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Ms. Randall

Unit 5: Reproduction & Development. Ms. Randall. Lesson 1: Meiosis and Sexual Reproduction Objective: To describe the products of meiosis. To relate meiosis to genetic variation. Review of Asexual Reproduction. Single parent gives rise to new offspring by mitotic cell division.

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Ms. Randall

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  1. Unit 5: Reproduction & Development Ms. Randall

  2. Lesson 1: Meiosis and Sexual Reproduction Objective: To describe the products of meiosis. To relate meiosis to genetic variation.

  3. Review of Asexual Reproduction Single parent gives rise to new offspring by mitotic cell division. Each new individual receives a set of chromosomes identical to the parent chromosomes. No variation of hereditary information.

  4. Types of Asexual Reproduction

  5. I. Sexual Reproduction • Twoparents give rise to new offspring by the fusion of nuclear materials from two different cells. • Offspring are NOT identical to the parent. • Variations exist, which increases the species ability to adapt to the changing environment. • Gametes - Sex cells 1. Males – sperm 2. Females – ovum (egg)

  6. Haploid vs. Diploid Haploid - Also known as monoploid. Represented by: n • The gametes contain half the number of chromosomes. • Once they fuse (combine), they form a zygote that is diploid. Diploid - Contain the full number (set) of chromosomes. Represented by: 2n • Homologous Chromosomes • Pairs of similar chromosomes • Humans have 46 chromosomes: • 22 pairs of homologous chromosomes • 1 pair of sex chromosomes

  7. Fertilization The fusion of the nuclei of one sperm with one ova (egg) to produce a zygote.

  8. How are Gametes formed? Meiosis - a type of cell division in which the daughter cell receives only half the number of chromosomes present in the parent cell. • 2 cell divisions occur but DNA is only copied once. • 23 Pairs of chromosomes of a human cell • The chromosomes labeled X and Y are the sex chromosomes. • XX = female • XY = male

  9. Genetic Variation Crossing over is the exchange of pieces of homologous chromosomes during meiosis. The pairing of homologous chromosomes is called synapsis. Crossing over occurs during synapsis, when the chromosomes are in this group of 4 called a TetradduringProphase I

  10. Genetic Variation • Independent Assortment - the random arrangement and separation of chromosomes during meiosis increasing genetic variation in the sex cells • Recombination (genetic recombination) - After synapsis & crossing over, the homologous chromosomes line up in the center of the cell. • Random ordering leads to different combinations of chromosomes in the resulting sex cells, increasing genetic variation in the offspring.

  11. Genetic Variation Crossing over (the exchange of pieces of homologous chromosomes) and recombination lead to genetic variation - new groupings of genes in the egg and sperm. • This increases genetic variation in the offspring and increases species survival in a changing environment.

  12. Compare & Contrast

  13. Check your understanding and practice

  14. Lesson 2: Sexual Reproduction in Animals Objective:To compare and contrast internal and external fertilization and internal and external embryonic development.

  15. Reproductive System Gonads-specialized organs that produce gametes. a) ovaries - female gonad - produce ova (eggs) b) testes - male gonad - produce sperm Hermaphrodite - Contain both male and female reproductive structures.

  16. Fertilization Union (joining) of a haploid sperm nucleus with a haploid egg nucleus. This results in a diploid zygote with the full number of chromosomes.

  17. Two types of Fertilization External Fertilization • Eggs are fertilized outside the body of the female. • Large numbers of eggs are required. • Takes place in an aquatic environment. • Ex: fish and frogs Internal Fertilization • Takes place inside the body of the female. • Less eggs are required. • Ex: mammals and birds

  18. Embryonic Development In the early stages of development, the organism is called an embryo. The process of embryonic development includes: 1. Cleavage 2. Gastrulation 3. Growth and Differentiation

  19. Cleavage & Gastrulation Cleavage is a series of mitotic divisions where the cell increases in cell number but NOT in cell size. Cleavage converts a single fertilized egg (zygote) into many cells. As cleavage continues, the cells form a hollow ball-type structure filled with fluid. At this point, the embryo is called a blastula. When the blastula reaches several hundred cells, gastrulation occurs. In this stage, the cells on one side of the blastula push in and form a two-layered embryo called the gastrula.

  20. Gastrula

  21. Growth and Differentiation Differentiation- series of changes that transform the unspecialized embryonic cells (stem cells) into specialized cells, tissues and organs. Growth- not only are the number of cells increasing, but the size of the cells are increasing as well and the embryo as a whole starts to develop.

