Entomology Study Guide for Exam 2
Entomology Study Guide for Exam 2 ENTO-2003-001
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Popular in Entomology
This 14 page Study Guide was uploaded by Jordan Notetaker on Sunday March 20, 2016. The Study Guide belongs to ENTO-2003-001 at Oklahoma State University taught by Dr. Hoback in Spring 2016. Since its upload, it has received 98 views. For similar materials see Insects and Society in Entomology at Oklahoma State University.
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Date Created: 03/20/16
Entomology 2003 Exam 2 Study Guide Types of metamorphosis (4 types seen in insects) None or “no metamorphosis (ametabolous) Gradual metamorphosis (paurometabolous) Incomplete metamorphosis (hemimetabolous) Complete metamorphosis (holometabolous) Gradual metamorphosis Immatures are “miniature” versions of adult, will have the same mouthparts Immatures and adults often occupy the same niche Wings develop between last instar and adulthood Egg, nymph, adult True bugs Grasshoppers Termites Adult stage has wings and is sexually mature Hemimetabolous metamorphosis Egg, nymph, adult Adults and larvae occur in different habitats Larvae are aquatic (naiads) Stoneflies Mayflies Dragonflies Holometabolous (complete metamorphosis) Flies Beetles Bees Butterflies Caddisflies Egg, larvae, pupa, adults Adults and immatures may occupy completely different niches or be in the same area Chitin Exoskeleton contains chitin and protein o Glucose with a modification Makes it indigestible like cellulose o Fiber Surface area to volume ratio o Surface area increases as a square but mass increases as a cube Surface area = L x W x 6 Volume = L x W x H (x^3) Consequence of Size Heat loss Insects are “cold-blooded” o poikilothermic Environment influences body temperature Smaller organisms lose heat faster o Higher metabolism Consequences of size Water loss o Threat of drying out o Desiccation Waterproofing Internal fertilization Sense Organs Touch Movable projections o Antennae, cerci Setae o Hairs or bristles o Non-living but connected to nerve cells Photoreception *Locomotion Center (thorax) Prothorax o One pair of legs o NO WINGS Mesathorax o One pair of legs o Maybe one pair of forewings Elytra Tegmina Hemelytra Metathorax o One pair of legs o Maybe one pair of hindwings Halteres Arthropoda “paired jointed appendages” One pair of legs for each thoracic Segment Leg segments o Tibia o Femur o Trochanter o Coxa o Tarsus (plural tarsi) Tarsal claws, pads, or hairs Honey Bees Collect pollen in the “pollen basket” a slight hollow with hairs on the tibia of the hind legs Immature insects often have legs True legs No legs Pro legs o Lepidoptera Wings NEVER attached to the prothorax May be modified depending on the insect order Only present on adult stages Wing veins Function of wings Flight provides many benefits o Protection o Escape From predators From adverse environmental conditions o Dispersal o Thermoregulation o Communication Find members of the opposite sex Hearing All sounds are vibrations o Picked up by internal sensilla “hearing” is a form of mechanoreception Sounds through air or water are detected by setae o Tympanic membranes Detect “ripple signals” using setae on tarsi Tympanum “eardrum” Thin flat membrane stretched over a hole in the cuticle Air vibrations move the tympanum The vibrations are detected by sensilla and relayed to the nervous system Making noises 4 types of sound production o Stridulation o Vibrating body parts o Tapping/hitting a body part against a surface o Forcing air out of spiracles Stridulation Only done by males Sound made by rubbing wings or legs together Abdomen Sclerites o Armor plates Sutures o Membranous areas between sclerites Abdominal Structures Cerci Spiracles Reproductive structures o Claspers Modified cerci used in mating or defense o Aedeagus Male structure for sperm delivery o Ovipositor Egg laying structure of female Reproductive Structures Male o Claspers Cerci that have been modified into claspers Reproductive Structures Female o Ovipositor Egg laying device o Can be varying lengths and shapes, depending on where eggs are laid o In one order, the ovipositor has a venom sac at the base, used for defense STINGER! Female Internal Reproductive Structures Internal fertilization Accessory glands o Spermathecae o Store sperm o Produce egg shells or other structures Spermathecae Females can store sperm and keep it viable for long periods o 2.5 years for honey bees Control allows one egg to be fertilized by one sperm Male Reproductive Structures Aedeages o Male copulatory organs o Internal fertilization Often highly modified o “Insect penis art” o Professor Maria Fernanda Cardoso Uses o Remove rival sperm Spiracles Openings to the respiratory system Passive system of gas exchange o “Opening the window” Found in