Biology Chapter 30 & 31

Gymnosperms

- A seed plant with seeds not enclosed in an ovary; conifers are gymnosperms - encompass four of the five lineages of seed plants

What differentiates charophytes from land plants?

- Land plants have multicellular haploid and diploid stages, unlike the charophytes. - land plant have diploid embryos - As land plants have evolved, the trend has been toward more embryo protection and a smaller haploid stage in the life cycle.

What are the five groups of seed plants? Which ones do gymnosperms encompass?

- The four groups of gymnosperms are the coniferophytes, cycadophytes, gnetophytes, and ginkgophytes - The fifth lineage of seed plants is the angiosperms.

As an adaptation to living on land, how are most plants protected from desiccation/drying out?

- by a waxy surface material called the cuticle that is secreted onto parts that are exposed to the air - the cuticle is relatively impermeable, preventing water loss

Land plants minimize the effects of mutation by...

- carrying two copies of every gene - their bodies are diploid, meaning that deleterious recessive mutations are masked

Horsetail What do their sporophytes consist of?

- consist of ribbed, jointed, photosynthetic stems that arise from branching underground rhizomes with roots at their nodes -

coniferophytes

- ex: Conifers (including pines, spruces, firs, yews, redwoods, and others) - Heterosporous seed plants. Sperm not motile; conducted to egg by a pollen tube. Leaves mostly needlelike or scalelike. Trees, shrubs. About 68 genera. Many produce seeds in cones.

cycadophytes

- ex: Cycads - Heterosporous. Sperm flagellated and motile but confined within a pollen tube that grows to the vicinity of the egg. Palmlike plants with pinnate leaves. Secondary growth slow compared with that of the conifers. Ten genera. Seeds in cones.

ginkgophytes

- ex: Ginkgo - Heterosporous. Sperm flagellated and motile but conducted to the vicinity of the egg by a pollen tube. Deciduous tree with fan-shaped leaves that have evenly forking veins. Seeds resemble a small plum with fleshy, foul-smelling outer covering. One genus.

gnetophytes

- ex: Gnetophytes - Heterosporous. Sperm not motile; conducted to egg by a pollen tube. The only gymnosperms with vessels. Trees, shrubs, vines. Three very diverse genera (Ephedra, Gnetum, Welwitschia).

In what environments are bryophytes mostly found?

- moist places, both in the tropics and temperate regions - commonly seen in damp forest floors and by stream beds

What beneficial symbiotic relationship is found in many bryophytes? Why does this relationship occur?

- mycorrhizal associations or a symbiotic association between fungi and the roots of a plant - enhances water uptake bc early terrestrial plants were limited in gas and water availability

Whisk ferns Where do they occur? What does their sporophytic generation consist of? Why is it surprising that they are monophyletic with ferns? With what other organism do the gametophytes form a symbiotic relationship?

- occur in the tropics and subtropics - the sporophytic generation consists merely of evenly forking green stems without roots - bc of their simple structure - gametophytes form symbiotic associations with fungi, which furnish their nutrients

What is another name for plants in the bryophyte group and why? What is this group comprised of?

- plants in this group are also called nontracheophytes because they lack the transport cells called tracheids - comprised of liverworts, mosses, and hornworts

What is special about the bryophyte gametophyte?

- small but specialized for light capture and photosynthesis - water and nutrients are transported throughout the gametophyte via simple conducting cells

Ferns

- the most abundant group of seedless vascular plants - they may be the closest relatives of the seed plants Ferns and their relatives have a large and conspicuous sporophyte with vascular tissue. Many have well-differentiated roots, stems, and leaves (fronds). The gametophyte generation is small and green, but lacks vascular tissue.

gametangia

A cell or organ in which gametes are formed.

reproductive cycle

A consistent feature in the evolution of plants is a reduction in the size of the gametophyte and a corresponding increase in dominance of the sporophyte generation.

haplodiploidy

A phenomenon occurring in certain organisms such as wasps, wherein both haploid (male) and diploid (female) individuals are encountered.

pollen tube

A tube formed after germination of the pollen grain; carries the male gametes into the ovule.

What is the difference between gymnosperms and angiosperms?

Although both gymnosperms and angiosperms produce seeds, only the angiosperms produce flowers and fruits

_______ _______ is the closest living relative to the earliest angiosperms

Amborella trichopoda

flowers

Each flower originates as a primordium that develops into a bud at the end of a stalk called a pedicel. The pedicel expands slightly at the tip to form the receptacle, to which the remaining flower parts are attached.

What are flowers considered to be?

Flowers are considered to be modified stems bearing modified leaves

fruit

Fruits are most simply defined as mature ovaries (carpels). During seed formation, the ovary begins to develop into fruit

How does this contrast with seedless plants?

In contrast to the seedless plants, the whole male gametophyte, rather than just the sperm, moves to the female gametophyte.

primordium

In plants, a bulge on the young shoot produced by the apical meristem; primordia can differentiate into leaves, other shoots, or flowers.

stomata

In plants, a minute opening bordered by guard cells in the epidermis of leaves and stems; water passes out of a plant mainly through the stomata.

gametophyte

In plants, the haploid (n), gamete-producing generation, which alternates with the diploid (2n) sporophyte.

