Transcript Chapter 5, Section 1 Darwin’s Voyage

Chapter 5, Section 1
Darwin’s Voyage
Wednesday, January 6, 2010
Pages 146 -- 156
Objectives
State how Darwin explained variations
among similar species.
Explain how natural selection leads to
evolution, and explain the role of genes
in evolution.
Describe how new species form.
Vocabulary Words
Species
Adaptation
Evolution
Scientific theory
Natural selection
Variation
Who is Charles Darwin?
QuickTime™ and a
decompressor
are needed to see this picture.
He was a scientist who
came up with the idea
of evolution by natural
selection.
Ideas began when we
worked as a young
naturalist aboard a
British naval ship.
His travels brought him
to the Galapagos
Island.
Darwin’s Observations
The voyages brought Darwin to many
interesting places such as Argentina and the
Galapagos Islands.
Darwin was amazed at the diversity of living
things he saw.
Today, there are over 1.7 million species of
organisms on Earth.
A species is a group of similar organisms that can
mate with each other and produce fertile
offsprings.
Similarities and Differences
While on the Galapagos Island, Darwin
noticed that many of the plants and
animals were the same as those
organisms found on the mainland.
Even though many of the plants and
animals, there were slight differences.
Small vs. large claws.
Shape of the shells on the tortoises
Adaptation
An adaptation is the
ability of an
organism to take on
a trait that will help it
survive and
reproduce.
Example: The size
of a bird’s beak.
QuickTime™ and a
decompressor
are needed to see this picture.
Evolution
Evolution is the gradual change in a
species over time.
Darwin thought that species gradually
changed over many generations and
became better adapted to the new
condition.
Darwin’s ideas are often referred to as the
theory of evolution.
A scientific theory is a well-tested concept that
explains a wide range of observations.
Natural Selection
Darwin published a book called The
Origin of Species in 1858.
This book proposed an explanation for
how evolution occurs.
Darwin explained that evolution occurs
by means of natural selection.
Natural Selection -- cont’d
Natural selection is a process by which
individuals are better adapted to their
environment and these individuals are more
likely to survive and reproduce than other
members of the same species.
Factors that affect the process of natural
selection are:
Overproduction, competition, and variations.
Over time, natural selection can lead to
evolution. Helpful variations gradually
accumulate in a species, while unfavorable
ones disappear.
Role of Genes in Evolution
Without variations, all the members of a
species would have the same traits.
Evolution by natural selection would not
occur because all individuals would
have the same chance of survival.
Variations come from mutations in
genes.
How do New Species Form?
New species may come about from
separation from the rest of its species.
Once a group is isolated, members of
the isolated group can no longer mate
with members of that species.
These separated members might be
away for so long that different traits
evolve.
Continental Drift
Continental drift affected the evolution
of species.
Evident when examining the fossils
from various continents.
The split of Pangaea accounts for
species being separated from one
another and caused them to evolve
independently.
Homework
Workbook 5.1 (1/8)
Worksheet 5.1 (1/7)
Vocabulary quiz 5.1 (1/8)