  22. External Development Development occurs outside the female body a) In water: 1. Nourishment for the developing embryo is supplied by the yolk stored in the egg. 2. No parental care 3. Examples are fish and frogs b) On land: 1. Production of egg and shell (protection) 2. SOME parental care 3. Developing embryo’s source of food is the yolk. 4. Examples are birds and reptiles

  23. What came first… the chicken or… Structure of Egg • Consists of 4 membranes outside of the embryo. • chorion- outer-most membrane, aids in gas exchange. • allantois- exchange of O2 and CO2. Also a storage site for wastes. • amnion- sac containing amniotic fluid which surround the embryo, provides cushion • yolk sac- source of food for the embryo

  24. Check your understanding and practice

  25. Lesson 3: Human Development Objective: To compare and contrast the human male and female reproductive anatomy. To relate the human reproductive anatomy to conception and birth.

  26. Internal Development Development occurs inside the female. Placental Mammals • These are animals, like humans, that contain a structure called the uterus where the embryo develops. • Within the uterus, a specialized structure called the placenta forms. Placenta - exchange of nutrients, wastes, and respiratory gases between the embryo and the mother takes place. • The umbilical cord, which contains blood vessels, attaches the embryo to the placenta.

  27. External Development Marsupials • Are mammals that do not have a placenta. • The embryo is born at a relatively premature stage, and completes its development externally in a pouch that contain mammary glands. • Ex) kangaroos and opossum

  28. Reproduction and Development in Humans

  29. Male Reproductive System • Testes - Paired oval structures, located in an out pocketing of the body wall, called the scrotum. • Temperature in scrotum is 2-4 degrees lower than body temperature. • Produce sperm. Secrete testosterone • Vas Deferens - Sperm duct of humans. Carries sperm and fluid in the form of semen. Empties into the urethra. • Semen - A mixture of sperm and fluid from seminal vesicles and prostate gland

  30. Male Reproductive System • Urethra - Carries semen from vas deferens to outside through the penis. • Also carries urine from urinary bladder. • Penis - External male genitalia. • Adaptation for internal fertilization • Release of semen during ejaculation contains about 200-350 million sperm in ~ 3.5 ml

  31. Female Reproductive System Ovaries-Produce Eggs • Paired walnut-sized structures located in the lower part of the abdomen. • They are partially surrounded by funnel-like openings of the oviduct. • The oviducts are called the fallopian tubes. • The ovaries also produce sex hormones known as estrogen and progesterone. • estrogen- used for the development of secondary sex characteristics like mammary glands (breasts). • progesterone- maintains uterus for pregnancy. Oviducts (Fallopian Tubes)- Fertilization occurs here

  32. Female Reproductive System Uterus (womb) - Where embryo develops if fertilization has taken place Cervix - Muscular ring between uterus and vagina Vagina - Birth canal; Receives semen during mating

  33. Conception • Fertilization occurs in the fallopian tubules (oviduct). • If the egg is not fertilized within 24 hours after ovulation, it will deteriorate. • After fertilization, the zygote undergoes cleavage and becomes an embryo. • The zygote arrives in the uterus 5-10 days after fertilization. • The embryo implants into the uterine wall and establishes pregnancy. • Placenta- exchange of nutrients, gases, and wastes between mother and embryo • Umbilical cord- attaches the embryo to the placenta. • Amnion- embryo develops inside the amniotic sac which contains amniotic fluid that serves as a shock absorber. Gestation Period- length of pregnancy (approximately nine months).

  34. Twins • Identical twins- Develops from one zygote separating into two during cleavage. • Onesperm and one egg is involved and therefore the babies will look identical and must be of same sex. • Fraternal twins- Develops from two eggs, each fertilized by separate sperm cells. • Therefore, the babies may not look identical and could be of different sex. • Conjoined Twins - 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.

  35. Menstrual Cycle Mature egg develops and is released. Begins at puberty and ends at menopause. Hormones involved: FSH estrogen LH progesterone Stages involved in order: follicle stage  ovulation  corpus luteum menstruation

  36. Check your understanding and practice

  37. Lesson 4: Cloning and Reproductive technology Objective: To compare and contrast the technologies used to create new cells or organisms in vitro

  38. Selective breeding: • The process of breeding plants and animals for desirable traits.

  39. Cloning • A process which produces identical copies of a gene, cell, or an organism.

  40. Stem cells • An undifferentiated cell that can develop and become specialized into different cell types of the body.

  41. Transgenics The technique of inserting foreign DNA into plants and animals produces transgenic organisms.

  42. Check your understanding and practice

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