Millipedes Centipedes w Many body segments w Live
Millipedes & Centipedes w Many body segments w Live under rocks & dark places w Really have less than 100 legs w Protects itself by curling up w Millipedes have 4 legs on each segment w Centipedes have 2 legs on each segment millipede centipede
INTRODUCTION TO THE INVERTEBRATES w What are the invertebrates? w The invertebrates constitutes ninety percent or more of the animal kingdom. Invertebrates don’t have an internal skeleton made of bone. w Many invertebrates have: w -- a fluid-filled hydrostatic skeleton, w --hard outer shell like
INTRODUCTION TO THE INVERTEBRATES w Types of cells w All cells can be divided into two large categories. A eukaryotic cell, or eukaryote w Classification of living things w Greek philosopher Aristotle grouped animals according to their physical similarities. w Aristotle’s classification --- mammals. w herbalists used plants to treat disease and needed to know how to identify which plants were poisonous and which had healing powers
INTRODUCTION TO THE INVERTEBRATES w Today biologists classify organisms not by their usefulness but by their physical, chemical, and behavioral similarities. w Taxonomy: The science of classifying living things. the system of classification was derived by Linnaeus
INTRODUCTION TO THE INVERTEBRATES w The smallest group in biological classification is the species. w Similar species are collected into a genus. Similar genera are united into a family. Similar families are combined into an order. Similar orders are collected into a class. w Similar classes are united into a phylum. Finally, similar phyla are collected into a kingdom.
w What is a species? w The species is a group of organisms that are able to interbreed with each other to produce fertile offspring and that usually do not reproduce with members of any other groups. . w the horse and the zebra belong to different species. Although they can mate, the resulting offspring, the “zebroid” is steril w - Hybrids are offspring that result from interbreeding by individuals of different species.
w Kingdoms of life w In 1969, Robert H. Whittaker described a system of classification that distinguished between kingdoms according to cellular organization and mode of nutrition : w 1 - Monera (bacteria and the cyanobacteria). They are prokaryotic. w 2 - Protista : eukaryotic +single cells or colonies of cells. w 3 - Plantae : eukaryotic, multicellular, and photosynthetic. w 4 - Fungi : eukaryotic and multicellular. w Fungi digest organic matter extracellularly and absorb the breakdown products w 4 -Animalia : eukaryotic +multicellular, feed by ingesting other organisms or parts of other organisms
Organization of the Animal Body w Some of the morphological features considered important by most zoologists include: w (1) body symmetry, w (2) grade of tissue construction, w (3) type of body cavity, w (4) segmentation, w (5) cephalization.
w 1 -Asymmetry w Irregular arrangements of body parts. Such animals have no plane of symmetry that can serve to divide the animal into similar halves. Example: many sponges. w 2 -Radial Symmetry. w Body parts arranged around one central axis; any plane passing through the central axis divides the body into similar (mirror image) halves. Examples: most medusae (jellyfish), sea stars, sand dollars. w 3 -Bilateral Symmetry w Body parts divided into equal (mirror image) halves by a single plane of symmetry.
INTRODUCTION TO THE INVERTEBRATES
w Grade of Tissue Construction w Three grades of tissue organization are found among animals; w 1 -Tissue Grade Construction w Found in animals whose multicellular bodies are composed of cells organized into simple tissues but are lacking organs and organ systems. Ex. Sponge w 2 -Diploblastic Construction w Found in animals with two distinct tissue layers derived from the embryonic germ layers ectoderm and endoderm. Examples: Hydra, Phylum Cnidaria. w 3 -Triplobiastic Construction Found in animals with tissues derived from three embryonic germ layers: endoderm, ectoderm, and mesoderm. Examples: flatworm
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