Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Reproduction • Reproduction: the creation of new individuals from a parental generation. Two types: • Asexual: one parent • Sexual: two parents: recombinant DNA Couple types of asexual reproduction paramecium 1. Binary fission: parent divides into two equal organism Organisms: bacteria and single celled organisms Similar to mitosis of multi-cellular organisms Binary fission animation 2. Budding: New individuals grow or bud on the surface of the parent. • may break off and live independently or remain attached. Organisms: Yeast, hydra, sponges • Sexual reproduction involves DNA being combine from two organism • creates recombinant DNA and many genetic variations. • The DNA needs vehicles in order recombine. EXAMPLE • Humans: sperm and egg • Flower: pollen and egg • We will focus on human reproductive system • • • • • Gametes: sex cells. Male gamete: sperm female gamete: egg both are haploid Haploid: single set of chromosomes (23) • Sperm + egg = zygote • Zygote: union of sperm and egg. • Fertilization: Remember the sperm and egg are haploid. • Once they combine it’s the first diploid cell. • It then divides into many diploid cells. How are gametes created? • Meiosis: The process of meiosis produces gametes or sex cells. 1. 2. 3. 4. Start with a diploid cell DNA replicates The cell divide into two cells It then divides again into four haploid cells that are all different. • Similar but different to mitosis. Differences between mitosis and meiosis: 1. Meiosis: creates gametes Mitosis: creates body cells 2. Meiosis: Daughter cells have half the chromosomes as the parent cell (haploid). Mitosis: Daughter cell have the same number of chromosomes as parent cell 3. Meiosis: Two divisions creates four daughter cells Mitosis: One division creates two cells 4. Meiosis: all four cells are genetically different Mitosis: two daughter cells are identical Divisions DNA Meiosis Mitosis 2 1 Half of parent Equal to parent Nucleus Haploid diploid Variations All unique All Identical End Four haploid gametes Two diploid body cells mitosis meiosis One division One division second division 2 genetically identical diploid body cells 4 genetically different haploid gametes Meiosis animation: • starts with one diploid cell. • Two divisions • Ends with four different haploid gametes 23 Chromosomes 23 Chromosomes 46 Chromosomes 23 Chromosomes 2nd division 1st division 23 Chromosomes 23 Chromosomes 23 Chromosomes Complete the meiosis diagram for an organism that has 8 chromosomes 1st division 2nd division • • • • Zygote: union of egg and sperm. It is the first single diploid cell Diploid: two set of chromosomes (46) Zygote divides many times until the human develops. • Haploid is written: (n) • Diploid is written: (2n) Zygote divides Male Reproductive System Main structures : 1. Testes 2. The epididymis 3. The vas deferens 4. The urethra 5. The penis • These structures work together to produce and deliver sperm. • Male reproductive organs are on the outside of the body. • It is one to three degrees Celsius lower • This temp difference is necessary for sperm development. • Males hormone: testosterone. • Testosterone produces secondary sexual characteristics in males • Secondary sex characteristics are those that do not include the sex organs: facial or body hair and deepening of the voice. • Puberty is complete when the testes have produced enough functioning sperm. Sperm • A sperm is made of a head, midpiece, tail and acrosome: A. Head: had the nucleus with DNA B. Mid-piece: has many mitochondria to make ATP, energy. C. Tail (flagellum): movement D. Acrosome: Small cap on the head that contains an enzyme needed for fertilization. • Sperm are made in the testicle • Stored in the epididymis. • They exit the body through the vas deferens. • The vas deferens connects to the urethra, a tube that leads to the outside of the body. • Seminal fluid: nutrient rich fluid • Semen: Seminal fluid and sperm together • There are between 50 and 130 million sperm in 1 mL of semen. Sperm Release • Ejaculation: Sperm are ejected from the penis by the contractions of smooth muscle lining • About 2 to 6 mL of semen with 200 to 600 million sperm are released • They are released in the reproductive tract of a female, • These large numbers make the chances of fertilization very good. Female Reproductive System Main structures: 1. The ovaries 2. The fallopian tubes 3. The uterus 4. The vagina • Function: produce eggs, prepare the body to nourish a developing embryo. Egg development • The ovary contains 400,000 eggs (primary follicles) • Primary follicles: cluster