Asexual Reproduction Is a method of reproduction with all the genetic information coming from one parent. Some Methods of Asexual Reproduction 1. binary fission -- involves an equal division of both the organism cytoplasm and nucleus to form two identical organisms -- the diagram of the protist at the right is example of this 2. budding -- involves one parent dividing its nucleus (genetic material) equally, but cytoplasm unequally -- the diagram of a yeast at the right is an example of this
3. sporulation (spore formation) -- is reproduction involving specialized single cells coming from one parent -- the diagram of mold spores being formed at the right is an example of this• Asexual reproduction is sometimes called cloning.• Cloning is the production of identical genetic copies. • All forms of asexual reproduction are variations of the cell division process of mitosis.•Mitosis is associated with asexual reproduction, as well as growth and repair in sexually reproducing organisms.
Mitosis Mitosis is the method used for cell division and reproduction in cells not involved in sexual reproduction. This process starts with one replication (copying of the chromosome material) and one division of the chromosome material.This results in the chromosome numbers in the two cells produced being the same as in the parent cell.
2 Key Results of Mitosis1. The same chromosome number is retained from generation to generation.2. Each daughter cell receives an exact copy of the chromosomes of the parent cell.(clones)
Sexual Reproduction•The process of sexual reproduction involves two parents.•Both parents normally contribute one gamete or sex cell to the process.• This process assures that the genetic information given to the offspring will be obtainedequally from each parent.•The female gamete is called the egg or the ovum and the male gamete is called asperm. These gametes are formed in specialized reproductive structures called gonads.The sperm is much smaller than the egg, but is capable of moving on its own power usinga whip-like tail called a flagellum. Sperm and Egg (fertilization) The sperm and egg unite in a process called fertilization. This process forms a single celled structure called a zygote which contains the complete genetic information to develop into a complete new organism having characteristics of both parents.
Process of FertilizationThis zygote will then divide by mitosis and form the specialized cells, tissues, and organs of the organism.This development of specialized structures from the zygote is called differentiation.
Meiosis•The process of meiosis produces gametes or sex cells.•The process of meiosis halves the chromosome number from the original parentcell in the four cells it forms. It does this by having two cell divisions forming fourcells, where mitosis has only one cell division forming two cells.•Both processes start out with one doubling or replication of the chromosomematerial. Process of Meiosis
Another important way that meiosis differs from mitosis is the exchange ofchromosome pieces which occurs in the first division of this process. Thisexchange of chromosome pieces is called crossing over. Crossing Over and Genetic Recombination
Development Initial Development and Differentiation •The processes of gamete production, fertilization, and development follow an orderly sequence of events. • Zygotes contain all the information necessary for growth, development, and eventual reproduction of the organism. •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. Fertilization and Initial Development of the Embryo
•The placenta is a combination of maternal and fetal tissue which allows for theexchange of materials with the fetus and mother. Needed materials such as food andoxygen diffuse through the placenta to the fetus, while wastes from the fetus diffuse tothe mother.•The umbilical cord is a fetal structure containing blood vessels which allows materialsto be carried between the fetus and placenta in both directions.• The amniotic fluid surrounds the fetus and helps to provide a shock absorber toprotect the fetus against mechanical injury in the event the mother is shaken or injuredin some manner.
Fetal Development in the UterusThe embryo will eventually develop into a three cell layered structure. Thisstructure is called a gastrula and will eventually differentiate to form thespecialized cells. Differentiation means that the cells will develop specificjobs and develop into specific tissues in the maturing organism.
Fetal Development•Development is a highly regulated process•After this small cluster of cells called the gastrula forms in humans, tissues beginto form. In humans, the embryonic development of essential organs occurs in earlystages of pregnancy.• During the first three months of human development, organs begin to form. Thehuman embryo is usually referred to as a fetus when human like features becomevisible 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 wellenough to function after birth.
Human Development at 6 Human Development at 4 weeks months The embryo (or fetus) may encounter risks from faults in its genes and from itsmothers exposure to environmental factors such as inadequate diet, use of alcohol, tobacco, drugs, other toxins, or infections. .
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