Dichotomous Key, Research Paper Example

Which phyla lack organs?

The phyla porifera

What type of symmetry do they have?

The phyla porifera has a bilateral symmetry because they can only be cut in to two equal parts in one direction and the direction of their   movement is towards the head (Margulis, L. & Schwartz, K.V.  1998).

List all of the phyla that show cephalization?

Cnidaria, anthropoda, chordata, platyheminthes, annnelida,( Gould, James L., and William T. Keeton 1996).

Do all organisms on the table have 3 germ layers (endoderm, ectoderm and mesoderm)? If not, which Phyla have fewer than three germ layers?

Not all animals in picture have 3 germ layers. Sponge and jelly fish which belong to the porifera and cnidaria phyla respectively have two germ layers,( Gould, James L., and William T. Keeton 1996)..

One phylum has more species than all the others. State the name of this phylum and provide several different examples of species found in this phylum.

The phyla anthropoda has far more species than in any other phyla with the insects, probably totalling to   tens of millions. The Arthropods include an incredibly diverse group of taxa like insects, spiders, crustaceans, scorpions, as well as centipedes, (Gould, James L., and William T. Keeton 1996).

According to chapter 24, fish do not all have the same skeletal structure. Describe the differences among fish from the most primitive to more advanced types.

The most primitive class of fish is cyclostomata. This is made up of hagfish and lampreys. They had a miniature skeletal structure and they were jawless. The next in the developmental tree is the super-class gnathostomata which has placoderms. These have movable jaws derived from trans-located set of gill arches.These were the first jaw vertebrates although they also eventually went extinct. Modern fish are also in two categories chondrichythes and osteochythes. Chondrichythes are cartilaginous fish while osteochythes are bony fish. Both the bony and boneless fish have jaws and they feed on a variety of food some being carnivorous and others being herviborous.

Describe the three types of mammals based on how their young develop.

Monotremes are primitive egg-laying mammals such as spiny ant-eaters and the duck-billed platypus. b. Marsupials are mammals that deliver their young while still in an extremely immature state and carry them along their pouches. Most female marsupials have pouches like the kangaroos and koalas. Placental mammals include such mammals like human beings and the primates which produce relatively advanced offsprings that can feed. The young ones are carried in the parents’ womb and feed through a placenta while in the womb. Upon delivery the feed by suckling before advancing to more complex foods

References

Gould, James L., and William T. Keeton(1996). Biological Science, 6th ed. New York: W. W. Norton & Co.

Margulis, L. & Schwartz, K.V. ( 1998). Five Kingdoms. An Illustrated Guide to the Phyla of Life on Earth. New York: W.H. Freeman.