Exam 3 Annelida, Nematoda, Arthropoda

What are the distinct paired appendages of annelids called?

Parapodia

What are setae and what is their function in annelids?

Bristles that aid in locomotion.

What are the two parts of the head in annelids?

Prostomium and Peristomium.

What is the pygidium in annelids?

The terminal segment bearing the anus, where new segments form just anterior to it.

How does the coelom form in annelids?

By schizocoely.

What is metamerism in annelids?

The serial division of the body into functional segments.

What are the advantages of metamerism?

Each segment can develop a complete set of organ systems, damage to one segment may not be fatal, and locomotion is more effective due to independent segment movement.

What do earthworms primarily eat?

Organic matter.

What feeding strategies do polychaetes exhibit?

Some are filter feeders, while others are active predators.

What types of feeding strategies do leeches have?

Some are parasitic and some are predators.

How do annelids reproduce?

Both asexually (by budding or fission) and sexually (by cross-fertilization).

What is the process of asexual reproduction in annelids?

Budding (fragment grows off) or fission (organism splits into two).

Where can annelids be found?

In marine, freshwater, and terrestrial environments.

What type of cleavage occurs during embryonic development in annelids?

Spiral cleavage.

What is a trochophore larva?

A free-swimming larval stage that some annelids develop through.

Do all annelids have a free-living larval stage?

No, some directly develop without a free-living larval stage.

What should you be familiar with regarding annelids?

The different classes, orders, and families of annelids.

What are the two main classes of polychaete annelids?

Class Errantia and Class Sedentaria.

What are the characteristics of Class Errantia?

Mobile, active polychaete annelids, including clam worms and sea mouse worms, that are predators or scavengers, lack a clitellum, are dioecious, have trochophore larvae, and possess prominent heads and parapodia with many setae.

What is the significance of setae in annelids?

Setae are bristles that aid in locomotion and are made of chitin.

What are parapodia and their functions in annelids?

Parapodia are paired, fleshy, lobe-like appendages that extend from the sides of body segments, aiding in locomotion and sometimes respiration.

What defines Class Sedentaria?

Includes many polychaete and oligochaete worms that live in tubes or burrows, such as earthworms and leeches, many of which are filter feeders or detritivores.

What is the clitellum and its role in Order Clitellata?

The clitellum is a glandular structure that produces mucous to hold individuals together, forms a cocoon for gametes, and is present at some stage in all members.

What is the reproductive strategy of members of Order Clitellata?

They are hermaphroditic and engage in cross insemination.

What are the characteristics of terrestrial oligochaetes?

They are detritivores important for nutrient recycling and soil aeration, have a fleshy protomium, lack parapodia, and possess four pairs of chitinous setae.

Describe the circulatory system of earthworms (Family Lumbricidae).

They have a closed circulatory system with dorsal and ventral vessels and aortic arches for pumping.

How do earthworms respire?

Respiration occurs through the integument.

What is the digestive tract structure of earthworms?

It is divided into functional regions: pharynx, crop, gizzard, and intestines, with a typhlosole to increase surface area for absorption.

What distinguishes freshwater oligochaetes from terrestrial forms?

Freshwater oligochaetes are typically smaller, have longer and more abundant setae, and better-developed heads and sense organs.

What are the characteristics of leeches (Family Hirudinidae)?

Leeches are dorsoventrally flattened, have anterior and posterior suckers, reduced coelom and segmentation, lack septa, and most lack setae.

What is the feeding strategy of leeches?

Leeches can be parasitic or predatory, with some being temporary or permanent parasites.

What is the Clade Ecdysozoa?

It is one of the two major protostome clades, named for the process of molting the cuticle (ecdysis) during growth, regulated by the hormone ecdysone.

How do locomotion mechanisms differ between nematodes and annelids?

Nematodes have only longitudinal muscles for side-to-side movement, while annelids have both circular and longitudinal muscles allowing them to lengthen and shorten their bodies.

What is the body plan of nematodes?

Nematodes have a cylindrical body shape, a complete digestive system, and a body covered by a tough cuticle.

What is the role of ecdysone in Ecdysozoa?

Ecdysone regulates the molting process (ecdysis) during growth.

What is the significance of the trochophore larvae in annelids?

Trochophore larvae are a developmental stage in some annelids, particularly in Class Errantia.

What is the ecological role of earthworms in soil?

Earthworms are important for nutrient recycling and aeration of the soil.

What are the main feeding strategies of freshwater oligochaetes?

They are primarily detritivores or graze on algae, with some feeding on suspended particles using cilia.

What is the body shape of unsegmented worms?

Cylindrical body that is circular in cross section.

What are unsegmented worms commonly known as?

Roundworms.

What type of skeleton do unsegmented worms possess?

A fluid-filled pseudocoel that acts as a hydrostatic skeleton.

What is the function of the collagenous cuticle in roundworms?

It contains the high pressures created within the pseudocoel.

What are the main parts of the digestive tract in unsegmented worms?

Pharynx, intestines, and rectum.

How does the pharynx function in roundworms?

It is used to suck food into the mouth.

What type of muscles do unsegmented worms have?

Bands of longitudinal muscle beneath the hypodermis; there are no circular muscle layers.

What is the dietary difference between parasitic and free-living roundworms?

Parasitic roundworms eat fluids and tissues of hosts, while free-living roundworms feed on bacteria, larger prey, fungi, or algae.

What are the reproductive strategies of unsegmented worms?

Most are dioecious, some are parthenogenetic, and some are hermaphroditic.

What is the dauer form in roundworms?

A juvenile form adapted for dispersal that does not feed.

Where can free-living unsegmented worms be found?

In freshwater, marine, and moist terrestrial environments, commonly in topsoil.

