BSC1010- Intro to Biology I K. Maltz Chapter 51

Reproduction Two types Sexual Reproduction- 2 gametes (not necessarily 2 parents) Asexual reproduction- Single parent; no fusion of genetic material In asexual reproduction, the offspring are clones of the parent Sexual reproduction allows for genetic mixing and greater gene variation Asexual reproduction has some advantages, too. Can reproduce in isolation Can reproduce rapidly And they can produce a large number of offspring prevalent in species in stable environments

Asexual Reproduction Mostly in invertebrates Three types Budding- parent produces outgrowth that becomes offspring organism Regeneration- whole new organism from fragment of parent Parthenogenesis- offspring from unfertilized egg Budding is usually in cnidarians such as hydras Regeneration is usually in worms (flat worms) and echinoderms (sea stars) Parthenogenesis can occur in some fish and reptiles

Examples Budding- Cnidarians Regeneration- Enchinoderms Parthenogenesis- Daphnia Sessile- non-motile Daphnea = water flea

Parthenogenesis vs. Normal Fertilization In sexual reproduction 2 gametes come together to combine dna producing a zygote which develops into an embryo

Hermaphroditism Synchronus hermaphroditism- can fertilize own eggs or join with another to reproduce (ex earthworms) Sequential hermaphroditism- sex reversal (expression of specific genes, but not at the same time) (ex fish)

Gametogenesis 2o spermatocyte 1o spermatocyte 2o oocyte oogonium Sperm- acrosome with nucleus inside, midpiece with mitochondrion, flagellum tail 1o oocyte egg First polar body

Gametogenesis antrum

Cells Cell phases Seminiferous tubule Leydig with testosterone

Fertilization Eggs continually release a chemoattractant molecule When a sperm gets close the sperm cell’s metabolism increases and it swims faster, following the concentration gradient When the sperm reaches the egg, the cumulus mass around the egg breaks down the sperm acrosome This in turn releases enzymes from the acrosome that break down the zona pellucida The plasma membrane of the egg fuses with the sperm head A metabolic change occurs within the egg to prevent more sperm from fertilizing

Now What? The resulting fertilized egg can develop in several ways Oviparity- animal develops in shell (birds) Viviparity- animal develops inside the mother (humans) Ovoviviparity- eggs have very thin covering develop inside mother but gain no nutrients from mother (some sharks, lizards, snakes)

Male Reproductive Structure Go from testes into epididymis to vas deferens to ejaculatory duct. ED connects with urethra Seminal vesicles secrete fructose and motile factors All of this requires testosterone Hypothalamus releases gonadotropin releasing hormone to signal anterior pituitary to release Leutinizing hormone and follicle stimulating hormone They activate the testes LH works on Leydig and FSH works on sertoli Leydig secrete testosterone, which also stimulates sertoli to start spermatogenesis Testosterone also stimulates secondary sex characteristics in puberty Prostate and bulbourethral secretes an alkaline fluid that protects sprem from acidic fluid in urethra and femal tract Sexual arousal causes release of Nitrous oxide in penis causing vasodilation

Female Reproductive Structure

Follicle and Oocyte Development

Menstrual Cycle

Placental Structure Embryo 1st 8 weeks, after 8 weeks called fetus

Hormonal Control Partuition- birth Oxytocin- posterior pituitary hormone that stimulates contraction of uterine muscles In the 3rd trimester the placenta secretes a lot of estrogen (particularly estradiol), which enhances sensitivity to oxytocin The fetus’s head pushes on the cervix, which signals the hypothalamus to release oxytocin Prostaglandins from the uterus and positive feedback continue the contractions

Labor

Birth Control Methods Male sterilization called vasectomy cuts vas deferens Tubal ligation in females tie and cut fallopian tubes. Keep on mind these are all when used PROPERLY, birth control pill is especially hard to use perfectly