Transcript Key Idea #
Key Idea # 9 All organisms have a life span and must reproduce in order to continue the species. Reproduction allows the genetic material of living things to be passed from generation to generation is required for the survival of a species includes two types: – sexual – asexual Asexual Reproduction Advantages: only one parent is needed offspring are genetically identical to parent can produce large numbers of offspring Disadvantages: no genetic variety because offspring are genetically identical to the parent organisms are all identical so the species can’t adapt to a changing environment Types of asexual reproduction include: runners bulbs tubers budding binary fission fragmentation regeneration cloning FYI: Fragmentation and Regeneration A type of asexual reproduction found in less evolved animals. When the parent body breaks into pieces, each piece can grow into a new organism that is identical to the parent. http://images.google.com/imgres?imgurl=http://image.tutorvista.com/content/reproduction/planaria-regeneration.jpeg&imgrefurl=http://www.tutorvista.com/content/science/science-ii/reproduction/asexualreproduction.php&usg=__RTk4xJj77XukAzKY23f81XPmc1o=&h=371&w=415&sz=16&hl=en&start=28&um=1&itbs=1&tbnid=AO9LlKVsW0u0XM:&tbnh=112&tbnw=125&prev=/images%3Fq%3Dregeneration%2Band%2Bfragmentation%26ndsp%3D20%26hl%3Den%26sa%3DN% 26start%3D20%26um%3D1 http://web.mit.edu/neuro/planaria.html Sexual Reproduction Advantages: Genetic variety • organisms closely resemble their parents • both parents contribute an equal amount of genetic material to the offspring. Organisms have a greater chance of adapting to environmental changes Disadvantages: Two organisms must be involved Some genetic combinations can negatively affect the survival of some species by passing on diseases and genetic defects Some organisms reproduce in more than one way…… Yeast Reproduction Bacteria reproduce Asexually genetic material is duplicated before the cell divides resulting in two daughter cells that are genetically identical to each other. – Note: a disadvantage is antibiotics will kill all bacteria Sexually genetic material is transferred from one cell to another cell forming one new bacteria cell that is genetically different from the parent cells – Note: An advantage is antibiotic resistance in offspring. http://biology.about.com/od/bacteriology/a/aa080907a.htm Plants reproduce sexually through pollination and fertilization asexually through production of runners, tubers, regeneration, bulbs cloning, etc… What about fraternal and identical twins? Fraternal Twins are produced when two separate sperm cells fertilize two different egg cells by sexual reproduction. are not identical because they have different DNA (chromosomes and genes) http://www.womenshealth.gov/pregnancy/you-are-pregnant/twins-multiples.cfm Identical Twins are produced after one sperm cell fertilizes an egg cell by sexual reproduction and the fertilized egg divides into two fertilized egg cells by asexual reproduction. are identical because they have identical DNA (chromosomes and genes). http://www.womenshealth.gov/pregnancy/you-are-pregnant/twins-multiples.cfm Cell Division is the process by which a cell divides to form two identical daughter cells. Googleimages.com Cell Growth and Cell Division The daughter cells grow and increase in size until they reach maturity. Once the daughter cells reach maturity, they divide and produce two more daughter cells. This process continues, resulting in organism growth and reproduction of cells. Googleimages.com The Cell Cycle Each time cell division takes place, it’s called a cell cycle For unicellular organisms, a cell cycle results in a new organism – bacteria, amoeba, paramecium For multicellular organisms, a cell cycle results in a new cell – leaf cells, root cells, skin cells, blood cells, etc. The growth of a unicellular organism is limited to an increase in cell size. Pleodorina starrii Once unicellular organisms reach adulthood they divide. The 12 small cells near the top of this colony only swim. The 20 larger adult cells both swim and reproduce by cell division. http://www.sciencedaily.com/images/2009/02/090219140546-large.jpg (Credit: Copyright 2008 Matthew Herron) Bacteria are unicellular organisms without a nucleus will reproduce every 20 minutes under ideal conditions How do cells reproduce? Prokaryote cells like bacteria don’t have organelles and a nucleus to divide up, so they can divide by splitting themselves in two by binary fission. Eukaryote cells like animal and plant cells have organelles and a nucleus to divide so they must undergo mitosis. http://74.125.95.132/search?q=cache:-HB2ovA4l8J:teachers.henrico.k12.va.us/deeprun/chapman_j/unit05/cell_division.ppt+skin+cell+reproduction&cd=6&hl=en&ct=clnk&gl=us Binary Fission The cell duplicates its genetic material and then divides into two separate cells Mitosis produces two new daughter cells which are identical to each other and the original parent cell. produces body cells for growth, replacement, and repair Note: A similar type of cell division occurs in plant cells Googleimages.com FYI: Cell Replacement Bone marrow cells constantly divide to produce new red and white blood cells – RBC’s live about 100-120 days – WBC’s live about 13-20 days Skin cells under your epidermis constantly divide and move upward to replace lost skin cells that flake off. – Most people re-grow their epidermis completely about every two years. Kidshealth.org Are a child’s cells smaller or the same size as it’s parents'? You might think that the parents have larger cells, because their bodies are bigger. But the truth is, that both the infant, its parents, have cells that are pretty much the same size. However, the parents have a lot more cells. http://www.kidsbiology.com/biology_basics/index.php Growth of multi-cellular organisms is due to both an increase in cell size and an increase in cell number. http://schulen.eduhi.at/hsgunskirchen/hot_pot/English/More1/family_clipart.jpg Once cells in multi-celled organisms reach adulthood they divide (reproduce) and form two cells. Repeated cell division causes an increase in cell number in the organism. A larger multi-cellular organism has more cells than a smaller organism of the same species, but the cells are all pretty much the same size. http://www.microscopy-uk.org.uk/mag/imgaug99/whole.jpg http://anubis.ru.ac.za/Main/ANATOMY/celldiv.jpg FYI Meiosis: is a type of cell division that produces sex cells for reproduction produces 4 new daughter cells which only have half of the genes from the original parent cell. When these cells combine to produce offspring each contributes half the genes that a normal body cell contains Produces Body Cells Produces Reproductive Cells http://www.bio.georgiasouthern.edu/biohome/harvey/lect/images/comparison.gif Life Cycle of the Flowering Plant: Produces Plant Cells