Comparative Anatomy

Comparative Anatomy Chapters 27, 32, 34, 36, 39, 41, & 42

What IS an animal? • All animals are: • Members of Kingdom Animalia • Multicellular • Heterotrophs • Organisms that move about during part or all of their life cycles • Most animals are invertebrates

Variation in Animal Body Plans • Organization • All animals are multi-celled • The most ancient animal linages are just aggregates of cells (Phylum Poriferia) • All animals show “division of labor” in their cells • This leads to tissue formation

Variation in Animal Body Plans • Organization • Tissue formation begins in the embryo • In early evolutions (jellyfish and flatworms), there are two tissue layers (ectoderm and endoderm) • Later athird layer developed (mesoderm) • Allowed increased complexity • Most animals have organs derived from mesoderm

Variation in Animal Body Plans • Body Symmetry • Simplest animals are asymmetrical • Jelly fish and hydras have radial symmetry • Most animals have bilateral symmetry • Most bilateral animals have also undergone cephalization (process in which nerve cells become concentrated at the head end)

Variation in Animal Body Plans • Gut and Body Cavity • Most animals have an incomplete digestive system (gut) • The sac-like gut opens at the end • Cannot perform all the tasks of digestion simultaneously

Variation in Animal Body Plans • Gut and Body Cavity • The two lineages of bilateral animals differ in how their digestive system and coelom (body cavity lined by mesoderm) form • Protostomes: Animals in which the first opening that appears in the embryo becomes the mouth and the second becomes the anus • Deuterostomes: Animals in which the first opening that appears in the embryo becomes the anus and the second becomes the mouth

Variation in Animal Body Plans • Circulation • In small animals, nutrients diffuse through the body (ex. Flatworms, jellyfish) • Flatworms MUST stay flat so that nutrients can diffuse in

Variation in Animal Body Plans • Circulation • Diffusion doesn’t supply nutrients fast enough for large organisms • These animals have either an open or closed circulatory system • Open: Blood diffuses directly with tissues • Closed: Blood travels around in veins and arteries, diffusing to tissues through the vessel walls • Much faster; allows for larger organisms

Variation in Animal Body Plans • Segmentation • Many bilateral organisms are segmented (similar units are repeated along the length of the body) • Leads to specialization

Reflect… • What is an animal? • Pretend you are taking a quiz with the following essay question: • Explain how animal body plans vary, giving an example of each variation. (10 pts.) • What would you write?

Now… • Work on one of the following: • Worksheet packet • Article response • Re-writing and highlighting your notes • Flashcards

Comparison of Major Systems • It is important to understand how different organ systems function in different organisms • Important organ systems that we will study: • Gas exchange (respiratory) • Removes waste (excretory) • Transmit information (nervous) • Reproductive system

Gas Exchange • All animals move about at some point in their life cycle • Movement takes energy (in the form of a molecule called ATP) • The fastest and easiest way to get ATP is through aerobic respiration • This requires oxygen and gives off carbon dioxide • Animals must supply cells with oxygen and give off carbon dioxide waste

Gas Exchange • Respiration: Physiological process by which an animal exchanges oxygen and carbon dioxide with its environment • Depends on O2 and CO2’s tendency to diffuse down its concentration gradient

Gas Exchange • Gases enter and leave an animal’s internal environment at a respiratory surface (moist, thin layer) • Why is it moist? • Why is it thin?

Gas Exchange • Factors affecting diffusion rates: • Surface-to-volume ratio • Ventilation • Respiratory proteins

Gas Exchange in Invertebrates • Some don’t have respiratory organs • Integumentary exchange: Diffusion of gases across their outer body surface (integument) • Ex. Sponges, cnidarians, flatworms, and earthworms • Live in aquatic or damp environments (why?) • Tend to be flat and small or have thin layers • Assists in vertebrates with gills as well

Gas Exchange in Invertebrates • Invertebrate gills • Gills: Filamentous respiratory organs that increase the surface area available for gas exchange • Ex. Aquatic mollusks, some sea slugs, aquatic arthropods • Water flows into the body cavity and passes over gills where gas exchange occurs

Gas Exchange in Invertebrates • Snails that spend their lives on land have a lung instead of (or in addition to) gills • Lung: Sac-like respiratory organ • Branching tubes deliver air to a respiratory surface with many blood vessels • A pore allows air to enter and can be closed to conserve water

