Question

The development and play of muscles in locomotion is a key characteristic of the animal clade. First, defend this statement by reviewing the importance of muscle-driven locomotion among bilaterians keeping in mind their size and the limitations of protist locomotion-mechanisms . In your second paragraph, discuss key differences between the use of muscles for locomotion in worms with a hydrostatic skeleton and animals with hard internal or external skeletons . In your last paragraph, consider the pros and cons of the following statement - external appendages of radiates and bilaterians we have examined all require muscles to function .

Answer 1

Q) The development and play of muscles in locomotion is a key characteristic of the animal clade. First, defend this statement by reviewing the importance of muscle driven locomotion among bilaterians keeping in mind their sixe and the limitations of protest locomotion mechanisms (3marks). In your second paragraph, discuss key differences between the use of muscles for locomotion in worms with a hydrostatic skeleton and animals with n hard internal or external skeletons (3marks). In your last paragraph, consider the pros and cons of the following statement 0 external appendages of radiates and bilaterians we have examined all require muscles to function (4marks).

Ans:

Muscles are soft tissues made of protein filaments called Actin and Myosin. Muscles are presnt in most of the animals and help in their movements.

Locomotion:

Locomotion is defined as a process of moving from one place to another. Locomotion occurs in both single celled organisms like protists and multicelled organisms like bilaterians.

Locomotion in bilaterians:

These animals show a bilateral symmetry which means they have tow sides, left and right, which are mirror images of each other. Most of the animals, including humans are bilaterians. Exceptions include placezoans, cnidarians and sponges.

Most of the bilaterians have a combination of circular and longitudinal muscles (more common in soft bodied animals). Circular muscles constrict the body making it longer and longitudinal muscles shorten the body. These muscles enabled a hydro-static skeleton in soft bodied animals that show movement in peristalsis. Soft bodied invertebrates like earthworms that have a segmented body show peristaltic locomotion.  A peristaltic wave is generated by the alteration of longitudinal and ciruclar muscle contractions. This wave helps in the movement of soft bodied animals.

Locomotion in protists:

Protists are eukaryotic, microscopic unicellular organisms. Some of the examples of protists are amoeba, euglena,algae and plasmodium. Protists show locomotion in three different ways. Amoeboid movement, Flagellar movement and movement using cilia.

Amoeboid movement: Most common type of locomotion found in eukaryotes. It is a crawling type of the movement which is accomplished by the cytoplasmic flow; The force of the volume of fluid inside the cells causes pulling of the cells that helps cells move forward. Amoeboid movement is observed in amoeba.

Flagellar locomotion: This locomotion is observed in euglenoids, zoo-flagellates and dino-flagellates. These protozoans have flagella which help in their locomotion. The flagella beat independently causing whip like movement.

Cilia locomotion: It is observed in protozoans like flat-worms, example–Platyhelimenthus. Cilia are slender like projections that protrude from cell. The cilia that helps in the locomotion are called motile cilia. The cilia beats against fluid outside the cell causing locomotion.

Differences between the use of muscles for locomotion in worms with hydrostatic skeleton and animals with hard internal and external skeleton:

Locomotion in worms with hydrostatic skeleton: Many animals with a wormlike cylindrical body have a hydrostatic skeleton with a flexible skin and a water-filled body cavity ( coelom or pseudocoelom ).

They move by peristalsis by using opposed circular and longitudinal muscles, which act on the hydrostatic skeleton to change the body's shape.

Locomotion in animals with hard internal and external skeleton: In these animals, muscular and skeletal systems work together for the locomotion. The muscles of the muscular system attach to these bones (skeletal system), pulling on them to allow for movement of the body.