sexual reproduction

• factors that cause endangered animals

  • hunting/illegal domestication
  • habitats destroyed(deforestation)
  • diseases wiping out a large number of the species
  • natural disasters
• internal fertilisation


  happens in the body of the animals
• external fertilisation


  out of body, they eject their gametes into water
• reproductive organs


  produces gametes
• male reproductive system includes:


  glands, scrotum, testis, urethra, sperm duct, penis
• testes


  produce sperm cells and testosterone
• urethra 


  carries urine and semen but not at the same time
• glands


  release fluids that have nutrients so the sperm cells have energy
• scrotum


  supports the testes which is outside the body
• foreskin


  protects the penis
• penis


  to place the sperm cells inside the female
• sperm ducts


  where sperms travel through
• the mixture of sperm cells and fluids is called semen which leaves the body through the urethra
• the male gamete 


  sperm
• sperms are specialised cells that are streamlined shaped to swim through body fluids and contains genetic info.They also have lots of mitochondria in a mitochondrion that releases energy.The tail of the sperm is called a flagellum and it helps it swim. The top of the head contains enzymes that attack the outside of the egg cell so it can fertilise it
• the female reproductive system includes


  oviduct, ovary, uterus, cervix, bladder, vagina and urethra
• ovaries


  contain egg cells
• oviduct


  has cilia that sweeps the egg cell towards the uterus
• uterus


  where a baby develops
• cervix


  holds the baby in place during pregnancy
• vagina


  provides a passageway for the uterus lining, egg cell, semen and the baby during childbirth
• as a couple prepares for intercourse

  the man's penis fills with blood and he gets an erection. the woman's vagina becomes moist to reduce friction
• during sex, the penis is inserted into the vagina and the man moves it back and forth. this stimulates it to pump semen into the vagina. this process is called ejaculation. the semen is sucked up through cervix. small movements of the uterus wall carry it to the oviducts
• men eject 300 million sperms but only one burrows into egg and fertilises it
• during fertilisation, the nucleus of the sperm cell and the nucleus of the egg cell fuse
• fertilisation occurs in the oviduct
• in all our cells we have 46 chromosomes, half from ur mom and half from ur dad
• an extra chromosome causes down syndrome
• when the egg cell is fertilised, all the characteristics will be decided and it is unique genetic coding
• a fertilised egg


  zygote
• the zygote splits into two, then each of those cells split again and they keep splitting as the zygote travels towards the uterus
• when the zygote becomes a ball of cells it is called a embryo
• the embryo sinks into the soft lining of the uterus. this process is called implantation. the woman is pregnant
• if implantation doesn't happen you can't get pregnant
• after implantation, the embryo continues to grow and is surrounded by amniotic fluid. the watery substance protects the fetus. the fluid is contained in a bag called the amnion
• a placenta is an organ that is attached to the uterus lining.it takes nutrients, water and oxygen from the mother's blood these go into the baby's blood. waste materials from the baby go into the mother's blood
• the umbilical cord carries the baby's blood to and from the placenta
• if people do drugs or drink when they are pregnant this may harm the baby or kill it
• the mother's blood does not mix with the baby's as the mother's blood pressure is too high and will damage the foetus's blood vessels
• identical twins


  same zygote, genetically identical, share a placenta