3.1 Meiosis

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1 3.1 Meiosis

2 Chromosome Number Individuals of the same species have the same number of chromosomes. Meiosis is used to half the number of chromosomes passed to the offspring.

3 What is meiosis Meiosis happens only in cells producing gamettes (egg and sperm). It is sometimes called reduction division as it reduces the chromosome number by half.

4 Stages of Meiosis

5 Diploid Cells Diploid cells are cells with a complete number of chromosomes. Examples: hair cells, liver cells They are symbolized by 2n. Also known as somatic cells

6 Haploid Cells Haploid cells are cells with only half the number of chromosomes. Examples: sperm and eggs They are symbolized by n. Also known as gamettes

7 Homologous Chromosomes Pairs of corresponding chromosomes One is provided by each parent

8 Assignment P. 78 #1, 3, 6-9, Stages of Meiosis Diagram Mitosis vs Meiosis Table

9 Mitosis vs Meiosis Parent Cell Sister Chromatids #daughter cells #divisions #chromosomes in daughter cells Types of cells produced examples Mitosis Meiosis

10 Mitosis vs Meiosis Mitosis Parent Cell 2n 2n Sister Chromatids Meiosis Separate in anaphase Separate in anaphase II #daughter cells 2 4 #divisions 1 2 #chromosomes in daughter cells 2n Types of cells produced Diploid, somatic Haploid, sex cells examples Skin, nerve Egg, sperm n

11 3.2 Sexual Reproduction and Diversity

12 Fertilization Fertilization produces a diploid cell from two haploid cells Egg(n) + Sperm(n) > Zygote (2n)

13 Alleles Alleles are different forms of the same gene. They may be recessive or dominant. Both alleles must be recessive for the trait to be expressed.

14 Incomplete Dominance Incomplete dominance produces a mixture of traits. For example a white carnation and a red carnation produces a pink carnation

15 Codominance Codominance occurs when both alleles are expressed. For example roan coloured horses have two different hair colours

16 Sexual Reproduction and Diversity Sexual reproduction results in genetically different offspring. These differences allow the species to survive in changing environments. Individuals need a mate to produce offspring.

17 Asexual Reproduction Asexual reproduction requires only one parent. Reproduction occurs frequently. If the environment changes, offspring are affected like the parent. If the environment is good for the parent, it will be good for the offspring.

18 Assignment P. 82 #1, 2, 4, 5, 7-9

19 Comparing Sexual and Asexual Reproduction Asexual Reproduction Sexual Reproduction # parents # offspring Variety of offspring Speed of reproduction timing

20 Comparing Sexual and Asexual Reproduction Asexual Reproduction Sexual Reproduction # parents 1 2 # offspring many Few to many Variety of offspring No variety diverse Speed of reproduction timing fast slow Anytime once mature Only when mate available

21 3.3 Methods of Sexual Reproduction

22 Conjugation Two unicellular organisms (bacteria and protists) Appears differently for different species Results in increased diversity

23 Hermaphrodites Hermaphrodites are organisms with both male and female sex cells. They can mate with any other organism of their species, but not with themselves. Eg. Earth worms

24 Flowering Plants Pollen contains male gametes. The stigma receives pollen grain which travels to the ovary. Pollen is moved from the male to female structures through wind, insects, birds or mammals. Some plants pollinate themselves. The zygote develops into a seed in the ovary.

25 Internal Fertilization The sperm is deposited into the body of the female. Ex. Most terrestrial animals, some aquatic animals

26 External Fertilization Sperm and egg are united outside the body. Both gametes and young are vulnerable to environmental conditions and predators. Eg. Many aquatic animals.

27 Assignment Anatomy of Flower Diagram P. 87 #2-4, 6-9, 11, 13, 14

28 3.4 Development of the Zygote

29 Zygote Formed when the egg and sperm fuse. It is a single cell.

30 Embryo Developed from a zygote when cells divide

31 Seeds Formed when eggs become fertilized. Contains food for the developing embryo. Much of the worlds food comes from seeds in the form of rice, corn and wheat.

32 Seeds Dicot Monocot

33 Radical develops into the roots Epicotyl becomes the stem and leaves Hypocotyl pushes through the soil and protects epicotyl Cotyldons contain food. Endosperm contains food

34 Eggs Contain zygote, nutrients, mechanisms for protection (jelly, shell or case). Monotremes are mammals which lay eggs

35 Eggs

36 Amnion provides cushioning Yolk sac stores food Allantois holds wastes Chorion and allantois controls movement of gasses and wastes into and out of egg Albumen cushions embryo and is an additional source of food

37 Embryo develops in the mother All mammals except the spiny anteater and platypus Marsupials do not develop very long in the mother, but are born early and climb to the mother s pouch. For most mammals, a placenta develops around the fetus Fetus is attached to the mother by the umbilical cord Umbilical cord carries wastes out and nutrients into fetus.

38 Mammal Development

39 Assignment Tomato Plant Life Diagram P. 92 #2-6, 8, 10-13

40 3.5 Reproductive Technologies in Agriculture

41 Selective Breeding Plants or animals with desired traits are bred together After several generations, all the offspring have the desired traits

42 Artificial Vegetative Reproduction Individual cells from a desirable plant are placed in bottles with growth hormone and nutrients Once seedling develop roots, they are planted in soil

43 Grafting Attaching a branch from a desirable tree onto the trunk or branch of another tree Common for fruit trees

44 Artificial Insemination Sperm is collected from the male and inserted into the female Commonly used for domestic animals

45 In Vitro Fertilization Sperm and egg are collected Fertilization occurs in a lab (petri dish) Embryos can be inserted into a different female

46 Hatcheries Male and female fish ready to mate are caught Eggs and sperm are collected and mixed Fish hatch, fed and released

47 Recombinant DNA Combines genes from different individuals or species into a single molecule of DNA DNA can be used to produce certain characteristics or substances from organisms

48 Genetic Engineering Intentionally altering genes Food is modified to resist spoilage or disease, delay ripening or improve nutritional content

49 Assignment p. 97 #2, 7, 12, 14-17

50 Review Assignment p. 104 #1-11, 14-17, 21-24

Sexual Reproduction. Chapter 3 Sexual Reproduction BC Science Probe 9 pages

Sexual Reproduction. Chapter 3 Sexual Reproduction BC Science Probe 9 pages Sexual Reproduction Chapter 3 Sexual Reproduction BC Science Probe 9 pages 72-105 Why Sex? Textbook Read pages 74 77 Sexual Reproduction Is reproduction involving two parents Each parent contributes equal