Download Change through Time…………… …Evolution.. Chpt 17/18

Chapter 13
The Theory of Evolution
Jean Baptist de Lamarck
• Theory of Acquired Characteristics –
– features increased in size because of use
or reduced in size because of disuse!
– these acquired traits are passed to
offspring
– change in species are due to the physical
conditions of life ( environment)
– NOT TRUE!
Charles Darwin
– A Naturalist who, in 1831, traveled on the
“HMS Beagle” for a five year expedition
to collect, study, and store biological
specimens discovered.
• Father of the Theory of Evolution
Alfred Russel Wallace
• Studied the birds of Malaysia and
hypothesized the same Theory of Natural
Selection as Darwin.
• Darwin then published his earlier works.
Darwin’s Pigeons
• Artificial Selection - By
breeding pigeons that had a
desirable trait, the offspring
would carry these same traits.
• Natural Selection - Nature
selects or chooses which traits
in an organism will be passed on
to future generations.
•
Darwin’s Theory of
1. Variations exist within Natural Selection
populations.
• 2. Some variations are
more advantageous than
others.
• 3. Organisms produce
more offspring than can
survive.
• 4. The “fittest” survive
and reproduce! Thus the
species modifies itself
over time. (Nature
selects who lives.)
• Darwin observed
islands with great
biodiversity.
• Organisms were best
suited for their own
particular climate.
The Galapagos Islands
• Island organisms
seemed to have adapted
to each particular island
climate.
• After 22 years of data
analysis, Darwin
formed his Theory of
Adaptation by Natural
Selection.
Adaptation
Adaptation is the evolutionary process whereby a
population becomes better suited to its habitat.
This process takes place over many generations.
• Populations adapt as the environment changes.
Types of Adaptions:
1. Structural-outward look, appearance, body part
2. Behavioral-mating, food gathering
3. Physiological-internal to the organism
Structural Adaptations
1. Mimicry-A structural adaptation that provides
protection by enabling an organism to copy another
species.
(Monarch, original/poisonous and Viceroy, copy/harmless)
--coloring is a warning to other organisms “Stay away!”
2. Camouflage- A structural
adaptation that enables the
organism to blend in with its
environment.
( Peppered Moths and Leaf Bugs)
Behavioral Adaptations
Behavioral adaptations help an organism to enhance survival
or reproduction by making a change to their behavior.
• Mobbing birds- the mob may protect their young from
predators by confusing them.
• Migrating waterfowl- have access to abundant food all year
round by migrating.
• Mating Calls- Certain species of female frogs prefer males
with long breeding calls, because males with long calls have
better breeding habitats.
• Nesting Sites- Ground squirrels that select optimum nesting
habitats can have a greater proportion of their young
survive.
Physiological Adaptations
A physiological adaptation is an adaptation in
which the organism changes internally (in its
cells/tissues) due to a very specific and direct
stimuli.
Ex: Bacteria that have developed a resistance to
antibiotics--Tuberculosis
Physiological Adaptations
Other Examples Include:
• Camel urine—it is extremely concentrated to
reduce water loss (desert dwelling animal)
• Callouses on fingers—hardened skin tissue to
lessen pain and feeling within an area of
overuse
• Tanning of skin—response to long periods
of time in the sun
Biological Molecules
• Proteins Sequences–
few changes in amino
acid sequences share
common ancestors.
• DNA Sequences –
Similar gene
sequences show
evolutionary ancestors.
Points of Evidence for Evolution
1. Fossil Record – Past History
2. Anatomical Studies – similar body parts
– Homologous structures - Modified structures seen among
different groups of descendents. Have a common
ancestor.
•
–
Whale fin and human arm (similar bone structure,
different function)
Analogous structure - Body part similar in function but
different in structure. Do NOT have a common ancestor.
•
Butterfly wing and bird wing (function is the same, but
structure is different)
Homologous
Structures
Yes
Common
Ancestor
Analogous
Structures
NO
Common
Ancestor
Vestigial Organs
3. Vestigial Organs - Structures that have no
function in the organism today but may
have been used at an earlier time in life.
Examples in humans: Appendix, tailbone,
wisdom teeth
http://www.livescience.com/animals/top10_vestigial
_organs-1.html
Embryological Development
4. Embryological development - Organisms that
develop similarly as embryos have an evolutionary
relationship.
Example: vertebrate embryos-have tails and gill slits
Embryological
Development
Mechanisms of Evolution or
Natural Selection
• Reproductive
Isolation- Occurs
when a population is
separated by
geographic , mating,
or reproductive
changes.
• Can no longer breed
successfully.
Grand
Canyon
Squirrels
Geographic
Isolation
Speciation
• The formation of a new species from an ancestor.
• Occurs if inter-breeding or the production of fertile
offspring is prevented from forming subspecies.
Divergent Evolution - An ancestral species evolves
into many different species (Adaptive Radiation)
Ex. Vertebrate limbs
Convergent Evolution -Distantly related organisms
evolve similar traits.
Ex. whales and fish
Speciation
• Speciation can occur quickly or slowly.
• Gradualism- Species originate through a
gradual accumulation of adaptations.
• Punctuated Equilibrium - Occurs in rapid bursts
with long periods of stability in between.
Changes in Genetic Equilibrium
• Genetic equilibrium - Allele
frequencies do not change over time
(non evolving)
3 Ways Evolution Occurs.....
1) Mutations - Cause genetic changes
in gene pool
2) Genetic Drift - Changes due to
chance events (Small populations)
3) Gene flow - Movement of genes
into or out of a population