Now we move onto animals. Animals are divided into vertebrates and invertebrates. Vertebrates are animals with a skull and backbone and invertebrates are animals without. The 6 following characteristics are for something to be classified as an animal: they are multicellular, reproduce sexually, develop from embryos, have specialized parts such as organs, they move, and are consumers. Animals are predators and prey, they are hunted and also hunt other organisms. They have come up with way to avoid being eaten though. Some use camouflage to blend in and hide, some have poisonous skin or can spray bad chemicals to deter predators, others have bright colors warning predators that they are poisonous. Some of us wondered how they knew to do this. If they knew from birth it is called innate behavior, but some creatures could modify a behavior making it a learned behavior. Animals also have some seasonal behaviors, such as migrating, or moving to a different place during extreme temperatures. During the winter some animals hibernate. Hibernation is a period of inactivity and decreased body temperature during the winter. Some animals estivate. Estivation is like hibernation during the hotter parts of the summer. They know when to start storing food due to their biological clock, or the internal control of cycles. Some biological clocks control daily cycles. These cycles are circadian rhythms. Some animals know how to migrate by remembering landmarks, or fixed objects. There are birds that even use the earths magnetic field like a compass.
Animals are social and need a way to maintain this, so how do they? They can use communication, or the sending of signals from one animal to another. There are different types of communication such as warnings, identification, intimidation, protecting their homes, courtship, which is used to attract a mate, and protecting their territory. There are other ways to communicate such as pheromones, or communication through chemicals, they can make noises, use body language, or physical touch. Animals also live in groups which can be safer or more dangerous than being alone.
Onto porifera and cnidarians. Sponges (or porifera) have a-symmetry and even though they look like plants, are actually animals. They feed by filtering micro-organisms through their pores, into their collar cells, while the excess water gets pumped through the sponge and through it's osculum to be expelled into the sea. Cnidarians have radial symmetry and can be either polyps or medusas. The main similarity across all cnidarians, is that they have stinging cells. Medusas are bell shaped with tenticles that drape down the bottom, they have a nerve ring instead of a nerve net, the nerve net is common across most cnidarians. Polyps are kinduf an upside-down version of the medusa, but they are more solid and do not have bell shaped bottom. Polyps also stay in one spot most of the time, and have a nerve net.