Transcript EVIDENCE THAT CHALLENGED THE ASSUMPTION THAT LIFE IS

EVIDENCE THAT CHALLENGED THE
ASSUMPTION THAT LIFE IS STATIC
AND UNCHANGING
Evidence for Change in the Patterns
of Life’s Biodiversity Over Time and
the Relatedness of Species
BIOGEOGRAPHY – The study of the
distribution 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/factshee
t1.PDF
Marsupials and Placental Mammals
and their Ecological Counterparts
African Euphorbs and the American
Cactus: Ecological Counterparts
Comparative Anatomy: Embryology
• Human embryos have
pharyngeal arches, a twochambered 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: Embryology
• Cat and human
embryos in the tail
bud stage. A cat
embryo is shown on
top, a human embryo
below. Note the postanal tail in both,
positioned at the
lower left below the
head of each. The
human embryo is
about 32 days old.
Comparative Anatomy: Vestigial Structures
Comparative Anatomy:
Homologous Structures
Fossil 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 Extinct
Artificial Selection: Breeds of Dogs
Artificial Selection: Varieties of Plants
Major 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.