Download Natural Selection

11/23/2015
Biology 102
Lecture 14: Natural Selection
Early Biological and Geological Thought
•
Many attempted to classify or explain geological
and biological observations
•
Aristotle – 384 – 322 B.C.
•
“Ladder of Nature”
•
Organisms arranged in a linear hierarchy of
complexity
•
Do not change
Early Biological and Geological Thought
Early Biological and Geological Thought
•
The Earth and life on it are static
•
Earth has always existed in its present form
•
All species created simultaneously and do not
change over time
Early Biological and Geological Thought
•
1700s – Exploration of new lands revealed the
staggering diversity of life
•
People started asking questions…
Early Biological and Geological Thought
•
Georges Cuvier – “Catastrophism”
Catastrophism”
•
Charles Lyell – “Uniformitarianism”
Uniformitarianism”
•
Father of paleontology
•
Earth is much older
•
Earth is ~10,000 years old, shaped by
catastrophic events
•
Slow, gradual forces changed it
•
Same processes still at work today
•
Inorganic evolution
•
Causes mass extinction, species replaced by new
ones
1
11/23/2015
Early Biological and Geological Thought
•
Jean Baptiste Lamarack
•
Innate drive for perfection
•
Believed in spontaneous generation
•
Species change over time
•
Inheritance of acquired characteristics
Early Biological and Geological Thought
•
Thomas Malthus
•
Economist
•
People should outgrow
•
“Survival of the fittest”
food supply
Dude,
step off!!
Early Evolutionary Evidence
•
Evolution: Change over time in the
characteristics of a population
Modern Perspectives
•
Mid 1800s – Explanations for the concept of
evolution
•
Biological examples
•
Alfred Wallace
•
Geology
•
Charles Darwin
•
Fossils
2
11/23/2015
Voyage of the Beagle – 1831
1831-1836
Charles Darwin
•
1831 – Charles Darwin was recommended by his
former mentor to accompany Robert FitzRoy
aboard the HMS Beagle
12 shirts
1 carpet bag
1 pair slippers
1 pair of light walking shoes
1 microscope (a single lens model by Bancks & Son,
London)
1 geological compass
1 plain compass
2 pistols (with spare parts)
1 rifle (with spare parts)
1 telescope
1 pencil case
1 geological hammer
5 simisometers
3 mountain barometers
1 clinometer
1 camera obscura
1 hygrometer (belonged to FitzRoy)
FitzRoy)
1 taxidermy book
2-3 Spanish language books
14 other books, including Humboldt's "Personal
Narrative" and Lyell’s "Principles of Geology Vol. 1"
1 coin purse (Fanny Owen's gift)
1 pin with a lock of Sarah Owen's hair (Fanny's sister)
Charles Darwin
Charles Darwin
•
Returned a scientific celebrity
•
Returned a scientific celebrity
•
1836 – 1858: Combined his observations with the
work of Lyell and others to develop his theories
on evolution
•
1836 – 1858: Combined his observations with the
work of Lyell and others to develop his theories
on evolution
•
Elements of the theory:
•
Descent with modification
•
Adaptation by natural selection
Four Postulates of Darwin’s Theory
•
Postulate 1
•
There is individual
variation within a
Four Postulates of Darwin’s Theory
•
Postulate 2
•
At least some of these
variations are heritable
population
3
11/23/2015
Four Postulates of Darwin’s Theory
•
Postulate 3
•
Four Postulates of Darwin’s Theory
•
Not all individuals in a
•
Survival and reproduction are not random
population will survive
•
Those with favorable traits leave more offspring
and reproduce
•
Favorable traits accumulate in a population
•
Population is modified by natural selection
•
High reproductive effort
•
Limited resources
•
Unequal reproductive success
How Natural Selection Works
“Survival of the fittest”
How Natural Selection Does Not Work
•
Adaptation has nothing to do with effort
•
Natural selection does not give organisms what
they “need”
•
An advantage must be heritable in order for it
to be passed on to offspring
Question
•
Postulate
The skin color of frogs naturally varies from
green to brown to orange to red to blue. None
of the frogs pictured below is poisonous, but all
live in an area covered with green plants. Which
frog will be more likely to survive and
reproduce?
