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103 Cards in this Set

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encompasses unrelated orders from mayflies (Ephemeroptera) to true flies (Diptera)
A systematic method relying on estimates of overall SIMILARITY, ususally derived from morphology, but sometimes from behavior and molecular evidence.
A systematic method that seeks patterns of SPECIAL similarity based only on synapomorphies (shared, evolutionarily novel features).
Shared, evolutionarily novel features
ALSO: pleisiomorphies

Shared ancestral features
Features unique to a particular group; not shared with another group
lack one clade from amongst descendants of a common ancestor
fail to include two or more clades amongst descendants of a common ancestor
Evolutionary systematics
A systematic method that uses estimates of derived similarity AND estimates the amount of evolutionary change included within the tree. Larger gaps=higher taxonomic status
Compare # of insect species described to # of vertebrates
Vertebrates=virtually all described and studied at some level. Wheeler says 7 spp/taxonomist

Insects=perhaps 5-20% described. Wheeler says 425 spp/taxonomist. GLobal insect diversity may include millions of undescribed species!
the specialization of successive body segments that more or less unite to form sections, or "tagmata", namely the head, ,thorax, and abdomen.
Hexapoda: Segmental composition of head
pragnathal region (usu. 3 segments) + three gnathal segements bearing mandibles, maxillae, and labium
Hexapoda: Segmental composition of thorax
three segments, each with one pair of legs, each with a max. of 6 segments (extant forms; primitive had more)
Orders in Insecta proper
Archaeognatha, Zygentoma, and Pterygota (huge radiation of primarily winged hexapods)
6-legged arthropod=Insecta and relatives. Share morphologies with crustacea=ultrastructure of nervous system, visual system, and development. This argues for Pancrustacea.
Arthropoda: is it monophyletic?
It's controversial, but recent molecular and morphological studies suggest is it monophyletic. Internal relationships are still controversial.
homeotic gene
developmentally regulatory gene
gene Dll
a homeotic gene for mandibles that is similar in insects and crustaceans. Supports monophyly (Pancrusteacea); refutes earlier claims that hexapod mandibles dervied independently from those of crustaceans
internal supports and muscle attachments; infoldings of exoskeleton
Four characters of arthropods
1. paired, jointed appendages
2. hard outer cuticle (exoskeleton)
3. molt during development (not unique)
4. Tagmosis (fusion of segments into specialized regions=head, thorax, abdomen)
What are arthropods, taxonomically speaking?
A phylum that comprises the classes Trilibita (extinct) and Chelicerata, Crustacea, Myriapoda, Hexapoda
What are the four extant arthropod groups?
Chelicerata, Crustacea, Myriapoda, Hexapoda

(Trilobites extinct)
1. representative organisms
2. # legs
3. body plan
4. mouthparts
5. appendages
6. breathing
7. pairs antennae
1. arachnids, horseshoe crabs, eurypterids, ticks, scorpions, mites
2. 4 pairs legs
3. cephalothorax + abdomen
4. chelicerate mouthparts
5. uniramous appendages
6. book lungs
7. no antennae
1. representative organisms
2. # legs
3. body plan
4. mouthparts
5. appendages,
6. breathing
7. pairs antennae
1. crabs, isopods, shrimp, amphipods
2. variable; 4-5 legs + claws
3. cephalothorax + abdomen
4. mandibulate
5. biramous appendages,
6. gills
7. 2 pairs antennae
1. representative organisms
2. # legs
3. body plan
4. mouthparts
5. appendages,
6. breathing
7. pairs antennae
1. centipedes, millipedes
2. 10-750 pair legs
3. head+trunk body plan
4. mandibulate mouthparts
5. uniramous appendages
6. tracheal system
7. 1 pair antennae
1. representative organisms
2. # legs
3. body plan
4. mouthparts
5. appendages,
6. breathing
7. pairs antennae
1. insects and non-insect hexapods
2. 3 pair legs
3. head+thorax+abdomen body plan
4. mandibulate mouthparts
5. uniramous appendages
6. tracheal system
7. 1 pair antennae
When did arthropods arise?
Precambrian (600 mya). Since Cambrian (540 mya), have been dominant life form.
Why are there problems in arthropod classification?
1. phylogenetic method is relatively new.
2. Not much known about development of groups.
3. More work on fossil records needed b/c insects have radiated quickly and intermediates are missing
4. Homoplasy
convergence in characters
Hypothesized relationship b/t taxa of interest.
How are arthropod groups related to one another? (New and traditional views)
Traditional (based on morphological characters):
New (based on molecular data, N.S. characters, and vision):
Chelicerata--Myriapoda--Crustacea--Hexapoda (last two becoming Pancrustacea)
Characteristics of an Insect
Class Insecta (In=latin for "into", secta=Latin "secare" for "cut or divide)

