Transcript Evolution Intro - HRSBSTAFF Home Page

Evolution Intro:
A bit about Darwin
Biology 12
Joke of the day:
Evolution
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Is the process by which modern organisms have
descended from ancient organisms over time
Involves significant changes to the genetic make up
a species over time
Charles Darwin
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1809 -1882
He was an English naturalist.
A keen observer of the
natural world and collected
many different species
He kept meticulous notes of
his observations.
Darwin published his
theory of evolution with
compelling evidence in his
1859 book On the Origin of
Species
Voyage of Beagle
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Date: Feb 12th, 1831
Captain: Charles Darwin
Ship: H.M.S. Beagle
Destination: Voyage around the
world.
Findings: evidence to propose a
revolutionary hypothesis about how
life changes over time
Where did he go?
What did Darwin observe and do?
1. Noted Patterns of Diversity
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Darwin visited Argentina and Australia which had
similar grassland ecosystems.
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Those grasslands were inhabited by very different
animals.
Neither Argentina nor Australia was home to the sorts of
animals that lived in European grasslands.
Darwin posed challenging questions:
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Why were there no rabbits in Australia, despite the
presence of habitats that seemed perfect for them?
Why were there no kangaroos in England?
2. Collected Fossils
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Darwin collected the preserved remains of ancient
organisms (fossils).
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Some of those fossils resembled organisms that were still
alive today.
Others looked completely unlike any creature he had ever
seen.
As Darwin studied fossils, new questions arose:
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Why had so many of these species disappeared?
How were they related to living species?
Example:
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Fossils of extinct animals that resembled animals
present today
3. The Galapagos Islands
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Darwin noted that the different islands had plants
and animals with traits unique to each island
3. The Galapagos Islands
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Giant tortoises varied in predictable ways from one island to
another, the shape of a tortoise's shell could be used to
identify which island a particular tortoise inhabited.
3. The Galapagos Islands
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He noted different species on each island
More of Darwin's observations:
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Homologous structures: common origin but
different functions
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Analogous Structures: similar function but
different origin
Homologous Structures
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Homologous structure are structures that share a common
origin but may serve different functions in modern
species.
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These structures are evidence that organisms with similar
structure evolved from a common ancestor.
Examples include the forelimbs of a variety of mammals.
For example, human, cat, whale and bat.
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These species show the same skeletal elements. Is in the
humerus, radius and ulna.
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However these skeletal elements have been modified over time to
suit the different functions suitable for the type of mammal.
Homologous structures
Analogous Structures
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They serve the same function between organisms
but are different in internal anatomy.
 Such as the wings of birds and butterflies or
the eyes of lobsters and fish.
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These structures are of no use in classifying organisms
or in working out their evolutionary relationships with
each other.
Analogous Structures
Vestigial Organs
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Rudimentary and non-functioning structures that are
homologous to fully functioning structures in other species
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Vestigial organs provide further evidence for evolutionary change
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Examples of these include:
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The human external ear muscles.
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The tail bone.
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Wisdom teeth.
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Some snakes have skeletal limbs.
Sometimes vestigial organs may be adapted for new uses
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Examples: penguin winds can’t be used for flight, yet they are
adapted for swimming.
Theory of Natural Selection
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Observations:
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Individuals within a species vary
Some variability can be inherited
More individuals are born than can survive
Populations of species tend to remain stable in size
Inferences:
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Members of same species compete for survival
Individuals with favorable traits are more likely to
survive and mate
These individuals will contribute more offspring to future
generations therefore increasing favorable trait
To do :
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Read pages 529-533 (section 11.6)
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Answer questions 6 -9 (on page 533)
Looking for Homologies Activity
Peppered Moth Activity
Looking for Homologies Activity