Learning Outcome G4

1. Learning Outcome G4 Phylum Mollusca, Echinodermata & Arthropoda

2. Learning Outcome G4 • Analyse the increasing complexity of the Phylum Mollusca, the Phylum Echinodermata, and the Phylum Arthropoda

3. Student Achievement Indicators Students who have fully met this learning outcome will be able to: • Examine members of the Phylum Mollusca and describe their unifying characteristics • Describe how molluscs carry out their life functions • Examine members of the Phylum Echinodermata and describe their unifying characteristics • Describe how echinoderms carry out their life functions • Examine members of the Phylum Arthropoda and describe their unifying characteristics • Describe how arthropods carry out their life functions • Compare how molluscs, echinoderms, and arthropods have evolved to adapt to different niches

4. Phylum Mollusca

5. Classification • Kingdom Animalia • Phylum Mollusca • Class Polyplacophora • Class Cephalopoda • ClassGastropoda • Class Bivalvia

6. Characteristics • An important food source to both humans and other animals • Great variety between species • There are 7 classes of molluscs; we are going to examine the 4 major classes. • All molluscs are protostomes, which means that during embryological development the first opening to develop is the anus. • Have a free-swimming ciliated larva, which uses a band of muscle to bring food towards the mouth • Largest invertebrate phylum

7. Body Plan • Great variation within this phylum, although they have inherited a common body plan form their ancestors. 1. Foot • Muscular and function in locomotion • In cephalopods the head has become a modified head and tentacles 2. Mantle • A folded tissue that folds down around some or all of the body 3. Shell • Made up of calcium carbonate • Can be internal or external

8. Body Plan 4. Gills • Specialized respiratory structure that arises from outgrowths of the mantle wall 5. Visceral mass • Internal organs consisting of the gut, kidney, heart and reproductive organs. 6. Radula • a unique rasping “tongue-like” organ with hard teeth that are used to scrape up food

9. Radula

12. Ecological Roles • Generally free-living and inhabit all known aquatic and terrestrial ecosystems. • They are a food source for fish, starfish, birds, humans and a variety of other mammals. • Molluscs live as predators, herbivores, detritus feeders, parasites and form other symbiotic relationships with other organisms. • Bivalves, such as mussels perform an important ecological role of recycling huge amounts of sediment back into the environment.

13. Ecological Roles • Also their empty shells often provide homes for other invertebrates. • Molluscs play a critical role in the food chain • Drastically impacted by oil spills and pollution because most molluscs are filter feeders and these pollutants smother the gills or enter the digestive tract causing inflammation and a variety of digestive problems. • Oil can also fill the mantle causing tumors and irritating muscle.

14. Class Polyplacophora(the chitons) • Marine animals that eat algae or small animals growing on rocks near the shore or in the deep ocean • Most of their bottom surface is taken up by a large muscular foot. • The upper surface consists of 8 overlapping shell valves, which provide protection.

17. ClassGastropoda(the Gastropods) • Make up the biggest group of molluscs • Generally have large coiled shell, and this group includes snails and whelks. • Their foot has a hard plate which fills the opening of the shell when the foot is withdrawn and protects the soft body.

19. Class Bivalvia (the bivalves) • Includes clams, mussels, oysters and scallops • Important food supply for humans • The body of bivalves is held between two protective valves connected by a ligament that holds them apart along one edge. • Two strong muscles pull the valves together. • Bivalves do not move due to their large, heavy shells. • Complex system for filter feeding; that involves the use of gills

20. Class Bivalvia (the bivalves) • These gills are large and covered with cilia; the water circulates between the valves and carries many small particles of food into the mollusc. • This water passes across the gills, and the food particles are filtered out and embedded in the mucus. • Strings of mucus and food are then moved toward the mouth by the cilia. • Digestion occurs in the stomach and undigested material exits via the anus

25. Class Cephalopoda(the cephalopods) • Most complex mollusks and includes squids, nautiluses, and octopods. • Only the nautiluses have a complex external shell • Octopods have 8 equal appendages all equipped with suckers and tentacles. • Squids have 10 appendages, two of which the tentacles are longer and have tentacles on expanded tips. • The tentacles trap and grasp prey, which are drawn towards the mouth. • Great predators due to efficient respiratory and circulatory systems • Have a muscular mantle which is well designed for water flow.

