Biology 202 : Diversity of Life II
Review: Lectures 10-16
Lecture 10 & 11: Molluscs
- Significance: 1) Food (mussels, clams, squid , snails & scallops), 2) Intermidiated host
for parasites, 3) Ornamentation ( pearls), 4) Medical research ( giant squid axon ), 5)
Invasive species ( zebra mussels)
- Bivalvia , Gastropods, & Cephalopoda.
- General Features : Bilateral symmetry, protostomes with a schizocoelous coelom, 2 part
body ( head-foot & visceral mass), mantle ( with CaCO3 shell), Radula, diverse
- Can live in diverse conditions: Marine, freshwater and terrestrial habits.
- Digestion: uses radula to scrape foods off the substrate, can also abrade hard surfaces
- Open circulatory system with 2 chambered hearts ( Not as good at delivering O2 to
organs, only can generate low pressure) 2 chambered hearts = 1 chamber is stretchy
and good at taking in fluid, 2 chamber is more muscular and better at pumping blood to
- Body Plan Specializations: Torsion of the body ( rotation of the shell so that mantle cavity
and anus are now forward facing) & flattened foot ( often ciliated).
- Respiration: Some aquatic gastropods breathe across skin, some have gills ( within
mantle cavity) and land snails possess lungs ( with reduced or eliminated gills) .
- Endosymbiosis: Select gastropods show intriguing abilities to consume and rely upon
other organisms, cells and organelles. ( One takes on chloroplasts and can use those
- Environmental Tolerance : Remarkable tolerance to environmental stressers
( dehydration), they strongly reduce their metabolic rate( lipid oxidation for energy) and
adapt methods of water retention ( including physical , cocoons , and metabolic ,
urea/uric acid accumulation.)
- Body Plan: laterally compressed ( shells ( also called valves ) are on the sides.
- Circulation & Respiration : open circulatory system , 2 auricles, 1 ventricle. Gills
protected in mantle cavity , with water directed over the surface by siphons. - Digestion: no radula, filter feeders to remove particulates from water flowing over gills
( one siphon faces into current to let water in , and one the opposite direction for exhaust
- Adductor muscles have a specialized muscle protein that allows the muscle to remain
contracted without expending any extra energy.
- Mantle is filled with glycogen , and the rest of the body mass is mostly made up of lipids,
used as food storages for when they have to remain closed for a long time.
- Locomotion & musculature: most use foot to dig, flip or walk but some can use jet
propulsion. Muscle include adductors, to close the shell quickly, and catch muscles to
keep it closed.
- Environmental Tolerance: able to survive, anoxia( high levels of glycogen in blood allows
for glycolysis without oxygen), osmotic stress ( produce or breakdown organi solutes in
an effort to control osmolarity of their tissues and cells) and freezing ( can be freeze-
tolerant, producing cryprptectants)
- As food: very common food, but pose issues due to bacterial contamination, pesticide
bioaccumulation and PSP ( paralytic shellfish poisoning)
- Body Plan: Most complex molluscs with tentacles reduced or absent shell. ( except
- Feeding and Digestion: Active predators with jaws and radula.
- Locomotion : slow movement uses fins and tentacles, rapid movement uses jet
- Nervous System : large brains … visual predators, eyes are superficially similar to
vertebrate eyes, cryptic coloration under neuronal control.
Lecture 12: Anthropods
- Diverstiy: Present in wide range of environments , were among first animals to invade
land ( and did so twice or three times independently), Sublime adaptive innovations for
a terrestrial life
- Importance: Pollination ( bees, lepidopterans) , Food ( for humans and other species),
Disease Vectors, Pests of Agriculture, Pest management, Model Organims.
- Body Plan: Metamerism and Tagmatization, Coelom reduced to cavity around gonads,
Chitinous exoskeleton ( support for muscle attachment, prevents desiccation and
provides protection), Growth facilitated by ecdysis ( Molting) , paired jointed
appendages. - Hinges and seams formed to allow motion to occur without breaking the exoskeleton,
these are not joints like in human bodies, but segments when the shell can bend.
- Cuticle separates from epithelial cells ( hypodermis), New cuticle synthesized expansion
helps break the old cuticle allow the animal to escape.
- Metamorphosis: Seperates from old exoskeleton, synthesize new exoskeleton, aids in
dispersal. Quantum jumps in size ( not continuous growth)
- Adaption to different resources and microhabitats during different stages of life.
- General Features: Ventral Nervous system, open circulatory system with blood draining
into sinus, breathes by gills( aquatic) book lungs ( awuatic /terrestrial) or
tachaeae(terrestrial), nitrogenous waste excreation depends on habitat, NH3 for aquatic
uric acid for land.
- Trilobites: All extinct, used to have oval flattened bodies, 3 segments, and lobed
- Carnivorous ( with poison glands and fangs ), One or more pairs of eyes and a variety of
other sensory structures, excretion via coxal glands or Malpighian tubules, relatively
impermeable exoskeleton, most are dioecious and oviparous
- Repiration: Book lungs = mediate countercurrent exchange of O2 and CO2 between air
and blood, Trachea = tubes running form the surface inward to deliver air deep to tissues
- Acarina: Many disease caused by ticks and mites
- Fusion of sensory and feeding tagamata: cephalothorax. Cephalization: - esophageal
ganglia Supra – regulates sensory , Sub – regulates locomotion, Giant neurons trigger
escape response, endocrine glads control metabolism, growth, ecdysis, and
- Brine Shrimp: Live in hypersaline lakes, when conditions deteriorate the females create
eggs with thickened walls ( cyst) , with low metabolic rates allowing them to survive for
years. When the adults emerge they undergo a mating frenzy for a short period of time
- Daphnia: Phenotypic plasticity in response to predators, they can grow spikes if copepod
predators are abundant( too make them too big to swallow).
- Barnacles: Adults are sessile , living attached to the “bottom”. Inhabit intertidal zone,
surving prolonged air exposure, monecious
- Copepods: Sea lice are parasitic, they live attached to the side of fish feeding on
mucous , epidermis , & blood. Major pest in aquatic agriculture. Lecture 13 & 14: Insects
- Myriapods and insects are terrestrial anthropods that invaded land . 450 mya, Some
insects secondarily returned to water. They all share – uniramous limbs trachea for
breathing and Malpighian tubules for excretion.
- Myriapod Diversity: Many impressive defence mechanisms: millipede repugnatorial
glands secrete cyanide, centipedes have ve