to advance their own agendas

20. What Evolution & Natural Selection ARE NOT: • Evolution means that organisms are “progressing” or getting better.

21. What it IS: • Natural selection does weed out individuals that are unfit in a particular environment • What’s “good” or “better” in one place or time, may not be in another • Fitness (reproductive success) is linked to the environment not progress Example: Chimps are chimps because the features they have are perfectly adapted to their environment & niche

22. Misconception: Natural Selection involves organisms “trying” to adapt

23. Adaptation doesn’t involve “trying” • Nat. Sel. leads to adaptation • Stems from variation (genetic diversity) in the population (no two individuals are exactly alike) • Some individuals will have genes (characteristics) that will enhance its chances of survival, and others won’t

24. Misconception: Evolution means that life has changed “by chance” • There is an element of chance (mutations, genetic processes, movement of populations, etc.) and of luck • Selection of/for specific traits is not random • Nat. Sel. favors characteristics that confer an advantage to survival, thereby increasing the frequency of that trait in the population to keep it adapted to its environment

25. Natural Selection in Action:Darwin’s Finches Revisited Beak of the Finch