5.5: Classification

Question 1

Outline the binomial system of nomenclature:

Answer 1

Species are a group of organisms with similar characteristics which can interbreed and produce fertile offspring whereas a genus is a group of similar species.

Species need an international name and so biologists name them using the binomial system of nomenclature. Each species is given two names. The first is the genus name and is given an upper case first letter. The second is the species name and is given a lower case first letter. If the name is printed, italics are used. If on the other hand the name is hand-written, it is underlined.

Question 2

List seven levels in the hierarchy of taxa:

Answer 2

1. Kingdom (King)
2. Phylum (Phillip)
3. Class (Comes)
4. Order (Over)
5. Family (For)
6. Genus (Great)
7. Species (Sex)

Question 3

Distinguish between the following phyla of plants, using simple external recognition features: bryophyta, filicinophyta, coniferophyta and angiospermophyta:

Answer 3

Bryophytes:

• No roots, instead they have structures similar to root hairs called rhizoids. Mosses have simple leaves and stems.
• Spores are produced in capsule. The capsule develops at the end of a stalk.

Filicinophytes:

• Have roots, leaves and short non-woody stems. Leaves are usually pinnate (divided into leaflets) and curled up in a bud.
• Spores are produced in sporangia, usually on the underside of the leaves.

Coniferophytes:

• Shrubs or trees with roots, leaves and woody stems. Leaves are usually narrow with thick waxy cuticle.
• Seeds are produced from ovules on the surface of the scales of female cones. Male cones produce pollen.

Angiospermophytes:

• Many different characteristics but usually have roots, leaves and stems. Stems of flowering plants that develop into shrubs and trees are woody.
• Seeds are produced from ovules inside the ovaries. The ovaries are part of the flower. The fruits then develop from the ovaries and disperse the seeds.

Question 4

Distinguish between the following phyla of animals, using simple external recognition features: porifera, cnidaria, platyhelminthes, annelida, mollusca and arthropoda.

Answer 4

Porifera:

• no clear symmetry
• attached to a surface
• pores through body
• no mouth or anus
• example: sponges

Cnidaria:

• radially symmetric
• tentacles
• stinging cells
• mouth but no anus
• example: jellyfish

Platyhelminths:

• bilaterally symmetrical
• flat bodies
• unsegmented
• mouth but no anus
• example: tapeworm

Annelida:

• bilaterally symmetrical
• bristles often present
• segmented
• mouth and anus
• example: earthworm

Mollusca:

• muscular foot and mantle
• shell may be present
• segmentation not visible
• mouth and anus
• example: slugs and snails

Arthropoda:

• bilaterally symmetric
• exoskeleton
• segmented
• jointed appendages
• example: spiders and insects