1. Anatomy and Physiology in Invertebrates

2. Support and Movement
Almost all animals have muscle-like tissue for movement
Three types of skeletons:
Hydrostatic skeleton
Exoskeleton
Endoskeleton

3. Hydrostatic Skeleton Muscles supported by a water-filled body cavity
No hard structures for muscles to pull against
Push against the water in the body cavity
Cnidarians, flatworms, nematodes, mollusks, annelids

4. Exoskeleton External skeleton, muscles attached inside
Arthropods have exoskeletons made of chitin
Exoskeletons are thin and flexible at joints, allowing for flexion and extension
Very adaptable, very strong
Drawbacks are that the animal must shed it and grow a new one as it gets larger, and it is heavy

5. Endoskeleton Present in sponges and echinoderms (also in vertebrates)
Internal skeleton

6. Feeding and Digestion
Intracellular digestion vs extracellular digestion
Sponges filter food particles from the water and digestion is intracellular with nutrients being distributed among cells

7. Feeding and Digestion
Cnidarians and flatworms have a gastrovascular cavity
Digestive sac with a single opening – food enters, wastes leave
Food particles broken down into smaller pieces, then are taken up by cells lining the cavity and digestion is intracellular

8. Feeding and Digestion
Extracellular digestion takes place in annelids, mollusks, arthropods, invertebrate chordates
Tube within a tube digestive system – food enters through mouth and leaves through anus, digestive tract forms a separate tube within the body
Food is digested extracellulary in digestive tract and nutrients are absorbed

9. Internal Transport
Constant supply of oxygen and nutrients necessary for survival
Carbon dioxide and posionous wastes need to be eliminated
Invertebrates like sponges, cnidarians, flatworms, and nematodes do not have circulatory systems – all done by diffusion

10. Internal Transport
More complex invertebrates (and vertebrates) have circulatory systems, which include one or more pumps and tubes that move things around within the body
Open and closed circulatory systems

11. Open Circulatory System
Blood from heart is not entirely contained within blood vessels
Heart pumps blood through a series of vessels, and it is released directly onto body tissues
Flows through tissues and is collected in sinuses, eventually flowing back to heart
Seen in some types of mollusks (clams, oysters), arthropods, echinoderms

12. Closed Circulatory System
Blood contained within a system of closed vessels that pass through various parts of the body and return to the heart
Blood does not come in direct contact with tissues – more rapid and efficient
Seen in some mollusks (squids, octopuses), and annelids

13. Respiration (gas exchange)
Small soft-bodied invertebrates exchange oxygen and carbon dioxide by diffusion through body surfaces
Two respiratory problems:
Respiratory system must have large surface area to allow for enough gas exchange to support organism’s demands
Surface of organs must be kept wet because diffusion can only take place across moist membranes

14. Respiration (gas exchange)
Animals that live in water do not have these problems (sponges, cnidarians, flatworms, nematodes, echinoderms)
Mollusks and crustaceans have gills, which are rich in blood vessels and provide a large surface area for gas exchange

15. Respiration (gas exchange)
Terrestrial invertebrates have special organs for breathing air
Spiders have book lungs – sheet-like layers of thin tissue that contain blood vessels
Insects have trachea – tubes that bring air to each body cell

16. Excretion (waste elimination)
Related to maintaining proper water balance
Ammonia is a highly toxic, water soluble byproduct of the breakdown of amino acids – carried in blood and body fluids
Eliminating ammonia means eliminating water

17. Excretion (waste elimination)
Marine invertebrates (like sponges, cnidarians) have thin bodies and get rid of ammonia by diffusion through body surfaces or gill surfaces
Freshwater flatworms have flame cells, which remove water and water soluble wastes
Flame cells form a network that empties water and wastes through opening in the skin
Can also diffuse waste

18. Excretion (waste elimination)
Annelids, mollusks, invertebrate chordates have nephridia – structures that remove wastes from body fluids and return water and solutes to the body
Waste products eliminated as urine

19. Excretion (waste elimination)
Land invertebrates convert ammonia into urea (less toxic) which is concentrated into urine and expelled
Insects and some spiders convert ammonia into uric acid, which is removed by Malpighian tubules – uric acid excreted with solid waste, conserving water

20. Response
All animals have some sort of nervous system, with individual nerve cells functioning the same
Primitive invertebrates have a nerve net spreading through their body
Some cnidarians (jellyfish) show centralization where nerve cells are more concentrated, forming nerve cords or rings around the mouth

21. Response
Cephalization comes with concentrations of nerve and sensory cells in the head
Primitive flatworms have ganglia (clumps of nerve cells) while insects and some mollusks have actual brains
Brains lead to nerve cords

22. Response
Along with nervous development comes increased sensory development
Flatworms have eye spots
Insects have well developed, compound eyes

23. Reproduction
All invertebrates are capable of sexual reproduction, though some also reproduce asexually
Sexual reproduction creates and helps maintain genetic variation