Invertebrate anatomy and physiology Aka: invertebrate form and function

Invertebrate physiology: Skeletons Three kinds of skeletons are seen in Invertebrates Hydrostatic –Muscles surround and are supported by a water filled cavity –No hard structures for muscles to pull against –Diagram on page 814

Invertebrate physiology: Skeletons Exoskeleton –External skeleton, muscles are attached to the inside (page 815) –Arthropods are the best examples –Made of the carbohydrate chitin (remember from fungus) –All exoskeletons are thin a flexible at the joints –Advantage: very adaptable, very strong –Disadvantage: in order to grow the anima has to molt

Invertebrate physiology: Skeletons Endoskeleton (page 815) –Located inside the body –Present in sponges and echinoderms –Vertebrate are the best examples

Invertebrate physiology: Digestion Two strategies: –Digestion inside cells and digestion outside cells –Diagrams on page 784. Inside cells: –1) Intracellular digestion –In sponges, cells filter particles of food in the water, digestion occurs inside the cell, digested products transported to other cells –2) Gastovascular cavity digestion (seen in cnidarians and flatworms) –Food goes into a digestive cavity with only one opening to the outside, food broken down in the cavity, smallest particles taken into the cell, waste eliminated through the opening Outside cells: –Tube within a tube plan, food enters a mouth and exits an anus –Food is digested inside this digestive tract; digested food is adsorbed into the cells

Invertebrate physiology: Internal transport Two kinds of circulatory systems –1) Open circulatory system –2) Closed circulatory system Open circulatory system –Blood from the heart is not contained inside blood vessels –Example: insects –Blood contacts all the tissues of the body Closed circulatory system –Blood is contained in a system of closed vessels that pass through various parts of the body and return to the heart –Example: earthworms (diagram on page 792) –Provides more rapid and efficient control of blood flow

Invertebrate physiology: Respiration Two physiology problems: –Surface area needs to be large enough so that gas exchange by diffusion is adequate to support the animal –Gas exchange surfaces must be kept wet because gas exchange happens by diffusion only across wet membranes –Diagrams on page Adaptations –Worms respire through their skin –Crustaceans have gills –Spiders have book lungs –Insects have trachea (tubes that carry oxygen to each cell)

Invertebrate physiology: Excretion Purpose is elimination of toxic waste Closely related to control of water loss –Breakdown of amino acids produces ammonia, which is water-soluble –Elimination of ammonia means losing water –Salt-water animals eliminate ammonia by diffusion into the water –Freshwater flatworms have specialized cells Flame Cells to remove excess water (why??, remember osmosis) and ammonia –Annelids, mollusks, invertebrate chordates have specialized organs to remove ammonia from water, eliminate the ammonia in urine and return most of the water to the organism –Land invertebrates convert ammonia to urea, which can be made more concentrated than ammonia, but is still soluble in water –Insects and some spiders convert ammonia into uric acid, which is removed by organs called Malpighian tubules. Uric acid is excreted as a solid waste. This system conserves the most water.

Invertebrate physiology: Response Specialized cells for response to the environment are called nerve cells No matter what the animal, nerve cells look and function pretty much the same Primitive invertebrate have nets of nerves distributed throughout the body Two advances in development of nervous systems: –Some jellyfishes show Centralization where nerve cells are concentrated into a system around certain organs like the mouth –Clumps of nerve cells are called ganglia. Ganglia located near the head result in Cephalization, gathering nerve cells in the front of the organism where the animal first senses its environment. –Insects and mollusks show development of ganglia into brains –Nervous system development coincides with the development of specialized sensory cells like eyes.

Invertebrate physiology: Reproduction All invertebrates are capable of sexual reproduction Creates and helps maintain genetic diversity