Presentation on theme: "Animal Reproduction Chapter 46. Slide 2 of 26 Two Ways to do it… Asexual Reproduction Creation of offspring without the fusion of egg and sperm "— Presentation transcript:
Animal Reproduction Chapter 46
Slide 2 of 26 Two Ways to do it… Asexual Reproduction Creation of offspring without the fusion of egg and sperm Sexual Reproduction creation of an offspring by fusion of a male gamete (sperm) and female gamete (egg) to form a zygote
Slide 3 of 26 4 Types of Asexual Reproduction 1. Fission separation of a parent into 2 or more individuals of about the same size Common in invertebrates 2. Budding new individuals arise from outgrowths of existing ones
Slide 4 of 26 What type of reproduction?
Slide 5 of 26 4 Types of Asexual Reproduction (page 2) 3. Fragmentation breaking of the body into pieces, some or all of which develop into adults Fragmentation must be accompanied by regeneration, regrowth of lost body parts
Slide 6 of 26 4 Types of Asexual Reproduction (page 3) 4. Parthenogenesis It gets weird here, so stay with me the development of a new individual from an unfertilized egg There is a female (egg producer) & there is a male, but no fertilized egg The egg doubles its chromosomes during parthenogenesis = diploid (viable) organism
Slide 8 of 26 Asexual reproduction Female Sexual reproduction Female Generation 1 Male Generation 2 Generation 3 Generation 4
Slide 9 of 26 Patterns of Reproduction 1. Ovulation Release of mature eggs Typically cyclical in nature Influenced or determined by hormonal cycles Associated with the release of chemicals (pheromones) indicating sexual receptivity (estrous cycle) Also influenced by environmental cues, e.g. day length, changing of seasons, etc.
Slide 10 of 26 Patterns of Reproduction (page 2) 2. Hermaphroditism each individual has male and female reproductive systems Individuals can self-fertilize or mate Some individuals are capable or switching genders depending on environmental conditions Effective reproductive strategy for solitary animals
Slide 11 of 26 Patterns of Reproduction (page 3) 3. Sex Reversal Individuals can change gender during its lifetime Bluehead wrasse Reef fish If male dies, largest female becomes a male She (He) produces sperm now Who’s your daddy?
Slide 12 of 26 Fertilization Fertilization - union of sperm & egg 2 Types of Fertilization External Fertilization Eggs shed by the female are fertilized by sperm in the external environment Large number of gamete production Internal Fertilization Sperm are deposited in or near the female reproductive tract, and fertilization occurs within the tract Adaptation to dry environments
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Slide 15 of 26 Female Reproductive Physiology Female gonads (ovaries) lie inside the abdominal body cavity Each ovary contains many follicles, which consist of a partially developed egg, called an oocyte, surrounded by support cells Prior to birth each oocyte is arrested in Prophase I (meiosis I) Called primary oocyte
Slide 16 of 26 Puberty The primary oocyte stays in prophase I until puberty Beginning at puberty, 1 oocyte per cycle completes meiosis I & arrests at metaphase II Called secondary oocyte after metaphase II Due to FSH secretion, a follicle grows and an egg or oocyte continues its development Finally, following fertilization oocyte completes meiosis II
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Slide 20 of 26 Spermatogenesis differs from oogenesis in which ways?
Slide 21 of 26 Differences SpermatogenesisOogenesis Production4 spermatids1 egg Duration Continuous from puberty to death Discontinuous Begins before birth Stops Starts up after puberty Menopause Meiosis Continuous process, and completes at regular intervals 1. Eggs are arrested in Prophase I, prior to birth 2. Prophase I Metaphase II, 3. Finish after fertilization
Slide 22 of 26 Female Cycles Primates have menstruation cycles Endometrial lining is shed from the uterus through the cervix & vagina 3 Phases of Menstrual Cycle 1. Menstrual Flow Phase Most of the endometrium is shed, menstrual bleeding occurs 2. Proliferative Phase Endometrium begins to regenerate & thicken 3. Secretory Phase Endometrium continues to thicken and if no embryo is implanted, proceeds to menstrual flow phase
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Slide 24 of 26 Ovarian Cycle Controlled by hormones Parallels the menstrual cycle Note the important role of hormones throughout the cycle Note the parallels between the ovarian & menstrual cycle as well
Slide 25 of 26 GnRH – Gonadotropic releasing hormone Note: FSH stays relatively constant LH shoots up = ovulation
Slide 26 of 26 Estradiol – secreted by ovarian follicle -- Causes endometrial lining to thicken Progesterone – follicle rupturing causes spike in this hormone -- When it falls, so too the endometrial thickening