Chapter 46 Dr. Gleason - Chapter 46 Animal Reproduction...

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Chapter 46 Animal Reproduction Look over test. Quiz on Tuesday over 5 most missed questions. 2 points each!!! Chapter 43 (Immune System) will be skipped due to time constraints!!! Why reproduce? o Only means available to overcome finite lifespans! Reproductive cycles o Based on hormonal and environmental cues o Cycles of reproductive activity common Examples Ewes (female sheep) ovulate at midpoint of 15 day cycle during fall/early winter; therefore born in springtime Many animals on lunar cycles Advantages of reproductive cycles o Allows conservation of resources o Can reproduce when energy sources readily available o Can maximize survival of offspring Reproductive modes o Asexual Creation of new individuals whose genes come from one adult
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No fusion of eggs and sperm Anthopleura elegantissima (Sea anemnone) splits and offspring is genetically identical to parent. o Sexual Creation of offspring by fusion of male (sperm) and female (egg) haploid gametes to form zygote. Types of Asexual Reproduction o Fission Separation of parent into two or more individuals of equal size Ex: the sea anemone mentioned above, cnidarians and tunicates (sea squirts) o Budding New individual results from outgrowth of existing one. Ex: Hydra o Fragmentation Body breaks into pieces and some or all develop into adults Ex: Sponges, cnidarians, polychaete annelids, tunicates o Parthenogenesis Females produce offspring from unfertilized eggs; no males needed!!! Ex: aphids, rotifers, some bees, wasps, ants, some fish, some amphibians, some lizards. Figure 46.3 Sexual behavior in parthenogenetic lizards o Whiptail lizards: every 2-3 weeks during breeding season, individuals switch sex roles.
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o The sexual behavior is correlated with cycle of ovulation mediated by sex hormones. Advantages of Asexual reproduction
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This note was uploaded on 08/21/2008 for the course BIOL 2108 taught by Professor Leege,gleason during the Spring '08 term at Georgia Southern University .

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Chapter 46 Dr. Gleason - Chapter 46 Animal Reproduction...

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