Plant Diversity II

The gametophytes of seed plants are microscopic. They develop within the walls of spores that are retained within tissues of the parent sporophyte. This arrangement protects the developing gametophyte from __

environmental stress and enables it to obtain nutrients from the sporophyte

Ferns and other close relatives are ___;

homosporous

seed

plants are ____

heterosporous

Homosporous

plants produce one kind of spore, which usually

produces a bisexual gametophyte

Heterosporous

plants produce two types of spores, which

develop into either male or female gametophytes

Megasporangia produce megaspores that give rise to

female gametophytes and develop on modified leaves called megasporophylls

Microsporangia produce microspores that give rise to

Male gametophytes and develop on microsporophylls

An ovule consists of a

megasporangium, megaspore, and one or more protective integuments

Gymnosperm megasporangia have__ integument

one

Angiosperm megasporangia usually __ integuments

two

A microspore develops into a __ that consists of a male gametophyte enclosed within the pollen wal

pollen grain

Pollination

The transfer of pollen to the part of a seed plant containing the ovules

A germinated pollen grain produces a pollen tube that

carries sperm into the ___ gametophyte

female

Pollen eliminates the need for a film of __ and can be dispersed great distances by air or animals

water

If a sperm fertilizes the egg of a seed plant, the ovule will develop into a __

seed

A seed is a ___, along with its food supply, packaged in a protective coat

sporophyte embryo

Seeds provide some evolutionary advantages over spores

• They may remain dormant for days to years, until conditions are favorable for germination

• They have a supply of stored food

• They may be transported long distances by wind or an animal

Origins of characteristics found in living seed plants

date back to the ___

late Devonian period (380 million years ago)

A 360-million-year-old fossil from the genus ___

provides the earliest evidence of seed plants

Elkinsia

Living seed plants can be divided into two clades

gymnosperms and angiosperms

Gymnosperms appear early in the fossil record,

about

305 million years ago

Gymnosperms means

naked seeds

Gymnosperms seeds are exposed on___ that form cones

sporophylls

Angiosperm seeds are found in ___, which are mature ___

fruits, ovaries

Gymnosperms dominated terrestrial ecosystems during the ___ era

Mesozoic era, 252 to 66 million years ago

The gymnosperms consist of four phyla

• Cycadophyta (cycads)

• Ginkgophyta (one living species: Ginkgo biloba)

• Gnetophyta (three genera: Gnetum, Ephedra, Welwitschia)

• Coniferophyta (conifers: pine, fir, and redwood)

Phylum Cycadophyta Have

large cones and palmlike leaves

Unlike most seed plants Cycadophyta have

flagellated sperm

Phylum Ginkgophyta consists of a single living species ___

Ginkgo biloba

Like the cycads Phylum Ginkgophyta also have ___.

flagellated sperm

Phylum Gnetophyta

Species vary in appearance, and some are tropical, whereas others live in deserts

Phylum Gnetophyta is comprises three genera

Gnetum

Ephedra

Welwitschia

Phylum Coniferophyta, this phylum is the __ of the gymnosperm phyla

largest

Most ___ species have woody cones, but a few have fleshy cones

Coniferophyta

Most __ are evergreens and can carry out photosynthesis all year round

conifers

The pine tree is a ___ sporophyte producing _ in modified leaves, the male and female cones

sporophyte, sporangia

pine tree pollen cones are small and consist __ that bear microsporangia

microsporophylls

pine tree cells ___ undergo meiosis to produce haploid microspores (pollen grains) inside the microsporangia

microsporocytes

Pine trees Ovulate cones are larger and consist of __ bearing megasporangia (ovule)

megasporophylls

Within each ovule, ___ undergo ___ to produce ___ megaspores which develop into __ gametophytes

megasporocytes , meiosis , haploid , female

__ gametophytes are retained within the megasporangia

Female

Fossil evidence suggests that angiosperms originated about __ million years ago and diversified over a 20- to 30-million-year period

140

The earliest pollen fossils with angiosperm characteristics are ___ million years old

130

Early fossils of larger flowering plant structures are about __ million years old

125

All angiosperms are classified in a single phylum, __

Anthophyta

The __ is an angiosperm structure specialized for sexual reproduction

flower

A flower is a specialized shoot with up to four types of modified leaves called floral organs:

• Sepals, which enclose the flower

• Petals, which are often brightly colored to attract pollinators; wind-pollinated flowers generally lack brightly colored parts

• Stamens, the male reproductive organs

• Carpels, the female reproductive organs

A stamen consists of a stalk called a __ , with a sac called an __

filament, anther

A carpel consists of an __ at the base of a _leading up to a sticky _, where pollen is received

ovary, style, stigma

The ovary contains the __ within the ovule(s)

female gametophyte(s)

The term __can be used to refer to a single carpel or two or more fused carpels

pistil

The flower of the sporophyte is composed of both male and female structures

• Male gametophytes are contained within pollen grains produced by the microsporangia of anthers

• The female gametophyte, or embryo sac, develops within an ovule contained within an ovary at the base of a stigma

A pollen grain that has landed on a stigma __, and the pollen tube of the male gametophyte grows down to the ovary

germinates

The ovule is entered through a pore called the

micropyle

Double fertilization occurs when the pollen tube discharges __

two sperm into the female gametophyte within an ovule

• One sperm fertilizes the egg

• The other combines with two nuclei in the central cell of the female gametophyte and initiates development of food-storing endosperm, a triploid structure that nourishes the developing embryo

Within a seed, the embryo consists of a root and one or two seed leaves called ___

cotyledons

Basal angiosperms

§include the flowering plants belonging to the oldest lineages

• These include water lilies and star anise

Monocots and Eudicots

Most angiosperms are divided into two main groups: monocots (one cotyledon) and Eudicots (two cotyledons)

Monocots

• About one-quarter of angiosperms, about 70,000 species, are monocots

• The largest groups are the orchids, grasses, and palms

Eudicots

• More than two-thirds of angiosperms, about 170,000 species, are eudicots

• Eudicots include the large legume family and the economically important rose family

Angiosperm Life Cycle