Kingdom Animalia

Animals are defined as: Heterotrophic (not making their own food) multi-cellular Having eukaryotic cells Having cells with no cell walls (as opposed to plant cells)

Remember eukaryotic cells have membrane-bound organelles and are more complicated than prokaryotic cells.

Invertebrates Invertebrates are defined as animals with no backbone. Really, they don’t have any bones at all. There are lots of invertebrates! 98% of animals are invertebrates

Here are some examples: Sponges

Cnidarians

Flatworms

Round worms

Annelids

Mollusks

Echinoderms

Arthropods- crustaceans, insects, and arachnids

Evolution Invertebrates are more evolved than plants, fungi, protists or bacteria. Their bodies have specialized cells, which divide up different jobs in the body. For example, many invertebrates have specialized cells for sight, digestion, gas exchange and reproduction.

Invertebrates have symmetry Invertebrates have symmetry. Some have radial symmetry (you can cut through the organism in any direction and the two parts will be the same). Others have bilateral symmetry ( you can cut in only one direction, where the two parts will be the same). Sponges are the exception and do not show any symmetry.

Homeostasis Invertebrates are quite diverse! This means they regulate their bodies in many different ways. Echinoderms have a water vascular system - which allows them move their tube feet, is used to exchange gas, and to remove waste.

Insects have an exoskeleton that protects them from environmental changes and threats. Round worms have a simple nervous system to detect certain chemicals given off by prey or “hosts.”

Energy All invertebrates are heterotrophic, which means they cannot make their own food and have to obtain it from an outside source. Their diet is widely varied: microscopic material, decaying matter, fresh meat, or plants.

Reproduction Invertebrates reproduce in many different ways – asexually, sexually, externally, internally. Echinoderms release gametes (egg and sperm) into the water where fertilization takes place. Sponges can reproduce asexually by producing a structure called a “gemmule.” This gemmule survives tough conditions and then eventually grows into an adult sponge.

Insects usually deposit sperm internally into the female with a special reproductive organ. The developing insect will go through several stages before reaching adulthood.