Exam 1 Flashcards

Question

Insect Evolution (Simplified) How Can One Study Insect Evolution/Phylogenetic Relationships?

Answer 1

1.) Fossils: relatively poor record, but fossils are sometimes found in sediments from lakes and streams, coal, volcanic ash, and amber. 2.) Biogeographic Analyses (Studies of “disjunct” ranges of certain insect taxa, for example from Africa and South America, were among the earliest evidence for “continental drift”). 3.) Comparative Method (Anatomy, Behavior) 4.) DNA Analyses/Genomics

Answer 2

There are two competing hypotheses: 1.) Uniramia (Atelocerata or Tracheata): Considers the Myriapods to be the sister group, emphasizing common possession of single-branched appendages, Malpighian tubules, and trachea. 2.) Pancrustacea: Considers one group of Crustaceans to be the sister group (some have placed Crustacea as sister group to the Uniramia because of shared mandible mouthparts, thus Mandibulata).

Answer 3

molecular analyses, developmental patterns, and some anatomical evidence (compound eyes, nervous system). It is the current majority position, gaining support. If correct, it means that the “shared traits” supporting the Uniramia hypothesis must be the result of convergent evolution! So –> Insects

Answer 4

Two suggestions: Malacostraca (lobsters, etc.) or a member of a group including Branchiopoda (fairy shrimps, cladocerans) and two obscure groups, Remipedia & Cephalocarida (see Fig. 8.1) - molecular & paleontological evidence support the latter suggestion.

Answer 5

I. The first unambiguous fossils of hexapods (springtails) date to about 380 mya, with the first fossils of true insects (silverfish-like) shortly thereafter (~376 mya)(During the Devonian Period). These first insects were Apterygota (primitively wingless insects, “ones without wings”). There are two modern Apterygote orders. II. The second stage entailed the evolution of wings. We will discuss theories on the origins of wings later. The first wings to evolve could not be folded; insects with this kind of wings are called Paleoptera (“ancient wings” springtials/bristletails & silverfish

Answer 6

one type of Paleopteran insect

Answer 7

III. The next stage in insect evolution entailed the evolution of wings that could be folded and aligned out of the way along the dorsal surface when not being used. All the remaining orders show this kind of wing and are referred to as Neoptera (“new wings”). Neopteran insects first show up in the late Carboniferous Period but diversified tremendously in the Permian (~299 to 250 mya).

Answer 8

Yellow-winged Grasshopper, showing Neopteran wings

Answer 9

The fourth and last major phase of insect evolution entailed the evolution of “complete metamorphosis”. Instead of a juvenile that looked like a non-sexually-mature, wingless version of the adult, a new “larva” stage evolved, followed by a transforming “pupa” stage leading to the adult. The larva and adult often have completely different habitats and feeding modes. These first appear in the late Carboniferous and expand throughout the Permian but radiate explosively in the Mesozoic Era: they now comprise >90% of insect species. Previous Neopteran insects with “gradual metamorphosis” are called Exopterygotes (ones with wings outside); the new type of insects are called Endopterygotes (ones with wings inside). Hypotheses about the evolution of complete metamorphosis will be discussed later.

Answer 10

gradual metamorphosis

Answer 11

complete metamorphosis

Answer 12

At the end of the Permian Period, about 250 million years ago, the greatest of all the Earth’s “mass extinctions” occurred - over 90% of all species on Earth went extinct, including several whole orders of the early insects. Today’s insects are the surviving orders, and new orders descended from them.

Answer 13

Although about 8 orders died out in the end-Permian mass extinction, members of all four major insect groups survived and subsequently radiated explosively. The most recent major types to appear, during the Cretaceous Period (145-65 mya) are: Moths, Termites, Ants, Butterflies, Bees, Fleas, Lice What major evolutionary/co-evolutionary factors are suggested by these new groups of insects?

Answer 14

Insects possess an Exoskeleton comprised of the Cuticle (Figure 2.1). The materials of which the cuticle is made are primarily Chitin (Figure 2.2) and a complex mixture of Cuticular Proteins. The non-cellular cuticle plus the underlying Epidermis of cells collectively are referred to as the Integument.

Answer 15

The external surface of an insect’s body includes areas of hardened plates (Sclerites) between which there may be softer, flexible membranous areas (Arthrodial Membrane).

Answer 16

The external surface of an insect’s body includes areas of hardened plates (Sclerites)

Answer 17

Dorsal sclerites are called Tergites

Answer 18

ventral tergites

Answer 19

lateral tergites

Answer 20

inward foldings of sclerotized regions The non-hardened (non-sclerotized) membranous areas The sclerotized regions may show inward infoldings (Apodemes) or outward projections (spines, setae, acanthae, and microtrichia - Figure 2.6) Apodemes may be evidenced externally by Sutures or Pits.

Answer 21

allow flexibility and expansion.

