Reproduction

1. Reproduction Science 9 Ms. Hayduk

2. Cells and Growth

3. Characteristics of Living Things • Growth • Obtain and use energy (breathing, eating) • Movement • Adaptation to their environment • Reproduction • Composed of cells

4. What are Cells? • Cells are living things. • They are basic unit of life. • All living things are made up of cells. It is important to know that cells are not organisms, because most cells cannot survive on their own (e.g. a skin cell dies if it is removed from your body).

5. Cell Theory • All living organisms are composed of one or more cells. • Cells are the basic units of structure and function in all organisms. • All cells come from previously existing cells. • The activity of an entire organism depends on the total activity of its independent cells.

6. Plant and Animal Cells • Plant and animal cells have different structure and organelles (“little organs”) because they make up very different organisms. • Plant cells are designed to support tall, immobile organisms that can make their own food from sunlight. • Animal cells need to be flexible, since animals move to look for food.

7. Plant and Animal Cells • Plants cells have a cell wall that makes the plant cells rigid and allows the plant to grow tall. • A very big vacuole (much bigger than in animals) also provides structure to plant cells by pushing on the cell wall, and gives a long-lasting supply of water to the plant. • Plant cells also have chloroplasts which make food from sunlight.

8. The Cell Cycle and Mitosis

9. Why Do Cells Reproduce? Healing and Tissue Repair • Cells may be damaged or die from injury to the organism or because they are old. • New cells replace dead or damaged cells. Reproduction of Organisms • When new organisms are created (babies), cells reproduce to create the new organism

10. Why Do Cells Reproduce? Growth • An organism can only get bigger if its cells increase in size or if new cells are created. • When cells are too big, it takes too long for nutrients to travel through the cell. Also, the DNA can’t handle all of the extra tasks needed for a cell that is too big. • Cell division changes one big cell into two smaller cells, which will be more efficient.

11. The Cell Cycle • Cells go through a series of phases in their life.

12. The Cell Cycle • Interphase is the “rest phase” of the cell. During this time, it does its normal job, grows and prepares to divide itself. • Mitosis is the name for the process of cell division. Within mitosis, there are four individual steps, where the nucleus of the cell divides into two new cells. • Cytokinesis occurs after the nucleus has duplicated; each new cell is fully formed.

13. Cell Type and the Cell Cycle • Different types of cells have different life spans because they have different functions. • e.g. Skin cells only live for 2-3 days, since they are simple cells, grow quickly and are easily damaged. Brain cells, however, live 30-50 years, because they are very complex and are well-protected from damage.

14. DNA and the Nucleus • The nucleus is the control centre of the cell. It is called this because it contains deoxyribonucleic acid, or DNA, which stores the cell’s genetic information. • DNA tells the cell what its job is, how fast it should grow and when it should reproduce.

15. Chromosomes • When the cell is preparing to reproduce, the DNA coils into a tightly-packed structure called a chromosome. • Different types of animals have different numbers of chromosomes. Humans have 23 pairs (46 chromosomes total).

16. Chromosomes

17. Interphase • In interphase, the chromosomes form identical copies of themselves. • They stay attached to their copy until the cell itself divides, making a shape that roughly resembles an “X”.

18. Mitosis Prophase • The chromosomes begin to condense themselves very tightly. • The nuclear membrane begins to dissolve and disappear. Metaphase • The double chromosomes line up along the “equator” of the cell in a very straight line.

19. Mitosis Anaphase • The double-stranded chromosomes are pulled apart so that one strand goes to each “pole” of the cell. Telophase • A nuclear membrane begins to form around each identical set of chromosomes. • The chromosomes lengthen and become less condensed.

20. Cytokinesis • The cytoplasm is divided to create two, identical daughter cells. In animal cells: • The cell membrane pinches in to divide the cytoplasm. In plant cells: • The cell wall forms between the two nuclei to divide the cytoplasm.

21. Important Points About Mitosis • The original cell is called the parent cell, and the new ones are called daughter cells. • Only two daughter cells are created, and they are genetically identical to the parent cell.

22. Haploid and Diploid Cells • For organisms with two parents, we call these cells diploid cells, because there is one set of chromosomes from the mother and another from the father. • All of our body cells except sperm and eggs are produced through mitosis, so they are all diploid cells. • Sperm and eggs are called haploid cells because they have half of the number of chromosomes that diploid cells.

