Species

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Welcome back to IB 150...
Nautilus eye A pinhole camera - no lens
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Reproductive Altruism

• Why do some individuals forgo reproduction to
  help others reproduce?

Dwarf mongoose on guard
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A Problem For Darwin
Social insects - Live in colonies with only one
or a few reproductive females (queens)
In ants - caste is fixed at birth
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Coefficient of Relatedness
parents
p 0.5
offspring
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Cooperation in Ground Squirrels
Which sex gives alarm calls?
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Evolution of Human Behavior

• Human Sociobiology or Evolutionary Psychology
• Has the same problems as studying human genetics
  of complex traits
• Also human cultural evolution is proceeding very
  rapidly - very controversial area of study

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Lecture 16 Animal Behavior
Readings Ch. 51
Behavior as Phenotype
ethology, von Frisch, Lorenz, Tinbergen, fixed
action pattern, imprinting, proximate vs.
ultimate Proximate Studies of Behavior neuroethol
ogy, behavior genetics, comparative psychology
Simple Behavioral Categories kinesis, taxis,
migration, communication, foraging, aggression,
courtship, cooperation Effects of the Environment
nutrition, learning
Evolution of Behavior
group and individual selection Sexual Selection
and Mating Systems polyandry, polygyny, monogamy
Parental Care male, female, biparental Behavior
al Polymorphisms alternative mating strategies,
cooperative breeding and eusociality Evolution
and Human Behavior
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Lecture 17 Speciation and Systematics
Readings Chapters 24 and 25
Speciation micro vs. macroevolution,
reproductive isolation, prezygotic vs.
postzygotic isolation, biological species
concept, allopatric vs. sympatric speciation,
adaptive radiation Investigating the tree of
life phylogeny,
systematics, molecular phylogeny The evidence
used in phylogenies the fossil record,
morphological and molecular data
Phylogeny construction
cladistics, clade, cladogram, monophyletic,
paraphyletic, polyphyletic, outgroup, ingroup,
Phylogeny and the genome
molecular clocks, neutral theory, the
universal tree of life Phylogenetic systematics
and taxonomy taxonomy
(classification), binomial nomenclature,
hierarchical classification, Linnaeus, Linnaean
groups
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It is useful to divide evolution into two
parts Microevolution - population genetics,
natural selection, drift, mutation, studies of
ongoing adaptation and evolution of
diversity Macroevolution - large scale changes in
organisms over time The transition between these
is the study of speciation - the formation of new
species.
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What are species?
Fig. 24. 3 Well, we cant define them on the
basis of morphology (body form anatomy) because
one can find pairs of species that are very
similar, while in other cases there is a lot of
variation within a single species.
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So what are species, really?

• Many biologists use the biological species
  concept, which is based on the idea that members
  of species can reproduce successfully with each
  other.
• Thus it is based on reproductive isolation
  (barriers) between species, and gene flow within
  species.

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Biological species are organisms that interbreed
under natural conditions
Hobbs at the Sierra Safari Zoo in Nevada (tiger
mother, lion father)
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Fig. 24.4 - read in detail!
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Types (or modes) of speciation

• Speciation requires interruption in gene flow
  (movement of genes from one population to the
  next)
• allopatric speciation geographic barrier
  physically isolates populations at first so they
  can evolve reproductive isolation which will keep
  them apart when they later come together.
• sympatric speciation populations of organisms
  with overlapping ranges speciate without
  geographic isolation.

