Reproduction

1. Reproduction Asexual Sexual Mitosis and Meiosis

2. Reproduction • A species is a group of closely related organisms that share certain characteristics and produce new individuals. • For many species to survive past a single generation, reproduction is essential. All individuals eventually die, but a species continues because of reproduction.

3. When individuals reproduce, their offspring begin a period of development that ends in adulthood. Once an individual reaches adulthood, it is usually able to reproduce and continue the species for another generation. • Reproduction and development are necessary for the continuation of any species and the continuation of life.

4. Types of Reproduction: • Asexual • Sexual

5. 1. Asexual Reproduction: • Involves 1 parent • All single celled organisms • Examples: Amoeba, Paramecium, Bacteria • Some multicellular organisms • Examples: Some plants (spider plant, strawberries), hydras, earthworms, starfish • Genetically identical offspring • By the process of mitosis

6. Review Mitosis: • Mitosis: “My toe grows by Mitosis” • the division of the cell nucleus into 2

7. Mitosis Animation

9. Diagram of Mitosis

10. 2. Sexual Reproduction: • Involves 2 parents • Most multicellular organisms • Genetically different offspring • By the process of meiosis • Growth by mitosis

11. Asexual Reproduction: • All types of asexual reproduction produces offspring that are identical to their parents. • There are 5 types of asexual reproduction: • Binary fission • Budding • Sporulation • Regeneration • Vegetative Propagation

12. Binary fission • Simplest form of asexual reproduction • common in unicellular organisms • examples: paramecium, amoeba, bacteria • Mitosis • Equal distribution of nuclear materials and cytoplasm • End result: 2 new organisms (daughter cells) - identical contents • parent no longer exists • only difference is smaller in size

13. Mitosis

14. Budding • Parent divides into two daughter cells with unequal distribution of cytoplasm • The smaller cell is called the BUD. • Budding refers to the production of a multicellular outgrowth from the parent organism • parent organism = the original cells • the bud and the parent may detach from each other and live independently or may remain together to form a colony • Parent and offspring are not the same size in the end

15. Examples of organisms the reproduce by budding: • Hydra • yeast DJ is my buddy! Please excuse his big head!

16. Yeast

17. Hydra

18. Sporulation • Spores are produced by mitosis • Spores are specialized reproductive cells and are unicellular • They have a thick protective coat that keeps them safe when environmental conditions are unfavorable • They stay dormant until conditions become favorable for temperature and moisture and develop into a new individual

19. Examples: Bread mold, mushrooms

20. Regeneration • The development of an entirely new individual from part of the original by the process of mitosis • Also refers to the replacement of lost structures • Not usually the form of reproduction for organisms

21. The power of regeneration decreases as the organism becomes more complex. • The cells of multicellular organisms tend to be more differentiated. Differentiation is the process that transforms developing cells into specialized cells with different structures and functions. Ex: liver cell vs. brain cells

22. Lobsters and crabs regenerate claws (note: They can not regenerate an animal from the claw !

23. If a hydra is cut in half, each half will grow a new individual

24. A planarian can be cut into several pieces, each piece will grow into a complete worm

25. Star fish can develop from a single ray and a piece of the central disk

26. Mammals can regenerate some tissue • Example: Liver

27. Vegetative Propagation • Some multicellular organisms reproduce by this method • New organisms develop from root, stems, or leaves of the parent plant • Can occur in 2 ways: • Artificially (human influence) • naturally (runner, tubers, or bulbs)

28. 1. Artificial Vegetative Propagation: • Developed by farmers and gardeners that allow them to grow plants with desirable traits • Examples: spider plants, seedless orange tree

29. Advantages of Artificial Propagation: • New plants have the same make up as the parent • It takes less time to mature • Seedless fruit can be grown • Faster growth of fruit or nuts • Higher levels of fruit or nut production

30. A length of stem that includes lateral buds is cut from the parent plant and partially buried in soil or rooting mixture to take root. A piece of stem is cut from the parent plant and attached to another plant. A piece of lateral bud is cut from the parent plant and attached to another plant. Compare/Contrast Table Comparing Plant Propagation Methods Method Procedure Cuttings Grafting Budding

31. 2. Natural Vegetative Propagation: • Occur naturally without human intervention • Examples: runners, tubers, bulbs

33. What is Cloning? • A technique that accomplishes the same end results as asexual reproduction (Identical copies) • Clones are very common in asexual reproduction

34. How animals are cloned: • Nucleus of parent cell is removed • Nucleus is inserted into an egg cell in which the nucleus has been removed • Egg cell is implanted into body of female, where it develops • Result: Organism with not 50% of the genetic information from 1 parent, but 100% • The clone is 100% identical to the original parent (step 1)

36. Cloning has been accomplished in animals as complex as sheep and pigs

37. Scientists are also developing methods in which we can grow human body parts.

38. Human Reproduction and Development • Human reproduction and development are carried out by specialized organs. • The functions of these organs are regulated by factors such as gene expression, hormones, and the environment.

39. The reproductive cycle in both males and females is regulated by hormones such as testosterone, estrogen, and progesterone. The hormones are controlled by the endocrine system in humans.

40. In humans, as a in nearly all mammals, fertilization and development occur internally within the mother’s body. Reproductive organs in other mammals are similar in appearance and function. • Reproduction is absolutely essential to the continuation of the species. Without it, a species will cease to exist.

41. Note: Sex cells = gametes = egg or sperm

42. Male Reproductive System • The structures and functions of the male reproductive system, as in other mammals, are designed to do the following: 1. Production of gametes (Sperm) 2. Delivery of gametes

43. Testes: • male reproductive organ • produce sperm • develop with in abdominal cavity and descend to the scrotum • also referred to as gonads • produce sperm and testosterone • number = 2

44. The testes have clusters of tiny tubules called seminiferous (means seed bearing) tubules. They are tightly coiled and twisted together to form a compact organ. • The pituitary gland releases Follicle Stimulating Hormone (FSH) and Leutenizing Hormone (LH), which stimulates the testes to produce the male sex hormone testosterone. • Testosterone is responsible for the development of secondary sex characteristics that appears in males at puberty.

45. Male Secondary Sex Characteristics: A boy’s voice becomes deeper, he grows a beard and more body hair, his chest broadens, he may find it easier to develop large muscles. • He will continue to grow for several years after his female classmates have stopped growing.

46. FSH and testosterone stimulate the development of sperm. When large numbers of sperm have been produced in the testes, the development process of puberty is completed. • The reproductive system is now functional, meaning that the male can produce and release active sperm.

47. Sperm: • Sperm cells are haploid (1n) gametes produced via gametogenesis in the testes to form the haploid nuclei found in male sperm.

48. The sperm consists of the following: • Head: contains the highly condensed nucleous (DNA = genetic information from the male) • Midpiece: packed with mitochondria which produce energy for the sperm to move • Tail or flagella: propels the cell forward

50. Scrotum: • The scrotum is a sac like structure that holds the testes on the outside of the body. • It regulates the temperature of the testes by relaxing when the body is hot and contracting when the body is cold. • The testes remain in the scrotum, outside the body cavity, where the temperature is about 1-3° lower than the internal temperature of the body (37°C) Sperm development requires the lower body temperature.