Ecology and Evolution (P2)

Standard Level Biology: Ecology and Evolution (P2) The animal kingdom consists of two separate sub-phyla, vertebrates (chordata) and invertebrates.In invertebrates consist of the following sub-phyla:

1. Porifera (sponges) are sessile animals feeding through pumping water through tissues to filter out food particles. No distinct internal organs.2. Cnidaria (Jellyfish and coral polyps) all have nematocysts (stinging cells) in order to catch food. Include sessile and swimming organisms, digest food through gastric pouch with one opening.3. Platyhelminthes (flatworms) consist of one body cavity, a single gut with opening for food to enter and exit. No other large organs. Flatworms are flat so cells have more surface area to be closer to one another and exchange gases through diffusion.4. Annelida (segmented worms/ringed worms) bodies are divided into sectioned separated by rings, consist of bristles on their bodies with a gastric tract consisting of a mouth excretion end.5. Mollusca (snails, clams, octopi, etc) aquatic mostly, except for snails, commonly use have shells made of calcium.6. Arthropoda (insects, spiders, crustaceans, etc) made of hard exoskeletons (chitin) and segmented bodies. Their limbs are bendable due to their joints. Champions of diversity as they have adapted to most climates and environments of the earth. Come in various sizes.

A dichotomous key consists of a series of key questions with yes/no answers in order to narrow the possibility of the species down through visible characteristics.