Chapter 29

Question 1

All green algae and the land plants shared a common ancestor a little over

Answer 1

1 B Y A​

Supported by D N A sequence data.​

Collectively known as green plants.​

Not all photoautotrophs are plants.​

Red and brown algae excluded.​

Question 2

Plants had many issues to overcome on land that include

Answer 2

Water loss​

Protection from the harmful effects of the sun​

Ability to effectively disseminate gametes for production

Question 3

Fungi helped plants to colonize land by

Answer 3

make nutrients available to plants.

Question 4

The green algae split into two major clades

Answer 4

Chlorophytes – Never made it to land.​

Charophytes – Sister clade to all land plants.​

Together, charophytes and land plants are referred to as streptophytes

Question 5

Land plants …

Answer 5

Have multicellular haploid and diploid stages.​

Trend toward more diploid embryo protection.​

Trend toward reduced haploid stage.

Question 6

Protection from drying out​

Answer 6

Waxy cuticle and stomata.

Question 7

Moving water within plants

Answer 7

Bryophytes are limited in size because they lack vasculature​

Tracheophytes have specialized vascular tissue for transport over long distances through body​

Xylem to conduct water​

Phloem to transport sugars and dissolved nutrients

Question 8

Dealing with U V radiation caused mutations

Answer 8

Shift to a dominant diploid generation, meaning deleterious recessive mutations are masked

Question 9

Multicellular diploid stage – sporophyte​

Answer 9

Produces haploid spores by meiosis.​

Diploid spore mother cells (sporocytes) undergo meiosis in sporangia.​

Produce 4 haploid spores.​

First cells of gametophyte generation.

Question 10

Multicellular haploid stage – gametophyte

Answer 10

Spores divide by mitosis.​

Produces gametes by mitosis.​

Gametes fuse to form diploid zygote.​

First cell of next sporophyte generation.

Question 11

Haplodiplontic Land Plants

Answer 11

Humans and other animals have a diplontic life cycle, meaning only the diploid stage is multicellular​

All land plants are haplodiplontic; having both multicellular haploid and diploid stages​

Relative sizes of generations vary

Question 12

Bryophytes

Answer 12

Closest living descendants of the first land plants​

Called nontracheophytes​

They lack tracheids.​

Do have other conducting cells in gametophytes.

Question 13

Bryophyte Characteristics

Answer 13

Simple, but highly adapted to diverse terrestrial environments​

Approximately 16,000 species in 3 distinct clades​

Liverworts.​

Mosses.​

Hornworts.​

Gametophyte is dominant generation – small but specialized for photosynthesis​

Sporophyte grows from the surface of gametophyte – specialized for dispersing spores​

Require water for sexual reproduction, as the sperm must swim to the egg

Question 14

Liverworts (phylum Hepaticophyta)

Answer 14

Best-known are the lobed liverworts that have flattened gametophytes ​

But 80% are leafy and look like mosses.​

Form umbrella-shaped gametangia (gamete-producing structures)​

Also undergo asexual reproduction

Question 15

Mosses (phylum Bryophyta)

Answer 15

Gametophytes consist of small, leaflike structures around a stemlike axis​

Not true leaves – no vascular tissue.​

Anchored to substrate by rhizoids​

Multicellular – but not nearly the volume of water absorbed by a vascular plant root.​

Question 16

Multicellular gametangia form at the tips of gametophytes

Answer 16

Archegonia – Female gametangia.​

Antheridia – Male gametangia.​

Flagellated sperm must swim in water.

Question 17

Hornworts (phylum Anthocerotophyta)

Answer 17

Origin is puzzling – likely among the earliest land plants, yet no fossils until Cretaceous​

Photosynthetic sporophyte looks like a green horn​

Sporophyte base is embedded in gametophyte tissue from which it derives some of its nutrition​

