Question

You are once again the science officer stationed on the starship NX-01. Upon discovery of a new planet, the mission of you team is to conduct a survey of the resources found on the planet. Now that you have conducted an ecological analysis of the planet, you have been called upon to some examine some of the living organisms on the planet. The area your team has been assigned to explore is located on East Darwin near the coast. The seawater is salty, approximately the same concentration as the seas on earth. Inland from the sea is a dry desert region with very little fresh water available. Between the desert and the sea are patches of scrubby grass, averaging approximately 35 cm in height.

Q1

While exploring the coastal areas of east Darwin, you find the remains of a large organism on the beach. The body is approximately 25m long, and appears to be some type of vertebrate-like organism. The organism has four relatively short limbs, attached to a heavy pectoral and pelvic girdle. Because of it’s location, you are at first unsure if it is an aquatic organism that washed up on the beach, or a terrestrial organism that died near the seashore. What respiratory, circulatory excretory and, structural features would you look for during your dissection to determine if it was aquatic or terrestrial? Explain why the structures you have mentioned are important in determining aquatic or terrestrial origins for the organism? (10 pts)

Q2

Describe some of the problems associated with the size of the organism mentioned in question #1. In your answer, address possible problems with movement, transfer of heat energy generated by the body and movement of materials across the epidermis. You must refer to the square cube law in your answer. If you answered terrestrial in question 1 assume your organism is terrestrial for question 2 as well. If you answered aquatic in question 1, assume your organism is aquatic for question 2 as well. (10)

Q3

In a stream you are observing, you see a living organism that appears to be Catadromous. Explain what this means for their physiology? (5)

Q4

These aquatic organisms can sense their environment in a variety of different ways. Discuss two different sensory systems that aquatic organisms may have that humans do not have. (5)

Q5 While continuing to explore your assigned area, you come across a small 4-legged organism (approximately 40 cm high, weight approximately 6 kg) with a feather-like outer covering. It inhabits the scrubby grass strips between the sea and the desert. As you observe the animal, you notice that after grazing on the grass, it walks to the sea and drinks the water. What adaptations might this organism have to be able to drink seawater? Explain. (10)

Q6

You are to travel to the cold regions in far north of the planet for your final explorations before you return to Earth from your continuing mission. Would you expect to large, small animals, both or none in this region? Why? (10)

Answer 1

Q1: Answer- The organism’s respiratory features that need to be observed to confirm whether these were aquatic or terrestrial is the presence of lungs or gills. The feature of the circulatory system that needs to be observed in two-chambered heart system or more than two chambered heart system. Two-chambered heart system animals are generally aquatic. The features of the excretory system that needs to be observed in the type of waste the organism release i.e., ammonia or more detoxified urea or uric acid. Although the type of waste the organism excrete couldn’t be known form the dead organisms, the more complex excretory system will provide evidence of it habitat in terrestrial land. The structural features that will provide evidence for land dwelling are the more developed limbs. In general, having well developed limbs are the characteristics of the terrestrial organism. Hence, the organism are amphibious.

Q2: Answer- The large size organism with short limb signifies that most of times it spends its life in water, however, sometime it moves to the land. Higher the size of the organism more difficult it is for the organism to move in land with short limb. In the water it can however swim faster. Aquatic animals can also regulate their internal body temperature by changing their position in the thermal gradient. Cutaneous gas exchange is the characteristic of aquatic species. The movement of materials across the epidermis in aquatic animals are quicker than the terrestrial organism. The square–cube law describes the relationship between the volume and the surface area. It states that, as a shape grows in size, its volume grows faster than its surface area. The size of the organism makes its body having more volume with less surface area, which needs direct gas exchange also with the cutaneous gas exchange.

Q3: Answer- Catadromous life style proves the amphibious physiology of the organism. They depends on both the water and land for their living. They migrate from the fresh water to the sea water. To migrate from fresh water to sea water they need to cross the land barrier and accordingly they need to cope with land dry environment for a short period of time at least.

Q4: Answer- Aquatic animals do not have eyelids, eyes bulge slightly out and are able to move each eye independently in 180°. They are able to see ultraviolet light unlike humans. Invery low light conditions, they do not rely on the sense of sight, rather they have other better developed senses to compensate. They have good sense of hearing (e.g., otoliths), as sound travels faster in water than the air.