The Evidence for Natural Selection
•
Artificial selection
•
Select for desired traits
•
Large changes, short time
4
11/23/2015
The Evidence for Natural Selection
•
Artificial selection
The Evidence for Natural Selection
Artificial selection
•
•
Select for desired traits
•
Large changes, short time
Maize
•
Select for desired traits
•
Large changes, short time
Teosinte
The Evidence for Natural Selection
30MYA
45MYA
50MYA
55MYA
Orohippus
40MYA
Youngest
rocks
Epihippus
35MYA
Eocene
Equus
Dinohippus
Astrohippus
Onohippidion
Calippus
Pliohippus
Protohippus
Nannippus
Cormohipparion
Neohipparion
Hipparion
Merychippus
25MYA
Desmatippus
20MYA
Oligocene
Parahippus
15MYA
Archaeohippus
Miocene
Fossils in newer strata do
Kalobatippus
10MYA
Megahippus
browsers
grazers
mixed feeders
5MYA
Hypohippus
Pliocene
Pseudhipparion
Pleistocene
Miohippus
•
Fossils in older strata don’t look much like
species from today
Mesohippus
•
Example: evolution of the horse
•
Anchitherium
Fossil record
Hyracotherium
•
The Evidence for Natural Selection
60MYA
Oldest
rocks
Hyracotherium
(browsers)
55
The Evidence for Natural Selection
Mesohippus
(browsers)
40
Anchitherium
(browsers)
20
Merychippus
(mixed feeders)
17
Neohipparion
(grazers)
Nannippus
(grazers)
14
12
Equus
(grazers)
5
The Evidence for Natural Selection
•
Fossil record
•
Transitional fossils
Caudipteryx – 125 mya
Archaeopteryx – 145 mya
55 mya
browsers
40 mya
browsers
14 mya
grazers
20 mya
browsers
12 mya
grazers
17 mya
mixed feeder
5 mya
grazers
Reptiles
birds
5
11/23/2015
The Evidence for Natural Selection
•
Fossil record
•
The Evidence for Natural Selection
•
Transitional fossils
Fossil record
•
Tiktaalik – 375 mya
Modern toothed whales
Transitional fossils
LobedLobed-finned fish
Rodhocetus swam with
an up-and-down
motion. 47 mya
Land back to sea
Ambulocetus
probably walked on
land. 49 mya
Pakicetus attocki lived
on land. 55 mya
Water
salamander
land animals
The Evidence for Natural Selection
•
Comparative anatomy
The Evidence for Natural Selection
•
•
Homology: Similar ancestry, different function
•
Example: vertebrate forelimbs
Comparative anatomy
•
Vestigial structures – relics of the past
humerus
Pterodactyl
Dolphin
Dog
ulna
radius
carpals
metacarpals
phalanges
Human
Bird
Bat
FLYING
Seal
SWIMMING
Sheep
RUNNING
Shrew
GRASPING
The Evidence for Natural Selection
•
Comparative anatomy
•
The Evidence for Natural Selection
•
Observations in nature
Development
6
11/23/2015
The Evidence for Natural Selection
•
The Evidence for Natural Selection
DNA sequence comparison
•
Observations in humans
The Evidence for Natural Selection
How do these organisms relate to each other?
0
1
10
11
13
17
28
Evolutionary relationships based on DNA and protein sequence Cytochrome C amino acid differences
The Evidence for Natural Selection
•
Pseudogenes
The Evidence for Natural Selection
•
Pseudogenes
•
“Dead” genes
•
“Dead” genes
•
Example: Ascorbic acid (vitamin C) synthesis
•
Example: olfactory genes in mammals
Total # of olf. genes
% dead
Dog
1,100
18%
Mouse
1,500
20%
Rat
1,500
19.5%
Human
900
63%
7
11/23/2015
The Evidence for Natural Selection
•
Experimental evidence
•
The Anole
Natural Selection
•
Natural selection is not random
•
Traits are produced by chance
mutations
•
The traits that persist in a
population are those that
work best in the organism’s
environment
Convergent Evolution
•
Convergent Evolution
Similar traits evolve separately, but in similar
environments
•
Similar selection pressures
•
Example: Placental mammals vs marsupials
Niche
Placental
Mammals
Burrower
Anteater
Mole
Nocturnal
Insectivore
Glider
Stalking
Predator
Wolf
Ocelot
Ring-tailed lemur
Numbat
Marsupial
mouse
Cactus
Thylacine
Spotted cuscus
Marsupial mole
Chasing
Predator
Flying squirrel
Grasshopper
mouse
Lesser anteater
Australian
Marsupials
Climber
Asia & Australia
North America
Euphorbia
Flying phalanger
Tasmanian
quoll
Biogeography
•
Geographical distribution of species
• Species differ slightly when separated by
geographic barrier
• Examples
• Primates separated by water
Biogeography
•
Geographical distribution of species
• Species differ slightly when separated by
geographic barrier
• Examples
• Snapping shrimp separated by the
Isthmus of Panama
8