Reproduction, Mitosis and Meiosis Spring 2012 All Living Things REPRODUCE… Without reproduction all living things would go EXTINCT… HOW DOES A LIVING ORGANISM REPRODUCE? Living things can reproduce in 2 different ways: SEXUALLY OR ASEXUALLY Similarities: Both types produce an offspring. Asexual reproduction - only one parent is needed for reproduction. Offspring clone of parent. Sexual Reproduction – Two parents are needed for reproduction. Offspring is different than parents. Asexual Reproduction: Definition: Only one parent is needed for reproduction. Offspring clone of parent. Sexual Reproduction Definition: Two parents are needed for reproduction to combine sex cells. Offspring is different than parents. 5 Types of Asexual Reproduction Binary Fission – simple cell division. Most unicellular organisms like bacteria and protists reproduce this way. KINGDOMS: Protists and bacteria 5 Types of Asexual Reproduction Budding – occurs in simple multi–celled animals and unicellular fungi, a small individual grows off the body of the adult. KINGDOM : ANIMALS Hydra, jellyfish, corals, sea anemone. FUNGI- yeast 5 Types of Asexual Reproduction Spores- Are reproductive cells that grow into new individuals when conditions are right. Some ferns and fungi reproduce this way. KINGDOM : Plants and Fungi 5 Types of Asexual Reproduction Fragmentation – Occurs in multi-cellular animals. Entire organisms grow from a piece of the adult. KINGDOM: ANIMALS EX: Worms and Starfish. 5 Types of Asexual Reproduction Vegetative Propagation – Cuttings from plants grow into new individuals, or new runners (root structures) are produced. KINGDOM: PLANT EX: Strawberry plants, monkey grass, potatoes. SEXUAL REPRODUCTION Most multi-cellular organisms reproduce this way, including KINGDOMS ANIMAL, PLANT and FUNGI . Sexual reproduction involves two sex cells. One sex cell is needed from each parent. The sex cells, also called gametes, are egg cells in the female and sperm cells in the male. How do Parent Compare to Offspring? Asexual Reproduction – Only involves one parent so offspring is a CLONE!! Sexual Reproduction – Two parents genes are combine to make a new organism. Different from parents SEXUAL REPRODUCTION: allows for variation. Sexual reproduction always involves the combining of 2 nuclei from 2 different sex cells. FERTILIZATION is the joining of egg and sperm. The cell (fertilized egg) that comes from fertilization is called the ZYGOTE. HOW DOES SEXUAL REPRODUCTION OCCUR? Sexual reproduction is simple the joining of the egg cell with the sperm cell. This can occur inside the body or even outside the body of animals. Female fish and amphibians lay their eggs and then the males spread their sperm over them. Plants join their egg and sperm by the help of the wind or other animals. The yellow pollen grains inside a flower are SPERM cells. The egg is found in the base of the flower. Insects or wind bring the pollen to the flower and then the sperm travels down to the egg. When egg and sperm join, it forms a SEED!!!!! Chromosomes Definition: The structure that DNA is organized in. They come in pairs, half from each parent. NUMBERS OF CHROMOSOMES VS COMPLEXITY The number of chromosomes in the cells of eukaryotes differs from one kind of organism to another and has NOTHING to do with the complexity of the organism. FOR EXAMPLE: Goldfish - 98 Wheat - 42 Human - 46 Potato - 48 Fruit fly - 8 A fern called Ophioglossum reticulatum has 1,260 chromosomes per cell, more than any other known organism. CHROMOSOME ARRANGEMENT All regular body cells have all the same parts in multi-cellular organisms and the same # of chromosomes. There are 46 chromosomes in human body cells. Chromosomes always come in pairs. There are 46 chromosomes for a total of 23 pairs. 22 of the pairs are similar. The 23rd pair is different. These are the sex chromosomes. CHROMOSOME ARRANGEMENT HUMAN BODY CELLS HAVE 46 CHROMOSOMES OR 23 PAIRS. Nerve cell Bone cell BULLFROG BODY CELLS HAVE 26 CHROMOSOMES OR 13 PAIR. FRUIT FLY BODY CELLS HAVE 8 CHROMOSOMES OR 4 PAIR. WHY ONLY ½ IN SEX CELLS??????? The sex cells (egg and sperm) are also called GAMETES. Sex cells only have ½ the number of chromosomes as body cells. So, when they unite it equals a full 46... They DO NOT have a full # of chromosomes Human sex cells would have Bullfrog gametes would have - 23 chromosomes 13 chromosomes Fruit fly egg and sperm would have - 4 chromosomes FERTILIZATION 23 CHROMOSOMES How many chromosomes will the human fetus have? FERTILIZATION 23 CHROMOSOMES 46 is correct!! Just as it is supposed to be. WHAT IF A MISTAKE HAPPENS DURING FERTILIZATION? The resulting zygote is called a mutation. Not all mutations are bad. There are several useful living things that are mutations. BUT All mutations have something WRONG with them. Good mutations are changes in a living organisms natural characteristics that benefit the organism and allows it to survive better in its changing environment. CAN MUTATIONS HAPPEN IN HUMANS? The boy on the right has DOWN’S SYNDROME. Remember that chromosomes are supposed to come in pairs. Down’s Syndrome is caused by having three chromosomes attached together where the 21st pair should be. Got 23 from one parent and 24 from the other. HAVE YOU EVER EATEN A TANGELO? A tangelo is a cross between an ORANGE. It has 20 chromomoses in its body cells so how many in the sex cells? 