Question

T-Mobile 46% . 10:33 PM Done Lab13 Answer Sheet-1.docx -Dipteran (either one) Lepidopteran Hymenopteran -Complete dissections of Ascaris, crayfish, grasshopper Questions 1. What character(s), besides DNA, suggest that arthropods are closely related to nematodes? 2. What trait distinguishes a male from a female Ascaris, crayfish, grasshopper? 3. Which appendages of a crayfish function directly in consuming food? 4. Describe how the thoracic appendages of a grasshopper. How many are there, and what is the function of each pair?

Answer 1

1 . ARTHROPODS ARE CLOSELY RELATED TO NEMATODES AS:

• They both have cuticle which provides a tough and flexible exoskeleton thus protecting them from predators and water loss.
• Both arthropods and nematodes undergo ecdysis. (Exoskeleton must be shed periodically for the continuous growth of animals) . They are termed as ecdysozoa which reflects shared characteristic of molting.

2. DISTINGUISHING FEATURES BETWEEN MALE AND FEMALE:

Ascaris:

• Female -long around 20-40 cm , male - usually thinner around 15-30 cm.
• Female - posterior end is straight; males- posterior end is hooked.
• Female - posterior opening does not have any specialized structures; males- pineal spicules near its posterior opening

Crayfish

• Males are generally larger in size than females.
• Males have a larger chelae and narrower abdomens while females have broader abdomen.
• Male crayfish carry an extra set of swimmerets (enlarged and hardened) while females have a small hole behind swimmerets.

Grasshopper:

• Males are smaller than females.
• Abdomen of male is rounded and dips into a curve thus tapering at a slightly raised angle while females have a straight abdomen with no curves.
• Males have hard and smooth plate on abdomen's end while females have four pointed protrusions at the end of their abdomens.

3. Appendages of crayfish that help in consuming food:

• Mandibles crush food
• Two pairs of maxillae hold solid food and tear it.
• FIRST THREE MAXILLIPEDS HOLD FOOD DURING EATING

4. Thoracic appendages of grasshopper:

• LEGS - First 2 pairs - walking and last two pairs for jumping
• WINGS - Forewings - leathery appearance and protect the hind wings