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