Bio 1010 Dr. Bonnie A. Bain

CHAPTER 13 Evolution Part 2

The Theory of Evolution Both Charles Darwin and Alfred Russell Wallace came up with the mechanism for evolution Mechanism: natural selection (more details later)

Figure 1.12

November 24, 1859 Origin of Species published In this book, Darwin lays out the evidence for the theory of evolution by natural selection

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Figure 13.00d

Darwin presented 2 main concepts in his book: 1. Contemporary species arose from a succession of ancestors through descent with modification [Evolution] 2. Mechanism for evolution: Natural Selection

Evolution or Descent with Modification As descendants of the earliest organisms spread into various habitats over millions of years, they accumulated different modifications to diverse ways of life

The history of life is analogous to a tree Patterns of descent are like the branching and re-branching from a common trunk

Located at each fork (node) of the tree is the common ancestor for all of the ones above that node Closely related species share many characteristics because they both share a common ancestor

Figure 13.6 Descent with Modification

Fig Tetrapod limbs Amnion Feathers Lungfishes Mammals Amphibians Lizards and snakes Crocodiles Hawks and other birds Ostriches Amniotes Tetrapods Birds

Natural Selection Evolutionary adaptations: The results of natural selection Adaptation: An inherited characteristic that enhances an organism's ability to survive and reproduce in a particular environment

Figure 1.13 Adaptive Radiation

Cultural and Scientific Context for Darwin's Work The view of life presented in The Origin of Species contrasted sharply with prevailing cultural views during Darwin's lifetime: Earth was relatively young (6,000 yrs) Lots of different species on Earth, but they were not related to each other

Evolutionary thought prior to Darwin Ancient Greece (2,500 years ago) Anaximander (Greek philosopher) Life originated in the water Simplest forms evolved first Gradually changed into more complex forms

Ancient Greece (2,500 years ago) Aristotle (Greek philosopher) Species are fixed (permanent) and do not evolve Aristotle's ideas survived the Dark Ages and influenced Renaissance science

1766 Georges Buffon French naturalist, studied fossils Earth much older than 6,000 yrs. (based on fossil evidence) Fossils are ancient versions of many contemporary species

1809 Jean-Baptiste de Lamarck Best explanation for fossils: Life evolves Mechanism for evolution: Inheritance of acquired traits

Extra Photo 13.03x4 Jean-Baptiste de Lamarck

Mechanism for evolution: Inheritance of acquired traits By using or not using certain body parts, an individual may develop (acquire) certain traits which can be passed on to its offspring Example: Giraffe's long neck

Was Lamarck right?? Do we inherit acquired traits??

Whether or not Lamarck was right about inheritance, he did help set the stage for Darwin's ideas (Darwin was born in 1809) Also, Lamarck got lots of other things right (described lots of new species, etc.)

Figure 13.3

Extra Photo 13.03x5 Next: Charles Lyell Scottish geologist 1830 Principles of Geology