Download Chapter 16 Evolution - Red Hook Central Schools

Chapter 16
Evolution
Darwin’s Voyage
• Charles Darwin
• 1809 – 1892
• A naturalist aboard the
HMS Beagle in 1831
• Believed that favorable
variations in an organism,
no matter how slight,
enabled the organism to
survive and pass the trait
to offspring
Patterns of biodiversity:
• Species Vary Globally
– Emu - Australia
• Ostrich - Africa
• Rhea – South America
Species vary locally
Species Vary Over Time
• Glyptodont – prehistoric amadillo
• Armadillo
Natural Selection
• a process by which organisms with
variations most suited to their local
environment survive and reproduce;
– Artificial Selection: humans select variations
in organisms that they find the most useful
Overproduction
• in some populations, more organisms are
born than can survive (struggle for
existence)
– Interesting info about overproduction:
– 1:1000 logger-head turtles survive to
reproduce
– 99% of the 23,000 acorns in a California
forest rot or were unable to produce a single
live oak tree
Adaptability and Variations
• Variations: any difference between
members of the same species
• Adaptations: an inheritable characteristic
that increases an organism’s ability to
survive and reproduce
• Differences in adaptations affect an
individual’s fitness, how well it can survive
and reproduce – survival of the fittest
Natural Selection and Evolution
• Some variations make an organism better
adapted to its environment. The alleles for
these variations are more likely to be passed
on to the next generation. Thus, natural
selection can lead to evolution.
• Principle of Common Descent: all species
(living and extinct) are descended from
ancient common ancestors
Chapter 16.4
Evidence of Evolution
Biogeography
• The study of where organisms live and
where their ancestors lived in the past
• Patterns in biogeography:
– Organisms that are closely related have
differences due to where they live
– Organisms that are not related but live in the
same area develop similar characteristics
Top two organisms: The hedgehog (left) and the tenrec (right) are lookalikes from widely separated branches of the tree of life.
Bottom two organisms: The mole (left) and the golden mole (right) are also lookalikes from widely separated branches of the tree
of life.
Fossil Records
• Earth is about 4.5 billion years old –
indicated by radioactive dating of rocks
and fossils
• In the 1800s the fossil record wasn’t as
extensive as it is today
• Many fossils have been found that bridge
the gaps between ancient and modern
organisms, making an more complete
fossil record.
Anatomy and Embryology
• Homologous Structures: structures that
organisms share that have been inherited
by a common ancestor – not common in
function necessarily
– Scientists study physical structure (anatomy),
the way the structure developed during
embryo stage, and pattern that these
structures appeared in evolutionary history
Analogous Structures
• Analogous structures
are those that are
similar in function but
not in structure.
– Wings of various
animals
Vestigial Structures
• Structures that are inherited from an
ancestor but have little or no function
• Why retain these?
– Structures have no bearing on an organism’s
fitness, so these structures are not eliminated
– Human appendix
– Wings of flightless birds
– Hipbones for terrestrial locomotion in aquatic
mammals
Embryology
• Support for evolution
from patterns of
embryonic
development
Genetics, Molecular Biology, &
Evolution
• Support for Darwin’s Theory comes from
genetics, the study of heredity
• Variation – from which natural selection
operates – caused by mutations and
“reshuffling” of genes during sexual
reproduction
• Universal genetic code and homologous
molecules (proteins) provide evidence of a
common ancestor
Video
http://video.pbs.org/video/1300397304/