2Two Ways to do it… Asexual Reproduction Sexual Reproduction Creation of offspring without the fusion of egg and spermSexual Reproductioncreation of an offspring by fusion of a male gamete (sperm) and female gamete (egg) to form a zygote
34 Types of Asexual Reproduction 1. Fissionseparation of a parent into 2 or more individuals of about the same sizeCommon in invertebrates2. Buddingnew individuals arise from outgrowths of existing ones
4What type of reproduction? What type of reproduction? Figure 46.2 Asexual reproduction of a sea anemone (Anthopleura elegantissima)
54 Types of Asexual Reproduction (page 2) 3. Fragmentationbreaking of the body into pieces, some or all of which develop into adultsFragmentation must be accompanied by regeneration, regrowth of lost body parts
64 Types of Asexual Reproduction (page 3) 4. ParthenogenesisIt gets weird here, so stay with methe development of a new individual from an unfertilized eggThere is a female (egg producer) & there is a male, but no fertilized eggThe egg doubles its chromosomes during parthenogenesis = diploid (viable) organism
7Why sex? Seriously? Humans & dolphins know why Genetic recombination Accelerate adaptation to environmental forcesShed harmful genes more rapidly
8Asexual reproduction Sexual reproduction Female Female Male Generation 1FemaleGeneration 2MaleGeneration 3Generation 4
9Patterns of Reproduction 1. OvulationRelease of mature eggsTypically cyclical in natureInfluenced or determined by hormonal cyclesAssociated with the release of chemicals (pheromones) indicating sexual receptivity (estrous cycle)Also influenced by environmental cues, e.g. day length, changing of seasons, etc.
10Patterns of Reproduction (page 2) 2. Hermaphroditismeach individual has male and female reproductive systemsIndividuals can self-fertilize or mateSome individuals are capable or switching genders depending on environmental conditionsEffective reproductive strategy for solitary animals
11Patterns of Reproduction (page 3) Who’s your daddy?3. Sex ReversalIndividuals can change gender during its lifetimeBluehead wrasseReef fishIf male dies, largest female becomes a maleShe (He) produces sperm now
12Fertilization Fertilization - union of sperm & egg 2 Types of FertilizationExternal FertilizationEggs shed by the female are fertilized by sperm in the external environmentLarge number of gamete productionInternal FertilizationSperm are deposited in or near the female reproductive tract, and fertilization occurs within the tractAdaptation to dry environments
15Female Reproductive Physiology Female gonads (ovaries) lie inside the abdominal body cavityEach ovary contains many follicles, which consist of a partially developed egg, called an oocyte, surrounded by support cellsPrior to birth each oocyte is arrested in Prophase I (meiosis I)Called primary oocyte
16Puberty The primary oocyte stays in prophase I until puberty Beginning at puberty, 1 oocyte per cycle completes meiosis I & arrests at metaphase IICalled secondary oocyte after metaphase IIDue to FSH secretion, a follicle grows and an egg or oocyte continues its developmentFinally, following fertilization oocyte completes meiosis II
20Spermatogenesis differs from oogenesis in which ways?
21Differences Spermatogenesis Oogenesis Production 4 spermatids 1 egg DurationContinuous from puberty to deathDiscontinuousBegins before birthStopsStarts up after pubertyMenopauseMeiosisContinuous process, and completes at regular intervals1. Eggs are arrested in Prophase I, prior to birth2. Prophase I Metaphase II,3. Finish after fertilization
22Female Cycles Primates have menstruation cycles Endometrial lining is shed from the uterus through the cervix & vagina3 Phases of Menstrual Cycle1. Menstrual Flow PhaseMost of the endometrium is shed, menstrual bleeding occurs2. Proliferative PhaseEndometrium begins to regenerate & thicken3. Secretory PhaseEndometrium continues to thicken and if no embryo is implanted, proceeds to menstrual flow phase