Download Principles of Evolution

Principles of Evolution
5-23-16
Chapter 18 section 1
Announcements:
• Quiz 5 (last quiz!!!) is on Wednesday
– Topics: biotechnology (chapter 17.1) and
principles of evolution (chapter 18.1)
Learning Goals for Today:
• Discuss the theory of evolution
• List some of the evidence that Darwin used to
formulate the theory of evolution
• List some of the data used to support the
theory of evolution
• Predict how a population may change over
time
Evolution: what is it?
• Book definition of evolution:
– the change over time in the characteristics of a
population
• A population consists of all the individuals of one
species in one location
– Micro- : An increase in the frequency of the gene
for dark wings in beetles from one generation to
the next
– Macro- : The extinction of all dinosaurs
Pre-Darwin and Wallace:
• All organisms were created simultaneously
(by a creator)
• They did not change
Greek philosophers:
Humans
Mammals
• Plato (427–347 B.C.) each object
on Earth is just a temporary
reflection of its divinely inspired
“ideal form”
• Aristotle (384–322 B.C.) increasing
complexity of organisms indicates
their perfection in the “Ladder of
Nature”
Birds
Reptiles and amphibians
Whales and porpoises
Fish
Squids and octopuses
Lobsters, crabs, etc.
Snails, clams, etc.
Insects, spiders, etc.
Jellyfishes, sponges, etc.
Higher plants
Lower plants
Inanimate matter
What got people thinking that
organisms could change
• 18th century: world exploration revealed more
species than anticipated
• Naturalists including Georges-Louis Leclerc noticed
that each geographical location had its own group of
species, even when environments were similar
• Some species in the same location were similar but
different in some aspects
• Having different sets of species in the same location
was inconsistent with the idea of fixed and
unchanging forms
How could this change (evolution)
happen?
• Jean Baptiste Lamarck (1744–1829) proposed
inheritance of acquired characteristics
– Due to use or disuse of different parts
• “use it or lose it”
– These modifications are passed to offspring
Theory unsupported for genetic inheritance
Is supported for cultural/behavioral characteristics
Dude,
step off!!
According to Lamarck
Modern Perspectives
•
•
Mid 1800s – Explanations for the concept of evolution
Both did expeditions in the tropics
• Charles Darwin (1831 to 1836, S. America, Australia, and
Africa)
• Alfred Wallace (Brazil, 1848 to 1852; Malay Archipelago,
1854 to 1862)
Published 28 years
after the expedition
in The Beagle began
Voyage of the H.M.S. Beagle and Darwin
Voyages of Wallace and Darwin
Australia
America
Darwin (and
Wallace) noticed:
Similar organisms
on different
continents
Found in similar
environments
Appear to have
similar roles
Darwin’s Finches, Residents of the
Galápagos Islands
Beak size corresponds with
food preference
Idea: changes in food supply
leads to selection for or
against specific beak shapes
For example, seed-eating
finches had stronger, thicker
beaks for breaking seeds, and
insect-eating finches had
spear-like beaks for stabbing
their prey.
Darwin noticed that different,
yet related, animal species
often occupied different
habitats within a local area.
Darwin notices fossil organisms that
resembled modern organisms
Armadillo
Glyptodon
Darwin noticed that species were
changing
• Darwin wanted to explain the biological
diversity he observed in a scientific way
• As he traveled, Darwin noticed three
distinctive patterns of biological diversity: (1)
Species vary globally, (2) species vary locally,
and (3) species vary over time.
Idea of natural selection
• Exploration of new lands revealed a staggering
diversity of life
– Discovered vast numbers of new species
– Early explorers often took naturalists along to
catalogue the plant and animal life they found
• Darwin: naturalist on the Beagle
• Wallace was a naturalist too but he worked
independently
– Idea of “survival of the fittest” explains changes in
populations
Natural selection
• Successful reproduction of individuals with
favorable traits that survive environmental
change because of those traits
• Leads to evolutionary change
• Fit = has more babies that survive
How Does Natural Selection Work?
• Darwin (and Wallace) proposed that life’s
diverse forms arose through the process of
descent with modification (evolution)
– Individuals in each generation differ slightly from
the members of the preceding generation
– Over long time periods, small differences
accumulate to produce major transformations
LaMarckian and Darwinian views
Four postulates of evolution –
Variation in phenotype
• Postulate 1: Individual members of a
population differ from one another
Fig. 14-6
Phenotypes must be heritable
• Postulate 2: phenotypic
differences can be passed
on from parents to
offspring – must be
heritable
More offspring are produced than are
able to survive
• Postulate 3: In each
generation, some
individuals in a
population survive
and reproduce
successfully but
others do not
Survival of the fittest because of
natural selection
• Postulate 4: Individuals
with advantageous traits
(phenotypes) survive and
leave the most offspring,
process known as natural
selection
What is natural selection?