of cells (immature eggs) surrounding a single egg. • Function of a follicle: help egg mature • Females do not produce any new eggs during her life time • only about 400 of the 400,00 eggs will mature. • Each month, one follicle grows and passes through the early stages meiosis. • Meiosis: how sperm and egg divide. • At the end of meiosis, females have one large haploid egg and three smaller cells called polar bodies. Egg release • Ovulation: When the follicle has completely mature, the egg is released • The follicle breaks open, the egg leaves the ovary into the opening of one of the two fallopian tubes. • The egg is often fertilized in the fallopian tube • The egg is then passed into the uterus. • The uterus is prepared to accept the fertilized egg, if fertilization has occurred. • Cervix: outer end of the uterus • Beyond the cervix is a canal called the vagina, leading to the outside of the body. The Menstrual Cycle • The reproductive and endocrine systems in females causes the menstrual cycle. • It takes about 28 days. • During the cycle, an egg matures and is released from the ovary. • The wall of the uterus thickens in preparation to accept the fertilized egg. • If the egg is fertilized, it is implants in the uterus and development begins. • If its not fertilized, the egg is discharged along with the lining of the uterus and blood: we call this her period. • This is the menstruation cycle: What is fertilization? • During sexual intercourse, semen is ejaculated from the penis into the vagina. • Sperm swim through the uterus into the fallopian tube. • If an egg is present in the fallopian tubes, it has a good chance of being fertilized because millions of sperm are released. • Only about one percent reach this area however. • The egg has a thick protective covering. • Acrosome: sac on the head of the sperm has enzymes. • When the sac hits the protective coat on the egg, the enzymes are released and break it down. • When the head of the sperm (haploid) penetrates the egg (haploid), • the two nuclei are joined together to form one diploid cell (fertilized egg). • Acrosome digests protective coating of the egg. • Zygote: the fertilized diploid egg. • The zygote then divides by mitosis to form a ball of cells. The ball attaches to the wall of the uterus and continues to divide. • Implantation: ball of cells attaching to uterus. Egg implanting in uterus • Fertilization in the fallopian tubes • implantation Fertilization • A zygote (fertilized egg) smaller than a period on this page divides by mitosis to form a new human being. • Stem cells: first cluster of cells that are unspecialized • Differentiation: eventually cells become specialized organs like brain and heart. • The placenta • The placenta is a connection between the mother and the embryo. • It serves as a source of nutrients and oxygen for the embryo. • Also eliminates wastes such as carbon dioxide • The placenta is the embryo’s organ of respiration, nourishment, and excretion. • Embryo does on get blood directly from mother. Why? • May have different blood types, also protect from diseases. • Some can pass such as rubella (german measles) • Alcohol and prescription drugs can also be passed by the placenta. • After 8 weeks, the embryo is called a fetus. • Most organs and tissues are fully developed (differentiation). • Umbilical chord forms which connects fetus to placenta. Childbirth • Nine months after fertilization, a baby is born. • When baby meets the outside, he or she may begin to cry, this rids the lungs of fluid. • Breathing starts almost immediately, and umbilical chord is cut. • Baby now leads an independent existence and has own supply of oxygen, and excretes own waste. • Comparing Reproduction of different species • Species possess different adaptations for reproduction and development. Possibilities • External fertilization • Internal fertilization • External development • Internal development • External Fertilization: The fertilization in water outside the body • External Development: Young organisms develop outside the mother in the water • Disadvantage: eggs and young have little or no protection. • Organisms: fish and amphibians • Most of their babies are eaten by predators. • Internal fertilization: male inserts sperm inside female. • External development: female lays fertilized eggs for development outside the body. • Advantage: Lay fewer eggs and provide more protection for young. • Organism: Reptiles and birds • Internal fertilization • Internal development: baby develops within the female womb. • Advantage: release few eggs that are well protected by parents. • Organisms: mammals