adults, nymphs, and larva Spiracles External openings One pair per segment o Normally occur on mesothorax, metathorax and adominal segments 1- 8 None in head, prothorax or genital segments Trachea Series of air-filled tubes Unique to insects Entirely separate from the circulatory system Lined with cuticle Extensively branched -39% of body volume of the June beetle Respiratory System No lungs Airway tubes o Spiracles o Trachea o Tracheoles Hemolymph Insect “blood” Four functions: o Move things around Hormones Sugars Other materials o Isolate foreign objects and dead cells for removal o Clot and heal wounds o Provide hydrostatic pressure Unfold wings Extend mouthparts and other body parts Expand after molt In insects, the hemolymph is: Clear or brown or green DOES NOT contain any respiratory pigments o Hemoglobin In vertebrate blood Picks up gasses 02, from the lungs and carries it to the cells Picks up CO2 and takes it back to the lungs Reflex Bleeding Protection Circulation Open circulatory system o Two main parts Dorsal tubular heart o Heart o Aorta Hemocoel Digestion Digestive tract divided into three sections Foregut o Lined with cuticles and molts o Intake, storage, some grinding and mixing Midgut o Not lined with cuticles does not molt o Digestion and absorption Hindgut o Lined with cuticles and molts o Waste collection and elimination o Dry out waste The Fat Body “Liver” Can be as much as 60% of the total body weight of the insect Removes toxins o insecticides Store energy (fat) o Important in those adults that do not eat Emperor moth Mayfly Cranefly Others Excretory System “Kidneys” Malphighian tubules o Save water and filter wastes Frass happens! Charles Darwin Evolution by natural selection Four Observations Individuals within a population are variable Some of these variations are passed on to offspring (heritable) Many more offspring are produced than can survive Four Observations Survival and reproduction are not random Individuals with favorable traits will produce more offspring over their life time than individuals with less favorable traits Darwin contributed an important component to the theory of evolution: the mechanism Natural selection does not occur in individuals; it occurs at the population level Genetic diversity within a population must be present Natural forces select which individuals survive to pass on their genes Naturals forces change with time and changing environments Three types of natural selection Directional selection Stabilizing selection Disruptive selection Sexual Dimorphism Moth Sexual Selection Males and females have different levels of reproductive investments Reproductive success measured by different criteria o Males: # eggs inseminated More mates usually good o Females: quality of the male More mates usually irrelevant Depends on sex ratio Sometimes role reversal Paternal Investment Male brooding Giant water bug Nuptial gifts Acquired Produced Produced Gift Jerusalem crickets Spermtophore o Protein wrapped around sperm Can weigh 20% of male! Alternative Hypotheses Suicide Male Hypothesis o Male sacrifices himself to improve chances of siring offspring Rapacious Female Hypothesis o Female eats male who tries to escape Communication Transmission of information among or within species Sensory input Photoreceptors Chemoreceptors Mechanoreceptors Thermoreceptors Chemoreception Male moths have as many as 75,000 receptor cells/antenna Female moths have less Pheromones o Chemicals produced by the insect for the purposes of communication Females produce pheromone Mechanoreception Ability to sense vibrations Communicate with sound o Different songs, different communication Setae and tympana in artropods What is behavior? Behavior o Change in activity of an organism in response to a stimulus o Innate Behaviors Instinct Independent of environmental influence Hard-wired o Learned Behaviors Result from environmental conditioning Flexible behaviors Behaviors Innate o Performed without experience Innate human behaviors o Grip when palm touched o Rooting when cheek touched o Crying o Smiling Insects o Small brains o Short life span o Complex life cycles Metamorphosis Innate Behaviors: Movement Kinesis and taxis are two types of movement-related behaviors o Kinesis is an increase in random movements o Taxis is movement in a particular direction Kinesis o Movement in response to stimulus o Non-oriented (directionless) Taxis o Oriented movement in response to stimulus Kinesis Examples Caterpillar o When touched wriggles and drops to ground Cockroach o When disturbed it runs o How fast depends on the intensity of the stimulus o Learning Persistent change in behavior that occurs as a result of experience Types of Learning Habituation Associative learning (classical conditioning) Instrumental learning (trial and error) Latent learning (behavior without immediate