REPRODUCTION

Objectives Compare asexual and sexual reproduction and discuss advantages and disadvantages of each Describe the different mechanisms of asexual reproduction (e.g. fission, budding, gemmules, fragmentation) Relate the choice of reproductive strategy with the availability of mates and resources, environment, and the lifestyle of the organism Compare internal and external fertilization and discuss advantages and disadvantages of each Enumerate the parts and describe the functions of the male and female reproductive systems Describe the events that occur during human sexual response Describe the structure of the sperm cell and that of the egg cell Describe the events that occur during fertilization

Asexual Reproduction genes come solely from parent mitotic cell division most suitable for favorable and stable environments fission (bacteria, archaea) gemmule formation (sponges) budding (yeast, hydra) regeneration and fragmentation (planarians, echinoderms) parthenogenesis (some insects, reptiles, fish)*

All-female whiptail lizard species Cnemidophorus mexicanus

Sexual Reproduction fusion of haploid gametes to form a diploid zygote formation of haploid gametes involves meiosis fertilization restores diploid number used during times of great stress increases genetic variety through gene shuffling

External and Internal Fertilization external - egg is fertilized in the environment more zygotes are produced often triggered by chemical/behavioral factors (e.g. pheromones)‏ internal - egg is fertilized in the female reproductive tract less zygotes parental care increases chances for survival

Different Reproductive Strategies Reproductive cycles (mammals) periodic, controlled by hormones Alternatingly asexual/sexual (aphids, rotifers) depends on environmental conditions Hermaphroditism (tapeworms) each individual has both male and female reproductive organs Sequential hermaphroditism (wrasses) conversion between sexes (protogynous, protandrous) Parthenogenesis (some insects, reptiles, fish)

Mammalian reproductive systems (male) External scrotum penis Internal gonads - produce gametes and hormones accessory glands - secrete products essential to sperm movement ducts - carry sperm and glandular secretions

4) Produce a fructose-rich fluid that aids in sperm motility 5) Produce an alkaline-rich fluid that prolongs sperm lifespans 7) Common passageway of sperm and urine 6) Produce a clear mucus that neutralizes acidic urine 2) Tightly-coiled tubes that make sperm motile and potent 3) Muscular tube that transports sperm from testes to urethra 1) Seminiferous tubules (sperm) and Leydig cells (testosterone)

Mammalian reproductive systems (female) External clitoris two sets of labia Bartholin’s glands Internal pair of gonads system of ducts and chambers

Human Sexual Response Phases of HSR Vasocongestion Two physiological reactions Vasocongestion Filling of a tissue with blood erection Flushing, swelling of nipples Myotonia Increased muscle tension in smooth and skeletal muscles Sustained/rhythmic contractions Phases of HSR Excitement – prepares vagina/penis for intercourse Plateau – breathing and heart rate increase Orgasm – rhythmic, involuntary contractions Resolution – reverses response of previous phases

Human Sexual Response

Structure of the sperm cell Head Acrosome helps penetrate the egg cell with its enzymes Nucleus Centriole Middle piece/body contains large amounts of mitochondria that provide ATP for movement of the tail Tail

Structure of the egg cell Corona radiata covering that supplies vital proteins to the cell Zona pellucida binds spermatozoa required to initiate the acrosome reaction used for protection very essential for the oocyte’s death and fertilization Nucleolus non-membrane bound structure made of protein and nucleic acid and transcribes RNA

Fertilization Capacitation Separation of follicle cells Sperm-zona pellucida binding Acrosomal reaction Sperm-oocyte binding Egg activation and the cortical reaction Fast block to polyspermy Slow block to polyspermy