Complexity of the Animal Kingdom Learning Outcome G1

Learning Outcome G1 Analyse how the increasing complexity of animal phyla represents an evolutionary continuum

Student Achievement Indicators Students who have fully met this learning outcome will be able to: Compare phyla in terms of: levels of organization cephalization development of a coelom symmetry reproduction Describe the life functions animals need to survive, including: (Examined in depth with specific phyla) feeding respiration internal transport excretion response and motility

Student Achievement Indicators Compare the advantages and disadvantages of different ways animals carry out their life functions (e.g., filter feeding vs. fluid feeding, parasitic vs. free-living, asexual vs. sexual reproduction, sessile vs. motile)

Characteristics of Animals Heterotrophic - eats other organisms or organic material that is decomposing Animal cells do not have a cell wall Animal cells are held together by structural proteins such a collagen Have muscle tissue Have nervous tissue

Characteristics of Animals Generally reproduce sexually, although more primitive animals may have life cycles that include an asexual phase. The lifecycle of animals is generally diploid (2n) and only the gametes are haploid (n) All animals are multicellular eukaryotes

Theory of Origin of Animal Kingdom The animal kingdom is monophyletic If we could trace all animal lineages back it would lead to one common ancestor

Complexity & Diversity Lower invertebrate such as jellyfish or sponges lack a mesoderm, therefore they do not have a complex circulatory, muscular or urinary system More complex animals have a large mesoderm which allows the formation of more complex systems.

Embryonic Development Small flagellated sperm and large non-motile egg Zygote (2n) - A fertilized egg Mitotic divisions start to occur, this is known as cleavage Blastula forms This is a multicellular state In many animals the blastula looks like a hollow sphere

Embryonic Development Gastrulation occurs when the blastula folds inward Embryonic tissues are produced by this folding These tissues will eventually become adult body parts Gastrulation forms germ layer There are three germ layers: Ectoderm (outer layer) - forms the skin and nervous system Mesoderm (middle layer) - forms the circulatory, reproductive, urinary and muscular systems Endoderm (inner layer) – forms the gut

Body Cavity & Symmetry Body Cavity Both type of body cavity and symmetry are used to classify animals There are two types of body cavities: Simple A gut with one opening formed from the endoderm. The opening serves as both a mouth and an anus This type of cavity is present in simple animals Example - flatworm

Body Cavity & Symmetry Complex Gut with both a mouth and anus Having both a mouth and an anus allows one way movement of food through the gut. Allows greater regional specialization Development of chewing mechanisms This occurs in more complex animals Development of coelom, which is a body cavity of space lined with a layer of cells and peritoneum Peritoneum – is a covering membrane that lines the body cavity and covers the internal organs The coelom is located between the gut and wall and is found in all vertebrates and many invertebrates.

Body Cavity & Symmetry Animals with a coelom are known as coelomates Less complex invertebrates may lack a coelom and are known as acoelomates Some animals are known as pseudocoelomates They have an intermediate structure known as a pseudocoelom (“fake-coelom) It is known as a pseudocoelom because the body cavity is not covered by a peritoneum.

Body Cavity & Symmetry Symmetry There are two types of symmetry in Kingdom Animalia: Radial asymmetry Symmetrical around a central axis Not highly adapted for movement Can not move quickly No definite head region or anterior end Example – hydra/ jellyfish

Body Cavity & Symmetry Bilateral symmetry Right and left hand sides of the organisms are identical Designed for speed Have definite head region Gives more immediate information about the environment Have cephalisation Concentration of nerve cells in the anterior region of the body Example – fish/cow/Human