Question

1. The year is 2050 and you are a scientist working with a Canadian Space Agency investigating new lifeforms from other planets. You have been asked to characterize a new lifeform called “pardigrades” from Planet XB-11.
   1. Pardigrades are highly resistant to solar radiation. Based on your knowledge of Earth-based animal lifeforms, what kind of tissue would you expect to be responsible for protecting pardigrades from irradiation? Justify your answer. (/3)
   2. You have no live pardigrades to study but you think that they must move, based on 18 foot-like structures that you find on the ventral surface of their body (i.e. their underbelly). What kind of tissue would you expect to control voluntary movements of pardigrades? (/1)
   3. You dissect a pardigrade and look at a histological slide of its foot tissue under a light microscope. You observe tissue that is uniform in appearance. When you apply electricity, the tissue contracts uniformly and returns to its resting state. What type of tissue are you observing under a microscope? Justify your answer. (/3)
   4. Your supervisor asks you to investigate how pardigrades are able to stay warm in the cold, vast vacuum of outerspace. Remember: you don’t have access to a live pardigrade. Based on what you know about animals on Earth, explain a simple test or observation you could make to tell you about how pardigrades stay warm. (/2)
   5. You are the only biologist on the team and your colleagues ask you what you can tell them about how you think pardigrades maintain homeostasis. You think about it and decide to tell them you expect that pardigrades use the most common way that animals on Earth maintain homeostasis. Name the most common mechanism through which animals on Earth maintain homeostasis. (/1)

Answer 1

(a) The least radiosensative tissues which donot really get affected much by radiation are the nerve tissue and the muscle tisssue which donot undergo further cell diviision. Thus, these two kinds of tissue would be present in ample amounts in Pardigrades to make them resistant towards solar radiation.

(b)The kind of tissue which might be responsible for the voluntary movements of the Pardigrades are the skeletal muscles. This kind of muscle are composed of parallel bundles of striated multinucleate fibres and they are connected to the bone via means of tendons.

(c)Accordin to the question the probable type of tissue that is being observed under the microscope probably will be skeletal muscle, as it is the only form of tissue which is under voluntary control and maintains more or less has a uniform structure with similar diameters. Moreover the smallest contrcatile units of the skeletal muscle called the Sarcomeres are capable of contracting uniformly and then again revert back to its original state.

(d) According to the question there may be various ways/observation Pardigrade adopt themselves to stay warm in cold -

-Organisms might be able to produce some kind of anti-freeze proteins.

-Organisms may undergo some kind of temporary hibernation (winter sleep) to be able to sustain in adverse conditions.

-They may have something like blubber( a thick layer of fat tissue) or fur to keep them warm.

- Feathers also do help to insulate the organism.

(e) The most common mechanism of maintaining homeostasis is ofcourse the negative feedback mechanism . The most common example of negative feedback mechanism is the regulation of blood pressure by vasoconstriction (the narrowing of the blood vessels by contraction of the smooth muscles reduces blood flow in peripheral vessels , this result in more blood accumulation in the core and thus conserving the heat to stay warm during cold ) in organisms.