Week 1 - Success, Mechanics, and Naming of Insects, Flashcards
Success of Insects (Evidence and Reasons): Key Points
Evidence: numbers, longevity, diversity
Reasons: physical size, flight, fecundity
Extant
Currently living, still surviving
Taxon
- Any group or rank in a biological classification into which related organisms are classified
- A taxonomic unit in the biological system of classification of organisms, for example: a phylum, order, family, genus, or species
Stenothermic
Capable of living or growing only within a limited range of temperature
Ectothermic
Of or relating to an organism that regulates its body temperature by exchanging heat with its surroundings; cold-blooded.
Success: Numbers
More than 5/6th of all known animal species; 10^18 (one million billion) extant; one ton per tropical acre biomass
Success: Longevity (as a taxon)
First appeared 400 million years ago (before dinosaurs)
Success: Ecological Diversity
Live everywhere but polar ice caps: land, water, high altitude (up to 16500 ft), high/low longitudes, temperatures ranging from -190 deg C to 51 deg C
Success: size
Very small (1/5 mm in length to 22”): need less food to grow to maturity; can use very small spaces for protection; can eat very small bits of food;
Apterous Insects
Without wings, do not fly
Pterygota Insects
Winged, can fly
Success: flight
Most insects either fly, or used to fly (fleas have lost their wings); first winged insects 300 million years ago; allows food capture (increased menu options), escape, travel - colonize new areas, reproduction
Success: fecundity (fertility)
Short life and generation spans plus high numbers of offspring (average insect lays 100-150 fertilized eggs in lifetime of about 1 month); high reproduction rates controlled by competition, disease, weather, food supplies; very responsive to short-term environmental changes
Mechanics of Insects: Key Points
small size exoskeleton body plan vision flight metamorphosis
Metamerism
A linear series of body structures fundamentally similar in structure; in animals, metameric segments are called somites or metameres.
Somites/Metameres
Individual segments of a metameric structure
Etymology
The study of the history of words, origins, and evolution
Mechanics: size
- 70% of all species are between 0.1” and 1.0” (600,000)
- most ecological niches available are in this size range
- high surface area to volume ratio
- flight is dependent on surface area of wings to weight of object to be lifted (weight increases by cube of length, wing surface area only increases by the square of the length)
Mechanics: exoskeleton (functions, composition, characteristics)
- retains water/controls water loss
- laminated, composed of chitin
- provides defense against predators
- lightweight and strong (for muscle attachment)
Exoskeleton layers
- Epicuticle (outer layer)
- Exocuticle (middle layer)
- Endocuticle (inner layer)
Chitin
- material that composes the exoskeleton
- a nitrogenous polysaccharide (a kind of carbohydrate)
- formed via tanning process with the protein sclerotin
How insects breathe
- Through skin via tubes (tracheae) and ports (spiracles)
* Allows oxygen to flow throughout the whole body
Mechanics: body plan (body and legs)
- Segmented body (metamerism)
- Major divisions are head, thorax, and abdomen
- 6 legs, each segmented and jointed (coxa, trochanter, femur, tibia (with preapical bristle), spur, tarsus (with 5 tarsomeres/tarsal segments), tarsal claws
Mechanics: eyes
- hemispherical, multi-faceted
- Facets of compound eyes are called “ommatidia”
- insects see in color
- vision is poor, polarized for some
- produce a mosaic image
Ommatidium
An individual unit in the compound eye, consisting of sensory cells and a lens
Mechanics: flight
- wings are independent structures (not modified limbs)
- made up of braces (veins) and thin cuticle (membrane/exoskeleton) webbing
- powered by muscles in thorax
Numbers of wings
0 - apterous groups (mostly ancient groups)
2 - one pair; diptera order (true flies)
4 - two pairs; multiple orders
Mechanics: metamorphosis (definition)
Growth through shedding exoskeleton
Metamorphosis (types)
“Many/multiple shapes/forms”
* 2 types: hemimetabolous (direct/incomplete), holometabolous (indirect/complete)
Instars
Stages between molts
Hemimetabolous
- Type of metamorphosis
- Direct or incomplete
- Immature stage called nymphs
Nymphs
- Youth stage of hemimetabolous metamorphosis
- Immature insects which look and act like adults
- Ex: grasshoppers
Holometabolous
- Type of metamorphosis
- Indirect or complete
- Immature stage called larva
- Mature stage called imago
- Follows egg-larva-pupa-adult development
Larva
- Youth stage of holometabolous metamorphosis
- Immature insects which have different form, food choices, and habits than adults
- (Ex: butterflies?)
Naming of Insects: Key Points (5)
- taxonomic hierarchy
- what is the species definition
- shared characteristics of arthropods and class Insecta
- who is Linnaeus
- what is a scientific name and how is it written
Naming: taxonomic hierachy groups
Kingdom
Phylum
Class
Order
Family
Genus (capitalized and underlined or italicized)
Species (lower case and underlined or italicized)
– can be followed by an initial of the “authority” (who named it, such as “L.” for Linnaeus)
Naming: species definition
- Capable of interbreeding and producing fertile offspring
- Reproductively isolated from similar organisms (of different species)
- Fundamentally of similar structure
Naming: insect and arthropod shared characteristics (6)
- Segmented body (2 or 3 divisions)
- paired, segmented appendages
- bilateral symmetry
- possessing exoskeleton
- open circulatory system
- paired, ventral nerve cord
Naming: 3 main Arthropod Classes
- Crustacea (crabs, crayfish, lobsters)
- Arachnida (spiders, scorpions, mites, ticks)
- Insecta
“Insecta” etyamology
From Latin “insecare”: in = into; secare = to cut or divide
“Entamology” etyamology
From Greek “entoma” = notched body (segmented/divided body)
Naming: Class Insecta shared characteristics (5)
- body w/ 3 distinct segments
- one pair of antennae
- 3 pairs of legs
- often one or two pair of wings
- “postoral” appendages of the head include: pair of mandibles, pair of maxillae, a hypopharynx, and a labium
Naming: Orders of Class Insecta
- 27 Orders (based mostly on wing structure, some mouth structure)
- 2 Subclasses: Apterygota (wingless - 4 Orders), and Pterygota (winged & secondarily wingless - 23 Orders)
Naming: scientific names
- binomial system (2 words)
- derived from Latin or Greek
- universally accepted
Theophrastus
Greek (287 BC) who devised first systematic naming of classifications: “the father of taxonomy”
Naming: Carolus Linnaeus
- Born 1701 in Sweden
- Wrote “Systema Naturae” (1736) which established the scientific naming convention used still today
- Identified ~2000 insect species; most identification characteristics were based on wing venation patterns
