BIO 7:  Lecture 37 Preview

More support for the Theory of Evolution by Natural Selection

• Macroevolution inferred from studies of other isolated populations

     e.g.  Fruitflies in the Hawaiian Islands:  8 volcanic islands formed 1-2 million years ago

        2000-2500 miles away from mainlands

        have several hundred species of fruitflies

        fruitflies related to each other and mainland species, but adapted to different parts of different islands

e.g. Cichlid fish in Lake Victoria:  several hundred species in lake filled 12,000 years ago

Formation of new species requires reproductive isolation.

• Can occur when a population is separated into 2 subpopulations by a geographical  barrier.

•  Can occur in the same location due to other barriers

 A recent example of speciation:  Hawthorn flies used hawthorn fruit for food before colonists came to America.  Colonists brought apple trees.  Apples ripen a few weeks later than hawthorns.  Some hawthorn flies used apples for food.  Now 2 species:  hawthorn fruitflies and apple maggot fruitflies. What is the reproductive isolation barrier?

Evolution by Natural Selection (or descent with modification) is like a low-budget remodeling job:  Each species is not an ideal "house" built from the ground up with a specific design.  Rather, species start with a structure passed on from an ancestor and make use of modifications that become available through mutations.

• Support from embryological studies

• Support from anatomy studies:  homologous structures and vestigial structures

• Support from Cell Biology studies:  Basic similarities are seen in cells and molecules of all organisms.

What acts as a selective barrier between the inside and the outside of all cells?

What molecule carries information passed from one generation to the next in all cells?

What molecule carries energy released from glucose and then releases energy for movement and synthesis in all cells?

What are the two processes by which all cells use information in nucleic acids to make proteins?

Support for the Theory of Evolution by Natural Selection Came from Many Areas of Science

• Paleontology (the study of fossils)

Fossils = mineralized remains or impressions (e.g. tracks) of organisms, usually in layers of rock (sedimentary rock)

   Record incomplete

    only some conditions right for preservation

    only some parts preserved

    only some found millions of years later

 

  Dating of fossils

    absolute age by chemical composition (radioactive isotopes)

    relative age by depth of rock layers

 

 Patterns

    different species appear at different times in the fossil record

    some species go extinct

Based on "descent with modification" what should appear first:  complex or simple forms? 

                                                 First appearance in fossil record (millions of years ago)

Prokaryotic cells                                                                        3500

Protists                                                                                      1800

Multicelled eukaryotes                                                                1000

Vertebrates                                                                                  550