Chapter 30 Biology Homework and Readings

Seeds of gymnosperms

"naked" seeds exposed on sporophylls that usually form cones (angiosperm seeds are enclosed in chambers that mature into fruits)

Eudicots

"true dicots" -large clade that arise from dicots

Pollen grain

-Consists of a male gametophyte enclosed within the pollen wall (wall's outer layer is made of molecules secreted by sporophyte cells) -developed from a microspore

Of the 10 plant phyla, 4 are gymnosperms

-Cycadophyta -Ginkgophyta -Gnetophyta -Coniferophyta

Double fertilization

-One fertilization event produces a zygote and the other produces a triploid cell -unique to angiosperms

Within the petals are 2 types of fertile floral organs that produce spores

-Stamens -Carpels

When carboniferous period gave way to the Permian, the climate became much drier. What happened to plant species as a result?

-The lycophytes, horsetails, and ferns that dominated Carboniferous swamps were largely replaced by gymnosperms (which were better suited to the drier climate)

Wood

-absent in all living seedless plants -consist of tough-walled xylem cells

Stigma

-at the tip of the carpel -receives pollen

All seed plants have reduced...

-gametophytes -heterospory -ovules -pollen

Seed plant evolution has included 3 key reproductive adaptations

-miniaturization of their gametophytes -advent of the seed as a resistant, dispersible stage in the life cycle -appearance of pollen as an airborne agent that brings gametes together

Flower may have 1 or more carpels

-multiple carpels can be fused into one structure -pistil refers to a single carpel or 2 or more fused carpels

Ovulate cones structure

-scales are compound structures composed of both modified leaves (megasporophylls bearing megasporangia) and modified stem tissue -within each megasporangium, megasporocytes undergo meiosis and produce HAPLOID megaspores inside the ovule -surviving megaspores develop into female gametophytes, which are retained within the sporangia

Pollen cones structure

-scales are modified leaves (microsporophylls) that bear microsporangia -within each microsporangium, cells called microsporocytes undergo meiosis (PRODUCING HAPLOID MICROSPORES) -Each microspore develops into a pollen grain containing a male gametophyte

In conifers, the 2 types of spores are produced by separate cones

-small pollen cones -large ovulate cones

Flower structure

-specialized shoot that can have up to 4 types of modified leaves called floral organs (sepals, petals, stamens, and carpels) -in all angiosperms, the sepals and petals are sterile floral organs

Evolutionary innovation in seed plants

-tiny gametophytes can develop from spores retained within the sporangia of the parental sporophyte (can protect from environmental stresses)

Spores vs seeds

-usually single-celled (seeds are multicellular -consisting of an embryo protected by a layer of tissue, the seed coat -seeds can remain dormant for a length of time after being released from the parent plant (spores have shorter lifetimes) -seeds have a supply of stored food (spores do not)

Angiosperm megasporangia

2 integuments

Ovules are found within structure

A Ovules are housed within ovaries.

Consider the seed shown in this figure. Select the correct description of this seed.

A seed includes contributions from three separate generations of plants. In addition to a sporophyte embryo, a seed has a seed coat derived from the integuments of the "grandparent" sporophyte and a food supply derived from the tissues of the "parent" gametophyte.

All angiosperms are classified in a single phylum

Anthophyta

All seed plants

Are heterosporous All seed plants produce separate male and female spores.

Conifers

Cone-bearing plants Is a gymnosperm

The reduced adaptation helped seed plants...

Cope with conditions such as drought and exposure to UV radiation in sunlight -also freed seed plants from requiring water for fertilization, enabling reproduction under a broader range of conditions than in seedless plants

The embryo is ______.

Diploid

The sporophyte generation is...

Diploid

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

Diploid sporophyte

Which of these structures contains a male gametophyte?

E Pollen grains contain the male gametophytes.

What are the main components of a mature gymnosperm seed?

Embryo Seed coat Food supply

Embryo sac

Female gametophyte In the ovary Consists of only a few cells, one of which is the egg

Megaspores

Female gametophytes

After fertilization of the ovule, the __________ develops into the embryo of the mature seed

Fertilized egg

Flagella in gymnosperms

Flagella have been lost in the sperm of most gymnosperms and all angiosperms

Nonvascular plants and seedless vascular plants (ex. ferns)

Free-living gametophytes release flagellated sperm that swim through a film of water to reach eggs

Mosses and other bryophytes have life cycles dominated by _______________, whereas ferns and other seedless vascular plants have __________________-dominated life cycles

Gametophytes ... Sporophyte

Each male gametophyte has 2 haploid cells

Generative cell that divides (forming 2 sperm) Tube cell (produces a pollen tube)

Exant seed plants form 2 sister clades

Gymnosperms and angiosperms

Life cycle of a gymnosperm

Gymnosperms undergo alternation of generations, alternating between the diploid sporophyte and the haploid gametophyte. In conifers, the mature sporophyte produces two types of cones, in which diploid microsporangia and megasporangia develop. A cell in microsporangia divides by meiosis to form haploid microspores. The microspores then divide by mitosis to form haploid male gametophytes (pollen grains). Inside megasporangia, a diploid mother cell divides by meiosis to form a haploid megaspore. The megaspore then divides by mitosis to form the haploid female gametophyte, which produces eggs. The pollen grains produce sperm, one of which fertilizes one of the eggs, resulting in a diploid embryo inside a seed. Once the seed germinates, it forms a diploid seedling (sporophyte) that will eventually develop into a mature diploid sporophyte.

