9 Sex cells – sperm In males, the sex cells are called sperm. Sperm are produced in sex organs called testes.
10 Sex cells – egg In females, the sex cells are called eggs. Eggs are produced in sex organs called ovaries.nucleus containingchromosomescytoplasmmembranejelly coatAn egg is so big that this is how small a sperm looks next to it.
14 Sexual ReproductionAlthough all cells carry the genetic code, special cells are produced for sexual reproduction – they are called gametes.In animals, these are the eggs and sperm.In plants, they are the eggs and pollen.Gametes are different from all other cells because they only carry one copy of each chromosome.For example, human gametes (sperms and eggs) have only 23 chromosomes, not 46 like all other body cells.
15 The process of a male and female gamete combining is called fertilisation. The fertilised egg is called a zygote and is the very first cell of a new individual.A zygote will have the normal number of chromosomes – one half from the male gamete, another half from the female gamete.This whole process is called sexual reproduction.
20 Male sex cellsIn males, the sex cells are called sperm. They are made in the testes
21 An egg is so big that this is how small a sperm looks next to it. Female sex cellsIn females, the sex cells are called eggs. They are made in the ovary.nucleus containingchromosomesAn egg is so big that this is how small a sperm looks next to it.
23 Ovulation and fertilization In the female, one of the ovaries releases an egg every28 days. This is called ovulation.During sexual intercourse millions of sperm are ejaculated into the vagina.If a sperm meets the egg a zygote is formed. This called fertilization.
25 What happens after fertilisation? Once the zygote is made the cells divide many timesIt is now called an embryo and it will sink into the lining of the uterus, this is called implantation.
26 The placenta How does an embryo get food and oxygen and how does it get rid of waste?A placenta is formed which allows it to exchange material with the motherThe umbilical cord joins the embryo to the placenta.
28 What happens in the placenta? In the placenta, food and diffuse from the mother’s blood into the blood of the fetus.Carbon dioxide and waste products diffuse from the blood of the fetus to the mother’s blood.
29 From embryo to fetus After the first eight weeks of pregnancy, a human embryo is then called a fetus.The fetus continues to develop and grow inside its mothers’ uterus for a total of40 weeks.What happens next?