1. Exoskeleton
2. Body part in 3s:
->3 body segments (head, thorax, abdomen)
->3 pairs of legs
->3 mouthparts (mandibles, maxilla, and labium)
Importance of insects (to humans)
* Diverse=est 3-30 mil
* impt ecologically and economically ($30 billion in US alone)--silk, honey, beeswax, dyes, pollination
* Food source in "eastern" cultures
* Pests (food prices would increase 30-50% without pesticides)
*Disease vectors
* Impt models for biological research (eg., drosophilla, flour beetles)
Why do we have collections?
--research (primary)
--Teaching collections
--Personal interests
--Inventory of given habitat
--conservation, species distribution, climate changes, pollinator declines, evolutionary research, electronic databases

Deposited in museums by researchers, professional collectors, students, amateurs
"Copy" of the exemplar specimen of the species.
How estimate rate of speciation?
Using the molecular clock:

1) we can estimate how long ago a specific speciation event (a specific split in the phylogenetic tree) occurred

2) we can do 1) above for all the different speciation events (the splits in a tree) within a given time period - this gives us the rate at which species were originating during this period

3) we can 2) above for many different time periods, and then ask if the rate of speciation differs across time – and if so, when and why it differs?
The clade Ecdysozoa
Ecdysis=molting, thus other groups that molt!

-onychophra (velvet worms), -tardigrada (water bears) -kinorhyncha and priapulida (not discussed)
Nematodes, characters
Member of the clade Ecdysozoa

-Parasites of plants/animals
-diverse group with more than a million est. species
Tardigrada, characters
Member of the clade Ecdysozoa

-Water bears
-semi-aquatic (mosses, lichens, ferns)
-arthropod-like nervous system
-legs NOT articulated (like slinky)
-clawed foot (to hold substrate)
Onychophora, characters
Member of the clade Ecdysozoa

-velvet worms
-terrestrial (In Cambrian, also marine)
-chitin (but lack true exoskeleton)
-paired appendages
-open circ. system
Serial homology
Structures that repeat and share same developmental origin
How did the arthropod body plan evolve? From nematodes to arthropods.
--presence of cuticle and molting -> NEMATODA

--Segmentation, chitin in culticle, presence of lateral appendages ->.ONYCHOPHORA and TARDIGRADA

--jointed apprendages, hard cuticle, fusion of body into specialized sections ->ARTHROPODA
Describe the proto-arthropod
--May have had 20 segments w/appendages
--tagma become: 1-6 -> head, 7-9 -> thorax, 10-20 -> abdomen, including ovipositors (segs 8-9) and cerci (seg. 11)
--6 segs fused w/head=Myriapoda, Crutacea and INSECTA
--3 segs. fused with head=Chelicerata
Evidence for homology of proto-arthropod segments and contemporary tagma
1. Dev/ comparative/ gene expression
2. creation of mutants that express appendages
3. Fossil intermediates/modern remnants (like Monura and bristletails)
Segments in the insect head
1. Labrum (keeps food in)
2. Antennae
3. Lost appendage
4. Mandibles
5. Maxillae (move food, taste receptors)
6. Labium
Fossil Monura
Controversial as basal insect b/c person "etched out" areas to make them clearer
How many species of insects are described?
~1 million described (estimated because of redundancies)
How many insect species are predicted?
--in 1980's, people believed ~2-5 million
--Terry Erwin (smithsonian, 1982) increased est. by 10-fold. Used beetles in canopy of tropical forests as starting point
--Current conservative estimates are 5-10 million (range 2-80 million)
--55-65% of species are insects
Why are there discrepancies between estimates of insect species?
1. number descovered unknown (described more than once)
2. effort not similar across groups/areas (popularity)
3. little known about tropics and other areas (80% of taxonimists in N Am or Europe)
4. Methods of extrapolation are controversial
Why are insects so diverse?
Like arthropods:
1. small
2. exoskeleton
3. High birth rate and short generation time
4. very old group

