Lecture 10 Animals can reproduce asexually Budding Mitosis Genetically the same Regeneration Example sea stars Growing a new organism from a piece of an old one Parthenogenesis An offspring develops from an unfertilized egg Parthenogenesis occurs by developing unfertilized eggs Estrogen progesterone Offspring are clones of the mother no meiosis No males needed all females Which role is played is determined by hormones Higher in estrogen Acting as a female Higher in progesterone Acting as a male Eggs released by physical stimulation courtship Stimulated by another female acting as a male Bite female which causes fertilization as egg Sexual reproduction requires the fusion of sperm and egg Sexual or asexual Asexual Creating a clone Gametogenesis Formation of gametes Spermatogenesis Formation of sperm Oogenesis Formation of eggs Spawning or mating When the gametes are brought together Spawning aquatic organisms releasing gametes into water to be brought together Fertilization Sperm and egg have to fuse together Sexual reproduction is very costly Finding a mate is challenging Maintained between spermatids Needed in order to exchange enzymes and genes necessary to produce final sperm cells Exposure to predators fight over females Taking care of offspring Meiosis is difficult Gametogenesis produces sperm and egg Spermatogenesis occurs in testes Male germ cell diploid Spermatogonium diploid Primary spermatocyte diploid Secondary spermactocyte haploid Spermatids haploid Sperm cells haploid First division 2 sperm cells formed Second meiotic division 4 cells formed Cytoplasmic bridge 4 sperm cells produced overall Specialized Large amounts of mitochondria and enzymes Gametogenesis produces sperm and egg Oogenesis in ovaries Female germ cell diploid Oogonium diploid Ootid haploid second polar body Ovum egg haploid Primary oocyte diploid Secondary oocyte haploid first polar body Secondary oocyte not produced until puberty Frozen as secondary oocyte until fusion fertilization occurs Produces 1 egg and 2 polar bodies Fertilization is the union of sperm and egg example of Sea Urchin Diploid organism Zygote Process Egg emits a chemical attractant Sperm swims towards egg up concentration gradient Sperm has to penetrate two protective layers Sperm and egg plasma membranes fuse together Egg sends out signal that prevents any other sperm from binding Once fused the egg becomes metabolically activated and starts development Then egg and sperm nuclei fuse Specificity Jelly coat First layer sperm must penetrate Vitelline envelope Second layer sperm must penetrate Acrosome Head of the sperm Acrosomal reation Bindin molecules Slow block Receptors on vitelline envelope Enzymes released from head of sperm that start eating away at jelly coat Sodium causes calcium to also rush into the egg Calcium rushing in leads to vesicles fusing with the plasma membrane Fusion leads to a hardened shell being formed around the egg Fast block When sperm and egg fuse a reaction occurs which prevents other sperm from attaching Triggers sodium ions to rush into the egg causing a charge difference Charge difference leads egg to stop producing enzymes that attract sperm Polyspermy An egg being fertilized by more than one sperm Mammalian eggs have an additional layer of protection Cumulus Fusion Sperm eat their way through the cumulus Occurs in the oviduct of humans Signal tells the sperm which way to go once in uterus Zona pellucida Glycoprotein Cortical granules Binds a sperm and triggers the acrosomal reaction Leads to calcium being released inside egg by ER Species specific protein Makes the cumulus go away when released so that sperm cannot bind Released by calcium Fertilization can take place internally or externally Externally Sperm and egg being released into the environment Most aquatic animals Releasing gametes into environment water The release of gametes into the females reproductive tract Water column Internally Penis Vagina Copulation Accessory sex organs The physical joining of two organisms when the sex organs come together Some animals can be either male of female Sex determination Temperature Size Dioecious Largest clown fish is female Second largest clown fish is male Separate sexes Definite males and definite females Monoeicious Both sexes present at the same time in one individual Hermaphrodites Simultaneous Male and female at the same time Sequential Male and one point and female at another point Examples Earth worms clown fish tape worm Type of embryonic development can be grouped in internal fertilizers Direct development Immediately after fertilization organisms looks like mini adult Example toads Oviparous Lay eggs Don t require water amniotic Embryo develops outside of the female Viviparous Humans most mammals Sperm moves from vas deferens to urethra and out the body Embryo is retained within the female Male sex organs deliver and produce semen Contains sperm and other fluids Product of the male reproductive system Sperm makes up 5 of the semen Where testes are contained Sperm produced in testes then go into epididymis Sperm storage where sperm mature Leave epididymis and move to vas deferens Semen Scrotum Epididymis Vas deferens Seminal vesicles Prostate gland 60 of semen volume Produce fructose mucus and fibrinogen 30 of semen volume Adds alkaline fluid since vagina is acidic Enzyme that makes fibrinogen gelatinous Used to make semen sticky Fibrinolisen Bulbourethral gland 5 small volume added Alkali fluid mucus Glands penis Tip of penis Erection Stimulated by nervous system Neurotransmitters release nitric oxide Blood pumped to penis causes it to become erect Hydrostatic skeleton Sperm is produced in the testes Composed of seminiferous tubules Testis Vas deferens Epididymis Sertoli cells Becomes active once in reproductive tract to sperm can be released Feed sperm as they are being produced Leydig cell Produce testosterone Male sexual function is controlled by hormones Involves hypothalamus anterior pituitary Testosterone Secondary sex characteristics Gonadotropin releasing hormone GnRH Travels to anterior pituitary which releases the two following hormones Luteinizing hormone LH Affects leydig cells to produce more testosterone Follicle stimulating hormone FSH Affects sertoli cells to continue feeding for spermatogenesis Female sex organs have any functions Ovary Fimbria Doesn t touch the ovary but is situated around it Start of the fallopian tube Fallopian tubes Lead to uterus Where egg is