Biology - Chapter 33 - An Introduction to Invertebrates - Review

Which of the following statements about bilaterian animals is TRUE?

* All bilaterians are triploblastic (have three germ layers). ((WHY: Review the following material: Bilaterian animals form an enormous clade whose members all have a two-sided or bilaterally symmetric form (unlike sponges and cnidarians). All bilaterally symmetric animals also are triploblastic. Bilaterians include both invertebrate and vertebrate animals. If you had trouble with this question, review the following material: Bilaterian animals form an enormous clade whose members all have tissues (unlike sponges) as well as a two-sided or bilaterally symmetric form (unlike sponges and cnidarians). All bilaterally symmetric animals also are triploblastic. Bilaterians include both invertebrate and vertebrate animals.))

Which of the following are thought to be most closely related to humans?

* sea stars ((WHY: Humans and sea stars are deuterostomes.))

Nematodes and arthropods are the largest ecdysozoan phyla. Which of the following statements are true?

* Arthropods are named for their jointed appendages. * Some nematodes are parasitic on humans. * Both nematodes and arthropods must molt in order to increase in size. * Both nematodes and arthropods possess an external covering, or cuticle. * Arthropods possess an open circulatory system. ((WHY: The ecdysozoans include nematodes, arthropods, and other phyla that have tough external coats, or cuticles, that must be shed as they grow. This process of shedding, or molting, is called ecdysis. Nematodes, or roundworms, are unsegmented pseudocoelomate worms that lack a circulatory system. Although most nematodes are free-living, some well-known nematodes, such as hookworms and pinworms, are parasitic. Arthropods have a reduced coelom and an open circulatory system. Arthropods have segmented bodies that enable specialization of body structures such as appendages.))

The phylum Arthropoda includes four major lineages: cheliceriforms (also called chelicerates); myriapods; insects and their relatives (together called hexapods); and crustaceans. Drag each word or phrase to the appropriate bin.

* CHELICERFORMS - arachnids - horseshoe crab - possess clawlike feeding appendages * MYRIAPODS - millipedes and centipedes - exclusively terrestrial * INSECTS - butterfly - wings allow flight - body divided into head, thorax, and abdonmen - three pairs of walking legs * CRUSTACEANS - primary aquatic - crabs and isopods - two pairs of antennae ((WHY: Cheliceriforms, which are named for their clawlike feeding appendages, called chelicerae, include sea spiders, horseshoe crabs, spiders, scorpions, ticks, and mites. Myriapods include millipedes and centipedes, which are terrestrial species. Crustaceans are primarily aquatic animals such as lobsters, crabs, and crayfish. Insects possess three body regions (head, thorax, and abdomen), may have one or more pairs of wings, and have six legs. Insects are the largest and most diverse group of arthropods, including numerous species of butterflies, beetles, flies, ants, and many others.))

Insects are the most diverse group of organisms, in terms of numbers of species, dominating terrestrial habitats. More than 30 orders of insects have been described, with the order Coleoptera being the largest. Classification is based on traits such as wings and mouthparts. All insects have a three-part body plan consisting of a head, thorax, and abdomen; three pairs of walking legs; and one or two pairs of wings. The chart below indicates defining characteristics for eight of the more than 30 orders of insects. Complete the chart by following these steps: Drag blue labels onto blue targets only to identify wing characteristics. Drag white labels onto white targets only to identify the type of development. Drag pink labels onto pink targets only to identify examples of insects in each order.

* COLEOPTERA - Hard forewings protect membranous hingwings - complete metamorphosis - beetles * DIPTERA - hindwings reduce to stabilizers - complete metamorphosis - flies * HEMIPTERA - thick forewings (except at tips) - incomplete metamorphosis - "true bugs" * HYMENOPTERA - membranous forewings and hindwings - complete metamorphosis - ants, bees, wasps * LEPIDOPTERA - wings have scales - complete metamorphosis - butterflies, moths * ORTHOPTERA - one pair leathery, one pair membranous - incomplete metamorphosis - grasshoppers, crickets * TRICHOPTERA - hairy wings - complete metamorphosis - caddisflies ((WHY: Insects and their relatives are the most species-rich group of living organisms. The diversity of characteristics such as wing shape, mouthparts, and reproductive tactics enable insects to live in most terrestrial and freshwater habitats. The evolutionary tree below shows the relationship between the phyla and subphyla within the clade Ecdysozoa, which includes animals with tough outer coverings that must be shed for growth to occur. Myriapods, cheliceriforms, crustaceans, and insects and their relatives (hexapods) together comprise the phylum Arthropoda, which is marked by jointed appendages, segmented bodies, and hard exoskeletons. Note that the tree does not show all phyla in the clade Ecdysozoa, nor does it show all orders of insects and their relatives in the subphylum Hexapoda.))

The animal phylum most like the protists that gave rise to the animal kingdom is __________.

* Porifera ((WHY: Evidence that supports this includes the lack of true tissue in sponges, and the close similarity between choanocytes and choanoflagellates.))

Which of the following statements correctly describes a characteristic of the phylum Platyhelminthes?

* They are dorsoventrally flattened. ((WHY: This is why they are also known as flatworms.))

Which of the following statements is true of annelids?

* They perform gas exchange across their skin. ((WHY: Cutaneous respiration occurs across their skins. Some annelids, such as the errantians, have lateral extensions (parapodia) which provide additional surface area for cutaneous respiration.))

A marine biologist dredges up a small animal from the bottom of the ocean. It is uniformly segmented, with short, stiff appendages and soft, flexible skin. It has a complete digestive system and a closed circulatory system, plus multiple true coeloms. Based on this description, it may be determined that the animal must be a(n) __________.

* annelid ((WHY: The description matches the characteristics of annelids.))

Members of the phylum Mollusca __________.

* are soft-bodied and often covered by a shell ((WHY: Members of the phylum Mollusca are soft-bodied and are often covered by a shell.))

What structure is responsible for gas exchange in most spiders?

* book lungs ((WHY: The extensive surface area of book lungs is a structural adaptation that enhances the exchange of O2 and CO2 between the hemolymph and air.))

Which of the following organisms have lophophores?

* ectoprocts and brachiopods ((WHY: Both ectoprocts and brachiopods have lophophore feeding structures.))

A hemocoel refers to a

* functional body cavity lined by tissues derived from mesoderm and endoderm. ((WHY: If you had trouble with this question, review the following material: Body cavities have diverse functions, such as to provide structural support and to facilitate the internal transport of nutrients, gases, and wastes. Many bilaterian animals have a coelom, a body cavity that forms from tissue derived from mesoderm. Other bilaterian animals have a hemocoel, a body cavity lined with tissue derived from mesoderm and with tissue derived from endoderm.))

Which of the following is a characteristic of cnidarians?

* gastrovascular cavity ((WHY: The gastrovascular cavity, characterized by a single opening, is the digestive compartment of cnidarians.))

Some species of rotifers consist solely of females. Their method of reproduction is described as __________.

* parthenogenesis ((WHY: The females lay unfertilized eggs that develop into females.))