Unique to insects
5. Flight (allows dispersal)
6. complete metamorphosis (parent/offspring difdfer in form and habitat)
7. Phytophagy (assoc with diversity)
Parts of the integument
-Waxy layer
-cement layer
-epidermis (only living layer)
-basement membrane
--undifferentiated cuticle layers equivalent to endocuticle + exocuticle
--20-50-% of dry weight is chitin
--more than 50% protein
--reactive amine group allows binding
Functions of the epidermal layer
--microvilli increase surface area
--produces chitin and proteins to bind it
--produces cuticle
--some exocrine glands that produce pheromones, waxes, cements, and defensive compounds
--pore canals
Functions of the basement membrane
protects adn supports the epidermal cells. Buffers against physical damage, pH shifts.
Functions of exocuticle
--hardness= "Sclerotized"
--chitin molecules form sheets laid down in anti-clockwise fashion
--proteins used to connect chitin chains and sheets (Some color from this)
Functions of endocuticle
--cushiony layer
--keeps growing, can be resorbed/eaten (esp during ecdysis) and regenerated
--support and storage
--chitin chains with no protein binding (proteins "floating")
Functions of epicuticle
--prevents dessication
--dictates outer shape of integument (shiny, bumpy, etc)
--metallic, irridescence
Functions of cement layer
--may be contiguous, an outer mesh, or absent
--limits cuticle expansion (holds shape)
--protects wax
Functions of waxy layer
--prevents dessication
--composed of 15-17 C alkanes (if too warm, they separate and insect dries up rapidly)
Importance of waxes (4)
1. nestmate recognition /communication (CHCs)
2. sexual selection
3. Bee homes
4. Protection (shellac)
Which two areas *don't* have integument?`
1. midgut
2. reproductive structures
How modify the integument to increase external hardness/rigidity?
1. add more proteins and/or specialized proteins
2. add metals (Zn, Mg, Cu)--often black. Mandibles, ovipositors, tarsal calws, etc.
How modify the integument to provide internal support/muscle attachments?
1. Apodemes=hollow, straight ingrowths of exoskeleton

2. Apophyses=arm-shaped apodemes, usually a hollow, pitlike inflection

Both withstand pressure from flight, eating, etc.
How modify the integument to increase flexibility?
1. leave procuticle undifferentiated (caterpillars, maggots)
2. Produce more unsclerotized cuticle than needed for expansion/telescoping
How modify the integument to increase elasticity?
--Add resilin (colorless polymer of protein added to exo-and endoculticle)
--Adds ability to RETURN to position by absorbing and releasing energy
--only 30% on energy lost as heat (very effic.)
Ecdysial line
Thin, central line that gives way during molting
White light
all wavelengths visible to a given organism
A lack of all wavelengths
Structural colors
--result of interference, diffraction, or scattering of light
--tend to be SHORT WAVE LENGTHS=blue, green, UV
--mostly epicuticle, sometimes exocuticle, rarely epidermis
the addition (or superposition) of two or more waves that result in a new wave pattern
ex. Blue Morpho=little ribs on scales that scatter all but bluek, which has *constructive* interference
When light passes sharp edges or through slits, which deflects and separates the rays
--analogous to a prism
--changes with position
Pigment-based colors
--absorb all wavelengths but those reflected (some may pass through as well)
--white pigments=STRUCTURAL molecule
--produced by metabolism, from food, from symbionts (rare, eg. aphids)
Which pigments are produced from which metabolic process?
* Yellow/white=uric acid (byproducts of purine synthesis)

* Yellow/red/brown/black= Ommochromes (product of tryptophan synthesis)

* Black/brown/yellow/red= Melanins (product of tyrosine synthesis)

* Red= Pteridines (byproducts of pyramidine (DNA/RNA) synthesis)
How are pigments made from food?
yellow/red=carotenoids, flavonoids
Ex. Sphinx moth metabolizes bilin (blue) and yellow pigment from plant to make green
Where are pigments stored?
--cuticle (most)
--epidermal (when cuticle transparent)
--hemolymph and fat body (aphids)
Three (3) sources of color change between and within individuals
1. genes (w/in pops, b/t sexes)
2. influenced by developmental stage, temperature/daylength, plants eaten
3. A few can actively change color (walking sticks, crab spiders)
Functions and characteristics of insect circulatory system
--circulates hemolymph through body
--open or closed
--dorsal longitudinal vessel=heart (w/ ostia, alary muscles), segmental vessels, aorta
-dorsal and ventral diaphragms
body cavity containing hemolymph
How is hemolymph circulated?
--Heart pulsates (peristalsis)
--hemocoel--->in through ostia--->heart--->aorta or segmental vessels (valves counter tidal effect)
--accessory pulsatile organs for appendages
parts of accessory pulsatile organ
Help move hemolymph into appendages with:
--constricting muscle
What is hemolymph?
15-75% insects volume

