Download Natural Selection

EVOLUTION
http://www.snotr.com/video/128
I. Introduction & Famous Theorists
A. Evolution is a STRONGLY supported theory…. lots of evidence!
B. Evolution is the genetic change in a species over time.
*** occurs in a population NOT IN INDIVIDUALS!
C. Famous Theorists:
1. Jean-Baptiste Lamark (1809)
a) Use and Disuse: organisms evolve because they
needed to adapt to changes in environment
b) Inheritance of Acquired Traits: useful traits developed during an
individual’s lifetime are passed on to its offspring
Ex. If you cut off your left hand… your kids won’t have one either
2. August Weismann (early 1900s)
Well that’s just
not cool!
You could say I am a …..wise…..man……
a) Disproved Lamark’s theory by cutting off the tails of mice for 50
generations.
*surprisingly… every generation grew tails.
I’m the man.
3. Charles Darwin (mid-1800s)
a) English naturalist.
b) Travelled around the world on the HMS Beagle
c) He studied and collected many organisms
d) On The Origin of Species (1859)
* Darwin’s book
e) Natural Selection:
• Overpopulation - More offspring are born than can
possibly survive
• Competition - These offspring must compete for limited
resources
• Variation - Slight differences occur among members of the population
(Caused by mutations and genetic recombination/crossing-over during meiosis)
• Adaptation - Variation that causes some individuals to have a greater
Fitness (ability to survive and reproduce) than others.
•Survival of the Fittest -
So…
close…
Curse
this
short neck!
I’m better than you.
Mmm…
This tree is delicious…
•Survival of the Fittest Individuals who are more fit for their environment are more likely to
survive and reproduce to pass on their favorable traits.
Less fit individuals die and their unfavorable traits are eliminated
from the gene pool
• Speciation - Many changes ultimately produce new species better
adapted to an environment
Adapted to cold
through heavier
fur, short ears,
short legs, short
nose. White fur
matches snow
for camouflage.
Northern
population
Early fox
population
Spreads
northward
and
southward
and
separates
Arctic Fox
Different environmental
conditions lead to different
selective pressures and evolution
into two different species.
Adapted to heat
through lightweight
fur and long ears,
legs, and nose, which
give off more heat.
Southern
population
Gray Fox
Fig. 5.8, p. 113
*Examples of Natural Selection
1) Galapagos Island Finches
• Distinct differences (beak sizes and shapes) among birds
on different islands
• Selecting agents = varying foods the finches ate.
2) Peppered Moth (in England)
• Two varieties: light-colored and dark-colored
• Pre-industrialization:
light-colored moths blended in with light tree bark
 more light moths than dark moths
• Post-Industrialization:
 soot covered trees
 Dark moths have
advantage
3) Insecticide-resistant Insects & Antibiotic-resistant Bacteria
• Insecticides kill most insects, while some insects are
resistant to the insecticide & live to reproduce
(Insecticide acts as a selecting agent)
• Antibiotic kills most bacteria, while resistant bacteria
live to reproduce. (Antibiotic is selecting agent)
• A natural variation
existed which allowed
some insects/bacteria
to survive exposure
to
insecticide/antibiotic
(selecting agent) and
reproduce
II. Evidence of Evolution
A. Fossils: preserved remains or evidence of an ancient organism
* Whole organism, bones, teeth, footprint, leaves, etc.
* Fossils form by layering of sedimentary rock
Recent
Oldest
B. Evidence in Living Organisms
1) Comparative Anatomy: structural similarities
• Homologous structures: similar form but different function
• Vestigial structures: remnants of structures that used to be useful
Ex. Appendix
2) Comparative Embryology: closely related species have similar
patterns of development
*Common ancestor
3) Comparative Cytology: similarities in cell structures
4) Comparative Biochemistry: closely related organisms have similar
DNA and proteins
Ex. human vs. ape hemoglobin
III. Causes of Evolution:
A. Sources of Genetic Variations
1. Mutations
2. Sexual Reproduction:
•Crossing over
B. When two populations are isolated from one another…
Natural selection might affect them differently, leading
to new species.
Geographic Isolation…
Behavioral Isolation
*Adaptive radiation*
Period of evolutionary change in which groups of organisms
form several new species with adaptations to fill different
niches in the community.
Galapagos Island Finches
• Similarities among all of the species, both on the
mainland and the islands
• Distinct differences (i.e. beak sizes and shapes) among
those on different islands, which Darwin attributed to
the selecting agents of the varying foods the finches ate.
C. Things to remember:
• Evolution is a change in a population over many generations
• Natural selection doesn’t
act directly on genes- it
acts on phenotypes by
determining which traits
(alleles) are passed on.
D. Theories of Evolution Patterns:
Gradualism
Vs.
Punctuated Equilibrium
*evolution is slow,
gradual, and
continuous.
Present
Past
*long periods of little
or no change are
interrupted by short
periods of rapid change.
Present
Common
Ancestor
Past
Common
Ancestor
E. The First Cell(s):
1. Early Hypotheses
a. Creationism
b. Spontaneous Generation: life arises from nonliving matter
• Aristotle, Virgil
Redi’s Experiment
Pasteur’s Experiment
2. Heterotroph Hypothesis (Modern Hypothesis)
a. Primordial Soup: Early Earth was covered in hot water with
various chemicals dissolved in it
• organic compounds formed through random bonding
• the first “cell” consumed other materials and divided
…a heterotroph!
Miller-Urey
Experiment
b. The first life forms were anaerobic.
• Autotrophs evolved, releasing oxygen into the atmosphere,
allowing some life forms to evolve and become aerobic