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(C) Gametogenesis. Process by which gametes are produced in the gonads Two types: - Spermatogenesis - Oogenesis. Oogenesis. The primary oocyte goes through first meiotic division and the cytoplasm of the cell is divided unequally
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(C) Gametogenesis • Process by which gametes are produced in the gonads • Two types: -Spermatogenesis - Oogenesis
Oogenesis • The primary oocyte goes through first meiotic division and the cytoplasm of the cell is divided unequally • The larger daughter cell is called the secondary oocyte and the smaller daughter cell is called the polar body • During second meiotic division, 1 mature ovum is produced and 3 polar bodies
Spermatogenesis • Primary spermatocyte goes through first meiotic division and form two daughter cells of equal size • Each daughter cell (secondary spermatocyte) goes through the second meiotic division forming four motile sperm cells of equal size
Comparison of Ova and Sperm • Egg cells contain stored food in the form of yolk • Egg cells are larger than sperm • Sperm are motile, egg cells are not
(B) Fertilization • The fusion of the nuclei of one sperm with one ova (egg) to produce a zygote • Sperm (n) + Ovum (n) =2n • Sperm (23) + Ovum (23) = 46
Parthenogenesis • An embryo develops from an unfertilized egg • typically involves the development of eggs into viable offspring from females without fertilization by sperm.. • Parthenogenesis is no longer only for lower invertebrates, such as aphids, mites and nematode worms--it's also been found in fish, bees, birds and lizards. the second polar body -- the daughter cell produced along with the egg in the second stage of meiosis -- acts like a sperm and re-enters the egg. Essentially the egg fertilizes itself! As this polar body contains identical genetic material to the egg, having been produced by normal division of an already haploid cell, the resulting diploid cell has only half the genetic diversity of the female's original cells. Thus fewer bands appear in the DNA fingerprint of the offspring.
Fertilization • Union of a haploid sperm nucleus with a haploid egg nucleus • This results in a diploid zygote with the full number of chromosomes n n 2n
Fertilization • Union of a haploid sperm nucleus with a haploid egg nucleus • This results in a diploid zygote with the full number of chromosomes
Two types of Fertilization External Fertilization Internal Fertilization **Parthenogenesis**
External Fertilization • Eggs are fertilized outside the body of the female • Large number of eggs are required • This type of fertilization is found in an aquatic environment • Ex: fish and frogs
Spawning??? http://www.umces.edu/2002Session/oyster.html
Do Now What are some differences between External and Internal Fertilization?Provide examples!!!
Internal Fertilization • Takes place inside the body of the female • Less eggs are required Ex: mammals, birds and reptiles
The embryo arrives in the uterus 5-10 days after fertilization • The embryo implants into the uterine wall and establishes pregnancy • Placenta- nourishes the embryo • Umbilical cord- attaches the embryo to the placenta • Amnion- embryo develops inside the amniotic sac which contains amnioticfluid that serves as a shock absorber • Gestation Period- length of pregnancy (approximately nine months)
Good Review Webpage http://regentsprep.org/Regents/biology/biology.cfm
Fallopian tube Zygote 4 cells 2 cells Morula Blastocyst Uterine wall Ovary Fertilization and Implantation Section 39-4 Day 2 Day 3 Day 1 Day 4 Fertilization Day 0 Day 7 Implantation of blastocyst Egg released by ovary http://regentsprep.org/Regents/biology/units/reproduction/index.cfm http://regentsprep.org/Regents/biology/biology.cfm
Development • The zygote, which is a fertilized egg consisting of one cell, will begin to divide rapidly by mitosis forming the early developing human embryo. Fertilization and the initial stages of this mitotic cell division occur in the oviduct. The early embryo is migrates down the fallopian tube and completes most of its development in the wall of the uterus.
Do Now Ectoderm Mesoderm Looking at the diagram above. Hypothesize the systems that will develop from these three layers. • Reproductive • Muscles, • Skeleton • Digestive • Nervous • ETC Endoderm
It is the three germ layers that give rise to all the tissues and organs of an animal
Do Now • Identify what is the purpose of the following: • The placenta: • The umbilical cord:. • The amniotic fluid:
Do Now answers • The placenta is a combination of maternal and fetal tissue which allows for the exchange of materials with the fetus and mother. Needed materials such as food and oxygen diffuse through the placenta to the fetus, while wastes from the fetus diffuse to the mother. • The umbilical cord is a fetal structure containing blood vessels which allows materials to be carried between the fetus and placenta in both directions. • The amniotic fluid surrounds the fetus and helps to provide a shock absorber to protect the fetus against mechanical injury in the event the mother is shaken or injured in some manner.
Fetal Development • Development is a highly regulated process After this small cluster of cells called the gastrula forms in humans, tissues begin to form. In humans, the embryonic development of essential organs occurs in early stages of pregnancy. During the first three months of human development, organs begin to form. • The human embryo is usually referred to as a fetus when human like features become visible in its structure. • All organs and body features are developed by the end of the sixth month. During the last three months of pregnancy, organs and features develop well enough to function after birth.
What are some things that could affect fetal development? • The embryo (or fetus) may encounter risks from faults in its genes and from its mother's exposure to environmental factors such as: • inadequate diet • use of alcohol (Fetal alcohol syndrome) • Tobacco • Drugs • other toxins • infections
Reproductive Technologies • Reproductive technology has medical, agricultural, and ecological applications. In many instances, these technologies have progressed at a faster rate than the ethical considerations resulting from these technologies. • Some of these techniques include birth control methods used to block the process of fertilization. • Many technologies now exist to enhance the process of fertilization and development in humans and other organisms. • Amniocentesis • Hormone therapy can cause increased egg production. • Surgery can open blocked fallopian tubes in females and the vas deferens in males. • In vitro fertilization (test-tube babies) is a widely used technique to aid infertile couples, allowing them to have children where this otherwise would not be possible.
Fetal cells are removed and surveyed for genetic disorders Amniocentesis
(IV) Multiple Births 1. Identical twins- Develops from one zygote separating into two during cleavage. One sperm and one egg is involved and therefore the babies will look identical and must be of same sex
(IV) Multiple Births 1. Identical twins- Develops from one zygote separating into two during cleavage. One sperm and one egg is involved and therefore the babies will look identical and must be of same sex
Identical twins do not have identical fingerprints. They are a product of their environment.
Eng Bunker---Chang BunkerBorn: May 11, 1811 Died: January 11, 1874
