LC-DevelopmentHW

Human Life Cycle 16.1 p. 320 INSERTING FIGURES IS ALWAYS A GOOD THING. (1) How many chromosomes does a mother contribute to a new individual? A father? - Each give 23 chromosomes so that the fertilized egg has the normal 46. (2) Where does meiosis occur in males? in females? - Males: testes -Females: ovaries (3) Compare an egg cell to a sperm cell. - An egg is large and complex and the sperm cell is solely there to deliver 23 chromosomes. The egg waits for the sperm and provides it cytoplasm and nutrients. (4) What is the difference between meiosis and mitosis. - Meiosis is also known as reduction division. Mitosis is duplication devision that takes place during human development and repair. Meiosis takes place only in the sexual organs to make the 46 chromosomes split to 23.

Development Chapter 17 17.1 (5) Describe in detail how fertilization occurs - After intercourse, the sperm swims to the egg and moves through the plasma membrane into the cytoplasm of the egg. Then the sperm pro nucleus breaks off and provides the nucleus of the egg with 23 chromosomes, at that point the egg is now a zygote. (6) What is polyspermy and how is prevented during fertilization? - Polyspermy is when more than one sperm fertilizes the one egg. 17.2 (7) Describe the processes involved in development. - Cleavage: the cells and chromosomes divide and multiply rapidly without increase in size - Growth: cell division is finally a size increasing process. - Morphogenesis: shaping of the embryo and the embryo begins to shape a person. - Differentiation: cells take on the different function of the body. (8) What are the extraembryonic membranes and what is their role? - Chorion: this develops into the fetal half of the placenta, the organ that provides the embryo with nourishment and oxygen and takes away its waste. - Allantois: extends away from the embryo. It accumulates the urine in the fetal kidneys and connects to the umbilical arteries. - Yolk: first membrane to appear. contains plentiful blood vessels. - Amnion: this membrane is closest to the baby and contains fluid protecting the fetus. (9) What happens during pre-embryonic development? - the first week of development in which the zygote reproduces cells called the morula and becomes a blastocyst. (10) What happens during embryonic development? - Second Week: implantation: embryo begins to implant in the wall of the uterus. - Third Week: nervous system and heart appear - Fourth and Fifth Week: the umbilical cord is completely formed and connected - Sixth through Eighth Weeks: cells have a job and the fetus appears to be a human in development (11) What are the primary germ layers and what body structures come from each layer? Ectoderm: epidermis of skin; epithelial lining of oral cavity and rectum: nervous system Mesoderm: skeleton; muscular system; dermis of skin; cardiovascular system; urinary system; reproductive system; outer layers of respiratory and digestive systems Endoderm; Epithelial lining of digestive tract and respiratory tract; associated glands of these systems; epithelial lining of urinary bladder.