The Puzzle of Life’s Diversity

Charles Darwin sailed around the world on the H. M. S. Beagle in 1831. Evolution: how modern organisms have descended from ancient organisms

Darwin’s Observations Patterns of Diversity: plants and animals well suited to their environments Why 2 similar ecosystems contain different animals Fossils: preserved remains of ancient organisms. Why species disappeared & relation to living species The Galápagos Islands: the characteristics of many animals and plants varied noticeable among the different islands

Important Scientists: Hutton & Lyell the Earth is many millions of years old the processes that changed Earth in the past are the same processes that operate in the present

Important Scientists: Malthus unchecked human population growth would lead to insufficient living space and food Forces Against Growth War Famine Disease

Lamarck’s Evolution Hypothesis Through selective use or disuse of organs, organisms acquired or lost certain traits Traits could then be passed on to offspring. Led to change in a species. Ideas are flawed; traits are inherited and behavior has no effect heritable characteristics. But organisms are adapted to their environment.

Darwin

Darwin Completed 25 years of research Published On the Origin of Species Proposed Natural Selection mechanism for evolution

Evolution By Natural Selection Struggle for existence: member of each species compete regularly for food, living space, and other necessities Survival of the Fittest better suited  survive and reproduce more not well suited  die or leave few offspring

Fitness: ability to survive & reproduce Successful adaptations allow organisms to become better able to survive and reproduce. Natural Selection changes in a population’s inherited characteristics increase a species’ fitness

Evidence of Evolution Fossils: observe changes over time Geographic Distribution: Similar species descended with modifications from a common ancestor Similar embryo development

Embryo Development

Evidence of Evolution Homologous Structures: structures that have different mature forms but develop from the same embryonic tissue vestigial organs: reduced organs are traces of homologous structures miniature legs/tails appendix