BIOL 1002 Crousillac Spring 2014 Exam 2 Learning Objectives Chapter 23 Invertebrates Understand the key features of animals Animals possess all of the following characteristics o Multi cellular o No cell wall o Obtain energy by consuming other organisms o Most reproduce sexually o They are motile at some point in the life cycle o They are able to respond rapidly to external stimuli Be able to explain the difference between radial and bilateral symmetry o Animals with radial symmetry can be divide into roughly equal halves by any plane that o Animal with bilateral symmetry can be divided into mirror image halves only along one passes through the central axis plane that runs down the midline Know the major animal phyla and distinguishing characteristics of each Phylum porifera o Sponges have a simple body plan found in most marine environments Immobile They may reproduce asexually by budding where the adult produce miniature versions of itself that drop off and assume an independent existence They may reproduce sexually through fusion of sperm and eggs o Sponges have no true tissues or organs The sponge body is perforated by tiny pores through which water passes and by fewer large openings through which water is expelled As water passes through the sponge oxygen is extracted and microorganisms are filtered out and digested by individual cells o Some sponges contain chemicals useful to humans A number of chemicals within sponges have proved to be valuable medicines The drug spongistatin is an emerging treatment for the fungal infection that sickens AIDS patients promising new cancer drugs Phylum Cnidarian o Cnidarians are well armed predators Includes sea jellies sea anemones corals and hydrozoans mostly marine and are all carnivorous predators lack true organs and have no brain but rather a network of nerves that controls movement and feeding behavior o Have stinging cells called cnidocytes that are used to capture prey and for defense Cnidocytes contain a finely coiled filament that is explosively expelled when the trigger is touched Some filaments inject poison into the prey Other either stick to or enlarge small prey The venom of some can cause extreme pain or death in humans o Jellyfish stings worse tentacles o The box jellyfish urinating on a jellyfish sting will not help ease the pain and may even make it Rinse the stings with seawater or vinegar and baking soda to deactivate the Then apply shaving cream to the sting area and shave the skin to remove excess tentacles If you re without a razor a credit card will work One of the 10 most venomous creatures on the planet Found mainly in ocean waters between Australia and Hawaii Stinging cells are ejected at an amazing speed Accelerates at a rate of over 1 million times the force of gravity Rocket launches are about 5 times Sting is painful enough to induce shock or cardiac arrest in a human Over 100 Phylum Ctenophora people killed o Comb jellies belong to the phylum Ctenophora Appear similar to cnidarian but use cilia to move Eat tiny invertebrate animals that they capture with sticky tentacles Hermaphroditic and can release both eggs and sperm into seawater fertilized eggs gradually develop into larvae and then adults Phylum Platyhelminthes o May be parasitic or free living Include flatworms Many species are parasites and live within the body of another organism Non parasitic free living flatworms inhabit aquatic and moist terrestrial habitats Can reproduce both sexually and asexually most are hermaphrodites o Have organs but no respiratory or circulatory systems Have a distinct head with sensory organs Their nervous system consist of clusters of nerve cells called ganglia in the head forming a simple brain In the absence of respiratory system gas exchange is accomplished by diffusion between body cells and the environment o Some flatworms are harmful to humans Tapeworms can infect people who eat improperly cooked beef pork or fish that has been infected by the worms Tapeworms attach themselves to the lining of the intestine Can grow up to 20 feet in length by absorbing nutrients in the intestine Phylum Annelida o Includes segmented worms Body is divided into a series of repeating units Segmentation Each segment is identical to the others allows for complex movement Most reproduce sexually Some species are hermaphroditic other have separate sexes During copulation sperm are transferred from one individual to the other In hermaphroditic species sperm transfer may be mutual with each partner donating and receiving sperm Some annelids reproduce asexually by fragmentation the body breaks into two piece each of which regenerates the missing part Phylum Mollusca o Most mollusks have shells o Includes clams snails and cephalopods o Mollusks reproduce sexually Some species have separate sexes Other are hermaphroditic o The three classes are Gastropods Bivalves Cephalopods o Gastropods are one footed crawlers Includes snails and slugs Muscular foot for locomotion May possess a shell but not all gastropods are shelled They feed using a radula a flexible ribbon studded with spines that scrape algae from rocks or grasp larger plants or prey o Bivalves are filter feeders Includes scallops oysters mussels and clams Live in fresh water and marine habitats Have two shells that can be clamped shut by a strong muscle Filter feeders and use gills for both feeding and respiration Most have a muscular foot used for burrowing or for attaching to rocks o Cephalopods are marine predators The cephalopods include octopuses nautiluses cuttlefish and squids All cephalopods are predatory carnivores and all are marine Have large complex brains and are capable of learning Possess highly developed sensory systems May have a shell E g nautiluses most do not o Are they smart Very good at manipulating objects with their tentacles An octopus in captivity will learn very quickly how to unscrew the lid to a jar with a fish inside This is similar to what an octopus would do in the wild to retrieve a clam from its shell Cephalopods have tentacles with chemosensory abilities and suction disks The tentacles are used for locomotion and to capture prey These animals are able to move rapidly by forcefully expelling water from a body cavity Some release ink like substances as a distraction to escape from predators Phylum Arthropoda o Arthropods are the most diverse and abundant animals Includes insects arachnids myriapods and crustaceans Arthropods have appendages and an
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