Jean Baptiste Lamarck ( ): 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”

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

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

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 (The Epigenome)

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 gene function/expression CAN be passed on to offspring (The Epigenome)

Charles Darwin ( ) 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

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

NATURAL SELECTION  Darwin & Wallace recognized that variation in populations already existed  This variation (genetic diversity) provided the “raw material” for natural selection: – some individuals have traits that give them an advantage to surviving  Any change in the environment can lead to an advantage for some individuals & disadvantage for others  If selective pressure acts against or upon these differences, you get natural selection

Natural Selection in a Nutshell Natural selection is the process by which NATURE (i.e. the environment), selects better adapted individuals for more successful reproduction Variation----Selection-----Variation-----Selection

Lamarck vs. Darwin Lamarck: Variation when needed Darwin: Variation already present

How does this lead to diversity of species? Over long periods of time, successful variations/traits accumulate such that later populations may become distinct (physically, behaviorally) from ancestral ones What defines 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

Diversity of species, cont. If no interbreeding (sharing of genes) occurs, they may eventually become separate species Populations are adaptable & can change over time in response to changing environments

Diversification of species, 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

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 End result is adaptation May result in new species developing, but not always

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)

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

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

Pesticide resistance among beetles

The “–isms” and “schisms” of Darwin’s Theory “-isms” 1.Implies a “belief system,” like Hinduism, absolutism, etc. 2.Ideas associated with Nat. Sel. used to explain & justify social differences (Social Darwinism) or “survival of the fittest” – Not Darwin’s doing 3.Darwinism used synony- mously with “Evolution” 4.Darwin’s name & ideas used by others to advance their own agendas “schisms” 1.Seemed to contradict religious explanations 2.Led to Eugenics movement, including the Holocaust; Darwin never used term “survival of fittest” 3.Process of evolution includes much more than Darwin ever explained or understood (in 19 th century) 4.Darwin would never have supported those agendas

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

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

Misconception: Natural Selection involves organisms “trying” to adapt

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

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