Animals Characteristics and Classification

What is an animal? When you think of animals you probably think of a Segmented Worm What is an animal? Tree Frog When you think of animals you probably think of a variety of furry or hairy creatures, and possibly some fish. But the animal kingdom encompasses a wide variety of living things. A few examples are shown here. African Elephant Caterpillar Jelly Fish

What makes an animal? We have to be able to separate animals from other living things like plants and fungi. To do this scientist look for key features. Can you pick out the animal? Animal- a creature that falls under the kingdom animalia- living things including many-celled organisms and often many of the single-celled ones Sea Sponge Venus fly trap

All animals have at least one cell All animals have at least one cell. For an organism to be multicellular it must have more than 1 cell. Many animals have trillions of cells. More cells generally means the organism is more complex. This is a picture of mouse cells under a microscope that have been stained. There are different types of cells, and many animals have cells that perform specialized functions.

All animals are heterotrophs All animals are heterotrophs. Heterotrophs must consume other organic materials for their carbon sources. This means animals must eat other living or once living organisms in order to get the energy they need to survive. They also usually have an internal chamber where they digest their food. Here you see a Giant Panda eating. He must consume the grass (a living organic material) for energy. The food will pass into the digestive tract, where it will be broken down and the nutrients will be absorbed.

Animals have cellular membranes. Animals do not have cell walls. Cell walls are cellular structures specific to plants, algae, and fungi. Plants need cell walls to protect them and help them maintain their shape in times of water shortages and floods. The walls also act as barriers to keep out unwanted materials. Animal cells do not need cell walls because they do not transport water the same way plant cells do. Animals can control water intake much more efficiently. Animal cells also do much more communicating with each other. Cell signaling is a big part of being an animal. Plants and simpler creatures do some cell signaling but not to the same extent. Plant Cells- notice that the cells are all separated by walls. Plants need cell walls to protect their structure. Animal cells do not have cell walls. In fact many animal cells contain specialized structures that interconnect the cells.

Almost all animals have differentiated tissues Almost all animals have differentiated tissues. The simplest case is to have muscle and nervous tissue. Muscle and nervous tissue are a necessity because they allow an animal to move and respond to its environment . Almost all animals are mobile. Even if it is only at one stage of their life cycle. This sea cucumber is using its tiny tentacles to search the ocean floor for plankton and decaying organic material. Both its muscular and nervous system are very important for it to survive and react to its environment.

Most animals have some form of symmetry. In biology symmetry is the balanced distribution of duplicate body parts or shapes. There are two forms of symmetry, bilateral symmetry (which humans have) and radial symmetry. This butterfly is a good example of bilateral symmetry. Its left side matches its right side in two ways. The patterns on its wings are bilaterally symmetrical, and so are its body parts. It has a wing, an antenna, and an eye on each side of its body. Think about your own body. How are you bilaterally symmetrical?

Most animals who have symmetry have bilateral symmetry. This means they will have only one plane of symmetry. You can only divide the organism in one way to produce mirror images. Look at the example below. It is obvious that the bear could only be divided one way to produce mirror images. Symmetrical Mirror images Kodiak bear Not mirror images

For an organism to have radial symmetry it must not have a left or right side. It will only have a top and a bottom and it could be cut many ways to produce mirror images. Think of a pie. If you start in the center and cut from edge to edge you will always have two equal sides. The starfish is considered to have radial symmetry but it is somewhat superficial. The jelly fish is a better example of radial symmetry. Can you explain why? Star fish The star fish has five arms and there are several ways in which you could cut the starfish from the center from edge to edge and not produce mirror images. The jelly fish is basically round with evenly distributed tentacles on its bottom side. Radial symmetry is restricted to a few phyla of animals. Radial symmetry is much more common in plants. Jelly fish pie

Think back to the Sea sponge and Venus fly trap. Both of the organisms consume other living organisms. The sponge filters water through its body to pull out food particles. The Venus fly trap lures bugs onto its palate and then snaps shut digesting the bugs with enzymes. Both are stationary. The sea sponge has a cellular membrane. The Venus fly trap has cell walls. Neither organism has true muscular or nervous tissue. Given this information which organism is an animal? The only way to distinguish that the sea sponge is the animal from the information previously given is the clue that the sea sponge lacks cell walls and the Venus fly trap has cell walls.

If you said the sea sponge you are correct If you said the sea sponge you are correct. The sea sponge is an example of the simplest animal. Things like reproduction, life cycle and body composition are factors we did not discuss that scientist considered when they classified the sea sponge as an animal. Classification in the world of science is about “best fit.” This question was a little tricky because the sea sponge is missing several characteristics of animals that we have covered There are many organisms that do not fit easily into one group, but there are usually a set of determining characteristics that make them most like the group they are put into. Other factors that classify the sea sponge as an animal is its ability to reproduce sexually, they way it digests its food, and the way it matures and develops as it grows.

After determining an organism is an animal, scientist study its features and group it together with other animals that it is most similar to. Classification is based on internal structures and processes and on external characteristics. Least Weasel Elephant Seal Polar Bear Take a minute to ask the students what some their similarities might be, and how they could be classified together. They all belong to the order Carnivora because they meat eating mammals. All of these animals belong to the same Order. They may not look alike but they have many similarities that may not be obvious at first glance. Leopard Pinniped

The Diagram at the right is a representation of the way living things are classified. As you move from kingdom towards species each group contains organisms with more things in common than the one before it. Another way to think of it is that there are fewer members in a common Family than there are in a common Order.

Cat Phylum:Chrodata Class: Mammalia Order: Carnivora Family: Felidae Genus: Felis Species:Felis catus Dog Phylum: Chordata Class: Mammalia Order: Carnivora Family: Canidae Genus: Canis Species:Canis lupus A dog and a cat belong to the same Phylum, Class, and Order. They are both in the Phylum Chordata because they both have vertebral columns. They are both in the Class Mammalia because they have hair, mammary glands, and a specialized ear bone. They are both in the Order Carnivora because they both are meat eating mammals.

When identifying an organism by its scientific name we use only the Genus and Species name. This is called binomial nomenclature. The Genus name is capitalized and the species name is lowercase. It is proper to either underline or italicize both of the names. See the examples below. Common name: Tiger Scientific Name: Panthera tigris Common Name: Roman snail Scientific Name: Helix pomatia

Practice naming these animals with binomial nomenclature. Kingdom: Animalia Phylum: Chordata Class: Mammalia Order: Artiodactyla Family: Suidae Genus: Sus Species: barbatus Kingdom: Animalia Phylum: Mollusca Class: Cephalopoda Order: Teuthida Family: Loliginidae Genus: Loligo Species: vulgaris Species Name: Loligo vulgaris Species Name: Sus barbatus

References www.photokonkurs.com www.flickr.com www.wikipedia.com http://ngm.nationalgeographic.com/ www.yahooimages.com www.images.fws.gov http://animaldiversity.ummz.umich.edu/site/index.html