Darwin’s Tea Party
Biological Adaptation & Evolution
Fall 2014
Two Definitions of Adaptation
• “Adaptation [verb] is the evolutionary process
whereby an organism becomes better able to
live in its … habitat” (T. Dobzhansky).
• “An adaptation” (noun) refers to a particular
body part, behaviour or other feature which
enables an animal to be better able to live (be
more fit) in its environment.
– e.g., the giraffe’s neck is an adaptation.
– The process by which it developed this neck is also
called adaptation.
• Adaptation can
refer to the
process by which
a creature gets its
useful parts
• Or it can mean
those useful parts
themselves
Biomimickry
A and B show real wasps; the rest are
mimics: three hoverflies and one beetle.
Two wasp species and four imperfect and
palatable mimics. (A) Dolichovespula
media; (B) Polistes spec.; (C) Eupeodes
spec.; (D) Syrphus spec; (E) Helophilus
pendulus; (F) Clytus arietes (all species
European). Of note, species C–F have no
clear resemblance to any wasp species.
The three hoverfly species differ in the
shape of their wings and body, length of
antennae, flight behaviour, and striping
pattern from European wasps. One fly
species (E) even has longitudinal stripes,
which wasps typically don't. The harmless
wasp beetle does not normally display
wings, and its legs do not resemble those
of any wasps.
Natural History Museum (UK), “I’m stuck
on you…who’s the pest? Episode Three”
http://www.nhm.ac.uk/natureplus/blogs/di
ptera-blog/tags/biomimicry
Camouflage as a form of adaptation
Camouflage is an amazing kind of adaptation
Spot the crab here?
Spot the stick insect?
The wonderful ichneumonidae (type of wasp) that eats
caterpillars from the inside out (just like the Alien monster)
before emerging out of it as afull grown wasp. A
wonderfully horrific adaptation!?
Echolocation:
another adaptation
allowing bats to
“see” by sonar or
sound waves.
Adaptations can be about behaviour, like the
web-making behaviour of the spider.
Woodpecker’s adaptations
•
Woodpeckers are most noted for their stout, chisel-like beaks
which they use to drill holes in trees to obtain food or make a
home. The beak is also used for drumming, which is the male's
way of signaling to his mate or declaring his territory to other
woodpeckers.
•
When searching for food, the woodpecker drills a small hole,
then uses its narrow, probing tongue to dislodge and extract
insects from their burrows in the wood or bark. For choice
morsels in those hard-to-reach places, the woodpecker may
extend its tongue four to five inches beyond the tip of its beak.
•
Watching the force with which the woodpecker strikes the tree,
it's amazing that the bird can hold on. Its toe arrangement, two
toes facing forward and two backward, gives the woodpecker a
solid base on which to cling to the tree. Its sharp claws dig into
the wood, and its stiff, square tail feathers braced against the
tree act as a support prop.
•
Even the woodpecker's skull is specially designed to withstand
repeated blows and to protect the bird's brain from concussion.
Unlike other birds, the bones between the beak and the skull are
joined by a flexible cartilage, which cushions the shock of each
blow.
DNR Wildlife Resources, “Woodpecker Adapations,”
http://www.wvdnr.gov/Wildlife/Woodpecker.shtm
Key Questions:
A key question that many who’ve marveled
at nature ask:
• How do we explain the fact that animals
seem so well adapted to their
environment?
• In other words, how did they get body
parts and behaviours (adaptations) that
are exactly what they need to survive?
• One answer is that God made them that
way (the answer both of Biblical theology
and natural theology (the argument from
design))
• But what is the scientific answer?
Jean-Baptiste Lamarck
(1744-1829), a French 19th
century naturalist before
Darwin, developed a theory
called “the inheritance of
acquired characters,” which
explained both adaptation
and evolution.
(NB: He didn’t invent the idea
but was the first to apply it to
evolution and adaptation)
Lamarck’s Theory
It included the idea of “use and
disuse of parts”.
The more you use a body part, the
more it is amplified.
Or, vice versa, “use it or lose it…”!
Lamarck’s Theory
• Lamarck thought characteristics acquired
in an animal’s lifetime (e.g., longer neck of
giraffe) could be passed down by heredity.
• This theory is thus called “the inheritance
of acquired characters”
Lamarck’s Theory
Lamarck distinguished between two “Laws”:
First Law
•
In every animal which has not passed the limit of its development, a more frequent and continuous use of any
organ gradually strengthens, develops and enlarges that organ, and gives it a power proportional to the length of
time it has been so used; while the permanent disuse of any organ imperceptibly weakens and deteriorates it, and
progressively diminishes its functional capacity, until it finally disappears. (Lamarck, 113)
Second Law
•
All the acquisitions or losses wrought by nature on individuals, through the influence of the environment in which
their race has long been placed, and hence through the influence of the predominant use or permanent disuse of
any organ; all these are preserved by reproduction to the new individuals which arise, provided that the acquired
modifications are common to both sexes, or at least to the individuals which produce the young. (Lamarck, 113)
J.-B. Lamarck, Zoological Philosophy trans. Hugh Eliot (New York: Hafner Publishing Co., 1963)
•
•
•
These “Laws” distinguish between the acquisition of a trait and its inheritance but both are
necessary to explain how adaptation and evolution happen for Lamarck.
The former happened as a result of use/disuse of parts which was itself due to a changes in the
environment causing animal’s to respond with new needs and new habits.
The latter claimed that all bodily changes acquired by use and disuse were passed down by
reproduction.
Darwin’s Theory
• Darwin explains adaptation
as due primarily to natural
selection.
• However, he also used
Lamarck’s theory as an
additional, secondary
explanation!
Darwin and Lamarck
• Darwin’s evolution theory explains
adaptation and evolution itself as a result
of natural selection
• Lamarck’s evolution theory explains both
as due to the inheritance of acquired
characters.
More…?
For more on Lamarck and Darwin’s theories see:
•“Natural Selection” section in GT DTP ch. 3
•“6.2 Pre-Mendelian Theories of Heredity:
Lamarck’s Inheritance of Acquired Characters” in
GT DTP, ch 6.
•Natural Selection PowerPoint
•Feedback to Written Assignment 1 (from previous
semesters)
•Conduct independent research
The End