Ch. 30 Plant Diversity II: The Evolution of Seed Plants

Seed plants originated about \____ years ago

360 million

A seed consists of an \______ and \______ surrounded by a protective coat.

Embryo; nutrients

The following are common to all seed plants:

-reduced gametophytes
-heterospory
-ovules
-pollen

What are the advantages of reduced gametophytes?

The gametophytes of seed plants develop within the walls of spores that are retained within tissues of the parent sporophyte
-nourished and protected

The ancestors of seed plants were likely \_______, while seed plants are \________.

homosporous;heterosporous

Megasporangia

produce megaspores that give rise to female gametophytes

Microsporangia

produce microspores that give rise to male gametophytes

An ovule consist of:

a megasporangium, megaspore, and one or more protective integuments

Gymnosperm megaspores have \__ integument.

1

Angiosperm megaspores usually have \__ integuments.

2

Microspores develop into \______, which contain the male gametophytes

pollen grains

Pollination:

the transfer of pollen to the part of a seed plant containing the ovules
-pollen eliminates the need for a film of water and can be dispersed great distances by air or animals

If a pollen grain germinates, it gives rise to a pollen tube that discharges sperm into the female gametophyte within the \______.

ovule

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

sporophyte embryo

A seed develops from the \________.

whole ovule

Evolutionary advantages of seeds over spores:

-they may remain dormant for days to years, until conditions are favorable for germination
-seeds have a supply of stored food
-they may be transported long distances by wind or animals

Gymnosperms means:

"naked seeds"

Gymnosperms seeds are exposed on \______ that form cones

sporophylls

Angiosperm seeds are found in \_______.

fruits

Fossil evidence reveals that by the late Devonian period some plants, called \_________, had begun to acquire some adaptations that characterize seed plants

progymnosperms

Living seed plants can be divided into two clades:

gymnosperms and angiosperms

\__________ appear early in the fossil record about 305 million years ago and dominated Mesozoic (251-65 Mya) terrestrial ecosystems

Gymnosperms

\________ were better suited than nonvascular plants to drier (and cooler) conditions

Gymnosperms

\______ began to replace gymnosperms near the end of the Mesozoic

Angiosperms

Conifers:

cone-bearing gymnosperms

Four phyla of gymnosperms:

-Cycadophyta (cycads)
-Gingkophyta (one living species: Ginkgo biloba)
-Gnetophyta (three genera: Gnetum, Ephedra, Welwitschia)
-Coniferophyta (conifers: pine, fir, redwood, etc.)

Phylum Cycadophyta

Individuals have large cones and palmlike leaves
These thrived during the Mesozoic, but relatively few species exist today

Phylum Ginkgophyta

This phylum consists of a single living species, Ginkgo biloba

It has a high tolerance to air pollution and is a popular ornamental tree

Phylum Gnetophyta

This phylum comprises three genera
-Species vary in appearance, and some are tropical whereas others live in deserts

Phylum Coniferophyta

This phylum is by far the largest of the gymnosperm phyla
-Most conifers are evergreens and can carry out photosynthesis year round

Three key features of the gymnosperm life cycle are:

-dominance of the sporophyte generation
-development of seeds from fertilized ovules
-the transfer of sperm to ovules by pollen

The pine tree is the sporophyte and produces \______ in male and female cones

sporangia

Small cones:

produce microspores called pollen grains, each of which contains a male gametophyte

Larger cones:

contain ovules, which produce megaspores that develop into female gametophytes

How many years is it from cone production to mature seed?

3

The reproductive adaptations of angiosperms include \______ and \_____.

flowers;fruits

What are the most widespread and diverse of all plants?

Angiosperms

Anthophyta:

phylum of angiosperms

Flower:

an angiosperm structure specialized for sexual reproduction

Four types of modified leaves on a flower

-sepals
-petals
-stamens
-carpels

Sepals:

enclose the flower

Petals:

brightly colored; attract pollinators

Stamens:

produce pollen
-consists of a stalk called the filament with a sac called an anther

Carpels:

produce ovules
-has ovary at the base and a style leading up to a stigma

Anther:

Where pollen is produced on the filament

Stigma:

where pollen is received

A fruit consists of a \_________.

mature ovary

Mature fruits can be either \_____ or \______.

fleshy; dry

In the flower male gametophytes are contained within:

within pollen grains produced by the microsporangia of anthers

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 germinates and the pollen tube of the male gametophyte \______________.

