Deck 13: Arthropods

Question 1

Filter feeding is a very common way to collect food from water, but this method is rarely used on land. Why might webspinning spiders be considered filter feeders?

Answer 1

Filter feeders are classified as the group of suspension feeding animals, which feed by straining the food material and suspended matter from water. Some of the animals use this method for feeding baleen whales, clams, krill, and some sharks. Few birds such as ducks and flamingo are also considered as the filter feeders.
They are often described as the engineers of the ecosystem as they have an important role in clarifying the water. A spider web is also known as the cobweb, which is the device formed by the web-spinning spiders. They form this web from a proteinaceous spider silk secreted from their spinnerets.
This is meant for catching the prey. Insects trapped in the spider web serve as the source of nutrition to the spider. The spider webs are the only terrestrial equivalents of the filter feeders. Spiders have different glands to secrete different types of silks. The spider web allows the spider to catch their prey without spending much of energy running behind them.
This is one of the effective methods for collecting the food. However, the spinning of the web is a costly method as it requires the huge amount of silk. Few spider species also secrete glue like substance along with the silk, which helps in preventing the escape of the food matter from the web.

Question 2

List some characteristics of arthropods that clearly distinguish them from Annelida.

Answer 2

The phylum Arthropoda includes the crustaceans, arachnids, insects, and myriapods. They are generally characterized by their cuticle and jointed legs made up of chitin, which is often mineralized with the calcium carbonate. The body plan of the arthropod is composed of the segments and each of the segments has the pair of appendages attached.
Their exoskeleton is replaced by the process of shedding or molting. The arthropods have an open type circulatory system. They have short as well as open-ended arteries. The arthropod lacks the acceleration sensors and balance. The phylum Annelida is composed of approximately 17,000 species of leeches, ragworms, and earthworms.
The annelids are the coelomate, bilaterally symmetrical, triploblastic, and invertebrate organisms. They use parapodia for the locomotion. Their body consists of various segments. The arthropods and annelids are similar as they have segmented body plan. They share more differences in comparison to the similarities.
The annelids lack the tagmata, whereas arthropods do have tagmata. The arthropods have specialized appendages to fly, eat, walk and swim. Coelom is also found present in the arthropods, whereas annelids lack the coelom.

Question 3

Name the subphyla of arthropods, and give a few examples of each.

Answer 3

The subphyla of Arthropods with examples are -
1) Subphylum Trilobita
Examples - Isotellus, Harpes, Walliserops, Phacops
2) Subphylum Chelicerata
Examples - Limulus, Pycnogonum, Latrodectus
3) Subphylum Myriapoda
Examples - Julus, Scutigera, Pauropus, Scutigerella
4) Subphylum Crustacea
Examples - Branchinecta, Daphnia, Caligus, Balanus, Cancer
5) Subphylum Hexapoda
Examples - Gerris, Halobates, Drosophila, Danaus

Question 4

Much of the success of arthropods has been attributed to their cuticle. Why? Describe some other factors that probably contributed to their success.

Question 5

What is a trilobite?

Question 6

What appendages characterize chelicerates?

Question 7

Briefly describe the appearance of each of the following: eurypterids, horseshoe crabs, pycnogonids.

Question 8

Describe the mechanism of each of the following with respect to spiders: feeding, excretion, sensory reception, webspinning, reproduction.

Question 9

Distinguish each of the following orders from each other: Araneae, Scorpionida, Opiliones, Acari.

Question 10

People fear spiders and scorpions, but ticks and mites are far more important medically and economically. Why? Give examples.

Question 11

The only venomous crustacean known is a small, blind cave-dwelling animal called a remipedian. Which other arthropods use venoms?

Question 12

What features of pentastomids support their current phylogenetic position as close relatives of fi shlice (branchiurans)?

Question 13

Distinguish among Ostracoda, Copepoda, and Thecostraca.

Question 14

Copepods sometimes are called "insects of the sea" because marine planktonic copepods probably are the most abundant animals in the world. What is their ecological importance?

Question 15

Define each of the following: swimmeret, maxilliped, cheliped, nauplius.

Question 16

Describe molting in Crustacea, including the action of hormones.

Question 17

Explain the mechanism of each of the following with respect to crustaceans: feeding, respiration, excretion, circulation, sensory reception, reproduction.

Question 18

Distinguish the following from each other: Diplopoda, Chilopoda, Insecta.

Question 19

Define each of the following with respect to insects: sclerite, tergum, sternum, labrum, hypopharynx, haltere, instar, diapause.

Question 20

Explain why wings powered by indirect flight muscles can beat much more rapidly than those powered by direct flight muscles.

Question 21

What different modes of feeding do insects use, and how are these reflected in their mouthparts?

Question 22

Describe each of the following with respect to insects: respiration, excretion and water balance, sensory reception, reproduction.

Question 23

Explain the difference between holometabolous and hemimetabolous metamorphosis in insects, including the stages of each.

Question 24

Describe and give an example of each of four ways insects communicate with each other.

Question 25

What castes occur in honey bees and in termites, and what is the function of each? What is trophallaxis?

Question 26

Name several ways in which insects benefit humans and several ways in which they are detrimental.

Question 27

For the past 50 or more years, people have relied on toxic insecticides for control of harmful insects. What problems have arisen as a result? What are the alternatives? Define integrated pest management.

Question 28

What evidence suggests that metamerism evolved independently in Annelida and Arthropoda?

Question 29

We hypothesize that the earliest insects were wingless, making lack of wings the primitive condition. Does winglessness characterize a hexapod class? In what sense is it useful for classification?

Question 30

Distinguish the Mandibulata hypothesis for arthropod evolution from the Myriochelata hypothesis.