Reproductive System Two types of reproduction Sexual two

Reproductive System

Two types of reproduction: • Sexual: two parents; offspring is a mixture of DNA from both parents • Asexual: one parent; offspring is genetically identical to the parent example: bacteria, some protists, fungi, some plants & animals

Benefits • Sexual reproduction: leads to genetic variation within a population without which there could be no evolution. • Asexual: 1. lots of offspring quickly 2. don’t need to find a mate

• Human life begins with the joining of two specialized cells gametes from two parents. • Male gamete: sperm • Female gamete: egg

• When the egg and sperm join it is called fertilization. • The fertilized egg is called a zygote.

Chromosome Count • Human body cells have 46 chromosomes that form 23 pairs. • Gametes are produced through a process called meiosis which reduces the chromosome number by ½ to 23 23 23 Zygote 46 EGG Sperm Mom Dad YOU!!

• All offspring produced through sexual reproduction get half of their chromosomes from each parent.

Male Reproductive System • The main job of the male reproductive system is to produce sperm and deliver it to a woman’s fallopian tube so it can fertilize the egg. • The main reproductive organs in males are the testes (singular testis), or testicles. • The testes are located outside the body in a sac called the scrotum.

Male Reproductive System • Structures include testes, scrotum & penis. • The sperm exit the male body through the penis.

Hormones • Sperm development results from the release of hormones. A hormone is a chemical made in one part of the body that affects the activities of cells in other parts of the body. The blood carries hormones through the body. • Once males begin to produce sperm, they can do so for the rest of their lives.

Female Reproductive System • Functions: to produce eggs that carry the female’s genetic information and, if an egg is fertilized, to nourish a developing baby until birth. • Organs include ovaries, fallopian tubes, uterus & vagina.

Female Reproductive System • There are two - one on each side • Females are born with all the eggs they will ever have. • Comes form the Latin word ova, meaning “eggs”.

Path of the Egg • Each ovary is connected to a fallopian tube • The fallopian tubes transport eggs (usually one egg each month) from the ovaries to the uterus. • While it is in the fallopian tube, the egg may be fertilized by sperm from a male.

• The uterus is an organ with strong, thick muscular walls that holds and nourishes a growing embryo. • If an egg is fertilized, it develops within the uterus. • The baby exits the mother’s body through the vagina, or birth canal. • The strong contractions that push the baby out of the mother’s body are called labor.

Embryos Develop within a Placenta • Offspring cannot be produced unless an egg is fertilized by a sperm. • The new cell formed when the sex cells unite is called a zygote. • All multicellular organisms begin life as zygotes.

Cell Division • Shortly after forming, the zygote undergoes a series of cell divisions. • Each cell division increases the number of cells in the zygote, so the embryo grows. • The early embryo is a ball of cells.

Mammals and Birth • Human embryos, like those of most other mammals, develop within a placenta. • The placenta is a fluid-filled organ through which materials are exchanged between the mother and the developing offspring. • The embryo is connected to the placenta by the umbilical cord. • Pregnancy is the period from fertilization to birth. In humans, pregnancy lasts about nine months.