Ch 33.4 HW

The phylum Arthropoda includes four major lineages: cheliceriforms (also called chelicerates); myriapods; insects and their relatives (together called hexapods); and crustaceans. Cheliceriforms, Myriapods, Insects, Crustaceans Terms: - Millipedes and centipedes - Butterfly - Wings allow flight - Two pairs of antennae - Arachnids - Primarily Aquatic - Exclusively Terrestrial - Crabs and Isopods - Body divided into head, thorax, and abdomen - possess clawlike feeding appendages - three pairs of walking legs - horseshoe crab

cheliceriforms: horseshoe crabs, arachnids, possess clawlike, and feeding appendages ________________________________________________ myriapods: millipedes and centipedes, exclusively terrestrial ________________________________________________ insects: butterfly, wings allow flight, body divided into head, thorax, and abdomen, and three pairs of walking legs ________________________________________________ crustaceans: two pairs of antennae, crabs and isopods, and primarily aquatic 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.

Comparing nematodes and arthropods Nematodes and arthropods are the largest ecdysozoan phyla. Which of the following statements are true? Select all that apply. - Nematodes possess a closed circulatory system. - Nematodes are acoelomate, whereas arthropods are coelomate. - The cuticle in nematodes lengthens as the animal grows. - Arthropods possess an open circulatory system. - Both nematodes and arthropods have segmented body plans. - Both nematodes and arthropods must molt in order to increase in size. - Arthropods are named for their jointed appendages. - Both nematodes and arthropods possess an external covering, or cuticle. - Some nematodes are parasitic on humans.

- Arthropods possess an open circulatory system. - Both nematodes and arthropods must molt in order to increase in size. - Arthropods are named for their jointed appendages. - Both nematodes and arthropods possess an external covering, or cuticle. - Some nematodes are parasitic on humans. Submit 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.

Select the correct statement(s) describing nematodes. Select all that apply. - Nematodes lack a circulatory system and circular body wall muscles. - All nematodes live in soil. - Some nematodes play important roles in nutrient cycling.

- Nematodes lack a circulatory system and circular body wall muscles. - Some nematodes play important roles in nutrient cycling.

Which phylum is characterized by animals that have a segmented body? - Porifera - Cnidaria - Platyhelminthes - Mollusca - Arthropoda

Arthropoda

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.

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.