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Discover the key traits of animals such as heterotrophy, multicellularity, diploidy, and more. Learn about symmetry, body cavity types, and the importance of segmentation in animal evolution. Dive into the diverse world of 35 animal phyla, from invertebrates to vertebrates.
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Characteristics of Animals Section 27.1
Features of Animals:# 1: Heterotrophy & Mobility • Animals cannot make their own food • Most animals move to find food • Food is digested internally • Animals have the ability to make rapid, complex movements
Features of Animals, con’t:# 2: Multicellularity & Tissues • All animals are made of many specialized cells • Animals are the only multicellular group without cell walls • All cells are roughly the same size, regardless of the size of the animal • Similar cells are organized into functional groups called tissues
Features of Animals, con’t:# 3: Diploidy & Sexual Reproduction • Adults cells are diploid – have 2 copies of each chromosome, 1 from each parent • Haploidgametes (sex cells with 1 set of chromosomes) unite to form offspring • The zygote (fertilized egg) is diploid • This allows for genetic diversity
Features of Animals, con’t:# 4: Blastula Formation • The zygote divides to form a hollow ball – the blastula • Cells in the blastula develop three layers which then develop into different structures: • Ectoderm: skin, nervous system • Endoderm: digestive & respiratory systems • Mesoderm: skeleton, muscular, circulatory, reproductive & excretory systems
Animal Body Plans:# 1: Symmetry • Asymmetrical – irregular in shape (sponges) • Radial symmetry – like the spokes of a wheel (sea anemone) • Bilateral symmetry – two equal sides (humans) • right & left sides • dorsal (back) & ventral (belly) • anterior (head) & posterior (tail) cephalization
Animal Body Plans, con’t:# 2: Internal Body Cavity • Found in bilaterally symmetrical animals • Coelom – the body cavity – fluid-filled space between body wall & gut; protects the internal organs • Three plans: • Acoelomate – no coelom • Pseudocoelomate – body cavity between the mesoderm and endoderm – “false coelom” • Coelomate – cavity within mesoderm; allows for greater movement
Animal Body Plans, con’t:# 3: Segmentation • Segments are repeating body units • All higher animals have some degree of segmentation (vertebrae)
Kinds of Animals • 35 phyla • Often divided into 2 major groups: • Invertebrates (without backbones) • Vertebrates (with backbones)