Organizing
Biological classification is the science of organizing organisms on this planet into groups. The early work on biological classification began with many different scientists all the way back to Medieval times. Today's classification largely started with the work of Carolus Linnaeus in the 1730s.
Since then, scientists have been hard at work and reworking the system for classifying living organisms on this planet. For the most part, scientists look for similarities between organisms when arranging them in the same group. Early on this involved looking at the physical structures/appearances of organisms. This was built upon by scientists who studied evolution, like Charles Darwin. Today, DNA and molecular genetics have been used to compare organisms for classification.
Levels
Most scientists use different levels when comparing organisms. These levels are:
- Kingdom
- Phylum
- Class
- Order
- Family
- Genus
- Species
So, for example. Humans and whales are both in the class "Mammalia". We have certain characteristics in common, like backbones, breathing air, have hair, and produce milk for our offspring. But humans and whales are in different Orders. Humans are in the order "Primates". Whales are in the order "Cetacea".
Different Phyla Under the Ice
We have been showing you pictures of different organisms from under the ice. These organisms each have adapted to the McMurdo Sound environment, though they come from different Phyla. They play different roles in the ecosystem and have different strategies (adaptations) for being successful. Let's take a look at a few of the phyla that are represented in our underwater photos.
Porifera
This phylum includes the sea sponges. We have see a ton of sea sponges on our dives. Can you see any similarities in the sponges we have seen?
Sponges (like Isodictya erinacea) are in the phylum Porifera. (Photo courtesy of Adam Marsh)
Cnidaria
This phylum includes the se anemones, jellyfish, and hydroids. The bottom of McMurdo Sound is covered with these.
Sea anemones (like Isotelia antarctica) are in the phylum Cnidaria. (Photo courtesy of Adam Marsh)
Ctenophora
This phylum includes a lot of small floating organisms. We have seen many of the unique organisms during our safety stops, just floating by.
Comb jellies (Beroe cucumis) are members of the phylum Ctenophora. (Photo courtesy of Stacy Kim)
Nemertina
This phylum includes the long ribbon worms which cover the bottom at some dive sites.
Proboscis worms (Parborlasia corrugatus) are members of the phylum Nermertina (which is why we sometimes refer to them as nemertean worms). (Photo courtesy of Adam Marsh)
Brachiopoda
While we have been looking hard for brachiopods, they have escaped our detection. They sort of look like clams, but with some important differences. We'll keep looking and when we find one, we'll post a picture. Until then, the hunt is on for the elusive brachiopods!
Annelida
This is a phylum containing a lot of organisms from the McMurdo benthic community, including our polychaete worms, Capitella and Spiophanes.
Polychaete worms, like this featherduster worm (Perkinsiana sp.) are in the phylum Annelida. (Photo courtesy of Adam Marsh)
Mollusca
We see lots of members of this phylum as well, especially the soft-shelled clams.
Soft-shelled clams (Laternula elliptica) are members of the phylum Mollusca. (Photo courtesy of Adam Marsh)
Echinodermata
The seafloor is literally covered with members of this phylum, which includes sea stars and sea urchins. There are many different species of echinoderms in McMurdo Sound.
Sea stars are in the phylum Echinodermata. (Photo courtesy of Adam Marsh)
This photo contains two members of the phylum Echinodermata, including sea stars (Odontaster validus) and sea urchins (Sterechinus neumayeri). (Photo courtesy of Adam Marsh)
Arthropoda
This phylum includes some important members of the Antarctic food web, including the krill, isopods, and sea spiders.
Giant Isopods (Glyptonotus antarcticus) are part of the phylum Arthropoda. (Photo courtesy of Adam Marsh)
Chordata
This phylum contains organisms with vertebrae, such as the fish, penguins, and seals.
Fish (like Trematomus bernacchii) are in the phylum Chordata. (Photo courtesy of Adam Marsh)
The Emperor Penguin (Aptenodytes forsteri) is also a member of the phylum Chordata.