Animal Body Systems

1. Animal Body Systems Section 27.2

2. Important Functions:Digestion • Sponges digest their food inside their cells  the food cannot be larger than the cell • All other animals digest food outside their cells – extracellular digestion  food can be larger • Simple animals have a digestive system with one opening – gastrovascular cavity • Complex animals have a digestive tract with 2 openings – mouth and anus • “Tube within a tube” plan – allows for specialization

3. Important Functions, con’t:Respiration • In simple animals, O2 & CO2 are exchanged by diffusion across moist skin • Aquatic animals use gills – rich in blood vessels, provide a large surface area, must be moist to work • Lungs function on land – do not require as much moisture

4. Important Functions, con’t:Circulation • Larger animals must have some way of transporting O2 and nutrients • Two types of circulatory systems: • Open circulatory system – heart pumps blood through the open spaces of the body cavity; not very efficient • Closed circulatory system – heart pumps blood through blood vessels; blood is not in direct contact with cells – materials diffuse through vessel walls

5. Important Functions, con’t:Conduction of nerve impulses • Needed to coordinate activities • All animals except sponges have nerves • Simple animals have a nerve net – all cells are similar and there is little coordination • Bilaterally symmetrical animals have clusters of nerves – ganglia • In simple animals, ganglia at the anterior end form brain-like structures • Cephalized animals – with heads – have complex brains and sensory organs

6. Important Functions, con’t:Support • Skeleton provides support and a way for the animal to move • Three types of skeletons: • Hydrostatic – water under pressure inside the body cavity; found in soft-bodied invertebrates • Exoskeleton – a rigid external skeleton; found in some invertebrates • Endoskeleton – hard material, such as cartilage or bone, inside the animal

7. Important Functions, con’t:Excretion • The removal of wastes made by cells • These wastes are toxic – poisonous • Aquatic animals can dilute wastes with water • Land animals need to save water, so they may produce urea, which is less toxic • Kidneys then filter urea from the blood and produce urine

8. Important Functions, con’t:Reproduction • Asexual reproduction – only 1 cell • Parthenogenesis – new individual from an unfertilized egg; some insects & fish • Sexual reproduction – 2 cells that join • Hermaphrodites – one animal produces both sex cells; usually does not self-fertilize; can mate with any other • External fertilization – the egg is fertilized outside the female; must be laid in water to keep moist • Internal fertilization – egg is fertilized inside the female & then may given a shell & laid on land or develop inside the mother