All life forms are grouped into three different domains based on
certain characteristics. These three domains are Eubacteria, Archaea,
and Eukaryotes. All the information on domains below is from Wayne
Maddison and his Tree of Life: http://phylogeny.arizona.edu/tree/life.html
The relationship among the three domains: Eubacteria
("True bacteria", mitochondria, and chloroplasts) | Archaea
(Methanogens, Halophiles, Sulfolobus, and relatives) | Eukaryotes
(Protists, Plants, Fungi, Animals, etc.) ? Viruses
The monophyly of Archaea is controversial. Two alternative views
on the relationship of the major lineages (omitting viruses) are
The "archaea tree": ,=============== Eubacteria | | ,== Euryarchaeota
=====| ,=Archaea=| `==| `== Crenarchaeota-Eocytes | `============
Eukaryotes The "eocyte tree": ,======== Eubacteria | | ,===== Euryarchaeota
=====| | `==| ,== Crenarchaeota-Eocytes `==| `== Eukaryotes Domain
Eukarya (includes Animals, Plants, Fungi, Protists, etc.)
The first and main characteristic of Eukarya (also called Eukaryotes)
is that they have a nucleus and undergo mitotic division. They are
also distinguished by complexity of their cells, which contain organelles
that are usually membrane-bound. Some of the membrane bound organelles
include the nucleus, chloroplasts, and mitochondria, among many
others. Eukaryotes also have some organelles that are not membrane
bound, such as motility devices (ex: flagella).
Domain Bacteria (“True Bacteria,” mitochondria, and chloroplasts)
Bacteria are prokaryotes, which means they do not have a nucleus
or membrane bound organelles. An example is cyanobacteria.
Domain Archaea (Halophiles, Methanogens, and their relatives)
Archaea branched off from Bacteria very early in their evolutionary
history. Both Archaea and Bacteria are prokaryotes that do not have
a nucleus and internal organelles found in Eukaryotes. Even though
the two came from the same origins, they are distinctly different.
Archaea are more similar to Eukarya than Eubacteria, which means
that it is more likely to be closely related to humans.
One of the kingdoms under Archaea is Crenarchaeota, which is very
unique. The organisms in this kingdom can handle, even prefer extreme
temperatures and acidity. These organisms are usually microscopic
and single-celled, but they can live in environments that most other
organisms would die in. Out of the species that are known, most
of them come either from marine or terrestrial volcanic environments,
such as shallow or deep-sea thermal vents and hot springs.
Kingdoms in the Domains: Domain: Bacteria Kingdom: Eubacteria Domain:
Archaea Kingdom: Archaebacteria Domain: Eukarya Kingdoms: Protista,
Plantae, Fungi, Animalia Lineage to classification of an organism:
Domain Kingdom Phylum Class Order Family Genus Species
Tree of Life http://phylogeny.arizona.edu/tree/life.html
Life The Science of Biology Fifth Edition. By William K.
Purves, Gordon H. Orians, H. Craig Heller, and David Sadava. Published
by Sinauer Associates, Inc. in 1998.
"Basic Information on the different environments in the ocean."
One way of classifying organisms is by the lifestyle of the organism.
Benthic organisms live on or are buried on the sea floor. Some organisms
are sessile (attached to a substrate) and others can move around.
Pelagic organisms live in the water column, away from the bottom.
These organisms are further divided by how well they can swim. Organisms
that swim weakly or not at all are plankton (they float with the
currents). Planktonic algae and other autotrophs are called phytoplankton,
which are the most important primary producers. The animal plankton
is called zooplankton.
Animals that can swim well are called nekton. They are comprised
mostly of vertebrates, mainly fish and mammals. However, there are
some invertebrates that can swim on its own such as the squid and
Another way to classify marine organisms is by where they live.
The intertidal zone is the shallowest part of the shelf that is
between land and sea. This area is where tides expose some of the
shelf at times.
The subtidal zone is where benthic organisms live on the continental
shelf beyond the intertidal zone.
The benthic zone is away from shelf, which is further divided into
bathyal, abyssal, and hadal zones.
All three of these zones are considered the deep ocean (for simplicity).
However, the bathyal zone is where the shelf breaks (which means
an increase in steepness that marks the outer edge of the continental
shelf) and to a depth of approximately 4,000 meters (13,000 ft).
The abyssal zone is from the depths, of 4,000 m (13,000 ft) to 6,000
m (20,000 ft).
