(c) gametogenesis
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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 - PowerPoint PPT PresentationTRANSCRIPT
(C) Gametogenesis
Process by which gametes are produced in the gonads
Two types:
- Spermatogenesis
- Oogenesis
OogenesisThe primary oocyte goes through first meiotic division and the cytoplasm of the cell is divided unequallyThe larger daughter cell is called the secondary oocyte and the smaller daughter cell is called the polar bodyDuring second meiotic division, 1 mature ovum is produced and 3 polar bodies
SpermatogenesisPrimary spermatocyte goes through first meiotic division and form two daughter cells of equal sizeEach 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.
Parthenogenesis
FertilizationUnion of a haploid sperm nucleus with a haploid egg nucleusThis results in a
diploid zygote with the full number of chromosomes
n
n
2n
FertilizationUnion of a haploid sperm nucleus with a haploid egg nucleus
This results in a diploid zygote with the full number of chromosomes
Fertilization and the Stages of Mitosis
Two types of Fertilization
External Fertilization
Internal Fertilization
**Parthenogenesis**
•Eggs are fertilized outside the Eggs are fertilized outside the body of the femalebody of the female
•Large number of eggs are Large number of eggs are requiredrequired
•This type of fertilization is This type of fertilization is found in an aquatic environmentfound in an aquatic environment
ExEx: fish and frogs: fish and frogs
External FertilizationExternal Fertilization
Spawning???
http://www.umces.edu/2002Session/oyster.html
External Fertilization
External Fertilization
External Fertilization
External Fertilization
What are some differences between External and Internal
Fertilization?
Provide examples!!!
External Fertilization
External Fertilization
External Fertilization
External Fertilization
Internal Fertilization
Takes place inside the body of the female
Less eggs are required
Ex: mammals, birds and reptiles
Internal Fertilization
The embryo arrives in the uterus 5-10 days after fertilizationThe embryo implants into the uterine wall and establishes pregnancyPlacenta- nourishes the embryoUmbilical cord- attaches the embryo to the placentaAmnion- embryo develops inside the amniotic sac which contains amniotic fluid that serves as a shock absorberGestation Period- length of pregnancy (approximately nine months)
Fertilization
Good Review Webpage
http://regentsprep.org/Regents/biology/biology.cfm
Implantation of blastocyst
Day 7 Fertilization
Day 4
Day 3 Day 2
Day 1
Day 0
Egg released by ovary
Fertilization and Implantation
Section 39-4
Uterine wall
Blastocyst
Morula
4 cells 2 cells Zygote
Ovary
Fallopian tube
http://regentsprep.org/Regents/biology/units/reproduction/index.cfmhttp://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 NowDo Now
Looking at the diagram above. Hypothesize the systems that will develop from these three layers.
Reproductive
Muscles,
Skeleton
Digestive
Nervous
ETC
Ectoderm
MesodermEndoderm
It is the three germ layers that give rise to all the tissues and organs of an animal
Ectoderm Mesoderm EndodermNervous system
Digestive System
lining of mouth, nostrils, and anus
epidermis of skin, sweat glands, hair, and nails
bones and muscles
blood and blood vessels
reproductive and excretory system
dermis layer of skin
lining of digestive tract
lining of trachea, bronchi, and
lungs
liver, pancreas
thyroid, parathyroid
urinary bladder
The Three germ layers
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.
Human Development
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 What are some things that could affect fetal development? fetal development?
6 weeks 4 months
What are some things that could affect What are some things that could affect fetal development? 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 dietuse of alcohol (Fetal alcohol syndrome)TobaccoDrugsother toxins infections
Reproductive TechnologiesReproductive 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.
Amniocentesis
Fetal cells are removed and surveyed for genetic disorders
Reproductive Technologies
(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.
Conjoined Twins
Conjoined “Siamese” Twins Chang and Eng
Eng Bunker---Chang BunkerBorn: May 11, 1811 Died: January 11, 1874
The developing embryo begins to split into identical twins but then
stops part way leaving the partially separated egg to mature
into a conjoined fetus.
They are more often female than male (ratio of 3:1)
They occur as often as once in every 40,000 births but only once
in every 200,000 live births.
40% are still born
70% are female - even though monozygotic twins are more frequently male than female.
75% are still born or die within 24 hours.
Cephalophagus
Dicephalus
This refers to one body with two heads.
Ischophagus
Anterior union of the lower half of the body
http://www.conjoined-twins.i-p.com/
Conjoined twins
Parasitic twins: Asymmetrical conjoined twins, one twin being small,
less formed, and dependent upon the other.
Fetus in fetu: Situation in which an imperfect fetus is contained
completely within the body of its sibling.
(V) Multiple Births
Fraternal twins- Develop from two separate eggs, each fertilized by separate sperm cells. Therefore, the babies may not look identical and could be of different sex. Simply ciblings!
(V) Multiple Births
Fertility drugs often cause production of more than one ovum during ovulation. Septuplets = 7 ova + 7 sperm (7 zygotes)
(V) Multiple Births