FLOWERS ! Land Plants Review

FLOWERS !

Land Plants ReviewMoist Dry environments

1) Swimming sperm

(club moss, horsetails, ferns)

2) Airborne pollen + swimming sperm (few gymnosperms)3)Airborne pollen (gymnosperms & angiosperms)4) Animal borne pollen (angiosperms)

Brief History of Land Plants~470 MYA 1st Land Plants

300 MYA 500 species-club mosses, horsetails, ferns, gymnosperms

150 MYA 3,000 species mostly gymnosperms

90 MYA 22,500 species—mostly angiospermsToday 300,000 species—mostly angiosperms

5 STAGES OF LAND PLANT EVOLUTION

5 STAGES OF LAND PLANT EVOLUTION

5 STAGES OF LAND PLANT EVOLUTION

5 STAGES OF LAND PLANT EVOLUTION

5 STAGES OF LAND PLANT EVOLUTION

What do you conclude from these data?

Why have angiosperms been so successful compared to gymnosperms?

Why have angiosperms been so successful?Adaptations to dry landRapid reproduction cycle & Early maturity

Flowers

 with

Well protected and well-nourished seedsEfficient seed dispersal mechanismsEfficient pollinationRecall the evolution of sperm transfer

Water

Air

(wind)

Animals especially

Insects

But first animals on land were arthropods

.

First

insect fossils ~ 470

mya at the same time as the first land plants colonized land.First flying insects ~325 mya.

Major diversification of insects (bees, flies, butterflies & moths) ~150 mya occurred along with the radiation of flowering plants

Phylum Angiosperms ( Flowering Plants)Two major classes

Monocotylendonae

Eudicotyledonae

Types of Flowers

Complete Flowers

(Perfect Flowers)= flowers with all

of the usual male and female parts

Double Fertilization

Triploid Endosperm (3n)

Fruit Formation

SEEDSEu

Types of Flowers Cont’.Incomplete Flowers (Imperfect Flowers) =Flowers with one or more basic parts missing

e.g.

Pistillate flowers

have only female pistile.g. Staminate flowers have only male stamen

Corn with incomplete flowers

Flower SymmetryRadial Symmetry (Circular & disk-like)

Line through the center in any direction forms identical halves. (Attracts general pollinators)

Tallest FlowerHasRadial symmetry

“Corpse Flower”

Amorphophallus titanum

Largest BlossomRafflesia arnoldii

Flower SymmetryBilateral SymmetryLine through the center in one direction can produce mirror images.

(These flowers

attract

specific pollinators)

Composite Flowers = Flowers grouped together into clusters to produce a showy display

Head of a sunflower

PollinationWind Pollination –earliest pollination Characteristics of wind pollinated flowers

Unisexual flowers—encourages outbreeding

Monoecious

= corn, oak, melonsDioecious= willows, poplars, maples, spinach, asparagus

Wind pollination in angiosperms (grasses)

Characteristics of wind pollinated flowers:

Small inconspicuous

Without petals

No

scent

or nectar

Large quantity of pollen produced

Animal PollinationMany types of animals involved:85% of flowers pollinated by insects (bees, butterflies, beetles, flies, ants); they get pollen and nectar.

Birds and a few small mammals especially bats

Less pollen needs to be produced than in wind pollination

Flowers are bisexual—increases efficiency

Generalist vs. Specialist StrategiesGeneralist

Flowers

—attract many pollinators

Specialist—attracts only one pollinatorDisadvantage –flower and pollinator are dependent upon one anotherBenefit for plant—prevents waste of pollen & nectar for inefficient pollinationBenefit for pollinator—monopoly of food source

The Co-Evolution of Flowers and their Pollinators

Attracting PollinatorsColor & UV & electric patternsNectar guides—lines of color that “guide” the pollinator to the nectaries (glands that produce the sugar water)Fragrance—scent glands

Sex

Bee FlowersFlowers open during dayBees visit many speciesSome flowers are specialized

only for bees

Buzz Pollination

Some bee species grab tubular anthers & vibrate flight muscles and shake the pollen out of pore at

the end.

Nectar Guides

Ultraviolet Light Patterns

Dandelion

Ultraviolet Light Patterns

Silverweed

SexFlower that mimics female bees by color and scent to attract male bees.

Bee orchid

Bird Flowers (e.g. hummingbird) Color red or orangeProduce lots of nectarFlowers large and shaped as tubes or funnels, cups or flasks.

Lack odor

Bat FlowersNocturnal flowersPale colorStrong scent

Bats with long

Nose and tongue. Some hover, some don’t

Fly FlowersFlies are second most common pollinatorsSmell is primary attractant

Color yellow, green, white, can be mottled and look & smell like rotting meat

Butterfly FlowersDiurnal Bright colorsSmell modest

Petals fused

into long tubes

for proboscis

Moth FlowersFlowers are nocturnalPale color

Strong sweet smell

Petals fused into long tubes for long proboscis

The case of the hawk moth and the iris

Hawkmoths & the S. African Iris

Hawkmoths are important pollinators!

S. African Iris produces nectar inside

a flower tube as a reward for pollinators.The ‘flower tube’ can vary in length.How does the Hawkmoth pollinate?...

How do hawkmoths pollinate S. African iris?

Hawkmoths stick their long

tongues

inside the flower tube to collect the nectar. When their tongue is inside, the the pollen from the stigma sticks to the head of the hawkmoth.When they visit a new flower, they

transfer the pollen from previous plant visits.

Tongue

length

Flower tube

length

Distribution of flower tube length

Distribution of moth tongue lengths

AB

C

Short

flower tube length

Long

Q

uestion :

w

hat

kind of selection do you think hawkmoth tongue length will have on flower tube length?

Other Pollinators:Mouse