Chapter 36 Arthropods Chapter 37 Insects -

Chapter 36 Arthropods Chapter 37 Insects -

Chapter 36 Arthropods & Chapter 37 Insects The real rulers of the Earth Sources used include textbook, (Holt Modern Biology) Just how dominant are arthropods? More than 83% of all described animal

species are arthropods. That's about 160 million insects for each person on Earth. Have evolved to fill a variety of ecological niches from tiny internal parasite to giant bird-eating predator. Arthropods are a lot more than just delicious feasts and disgusting pests. What are the characteristics of an arthropod ?

5 Characteristics of all Arthropods Bilateral symmetry High degree of Cephalization Variety of segmented appendages around the mouth Segmented antennae- sense environment Compound eyes- made of many individual light detectors, each with their own lens.

Segmented Body Each body segment tends to repeat the same suite of structures (ie, a pair of legs, a set of breathing organs, & a set of nerves), sets of segments are grouped into a larger unit, such as the abdomen & cephalothorax. Hard Exoskeleton Made of protein & Chitin (a polysaccharide)

Must molt many times as grows Enzymes digest the layer of exoskeleton inside soften & then shed. It takes a few days for the newly excreted exoskeleton to harden. Jointed Legs How can an animal with a rigid body covering move its legs? a problem for arthropods: flexibility.

All arthropods (arthro = joint, pod = foot) have jointed limbs. In most of the leg, the exoskeleton is hard, but at the joints it is softer and bendable, allowing movement in the same way that a suit of armor does. The limb can be controlled by contracting muscles connected to the exoskeleton on both sides of the joint. Many pairs of limbs ancestral arthropod had

many body segments with one pair of limbs on each segment. in modern arthropods, some limbs have even been lost completely as they evolved to be smaller and smaller, while others have evolved into new shapes. functions.

Tagma-specialized segements Systems in Arthropods All- Open circulatory system Respiration gills (aquatic crustaceans) tracheae book lungs (spiders) Excretion Green glands (Crusteaceans) Malpighian tubules(spiders)

Many arthropods have wings. The two major types of mouthparts are: mandibles, which are jawlike chelicerae (singular, chelicera), which are pincerlike The five major subphyla of the phylum Arthropoda. Arthropods usually divided

into 5 subphyla based on: differences in development in the structure of appendages, such as mouthparts. Trilobites

Extinct Many body appendages with one pair of appendages per segment Trilobites, living in shallow seas, flourished as swimmers, crawlers and burrowers for some 350 million years. They evolved rapidly into many beautiful, bizarre and, even by today's standards, futuristic forms. Fossil evidence of these extraordinary marine creatures are found on all continents, entrapped in the hardened sediments of Ancient Seas. Subphylum Myriapoda Meansmany feet One pair of branched antennae Many body segments

Includes class: Diplopoda (millipedes) Up to 100 body segments 2 pairs of legs on each segment Chilopoda (centipedes) In tropical regions can reach 12 inches long From 15 to 175 pairs of legs Subphylum Crustacea contains about 38,000 known species.

Terrestrial & Marine so diverse their single defining characteristic is having two pairs of antennae. Most also have: a pair of mandibles a pair of appendages on each body segment some branched appendages 16 to 20 segments &

several tagmata Many have a free-swimming larval stage called a nauplius. a. Terrestrial Crustaceans Sow bugs and pill bugs are terrestrial isopods. They lack adaptations for conserving water and live only in moist environments.

They generally feed on decaying vegetation. Pill bugs roll into a ball when disturbed or threatened. b. Aquatic Crustaceans (many species) Copepods -important part of the oceans plankton. In freshwater, much of the plankton are water fleas such as Daphnia species. Barnacles are sessile as adults. Free-swimming barnacle larvae attach to surfaces and develop a shell that encloses the body. Barnacles use their cirri (singular, cirrus) to

sweep food. More aquatic crustaceans Order Decapoda -means10 feet Decapods have five pairs of legs Crayfish, lobsters, crabs, and shrimp are decapods Respiration through gills (see more about crayfish in detail at end of

chapter- know parts for dissection lab) 4. Subphylum Chelicerata Defined by presence of chelicerae The first pair of appendages Modified into pincer or fangs Class Arachnid- spiders, scorpions, mites, ticks Some important Parts : Chelicerae ( in spiders = fangs to inject poison) Pedipalps (hold food)

8 simple eyes at anterior of cephalothorax (NOT compound eyes!) Spinnerets- 3 pairs on tip of abdomen, for making silk Book lungs- like folds in a book= lots of surface area for gas exchange (some spiders use Tracheae for respiration instead) Malpighian Tubes- excretory tubes collect wastes, liquids. The liquid is reabsorbed (to conserve water) & waste is nearly solid. Spiders-A full facial view of any spider shows its killing ability. Two powerful chelicerae, protrude down

Each chelicera bears a hinged fang. Both fangs have ducts that lead up to the venom glands within the head. Spiders fall into two groups, each being classified upon how they strike their prey. The fangs of Tarantulas are so hinged that they articulate in a front-to-back motion allowing them to strike their prey from above. Most other spiders have fangs that are hinged laterally, providing a left-to-right strike. Spider Chelicerae Fangs and Chelicerae of Fangs, Chelicerae of Zebra Jumping Spider Tarantula Spiderling Salticus scenicus Brachypelma smithi (Mexican Red-Knee Tarantula) Anatomy of a spider ** Mites and ticks differ from spiders because they have a fused cephalothorax and abdomen. Life of a Spider Spiders feed on insects and other small animals. Many species are adapted to capture certain prey. Spiders rarely harm humans, but two species in

the United States are dangerous: the black widow the brown recluse A male spider is usually smaller than the female. Females lay eggs in a silken case. 5. Subphylum Hexapoda Class Insecta By many standards- the most successful group of animals on earth. Entomology- the study of insects &

terrestrial arthropods. Body of an insect is divided into 3 tagmata: Head Thorax Abdomen bugs Because they dominate all terrestrial environments that

support human life, insects are usually our most important competitors for food, fiber, and other natural resources. See page 743 for common insect orders See Example organism: Grasshopper Please note parts for dissection lab, see p 745 text.