What did land plants have to develop to survive?

Land plants had to develop mechanisms to avoid water loss, and protection from the harmful effects of solar radiation.

A common ancestor gave rise to two clades:

One clade diverged to produce a line of ferns and horsetails The other diverged to yield another line of ferns and whisk ferns—ancient-looking plants.

Seeds are an important adaptation in at least four ways:

Seeds maintain dormancy under unfavorable conditions and postpone development until better conditions arise. Seeds afford maximum protection to the young plant at its most vulnerable stage of development. Seeds contain stored food that allows a young plant to grow and develop before photosynthetic activity begins. Perhaps most important, seeds are adapted for dispersal, facilitating the migration of plant genotypes into new habitats. Germination cannot take place until water and oxygen reach the embryo. Fire, heavy rains, or passage through an animal's digestive tract may be required for germination in some species.

What part develops into a fruit?

The carpel, a modified leaf that encapsulates seeds, develops into the fruit, a unique angiosperm feature

seeds

The embryo is protected by an extra layer or two of sporophyte tissue called the integument, creating the ovule (figure 31.1). Within the ovule, meiosis occurs in the megasporangium, producing a haploid megaspore. The megaspore divides by mitosis to produce a female gametophyte carrying the female gamete, an egg. The egg combines with the male gamete, a sperm, resulting in the zygote. The single-celled zygote divides by mitosis to produce the young sporophyte, an embryo. Seeds also contain a food supply for the developing embryo. During development, the integuments harden to produce the seed coat, which protects the embryo. The seed is easily dispersed The integuments—the outer cell layers of the ovule—develop into a relatively impermeable seed coat, which encloses the seed, which contains a dormant embryo and stored food

Angiosperms

The flowering plants, one of five phyla of seed plants. In angiosperms, the ovules at the time of pollination are completely enclosed by tissues

What does the name gymnosperm mean and why is this significant?

The name gymnosperm means "naked seed" because the seed develops on the surface of the scale.

sporophyte

The spore-producing, diploid (2n) phase in the life cycle of a plant having alternation of generations.

T or F: Bryophytes are the closest living descendants of the first land plants

True

T or F: Terrestrial plants are exposed to higher intensities of UV irradiation than aquatic algae, increasing the chance of mutation.

True

mycorrhizal associations

a symbiotic association between fungi and the roots of a plant

One of the most significant evolutionary events in the billion-year-old history of the green plants is the...

adaptation to terrestrial living

What aspect of bryophytes indicates their aquatic origin?

bryophytes require water to reproduce sexually (the sperm must swim to the egg) tracing back to their aquatic origins

What are the four types of gymnosperms?

coniferophytes, cycadophytes, gnetophytes, and ginkgophytes

Bryophytes

continue to learn more

Ferns

continue to learn more

All land plants have both haploid and diploid generations, but there is an evolutionary shift toward a dominant ________ generation

diploid

From what species did and plants evolve?

from green algae

The haploid gametophyte produces _______ by mitosis. Consequently, the gametes (egg cells and sperm cells) are also ________. When two gametes fuse, the zygote they form is _______ and is the first cell of the next __________ generation.

gametes haploid diploid sporophyte

Spores are the first cells of the _________ generation. Spores divide by mitosis, producing a multicellular, ________ _________.

gametophyte haploid gametophyte

What happen to the zygote?

grows into a diploid sporophyte by mitosis and produces sporangia in which meiosis ultimately occurs

The diploid sporophyte produces ______ ________ (not gametes) by meiosis. Meiosis takes place in structures called ________, where diploid spore mother cells (sporocytes) undergo meiosis, each producing four haploid spores.

haploid spores sporangia

They undergo ______ after both fertilization (the diploid stage) and meiosis (the haploid stage). The result is a multicellular diploid individual called the __________ and a multicellular haploid individual called the __________.

mitosis sporophyte gametophyte

A fundamental feature of land plants is that the land plant life cycle has both __________ haploid and diploid stages, a term we call __________.

multicellular haplodiplontic

Seed plants appear to have evolved from spore-bearing plants known as __________.

progymnosperms

A consistent feature in the evolution of plants is (2)

reduction in the size of the gametophyte and a corresponding increase in dominance of the sporophyte generation

Gymnosperms vary in their ___________ and ______ form.

reproduction growth

A reduction of the size of the gametophyte and gametangia seen corresponds with the increase in...

specialization for life on land

Gas diffusion into and out of a plant occurs through tiny mouth-shaped openings called ______.

stomata

Together charophytes and land plants are referred to as __________.

streptophytes

The green algae split into what two major clades?

the chlorophytes, which never made it to land, and the charophytes, which are a sister clade to all the land plants

The evolving of land plants from green algae began...

the conversion of bare ground to the rich and diverse ecosystems found on our planet today

In gymnosperms, is the ovule closed or exposed at the time of pollination?

the ovule, which becomes a seed, rests exposed on a scale (a modified shoot or leaf) and is not completely enclosed by sporophyte tissues at the time of pollination

Are their ovules enclosed at the time of pollination?

their ovules, unlike those of gymnosperms, are enclosed within diploid tissues at the time of pollination

The tissue that carries water is called ________, whereas food is carried by ______.

xylem phloem