Transcript Darwin`s Theory of Evolution

What does each picture show? What is the same in the pictures?
The Theories of Evolution
Species change over time!!!
K-W-L
– Write everything you already know about
evolution in the K column
– Write everything want to know about evolution
in the W column
– Leave the L column blank for know, but fill it in
each day at the end of class
What Do We Know?
• Evolutionary theory helps biologists understand
how fossils fit into life’s history and how natural
selection shapes our world today.
• Evolution explains how bacteria became
resistant to antibiotics, how new diseases arise,
and how insects become resistant to pesticides.
• Modern genetics is helping biologists determine
the relationships among the different groups of
organisms on Earth.
What We Want to Learn?
• Can evolutionary theory help predict which
strains of diseases, such as influenza and
tuberculosis, will be most deadly next year?
• What will the study of fossils and genes reveal
about the early evolution of the major groups of
plants and animals?
• Will studying the mass extinctions of the past
help scientists find ways to protect biodiversity
today?
• What new organism will be discovered as a
result of the current efforts to classify and catlog
all of life’s diversity?
To Summarize it up…
• Species evolve (change) over time.
• Evolution is the consequence of the interactions
of
– (1) the potential for a species to increase its numbers
– (2) the genetic variability of offspring due to mutation
and recombination of genes
– (3) a finite supply of the resources required for life
– (4) the ensuing selection by the environment of those
offspring better able to survive and leave offspring
Evolutionary Foundation
• Hutton and Lyell helped scientists recognize that Earth is
many millions of years old, and the processes that
changed Earth in the past are the same processes that
operate in the present.
• Lamarck proposed that by selective use or disuse of
organs, organisms acquired or lost certain traits during
their lifetime. These traits could then be passed on to
their offspring. Over time, this process led to change in a
species = Adaptation
• Malthus reasoned that if the human population continued
to grow unchecked, sooner or later there would be
insufficient living space and food for everyone.
Introducing Evolutionary Theory
• We share Earth with millions of other organisms
(variety of living things) = Biological Diversity
– How is everything so different?
• Evolution = change over time leading to modern
organisms that have descended from ancient
organisms
• Theory = well-supported testable explanation of
phenomena that have occurred in the natural
world
Introducing… Charles Darwin!
• In 1831, Darwin set sail on the Beagle for a voyage
around the world
• During his travel, Darwin made numerous
observations and collected evidence that led him to
propose a revolutionary hypothesis about the way
life changes over time = The Theory of Evolution
• Darwin used these observations to scientifically explain
the diversity of life on this planet.
Darwin’s observations
• Darwin was interested in the diversity of organisms in
specific areas and the specific locations species
inhabited
– How are there so many different organisms and why
do they live in specific areas?
• He also found fossils of the past that resembled present
day organisms
– Why did they disappeared and were they related?
• He was fascinated by the differences on the Galapagos
islands
– Why were these close islands inhabited by similar
organisms that appeared slightly different?
The Galapagos Islands
• Darwin observed that the characteristics of many
animals and plants varied noticeably among the different
islands.
– Did these species evolve from a common ancestor
after being isolated to different islands needing
different survival skills?
Pinta Island
Intermediate
shell
Hood Island
Saddlebacked shell
Isabela Island
Dome-shaped shell
The Controversy
• Darwin brought some specimens back and
studied them, soon realizing that they
were separate species that did not exist
anywhere else in the world!
– These species were clearly different from
mainland species and from one another.
• In 1859, Darwin published a book: On the
Origin of Species about species diversity
and evolution (natural selection) that
would change how we view the world!
Natural Variation & Artificial Selection
• Natural Variation = differences among individuals of a
species
– Variations can be inherited from one generation to the
next
• Selective breeding = humans select desirable traits and
breed based on natural variation (to improve
crops/farms)
– Darwin called this artificial selection = nature provides
variation among different organisms, and humans
select variations they found useful.
– What is the difference between natural variation and
artificial selection?
Evolution by Natural Selection
• Living things evolve as the result of:
– The struggle for existence
– The survival of the fittest
– The descent with modification
Peacock tail evolution:
http://www.pbs.org/wgbh/evolution/library/01/6/l_016_09.html
Struggle for Existence
• Darwin was convinced artificial selection worked
in nature as the result of overproduction and
competition for resources = struggle for
existence (members of each species compete
regularly to obtain food, living space, and other
necessities of life)
– Depends on an individual’s ability to survive
and reproduce = fitness
– Fitness results from adaptations = inherited
characteristics that increase an organism’s
chance of survival
– = “Survival of the Fittest!”
Natural Selection
• Survival of the fittest = Natural Selection!
– Traits are being selected and increasing over
time (over many generations without human
influences)
• Over time, natural selection results in
changes in the inherited characteristics of
a population. These changes increase a
species’ fitness in its environment.
Descent with Modification
• Over time, natural selection
produces organisms with
different structures or functions
resulting in species that look
different from their ancestors
– Each living species has
descended with changes
from other species over time
= Descent with
Modification
• Then, all living things must be
related!
– There’s a common ancestor
of all living things =
Common Descent
Evidence of Evolution
• Living things have been evolving on Earth
for millions of years. Evidence of this
process could be found in:
– The fossil record
– The geographical distribution of living species
– Homologous structures of living organisms
– Similarities in development
Fossil Record
• Remember: Fossils are
the remains of ancient
life and different layers
of rock were formed at
different times.
• Fossils in different layers
of rock are evidence of
the gradual change over
time (different species
appeared, lived for a
time, and then vanished)
Geographic Distribution
• Populations in different
places adapted to different
environments… different
species descended with
modification from a
common ancestor.
• Different species living in
similar environments in
different parts of the world
sometimes have similar
structures and functions
because they experienced
similar pressures of natural
selection
Homologous Structures
• Some vertebrates have similar bone structures that
develop from a specific group of cells in an embryo, but
the structures adapted different functions so the
organism can survive in different environments
providing evidence of descent with modification from
common ancestors
• Homologous Structures = they appear and function
differently, but develop from the same embryonic tissues
• Some homologous structures provide little or no function
in some organisms = vestigial organs
Similarities in Development
• Embryos of many
vertebrates look very
similar in the early
stages of
development.
• The same groups of
embryonic cells
develop in the same
order and in similar
patterns producing
homologous
structures
Summary of Darwin’s Theory
• Individual organisms in nature differ, and some variation
is inherited
• Organisms in nature produce more offspring than can
survive and reproduce
• Members of each species compete for limited resources
• Unique organisms have different advantages and
disadvantages in the struggle for existence
• Individuals best suited to their environment survive
and reproduce, passing the characteristic to their
offspring. Individuals without the characteristic die
• Species change over time due to natural selection…
new species arise and others disappear
• Species alive today have descended with modification
from species of the past
• All organisms on Earth are united by a common
descent