Kingdom Animalia – Part One

1. Kingdom Animalia – Part One

2. Remember…we’re talking about Kingdom Animalia

3. What characteristics do all members of the animal kingdom share?

4. Characteristics of Kingdom Animalia • Multicellular – what might be the benefit of being multicellular? • Eukaryotic – their cells each have membrane-bound organelles and a nucleus • Heterotrophic – animals are unable to obtain energy from the sun, so they need to consume other organisms • Animal cells lack cell walls (this, among other things, makes us different from plants!)

5. Animal Cell vs. Plant Cell • Look at the diagram below. Notice animal cells are surrounded just by a cell membrane while plants have a cell membrane and a rigid cell wall Cell Wall

6. Animal Kingdom has 2 Main Groups Invertebrates Vertebrates Have a backbone for at least part of their history Only one phylum (Chordata) • Lack a backbone • 97% of all species on Earth are in this category

7. Evolutionary Trends of K. Animalia • If we examine the basic body plan of the members of K. Animalia, we find that they exhibit four major evolutionary trends: 1) Multicellular Development of Tissues 2) No symmetry  Bilateral Symmetry 3) 2 Germ Layers  3 Germ Layers 4) Acoelomate (no gut)  Coelomate (gut surrounded by cells)

8. Trend #1 Multicellular Tissues • Remember: multicellular means you are made up of more that 1 cell. Humans, for example, are made of trillions of cells • The benefit of being a multicellular organism is that your cells can group together to form “tissues” that can them be specialized for different functions (i.e. become organs). • Simple animals are multicellular; however they lack true tissues (e.g. sponges). In more complex animals, cells start to form tissues and simple organs

9. Types of Tissues Found in Complex Animals

10. Trend #2: Body Symmetry • There are three main types of body symmetry: no symmetry(asymmetrical), radial symmetry, and bilateral symmetry • Radial means you can divide the organism into more than 2 equal parts while bilateral means you can divide the organism into 2 like parts.

11. Trend #2: Body Symmetry Why would it be beneficial to be bilateral? As you can see below, bilateral species have developed different body regions (anterior = head; dorsal = back) allowing these regions to specialize into different functions (head = sensory organs).

12. Trend #3: Development of Germ Layers All animal life begins with a single fertilized egg The single egg divides multiple times to form a small ball of cells called a blastula (yes you were once a blastula!) The blastula later develops into “germ layers” (ectoderm, endoderm and mesoderm)

13. Trend #3: Development of Germ Layers Each of these layers becomes specific tissues in an adult Ectoderm – skin, nervous system (in more complex animals it also becomes feathers, scales, hair and nails) Mesoderm – present in more complex animals. Forms organs of circulatory, reproductive, urinary and muscular system. Endoderm – form lining of the gut

14. Why are germ layers important? • Germ layers give us a hint as to how the complexity of organisms has progressed • Lower invertebrates (sponges, jellyfish, etc.) lack a mesoderm (only have 2 germ layers) and therefore have no circulatory systems • In more complex animals, a mesoderm layer (3rd germ layer) is present and it develops into important internal transport systems (digestive systems, circulatory systems, etc.)

15. Trend #4: Body Cavities • Another evolutionary trend is the development of an internal body cavity called a coelom. A true coelom is lined by cells from the mesoderm germ layer. • Some less complex animals groups have “pseudocoelom” (pseudo = false). This is a fluid-filled body cavity that is not surrounded by a layer of cells • The simplest organisms lack coeloms and are therefore called “acoelomate.” In this case, the gut is not lined by cells or surrounded by a fluid-filled cavity.

16. Trend #4: Body Cavities The red circle above is the gut. Notice in the pseudocoelomate, the gut is surrounded by a fluid-filled cavity. In the coelomate organism, the gut is surrounded by a layer of mesoderm cells (in blue).

17. Why is a coelom important? • Having a coelom is beneficial because it helps to: • Protects internal organs • Streamlines the organism • Allows for the evolution of more complex organs and organ systems