BI0 101 1nd Edition Lecture 9 Outline of Last Lecture I Characteristics of Animals II How are animals Grouped III Investigating patterns IV Trends In Circulatory Systems V Trends in Skeletal Systems Outline of Current Lecture II Asexual Reproduction III Sexual Reproduction IV Fission V Budding VI Parthenogenesis VII Hermaphroditism Current Lecture Biological Purpose of life is to reproduce The diverse reproductive mechanisms in the animal kingdom Asexual Reproduction New individuals whose genes all come from one parent without the fusion of egg and sperm Sexual Reproduction the creation of offspring by the fusion of haploid gametes to form a zygote fertilized egg o Diploid o Ovum Female Gamete usually large and nonmotile o Spermatozoon Male gamete usually small and motile Sexual reproduction may enhance the reproductive success These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute Mechanisms of Asexual Reproduction Fission The separation of a parent into two or more individuals of approximately equal size o Fission is essentially cloning themselves Budding New individuals arise from outgrowths of existing ones o Certain tunicates and cnidarians o The offspring may either detach or remain joined Fragmentation and regeneration o The breaking of the body into several pieces some or all of which develop into complete adults Advantages of Asexual Reproduction Enables animals living in isolation Create numerous offspring in a short amount of time Would be the most advantageous in stable favorable environments Some animals alternate the reproduction between asexual and sexual modes Parthenogenesis the process by which an unfertilized egg develops into adult Parthenogenesis plays a role in the social organization of species of bees and ants o Male honey bees are haploid and female honey bees are diploid 2n diploid or 2 sets of DNA Haploid is one set of DNA Several genera of fishes amphibians and lizards produce by a complex form of parthenogenesis that produces diploid zygotes The complex form of parthenogenesis Some vertebrates use parthenogenesis to produces diploid zygotes o By doubling of chromosomes after meiosis Eg About 15 species of whiptail lizards reproduce exclusively by parthenogenesis THERE ARE NO MALES IN THESE SPECIES Hermaphroditism Each individual has both male and female reproductive systems o Sessile organism can t move Although some hermaphrodites fertilize themselves most mate with a member of the same species Advantages o More adaptable to the environments o Each hermaphroditic mating can result in twice as many offspring as from a male female mating Sequential Hermaphroditism An individual reverses its sex during its lifetime The mechanisms of fertilization The union of sperm and egg External Fertilization o Eggs are released by the female into a wet environment where they are fertilized by the male Internal fertilization o Sperm are deposited in the female reproductive tract and fertilization occurs within the tract External Fertilization A moist habitat o Prevents gametes from dying out o Allow the sperm to swim to the eggs Timing and environmental Cues o Ensure that mature sperm encounter ripe eggs Specific mating behaviors Temperature or day length Produce enormous numbers of zygotes o Ensuring the survival of offspring External Fertilization An adaptation to terrestrial life that enables sperm to reach an egg when the environment is dry Advantages o Produces fewer zygotes o Energy saving o Greater protection of the embryos Complex reproductive systems have evolved in many animal phyla Animals must have systems that produce gametes gonads The simplest systems o The egg and sperm develop from undifferentiated cells lining the body wall The most complex reproductive systems o Contain many sets of accessory tubes and glands that nourish and protect the gametes and the developing embryos Vertebrate reproductive systems Differences between vertebrates reproductive system o The cloaca Existed in many non mammalian vertebrates The digestive excretory and reproductive systems have a common opening to the outside Probably present in the ancestors of all vertebrates o Mammals have separate openings for the digestive excretory and reproductive systems Vertebrate reproductive systems Differences between vertebrate reproductive systems o The uterus Existed in most vertebrates Most vertebrates is divided into two chambers o The copulatory organs in male Many non mammalian vertebrates do not have a well developed penis and simply turn the cloaca inside out to ejaculate Human Reproductive organs female A woman is born with about 400 000 Follicles Only several hundred of which will release eggs during a female s reproductive years Reproductive anatomy of the human male Testis consist of seminiferous tubules Epididymis Places for sperm storage and maturation 6m tube length Bulbourethral gland Secrete mucus that neutralizes an acidic urine in the urethra Gametogenesis Based on meiosis but details differ in females and males o Oogenesis The development of mature ova egg cells o Spermatogenesis The production of mature sperm cells Each ejaculation of a human male contains 100 to 650 million sperm cells