The crayfish- next 4 pages are notes for dissection lab an abundant freshwater crustacean that is structurally similar to lobsters, which are marine crustaceans. Crayfish, lobsters, crabs, and shrimp are decapods, or members of the order Decapoda. Decapoda means 10 feet. Decapods have five pairs of legs that are used for locomotion.

External Structure The crayfishs body is divided into the cephalothorax, which is covered by the carapace and is divided into the head, which has five segments the thorax, which has eight segments the abdomen, which is is divided into six segments A pair of appendages is attached to each segment of the crayfish. Several pairs have specialized functions.

These appendages include: Antennae

Antennules Mandibles Maxillae Maxillipeds Chelipeds Walking legs Swimmerets Crayfish -Parts for lab Excretion

Green glands assist in excretion of excess water that enters the body by osmosis. Digestion Digestive gland near the stomach secretes enzymes for digestion. Respiration gills. Circulation open. Nervous & Sensory Organs Many small sensory hairs. (sense water vibrations & chemicals) Compound eyes are set on two stalks.

Chapter 37 Insects Entomologists classify insects into more than 25 orders based on characteristics such as: structure of mouthparts number of wings type of development Factors responsible for their success include: ability to fly jointed appendages

large numbers offspring -exoskeleton -small size -short life span Just how dominant are insects? Comparison of 2 of the 5 groups of Arthropods

Insects as Food Insects were undoubtedly an important source of nutrition for our early human ancestors. Even today, they are still collected and eaten by people of many cultures. In Mexico, dried grasshoppers are sold in village markets. High in protein and low in fat, they may be fried or ground into

meal and mixed with flour to make tortillas. Sago grubs, the larvae of a wood-boring beetle, are considered a delicacy in Papua New Guinea. The islanders boil the larvae or roast them over an open fire. Ants, bees, termites, caterpillars, water bugs, beetle larvae, flies, crickets, katydids, cicadas, and dragonfly nymphs are among a long list of edible insects that provide nutrition for the people of Australia, Africa, South America, the Middle East, and the Far East. Indeed, Americans and other descendents of western European culture appear to be unique among peoples of the world in having such a strong cultural taboo against the use of insects as food.

Silkworm pupae for human food in Thailand A Recipe for Maggot Crispies 1/4 cup margarine 4 cups small marshmallows 3 cups crispy cereal 3 cups dry roasted maggots or mealworms In a saucepan, melt margarine and

marshmallows. Remove from heat and stir in cereal and maggots. Spread mixture in a 9x13 greased pan and allow to cool. Insect body is divided into three tagmata: 1. Head -has mandibles and one pair of unbranched antennae. 2. Thorax -has three pairs of jointed legs and, in many species, one or two pairs

of wings. 3. Abdomen -has 9 to 11 segments but neither wings nor legs in adults. Insects and People Insects negatively affect humans by: competing for food transmitting diseases destroying buildings & other manufactured products

Insects benefit humans by: serving as food for other animals pollinating flowers making valuable products such as honey recycling nutrients in ecosystems External Anatomy Grasshopper Internal Anatomy Grasshopper Grasshopper body- three

tagmata: The head mouthparts -labrum & labium are mouthparts that function like upper and lower lips, respectively. a pair of unbranched antennae pairs of simple and compound eyes. The thorax is composed of:

Prothorax Mesothorax Metathorax The abdomen has upper and lower plates Insect mouthparts Circulation, Respiration, &

Excretion Insects have an open circulatory system that transports nutrients through the body. Gas exchange occurs by means of air-filled tracheae that reach deep into the body. Malpighian tubules remove cellular wastes from the hemolymph while conserving water. Nervous system The grasshoppers central nervous system consists of

a brain and a ventral nerve cord with ganglia located in each body segment. Nerves extend from the brain to sensory structures. Insect sensory structures include : simple and compound eyes sensory hairs on antennae and other body parts in some species, a sound-sensing tympanum Reproduction Grasshoppers have separate sexes,

as do all insects. During mating, the male deposits sperm into the females seminal receptacle, where the eggs are fertilized internally. The last segment of the females abdomen forms the ovipositor, which she uses to lay fertilized eggs. Most insects go through metamorphosis.

In incomplete metamorphosis, a nymph hatches from an egg and resembles the adult but has undeveloped reproductive organs and no wings. The nymph molts several times to become an adult. In complete metamorphosis, a wormlike larva called a caterpillar hatches from an egg and molts several times before becoming a pupa. The pupa molts to produce the adult, which resembles neither the larva nor the pupa.

Incomplete vs. Complete metamorphosis Complete metamorphosis -allows larvae and adults of the same species to avoid competing for space and food. -allows survival in periods of harsh weather or scant resources. See writing assignment sheet

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