31. Invertebrates

Ecdysozoans

Characteristics of Crustaceans

SCIENTIFIC THINKING In one of the experiments described in researchers tested the hypothesis that the highly successful arthropod body plan resulted from new genes that originated in the arthropod lineage. Draw a diagram showing the evolutionary relationship between arthropods and velvet worms and use it to explain why velvet worms were a good choice to test this hypothesis. What results would have supported the hypothesis?

3840_Chapter 21: Arthropoda- Hexapoda

Propose an explanation for why annelids and arthropods were thought to be closely related, before phylogenetic analyses in the late 1990s.

have closed circulatory systems; have bristles

No. Arthropods have an open circulatory system.

are cephalized and bilaterally symmetrical; have true organs

No. Both are coelomates, and both are segmented.

have prominently segmented bodies; have jointed appendages

What is the meaning of the name arthropod?

The arthropods superficially resemble earthworms in that both groups __________, yet the two are distinctly different because arthropods, but not earthworms, __________.

One of the key characteristics of arthropods is their jointed appendages. Describe four functions of these appendages in four different arthropods.

Arthropoda (Part 1) Chelicerata, Crustacea, Insecta, Myriapoda- Invertebrate Paleontology | GEO GIRL

Suppose that a gene originally identified in nematodes (roundworms) is found to be homologous with a gene that can cause developmental abnormalities in humans. Would it be possible to use fruit flies as a model organism to study this gene? Explain.

One trait that is shared by the Lophotrochozoa and Ecdysozoa is                .

Nematodes

No. Flame bulbs are excretory structures found in flatworms.

No. Arthropods exhibit bilateral symmetry.

No. Arthropods have a true coelom, although it is typically reduced in size.

No. Only one of the other choices is correct.

Arthropods belong to the clade Ecdysozoa.

A major characteristic of arthropods is __________.

Use your understanding of insect evolution to predict two adaptations for terrestrial living that occurred in spiders.

ARTHOPODA CLASSIFICATION

A team of 102 scientists spent a year surveying a small area of the San Lorenzo rain forest in Panama to count the number of species of arthropods living there. After collecting 129,494 specimens—using nets, traps, shovels, tree-climbing harnesses, helium balloons, and other creative gear—it took the team eight years to sort and identify the arthropods.

Which of the following nested groups best describes the taxonomic context for the San Lorenzo project?
a. Animalia > Bilateria > Arthropoda > Ecdysozoa
b. Protostomia > Lophotrochozoa > Ecdysozoa7 Arthropoda
c. Arthropoda > Protostomia > Ecdysozoa > Bilateria
d. Bilateria > Protostomia > Ecdysozoa > Arthropoda

arthropod appendages generally increase in number as the animal ages

No. The appendages increase in size, not number.

the environment degrades the exoskeleton, which therefore must be shed and replaced

No. The chitinous exoskeleton is very durable.

worn exoskeletons make arthropods more susceptible to predators

the exoskeleton is progressively reabsorbed by body tissue

No. Arthropods outgrow their exoskeletons.

Why do we need to acquire new clothes for children?

In arthropods, molting is necessary because __________.

Parasitic Diseases Lectures #21: Nematodes

Short Video: Butterfly Emerging

involves adults that are specialized for eating and growth

No. Complete metamorphosis involves larvae adapted for eating and growth and adults adapted for dispersal and reproduction.

No. Complete metamorphosis is not synonymous with molting.

is accompanied by a complete rearrangement of the genome

No. The genome is not rearranged, although in some groups, chromosomes are lost at metamorphosis.

features a larval stage that looks different from the adult

Butterflies exhibit complete metamorphosis.

Complete metamorphosis __________.

Phylum Nematoda: the roundworms

No. Annelids have a closed circulatory system.

This phylum is the most abundant on Earth, consisting of two out of every three known species of life on Earth.

An unidentified species of animal displays the following characteristics: bilateral symmetry, a complete digestive system, an open circulatory system, distinct body segmentation, and a series of molting stages during growth. To which of the following animal phyla does this species most likely belong?

Which protostome phyla successfully made the transition from water to land? Select True or False for each phylum.
T/F Mollusca
T/F Arthropoda
T/F Annelida
T/F Nematoda

Crustaceans and Hexapods

Which phylum is characterized by animals that have a segmented body?
a. Cnidaria
b. Platyhelminthes
c. Arthropoda
d. Mollusca

No. These are the excretory organs of flatworms.

No. These carry out gas exchange in most spiders.

No. The exoskeleton does not allow for gas exchange.

These structures function somewhat like the air-duct system in a building.

In most insects, gas exchange is accomplished by __________.

Pose a hypothesis to explain why the evolution of the wing was such an important event in the evolution of insects.

Unit 14 - Annelids, Mollusks, and Arthropods

No. Although nematodes are abundant, they are far outnumbered by insects.

No. In species diversity, insects (which are almost entirely terrestrial) outnumber all other forms of life combined.

No. Insects, which have a coelom, have the greatest number of species.

No. Only about 5% of known animal species are vertebrates.

The majority of animal species are arthropods.

The majority of animal species are __________.

No. An exoskeleton is a characteristic shared by all arthropods.

No. This is a characteristic of all arthropods.

No. Both insects and crustaceans have antennae.

How do the appendages of insects compare to the appendages of crustaceans?

Sowbugs are really crustaceans, not insects. Therefore, a sowbug does not have __________.

Identifying Hexapods and Basal Insects

Nematoda General Characters

Meet the Most Important Animal You’ve Never Seen

3840_Chapter 20: Arthropoda- Crustacea

No. Grasshoppers are in the clade Hexapoda, whereas spiders are in the clade Chelicerata.

No. Pill bugs are isopods in the clade Pancrustacea, whereas spiders are in the clade Chelicerata.

No. Mosquitoes are in the clade Hexapoda, whereas spiders are in the clade Chelicerata.

No. Centipedes are in the clade Myriapoda, whereas spiders are in the clade Chelicerata.

Which of the following groups has chelicerae?

Which of the following animals is most closely related to spiders?

Molecular comparisons place nematodes and arthropods in clade Ecdysozoa. What characteristic do they share that is the basis for the name Ecdysozoa?
a. a complete digestive tract
b. body segmentation
c. molting of an exoskeleton
d. bilateral symmetry

Arthropod Characteristics

Arthropods and Chelicerata

What is the function of the arthropod exoskeleton?
a. The presence of an exoskeleton has given arthropods a good fossil record, because hard parts fossilize more readily than do soft tissues.
b. It has no well-established function. (Trilobites had an exoskeleton, and they went extinct.)
c. It provides protection and functions in locomotion.
d. It makes growth by molting possible.

Which of the following groupings includes the largest number of species? (Explain your answer.)
a. invertebrates
b. arthropods
c. insects
d. vertebrates

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