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Transcript
Evolution
What Darwin Never Knew
Evolution
 Evolution
 Change over time
 Modern organisms have
descended from ancient
organisms.
Evolution Myths
 Man evolved from monkeys.
 Evolution does not state that man evolved from monkeys. It states
that we shared a common ancestor.
 Darwin came up with the theory of evolution.
 The theory existed before Darwin
 Evolution is JUST a theory:
 A well supported, testable explanation of phenomena that
have occurred in the natural world.
Charles Darwin
 Born: 1809 in England
 Religious Beliefs:
 Darwin was a Christian for a majority of his life and later
became an agnostic.
Voyage of the Beagle
 Voyage of the Beagle
 Darwin set sail for 5 years on the H.M.S. Beagle in 1831
 While on the Beagle, Darwin made several observations and
inferences that lead him to develop his theory of evolution.
Patterns of Diversity
 Darwin was surprised at:
 how many plants and animals seemed well-suited for
their environments.
 how different organisms were in similar ecosystems of
different continents.
Charles Darwin
 Born in England – 1809
 Sailed on the HMS Beagle’s five-year voyage mapping
the coastline of South America.
 Observed and recorded characteristics of species on the
trip
 Developed a scientific theory of biological evolution explains how modern organisms evolved over long
periods of time through descent from common
ancestors.
 Wrote On the Origin of Species
 Darwin's Finches
Darwin’s 3 patterns of biodiversity
 Species vary globally
 Species vary locally
 different, yet related, animal species often occupied
different habitats within a local area
 Species vary over time
Species vary globally
 Different, yet ecologically similar, animal species
inhabited separated, but ecologically similar, habitats
around the globe
 found flightless, ground-dwelling birds that were similar on
different continents.
 South America = rheas
 Africa = ostriches
 Australia = emu.
Species vary locally
 Different, yet related, animal species often occupied
different habitats within a local area
 Galapagos Islands – the shape of the tortoises’ shells corresponds to
different habitats.
 Isabela Island has high peaks, is rainy, and has abundant vegetation
that is close to the ground. A tortoise from Isabela Island has a domeshaped shell and short neck.
 Hood Island, in contrast, is flat, dry, and has sparse vegetation. A long
neck and a shell that is curved and open around the neck and legs
allow the Hood Island tortoise to reach sparse, high vegetation.
Species vary over time
 Darwin collected fossils = the preserved remains or
traces of ancient organisms.
 Darwin noticed that some fossils of extinct animals
were similar to living species.
 He discovered fossils of Glyptodont
where armadillos currently live.


