Transcript Nerve activates contraction

CHAPTER 22
DESCENT WITH MODIFICATION:
A DARWINIAN VIEW OF LIFE
Evolution :
processes that have transformed life on
Earth from its earliest forms to the
vast diversity that characterizes it
today.
*diversity of organisms
*origins and relationships
*similarities and differences
*geographical distribution
*adaptations to surrounding environment
HMS Beagle
Who was Charles Darwin?
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1809 - 1882
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Captain Fitzroy’s traveling
companion on the Beagle
Hated
Was a Medicine
‘substitute’ and
Hated
almostConfrontations
did not get on the
HMS
Spent Beagle
time collecting
beetles, catching
rats, …..
Geologist,
zoologist,
paleontologist,
naturalist
Hated being in the
ministry
Author
of the
book “Origin
Was called
a “disgrace
to
of
Species”
thethe
family”
by his father
Robert
Darwin!
Said
- writing
it was “Like
Confessing a Murder”!
VOYAGE OF THE HMS BEAGLE : 1831 - 1836
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Fossil record
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Created by impressions of
organisms that existed in
the past
Fossils in sedimentary
rock – show succession of
organisms through time
(includes transitional
forms and extinctions)
Slow and subtle processes persisting for long
periods of time can add up to substantial
change - Geology records this before
‘evolutionary’ theories (plate tectonics,
mountain building/erosion……)
Jean Baptiste Lamarck: the outcaste!
 used the fossil record as evidence
 proposed a theory of evolution
where organisms became better
and better
 Mechanism - ”use” and “disuse”
leads to:
 inheritance of acquired
characteristics (you ‘acquire’ a
phenotype in your lifetime and
pass it on to your kids)
 also means environmental
influences can be inherited
 DON’T BE LAMARCKIAN!
FOR YOU WILL BE
DISSSSED……. BUT WAIT,
NOW, Epigenetics makes Lamarck a new Hero!!!! (oh
you did not hear that as far as your not-so -current AP
exam goes - stomp with glee on Lamarck all you want!)
Carolus Linnaeus:
--founded
taxonomy and the
genus/species
system of naming
organisms
Homo - genus
sapien - species
AHEM! NOTICE THEY ARE BOTH MALE!
DOMAIN
Kingdom
Country
Phylum
State
Class
County
Order
Town
Family
Neighborhood
Genus
Street
Species
House Number
King Philip Came Over For
Getting Stoned (yikes!)
Observation: 13 or so species of finches on different Galapagos
islands; these finches resembled the South American (mainland)
finches more than say finches in Asia….
Can you summarize how
EVOLUTION occurred to
produce separate populations of
large and medium beaked
Ground Finches in Galapagos
Islands?
Medium Ground Finch
(smaller beak)
Large Ground Finch (Larger
Beak)
Microevolution: changes in allele frequencies (=how often you see a
particular phenotype) from generation to generation
Speciation/Macroevolution: Evolution of
distinct species (that cannot mate)
One population of birds on one island
After a long time, there are now 2
islands and 2 populations with a
reproductive barrier (geographic).
many insects in tree
holes
lots of plants (with
hard to crack seeds)
The birds adapt to their niche and cannot mate
anymore = 2 different species!
many insects=long
beak
lots of plants with
seeds=large beak
What did Darwin Say?
 Descent
with modification (diverse life
forms have risen from a common ancestor)
(the CONCLUSION)
 Descent occurs through the process of
Natural selection (the HOW?)
Observations:
 All populations would increase exponentially if
all individuals reproduce successfully.
Populations tend to remain stable in size.
Environmental resources are limited.
Inferences:
There is competition for resources – the
“struggle for existence”
Only a small fraction of the population survives
Observations:
 Individuals in a population have varying
characteristics.
 Much of this variation is heritable.
Inferences:
Survival
depends on inheriting the “best fit”
physical traits (“reproductive fitness”)
This unequal ability of individuals to survive
and reproduce will lead to a gradual change in a
population, with favorable characteristics
Island with many many insects
accumulating over the generations.
Darwin’s main ideas : 6 steps KNOW THIS INSIDE OUT!
1) All populations will try to increase in time; Resources are limited (intraspecific
competition results). Struggle for existence follows.
2) There is an unequal ability of individuals to survive and reproduce - this is
‘variation’ based on genes/epigenome.
3) Natural Selection acts on this inherent VARIATION allowing the “best fit” to
survive and pass on their genes.
