Transcript Development
Development Links - Biology Components of Development Growth- The process of a multicellular Differentiation- The process of cells in increasing its number of cells, becoming larger. (i.e. zygote to an adult) a multicellular organism (initially all alike) becoming different from each other generating the various tissues (i.e. nerve, muscle, skin and bone, etc.) necessary to be a functional adult . Thoughts on development: Growth Cells generating more cells (Mitosis and Cytokinesis) A single cell has size limits, therefore for organisms to become larger they must be multicellular. All cells of an organism have a complete set of DNA to make the entire organism. Cell death, as well as cell growth must occur for proper development Connected to the cell cycle. Mitosis and Cytokinesis Cell cycle Phases of Mitosis Interphase Prophase Metaphase Anaphase Telophase Animation link(s) http://science.nhmccd.edu/biol/mitosis/pmitosis.html http://www.lewport.wnyric.org/jwanamaker/animations/mitosis .html http://www.sci.sdsu.edu/multimedia/mitosis/mitosis_qt1.html Interphase Prophase Metaphase Anaphase Telophase Thoughts on development: Differentiation What if your entire body was made of only stem cells? Muscle cells? Nerve cells? Do different types of cells (tissue) perform different jobs in a multicellular organism? If all of the organisms cells are genetically Identical, how do they become different types of cells (tissue)? Epithelial and Connective Nerve and Muscle OKAY??????? But how does an organism get all of these cell (tissue) types? Historical perspective The “Homunculus” Theory = A fully formed person, just very tiny, exists in the head of a sperm cell. The egg makes no contribution except to function as an incubator. No differentiation necessary!!!!!!!!!! We now know better. Embryonic differentiation: Zygotes Early embryonic development Blastula Gastrulation It is not birth, marriage, or death, but gastrulation, which is truly the most important time in your life." Lewis Wolpert (1986) Embryonic cell (tissue) types As embryo’s develop to the gastrulation stage they form three basic types of tissue which differentiate into all other tissues: Endoderm Mesoderm Ectoderm These basic tissues become: OKAY ?? But how do we get to become these tissues from embryonic stem cells? Influences on differentiation (switching genes on and off) Environmental influences both inside the cell and outside the cell can cause certain genes to switch on or off at appropriate or inappropriate times. Inside the cell- differential distribution of materials during cell division can cause cells to develop differently. Outside the cell- chemical communication with nearby cells may influence development based on strength of signal. Induction- is a special type of outside influence. (Leads to Cell Differentiation) ??????????? (good field for a career) Induction!!! Apoptosis (cell death) at the appropriate time is also very vital to development. What next? Development sometimes messes up! Cancer- one’s own cells fail to stop reproducing when they should. Birth defects- environmental factors + genetics cause misinformation during development. Key Development terms Zygote Blastula Gastrulation Growth Cytokinesis Mitosis interphase prophase metaphase anaphase telophase Differentiation Senescence Cell cycle DNA Induction Cancer Metastasis Birth defects Mutation Final thoughts Development must occur at the correct times and correct places in the embryo. Animal development occurs in consistent patterns. Plants go through similar development. Cell deaths must also occur at appropriate times. Development is a zygote to death process. Developmental errors often cause spontaneous abortions (miscarriage) Environmental factors can greatly influence development (especially during very early development). Development = growth + differentiation. We still have a lot to learn about development.