Biodiversity
Biogeography






Geography 210: Physical Geography and Environmental Issues
The Creation by Michelangelo
Natural Selection
Organisms that have characteristics better suited to the environments they are in survive better, as do their offspring, given that the parents’ traits are inherited.
Taller giraffes, faster cats, smarter hunters, can get more food, survive
Pests become resistant to pesticides
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Idealized relation of an island’s size, distance from the mainland, and number of species.
© 2003 John Wiley and Sons Publishers
The main bio-geographic realms for animals are based on genetic factors.
In each biogeographic realm, certain families or orders are dominant.
© 2003 John Wiley and Sons Publishers
The major vegetation realms are also based on genetic factors.
Plate Tectonics
Continents in motion
Divergent Evolution
Ostrich – Africa
Rhea – South America
evolution from a common ancestor
Evolution of Life on Earth
Past history from fossils and other stratigraphic deposits
Earliest beginnings: microorganisms
Early evolution was slow
2 B y b p for 1st organisms.
Bacteria
2-0.4 B y b p – the age of plants
0.5 B y b p – first critters, mussels, trilobites
0.2 B y b p – proto human
Fig 7.8 The stomach of a reindeer illustrates complex symbiotic relationships.
Symbiosis
“living together”
© 2003 John Wiley and Sons Publishers
Succession
© 2003 John Wiley and Sons Publishers
Change in the relative abundance of a species over an area or a distance is referred to as an ecological gradient.
Biogeographer, Dr. Keith H. Topps, Nipissing University, Ontario, Species Replacement at an Alpine Treeline, Top of the World Highway, Yukon, Canada
All organisms are adapted to the environment in which they live
Support: Fossils
Support: Fossils
Earliest fossils were prokaryotes
Appeared in fossil record about 3.5 billion years ago
Chronological Appearance of Vertebrates
Support: Fossils
Whales have forelegs in the form of flippers, however, they also have vestigial hind-leg and foot bones that do not extend from their body
Fossils link past and present
Support: Fossils
Basilosaurus is an extinct whale that had hind-legs
These also are vestigial legs as the ancient whale was an aquatic animal
Other Support: Comparative Anatomy
Comparative Anatomy: comparison of body structures in different species
Anatomical similarities among many species give signs of common descent
Other Support: Molecular Biology
Artificial Selection
German shepherd
Yorkshire terrier
English springer
spaniel
Mini-dachshund
Golden retriever
Hundreds to
thousands of years
of breeding
(artificial selection)
Ancestral dog
Natural Selection
African wild
dog
Coyote
Fox
Wolf
Jackal
Thousands to
millions of years
of natural selection
Ancestral canine
Natural Selection in Action
Chromosome with gene
conferring resistance
to insecticide
Additional
applications of the
same insecticide will
be less effective, and
the frequency of
resistant insects in
the population
will grow
Survivor
Insecticide
application
Microevolution
Chromosome with gene
conferring resistance
to insecticide
Gene pool changes
as most alleles
that do not confer
insecticide resistance
are removed
Survivor
Insecticide
application
Causes of Microevolution
Bottleneck effect: genetic drift that results from event that drastically reduces population size
Causes of Microevolution


Founder effect: random change in gene pool that occurs in a small colony of a population
A type of genetic drift
Over time, random changes in allele frequencies will continue until population is large enough that genetic drift is minimal
Variation is extensive in populations
2 morphs of California King Snake