ENTM module 1

Natural selection

- Environment selects

- Acts over *long-time scales* (millions of years)

- Favors traits that give a *survival or reproductive advantage*

Artificial selection

- Humans select

- Acts over *shorter time scales* (many generations)

- Favors *desired traits* chosen by humans

(Dog breeds demonstrate artificial selection, while camouflage patterns demonstrate natural selection)

Pesticide Resistance Examples - "Variation"

Some insects can metabolize or tolerate toxins

Pesticide Resistance Examples - "Selection"

Pesticide kills susceptible individuals

Pesticide Resistance Examples - "Inheritance"

Resistance is passed to offspring

BB or Bb results in what wings

normal wings

bb results in what wings

wrinkled wings

Phylogenetic trees : Roots

Common ancestor

Phylogenetic trees : Tips / Branches

current species

Phylogenetic trees : Nodes

Divergence points (where lineages split)

Phylogenetic trees : Branch length

Evolutionary distance

Monophyletic groups "natural"

- Derived from a *single common ancestor*

- Includes *only and all* species that share that ancestor

Polyphyletic groups "artificial"

Derived from multiple ancestors

Grouped by similar traits, not by a single shared ancestor

Phylum Annelida

segmented worms

Phylum Onychophora

velvet worms

Phylum Arthropoda

joint-legged animals

Complete metamorphosis (holometabola)

Egg → larva → pupa → adult

Antennae on arachnids

0

Arachnids : Legs

8

Body regions : Arachnids

2

Crustaceans : Legs

10+

Crustaceans: Antennae

2 pairs

Crustaceans: Body regions

2-3

Myriapods: Body regions

2

Myriapods: Legs

Many

Myriapods: Antennae

1 pair

Insect: Legs

6

Insect: Body regions

3

Insect : Antennae

1

Natural selection drives.....

adaptation

Phylogenies show...

evolutionary relationships

Arthropods evolved from...

worm-like ancestor

Insects are...

hexapods with 3 body regions

success comes from....

small size, flight, metamorphosis...

Darwin's 5 Key Principles:

Not all individuals survive

Population stability

Limited resources

Variation

Heritability

key formula involving his principles

Variation + Selection = Adaptation

Monophyletic group

Natural group, (ancestor+, ALL descendants)

Polyphyletic group

Artificial, (multiple unrelated lineages)

4 key features arthropods share

Exoskeleton

Jointed appendages

Segmented body

Bilateral symmetry

Epicuticle

outer layer, waxy, waterproof

Exocuticle

middle layer, stiff, sclerotized

Endocuticle

flexible , inner layer

sutures

folds

setae

hair

scales

flattened specialized setae

Resilin: location and function

Found at joints and wing hinges

Provides elastic energy storage

Enables high-frequency movements

the key to insect flight is...

resilin

structure of compound eyes

Composed of hundreds to thousands of ommatidia

Each ommatidium is one visual unit

Light path: corneal lens → cone → photoreceptors

Ocelli (simple eyes)

3 on head

detect light intensity

antennae types : filiform

thread-like

antennae types: Setaceous

bristle-like

antennae types: Moniliform

beaded

Antennae types: Clavate

clubbed

antennae types: Capitate

knobbed at tip

antennae types: Lamellate

plate like fan (scarab Beetles)

antennae types: Plumose

feathery (male moths)

antennae types: Pectinate

comb-like

Antennae types: Aristate

with bristles (flies)

antennae types: Geniculate

elbowed (ants, wasps)

antennae functions

Chemoreception - smell and taste detection

Mechanoreception - touch and air current detection

Hygroreception - humidity sensing

Thermoreception - temperature detection

probiscis

2 maxillae fused together