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Kingdom Animalia



Polar Bear
Click on image for full size (22K jpeg)
Image courtesy of Corel Photography
With over 2 million different kinds of animals, Kingdom Animalia is the largest of the kingdoms. But when you think of an "animal", what image comes to mind? While animals like bears, fish, and birds are the most familiar to us, over half of all the animals on Earth belong to a group of animals known as "arthropods". Arthropods include animals such as centipedes, crabs, insects, and spiders. This means that the majority of animals come from a group of critters that give most folks the creeps!

So, what exactly is an "animal"? With so many different kinds of animals, it's hard to imagine what they all might have in common. First, animals are "multicellular". This means they are made of many cells, unlike bacteria, which are made of only one cell. Second, all animals must get their food by eating other organisms, such as plants, fungi, and other animals. Plants don't have to eat other organisms because they can use the Sun's energy to make their own food. In addition, all animals need oxygen to survive. Did you know that fish can breathe oxygen from the water that passes through their gills and earthworms get their oxygen through their skin?

Kingdom Animalia



Polar Bear
Click on image for full size (22K jpeg)
Image courtesy of Corel Photography
With over 2 million species, Kingdom Animalia is the largest of the kingdoms in terms of its species diversity. But when you think of an "animal", what image comes to mind? While mammals, birds, reptiles, amphibians, and fish are the most familiar to us , over half of all the animal species belong to a group of animals known as arthropods. Arthropods include animals such as centipedes, crabs, insects, and spiders. And with over a million species of arthropods, this means that the majority of animals species come from a group of critters that give most folks the creeps!

So, what exactly is an "animal"? With so much diversity among different animal species, it's difficult to imagine what they all might have in common. First, animals are "multicellular" (composed of many cells). In most animals, these cells are organized into tissues that make up different organs and organ systems. Second, all animals are heterotrophs (= "other feeder"), meaning that they must get their food by eating other organisms, such as plants, fungi, and other animals. (Plants are referred to as autotrophs or "self feeders") because they produce their own food by the process of photosynthesis.) In addition, all animals require oxygen for their metabolism , can sense and respond to their environment, and have the capacity to reproduce sexually (though many reproduce asexually as well). During their development from a fertilized egg to adult, all animals pass through a series of embryonic stages as part of their normal life cycle. Though frogs and humans don't look very much alike, we share many features in common during our embryonic phase.

Kingdom Animalia



Polar Bear
Click on image for full size (22K jpeg)
Image courtesy of Corel Photography
With over 2 million species classified into 30 phyla, Kingdom Animalia surpasses the other 4 kingdoms in terms of its species diversity. But when you think of an "animal", what image comes to mind? While mammals, birds, reptiles, amphibians, and fish are the most familiar to us, over half of all the animal species belong to a single phylum -- the arthropods! Arthropods include animals such as centipedes, crabs, insects, and spiders which all share in common hardened exoskeletons, jointed appendages, and fused body segments. And with over a million species of arthropods, this means that the bulk of animal diversity of Earth belongs to a group of organisms that give most folks the creeps!

So, what exactly is an "animal"? With so much diversity among different animal species, it's difficult to imagine what they all might have in common. First, animals are "multicellular" (composed of many cells). In most animals, these cells are organized into tissues that make up different organs and organ systems. Second, all animals are heterotrophs (= "other feeder"), meaning that they must obtain energy and nourishment by consuming other organisms. (Plants are referred to as autotrophs or "self feeders") because they produce their own food by the process of photosynthesis.) In addition, all animals require oxygen for their metabolism , can sense and respond to their environment, and have the capacity to reproduce sexually (though many reproduce asexually as well). During their development from a fertilized egg to adult, all animals pass through a series of embryonic stages as part of their normal life cycle. In many respects, the embryonic phases are quite similar across animal groups.



Last modified December 17, 1998 by the Windows Team

The source of this material is Windows to the Universe, at http://www.windows.ucar.edu/ at the University Corporation for Atmospheric Research (UCAR). 1995-1999, 2000 The Regents of the University of Michigan; 2000-04 University Corporation for Atmospheric Research. All Rights Reserved. Site policies and disclaimer