Organ Systems in Other Animals Cow, Fish, Frog, Crayfish

Goals To become aware of the diversity that is present in members of the animal kingdom. To compare the organ systems of humans to other animals.

Digestive System - Cow Cows are large mammals that mainly eat grass and plant material. Plant matter contains cellulose, which is very hard to break down.

Four Stomachs? Much chewing is needed to break down plant fibres. Four stomach chambers are needed to completely digest the tough plant cellulose.

Four Stomachs? Rumen The largest chamber Digests cellulose with the assistance of bacteria. Reticulum – a secondary chamber that digests non-plant material Omasum – absorbs water back into the body. Abomasum the “true stomach” Digests proteins, fats, and sugars, much like a human stomach.

In Humans Human have only one stomach chamber. We cannot digest cellulose. It is thought that the appendix was once a secondary stomach for digesting cellulose.

Respiratory System - Fish Fish live under water, and do not breathe “air” Gills are required to absorb dissolved oxygen directly from the water.

Breathing Water Gills – network of fanned membranes with many blood vessels. O2 is absorbed and exchanged for CO2, much like in human lungs. Why are gills fanned out?

The Operculum Most fish have an operculum, or ‘cheek’ to pump water through their gills. Sharks do not, and must always be moving to keep water flowing across their gills. Operculum

Reproductive System - Frog Frogs are amphibians, which means: They must live part half of their life in water. Lay soft eggs outside of the body.

Laying Eggs Frogs lay gelatinous strands of eggs in the water which hatch into tadpoles. Tadpoles have gills which require them to stay in the water.

Metamorphosis As frogs grow, they lose their gills and grow lungs and limbs. This allows them to live on land.

Humans Baby humans are born functionally the same as adults – just smaller. Humans give live birth.

Skeletal System Crayfish A crayfish is a crustacean with a hard exoskeleton and many specialized appendages. 6 antennae for smelling 8 legs for walking (the front two pairs taste food) Small feathers on the tail segments for swimming Many different mouthparts for handling food Two large claws for defense

Exoskeleton All of their appendages are formed of chitin – the exoskeleton. Crayfish cannot grow larger than their skeleton and must moult it regularly. The crayfish is soft and weak for a short period while the new skeleton grows.

Moulting

In Humans The skeleton is within the body. The body tissues are able to grow around the skeleton. Thankfully, you never have to take your bones out and replace them.