Transcript Mr. Martin`s Unit 5 PowerPoint #1

Evolution
• Definitions:
• “genetic change in a population”
• “change in gene frequencies within the
gene pool”
I. Historical Background
A. Georges Cuvier (1769-1832)--catastrophism
and paleontology
B. James Hutton (1795)--gradualism
C. Jean Baptiste Lamarck (1809)
1. Innate tendency toward perfection
2. Use and disuse = Use an organ and it
develops; do not use it and it deteriorates.
3. Inheritance of acquired characteristics
http://thinks.com/puzzles/hidden1.htm
D. Charles Darwin (1809-1882)
1. Major influences
a. Voyage of the HMS Beagle (1831-1836)
b. Charles Lyell , friend, wrote Principles of
Geology (1830) (uniformitarianism)
c. Thomas Malthus, “Essay on the Principles
of Population” (1797) --geometric
population increases are countered by
environment factors i.e. starvation, war,
disease
d. artificial selection--pigeons, dogs, roses
2. Mechanism of natural selection
a. Variation exists among all living things.
b. There is an overproduction of offspring.
(exponential growth)
c. This leads to competition for resources and
space.
d. Those best adapted to the environment due to
their genetic makeup survive and reproduce,
passing on their favorable adaptations.
II. The Evidence of Evolution
A. Paleontology--fossil studies
1. Types of fossils--petrified copies, carbon
copies, casts, footprints, amber
2. Fossil series – bones of ancestors are put in a
sequence – Example: horses
(danger of oversimplification here)
3. Index fossils
are used to
correlate rock
strata and organize
geological column
An Ammonite. By permission of
Emporia State University Geology
Museum, Emporia, KS.
B. Comparative anatomy
1. Homologous
structures, i.e. features
that are similar based
upon structure, these
similarities indicate
common ancestry.
2. Analogous structures,
i.e. features that similar
based upon function,
these similarities do not
indicate common
ancestry
C. Vestigial Structures – structures with no
current known functions
-human ear muscles, wisdom teeth, body
hair, limb bones in pythons and whales
D. Embryology - closely related organisms go
through similar development stages as embryos
E.
1.
2.
3.
Biogeography (geographical distribution)
Australia
Galapagos Islands
Hawaiian Islands
F. Biochemistry
1. Amino acid sequences - cytochrome c
2. Nucleotide sequences in DNA – cytochrome b
G. Microevolution – change within a species that has not
yet led to species formation
1. Insecticides and insects
2. Antibiotics and pathogenic bacteria
3. Finch’s beak
Play
Game
III. Speciation (Chapter 19)
A. Definition of species
1. Group of organisms with a common gene
pool
2. Group characterized by reproductive
isolation (gene pool is isolated)
3. Group sharing morphological similarities
B. Reproductive Barriers -- restrict gene flow,
but are not geographical
1. Prezygotic barriers
2.
Postzygotic barriers -- usually
chromosomal problems
C. Speciation -- when two populations of a species
become so different that there is no gene flow
between them when they are brought together,
i.e. they demonstrate reproductive isolation
1. Allopatric speciation -- caused by geographical separation
a. Galapagos Islands -- small isolated groups form, genetic
drift (founder effect) in action
b. Barrier formation -- rivers, mountains, glaciers, land
slides, etc., gene flow is interrupted, different habitats are
sometimes formed, usual result is extinction
From: http://tolweb.org/tree/learn/concepts/whatisphylogeny.html
What is Phylogeny?
Biologists estimate that there are about 5 to 100 million species of organisms living on Earth today.
Evidence from morphological, biochemical, and gene sequence data suggests that all organisms on
Earth are genetically related, and the genealogical relationships of living things can be represented by a
vast evolutionary tree, the Tree of Life. The Tree of Life then represents the phylogeny of organisms, i.
e., the history of organismal lineages as they change through time. It implies that different species arise
from previous forms via descent, and that all organisms, from the smallest microbe to the largest plants
and vertebrates, are connected by the passage of genes along the branches of the phylogenetic tree that
links all of Life (Figure 1).
Figure 1: All organisms are connected by the passage of genes along the branches of the phylogenetic Tree of Life.
The organisms that are alive today are but the leaves of this giant tree, and if we could trace their
history back down the branches of the Tree of Life, we would encounter their ancestors, which lived
thousands or millions or hundreds of millions of years ago (Figure 2).
Figure 2: Living organisms sit like leaves at the tips of the branches of the Tree of Life. Their evolutionary history is represented by a series of
ancestors which are shared hierarchically by different subsets of the organisms that are alive today.
The notion that all of life is genetically connected via a vast phylogenetic tree is one of the most romantic
notions to come out of science. How wonderful to think of the common ancestor of humans and beetles. This
organism most likely was some kind of a worm. At some point this ancestral worm species divided into two
separate worm species, which then divided again and again, each division (or speciation) resulting in new,
independently evolving lineages. Little did these worms know, those hundreds of million years ago, that
some of their number would end up evolving into beetles, while their brothers and sisters would end up as
humans or giraffes.
Organisms have evolved through the ages from ancestral forms into more derived forms. New lineages
generally retain many of their ancestral features, which are then gradually modified and supplemented with
novel traits that help them to better adjust to the environment they live in. Studying the phylogeny of
organisms can help us explain similarities and differences among plants, animals, and microorganisms. The
Tree of Life thus provides a rigorous framework to guide research in all biological subdisciplines, and it is
therefore an ideal model for the organization of biological knowledge.
2. Sympatric speciation -- new species within
same geographical area as parent species
(common in plants, rare in animals)
[polyploidy = 2n
4n]
a. Autopolyploidy -- self-fertilizing plant become
tetraploid, thus cannot interbreed with parents
b. Allopolyploidy -- a new species forms
from a normally sterile hybrid
V. Patterns of speciation
A. Anagenesis -- phyletic evolution
1. transformation of a single ancestral
species into a single descendant species
B. Cladogenesis -- branching evolution
1. transformation of one ancestral species
into more than one descendant species
2. a type of speciation
C. Adaptive radiation
D. Convergent Evolution
VI. Pace of Evolution
A. Gradualism (Darwin) -- change occurs
stepwise or gradually
-no stasis
-many intermediate forms
B. Punctuated equilibrium (Stanley, Gould)
-rapid change, then stasis
-few transitional forms
[Fossil record manifests repeated mass extinctions followed by mass
speciation. (26 million year cycle)]