Biology 1004: Evolutionary Biology
What is Science?
▯science is a way of understanding the natural world based on observable and measurable evidence
Evidence is interpreted through logic
Assumptions: help us learn about the natural world from evidence
Characteristics of Science
▯Scientific conclusions are reliable (ie. founded on facts) but are not TENTATIVE [not certain] (ie.
Subject to scrutiny)
Science is not democratic but is non dogmatic
• Scientific theories are not voted upon by accepted or rejected based on the amount of
• Ideas are accepted based on scrutiny not based faith.
• Biologists don't believe in a scientific theory but they rather accept it if it is useful to
understand the natural world.
• A Hypothesis would be valid, if there was data to support. Essential a theory if first
created through observations ▯hypothesis assumption about the nature of something
(prediction a guess about an outcome) ▯test through experiments ▯collected data. The
hypothesis would not be true if the data did not supported, theory would be invalid.
• Explanation based on first principled (undeniable facts) or from lots of measurable evidence.
• Theory are subject to modification or replacement as new evidence is gathered.
3 Important qualities of a Scientific Theory:
1. Explain the past and present
2. Predict the future
3. Better explain observation than alternative theories.
Scientific theories are problem solving tools
• Bacteria / Diseases are known to evolve throughout the generations , Rhinovirus is less dangerous
because our body have evolved to protect ourselves from it (immune system) • Cholera is more dangerous since it doesn't need alive host to travel, it can be cause through
• The study of evolution
the process responsible for the changes in the heritable traits of population among generations
Large temporal changes in diversity (macroevolution).
Burgess Shale–type (BST) biotas are of critical importance to understanding the early evolution
of the. The great majority of species preserved in BST deposits lack biomineralized tissues.
Preservation of softbodied organisms is rare in the geologic record and BST deposits provide a
record of early Phanerozoic biodiversity otherwise unknown.
Types of Evidence
• Fossils are relics or impressions of ancient organisms
• Most fossils are found in layers (strata) of sedimentary rock
• Living and recently extinct species in the same area resemble each other
• The fossil record traces history of life and allows us to study history of particular organisms
• Through radioactive dating, geologists estimate the age of the earth at about 4.6 billion years
o Law of succession: general patters of correspondence between fossil and living forms from
the same local area.
• Mammalian traits
o Mammals glands
o Jaw structure
• Unique traits
o No hind limbs
o No hairs
o Nostrils (blow hole)
o Located on top of the head
• Fossils contain transitional forms between living and extinct species o Ambulocetus (5048 MYA) are Fully Aquatic but possesses hind limbs
o Terrestrial / semiaquatic mammals chare more features with whales that with any other
E.g. Auditory bulba and the inner hear bone
o Indohyus (48 MYA)
o Semi aquatic
Not whale but shares features of both whales and artiodactyles (even hoofed
ungulates e.g. hippos, pigs, camels)
o As fossils get younger, they show more similarities with living whales
o Completely aquatic lifestyle
o Modification of the nostrils into a blowhole
• Vestigial Structures: are remains of a structure that is no longer functional but show common
o Example: Humans have a tailbone but no tail
o Reduction of the pelvic bones (vestigial in current whales)
o Limb buds in snakes
• Embryological Evidence: During development, all vertebrates have a postanal tail and paired
• Developing organisms show ancestral features.
• Organisms that show similarities in their embryonic development may have a common ancestry
• Organisms have anatomical similarities when they are closely related because of common descent
• Homologous structures in different organisms are inherited from a common ancestor have similar
• Is like the blueprint for development
MORPHOLogicAL HOMoLogies AND molecuLAR homologies.
• Example : Vertebrate forelimbs contain the same sets of bones organized in similar ways, despite
their dissimilar functions
**HOWEVER; similarities aren't always due to ancestry
• E.g. Marsupials are more related to kangaroo than squirrel ▯Like bats they're wings derive from
finger not arms like birds.
• Another e.g. Wasps and a fly that looks like a bee, to warn predators of they're dangerousness.
• DNA is responsible for the similarity and differenced between living entities
o All living organisms have DNA & the same genetic code (i.e. same codon get translated
in the same amino acids)
• Similarities in DNA sequenced can be used to infer relatedness among species o E.g. Extinct whales have ankle bones that are only found in artiodactyles
o DNA and morphology tell the same story
• Recognized that the Earth is older that proposed by the bible.
• Species are not immutable and can change over time.
• Did not propose a mechanism of change
JeanBaptiste Lamarck (1744 – 1829)
• -Said species adapt to changing environment, and has some role in evolution
• Simple organisms are produced by spontaneous generations. And can evolve into more complex
• First naturalist to propose a mechanism for evolution: Inheritance of acquired characteristics.
Lamark's Principle of Use and Disuse.
• Rejected early on but resurrected in the early late 1800 as an alternative to Darwin's theory
• Voyage of the beagle (18311835): collected specimen (plants, animals, fossils, rocks, from
around the world.
o Started noticing the variation in bird species, around islands.
o Species must be changing.
• Developed the theory of evolution by natural selection for the next 20 years
• The origin of species was published in 1859.
Alfred Russell Wallace (1823 1913)
• Naturalist and Explorer
• Independantly developed the theory of evolution by natural selection
• The theory was originally presented by both in 1859 to the Linnean Society before the Origin was
Natural Selection = Mechanis