2 Two 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
3 4 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
4 What type of reproduction? What type of reproduction? Figure 46.2 Asexual reproduction of a sea anemone (Anthopleura elegantissima)
5 4 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
6 4 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
8 Asexual reproduction Sexual reproduction Female Female Male Generation 1FemaleGeneration 2MaleGeneration 3Generation 4
9 Patterns 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.
10 Patterns 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
11 Patterns 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
12 Fertilization 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
15 Female 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
16 Puberty 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
20 Spermatogenesis differs from oogenesis in which ways?
21 Differences 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
22 Female 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