23. Cancer and the Cell Cycle • Cancer is the term used when cell growth is out of control. Basically, cancer occurs when there is too much life. • Cancer cells spend very little time in interphase, because most of their time is spent in mitosis. They grow very quickly and reproduce at a very rapid rate.

24. Cancer and the Cell Cycle • Cancer cells also have gripping structures that allow them to “grab on” to other cells and tissues. • Cancer is caused by mutated cells, which can occur from a variety of sources.

25. Kingdoms of Organisms

26. Kingdoms of Organims • Plants • Animals • Mammals, reptiles, amphibians, bird, fish, insects • Protists • Mostly single-celled organisms that do not fit into other kingdoms (eukaryotes – nucleus) • Bacteria • Single-celled (prokaryotes – no nucleus) • Fungi

27. Asexual Reproduction

28. What is Asexual Reproduction? • Asexual reproduction is a way for organisms to reproduce without sex. • All of the offspring are created from one parent, and are genetically identical to each other (and to the parent). • Each of the offspring is called a clone.

29. Advantages of Asexual Reproduction • Produces lots of offspring very quickly • Produces offspring that are well-suited to the environment they are in, provided it stays the same • No energy used to find a mate

30. Disadvantages of Asexual Reproduction • No genetic variation • Species cannot adapt easily • Anything that harms the parent will also harm all of the offspring • Changes in environment might kill or harm the whole population

31. Binary Fission • Occurs when single-celled organisms divide into two identical daughter cells • It is very much like the process of mitosis, except that not all single-celled organisms have a nucleus, so sometimes it is a simpler process

32. Binary Fission in an Amoeba

33. Binary Fission in Bacteria

34. Budding • The parent produces a small bud (basically a tiny clone – like a baby!), which grows out of the parent and can eventually detach to be a completely new offspring • This happens in organisms like yeast, coral and sea sponges

35. Budding in Yeast

36. Parthenogenesis • Certain species of insects and some reptiles can reproduce from unfertilized eggs • These eggs develop into full organisms, but may be different or less complex than organisms of the species from fertilized eggs • For example, in bees, unfertilized eggs develop into worker drones (male) and fertilized eggs become female workers

37. Spores • Most fungi, green algae, some moulds and non-flowering plants reproduce by spores • A spore is a reproductive cell that grows into a new organism by mitosis • The process is like parthenogenesis, except that spores cannot be fertilized • Spores travel to a new place by water or wind, where they grow into a new organism

38. Spores from Bread Mould

39. Vegetative Reproduction • Occurs with plants • Many methods: • Plant cuttings (the cutting, in water, will grow roots which can be planted) • Runners (plant puts out shoots that grow along the ground – roots develop and new plants grow along the length of the runner) • Bulbs and tubers (new plants grow from pieces of the old bulb or organism)

40. Strawberry Runners

41. Fragmentation • Occurs when a new organism is created from a piece of an existing parent, and the parent continues to live • Some worms can be cut in half and each piece will regenerate into a whole worm • Starfish can also do this, if one arm is removed from the parent • New organisms are genetically identical to the parent

42. Grafting • A process for plants when one part of one plant is joined on to another plant • The two plants continue to grow as one plant, but their DNA does not change – so they look like separate plants

43. Grafting

44. Sexual Reproduction

45. What is Sexual Reproduction? • Sexual reproduction is the union of two sex cells • Sex cells, also called gametes, refers to egg (from females) and sperm (from males) • The union of the egg and sperm is called fertilization • Sexual reproduction occurs for most species of plants and animals, and generally involves two organisms

46. Advantages of Sexual Reproduction • The offspring of sexual reproduction have a combination of genes from both parents • Genetic diversity in a population allows the organisms to adapt and survive through disease and other dangers

47. Disadvantages of Sexual Reproduction • Takes more time and energy, so populations do not grow as quickly

48. Meiosis • Meiosis is a process of cell reproduction that produces gametes (haploid cells) • The first phase of meiosis is just like mitosis. The cells reproduce their chromosomes, then the cell divides, producing two daughter cells. • Then, the daughter cells each reproduce once more, producing cells with half of the number of chromosomes.

49. Basics of Sexual Reproduction • A male sex cell (sperm) and female sex cell (egg) join together to make a single cell called a zygote. • The zygote begins to undergo mitosis, growing, bigger. At this point it is called an embryo.

50. Meiosis • All of the cells produced have unique genetic material. • Every cell that undergoes meiosis produces either: • Four viable sperm • One viable egg and three non-viable eggs called polar bodies • The one egg produced takes most of the cytoplasm, making it a bigger cell than a sperm