10 Tangelos are a HYBRID because it will end up with an odd number or chromosomes (23). It has NO SEEDS and cannot reproduce And a TANGERINE. It has 26 chromosomes in the body cells so how many in the sex cells? 13 WHAT IS A MULE? How many chromosomes will the body cell of a mule have? 63 is an odd number. Knowing that all chromosomes come in pairs makes this animal have one single chromosome by itself. This causes ALL mules to be sterile and not able to reproduce. Body cells – 60 chromosomes Sex cells – 30 chromosomes Body cells – 66 chromosmes Sex cells – 33 chromosomes A mule is a cross between a horse and a donkey. ADVANTAGES AND DISADVANTAGES OF ASEXUAL REPRODUCTION Advantages: 1. Quicker, no need to look for a mate. 2. Simpler to produce another just like yourself if you have desirable traits. Disadvantages: 1. No variation of traits, no individuality. 2. Offspring is a clone of the parent (can be bad if parent has undesirable traits. ADVANTAGES AND DISADVANTAGES OF SEXUAL REPRODUCTION Advantage: 1. Allows for individualism or variation. There will never be two just alike unless they are identical twins. TWO different genetic codes from 2 different parents results in variation in a species. For example, no two quarter horses, pine trees, blue whales, dogwoods or humans are exactly alike. (Good for “weeding” out bad genes. Disadvantages: 1. Takes more time (gestation). 2. More energy required to find a mate, etc. What is a Liger? Lions - 38 chromosomes Tigers - 38 chromosomes Sex Cells - ? Sex Cells - ? How many chromosomes do ligers have? Can they reproduce? Sometimes an egg will split into two separate parts soon after it is fertilized. This creates two embryos with the same DNA: IDENTICAL TWINS. Sometimes two eggs are fertilized at the same time. The two embryos are just like regular siblings except that they develop and are born at the same time. These are called FRATERNAL TWINS. Conjoined Twins: Two theories 1.“Fission theory“ - conjoined twins occur when a fertilized ovum (egg) begins to split into identical twins, but is somehow interrupted during the process and develops into two partially formed individuals who are stuck together. 2.“Fusion theory“ - twins become conjoined after the fertilized ovum intially splits into identical twins. HOW DOES A CELL REPRODUCE ITSELF? The process is called CELL REPRODUCTION Cell Reproduction S- imple cell division in which one cell divides into two Multi-cellular organism use cellular reproduction to produce more body cells for growth and repair. Unicellular organisms use cell reproduction to reproduce period. Mitosis: Definition: A type of cell division that results in two daughter cells that are exactly the same as the parent cell. Results in cells such as internal organs, skin, bones, blood, etc. OR a new organism (clone). Purpose of Mitosis: Multicellular: To produce new cells to repair and replace existing body cells. Unicellular: To produce a new individual through asexual reproduction. The Process of Mitosis a cell wants to make a duplicate of itself, it first must copy its DNA (part of a chromosome). The copies then must be separated & sorted into two sides of the cell. The cell then splits in two. Part of each parent is carried to the two new cells. Exact DNA is passed on to offspring. End Product of Mitosis Multicellular: Results in new body cells such as internal organs, skin, bones, blood, etc. Heart (Cardiac) Cells Liver Cells Bone Cells End Product of Mitosis Unicellular: a new individual that is a clone of the parent. Number of Chromosomes Total number of chromosomes is the same as the parent. Example: Yeast cells = 32 chromosomes… Since it reproduces asexually, each offspring will have 32 chromosomes from a single parent. Meiosis: Definition: A type of cell division that results in two daughter cells each with half the chromosome number of the parent cell. Results in SEX CELLS! Purpose of Meiosis Multicellular: to produce new SEX CELLS that can combine to form an offspring. End Product of Meiosis New sex cells with half the number of chromosomes as body cells. Number of Chromosomes Each sex cell will have HALF the number of chromosomes than body cells. For humans, each sex cell will have 23 chromosomes. So, in mitosis in humans (reproducing body cells), each new body cell will have the TOTAL 46 chromosomes!!!