4) The product of natural selection is the adaptation of populations of organisms
to their environment. (= edits the variation to exclude ‘unfit’ individuals)
5) This adaptation is inheritable - so the next generation continues to express
that ‘best fit’ trait and then in time…..
6) New species formed as sufficient adaptations accumulated in time such that
they could no longer mate with the ancestral species
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Descent with modification - all present day organisms have descended from
ancestors by the accumulation of adaptations through natural selection
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Descent with modification - the conclusion.
Descendents accumulated diverse modifications or
adaptations that fit them to specific ways of life and
habitats - resulting in formation of new species.
All present day organisms are related through descent
from unknown ancestors in the past.
DESCENT WITH MODIFICATION – CORE
OF DARWINIAN THEORY
-More descent:
Organisms are
related through
descent from
common ancestors
So….. All organisms
in a CLASS have a
common ancestor at
the level of the
PHYLUM and so
on…
• This evolutionary tree of the elephant family is
based on evidence from fossils.
Fig. 22.7
Fig. 22.9
Apply the concept of Natural
Selection and predict what will
happen to these beetle species in
this new environment
Fig. 22.9
Apply the concept of Natural
Selection and predict what will
happen to these beetle species in
this new environment
• For example, these related species of insects called
mantids have diverse shapes and colors that evolved
in different environments.
Fig. 22.10
Artificial Selection: The selective breeding of
domesticated plants and animals to
encourage the occurrence of desirable traits.
 Short period of time needed for Artificial
Selection
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What common EVOLUTION
misconceptions do students have?
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Organisms “choose” to
evolve better traits
(Lamarckian)
Natural Selection causes
variation
Natural selection acts on
ALL variation
Natural Selection acts on
individuals and
therefore individuals
evolve
What is EVOLUTION?
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Evolution is measured as the change in relative
proportions of heritable variation in a population
over a succession of generations.
Is there evidence for evolution?
Insecticide resistance
AIDS
Pepperred moth
Homologies
(Anatomical
Embryological
Molecular)
Biogeography
Fossil Record
2a) Natural selection in action: the evolution of insecticideresistance occurs in nature - individuals with the best fit genes
that can resist the insecticide will survive….
Fig. 22.12
2b) Natural selection in action: the evolution of drugresistant HIV - 3TC drug resistance developed - 100%
HIV become resistant in 3-4 weeks!
2c) Natural selection in action: the peppered moth - originally light
colored on light bark; Industrialized England - bark became covered
in soot; so bark became dark; moth evolved to become dark
3a) Anatomical -human hand, cat limb, whale flipper, bat
wing - they all have the same basic bone structure and
design;
they have ALL evolved from
B)SoHOMOLOGIES
– a common
ancestor
with a similar
‘limb design’. Related
to this:
 Similarities
in characteristics
resulting
from
common
ancestry is
known as are
homology.
3b) Genetic
Homologies:
Homeoboxes
a common set of
developmental
genes seen
in species
as diverse
as the fly to
 1) Homologous
Structures:
Same
skeletal
mammals!
elements, but different functions
 Same ancestor- tetrapod forelimb.
HOMOLOGOUS STRUCTURES
3b) Molecular Homologies
 Basic genetic Code (all organisms) and….
Ontogeny recapitulates phylogeny what ever does this mean?
Ontogeny recapitulates phylogeny what ever does this mean?
Ontogeny recapitulates phylogeny - the
phylum origin is ‘recapped’ in the embryo
3c) Embryological Homologies - embryos look alike
in related species!
 All vertebrate embryos have ‘pharyngeal pouches’
in their throat. These in the Adult become gills of
fish or the Eustacean tubes in other vertebrates!
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Homologies mirror the tree of life.
3d) Vestigial organs, structures that are not used, but
which had important functions in ancestors - still
retained in descendents, so evolution ‘happened’.
Some Alleged Vestigial Organs in Man
Tonsils
Coccyx (tail bone)
Thymus
Little toe
Nipples on males
Nodes on ears "Darwin's
points"
Pineal gland
Adenoids
Nictitating membrane of
eye
Appendix
Wisdom teeth
Parathyroid
Ear muscles for wiggling
Body hair
3d) Vestigial organs – spurs in snakes, hind leg
bones in whales.
4) Fossil Evidence- Capture evolutionary
transitions - all species not present at the
same time
5) Biogeography- The geographical distribution of
species .
Species tend to be
more closely
related to other
species from the
same area than to
other species with
the same way of
life, but living in
different areas
CONVERGENT EVOLUTION
5) Biogeography- extension- Island species
related to mainland species
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As Darwin said,
“There is grandeur
in this view of life.”
Fig. 22.18