Reproductive System

• Sexual reproduction - the creation of an offspring by fusion of a male gamete and female gamete to form a zygote
• sperm - male gamete
• egg - female gamete
• Asexual reproduction - creation of offspring without the fusion of egg and sperm
• Mechanisms of Asexual Reproduction: budding, fission, fragmentation, and parthenogenesis
• Budding - a simple form of asexual reproduction found only among invertebrates
• Fission - asexual reproduction in many invertebrates; separation of a parent into two or more individuals of about the same size
• Fragmentation - breaking of the body into pieces, some or all of which develop into adults
• Fragmentation must be accompanied by regeneration
• regeneration - regrowth of lost body parts
• Parthenogenesis - the development of a new individual from an unfertilized egg
• Parthenogenesis - mechanism of asexual reproduction that is mainly observed in invertebrates, but is observed rarely in some vertebrates
• Sexual females have half as many daughters a s asexual females
• almost all eukaryotic species reproduce sexually
• Asexual reproduction - expected to be most advantageous in stable, favorable environments
• sexual reproduction - may enhance reproductive success of parents when environmental factors change relatively rapidly
• Reproductive Cycles - controlled by hormones and environmental cues
• climate change can decrease reproductive success
• Hermaphroditism - each individual has male and female reproductive systems
• oysters - example of species that exhibit male to female reversal
• coral reef fish - example of species that exhibit female to male

  reversal
• Fertilization - the union of egg and sperm
• External fertilization - eggs shed by the female are fertilized by sperm in the external environment
• In external fertilization, a moist habitat is required to allow sperm to swim to the egg and to prevent the gametes from drying out
• spawning - individuals cluster in the same area to release their gametes into the water at the same time
• Internal fertilization - sperm are deposited in or near the female reproductive tract, and fertilization occurs within the tract
• Internal fertilization - requires behavioral interactions and compatible copulatory organs
• Gonads - organs that produce gametes
• Many female insects have a spermatheca in which sperm is stored during copulation
• cloaca - a common opening between the external environment and the digestive, excretory, and reproductive systems
• mammals usually have a separate opening to the digestive tract
• External reproductive organs of males: the scrotum and penis
• [Internal organs of Male Reproductive]

  gonads - which produce sperm and hormones
• [Internal organs of Male Reproductive]

  accessory glands - secrete products needed for sperm movement
• [Internal organs of Male Reproductive]

  Ducts - carry sperm and glandular secretions
• testes - male gonads
• seminiferous tubules - where sperm forms
• Leydig cells surrounding the tubules produce hormones
• testes is held outside the abdominal cavity in the scrotum where temperature is lower
• From the seminiferous tubules, sperm pass into the coiled duct of the epididymis