Presentation on theme: "Staring the Crayfish Part 2 – Internal Anatomy"— Presentation transcript:
1Staring the Crayfish Part 2 – Internal Anatomy ArthropodsStaring the CrayfishPart 2 – Internal Anatomy
2Hold on a minute!Why do we dissect animals anyway?
3Why dissect?It is important to learn the similarities and differences between animals – so that we can know about ourselves better.Analogous = organs in different animals that have similar functions (gills vs. lungs)Homologous = animals that share the same organs (frog and human liver)
7Nutrition & the Digestive System The jaws tear the food apart and it passes down a short esophagus to the stomach
8Nutrition & the Digestive System The stomach has 3 teeth made of chitin to grind the food
9Nutrition & the Digestive System The cardiac stomach grinds the foodThe fine pieces of food are passes to the next stomach, called the pyloric stomachIn the pyloric stomach, digestive juices are mixed with the food
10Nutrition & the Digestive System Digested food is passed to the digestive glands where nutrients are absorbed
11Nutrition & the Digestive System Undigested food goes to the intestines where it is eliminated as feces through the anus.
12Excretory SystemThe green glands filter and excrete waste from the blood.They are located at the base of the antennae.
13Respiratory SystemThe gills are feather like structures found underneath the carapaceVery thin walledThey are attached to the chelideds and walking legs.A constant flow of blood to the gills releases carbon dioxide and picks up oxygen
14Respiratory SystemThe feathery nature of the gills give them a very large surface area. Why is this important?
15Circulatory SystemThe crayfish has an open circulatory system
16Circulatory SystemThe blood leaves the dorsal heart through a series of arteries.
17Circulatory SystemAfter leaving the heart, the blood flows into sinuses, or spaces, in the tissuesThe blood picks up nutrients from the digestive gland and oxygen from the gills and carries them to the cellsThe blood flows over the gills picking up more oxygen and releasing carbon dioxide before returning to the heart
18Circulatory System Why do the cells need oxygen & nutrients? Why do the cells produce carbon dioxide?
19Nervous SystemVery simpleNerves carry impulses to the brain
20Nervous SystemVentral nerve cord carries messages to the body
21Nervous System There are ganglia throughout the body Many nerves leave from each ganglionWhere do you think these nerves go?Statocysts are organs used for balance. They are filled with sand and sensory bristles. They are in the base segments of the antennae.
22Reproduction & GrowthCrayfish have separate male and female animals ~ in other words, they are not hermaphroditesExternal Fertilization = eggs are fertilized outside of the female’s bodyFertilized eggs are stored on the last three abdominal sections on the female
23Reproduction & Growth Eggs will hatch in 6 to 8 weeks As the crayfish gets larger, it must molt, or shed its exoskeletonIt molts several times during the first year and about twice per year thereafterThe crayfish is very vulnerable after molting until its exoskeleton becomes hard once again
24Reproduction & Growth Crayfish can live 3 to 4 years They can regenerate, or regrow, lost appendages
25Is your crayfish a male or female? Locate the base segment of each pair of walking legs.The base segment is where the leg attaches to the body.Study the inside surface of the base segments of the 3rd and 4th walking legs.
26Reproductive System - Female Female = observe a crescent-shape slit on the base segment of the 3rd walking leg (genital pore)