grows down to the ovary

Micropyle:

pore in which the ovule is entered

Double fertilization occurs when:

the pollen tube discharges two sperm into the female gametophyte within an ovule
-One sperm fertilizes the egg, while the other combines with two nuclei in the central cell of the female gametophyte and initiates development of food-storing endosperm

Triploid endosperm

nourishes the developing embryo

Within a seed, the embryo consists of a root and two seed leaves called \_____.

cotyledons

Angiosperms originated at least \___ million years ago

140

Angiosperms may be closely related to \________, extinct seed plants with flowerlike structures

Bennettitales

Angiosperms were divided into two main groups

-monocot
-dicot

monocot:

one cotyledon
-veins usually parallel
-vascular tissue scattered
-root system usually fibrous
-pollen grain with 1 opening
-floral organs usually in multiples of three

dicot:

two cotyledons

DNA studies suggest that monocots form a clade, but dicots are \__________.

polyphyletic

Polyphyletic:

group with no common ancestor

The clade \_______ ("true" dicots) includes most dicots

eudicot

basal angiosperms

-dicot lineage
-are less derived and include the flowering plants belonging to the oldest lineages

magnoliids

-dicot lineage
-share some traits with basal angiosperms but evolved later

Three lineages that constitute the basal angiosperms:

Amborella trichopoda, water lilies, and star anise

Three lineages that constitute the magnollids:

magnolias, laurels, and black pepper plants

More than one-quarter of angiosperm species are \________.

monocots

More than two-thirds of angiosperm species are \________.

eudicots

Eudicot:

Two cotyledons
-veins usually netlike
-vascular issue usually arranged in a ring
-taproot usually present
-pollen grain with 3 openings
-floral organs usually in multiples of four or five

Animals influence the evolution of plants and vice versa; for example:

-animal herbivory selects for plant defenses
-interactions between pollinators and flowering plants select for mutually beneficial adaptations

Clades with \_______ symmetrical flowers have more species than those with \______ symmetrical flowers.

bilaterally; radially
-likely because bilateral symmetry affects the movement of pollinators and reduces gene flow in diverging populations

Five Derived Traits of Seed Plants

-Reduced gametophytes
-Heterospory
-Ovules
-Pollen
-Seeds

What are the products of meiosis in the life cycle of a seed plant?

Megaspore or microspores

Which of these structures is a separate generation from the plant sporophyte?

A male gametophyte within a pollen grain.

Select the correct statement describing the life cycle of angiosperm

Double fertilization in the life cycle of seed plants results in the production of a diploid zygote and a triploid endosperm nucleus

In which of the following pairs do the structures play comparable roles in the plant and animal life cycles?

A plant sporophyte and an adult animal

In pines, the female gametophyte contains \_____, each of which contains a(n) \_____.

archegonia ... egg

In pines, an embryo is a(n) \_____.

immature sporophyte

In pine trees, pollen grains get to the ovule via the \_____.

micropyle

Which of these statements is true about the gametophyte tissue that surrounds the pine embryo?

It functions as a haploid food reserve.

Of the four haploid cells produced by a pine cone's megasporocyte (megaspore mother cell), \_____ survive(s).

one

In the pine, microsporangia form \_____ microspores by \_____.

haploid; meiosis

Which of these is unique to flowering plants?

double fertilization

The male gametophytes of flowering plants are also referred to as \_____.

pollen grains

In flowering plants the integuments of the ovule develop into a(n) \_____.

seed coat

A carpel is composed of \_____.

stigma, style, and ovary

In flowering plants one megaspore gives rise to \_____ nuclei

eight haploid

A stamen consists of \_____.

anther and filament

In angiosperms, pollination is the transfer of pollen grain to the \_____ of a flower on the same plant or another plant of the same species.

stigma

Where in an angiosperm would you find a megasporangium?

within an ovule contained within an ovary of a flower

A fruit is most commonly

a mature ovary

With respect to angiosperms, which of the following is incorrectly paired with its chromosome count?

megaspore-2n

Which of the following is not a characteristic that distinguishes gymnosperms and angiosperms from other plants?

alternation of generations

Gymnosperms and angiosperms have the following in common except

ovaries.

When you look at a pine or maple tree, the plant you see is a \_____.

diploid sporophyte

All seed plants \_____.

are heterosporous

The adaptation that made possible the colonization of dry land environments by seed plants is most likely the result of the evolution of \_____.

pollen

Gymnosperms were most abundant during the \_____.

Mesozoic

In gymnosperms megaspores develop into \_____ .

female gametophytes