The hadal zone is below 6,000 m (20,000 ft). The pelagic zone refers
to the continental shelf, and is also divided.
The area over the shelf is called the neritic zone.
The pelagic waters, beyond the area where the shelf breaks, are
called the oceanic zone. The pelagic zone is divided vertically
by depth as well as the amount of sunlight that each zone receives.
The shallowest level is the epipelagic zone, where there is plenty
of sunlight for photosynthesis. This area extends to the depths
of 100 m to 200 m (350 ft to 650 ft). Nearly all of the neritic
waters lie in the epipelagic zone.
Next is the mesopelagic zone, where there is not enough light for
photosynthesis but enough to see. This twilight zone is extends
from 200m to 1,000 m (650 ft to 3,000 ft).
Lastly are the bathypelagic, abyssopelagic and hadopelagic zones,
where no sunlight penetrates. This is called the deep-pelagic. These
three zones have the same depth range as the three deep zones in
the benthic section.
Animals in the intertidal zone deal with factors of changes in
salinity, oxygen depletion, being exposed to predators, increase
in temperature, wave actions, and most often desiccation. Therefore,
most of the animals have a hard casing of some sort to help with
all of these factors.
Animals in the pelagic zones, particularly in the upper column
where sunlight still penetrates, have to deal with finding food,
avoiding predators, and finding mates. Because these animals need
to avoid predation, certain traits such as counter-shading and schooling,
Lastly, organisms in the deep ocean deal with factors such as
lack of food, mates, oxygen, and sunlight. Characteristics of these
organisms are large, gaping mouths (to catch any size of prey),
weak swimmers (do not want to use energy to swim), bioluminescence
to find mates and food. Some deep ocean organisms lack eyes and
others do not, they also use of pheromones to attract and find mates.
"Characteristics of Different Phyla"
These animals are asymmetrical, meaning they have no symmetry. They
are filter feeders by means of flagellated cells. Filter feeders
pump in water so that they can obtain their food from what is in
the water. In some cases, the exit ‘door’ or osculum can been seen
with the naked eye. Example: sponges.
Cnidarians have medusa and polyp cycles. The medusa cycle is free
swimming such as a jellyfish. The polyp cycle is stationary such
as an anemone. They have radial symmetry with stinging cells called
nematocysts. Examples: Jellyfish, hydroid, anemones and coral.
There are unsegmented worms that are flattened dorsoventrally. They
move by contracting muscles down its body (ungulates). They have
bilateral symmetry with two eyespots, that are sometimes visible.
Example: Flat worms such as the Mexican skirt dancer.
They are segmented worms with bilateral symmetry. Each of their
segments have a pair of parapodia for movement, which are ususlly
visible to the naked eye. Examples: Fire worms and tube worms.
These animals have bilateral symmetry and segmented bodies. They
also have jointed appendages and an exoskeleton made of chiton.
They have compound eyes, in which usually sit on stalks, such as
a crab's eyes. Examples: crabs, shrimp, barnacles.
Mollusks have bilateral symmetry and a mantle. In snails, chitons,
and bivalves, the mantle secretes their shell. In a squid, the mantle
secretes a pen that is found within the squid. They also have a
muscular foot to help with movement. In the cephalopods (octopus
and squid), the foot has been modified into arms and tentacles.
They also have a radula which is a feeding structure, much like
a rough tongue.
Echinoderms, which means spiny skin, have a calcarious exoskeleton
with a water vascular system. A water vascular system is a network
of water-filled canals that are used in locomotion and food-gathering.
They have pentaradial symmetry. They move by their tube feet. They
have capabilities of regeneration. Examples: Sea urchins, sea stars,
Their characteristics are a notochord, hollow dorsal nerve chord,
pharayngeal gill slits. Vertebrate chordates have a backbone. There
are some chordates that do not have a backbone such as a tunicate.
Examples: fish, sharks, humans, dogs, etc.
Reference: Marine Biology Third Edition By Peter Castro
and Michael E. Huber. Published by McGraw-Hill Company in 2000.
Sample Dichotomous Key: Taking a penny, nickel, dime, and quarter
as the “unknown” species, pick any coin to start with and begin
at #1 and follow the steps. 1. Color a. It is silver in color (See
#2) b. It is copper or brownish in color (Organism is a Penny) 2.
Texture of edges a. Smooth (Organism is a Nickel) b. Rough (appear
to have lines cut on the edges) (See #3) 3. Size a. Smaller than
2.0 cm (Organism is a Dime) b. Larger than 2.0 cm (Organism is a