REPRODUCTION AP BOOK: CHAPTER 46 LOREN MCLENDON

Animal Reproduction (46.1) Reproduction: the creation of new individuals from old ones –A population only transcends finite life spans by reproduction –Study diverse reproductive mechanisms Closer look at humans –Physiology of parents

Asexual Reproduction Asexual: “Greek, without sex” –Genes come form one parent –Mitotic cell division Types of Asexual Reproduction –Fission (invertebrates): separation of a parent into two or more individuals of about equal size –Budding: New individuals arise from outgrowths of exiting ones Form colonies (corals, cnidarians, sponges) –Fragmentation: Breaking of body into several pieces that develop into complete adults Must be accompanied by regeneration Replaces lost appendages (not reproduction)

Sexual Reproduction Sexual: Creation of offspring by the fusion of haploid gametes to form a zygote – Requires animal to undergo meiosis Female Gamete: egg (ovum) –Large cell, not motile Male Gamete: sperm –Smaller, motile cell (ability to move) –Increases genetic variability Enhances success in rapidly changing environments

Reproductive Cycles and Patterns Animals have reproductive cycles –Reproduce when there more energy is available –Controlled by hormone and environmental cues –Some animals can reproduce asexually/sexually Depends on their environment Parthenogenesis:egg develops without being fertilized –Reproduce exclusively by doubling chromosomes after meiosis »Creates diploid zygotes Hermaphroditism: Species that seldom encounter another of the same species –Individuals have both male and female parts »Both donate and receive sperm Sequential Hermaphroditism: individual reverses its sex during its life time

Mechanisms that help Sperm meet Egg Fertilization: union of sperm and egg –External:egg released into wet environment to be fertilized by male Always require moist environment –Gametes won’t dry out, sperm can travel to egg Timing is crucial –Environmental cues: temp., day length, chemical signals –Internal: sperm deposited near or in female reproductive tract Adaptation in terrestrial animals (sperm can reach egg in a dry environment) Requires cooperative behavior, leads to copoluation Natural selection: eliminates undesirable habits (spiders) Pheromones: chemical signals released by one organism that influence the physiology and/or behavior of others –Small, volatile/water soluble, Active in minute amounts –Mate attractants

Production and Delivery How are gametes produce? –Gonads: organs that help most animals produce gametes As gametes mature they are released from the body wall and fill the coelom Some shed through the excretory openings Others, swelling mass of eggs split the body open killing the parent. –Spermatheca: a place in the female body where sperm can be stored for a year or more –Some non-mammalian vertebrates have a cloaca Common opening for reproductive, digestive, and excretory systems