Animal Diversity

One of the classes I'm taking this semester is Animal Diversity. Not surprisingly, I LOVE this class! It's so fascinating! One of the coolest parts about it has been how much attention we've given to invertebrates. When I started the class, I realized we would spend the majority of the class studying invertebrates, and to be honest, I was a little disappointed. But it's actually so interesting! It's really helped me feel a lot more wonder about all the animals in the world, from sponges to jellyfish, from blue whales to flatworms. Animals that seemed so simple before have been surprisingly complex, like earthworms-- I always used to think of earthworms as being "barely" animals, but they actually have complex organs, a brain, eyes, jaws, and make themselves burrows which they return to daily. 

It's also been really fun to do dissections every week. My lab partner and I have gotten to be really good friends, and we have had fun getting more used to using the instruments and learning a ton about each animal phylum that we've studied. We started with the most basic, Sponges (Porifera), which lack true tissues, symmetry, or any ability to move, and have slowly moved up through the phyla, advancing in complexity through Cnidarians (Jellyfish, sea anemones, corals), Platyhelminthes (Flatworms, tape worms and flukes), Annelids (Earthworms, sea worms, sand worms), Nematoda (Roundworms -- the ones Alicia did lots of work on), Molluscs (Clams, snails, squids, octopi) and now we're working on Arthropods (Spiders, insects, millipedes). Some fun facts I've learned about these animals:

Nematodes are the most abundant type of animal on earth. Of all individual animals (not species, individuals), 80% are nematodes.

Platyhelminthes have extremely complex life cycles-- usually three or more hosts (they're almost all parasitic), and as many as eight different forms and life stages.

All Cnidarians are stinging-- the reason sea anemones feel kinda sticky when you touch them is because they've shot off hundreds of microscopic "harpoons" that are all sticking on the outside of your skin with "strings" still attached to the organism (they're not strong enough to get through human skin and actually hurt you)

Spiders lost their sensory organs (antennae), but many of them use the front pair of their legs as antennae most of the time and walk on only six legs.

The largest arthropod that ever lived was some 13 ft long (It was a giant swimming scorpion)

Our closest relatives as chordates are sea urchins and starfish.

Arthropods are the most species diverse group-- about a quarter of all known animal species are beetles.

There's a wasp that's about the same size as a single celled paramecium-- and it's not even the smallest insect in the world.