26. Class Cephalopoda • The squid’s body is stream-lined and maintains its shape, with the aid of a pen. • An octopod has no shell and the body is incredibly flexible. • A pen is the internal remnants of a shell. • Both the squid and octopus use water jets that are powered by contractions of the mantle for fast swimming. • Nautiloidsswim with the aid of their numerous arms • Both squids and octopods have digestion occur in their stomach, which is aided by enzymes secreted by the digestive glands. • Nutrients are absorbed in the stomach and some additional absorption occurs in the starting of the small, coiled intestine.

27. Class Cephalopoda • Undigested material is excreted into the mantle cavity • The circulatory system of a cephalopod is closed and capable of maintaining a high flow rate and blood pressure. • The large, extensively folded gills have a separate “gill heart” to pump blood back to the “systemic heart” which pumps it out of the body. • The cephalopods nervous system is also highly developed with a large brain that contains several ganglia. • In the octopus the brain has 10 lobes, and the animals are good learners. • Octopods have been trained to solve simple problems and have the ability to remember

28. Class Cephalopoda • Squids and octopods have image forming eyes, which are very close to the eyes of vertebrates but have a different embryonic origin (convergent evolution). • Complex eyes are crucial to the survival of these predatory animals which depend of vision to find their prey. • Cephalopods are dieoccius and fertilization is internal. • In squid the fertilized eggs are deposited in a gelatinous capsule and both the male and female die after mating. • In octopods, the fertilized eggs are attached to the roof of the cave or crevice in which the female live and she guards and cleans them for several months until they hatch. • During this time the female eats little or nothing

33. Phylum Echinodermata

34. Classification • Kingdom Animalia • Phylum Echinodermata • Class Asteroidea • Class Ophiroidea • ClassEchinoidea • Class Holothuroidea • Class Crinoidea

35. Characteristics • Generally large and live on the bottom of large bodies of water • Usually marine • Have spiny skin, which is a key characteristic of this group • Have radial symmetry and many have 5 similar body segments around a central core. • The larval sate is bilaterally symmetrical • The development of echinoderm eggs is similar to the development of chordate eggs.

36. Characteristics • Deutrostomes • Have a endoskeleton that is made up of calcified plates covered by an epidermis • These plates may be a single plate • Example – starfish have a single flexible plate or a fused solid shell has in sea urchins. • Has a complicated water vascular system. • The coelom is separated into two parts: • the perivisceral coelom which plays a role in circulation and excretion • The hydrocoelwhich function in locomotion and feeding

37. Ecological Roles • Bottom dwellers of all ocean • May live in large numbers • Recycle nutrients in ecosystems by feeding on dead and decaying materials • Starfish are important marine carnivores that control the population of other animals • However large population ofechinodermscan be troublesome, they can wipe out whole populations of molluscs. • They can also cause severe damage to coral reefs • Sea urchins are essential to the control and distribution of algae • Non parasitic but are home to many parasites.

38. Class Asteroidea (sea stars) • 1800 species • Have tube feet which help in movement and feeding. • Tube feet are part of the water vascular system • At the end of each arm, starfish have a microscopic eyes that can only see light and dark. • The mouth is located on the underside of the stomach • Able to regenerate • Feed on mussels and other molluscs. • Wide diversity in body plan and feeding • Pentaradialsymmetry • Bodies made of calcium carbonate which form ossicles.

42. Class Ophiuroidea(brittle stars) • Closely related to sea stars • 5 long slender whip-like arms • Arms can be up to 60 cm

44. ClassEchinoidea(sea urchins) • Spiny globular animals • Move via tube feet • Vary in color • Food source for sea otters and seals • Sea urchin eggs are a human delicacy

47. Class Holothuroidea (sea cucumbers) • Elongated both with leathery skin • Sends hormones through the water to attract a mate • Body contains collagen, so the body can looses and tighten at will which allows this organism to move through small spaces. • Can expose it’s intestines to predators when feeling threatened, this is known as eviceration. • Form large herds and can form symbiotic relationships

50. Class Crinoidea (sea lilies or feather stars) • Live in shallow and deep water • Mouth is on the surface surrounded by feeding arms • Generally attached to substrate but can be unattached.