Answer 22

The Insect Head * Consists of an anterior Prostomium plus 6 fused segments, the back 5 of which bear appendages. * Segmentation is apparent in the embryo but becomes obscured by the time of hatching. * Appendages of the six segments: – 1st: No appendage (“pre-oral or “pre-antennal” segment) – 2nd: Antennae – 3rd: Labrum (“upper lip”) – 4th: Mandibles – 5th: Maxillae – 6th: Labium

Answer 23

* Different Head Regions defined by position of various sutures & pits, and the tentorium, a complex internal apodeme providing support and muscle attachment surfaces. * Regions: Occiput (back), vertex (crown), gena (cheek), frons (forehead), clypeus (area above the labrum) * Eyes: 1 pair of compound eyes, varying number (often 3) of ocelli (simple eyes) (discussed in detail later in semester

Answer 24

* Basal scape and adjacent pedicel (musculated), plus terminal multi-segmented flagellum. * Used for every sense (even vision!) in various insects. * Shape highly variable in different insects.

Answer 25

1.) Labrum (with interior Epipharynx) 2.) Mandibles 3.) Maxillae: Cardo, Stipes, Palp, Galea, Lacinia 4.) Labium (basically a fused second set of maxillae): Submentum, Mentum, Prementum, Palp, Glossae, Paraglossae Not a mouthpart: Hypopharynx (“tongue”)

Answer 26

cardo, stipes, palp, galea, lacinia

Answer 27

Labium (basically a fused second set of maxillae): Submentum, Mentum, Prementum, Palp, Glossae, Paraglossae Not a mouthpart: Hypopharynx (“tongue”)

Answer 28

mouth down (grasshopper)

Answer 29

mouth forward (beetle larva)

Answer 30

mouth backwards (cicada)

Answer 31

3-segmented: Prothorax, Mesothorax, Metathorax Each dorsal tergite is referred to as a Notum (pl., nota) The notum of the first segment (the Pronotum) is often enlarged into a shield-like covering Spiracles (1 pair/segment) are typically present on the mesothorax and metathorax. Each segment has one pair of legs; the mesothorax and metathorax usually have a pair of wings each.

Answer 32

Six Articulating Segments: Coxa Trochanter Femur Tibia Tarsus (varying number of tarsomeres) Pretarsus (claws plus arolium)

Answer 33

1.) Apodous (legless) 2.) Gressorial (walking)/Cursorial (running) 3.) Saltatorial (jumping) 4.) Raptorial (grasping) 5.) Fossorial (digging) 6.) Natatorial (swimming) Other leg modifications: corbiculum (pollen basket), suction disks, tympana (eardrums)

Answer 34

pollen basket

Answer 35

Wings are composed of plates, veins and cells.

Answer 36

1.) Tegmina (leathery forewings of Orthoptera) 2.) Elytra (hardened forewings of beetles) 3.) Hemelytra (hardened basal area of forewings of heteropteran suborder of Hemiptera - “true bugs”) 4.) Halteres (balancing organs - back wings of flies, front wings of male Strepsiptera)

Answer 37

(leathery forewings of Orthoptera)

Answer 38

hardened forewings of beetles

Answer 39

hardened basal area of forewings of heteropteran suborder of Hemiptera - "true bugs"

Answer 40

balancing organs - back wings of flies, front wings of male Strepsiptera

Answer 41

Most insects have modifications so that, effectively, they have just one pair of “airfoils”. Only 1 pair of flight wings: Orthoptera - tegmina; Beetles - elytra; Bugs - hemelytra; Flies - halteres Where two pairs of flight wings are still present, they may be coupled so that they function as one pair. Sometimes this is accomplished just by overlap of the wings, but there are also some special wing-coupling structures.

Answer 42

1.) Floating or Gliding (“Flying Squirrel Hypothesis”) 2.) Sexual Display Structures (“Sexy Cockroach Hypothesis”) 3.) Thermoregulatory Lobes (“Stegosaurus Hypothesis”) 4.) Sails (“Sailboat Hypothesis”) 5.) Gills (“Flying Fish Hypothesis”) (Hypotheses 2-5 are based on “Pre- adaptation”. )

Answer 43

Specifically, wings were thought to be derived from gills that were the upper branches of biramous appendages. Most recently (as in your book) a “dual-origin fusion hypothesis” has gained favor in opposition to the gill hypothesis, with the original function being gliding. See the discussion in your book, pp. 238-241.

Answer 44

Typically composed of 11 segments, with spiracles on the first 8. The terminal segment often bears a pair of sensory cerci (singular, cercus). Females often have ovipositors as modifications of the appendages on segments 8 & 9. (See Fig. 2.25) Males often have an intromittent organ called the aedeagus arising from the 9th segment. Claspers may also be present, in various forms and locations. (See Fig. 2.26)

Answer 45

1.) Styli 2.) Tenaculum & furculum of springtails 3.) Collophore of springtails 4.) Prolegs (w/ crochets) of caterpillars 5.) Gills (mayfly & damselfly naiads) 6.) Cornicles (aphids) 7.) Modified cerci or terminal plates (pincers, etc.)

