EVIDENCE THAT CHALLENGED THE EVIDENCE THAT CHALLENGED THE ASSUMPTION THAT LIFE IS STATIC ASSUMPTION THAT LIFE IS STATIC

AND UNCHANGINGAND UNCHANGING

Evidence for Change in the Patterns Evidence for Change in the Patterns of Life’s Biodiversity Over Time and of Life’s Biodiversity Over Time and

the Relatedness of Speciesthe Relatedness of Species

BIOGEOGRAPHY – The study of the BIOGEOGRAPHY – The study of the distribution of organisms that live on the earthdistribution of organisms that live on the earth

• Biodiversity is High!– At least 1.75 million species

on earth have been described and given names.

– Approx. 1,000,000 animals, ¾ of which are insects

– Approx. 250,000 plants – Approx. 69,000 to 100,000

fungi

• About 10,000 new species are reported each year – On internet visit:

http://www.wwf.org.hk/eng/pdf/references/factsheets/factsheet1.PDF

Marsupials and Placental Mammals Marsupials and Placental Mammals and their Ecological Counterpartsand their Ecological Counterparts

African Euphorbs and the American African Euphorbs and the American Cactus: Ecological CounterpartsCactus: Ecological Counterparts

Comparative Anatomy: EmbryologyComparative Anatomy: Embryology

• Human embryos have pharyngeal arches, a two-chambered heart, and a tail which disappears before birth!  – Pharyngeal arches in fish

develop into the gills and the jaw. 

– In humans, pharyngeal arches do not develop into gills, but into the lower jaw, hyoid bone, and larynx

Comparative Anatomy: EmbryologyComparative Anatomy: Embryology• Cat and human

embryos in the tail bud stage. A cat embryo is shown on top, a human embryo below. Note the post-anal tail in both, positioned at the lower left below the head of each. The human embryo is about 32 days old.

Comparative Anatomy: Vestigial StructuresComparative Anatomy: Vestigial Structures

Comparative Anatomy: Comparative Anatomy: Homologous StructuresHomologous Structures

Fossil RecordFossil Record• Nicolaus Steno - published a work in

1669 dealing with the question of "Why is a solid in a solid?" 

• He was puzzled by the existence of 'tongue stones' which were found embedded in rock, but which bore a strong resemblance to sharks teeth. 

• He proposed that some forms of rock (sedimentary rock) were not always hard but were formed by from a slurry of mud, rock, sand, and other materials which had encased teeth from sharks before some geological process had transformed the entire lot into stone.

• He was one of the first people to recognized that fossils were the castings and/or physical remains of life forms that had existed in the past.

• For more information see Gould, S. J., 1983. The titular bishop of Titiopolis. Chapter 5 in Hen's Teeth and Horse's Toes, 69-78.

Fossil Record: Extant and ExtinctFossil Record: Extant and Extinct

Artificial Selection: Breeds of DogsArtificial Selection: Breeds of Dogs

Artificial Selection: Varieties of PlantsArtificial Selection: Varieties of Plants

Major Paradigm Shift in Life ScienceMajor Paradigm Shift in Life Science

• By the beginning of the 19th century, it was becoming apparent that species represented potentially changeable or malleable entities.

• Under the proper conditions, pre-existing species might give rise to a new species! 

• If so, change in the pattern of biodiversity of life could occur (A.K.A. evolution).

• If evolution (at the time called transmutation) did occur then by what mechanism?

• Entering the fray during the 18th and 19th centuries: Georges Buffon, Erasmus Darwin, Jean-Baptiste Pierre Antoine de Monet, Chevalier de Lamarck, Charles Lyell, Charles Darwin, and Alfred Wallace.