BIO 311D 2nd Edition Lecture 22 Outline of Last Lecture I Animal cells tissues body plans II Hox genes Outline of Current Lecture I Animal Development and Hox genes II A look at the classes of vertebrates III What is homeostasis Current Lecture I Animal Development and Hox genes A Hox genes Helps control the expression formation of body forms Multi gene family Expressed along the anterior posterior axis of the embryo in the same order as their arrangement between the 3 end and the 5 end If one of the genes is mutated along the way you ll see the lack of the structure of the gene the spread of influence of the hox gene continues from the anterior to posterior end IClicker the absence of gene D gene B continues C A mutation in the Ubx homeotic gene resulted in a protein that inhibits leg formation in this lineage of arthropods Influence of hox genes insect wing the vertebrate of the chicken difference between a fin and a paw IClicker two groups of animals that are relatively closely related but in different families such as dogs and cats would be expected to have Similar hox genes but differential hox gene expression patterns B Animal Development Larger animals have internal surfaces for exchange of substances Cell blood blood external surface Exchange surfaces are finely branched to permit maximum transport across cell membranes Diffusion a limiting factor Four tissue types 1 Epithelial cells in layers on a basilar membrane for transport secretion and protection II III 2 Connective cells in a non cellular matrix blood bone cartilage fibrous connective 3 Muscle smooth striated cardiac 4 Nerve Elements of the cytoskeleton holds the cell shape C Describe some specializations cell shape which organelles abundant cell cell junctions found in these cells Sperm a lot of mitochondria to produce energy for movement flagella haploid nucleus membrane proteins Small intestine transport epithelium specialized for taking up digested foods a lot of surface area to absorb all the food layers membrane proteins transport proteins Pancreatic secretory epithelium produces and secretes insulin a lot of rough ER Macrophage large white blood cell engulfs and breaks down particles a lot of lysosomes moving cytoskeleton nothing anchoring amoeba movement no cilia or flagella Heart muscle communicates immediately with neighbors when one pulls all move gap junctions desmosomes mitochondria for energy Classes of Vertebrates A Arthopods jointed legs and exoskeleton three classes 1 Arachnids two body segments head and thorax 8 legs spiders and scorpions 2 Crustaceans multiple pairs of appendages specialized for different functions crab shrimps 3 Insects 6 legs B Jawless Fishes no jaw they suck because they can t chew Jaws C Cartilaginous Fishes a cartilaginous skeleton i e sharks D Bony Fishes bony skeleton Tetrapod body form better on land E Amphibia smooth moist skin gas exchanges Aminiotic Egg F Reptiles scaly skin cannot have gas exchange over the surface of their body G Birds Reptilian ancestry Homeostasis A The concept of homeostasis maintaining a parameter in a steady state condition around a set point B Hormones pH
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