Download ch 13 evidence of and natural selection

Evolution
Descent with Modification
Within a species, each individual has slightly
different characteristics
Natural Selection
Nature chooses who is best suited to live in
each environment
Chapter 13
What is Natural Selection Video
Natural Selection
 Nature decides which organisms are the
best suited for their environment.
 These organisms survive & reproduce
 The stronger, better genes move into the
next generation.
 Survivor Island Lab
 Evolution: “CHANGE over time.”
 Descendents look different than their
ancestors.
Charles Darwin 1809 – 1892
FYI - Three Main Parts of Charles Darwin’s
Life
1809 – 1831: Age 0 - 22
Childhood, education, college
1831 – 1836: Age 22 to 27
Voyaging on the HMS Beagle
1836 – 1882: Age 27 to 73
Scientist and author (geology, experimental and
evolutionary biology - 1859)
Charles Darwin
 Darwin set sail on the H.M.S. Beagle (1831-1836)
to circumvent the world.
 Hired as a naturalist.
 Collected fossils, made sketches and notes on
flora & fauna of the areas he visited
 Galapagos Islands: Darwin observed species
that lived no where else in the world.
 These observations led Darwin to write a book.
The Beagle
Only 90 foot long, but carrying 74 people.
Voyage of the HMS Beagle, 1831 – 1836
Charles Darwin
 Wrote “On the Origin of Species by Means
of Natural Selection”
 Two main points:
1. Species were not created in their present
form, but evolved from an ancestral species.
2. The mechanism for evolution:
NATURAL SELECTION
Many Factors Affect Populations
This Chapter Deals with Natural Selection
 Variation: a difference in a physical trait.
 Galápagos tortoises that live in areas with tall plants
have long necks and legs.
 Galápagos finches that live in areas with hard-shelled
nuts have strong beaks.
 Adaptation: a feature that allows an
organism to better survive in its environment.
- Adaptations can lead to
genetic change in a
population.
– Adaptations do not
“happen.” The species is
already born with the
adaptation.
Evidences of Evolution
1.
2.
3.
4.
5.
Fossil Record
Geographic Distribution of Living Species
Homologous Body structures
Similarities in Embryology
Molecular or Genetic Similarities
Evidence of evolution:
#1: Fossils
 Paleontology is the study of fossils or
extinct organisms.
 Evidence of evolution: fossils
 (relative of whale)
• Darwin found fossils of extinct animals that
resemble modern animals.
 Evidence of Evolution:
#2 Geography
– island species most closely resemble nearest
mainland species
– populations can show variation from one island
to another
 Evidence of Evolution:
#3 Anatomy
– Homologous structures:
– similar in structure but different in function.
– evidence of a common ancestor.
Human hand
Mole foot
Bat wing
Homologous Body Structures
• Not all structures are evidence of a common
ancestor.
– Analogous structures have a similar function.
Human hand
Mole foot
 Analogous structures are not evidence of a
common ancestor.
Fly wing
Bat wing
Structural features are a clue to a species
history.
• Vestigial structures:
remnants of organs or structures that had a
function in an early ancestor.
• Ostrich wings are examples of vestigial structures.
Evidence of Evolution:
#4 Embryology

In their early
stages of
development,
chickens, turtles,
fish and humans
look similar,
providing
evidence that
they probably
shared a
common
ancestry.
Evidence of Evolution:
#5: Molecular and genetic evidence
 Two closely-related organisms will have similar
DNA & protein sequences.
Natural Selection
Or, how did we get here….
Vocabulary
 Species: A group of individuals that
have the potential to interbreed and
produce viable offspring.
 Population: A localized group of
individuals belonging to the same
species. One specie one place.
Vocabulary
 Gene Pool
 The total collection of genes in a
population at any one time.
 Divergence: the accumulation of
differences between species or
populations
Some of Darwin’s Theory
FYI
Organisms change in time, usually very slowly (sometimes
extremely slowly), or evolve. Darwin wrote of “descent with
modification” but the modern term is “evolution.”
All organisms – animals, plants, fungi, all organisms – are
descended from a remote common ancestor.
The main driving force for evolutionary change is natural
selection, the survival of certain traits because they better
adapt the organism for its survival. Natural selection doesn’t
just select against inferior organisms, it selects for superior
organisms and leads to even more superior organisms.
Natural Selection
 Individuals with favorable traits
are more likely to leave more
offspring better suited for their
environment.
Natural Selection - FYI
 How did Darwin come to his idea about
Natural Selection?
 He considered 3 concepts:
1st - FYI
 There is change over time in the flora
(plants) and fauna (animals) of the
Earth
 What we would commonly call ‘evolution’
today
 The fossil record showed this to be pretty
clear, even to people in the mid 1800s
2nd - FYI
 There is a taxonomic (order)
relationship among living things
 People were big into classifying stuff
 It was pretty obvious that there was a
relationship between different species
 Different birds, different grasses, different cats
etc
3rd - FYI
 Adaptation
 Different kinds of teeth for different
animals, say carnivore ripping teeth and
herbivore grinding teeth
 Different tissues within species
 Heart vs. eye etc.
 Differences in beak structures in similar
species
How does it work?
 There is competition among living things
 More are born or hatched, than survive and
reproduce
 Reproduction occurs with variation
 This variation is inherited
 Remember, there was NO genetics back
then, Chucky D knew, he just knew….
 Realized that it wasn’t ‘blending’
How does it work?
 Selection determines which individuals
enter the adult breeding population
1. This selection is done by the environment
2. Those which are best suited, reproduce
3. The strong, survival characteristics are
passed on to the young
How does it work?
 REPRODUCTION is
the key, not just
surviving.
 An organism must
be able to reproduce
to pass on traits to
the next generation.
This lecture keeps
evolving…..
 Survival of the Fittest
 (Chucky D. NEVER said)
 means those who survive tend to
have the most offspring that
reproduce
Summary of Darwin’s Theory
1. Organisms differ; variation is inherited
2. Organisms produce more offspring than
survive
3. Organisms compete for resources
4. Organisms with advantages survive to pass
those advantages to their children
5. Species alive today are descended with
modifications from common ancestors
Video: Natural Selection
 http://www.youtube.com/watch?v=AMtT
5_AQmLg