Month: December 2016
The last animal I have decided to write about is one that most people do not even consider an animal, but something higher than. This species has managed to colonize each continent and even go off the planet even though it does not possess any great physical defense. The animal that I am talking about of course is the modern human. Most people do not consider us to be humans even though that is exactly what we are. We reproduce, get our nutrients, have similar anatomy, and have similar problems like disease just like most animals but for some reason popular culture has made the use of the word animal to not be equated with humans as well. Humans are coelomate organisms which means that they have a fluid filled space other than the gut in their internal anatomy. They reproduce sexually and are dioecious which means that they have separate sexes. Humans are vertebrates which means they do have an internal skeleton. Humans have great power over reasoning, logic, and communicate to a great capacity. This has allowed them over thousands of years to make an interconnected community that spans the globe. This has happened because humans were able to create languages that allowed them to articulate their ideas to one another. Using language they were able to create writing to preserve ideas across lifetimes, so that knowledge could be built upon. What really started all of this though is that humans were able to create their own food supply, and stop relying on natural resources through farming. This allowed humans to create societies and begin working on things other than simply surviving by getting food. Humans move through a neuromuscular system. They have a complete digestive system. Humans are omnivores so they eat both animal and plant matter. Humans are very unique in the fact that they are able to impact the world so much. They have been able to change the world to fit their needs, instead of adapting to fit the changes that occur in the world. That is what really sets them apart from other animals, and is how they have been able to spread out so far even though they have no physical adaptations that make them threatening or well adapted to survive in certain places. Humans also have almost no predators, and are able to kill most animals that kill them, so they are a top predator even though they have no adaptation like those of other top predators such as large teeth, claws, massive strength, or great speed and dexterity.
This next post will be a little different since it will not be focusing on a single species but rather a type of organisms within a class. This class is stelleroidea and the group from that I will be focusing on in that class is the sea stars. Sea stars are in the phylum Echinodermata. The name of this phylum literally means spiny skin which is true for the sea stars. They have five arms and a radial pentamerous symmetry pattern, which means that it can be put five ways to form two symmetric halves. The ecological role of the sea star is that it is a predator. It feeds mostly on barnacles and other invertebrates. The sea star itself is an invertebrate which means it has no spinal structure even though it still seems hard and has a definite shape. This is because it has structures that give support to it made out of calcium carbonate called ossicles. The sea star has two stomachs. The stomach closer to the mouth is called the cardiac stomach and can be protruded out of the mouth to start external digestion for larger prey. The second stomach is called the pyloric stomach and extends into the arms. This has two uses, it increases the surface area of the stomach for increased breaking down of organic material and it serves to distribute nutrients throughout the body. Something weird about a sea star is that it doesn’t use its arm to move. alternatively, it uses tube feet that are controlled by ampulla that contract to fill the tube feet with water so that contracting different tube feet that are all over the bottom surface will move the organism along a substrate. The sea star also has appendages called pedicellariae which remove material from the surface of the body. The sea star is also considered a keystone species which means that it has a large impact on the diversity of an ecosystem even though it may not have the most biomass within that ecosystem. It has this impact by eating its prey (a species of barnacle) which if left unchecked will outcompete most other species in the intertidal zone decreasing diversity drastically.
Factzoo. (2015). Starfish – sea star, armed sea critter. Retrieved December 7, 2016, from http://www.factzoo.com/invertebrates/starfish-sea-star-armed-sea-critter.html