Why did Glyptodont disappear
Why did they resemble armadillos?
Scientists who shaped Darwin’s
thinking
 Hutton and Lyell - geologists
 The earth is extremely old
 Processes that changed the past are the same that
operate in the present
Scientists who shaped Darwin’s
thinking etc.
 Lamarck – Although his ideas were
FLAWED they shaped Darwin’s thinking
 Organisms could change during their
lifetimes by selectively using or not using
various parts of their bodies
 Individuals could pass these acquired traits
on to their offspring, enabling species to
change over time.
 Organisms have an inborn urge to become
more complex and perfect, and to change
and acquire features that help them live
more successfully in their environments.
Scientists who shaped Darwin’s
thinking etc.
 Malthus = if the human population grew unchecked,
there wouldn’t be enough living space and food for
everyone
 War, famine and disease would work against population growth
 Darwin realized that most organisms don’t survive and
reproduce, he wondered which individuals survive…and
why?
Artificial selection
 Artificial selection = process in which nature provides
the variations, and humans select those they find
useful.
 Darwin put artificial selection to the test by raising and
breeding plants and fancy pigeon varieties.
16.3 Natural selection
 Natural selection = the process by which organisms
with variations most suited to their environment
survive and leave more offspring
 Natural selection occurs when there is
 1) A struggle for existence – more offspring are produced
than can survive
 2) Variation and adaptation
 3) Survival of the fittest
1) Struggle for existence
 Grasshoppers can lay more than 200 eggs at a time,
but only a small fraction of these offspring survive to
reproduce.
2) Variation and Adaptation
 Adaptation = heritable characteristic that increases an
organism’s ability to survive and reproduce in its
environment
 EX. Green color is an adaptation: The green grasshoppers
blend into their environment and so are less visible to
predators.
3) Survival of the Fittest
 Fitness = the ability of an organism to survive and
reproduce
 Because their color serves as a camouflage adaptation, green
grasshoppers have higher fitness and so survive and
reproduce more often than yellow grasshoppers do.
Natural Selection
 Green grasshoppers become more common than
yellow grasshoppers in this population over time.
 More grasshoppers are born than can survive
 Individuals vary in color and color is a heritable trait
 Green grasshoppers have higher fitness in this
particular environment
Natural Selection
 Natural selection does not make organisms “better”.
 It is a process that enables organisms to survive and
reproduce in a local environment.
 If local environmental conditions change, some traits
that were once adaptive may no longer be useful
 Salamander Evolution
Principle of common descent
 According to the principle of common
descent, all species—living and
extinct—are descended from ancient
common ancestors.
 Darwin proposed that, over many
generations, adaptation could cause
species to evolve into new species.
 He also proposed that living species
are descended, with modification,
from common ancestors—an idea
called descent with modification.
Evidence for Evolution
Age of the Earth and Fossils
 Radioactive dating of rocks
indicate that Earth is about
4.5 billion years old—plenty
of time for evolution by
natural selection to take
place.
 Since Darwin,
paleontologists have
discovered hundreds of
fossils that document
intermediate stages in the
evolution of many different
groups of modern species
Evidence for Evolution
Homologous Structures
 Homologous Structures – structures that are shared by
related species and are inherited from a common
ancestor
 For example, the front limbs of amphibians, reptiles,
birds, and mammals contain the same basic bones.
Evidence for Evolution
 Vestigial structures are inherited from ancestors,
but have lost much or all of their original function due
to different selection pressures acting on the
descendant.
 Ex. hipbones of bottlenose dolphins
 In ancestors, hipbones played a role in terrestrial
locomotion. As the dolphin lineage adapted to life at sea,
this function was lost
 Why would an organism possess structures with little
or no function?

The presence of a vestigial structure does not affect an
organism’s fitness. Natural selection would not eliminate it.
Evidence for Evolution
Embryology
 Similar patterns of embryological
development provide evidence that
organisms have descended from a
common ancestor.
 Researchers noticed a long time ago
that the early developmental stages of
many animals with backbones (called
vertebrates) look very similar.
 PBS embryology clip
 Which Embryo?
Evidence for Evolution
Genetics & Molecular Biology
 At the molecular level, the
universal genetic code and
homologous molecules provide
evidence of common descent.
 DNA and RNA carry
information from generation to
generation and to direct protein
synthesis
 Similar genes and proteins are
found in many organisms

Hox genes – determine the headto-tail axis in embryonic
development
Classification
Why Classify?
 The goal of systematics is to organize living things
into groups that have biological meaning
 By using a scientific name, biologists can be sure
that they are discussing the same organism.
 Ex. cougar, puma, panther, and mountain lion can all
be used to indicate the same animal— Felis Concolor.
Linnaean Classification System
 Organizes living things into groups (taxa) that have
biological meaning
 Linnaeus grouped species according to anatomical
similarities and differences
• Linnaeus’s classification system includes seven
hierarchical taxa: species, genus, family, order, class,
phylum, and kingdom.
Classification
Binomial Nomenclature
 Linnaeus developed a two- word naming system in the
1730s= binomial nomenclature
 The scientific name is written in italics
 The first word begins with a capital letter
 The second word is lowercase
 EXAMPLE : Genus species
 Polar bear = Ursus maritimus
Dichotomous Key
 Used to identify organisms
 Consists of paired statements that describe
alternative characteristics for an organism.
Problems with Traditional
Classification
 Organisms that look alike are not always the most
closely related
 Which two are most closely related?
Dolphin
wolf
shark
Cladogram
• Cladogram = illustrates how groups of organisms are
related to one another by showing how evolutionary
lines, or lineages, branched off from common ancestors.
The 6 Kingdoms
The 3 Domains
 Genetic analysis shows the two prokaryotic
kingdoms are more different from each other, and
from eukaryotes
 Domain = a larger, more inclusive category than a
kingdom.
The Tree of Life