reward) Insight learning (problem solving) Associative Learning Wasps detect prey or hosts through chemical cues Can wasps be trained to detect narcotics, explosives? Wasp Hound could have potential for this! Instrumental Learning “learning to do” Depends on the animal’s ability to remember the outcome of past events and modify future behavior accordingly o Also called “operant conditioning” Form of associative learning discovered by the animal itself Running a maze Bees were the best, and were able to negotiate the maze correctly for sugar water Latent Learning Learning without immediate reward Foragers first make short “recon” flights to learn landmarks to food sources Insight Learning Most advanced form of behavior Insight learning involves using reason to solve a problem, and the use of tools Reorganizing memories to construct new response in the fact of a new problem Problem solving by use of reason Use tools to solve a problem Impossible in insects Universal laws of energy First law of Thermodynamics o Energy cannot be created nor destroyed, only changed in form Second law of Thermodynamics o Systems need input of energy or disorder increases Biological Clock Insects have a circadian rhythm o 24 hour biological clock o Photoperiod Detected by occelus Reset by the setting/rising of the sun Insect “day” is about 23.5-24.5 hours long Conserves energy, synchronizes behavior to avoid predators, find food, find mates Diurnal vs. Nocturnal Diurnal o Active during the daylight hours o Have bigger eyes Nocturnal o Active during the nighttime hours o Rely on many other senses When the conditions change MOVE o Behavioral changes o Immediate by individuals ADAPT o Morphological or physiological changes o Through differential survival of the “fittest” DIE o Most insects adults do not survive winter o If entire population eliminated = extinction Types of behavioral activity demonstrated by the Great Sand Dunes Tiger Beetle Basking Beetles exhibit slow movements Hold abdomens close to sand surface for warmth Orient to have maximum exposure to sun Stiliting The beetle straightens its legs to push its abdomen as far off the sand as possible Reduces overheating Shade seeking Seek shaded areas for protection from sun’s energy Shivering Many insects shiver early in the morning to create enough heat in their thorax to allow their wings to function Migration Mass movement of a population Migrating insects ignore food, mates, etc. o Single-minded purpose to get from here to there Migration is almost always by flight o Can hitch a ride on the wind o Army ants walk…or rather march! Record travel was 2,700 miles in 1988, from west coast of Africa to an island in the West Indies One way Insect response to cold temperature Freeze avoidance o Supercooling o Keep body fluids in liquid state Freeze tolerance o Cryoprotectants Freeze Avoidance Compounds to lower freezing point Temperature of freezing o 0 C for pure water o -21.1 C for saturated salt water o -10 C for salt water Remove ice nucleating agents o Freezing at -42 C Clear digestive tract o Molt Freeze Avoidance Synthesize cryoprotectants o Disrupts ice nucleation Glycerol most common o Sugar alcohol Factors affecting insect survival Size o Smaller better Moisture o Dehydration better Nutrition o Empty gut better Temperature o Less fluctuation better Stages of lifecycle o Non-feeding stages better Adaptations Freeze Tolerance Less common strategy Survive ice formation in tissues o Control where and to what extent ice forms Limit supercooling Create ice nucleating proteins o Sometimes utilize microbes Escaping Lethal Temperatures Escape in time o Pupation o Diapause/aestivation Escape in space o Immediate flight o Migration Overwintering Insects can survive temperature extremes by “hibernating” Diapause o During cold weather o Long-term, not immediately reversible Diapause Based on changing day length, NOT on temperature o Token stimulus o Low temps keep it in diapause Eyes detect changing light Brain directs endocrine system to release hormones to prepare for winter Up to 25% of the water in the hemolymph is substituted for glycerol o Sweet, syrupy alcohol o Component of fats Insects can survive to -22 F Snow cover improves survival Diapause v. Hibernation An animal in hibernation can wake up and forage on a warm day o Flies, gnats o Boxelder bugs An animal in diapause cannot wake up until enough “heat units” have accumulated Physiology Age v. Calendar Degree-day o A measure of heat accumulation above a certain threshold o More accurate than a calendar in determining insect life stages Models that predict insect emergence or different life stages can be developed for better pest management Degree-day Maximum temp + minimum temp / 2 = avg. temp Avg temp – base temp of insect (40) = dd
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