Question

1. Identify one unique feature of the reproductive system for the shark, mudpuppy, snake, bird, and pig, and explain its role in the reproduction for that organism.

2. Describe how the excretory system has evolved across this spectrum of animals.

3. Describe how the brain has evolved across this spectrum of animals.

Answer 1

1) Shark: One of the main differences between sharks and other water animals is that the males have claspers that they use to get the sperm into the females. Sharks have two claspers one on each side of their body. And mostly the fertilisation is internal.

Mudpuppy :  primitive tmode of reproduction to most vertebrates. The male Necturus has testes that are located inside the pleuroperitoneal cavity and lacks a more specialized intromittent organ like sex organ found in more advanced level of vertebrates. The sperms are made in the testes and pass through several ductuli efferentes to the cloaca through the archinephric duct. The sperm are then deposited into the water in the form of clumps called spermatophores, which are taken by females for fertilisation.

Snake: They have Hemipenis , which is inserted into the female snakes vent leading to cloaca and then sperm dispersal.

Bird: Both male and female birds have cloaca , where either eggs or sperms are deposited. In mating seasons, the cloacal of both sex birds swell, protruding slightly outside the bodies. When birds feel like mating , they rub their swollen cloacas together. The male's sperm, stored in his cloaca, is deposited into the female's cloaca, where it travels up the chamber fertilizes an egg.

Pig: In pig the reproduction is mammalian, same like humans but in male pig’s testes the unusual factor is that they are anatomically upside down, which means that sperm is stored near the top of the testicle.

2) These animals show the evolution from aquatic animals to amphibians to reptiles to aves to mammals. The change in excretory system is :

In sharks the urinary system is inside body known as archinephros. Then in the amphibians comes the Mesonephros where the urinary systen and reporductive systems are mixed.In the reptiles, birds, and mammals there is greater separation of function, the mesonephros being exclusively genital and the metanephros being exclusively urinary.

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