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Fig. 24.5
16
Fig. 24.6
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Sympatric speciation - speciation in the same
geographic area, is a hot area of research right
now. Two mechanisms are 1. Polyploidy -
speciation due to changes in chromosome
number. 2. Habitat selection - mating in
different habitats - I will talk about my
research in this area at the end of the semester,
so I will not go into it today.
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Adaptive radiation - bursts of speciation in new
geographic areas (good examples involve
archipelagoes like the Galapagos and Hawaiian
islands), in which the new species have adapted
to different ecological niches / habitats.
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Three Hawaiian Drosophila species
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Fig. 24.20 Evolution is not a linear trend, but a
bush
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Mutations contain a history of their past!
3 evolutionary steps
original
ATTAGATTAGCGATCGCTTTAATGGGGTAG
mutant 1
ATTAGATTAGCGATCGCATTAATGGGGTAG
mutant 2
T to A
ATTAGATTAGCGATCGCATTAATCGGGTAG
G to C
mutant 3
ATTAGATAAGCGATCGCATTAATCGGGTAG
T to A
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Some more terminology
original
ATTAGATTAGCGATCGCTTTAATGGGGTAG
branch
mutant 1
root
ATTAGATTAGCGATCGCATTAATGGGGTAG
mutant 2
T to A
ATTAGATTAGCGATCGCATTAATCGGGTAG
G to C
mutant 3
ATTAGATAAGCGATCGCATTAATCGGGTAG
T to A
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Note that we can infer the direction of
evolutionary change - for the first change, T is
the ancestral or primitive state, and A is the
derived trait.
original
ATTAGATTAGCGATCGCTTTAATGGGGTAG
mutant 1
ATTAGATTAGCGATCGCATTAATGGGGTAG
mutant 2
T to A
ATTAGATTAGCGATCGCATTAATCGGGTAG
G to C
mutant 3
ATTAGATAAGCGATCGCATTAATCGGGTAG
T to A
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Most times, we do not observe every step of
mutational change, but we can often infer the
most distantly related sequence to the rest. We
can call this sequence the outgroup (could be
more than one sequence).
ATTAGATTAGCGATCGCTTTAATGGGGTAG
outgroup
ATTAGATTAGCGATCGCATTAATGGGGTAG
T to A
ATTAGATTAGCGATCGCATTAATCGGGTAG
G to C
ATTAGATAAGCGATCGCATTAATCGGGTAG
T to A
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When you have identified the outgroup, you put
the root between the outgroup and the rest, which
becomes the ingroup.
ATTAGATTAGCGATCGCTTTAATGGGGTAG
outgroup
ATTAGATTAGCGATCGCATTAATGGGGTAG
T to A
ATTAGATTAGCGATCGCATTAATCGGGTAG
G to C
ATTAGATAAGCGATCGCATTAATCGGGTAG
T to A
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Now lets start moving toward making trees for
species (and other taxonomic groups)
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Present
19
9
16
11
24
8
3
15
20
1
17
12
2
7
14
10
21
4
18
13
6
22
11
23
TIME
The grand view of the combined effects of drift
and mutation - new alleles arise by mutation, may
go extinct immediately or increase. But all
alleles go extinct eventually.
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Present
TIME
At this point, since we are leaving population
genetics behind, we will only need to know about
the allele tree - not the frequencies. (Note
this is not the same exact pattern as in the
previous slide).
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Present
reproductive isolation
Species A
Species B
Species C
TIME
Now, what do you think would happen during a
speciation? The above is what is happening.
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Present
Species A
Species B
Species C
TIME
In reality, we dont often have fossil DNA from
the past, so all we can do is sample DNA from
living species and infer trees for those.
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Terms again
Node (speciation event)
Species A
Species B
Species C
root
branch
TIME
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A particular school of thought on inferring the
past that Campbell likes is called cladistics.
Cladistics espouses making cladograms by placing
species together that share derived characters or
features. How do we know what is derived? We
either observe the direction of change for the
particular character in the fossil record, or we
make a assumption about what is the outgroup, and
use that to infer direction. Primitive
original, derived later.
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Fig. 25.10. How should we establish a set of
names (bird, orchid, snail) based on a
phylogenetic tree? Most modern systematists
want their groups to be monophyletic - single
origin.
Unfortunately, groups like reptiles are
paraphyletic.
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Fig. 25.8. Modern systematists want their trees
and their Linnaean classification to agree. Carl
Linne was the inventor of the system of taxonomy
(classification) we still use. It is based on
nested hierarchies. Note that at the lowest
level we use italics, and that the genus name is
capitalized and the species name is not. This is
binomial nomenclature.
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Fig. 25.9. An example of a tree and a taxonomy
that agree.
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Lecture 17 Speciation and Systematics
Readings Chapters 24 and 25
Speciation micro vs. macroevolution,
reproductive isolation, prezygotic vs.
postzygotic isolation, biological species
concept, allopatric vs. sympatric speciation,
adaptive radiation Investigating the tree of
life phylogeny,
systematics, molecular phylogeny The evidence
used in phylogenies the fossil record,
morphological and molecular data
Phylogeny construction
cladistics, clade, cladogram, monophyletic,
paraphyletic, polyphyletic, outgroup, ingroup,
Phylogeny and the genome
molecular clocks, neutral theory, the
universal tree of life Phylogenetic systematics
and taxonomy taxonomy
(classification), binomial nomenclature,
hierarchical classification, Linnaeus, Linnaean
groups