tailieunhanh - Lecture Biology (7th edition) - Chapter 46: Animal reproduction

After studying this chapter you will be able to: Distinguish between asexual and sexual reproduction; explain how hermaphroditism may be advantageous to animals that have difficulty encountering a member of the opposite sex; describe various ways in which animals may protect developing embryos; using diagrams, identify and state the function of each component of the male and female reproductive systems;. | Chapter 46 Animal Reproduction Overview: Doubling Up for Sexual Reproduction The two earthworms in this picture are mating Each worm produces both sperm and eggs, which will fertilize And in a few weeks, new worms will hatch Figure A population transcends finite life spans Only by reproduction Concept : Both asexual and sexual reproduction occur in the animal kingdom Asexual reproduction is the creation of new individuals Whose genes all come from one parent Sexual reproduction is the creation of offspring By the fusion of male and female gametes to form a zygote The female gamete is the egg The male gamete is the sperm Mechanisms of Asexual Reproduction Many invertebrates reproduce asexually by fission The separation of a parent into two or more individuals of approximately the same size Figure Also common in invertebrates is budding In which two new individuals arise from outgrowths of existing ones Another type of asexual reproduction is fragmentation, which Is the breaking of the body into several pieces, some or all of which develop into complete adults Must be accompanied by regeneration, the regrowth of lost body parts Reproductive Cycles and Patterns Most animals exhibit cycles in reproductive activity Often related to changing seasons Reproductive cycles Are controlled by hormones and environmental cues Animals may reproduce exclusively asexually or sexually Or they may alternate between the two Some animals reproduce by parthenogenesis A process in which an egg develops without being fertilized Among vertebrates, several genera of fishes, amphibians, and lizards, including whiptail lizards Reproduce exclusively by a complex form of parthenogenesis Figure , b Time Ovary size Hormones Behavior Ovulation Ovulation Progesterone Estrogen Female- like Male- like Female- like Male- like (a) Both lizards in this photograph are C. uniparens females. The one on top is playing the role of a male. Every two or three weeks during the breeding . | Chapter 46 Animal Reproduction Overview: Doubling Up for Sexual Reproduction The two earthworms in this picture are mating Each worm produces both sperm and eggs, which will fertilize And in a few weeks, new worms will hatch Figure A population transcends finite life spans Only by reproduction Concept : Both asexual and sexual reproduction occur in the animal kingdom Asexual reproduction is the creation of new individuals Whose genes all come from one parent Sexual reproduction is the creation of offspring By the fusion of male and female gametes to form a zygote The female gamete is the egg The male gamete is the sperm Mechanisms of Asexual Reproduction Many invertebrates reproduce asexually by fission The separation of a parent into two or more individuals of approximately the same size Figure Also common in invertebrates is budding In which two new individuals arise from outgrowths of existing ones Another type of asexual reproduction is fragmentation, which Is the .