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Taxonomy
What is Scientific Classification?
Scientific classification is how scientists categorize and name plants and animals.
Why do we need scientific classification?
In order to effectively study plants and animals, all scientists need to use the same
names. Using the same names keeps scientists from getting confused about what
species is being referred to. Our current day classification system was created by
Swedish botanist Carl Linnaeaus in 1757; this is what we refer to as Taxonomy.
What is the Linnaean taxonomic system?
The Linnaean taxonomic system is quite useful as a classification system. Not only
does it provide official names for every plant and animal, it also helps scientists
understand how objects are related to one another. The Linnaean system is based on
a series of nested categories. Each Linnaean name is based on Latin and Greek root
words which are often difficult to pronounce. People that are not scientists use
common names. For example, the blue whale is known by two names: 1) Most
people call them by their common name: "blue whale" while 2) Scientists use the
blue whale's scientific name: Balaenoptera musculus.
Classification
Kingdom
Blue Whale Example
Animalia
Phylum
Chordata
Class
Mammalia
Order
Cetacea
[Suborder]
Mysticeti
Family
Balaenidae
Genus
Balaenoptera
Species
musculus
Explanation
Whales belong to the kingdom Animalia
because whales, have many cells, ingest
food, and are formed from a "blastula"
(from a fertilized egg
An animal from the phylum Chordata has a
spinal cord and gill pouches.
Whales and other mammals are warm
blooded, have glands to provide milk for
their off-spring, and have a four-chambered
heart.
Cetaceans are mammals live completely in
the water.
Whales that belong to the suborder
Mysticeti have baleen plates (big filters in
their mouths) rather than teeth.
he family Balaenidae, also called rorqual
whales. They have pleats around their
throat that allow them to hold lots of water
(which contains their food).
A genus is a group of species that are more
closely related to one another than any
group in the family. Balaenoptera refers to
the genus.
A species is a grouping of individuals that
interbreed successfully. The blue whale
species name is musculus.
The publication of Carolus Linnaeus’s 1758 treatise Systema Naturae set the stage
for the hierarchical classification system now used to organise all life forms. It may
look difficult, yet once understood gives clear directions for the understanding of the
relationships between life forms. The format is; Kingdom, Phylum, Class, Order,
Family, Genus, Species. This system gives us information about the organism and
its relationship to other organisms.
The name is two parts (binomial nomenclature), like our own name. The first part
genus) is like our surname e.g. Smith, The second part (species) is our first name
e.g., Steve.
eg Balaenoptera musculus.
Marine Phyla
Annelida
Latin: anellus = little ring
True segmented worms capable of movement*, with a large gut. The phylum
includes the ragworms and lugworms familiar to anglers. *Some species construct a
mucus tube and adopt a sedentary life style.
Arthropoda
Greek: arthron = joint, pous = foot
Crusty (with an external skeleton made of largely of chitin) animals that have
segmented bodies and appendages that can be divided into the cephalum (head),
thorax and abdomen (although in some arthropods like the crabs the abdomen is
effectively hidden by the carapace). The hard external skeleton (exoskeleton) does
not grow and has to be replaced by a new one growing underneath.
Chordata
Latin: chordata = chord
Phylum that contains the mammals including Man. The main characteristic is the
presence of the notochord that is the precursor to the backbone in humans.
Chordates have three features in common. They have a nerve chord (expanded into
the brain on the upper side of the body), notochord (supporting structure) and gill
slits (connect the throat with the outside of the body). They may have these features
at SOME stage in their lifecycle, but not necessarily every stage. Most chordates are
vertebrates (they have a backbone). Some chordates don't, including the Class
Ascidiacea (Ascideans, sea squirts, tunicates).
Cnidaria
Greek: knide = nettle
Radially symmetrical animals with a simple form, all with stinging capsules. These
capsules are activated when chemically or mechanically stimulated. Species appear
as polyps (sea anemones) or medusa (jellyfish), and often a species goes through
both forms in its life cycle (jellyfish, hydroids). Cnidarians live in the sea except for a
few (e.g. hydra) that inhabit fresh water.
Echinodermata
Greek: echinos = sea urchin, derma = skin.
Starfishes, Sea Urchins, Sea Cucumbers and Related Invertebrates
Marine animals that are radially symmetrical (most species) and contain a unique
water vascular system, and tube feet that are used for movement, respiration,
protection (spines) and assist in the capture of food.
The Echinodermata are exclusively marine, and most species are intolerant of
immersion in low salinity water. One remarkable observation is that they are rarely
settled on by barnacles, mussels and other fouling organisms.
Mollusca
Latin: molluscus = soft
Soft bodied animals with a hard external shell (mussels, winkles, snails), or an
internal shell (sea hares, cuttlefish) or have lost their shell in the course of evolution
(nudibranchs). Molluscs have a mantle that secretes the calcium carbonate that
makes up the shell. They inhabitat numerous different environments with a large
number living in the sea.
Octopuses and squids have evolved to intelligent mobile forms with complex
behaviour.
Platyhelminthes (Flatworms)
Phylum: Platyhelminthes, Class: Turbellaria, Order: Polycladida. A group of large,
free-living marine flatworms which are mainly found in tropical coral reefs.
Although not related to molluscs (Phylum: Mollusca) they are often mistaken for sea
slugs (Order: Nudibranchia) because of their brilliant colour patterns.
Porifera (Sponges)
Poriferans are commonly referred to as sponges. An early branching event in the
history of animals separated the sponges from other metazoans. As one would
expect based on their phylogenetic position, fossil sponges are among the oldest
known animal fossils, dating from the Late Precambrian. Since then, sponges have
been conspicuous members of many fossil communities; the number of described
fossil genera exceeds 900. The approximately 5,000 living sponge species are
classified in the phylum Porifera, which is composed of three distinct groups, the
Hexactinellida (glass sponges), the Demospongia, and the Calcarea (calcareous
sponges). Sponges are characterized by the possession of a feeding system unique
among animals. Poriferans don't have mouths; instead, they have tiny pores in their
outer walls through which water is drawn. Cells in the sponge walls filter goodies
from the water as the water is pumped through the body and out other larger
openings. The flow of water through the sponge is unidirectional, driven by the
beating of flagella which line the surface of chambers connected by a series of
canals. Sponge cells perform a variety of bodily functions and appear to be more
independent of each other than are the cells of other animals.
Taxonomy Questions
1. Make up a saying to remember the 7 categories in the classification system.
K…………….. P…………….. C……………. O……………..
F……………… G…………….. S……………….
2. Which phylum do the following animals belong to?
a. Seastars
b. Anemones, seapens and corals
c. Sharks
d. Sponges
3. What type of animals would you find in the following phyla?
a) Arthropoda
b) Mollusca- 3 types
c) Platyhelminthes
4. Which of the phyla has members that belong to the benthic community?
5. Which of the phyla have members that are nekton?
6. Make a list of the different phyla and the identifying characteristics of each.
7. Choose a particular phylum to work with. Collect photos from any source you
wish and identify the species in the photograph with a common name and a
scientific name as well. Collect a minimum of 20 of these.
8. What are the different classes that belong in Phylum Chordata that we find in
the sea?
9. List a few marine examples of each of the classes of animal from Q.8
10. Choose a class from Q.8 that is different to what you have chosen for Q.7 and
do the same. ie collect photographs or pictures and identify with common and
species name.
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