Answer 46

Entomology is the scientific study of insects (and a few close relatives). * Insects are just one Class within the Phylum Arthropoda & the Kingdom Animalia. Creighton has no other Biology courses devoted to only a single class of organisms - why do insects merit a course all to themselves?

Answer 47

1.) Abundance: There are probably more insects than all other animals combined. A.) Species Richness (number) (E. O. Wilson once collected 43 species of ants, in 26 genera, in a single tree in Peru (equivalent to the total ant fauna of Great Britain or Nebraska!)

Answer 48

* U.S.D.A. (1952): 763,000 * Wilson (1992): 751,000 * Triplehorn & Johnson (2005): 826,000 These estimates show that insects are overwhelmingly the most species-rich group of organisms on Earth to the best of our current knowledge.

Answer 49

Erwin (1982, 1988): 60 million? (based on extrapolations from beetle sampling in one species of tree) Gaston (1991): 5-10 million (based on extensive sampling of bugs, using proportion of known to unknown species) Two recent analyses: agreed on a figure of about 6 million. G & C: “A figure of between two and six million species of insects appears realistic.”

Answer 50

In the U.S., about 400 lbs. per acre (compared to 14 lbs./acre for humans) Worldwide: about 6X human biomass Tropics: Ants = 30% of animal biomass Termites = 10% All other insects = 10%

Answer 51

Wilson (1992) -> 1015 ants Waldbauer (1998) ->1018 total insects

Answer 52

28 Orders, from silverfish to honeybees, living in an incredible range of ecological niches, primarily terrestrial and freshwater. Excellent group to study to shed light on evolutionary and ecological processes (especially speciation, niche specialization, co-evolution with other organisms).

Answer 53

Exoskeleton Segmented bodies with segmented appendages Tagmata Superficial cleavage development Growth by Molting Metamorphosis Tracheal respiratory system Flight

Answer 54

Herbivores – Insects, especially moth and butterfly caterpillars, consume more of the Earth’s vegetation than any other animal group. (Mopane worm example, p. 20-23 - caterpillars eat 10X more leaves in 6 weeks than elephants eat in an entire year and produce 3.8 times more fecal material!) Carnivores - 500,000 species of predators, parasitoids, and parasites

Answer 55

* Dragonflies & Damselflies * Mantids * Assassin Bugs * Minute Pirate Bugs * Lacewings * Ground & Tiger Beetles * Ladybugs * Robber & Hover Flies * Ants * Digger & Paper Wasps * Many Others

Answer 56

Parasitoids consume their victims from inside, like a parasite, but kill their victim, like a predator. One insect ecologist pointed out that over half of the world’s species are part of one three- step food chain: Flowering Plant -> Insect Herbivore -> Insect Parasitoid!

Answer 57

Detritovores (dung beetles, termites) Pollinators & Seed Dispersers (80% of the animal pollinators of the 80% of flowering plants that use animal pollination, therefore the pollinators of ~160,000 species of flowering plants) Food for other animals (including H. sapiens) (G & C: “Probably 1000 or more species of insects are or have been used for food somewhere in the world.”)

Answer 58

Over 1,000 species of insects are consumed by people, in 80% of the world’s nations.

Answer 59

Pollination (worth > $19 billion/year in U.S., at least $235 billion/year worldwide) Crop, livestock, & stored product pests (consume an estimated 1/3 to 1/2 of all food grown for human consumption) Medical & Veterinary Importance as Disease Vectors (malaria: estimated 154-289 million cases & 660,000 deaths/year) (Recently: Zika Virus) Biological Control of weeds, pest insects Commercial Products (Honey = $300 million/year in U.S.; Silk = $1.5 billion/year worldwide, etc.)

Answer 60

Worldwide, Honey Bees pollinate over 200 crops, the value of which is estimated at $19 billion per year in the U.S., at least $235 billion per year worldwide. (In the U.S., crop pollination by native bees adds an additional value of over $3 billion per year!)

Answer 61

silkworm: silk Lac insect: shellac bees: honey Cochineal Scale Insect: red dye

Answer 62

For example, much of what we understand about genetics and development comes from studies of Drosophila, and most of what we understand about animal social behavior comes from studies of Honey Bees! https://www.mybeeline.co/en/p/how-the-honey-bees- navigate https://kxci.org/podcast/drosophila- melanogaster/

Answer 63

Is “Biophilia” part of Human Nature? Each Species is Special & Unique. All Have Amazing Stories to Marvel At!

Answer 64

1.) Evolutionary potential of the insect body plan (segmented body with segmented appendages) 2.) Small size 3.) Specialized ecological niches 4.) Rapid evolution: short generation times, large population sizes 5.) Co-evolution with plants (and as parasites of animals) 6.) Metamorphosis 7.) Diapause 8.) Flight (were the first flying animals and remain the only invertebrates to evolve flight)- opens new niches and promotes isolation/speciation 9.) Highly evolved nervous system & complex behavior.

Exam 1 Flashcards

(100 cards)