Grazing, Pollution, and Evolution c. They hatched the eggs and tested their abilities to eat the toxic cyanobacteria. Daphnia swimming amid toxic cyanobacteria in Lake Constance b. Nelson Hairston et al. collected Daphnia eggs in a state of diapause from the sediments, layer by layer a. pollution over the past 30 years has caused a proliferation of toxic cyanobacteria in Lake Constance
B. Filter Feeding aquatic animals, sessile benthic invertebrates: sponges, barnacles, polychaete worms, bivalves, etc. constant flow of water through organism – constant supply of microbes suspended in the water column microorganisms filtered through gills, tentacles, mucous nets microbes are autotrophs, heterotrophs, detritus sea squirts (tunicates, ascidians) and bivalves can capture particles as small as viruses
tunicates, so named because the outer layer of the body wall is a tough "tunic", made of a substance that is almost identical to cellulose animal consists of a double sac with two siphons: Sea water is pumped slowly (by cilia) through one siphon, sieved through the inner sac for plankton and organic detritus, and the filtered seawater is pumped out again through the second siphon, the atrium. Ascidian Tunicates are called sea squirts because when taken out of the water they squirt the water inside their body with force through the atrium
cellulose monomer animal biomass III. Cellulose digestion – key process in animal/microbe mutualisms cellulose – most abundant carbohydrate in the biosphere – chain of glucose molecules linked together – most animals can’t degrade it – rely on cellulolytic microorganisms microbial biomass degradation products 1. coprophagous and detritivorous animals (above) 2. animals that cultivate microbes externally 3. intestinal symbionts
IV. Cultivation of Microorganisms (External), plant-eating insects: A. leaf-cutting ants mutualism – ants – excavate cavity in soil bring leaves to fungus inoculate leaves w/fungus fungus grows by decomposing cellulose ants eat fungus cellulose --> fungal biomass --> ant biomass also, when ants eat fungi, the acquire cellulase, so they are able to continue degrading cellulose in their guts, using enzyme produced by the fungus obligate mutualism fungal garden breaks down without ants ants protect fungus from competitors fungus requires ants for dispersal ants require fungus for food
<ul><li>Stomata sunken in pits creates local humidity/decreases exposure to air currents; </li></ul><ul><li>Presence of hairs creates local humidity next to leaf/decreases exposure to air currents by reducing flow around stomata; </li></ul><ul><li>Thick waxy cuticle makes more waterproof impermeable to water; </li></ul>Xerophytes possess some or all of these adaptations to prevent excessive water loss
Xerophytes possess some or all of these adaptations to prevent excessive water loss cont. <ul><li>Stomata on inside of rolled leaf creates local humidity/decreases exposure to air currents because water vapour evaporates into air space rather than atmosphere e.g. British Marram grass </li></ul><ul><li>Fewer stomata decreases transpiration as this is where water is lost; </li></ul>
Xerophyte adaptations summary: Adaptation How it works Example thick cuticle stops uncontrolled evaporation through leaf cells small leaf surface area less surface area for evaporation conifer needles, cactus spines low stomata density smaller surface area for diffusion sunken stomata maintains humid air around stomata marram grass, cacti stomatal hairs (trichores) maintains humid air around stomata marram grass, couch grass rolled leaves maintains humid air around stomata marram grass, extensive roots maximise water uptake cacti
Left and right Epidermis of the cactus Rhipsalis dissimilis . Left: View of the epidermis surface. The crater-shaped depressions with a guard cell each at their base can be seen. Right: X-section through the epidermis & underlying tissues. The guard cells are countersunk, the cuticle is thickened. These are classic xerophyte adaptations.
Transverse Section Through Leaf of Xerophytic Plant
Marram grass possesses: rolled leaves , leaf hairs and sunken stomata . These adaptations make it resistant to dry conditions and of course sand-dunes which drain very quickly retain very little water.