• Unequal survival and reproduction of
organisms with different phenotypes, caused
by environmental forces
Natural selection modifies populations
over time
• Natural selection acts on individuals within a
population; however, it is the population that
changes over time
– Over generations, the population changes, as the
percentage of individuals inheriting favorable
traits increases
Adaptation
• A heritable trait that helps the survival and
reproduction of an organism in its present
environment
– The webbed feet of platypuses are an adaptation
for swimming
– The snow leopards’ thick fur is an adaptation for
living in the cold
– The cheetahs’ fast speed is an adaptation for
catching prey
How does natural selection happen:
step by step?
• A population with genetic/phenotypic
variation
1. A change occurs in the environment
2. Well-adapted individuals leave more
offspring than do poorly-adapted individuals
3. Genetic frequencies within the population
change
How Natural Selection Works
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
Worksheet on natural selection
Support for the Process of Evolution
• Fossils provide evidence of evolutionary
change over time
• Comparative anatomy gives evidence of
descent with modification
• Embryological similarity suggests common
ancestry
• Modern biochemical and genetic analyses
reveal relatedness among diverse organisms
Fossils Provide Evidence for Whale
Evolution from Land Mammals
Millions of years ago
0
Modern whales
40
Basilosaurus
45
Dorudon
Rhodocetus
Ambulocetus
50
Pakicetus
Fig. 14-7
The Evidence for Natural Selection
•
Fossil record
•
Transitional fossils
Caudipteryx – 125 mya
Archaeopteryx – 145 mya
Reptiles

birds
The Evidence for Natural Selection
•
Fossil record
•
Transitional fossils
Tiktaalik – 375 mya
Water  land animals
Lobed-finned fish
salamander
The Evidence for Natural Selection
•
Fossil record
•
Modern toothed whales
Transitional fossils
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
Divergent evolution
• Sometimes, evolution gives rise to groups of
organisms that become tremendously
different from each other
• When two species evolve in diverse directions
from a common point, it is called divergent
evolution
Comparative anatomy (homologous structures)
is a result of divergent evolution and provides
support for common ancestry
humerus
ulna
Pterodactyl
Dolphin
Dog
radius
carpals
metacarpals
phalanges
Human
Bird
Bat
FLYING
Seal
Sheep
Shrew
SWIMMING
RUNNING
GRASPING
Bones in the appendages share the same overall construction
Vestigial Structures: evidence of loss of once
important structures (divergent evolution),
“evolutionary baggage”
The bones of a salamander’s hindlimb
function in support and locomotion
(a) Salamander
(b) Baleen whale
(c) Boa constrictor
These vestigial bones are similar in
structure to those of the salamander
but serve no function; all three animals
inherited the bones from a common
ancestor
Shrunken to the point that
they no longer constitute a
survival-reducing burden.
The Evidence for Natural Selection
•
Comparative anatomy
•
Vestigial structures – relics of the past
The Evidence for Natural Selection
•
Pseudogenes
•
“Dead” genes
• Products of divergent evolution
• Example: Ascorbic acid (vitamin C) synthesis
Convergent Evolution gives rise to
analogous structures
•
•
•
Similar traits (“analogous structures”) 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
Thylacine
Spotted cuscus
Marsupial mole
Marsupial
mouse
Chasing
Predator
Flying squirrel
Grasshopper
mouse
Lesser anteater
Australian
Marsupials
Climber
Flying phalanger
Tasmanian
quoll
Convergent Evolution
Asia & Australia
North America
Cactus
Euphorbia
Analogous Structures: similar function but
unrelated, product of convergent evolution
Fig. 14-10
All vertebrate embryos look similar –
homologous traits in embryos provide
evidence of a common ancestor
Lemur
pig
At one point all possess gill slits and a tail
Which is the lemur, pig, human?
human
Homologous biochemical and cellular
features - Evidence for common ancestry
• Shared features of all cells
– DNA as a genetic blueprint
– RNA, ribosomes, and approximately the same
genetic code for translation
– same set of 20 amino acids to build proteins
– ATP to transfer energy
Cytochrome c gene is highly conserved
between species
human
mouse
human
mouse
human
mouse
human
mouse
human
mouse
human
mouse
human
mouse
human
mouse
Natural Selection - conclusions
•
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