REVIEW AND WRAP
UP OF CHAPTER 11
Clarification of some confusion
Development: Proximal or Ultimate?
• Clarification: Evolutionary Development is a PROXIMATE
mechanism that leads to an ultimate cause, tying the different
levels of analysis together.
• These developmental mechanisms have an evolutionary history that is sometimes
described as a series of modifications of an ancestral pattern into a modern
attribute.
• Major conclusions of evo-development is that although changes in the
base sequences of enzyme coding genes are important in evolution,
changes in mechanisms regulating gene expression may be even more
important.
• Transcriptional products that influence the activity of other genes and thus alter the
regulatory functions of the genome.
Adaptive Developmental Homeostasis:
• Question remains: How can organisms develop normally, more or
less, even with genetic mutations?
• Part of the reason is we have a fair amount of genetic redundancy as well
as built in compensatory mechanisms
• Examine all traits based on their possible adaptive value
Adaptive Developmental Switch
• Selectionist approach
• This approach acknowledges that there are sometimes two or more quite
distinct alternate phenotypes that can comfortably co-exist, and the
differences arise proximally as a result of environmental differences.
• Polyphenisms: several discrete phenotypes that can arise from a single
geneotype.
• Eg. Migratory Locusts
Adaptive Value of Learning
• Neural mechanisms allow for learning
• We can modify our behavior depending on our experiences
• Types of learning:
• Spatial learning: evolves in response to a particular ecological pressure
• Operant Conditioning: Trial-Error Learning
• An animal learns to associate a voluntary action with consequences that follow from the
action
• The ease of conditioning differs depending on factors such as novelty, intensity of
consequence, an time interval between the stimulus and the response.
• E.g. conditioned taste aversion
SPECIATION AND
PHYLOGENETICS
Speciation:
• What is it?
• How does it occur?
• Where does it occur?
• How long does it take to make a new species?
• Can we observe speciation in real time and/or in the fossil record?
What is a species?
• The Biological Species Concept
• Reproductive isolation is the centerpiece of the BSC. Reproductive
isolation is the failure of populations to interbreed or to form viable
or fertile hybrids
• "a species is an array of populations which are actually or
potentially interbreeding, and which are reproductively isolated
from other such arays under natural conditions." (Ernst Mayr)
The Phylogenetic Species Concept
• Studies the history of the evolution of a species or group, especially
in reference to lines of descent and relationships among broad
groups of organisms.
• Fundamental to phylogeny is the proposition, universally accepted
in the scientific community, that plants or animals of different
species descended from common ancestors..
• The evidence for such relationships, however, is nearly always
incomplete, for the vast majority of species that have ever lived are
extinct, and relatively few of their remains have been preserved in
the fossil record.
• Most phylogenies are hypotheses and are based on indirect
evidence.
• Different phylogenies often emerge using the same evidence.
• Nevertheless, there is universal agreement that the tree of life
is the result of organic descent from earlier ancestors and that
true phylogenies are discoverable, at least in principle.
Pylogenetic trees
• Most of the data used in making phylogenetic judgments have
come from comparative anatomy and from embryology
• In comparing features common to different species, anatomists try
to distinguish between homologies, or similarities inherited from a
common ancestor, and analogies, or similarities that arise in
response to similar habits and living conditions
Figure 2.10
Monogamy and the
origin of eusociality by
kin selection in the
Hymenoptera
Figure 2.9
Haplodiploidy and the
evolution of
eusociality in the
Hymenoptera
Figure 2.9 Haplodiploidy and the evolution
of eusociality in the Hymenoptera
Figure 2.9
Haplodiploidy and the
evolution of
eusociality in the
Hymenoptera (Part 4)
Figure 2.16
Evolutionary history of
the honey bee dance
communication system
Box 2.3 How are phylogenetic trees constructed
and what do they mean?
Which taxon on the tree below is most
advanced/specialized?
a. A
b. B
c. C
d. D
e. None of the above
Which taxon on the tree below is most closely related to taxon A?
a. B
b. C
c. D
d. All of the above are
equally closely
related to A
Which taxon on the tree below is most closely related to taxon C?
a. A
b. B
c. D
d. B and D are
equally closely
related to C
e. All of the above are
equally closely
related to C
Which taxon on the tree below is most closely related to taxon D?
a. A
b. B
c. C
d. All of the above are
equally closely
related to D
Example test question:
Write a short response to the following question:
• If a species has a vestigial anatomical structure that it no longer
uses, would you expect this structure to disappear over many
generations through the action of natural selection? Always,
sometimes, or never? Explain your answer.
Example Test Question:
Write a short response to the following question:
• What does it mean to be fit in
an evolutionary sense?
Homology in the Brain
Plainfin Midshipman Fish
Human
Feeding Behavior
Fear and Reward Circuitry
Emotion