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/diptera-blog/tags/biomimicry

Camouflage as a form of adaptationCamouflage as a form of adaptation

Camouflage is an amazing kind of adaptationCamouflage is an amazing kind of adaptation

Spot the crab here?

Spot the stick insect?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