The gametophyte generation is...

Haploid

The megaspore is...

Haploid

Ferns and other close relatives of seed plants are

Homosporous, then seed plants evolved to be heterosporous

Cross-pollination

In angiosperms, is the transfer of pollen from an anther of a flower on one plant to the stigma of a flower on another plant of the same species -enhances genetic variability

Filament

In the stamen, it is the stalk

After fertilization of the ovule, the ________ develops into the seed coat

Integument

Petals

Interior to the sepals

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

It functions as a haploid food reserve.

If a pollen grain germinates (begins growing)...

It gives rise to a pollen tube that discharges sperm into the female gametophyte within the ovule

Integument

Layer of sporophyte tissue that envelops and protects the megasporangium

Ovary

Located at the base of the carpel Contains one or more ovules -As in gymnosperms, each angiosperm ovule contains a female gametophyte

Microspores

Male gametophytes

After fertilization of the ovule, the ________ develops into the food supply of the mature seed

Megaspore

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

Megaspores or microspores Review the life cycles of a pine tree and an angiosperm, respectively. In both life cycles, meiosis produces m

Carpels

Megasporophylls; they produce megaspores that give rise to female gametophytes -"container" in which seeds are enclosed -key structure that distinguishes angiosperms from gymnosperms

Gymnosperms were most abundant during the

Mesozoic

Stamens

Microsporophylls -produce microspores that develop into pollen grains containing male gametophytes -Consists of: filament, anther

From ovule to seed in a gymnosperm

Pollen grain (n) Integument (2n) Female gametophyte (n) Egg nucleus (n) Discharged sperm nucleus (n) Male gametophyte within a germinated pollen grain (n) Megasporangium (2n) Female gametophyte tissue/food supply (n) Embryo (2n)

Micropyle

Pore in the integuments of the uvule, and discharges 2 sperm cells into the female gametophyte (embryo sac)

Fruit

Resulting from when seeds develop from ovules after fertilization and the ovary wall thickens -protect seeds and aid in their dispersal

How are seed plants unique in comparison to seedless plants?

Seed plants retain the megasporangium within the parent sprophyte

Angiosperms

Seed plants with the reproductive structures called flowers and fruits

Pine tree is the sporophyte

Sporangia are located on scalelike structures packed densely in cones

Cotyledons

Sporophyte embryo with a rudimentary root and one or two seed leaves developed from the zygote

Gymnosperm megasporangia

Surrounded by one integument

Until advent of seeds, ______ was the only protective stage in any plant life cycle

The spore

If sperm fertilizes an egg of a seed plant...

The zygote grows into a sporophyte embryo

Why did gymnosperms thrive as the climate dried?

They have the key terrestrial adaptations found in all seed plants, such as seeds and pollen -some gymnosperms were particularly well suited to arid conditions because of thick cuticles and relatively small surface areas of their needle-shaped leaves

Endosperm

Tissue rich in starch and other food reserves that nourish the developing embryo -triploid central cell of the female gametophyte develops into endosperms

Pollination

Transfer of pollen to the part of a seed plant that contains the ovules

Flower

Unique angiosperm structure that is specialized for sexual reproduction -Insects or other animals transfer pollen from one flower to the next (makes pollination more directed than the wind-dependent pollination of most species of gynopserms) -some angiosperms are wind-pollinated (ones that occur in dense populations

Sepals

Usually green and enclose the flower before it opens (rosebud) -at the base of the flower

Anther

Where pollen is produced in a stamen

Ovule

Whole structure: megasporangium, megaspore, and their integument(s) -inside each ovule, a female gametophyte develops from a megaspore and produces one or more eggs

Human survival literally depends on the produce of

angiosperms Angiosperms are the source of our major food crops, including rice, wheat, maize, and barley. They also provide cotton and linen, and medicines such as digitalis and codeine. Rubber, coffee, chocolate, and aromatic oils come from flowering plants. Woods such as oak, cherry, and walnut are derived from angiosperms.

A stamen consists of

anther and filament

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

archegonia ... egg

Which of these is unique to flowering plants?

double fertilization In flowering plants one sperm nucleus fertilizes the egg and the other sperm nucleus fuses with two other nuclei found within the ovule, thus forming triploid endosperm.

In gymnosperms, megaspores develop into

female gametophytes

Angiosperms are different from all other plants because only they have

flowers

In the pine, microsporangia form _____ microspores by _____

haploid ... meiosis

In pines, an embryo is a(n)

immature sporophyte

Style

leads from the stigma to the ovary

In pine trees, pollen grains get to the ovule via the

micropyle

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

one

Which of the following contains multiple gymnosperm ovules? megasporangium integument ovulate cone megaspore

ovulate cone An immature ovulate cone contains multiple ovules. An ovulate cone will become a mature gymnosperm cone after all of the ovules mature into seeds.

Unlike most angiosperms, grasses are pollinated by wind. As a consequence, some unnecessary parts of grass flowers have almost disappeared. Which of the following parts would you expect to be most reduced in a grass flower?

petals Petals play a role in attracting pollinators.

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

Dicots

species with 2 cotyledons

Monocots

species with one cotyledon

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

A carpel is composed of

stigma, style, and ovary

Which of the following is found inside a pollen grain? the sporophyte the megaspore the female gametophyte the male gametophyte

the male gametophyte A pollen grain contains the male gametophyte. Pollination of the ovule begins the process of fertilization, which results in the merging of the haploid male and female gametophytes to form a diploid zygote.