Chapter 17: Angiosperms

Angiosperms

~300,000 species, enclosed seeds → presence of seeds in fruits

• flowers, fruits, efficient vessels, double fertilization and seed endosperms using stigma

Fruits

develop from mature ovary walls

aid dispersal of enclosed seeds; prevents competition and aids in colonization

Gene duplication

1. duplication of gene A

a. gene A and duplicate of gene A split and share their functions, now being co-dependent for proper functioning

b. duplication of gene A stays as a duplicated copy or becomes non-functional and disappears

c. duplication of gene A acquires a new function and becomes gene C

Secondary metabolites

plants can synthesize molecules that are not essential for cell structure and growth, for defense, protection, or attracting animals/pollinators

• terpenes and terpenoids, phenolics, alkaloids

Terpenes

distinct aromas and insect-repellent

• citronella, rubber, rosin, amber

Phenoles

flavenoids and related compounds (FLAVORS)

• some flowers and fruit colors

• cinnamon, nutmeg, ginger, clove, chilies

• prevents UV damage

Alkaloid

nitrogen-containing molecules that act as toxic deterrents against herbivores or pathogens

• potent effects on animal nervous system

• caffeine, nicotine, morphine, cocaine, and ephedrine

Autoploidy

nondisjunction results in extra chromosomes in the gametes

Alloploidy

hybridization between 2 species with different chromosome counts, followed by whole genome duplication

Flowers

complex reproductive structures

specialized for efficient production of pollen and seeds, and attract pollinators

four organs: sepals, petals, stamens, carpels

Carpel

produce ovules

Pistil

female reproduction: 1 or more carpels

Sepals

green outer layer of flower

Stamens

produce pollen

Stigma

receives and recognizes pollen; only appropriate pollen will be allowed to germinate

Style

long middle portion; pollen tube delivers sperm to ovule, pollen competition happens here

Ovary

encloses and protects ovules. ovaries develop into fruits

Petals

provide protection

Monocots

1 cotyledon, fibrous roots, have petals in multiples of 3s, narrow and parallel veins, scattered vascular bundles, one pore for pollen grains

Eudicots

2 cotyledons, tap roots, have 4 or 5 petals, oval or palmate net-like veins, ringed vascular bundles, have 3 pores for pollen grains

Coevolution

process by which 2 or more species of organisms influence each other’s evolutionary pathway

Specialist vs. generalist pollinators

specialist:

• choose pollen from a specific plant species

• vulnerable to habitat loss, climate shifts, or absence of specific host plants

generalist:

• feed on nectar and pollen from a wide variety of plant species

• longer active seasons and adapt to changing food sources

• sustain populations

Pollination syndrome

suites of flower traits that have evolved in response to natural selection imposed by different pollen vectors, which can be abiotic or biotic

Complete vs. incomplete flowers

complete

• contain all 4 flower organs: sepals, petals, stamens, pistil

• examples: hibiscus, rose, sunflower, lily

incomplete

• flowers that lack one or more organ

• examples: flower of grass plants

Perfect vs. imperfect

perfect

• contain male and female reproductive structures

• examples: lilies, roses, dandelions, wheat, apples, tomatoes

imperfect

• flowers that lack one or more reproductive organ

• can be monoecious and dioecious

• examples: corn, black walnut, cannabis, cottonwood

Domestication syndrome

artificial selection for traints desirable to humans

abiotic pollination syndrome: wind

• wind pollinators produce pollen in copious, tiny air savs

• flowers reduced, often unisexual, no petals

• temperate, rarely tropical

• often flowering in early spring

• oak, beech, hickory, walnut, birch, ragweed

biotic pollination syndrome: bees

• flowers often blue, purple, yellow — bees see different wave lengths of light

• fragrant

• diurnal

• pollen and or nectar rewards

• corolla often bilateral landing platform

• nectar guides