Book : Living Body
posted by
Posted by: CHELSEA
posted by
Writer CHELSEA

Sexual Reproduction

image about


Overview

Sexual reproduction is a way of reproduction of some animals and plants. Some protists and fungi also reproduce this way. Organisms that reproduce sexually have two different sexes: male and female. Offspring is made by a cell from the male and a cell of the female. Different steps are involved in the process. The cells of an animal or higher plant have two sets of chromosomes: they are diploid. When gametes (sex cells) are produced, they have only one set of chromosomes: they are haploid. They have undergone a process of cell division called meiosis. During meiosis, crossing over occurs. This makes it possible to get recombination. This has various consequences. It means, for example, that all the children of two parents are not identical, except in the rare case where they developed from the same fertilized egg. The second step is called fertilization. In it, the two cells merge into one. This restores the diploid state. Fertilization is what happens when a female's ovum (or "egg") joins together with a male's sperm and they form a zygote. Fertilization is also called conception. In humans, biologists call a fertilized egg a zygote.

Zygote

A zygote is the fertilized cell that will grow into a baby animal. When a female's ovum and a male's sperm cell become one, this cell is called the zygote. The zygote then multiplies, and grows into an embryo. A zygote is the cell that results from fertilization. A zygote is synthesized from the union of two gametes, and constitutes the first stage in a organism's development. Zygotes are produced by fertilization between two haploid cells, the ovum and the sperm cells, which make a diploid cell. Diploid cells have copies of parent chromosome or DNA. Some animals keep the zygote in their bodies until it is a full-grown baby. The time between the forming of the zygote and the baby's birth is called pregnancy. Other animals do not keep the zygote in their bodies, but lay an egg. The zygote grows inside the egg until it is ready and the baby animal hatches. The fertilized egg now starts to divide and produce the embryo. It is called an embryo from 3-8 weeks (the embryonic period.) Then after 8 weeks, it is called a fetus. If it continues to grow normally it can eventually become a baby.

Terms:

Gonads- specialized sex organs where gametes are formed. In the male, the gonad is the testes, while in the female, the gonad is the ovaries. Diploid cells- (indicated by 2n) have two homologous copies of each chromosome, usually one from the mother and one from the father. Haploid cells -The haploid number (n) is the number of chromosomes in a gamete. Gametes -- specialized sex cells formed in gonads by gametogenesis. The male gamete is the sperm, and the female is ovum(ova pl) or egg. Zygote - produced by fertilization between two haploid cells, the ovum and the sperm cells, which make a diploid cell.


related articles

Blood Vessels

Blood Vessels

  • Basics
  • posted Date:2017 Sep, 14

OverviewThese are a network of tubes that transport the blood ar...

read more
Breathing and Respiration

Breathing and Respirat...

  • Basics
  • posted Date:2017 Sep, 14

OverviewMany people confuse the terms Breathing and Respiration...

read more
Gas Exchange

Gas Exchange

  • Basics
  • posted Date:2017 Sep, 14

OverviewIn order to...

read more

Subscribe With Us For Daily Reading Lesson Materials