Wiens-lecture 9-14April_v2

Wiens-lecture 9-14April_v2 - Todays Lecture Phylogeny and...

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Today’s Lecture • Phylogeny and diversity of ecdysozoans
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Test next Wednesday • Same format and rules as previous exams • Read the book and go over the lectures, but test will be primarily on the lectures
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Studying advice • Big studying night should be the night before the night before the exam, but start before then also (e.g., Sunday) • Don’t stay up all night the night before the exam • Write down and then rewrite all the material in the lectures 5-6 times; don’t expect to memorize the material just by reading it • Make flashcards to learn vocabulary; start this week, not next week • Study alone, in a quiet place with no music or TV (try the library)
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Phylogeny of animals last Friday Monday Today Friday April 19–28
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Phylogeny of Protostomes
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Lophotrochozans vs. ecdysozoans Ecdysozoans share an exoskeleton (external skeleton) • Secreted by epidermis, made of layers of protein and (in some groups) a strong waterproof polysaccharid called chitin • Provides protection and support • But has an important problem
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Lophotrochozans vs. ecdysozoans Ecdysozoans share an exoskeleton (external skeleton) • Exoskeleton cannot grow • To increase in size, individuals need to “molt” (shed) the exoskeleton, process called ecdysis • New exoskeleton grows underneath the old one, expands and hardens after ecdysis
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Lophotrochozans vs. ecdysozoans Ecdysozoans share an exoskeleton (external skeleton) • In worm-like ecdysozoans, exoskeleton may be thin, flexible • Called cuticle • A thin cuticle allows water, oxygen, and minerals to pass into the body, but restricts species to moist environments
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Lophotrochozans vs. ecdysozoans Ecdysozoans share an exoskeleton (external skeleton) • Species with waterproof exoskeleton able to invade land and dry areas • But hard to move (not flexible); body needs appendages • Cannot breathe through skin; requires gas exchange system
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3 obscure groups of marine ecdysozoans • Priapulids • Kinorhynchs • Loriciferans
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ecdysozoans Priapulids • 16 species, marine, 0.5 mm to 20 cm
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Wiens-lecture 9-14April_v2 - Todays Lecture Phylogeny and...

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