Guidelines for Take Home Exam 2
There are 6 questions for consideration in this exam. Undergraduate students must
answer 3 questions. Graduate students must answer 4 questions. Your answers to these
questions should reflect the knowledge you gained in class and knowledge you gained
from reading various publications. Since this is an “open book” exam, we expect you to
cite at least two sources per answer from the primary literature (journal publications, not
textbooks or lecture notes). There is no word limit or page limit to answering any
question, but please make your answers as succinct as possible.
New Rule for this Exam: Each question-answer pair should be placed on a separate
page (piece of paper). As always, grammar is important. For undergraduates, each
answer is worth 33% of the exam grade; for graduate students, each answer is worth 25%
of the exam grade. A hardcopy of your answers is due in the Hochberg mailbox by 9am
5/14/12.
** Please copy the questions you will be answering into a separate file prior to
answering them.
1. There is mounting evidence that the clade Hexapoda is derived from within the
Crustacea (as opposed to being a sister taxon of Crustacea), making the subphylum
Crustacea paraphyletic. What makes this so interesting is that it means insects (and the
related “collembolans”) had a definite aquatic (probably marine), crustacean ancestry.
Insects are however quite a bit different from most crustaceans in terms of overall body
plan organization and the fact that most adults are fully terrestrial. From what you’ve
learned in class (and using primary sources), briefly document what kinds of evolutionary
changes led to the insect body plan from a crustacean ancestry. Be sure to include any
mechanisms we discussed (molecular, developmental) that could serve as evidence for
showing how the body plans changed from crustacean-like to insect-like (you may ignore
the “collembolans” if you choose).
2. Suppose during an oceanic research expedition you come across some tiny (2-4 cm)
plantkonic organisms that look like this (note the lack of compound eyes):
You’ll be spending several weeks out at sea and have all the research tools (dissection
tools, all types of microscopes, stains, aquaria, etc.) necessary to culture the animals and
perform some detailed morphological analyses (molecular sequencing is unavailable
aboard the ship). With these tools at hand, how might you go about answering the
following questions? A. To what subphylum does this animal belong? B. To which major
taxonomic group does this animal belong in its respective subphylum? Remember, there
is a great amount of variation (both morphologically and ecologically) in most groups, so
a perfect taxonomic match might not be possible; nevertheless, the relationships you
propose should be plausible. Be sure to mention how you would go about determining the
answers to these questions as opposed to just listing characteristics that might be
indicative of a particular group of animals.
3. The Myriapoda is a collection of worm-like segmental arthropods with a fairly
homonomous body plan. Still, there are important morphological and ecological
differences between members of the two major clades, Chilopoda and Diplopoda, which
figure prominently in their diversification and ecological success. For this question,
describe the major differences between the two groups and how their morphologies are
adapted for each of the major lifestyles (lifestyle = their relationship to the environment
including how they move and feed).
4. Silk production is a hallmark of spider biology, and is considered a key innovation that
sparked the diversification of this mega-diverse chelicerate order. Using evidence from
morphology and molecules, describe how spider silk production is different from insect
silk production and explain how silk use has played an important role in spider evolution
and species diversification.
5. Venoms have independently evolved in different arthropod lineages as well as in other
invertebrates and vertebrates. Across these organisms, venom production exhibits
convergence at several levels of biological organization, from molecules to morphology.
First define what venom is, and then explain how venom production is similar and
different in two animal lineages that have independently evolved venom. Provide specific
examples of the evidence for convergent evolution. Make sure to use at least one type of
venomous arthropod in your answer; restricting your answer to only two independently
evolved arthropod venoms is also acceptable.
6. Eusociality is perhaps the most complex form of social behavior in an organism and is
mostly known from species in two insect orders (Isoptera and Hymenoptera). One
pathway to evolving eusociality may have involved a transition from sub-social
behavioral systems. Define the terms eusociality and sub-sociality, and explain how
eusociality may have evolved from sub-sociality. Use a specific insect species to
illustrate the key features of eusociality.