Cells have a single large chloroplast

Question 18

Cooksonia, first known vascular land plant

Answer 18

Appeared about 420 M Y A, now extinct​

Phylum Rhyniophyta​

Only a few centimeters tall​

No roots or leaves​

Homosporous – producing only one type of spore​

Sporangia formed at branch tips

Question 19

Vascular Tissue

Answer 19

Allows for distribution of nutrients​

Xylem conducts water and dissolved minerals upward from the roots.​

Phloem conducts sucrose and hormones throughout the plant.​

Enable enhanced height and size in the tracheophytes​

Develops in sporophyte but usually not gametophyte​

Cuticle and stomata also found in all vascular plant sporophyate

Question 20

Tracheophytes

Answer 20

Vascular plants include seven extant phyla grouped in three clades​

Lycophytes (club mosses)​

Pterophytes (ferns, whisk ferns, and horsetails)​

Seed plants​

Gametophyte has been reduced in size relative to the sporophyte during the evolution of tracheophytes​

Similar reduction in multicellular gametangia has occurred as well

Question 21

Stems Evolved Early

Answer 21

Fossils of early vascular plants reveal stems, but no roots of leaves​

Lack of roots limited the size of these plants in two ways:​

Roots anchor plants to the ground, preventing them from falling over​

An extensive root system is needed to ensure a large plant’s need for water is met

Question 22

Roots

Answer 22

True roots are found only in the tracheophytes.​

Only roots provide both transport and support.​

Nontracheophytes may have structure that provide one or the other​

Lycophytes diverged from other tracheophytes before roots evolved​

It appears that roots evolved at least twice.

Question 23

Leaves

Answer 23

Increase surface area for photosynthesis.​

Evolved twice.​

Euphylls (true leaves) found in ferns and seed plants.​

Lycophylls found in lycophytes.

Question 24

Seeds

Answer 24

Highly resistant structures – protect embryos from environmental stresses​

Contain food supply for young plant.​

Lycophytes and pterophytes do not have seeds.​

Fruits in the flowering plants (angiosperms) add a layer of protection to seeds and attract animals that assist in seed dispersal, expanding the potential range of the species.

Question 25

Lycophytes

Answer 25

Sister group to all other vascular plants​ Leaves developed independently​ Sprophyte dominant​ Lack seeds​ Worldwide in distribution – most abundant in the tropics

Question 26

Club Moss, Selaginella

Answer 26

Superficially resemble true mosses, but have quite different vascular structure and reproductive processes​ Small, unbranched veins​ Specialized leaves bear spores​ Small, free-living gametophytes that produce both sperm and eggs​ Gametophyte may be photosynthetic​ Sporophyte is dependent upon gametophyte until its leaves develop

Question 27

Pterophytes

Answer 27

Phylogenetic relationships among ferns and their relatives is still being sorted out​ Common ancestor gave rise to 2 clades​ A line of ferns and horsetails​ Another line of ferns and whisk ferns​ All form antheridia and archegonia​ All require water for flagellated sperm

Question 28

Whisk Ferns

Answer 28

Found in tropics​ Sporophyte consists of evenly forking green stems without true leaves or roots​ Some gametophytes develop elements of vascular tissue​ Only one known to do so.

Question 29

Horsetails

Answer 29

All 15 living species are members of a single genus, Equisetum​ Sporophyte consists of ribbed, jointed photosynthetic stems that arise from branching rhizomes with roots at nodes​ Whorl of nonphotosynthetic, scalelike leaves emerges at each node​ Silica deposits in cells – (also called scouring rushes because pioneers in the American West used them to scrub pans)

Question 30

Ferns

Answer 30

Most abundant group of seedless vascular plants​ About 11,000 species.​ Coal formed from forests 300 M Y A​ Conspicuous sporophyte and much smaller gametophyte are both photosynthetic

Question 31

Fern Life Cycle

Answer 31

Fern life cycle differs from that of a moss​ Much greater development, independence, and dominance of the fern’s sporophyte​ Sporophyte is structurally more complex than moss – having vascular tissue and well-differentiated roots, stems, and leaves​ Gametophyte lacks vascular tissue

Question 32

Fern morphology

Answer 32

Sporophytes have rhizomes​ Fronds (leaves) develop at the tip of the rhizome as tightly rolled-up coils (“fiddleheads”)

Question 33

Fern reproduction

Answer 33

Produce distinctive sporangia in clusters called sori on the back of the fronds​ Diploid spore mother cells in sporangia produce haploid spores by meiosis​ Spores germinate into gametophyte​ Rhizoids but not true roots – no vascular tissue.​ Flagellated sperm