What distinguishes acoelomates, pseudocoelomates, and coelomates?

Acoelomates lack a body cavity, pseudocoelomates have a body cavity not completely lined by mesoderm, and coelomates have a true coelom completely lined by mesoderm.

How does locomotion differ between nematodes and annelids?

Nematodes only have longitudinal muscles for side-to-side movement, while annelids have both circular and longitudinal muscles for lengthening and shortening their body.

Why is C. elegans important as a model organism in biology?

It is the only animal whose complete cellular development is known and the first animal whose genome was fully sequenced.

What is the habitat and lifecycle of Ascaris lumbricoides?

Lives in the small intestines; eggs are spread through feces; juveniles enter the bloodstream and return to the intestines through the lungs.

How do hookworms infect their hosts?

Juveniles burrow through the skin, pass through the bloodstream to the lungs, and then to the intestines.

What are the effects of pinworms and where do they reside?

They cause relatively mild effects, occupy the large intestines and cecum, and lay eggs outside the anus, causing irritation.

What disease does Trichinella spiralis cause and how is it transmitted?

It causes trichinosis; juveniles develop inside skeletal muscle cells and are passed to a new host when this tissue is consumed.

What is the life cycle of filarial roundworms?

They have a two-host life cycle with definitive hosts (vertebrates) and intermediate hosts (mosquitoes), causing diseases like elephantiasis and river blindness.

What are the basic characteristics of the Phylum Nematomorpha?

They are known as horsehair worms, typically parasitic in their juvenile stage and free-living as adults.

What is the diameter range of horsehair worms?

0.5-3 mm

What is the maximum length that horsehair worms can reach?

Up to 1 meter

What is the life stage of horsehair worms that is parasitic?

Juveniles

What type of hosts do juvenile horsehair worms infect?

Arthropod hosts

What environments do horsehair worms require?

A moist environment, including freshwater and marine forms.

What are the basic characteristics of the Phylum Tardigrada?

Microscopic, segmented bodies; resilience to extreme environments; feed on algae, fungi, and other vertebrates.

How do tardigrades exchange gases?

Through diffusion, as they lack circulatory and respiratory systems.

What is cryptobiosis in tardigrades?

A dormant stage in response to extreme conditions, allowing them to survive for decades.

What defines the Clade Ecdysozoa?

A monophyletic group defined by the ability to molt or shed their outer cuticle through ecdysis.

What are the key features of arthropods?

Segmented body, jointed appendages, cuticular exoskeleton, complete digestive tract, small coelom, and open circulatory system.

How do arthropods grow?

Through molting of the exoskeleton (ecdysis).

What type of circulatory system do arthropods have?

Open circulatory system with a dorsal contractile heart that pumps hemolymph.

What are the different methods of respiration in arthropods?

Through gills, trachea, or book lungs.

How do arthropods excrete waste?

Through malpighian tubules or glands located at the proximal end of appendages.

What is the structure of the nervous system in arthropods?

A brain and a double chain of ventral ganglia.

What is tagmosis in arthropods?

The grouping of body segments into different regions (tagmata) associated with specific functions.

What is the most diverse animal phylum?

Phylum Arthropoda.

Name the four extant subphyla of arthropods.

Chelicerata, Myriapoda, Crustacea, Hexapoda.

What are some examples of organisms in the subphylum Chelicerata?

Spiders and horseshoe crabs.

What organisms are included in the subphylum Myriapoda?

Centipedes and millipedes.

What is the one extinct subphylum of arthropods?

Trilobita.

What are the two main tagmata of Subphylum Chelicerata?

Cephalothorax and abdomen.

How many pairs of appendages do Chelicerata have, and what are their types?

6 pairs: 1 pair of chelicerae, 1 pair of pedipalps, and 4 pairs of walking legs.

What is a key characteristic of Chelicerata regarding mandibles and antennae?

They have no mandibles or antennae.

What are the two subclasses of Class Merostomata?

Eurypterida and Xiphosurida.

What are Eurypterida commonly known as, and what is their significance?

Sea scorpions, known only from fossils and went extinct at the end of the Paleozoic era.

What is the ecological role of Eurypterida?

They were predators in marine environments and may have been the first animals to move onto land.

What are Xiphosurida commonly known as?

Horseshoe crabs.

What is the significance of horseshoe crabs in biomedical research?

They are important for their blood, which is used to test for bacterial contamination.

What do horseshoe crabs eat?

Worms, molluscs, and other invertebrates.

What is the reproductive behavior of horseshoe crabs?

They spawn on sandy beaches, with large aggregations on the Atlantic coast.

What are the defining features of Class Pycnogonida?

Sea spiders with an elongated cephalothorax and reduced abdomen.

How do sea spiders feed?

They feed on soft-bodied invertebrates using a proboscis.

What is the diversity of Class Arachnida?

>80,000 species, including spiders, scorpions, mites, ticks, harvestmen, and sun spiders.

What is the primary feeding method of spiders in Order Araneae?

They are predators that feed on insects and other small animals, using fangs to inject venom.

How do spiders capture their prey?

Through ambush, webs, or pursuit.

What are the excretory and respiratory systems of spiders?

Excretion through malpighian tubules and coxal glands; respiration through trachea or book lungs.

What is the defining feature of Order Scorpionida?

They have a post abdomen that bears a stinger.

What distinguishes Order Opiliones (harvestmen) from other arachnids?

Their cephalothorax and abdomen are joined.

What are the characteristics of Class Insecta?

Most speciose group with >1 million species, ectognathous mouthparts, and three tagmata: head, thorax, abdomen.

What is the primary feature of Subphylum Crustacea?

They have biramous appendages and two pairs of antennae.

What is the ecological role of Myriapoda?

They occupy various niches as detritivores and predators.