Phylogenetics: What are three evolutionary lineages with Superclass Hexapoda, and what are distinguishing characteristics of each?
There are several ways you can address this question. Pick three lineages, or monophyletic groups, and to be consistent, you should pick lineages of the same taxonomic level (division, subdivision, order, etc.). For each, the distinguishing characteristics may be features that evolved that separated that particular lineage from other monophyletic groups. For example, I thought of using endopterygotes, polyneopterans, and paraneopterans, as three monophyletic groups within the Neopterans. The characteristics for these broad subdivisions should be very general - polyneopterans have caudal cerci, chewing mouthparts, and incomplete metamorphosis, paraneopterans have incomplete metamorphosis and sucking mouthparts, and endopterygotes have complete metamorphosis.
More specifically, you could choose any three orders as evolutionary lineages, as long as you could describe the distinguising characteristics of each, which would allow someone to identify a member of each lineage as accurately belonging to that lineage.
Morphology: Describe the basic structure of the meso- or metathoracic segment of a neopteran.
Each of these two segments will most likely have a pair of legs and a pair of wings. There are exceptions, of course, such as in the secondarily wingless fleas and lice, and the legless larvae of some endopterygotes. These two segments are often partially or completely fused into the pterothorax, and they usually have heavily sclerotized nota, pleura, and sterna. In many active neopterans, musculature is well-developed, and flight muscles take up a large portion of the pterothorax, internally.
Morphology: Describe the leg adaptations and habits of three insect families or orders that have different types of legs.
Again, there are a variety of ways to address this question. You must first select taxa of insects that have leg variations at the species level (forelegs, midlegs, and hindlegs are not all the same). For instance, all Mantodea (order level) have raptorial forelegs and walking mid/hindlegs. Grasshoppers of several families (Acrididae, Tettigoniidae, for instance), have walking fore and midlegs, and saltatorial hindlegs. Bees in the family Apidae have modified hindlegs, used to collect pollen.
Evolution: Define holometabolism, and discuss the currently accepted hypothesis for the evolution of holometabolism.
Holometabolism is a form of development in which the insect has egg, larval, pupal, and adult stages. Dramatic changes occur during the pupal stage to radically reorganize tissues to alter the animal from larval form to adult. It is also known as complete development or complete metamorphosis, and occurs only in the endopterygotes. The most recent hypothesis is that the pronymph stage of hemimetabolous and ametabolous insects is the evolutionary precursor to the holometabolous larva, and the holometabolous pupa is the sole nymphal stage. The pronymph thus evolved the ability to feed, and as it grew, required molting, and hence larvae have multiple instars. The pupa is a reduced version of the hemimetabolous nymph, in the sense that it has only one instar, rather than multiple, as the nymph does.
What are advantages and disadvantages of possessing an open CS?
Advantages include...
What other structures would need to evolve along with this system, and how does this affect the cost/benefit analysis?
In order to be an active animal, rather than a sedentary one, there needs to be an efficient mechanism of gas exchange. An open CS is probably not going to be that efficient, so another mechanism or system must exist. That system is the tracheal system in insects. The cost of not having an efficient or fast way to move materials in the hemolymph is thus not as much of a factor. Additionally, there is a possibility that the open CS of arthropods evolved along with the exoskeleton. In invertebrates without an exoskeleton, maximum size is an issue, as is support. Those other invertebrates often have hydraulic skeletons, and in larger ones, they also have closed CS.
Describe the structure and function of the following systems:
Nervous:
Respiratory:
Digestive: The alimentary canal is a tube, open at both ends. There are three major sections, the foregut, midgut, and hindgut. The foregut and hindgut are lined with cuticle, and are thus molted with the rest of the cuticle during molting. The foregut contains the pharynx, esophagus, crop, and proventriculus.
How might the endocrine system have played a role in the evolution of endopterygotes?
There's the hypothesis that larval stages of endopterygotes are expanded pronymph stages of hemimetabolous insects. If true, then...
Explain the differences between a primary host, an amplifying host, and a reservoir host
A primary host is one on which the ...
Draw a generalized arbovirus disease cycle that includes a primary cycle, a secondary cycle, dead-end hosts, and transgenerational transmission
A generalized cycle...
What biological factors of a reservoir host might make it a good reservoir for disease?
Reservoir hosts that are excellent reservoirs are long-lived (at least longer than the period of time when vectors are unavailable, seasonally), they remain infective or become infective at the right time for transmission back to the vector, and ...
Provide an example of each of the four main categories of parasite vectored by arthropod, and an example of an insect that vectors such a parasite.
The four main categories are nematodes, bacteria, viruses, and protozoans.
What is the difference between a parasite and a pathogen?
A parasite lives off a host, a pathogen is a parasite that causes disease
