Chapter 23

angiosperms contain the greatest number living species 257,000

called magnolilphyta

Monocots

Changing concepts about early angiosperms

The point is that we must not think about evolution as a linear progression forward and upward with each new group leaving the previous ones behind

in most angiosperm carpels, the edges of sporophyll primordia crowd against each other and grow shuts sometimes leaving a visible suture, sometimes closing so completely that no sign of a seam remains

called a closed carpel

double fertilization is universal in flowering plants

primitively vesselless

basal angiosperms

Primitively vesselless

having wood without vessels

about 100 years ago C.E. Bessy developed the hypothesis of the ranalean flower

a magnolia flower was thought to be relictual

this flower is known to be generalized that is it has all parts and is arranged spirally

many paleobotanist and taxonomists believe that the transition from gymnosperm to angiosperm occurred during the jurassic and lower cretaceous periods of the mesozoic era

the earliest leaf fossils definitely considered to be those of angiosperms are from the lower cretaceous period approx. 130 million years ago

the oldest wood that seems to be from an angiosperm comes from the Aptian Epoch 125 million years ago from japan

much attention is now being given to gymnosperms of the jurassic and Triassic period and the focus is centering on cycadophytes and glossopterids

Classification of Flowering plants

magoliophyta is a large group with many families, genera, and species that it is rare fro an individual taxonomist to attempt to study and classify the entire group

soon after their origin flowering plants began to follow two distinct lines of evolution and currently almost angiosperms are classified as monocots or eudicots

no single character always distinguishes a monocot from a eudicot

their leaves have parallel veins because the leaves are elongate and strap shaped

flowers of monocots have their parts arranged in groups of threes

three sepals

three petals

three stamens

three carpels

Eudicots have two cotyledons and reticulate venation in the leaves vascular bundles occur in only one ring in the stem

the monocot/eudicot divergence did not occur right away

early angiosperms diverged into several clades now called basal angiosperms

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Basal angiosperms

living descendants of several groups that originated while angiosperms were still a young clade

nymphaceaceae are water lilies

they are small soft-bodied herbs with vascular bundles scattered like those in monocots and they completely lack any wood

stems must be kept underwater

magnolia flowers have numerous stamens and carpels are not fused together into a pistil as occurs in almost all monocots and eudicots

being on land would kill them

flowers are pollinated by animals

eudicots have three germination pores

other magnoliids are laurels and avocado and pepperomias

widely believed to have arisen from early angiosperms approximately 80 to 100 million

because all monocots lack ordinary secondary growth and wood their ancestors were probably herbs with either no vascular cambium or little cambial activity

the perianth members are called tepals

in the evolutionally lines of broadleaf monocots such as palms, philodendrons and dieffenbachias

Hydrocharis, Najas, and Hydrilla are found in swamps and marshes

most often these plants are found submerged

although many species retain a large number pf [;isomorphic features others have become highly modified in response to the unusual selection pressures associated with an aquatic habitat

sea grasses grow completely underwater in the ocean

they have no transportation and thus mutations that result in the loss of stomata are not selectively disadvantageous

do not waster carbon and energy by producing fibers that are not needed for support

In most alismatales flowers are large and showy

Liliales

defined broadly as a large group with many highly derived families

it was defined as the petaloid monocots those with large colorful flowers

DNA evidence indicates this is a smaller clade with 11 families and 1300 species

Asparagales

large clade

many families

many species

and many types of biology

most form nectaries in an unusual way

carpels fuse side by side starting at their bases the fused sides being called septa

they do not fuse all the way up to the style however and the open areas secrete nectar these are septal nectaries

extremely diverse in morphology

the orchidaceae is the largest and most divers family of asparagales

commelinoid monocots

four orders of monocots are known as the commelinoid monocots

epiticilar wax

Arecales

contains familiar plants

palms

has solitary trunk

leaves of palms always occur only near the shoot apex never distributed along the length of the stem

all species have simple leaves

leaves are torn by the wind into a pinnate pattern or palmate pattern

Poals

grass family

cattails and bromeliads

8000 species

include most foods that we eat

all grasses are wind pollinated

sepals and petals are of little importance

Eudicots

sedges and rushes

bromeliaceae contains tropical epiphytes

Zingiberales

house plants

maranta, calathea, canna, and gingers

banana is also a species

showy flowers

need to be pollinated by insects

larger group than monocots

more diverse than monocots

Basal Eudicots

Ranuculaceae with flowers that have little fusion

poppy family, Papaveraceae is well known for their ornamental species

hamamelids

once thought to be basal angiosperms

contains many staminate flowers

Caryophyllales

anthocyanin pigments

has water soluble pigments called betalains

nucleus cells proliferate and from a nutrient tissue called perisperm which surrounds the developing embryo

postulated to have arisen from ancestors similar to ranuculacea

Santales

small order

highly modified

parasitic plants

appears to be an ordinary tree but roots attach to other roots and parasitizes them

Rosid Clade

named after the order rosales

very diverse in every way

consists of several small orders and two big groups

two large clades of rosins are the abides

then there is the malvids

the two clade contain 100 families

none of them has ant highly relictual features found in many basal angiosperms

pinnately compound leaves

this is an ancestral condition

roses are not considered typical they are a large group of many

rose family is not also an evolutionary sense but also economically

Fabaceae are the lentils and peanuts aka its the legume family

many species have nodules

Astrid Clade

clade of the eudicots

large clade

contains plants like the sunflower, periwinkle and petunia and moving glory

they have sympetalous flowers their flowers are fused together into a tube

they always have a few stamens

stamens alternate with petals

astrids exploit very specialized pollinators that recognize complex floral patterns and such plants could not evolve before derived

they have iridoid compounds which are rarely outside this group

two orders are lamiids and campanulids

many are importantly medically

apocynaceae the oleander family,

extracted vinblastine and vincristine

two important anticancer drugs

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