Biology 102Lecture 23Outline of Last Lecture:I. CnidariansII. TapewormsOutline of Current Lecture:I. Clicker QuestionsII. TapewormsIII. RoundwormsIV. InsectsClicker QuestionsTapeworms and planarians BOTH belong to the same group. The Flatworms. Why then are they so different?a. Planarians are free livingb. Tapeworms are parasitesc. They have evolved special structures suited for their particular way of lifed. All of the aboveWhat is the evolutionary advantage of a parasitic worm having a complex life cycle (two or morehosts, and at least one larval stage)?a. Avoiding mortality when host #1gets eaten by a predatorb. Predators are usually larger than prey and when parasite moves up the food chain, it hasmore room (bigger niche) in the predator to grow largerc. Larger size at maturityd. Higher transmission rates e. Higher rate of fecundityf. Reduction in the chance of extinction if host goes extinctg. All of the aboveTapewormsTapeworm: parasitic flatworm - Penis fencing: when flatworms fence 2 “males” use their penises to fence one another. The winner or the flatworm that stabs the other with his penis gets to remain male whilethe other becomes female.RoundwormsBiology 102Roundworms can be free living and or parasitic as well- Trininella larvae: in the muscle of porko It goes into metamorphosis and forms into an adult roundwormGuinea worm: 3.5 million cases in 1986, 1,800 in 2012- Drink infected water with water flea and that water flea has the guinea worm larvaeInsects70% of animal species are insects- Success of animalso Exoskeleton: not living, this is a problem because in order for them to grow they have to molt leaving the insect really vulnerable and unable to moveo Waterproof cuticle: allows them to live in hot environments80% of insects undergo metamorphosis- Complete metamorphosis: larval stage that does not resemble the adulto Caterpillar represents larval stage Is specialized for eating and growing Enclosed as a nonfeeding pupa Have embryonic stem cells on reserve Metamorphosis occurs Emerge as the adult Adult form: usually lives in a different place specializes in dispersal and
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