Question

Exercise 1. Comparative Anato Animal Type of Circulatory Outstanding System Advantages/ Disadvantages Features Hydra Earthworm Grasshopper Fish Frog Crocodile Turtle Bird Dog Human

Answer 1

Hydra- It belongs to the phylum Cnidaria where the animals don’t have a real circulatory system. The unique feature about the animals is that they doesn’t need a circulatory system. Hydra is generally found in fresh water. Hydra has a fluid filled gastrovascular cavity which helps in the nutrient absorption from water in the form of oxygen and nutrients. Since Hydra is a very small organism, it doesn’t require much complex system to metabolize the available nutrients as compared to complex circulatory systems found in other animals. Moreover, hydra can never ingest or digest its prey like other animals due to its small circulatory system. Therefore, the hydra can never grow beyond a limited size which is a disadvantage of the Hydra’s circulatory system.

Earthworm- it is a most evolved invertebrate that has an advantage of a closed circulatory system. Its circulatory system comprises of a heart and blood vessels for the distribution of oxygen and nutrients throughout the body. The aortic arches in the earthworm functions like a human heart and consists of five pairs that are responsible for pumping blood into dorsal and ventral blood vessels. This closed system can lead to much faster blood circulation due to higher blood pressure, providing more power. The main disadvantage of this system is that closed circulatory system requires more energy as it is a more complex system as compared to open circulatory system.

Grasshopper- Grasshopper is an insect with an open type of circulatory system that requires very less energy as compared to the closed type circulatory system. The circulating liquid also known as hemolymph or blood is required for circulation of nutrients and oxygen throughout the body. The disadvantage is the low metabolic rate as there are limits to the diffusion rate.

Fish- Fish has a closed circulatory system, which comprises of a two chambered heart, blood and vessels. It is the most simplified form of system found in vertebrates. In this system, blood passes through the heart once during one complete cycle. Blood is pumped into the gills through the ventricle where it is re-oxygenated. This unidirectional blood flow produces a gradient of oxygenated and deoxygenated blood in the fish circuit, resulting in less amount of oxygen reaching to some of the organs and tissues. This can reduce the overall metabolic capacity of fish.

Frog- As compared to the fish, amphibians have a three chambered heart, comprising of two atria and one ventricle. The blood from lungs and systems is pumped in to two atria and there is a mixing of blood in the ventricle. This leads to a reduction in the oxygenation efficiency. But at the same time, the advantage of this system is that high pressure in the vessels pushes the blood in to lungs and body.

Crocodile- it is a reptile which is one of the primitive animals to exhibit a four-chambered heart. The unique features of the crocodile heart is two main arteries that arises from same part of heart-one takes blood to the lungs and the other providing an alternate route to the stomach and other body parts. Moreover, there is a presence of a hole in the heart between two ventricles, known as Panizza, which allows movement of blood from one side to another and presence of a specialized connective tissue that slowdowns the blood flow to lungs.

Turtle- The circulatory system comprises of a three chambered heart with 2 atria and 1 ventricle. The ventricle of a reptile is divided more effectively by a partial septum. Due to presence of this partial septum mixing of oxygenated and deoxygenated blood is not completely prevented.

Bird-Like mammals, birds also have a 4 chambered heart. The main advantage is that birds have a larger heart as compared to their body size that is required to maintain the high metabolic demands required for flight. Also, the bird pumps the blood at a lower rate but pumps more amount of blood.

Dog- A dogs heart is almost similar to the human heart, closed and complex type, that can pump blood more efficiently throughout the body. The dogs heart is known as canine heart with the difference of pulmonary veins. Also, the rate at which the blood pumps in heart is much higher as compared to human heart.

Human- Human heart is divided in to 4 chambers: 2 atria and 2 ventricles. Both oxygenated and deoxygenated blood are separated through these chambers, thus improving the efficiency of double circulation, as required in the warm blooded mammals to maintain a constant body temperature. The disadvantage of this system is that blood flows at very high pressure leading to possible damage to the vessels.