Gas Exchange in Invertebrates • Tracheal tubes and book lungs • Insects and arachnids have hard exoskeletons that provide protection but prevent gas exchange • Have a tracheal system (repeatedly branching, air-filled tubes reinforced with chitin) • Start with spiracles(small openings across the integument) that can be opened and closed to regulate air flow • Some pesticides clog spiracles

Gas Exchange in Invertebrates • Tracheal tubes and book lungs • Tracheal tubes end near body cells, where respiration takes place • Some organisms can force air in and out of the tracheal tubes (ex. Grasshoppers)

Gas Exchange in Invertebrates • Tracheal tubes and book lungs • Some spiders have book lungs (air and blood exchange gases across thin sheets of tissue) • Hemocyanin picks up oxygen and transports it to body tissues

Reflect… • Create a chart comparing and contrasting the forms of invertebrate respiration.

Gas Exchange in Vertebrates • Fish gills • All fishes have gill slits that open across their pharynx (throat region) • In jawless fishes the gills are visible from the outside • In bony fishes the gills are covered by gill slits • In all fishes, respiration occurs when water flows into the mouth, into the pharynx, and over the gills

Gas Exchange in Vertebrates • Fish gills • Jawless fishes actively suck water into their mouths and over their pharynx and force water out by contracting muscles that make the opening smaller

Gas Exchange in Vertebrates • Fish gills • Bony fishes have gill filaments with capillary beds • Blood in the capillary and water flow in opposite directions so the oxygen levels can never equalize (counter current exchange) • Why would this be important?

Gas Exchange in Vertebrates • Paired lungs evolved from outpouchings of the gut wall in some bony fishes • http://www.youtube.com/watch?v=EWGrMxKALzc • http://www.youtube.com/watch?v=WwgjW3AIJa4 • http://www.youtube.com/watch?v=oMPBukVALw0 • http://www.youtube.com/watch?v=WwgjW3AIJa4

Gas Exchange in Vertebrates • Gills would be useless on land • Without water, they would dry out and collapse • Lungs became more and more necessary as organisms spend more time outside of water

Gas Exchange in Vertebrates • Amphibians • Larvae have external gills • Gills disappear as they develop and are replaced with internal lungs • Integumentary exchange accounts for nearly all carbon dioxide leaving the body • Frogs draw air in by lowering the bottom of their mouth and push air out by raising it

Gas Exchange in Vertebrates • Amniotes (Reptiles, birds, mammals) • Have waterproof skin and no gills as adults • Have two well-developed lungs • Contraction of chest muscles pulls air into the lungs

Gas Exchange in Vertebrates • Reptiles and mammals • Respiration occurs in sacs at the ends of the smallest airways

Gas Exchange in Vertebrates • Birds • Have small inelastic lungs that don’t expand • Air sacs attached to lungs inflate and deflate • It takes TWO breaths to move air through the system • Air flows through tubes during inhalation AND exhalation • Tubes are covered in respiratory surfaces

Reflect… • Create a Venn Diagram comparing and contrasting vertebrate and invertebrate gas exchange. • Add vertebrate gas exchange to the comparison chart you made of invertebrate gas exchange

Fluid Regulation and Waste Removal • Vertebrates have a urinary system • Filters water and solutes from blood • Reclaims or excretes water and solutes as needed to maintain the volume and composition of the extracellular fluid • Kidneys filter blood

Fluid Regulation and Waste Removal • Invertebrates • Marine invertebrates the same fluid concentration as seawater (why would this be important?) • Sharks also have isotonic fluids with sea water

Fluid Regulation and Waste Removal • Fishes • Bony fishes have body fluids that are less salty than saltwater and more salty than freshwater • Marine fishes lose water across their bodies and their gills • To replace water, they gulp seawater and pump salt out through the gills • Produce small amount of concentrated urine

Fluid Regulation and Waste Removal • Fishes • Freshwater fishes continually gain water • Don’t drink water • Produce large volume of dilute urine • Loss of solutes is offset by solutes absorbed from the gut and pumped across the gills

Think about it… • What is the MAIN problem for fluid regulation in marine fishes and salt water fishes?

Comparative Anatomy