ANIMAL UNIT (DIVERSITY FINAL)

• Steps of Urchin Gastrulation

  1. Vegetal Pole Invaginates
  2. becomes archenteron (primitive gut)
  3. 2. Archenteron Elongates
  4. mesenchyme cells contract
  5. 3. The Mouth forms where the primitive gut meets the ectoderm
• Key details: MODERATE amount of yolk

  1. cells will become increasingly smaller in the animal hemisphere
  2. cells are large in the vegetal hemisphere
  3. 2. Invagination in grey crescent forms the blastophore (primitive mouth/anus)
  4. 3. Blastomere cells in the animal pole move over the dorsal lip and push into the blastocoel (fluid cavity)
  5. 4. Endoderm and mesoderm form like this:
  6. cells in the animal hemisphere divide faster and move around the vegetal
  7. cells move INWARD
• Key details: LARGE amount of yolk

  1. The blastodisc (contains female sex cell) forms on top of the yolk
  2. The blastopore becomes the primitive streak (a groove with Hensen's node at the anterior)
  3. Ectoderm cells move inwards through the primitive streak
  4. forms endoderm/mesoderm
  5. displaces the hypoblast (creates bilateral symmetry and axes)
  6. in placental mammals, the hypoblast will become the placenta
• Formation of Coelom

  1. Mesoderm forms from the out-pouching of primitive gut (DEUTEROSOMES)
  2. Indiv. blastomeres create specialized tissues and the mesoderm forms from all of the cell divisions (PROTOSOMES)
  3. Interactions between germ layers will shape morphogenesis of animal
• Ectoderm

  1. Outermost germ layer
  2. epidermis, hair, claws, sweat glands, pigment cells
  3. in the brain and nervous system
• Endoderm

  1. Innermost germ layer
  2. lining of associated organs (ex. digestive tract)
  3. lungs, liver, gall bladder, pancreas
• Mesoderm

  1. Middle germ layer
  2. Urogenital system, muscles, bones
  3. Notochord, heart, blood vessels
• Where is Hensen's node?

  At the anterior end of the primitive streak
• Water & the salts dissolved in water


  Na+ & Cl- in the tissue/body fluids of the animal and the immediate environment of its cells, which is the animal's internal environment
• Aqueous solutions


  • Osmotic pressure, concentration of solutes, determine direction of osmotic water movement, isosmotic, hyperosmotic, hypoosmotic, ionic composition, volume
• Freshwater animal & its environment


  Hyperosmotic to fresh water, ion concentration in plasma & fluid are higher, must void water gained - dilute urine produced, Na+ & Cl- diffuse into environment, must replace lost ions - active transport cells in gills
• Ocean invertebrates


  Isosmotic to seawater, body fluids & ocean ~1 Osm, little need to expend energy, little need to correct gains/loses of water & ions
• Ocean bony fishes


  Hypoosmotic to seawater, body fluids more dilute (0.3 - 0.5 Osm), tendency to lose water - dehydration potential, tendency to gain ions - fluids become too concentrated, solutions: drink water, pump ions out of seawater during absorption, energy used to excrete ions - specialized cells in gill membranes, mitochondria-rich cells or chloride cells
• When colonizing freshwater


  Body fluid Osm > freshwater Osm, much energy needed
• When some fishes invaded land


  Gave rise to terrestrial vertebrates, Osm of land vertebrates ~0.3 Osm (e.g. human blood)
• When some fishes reinvaded oceans


  Gave rise to virtually all bony fishes alive today, explains osmolarity of ocean fish body fluids - hypoosmotic, explains why ocean fishes are no isosmotic
• Air-breathing ocean vertebrates


  Descended from terrestrial vertebrates, similar body fluid Osm, obtain substantial salt load (~3x saltier!), salt glands evolved to support excess salt removal, ATP needed
• Salt glands


  Located in head, secrete highly concentrated salt solution, sea birds - nostrils, sea turtles - tears, ocean lizards - often nostrils
• Migrations


  Switch between hyperosmotic regulator & hypoosmotic regulator, mostly controlled by hormones, function like freshwater fish in freshwater, function like saltwater fish in saltwater
• Brackish water


  Interface between ocean & freshwater sources, variable salinity - can change based weather patterns, invertebrates - many near coastlines are osmotic conformers, body fluid Osm varies with seawater, can be stressful, some inverts near coastlines are osmotic regulators - maintain steady body fluid Osm
• Mammalian excretory system


  Primary organ - kidneys, functional unit - nephron, filters blood, modifies filtrate, removes components, adds components
• Nephron function


  Glomerulus - blood capillary ball, increased bp - filtration of blood, Bowman's capsule - collects filtrate, proximal convoluted tubule - reabsorption of needed nutrients, loop of Henle - urine concentration, distal convoluted tubule - urine concentration, buffer system, collecting duct - urine concentration
• Nephron types


  Cortical - short loops, juxtamedullary - longer loops, corpuscle near medulla - glomerulus & Bowman's capsule, more urine concentration, deeper into medulla - more ECF solutes, more ECF - more water leaving tubules
• Kangaroo rat distribution, diet, water adaptations
• Behavior


  Controlled by the Nervous System
• Behaviors


  Play central roles in interactions with each other & environment
• Proximate causes


  Immediate, mechanistic causes of a process
• Ultimate causes


  Larger-scale causes, e.g. causes that led a process to evolve
• Herring Gulls (Larus argentatus)


  • Red dot on bill
  • Return to nest
  • Nestlings peck dot
  • Stimulates regurgitation of food in adult
• Proximate vs ultimate causes of the feeding behavior in Herring Gulls?
• One cannot predict the other between proximate and ultimate causes
• Fixed action patterns


  Behavior expressed without prior learning (innate), often resistant to modification, present in healthy nervous systems
• Fixed action patterns


  • Bill pecking
  • Spider web-making
• Behaviors evolve because the nervous system allows for behavior, and genes encode tissues that can evolve
• Behaviors that have evolved


  • Reduction of spontaneous activity in Drosophila melanogaster due to "clock" mutations
  • Nest building patterns in Mus musculus varying by geographic location
• Biological determinism


  Attributes determined by genetic inheritance, genes -> neural tissue -> behavior
• Behavior is not simplistically deterministic, as more complex nervous systems allow for more flexible behavior that can be modified by learning and epigenetic effects
• Behavioral evolution


  Depends on evolution of functional systems
• Functional systems that influence behavior


  • Insect navigation using polarized light
  • Pronghorn running behavior and muscle evolution
• Natural selection favors the evolution of learning abilities, as specific details of an individual's life cannot be predicted or inherited