23.Animal reproduction done.docx

Reproduction in Animals Two types: asexual reproduction and sexual reproduction Asexual reproduction Involves only one parent, and its offspring is genetically identical to parent and is common in plants and aphid’s Sexual reproduction Occurs when the male sperm produced by the testes enters the fem...

Reproduction in Animals Two types: asexual reproduction and sexual reproduction Asexual reproduction Involves only one parent, and its offspring is genetically identical to parent and is common in plants and aphid’s Sexual reproduction Occurs when the male sperm produced by the testes enters the female’s vagina to fuse the egg produced by her ovaries. Offspring are not genetically identical - will contain a mixture of genes. Male reproductive system Function: Testes Produces sperm (haploid) by meiosis and Secrete testosterone. Epididymis is Maturing & storage of sperm cells. Sperm Male gamete Sperm duct Forces sperm by peristalsis to the urethra during ejaculation Testes produce sperm (exocrine function) and production of testosterone (endocrine function). The testes temperature is 35°C as meiosis works best at this temperature. Functions of seminal fluid: • Allows sperm to swim • Provides nutrients (fructose) • Lubricant • Protects sperm 
 Hormones in the male reproductive system The pituitary gland secretes FSH (follicle stimulating hormone) causing the production of sperm in the testes. Sperm is produced by meiosis in the testes. Sperm-producing cells are diploid (46 chromosomes) and they divide by meiosis to form haploid sperm cells (23 chromosomes). 
 The female reproductive system Function Ovaries Produce the haploid egg cells by meiosis and hormones Fallopian tubes (oviduct) Egg is either fertilised or dies here. Uterus (womb) To receive, hold and nourish a fertilised egg - Implantation occurs here. Cervix Area between vagina and uterus Vagina Organ of copulation and is the birth canal. Vulva (labia folds) The labia are folds of skin that protect the vagina Female hormones FSH Promotes development of a follicle which produces oestrogen. LH Stimulate ovulation and promotes corpus luteum development, which secretes progesterone in the ovaries. Progesterone: Allows uterus to grow during gestation, inhibits lactation prior to birth, develops the mammary glands, induces labour, inhibits immune response to embryo and the ovary also secretes oestrogen. Oestrogen: Promotes the secondary sex characteristics in the female, promotes the development and growth of the mammary gland. Animal gestation Cow 21 days 18-24 hrs 283 days Sheep 17 days 36 hrs 149 days Pig 21 days 2-3 days 115 days Seasonal breeding: determined by length of day (photoperiod). Sheep are short-day breeders, they breed when daylight hours begin to reduce. Birthing process Oxytocin hormone causes contractions to occur to push the baby out as well as milk let down after birth. Birth in cows and sheep A few days before birth, the udder swells. Ligaments around the base of tail relaxes and pelvic bones widen. Forelegs leave first followed by head tucked in between. Hind legs can come first sometimes, this is generally ok but there is an increase in problems. Umbilical cord is cut in two places and tied. The navel is disinfected with iodine. The mother should be allowed to lick her calf or lamb clean. The placenta is expelled soon afterwards, and it is removed by farmer to prevent any infections being spread or predator attraction.