Transcript Arthropods
Arthropods Chapter 28 Arthropods • Have a segmented body. • A tough exoskeleton. • Jointed appendages that extend from the body wall. • Environments they occupy are: – Sea, land, and air. The evolution of arthropods, by natural selection & other processes, has led to fewer body segments & highly specialized appendages for feeding, movement, & other functions. Arthropods • Have a digestive tract, an open circulatory system, and an exoskeleton. • Insects has a network of tracheal tubes where gas exchange takes place. Arthropods • Molting – arthropods outgrow their exoskeletons and will shed the entire thing and replace it with a new larger one. • Arthropods are classified based on the number and structure of their body segments and appendages. Arthropods • Groups of Arthropods are: – Crustaceans – crab, shrimp, lobster, crayfish & barnacles. – Spiders – spiders, ticks, scorpions & horseshoe crabs. – Insects – centipedes, millipedes & insects. The easiest way to tell whether an arthropod is an insect or a spider is to count its legs. Spider has 8, insects have 6. Arthropods • Insects – reason for evolutionary success is: – Ability to fly allows insects to colonize new habitats. – They may use many sense organs to respond to stimuli. – Many have a life cycle in which the young are very different from adults. – The body is divided into a head, thorax, and abdomen. – Sensory hairs – insects use these hairs along with its compound eyes to detect minute movements in its environment Arthropods • Difference between a Nymph and a Larva: – A nymph resembles an adult of the same species, but a larva do not. Echinoderms • • • • • • Spiny skin. Internal skeleton. Water vascular system. Suctioncuplike structures called tube feet. Radial symmetry. Examples – sea stars, sea urchins, sand dollars. Comparing Invertebrates • Digestion- intracellular or extracellular. • Respiration- gills, book lungs, or tracheal tubes. • Circulation – Open circulatory system blood is pumped through a system of sinuses. One or more hearts. – Closed circulatory system blood is contained within vessels that extend throughout the body. • Response (nervous system)-senses gather & process information. • Excretion- eliminating nitrogenous wastes from the body. • Movement & support • Reproduction- asexual & sexual Chordates Characteristics • A dorsal, hollow nerve cord • A notocord. • A pharyngeal pouches. • A tail that extends beyond the anus. • A vertebrate is any chordate that has a backbone so any animal with a spinal cord must be a vertebrate. Fish & Amphibians FISH • Aquatic vertebrate. • Most have paired fins, scales, and gills. • Gills –structures that are important for obtaining oxygen from water. • Heart has one atrium. AMPHIBIANS • • • • Lives in water as a larva & on land as an adult. Adult breathes with lungs. Moist skin, no scales and claws. Example – frogs, toads, & salamanders Reptiles & Birds REPTILES • • • • • • • Dry, scaly skin. Lungs. Terrestrial eggs with several membranes. Can live their entire life outside of water. Groups–lizards, snakes, crocodiles, &turtles They do not excrete ammonia like most Chordates. Snakes are reptiles with no legs and skin unlike other reptiles. Reptiles & Birds BIRDS • Maintain a constant internal body temperature. • Outer covering is feathers. • Two legs that are covered with scales and are used for walking, perching. • Front limbs are modified into wings. • Not all birds can fly. • To distinguish bird eggs from reptile eggs, you must test the hardness of the outer shell. • A bird’s heart ensures that oxygen-rich blood never mixes with oxygen poor blood. Mammals • Have hair. • Have the ability to nourish their young with milk. Mammary glands – found only in female mammals • Breathe air. • Have a 4- chambered heart and system that carries oxygen-rich blood directly from the heart to the muscles. • Are endotherms that generate their own body heat internally. • Water in the body is controlled by the kidneys. Mammals 3 Main Groups of Mammals • Monotremes – lay eggs. Ex. Platypus, anteaters. • Marsupials – bear live young, but at a very early stage of development. Ex. Kangaroo, Koalas, Wombats • Placental mammals – have a placenta which exchanges materials between an embryo and its mother. Ex. Mice, cats, dogs, whales, humans