--PLASMA(90%)--H2Ok amino acids, carbs, fats, salts, proteins, waste--NO OXYGEN

--HEMOCYTES (10%) for metabolism, defense, waste, removal of foreign materials, encapsulation

--defense compounds
Functions of hemolymph
1. lube organs
2. distribute hormones and nutrients
3.dissipate metabolic waste
4. dissipate heat
5. hydrostatic pressure
6. water/nutrient storage
7. defense (sequestration), eg. arachne checkerspot and monarch
Kreb's cycle formula (respiration)
o2 + c6h12o6 --> co2 + h2o +Energy
Tracheal system
A series of structures (spiracles, trachea, tracheoles, etc) that allow ijnsect cells to exchange gases w/ surroundings
--5-50% of body volume
--extensions of epicuticle within trachea
--ringlike, support
Difference between open and closed respiratory system
OPEN: open to outside via spiracles

CLOSED: tracheal system lacks spiracles (diffusion through cuticle, or gills)

Can change from larvae to adult!
How does gas exchange happen in insects?

Ventilation (for larger, more active insects)
How can the tracheal systems of insects change as they develop?
Closed-->open: aquatic insects w/ gills, parasitoids

Passive-->active: in many holometabolous insects (complete metamorphosis

Number of spiracles
experiencing complete metamorphosis
What are the aquatic adaptations for respiration?
--renewal of air supply
--compressible gills

--cuticular respiration
--tracheal gills
--brachial chamber
(read in book)
Developmental origin of the alimentary canal?
foregut and hindgut=ectoderm

midgut and Malpighian tubules=mesoderm
Functions of foregut, midgut, and hindgut
FOREGUT: mech. breakdown, food processing, storage (crop)
MIDGUT: digestions, absorption (enzymes)
HINDGUT: excretion, sybiont storage, reabsorption, H2O regulation
Parts and functions of the preoral cavity
--salivary glands (lube, enzymes, anticoagulants, antibiotics)

--preoral muscles (hemipterans) pump fluids into mouth
Function of the proventriculus
Gizzard, maceration plates
Parts of the foregut
Pharynx, Esophagus, Crop
Parts of the Midgut
Gastric caecum=^ surface area, expels H2O into hemocoel, movement of nutrients, enzymes

Ventriculus=tubular portion (epidermal)

Epithelial cells=produce/secrete enzymes, absorb nutrients

Peritrophic membrane= separates epithelial cells from food (lines ventriculus); perforated, contains embedded enzymes, etc
Functions of peritrophic membrane
--separates epithelial cells from food (lines ventriculus);
--compartmentalizes digestion
--perforated: helps filter toxins
--contains embedded enzymes
--grabs tannins (from plants; bind to proteins)
--protects against infection
Which insects produce a peritropic membrane?
Most, but not:
--insects with liquid diets (unless includes feces, mud, or rotting flesh)
Five (5) steps of digestion in insects
1. Food enters peritrophic membrane space
2. Enzymes breakdown food
3. SMall nutrients penetrate PM and are absorbed by epithelial cells
4. Larger materials (and recycled enzymes) may penetrate PM, or are moved to anterior midgut by fluids on the "conveyor belt"
5. Partially digested food (and enzymes) passes through caecum and back into PM
Parts and function of the hindgut
--Malpighian tubules: elim. waste, pump for salts-->nitrogenous waste follows (reduce in evolutionary time)

--Ileum: sugar absorption and water retention. Stored symbionts (anoxic). Large in roaches, termites, beetles, flies.

--Colon: connects

--Rectum: reabsorbs impt. nutrients and water (via rectal pads); heavy pumps to reuptake H2O.

How can insect digestive systems vary?
--PREDATORS: large storage and well-developed gizzards for infrequent, nutrient-rich food

PLANT-FEEDERS: short gut, no storage, well-developed gizzards for low-quality food requiring a lot of processing

BLOOD, SAP, AND NECTAR FEEDERS: long convoluted gut to increase absorption; flexible gut, little protection, some storage capacity (water stider, cicada, moth, house fly)