Topic 9

Question 1

What are the general characteristics of the plant kingdom?

Answer 1

land-dwelling (terrestrial), some have returned to aquatic (freshwater) habitats

eukaryotes

multicellular

photosynthetic (photoautotrophs)

cell walls made of cellulose

alternation of generations

Question 2

What are the two main groups in the plant kingdom?

Answer 2

Non Vascular Plants (mosses)

Vascular Plants: seedless vascular plants (ferns), gymnosperms, angiosperms

Question 3

What are the benefits of plants moving to land?

Answer 3

spacious

unfiltered sunlight

high levels of atmospheric CO2

rich source of mineral nutrients

relatively few herbivores and pathogens

Question 4

What were the challenges for plants moving to land?

Answer 4

less water

need to resist gravity

reproduction

Question 5

What are the synapomorphic features with charophytes?

Answer 5

1. Rings of cellulose-synthesiezing proteins (make cellulose microfibrils of the cell wall, are linear in non-charophycean algae)
2. Structure of the sperm resembles the sperm of charophytes (but only for those plants with flagellated sperm)
3. Phragmoplast during cell division (microtubules, constructs cell plate between incipient cells, becomes new cell wall)

Question 6

What were the evolutionary innovations that allowed plants to adapt to life on land?

Answer 6

sporopollenin

cuticle, pores

stomata

embryophytes

vascular tissue

roots

true leaves

Question 7

How was sporopollenin an adaptation to life on land?

Answer 7

in charophytes: protects zygote from drying

in plants: walls of plant spores

resistant to drying and physical stresses

Question 8

What were adaptations for water conservation for plants moving to land?

Answer 8

waxy cuticle on epidermis: waterproofing, protection from microbial attack

stomata: pores on the epidermis of leaves and other photosynthetic organs, allow gas exchange between air and leaf interior, sites for water to exit via evaporation, closed stomata minimize water loss

Question 9

How were multicellular, dependent embryos an adaptation to life on land?

Answer 9

zygotes retained within tissues of the female parent

parent provides nutrients, embryo has specialized placental cells (transfer nutrients)

in contrast to most green algae, zygotes of land plants: begin development on the parent plant

the retention of the embryo was a key event in land plant evolution

Question 10

How was lignified vascular tissue for internal support an adaptation to life on land?

Answer 10

contain lignin (a complex polymer), which strengthens

xylem cells carry water and minerals up from roots (dead wall act as microscopic water pipes)

phloem cells distribute organic products (living cells)

Question 11

How was the compartmentalization of resources an adaptation to life on land?

Answer 11

most plants show structural specialization for searching for water and minerals underground (roots) and light and gases aboveground (shoots)

elongation and branching maximizes root and shoot exposure to environmental resources

Question 12

What are apical meristems?

Answer 12

undifferentiated tissue from which new, differentiated cells arise: simple in non-vascular plants, more complex structures at tips of shoots and roots in vascular plants

cells produced by meristems differentiate into various tissues, including surface epidermis and internal tissues

Question 13

How is alternation of generations an adaptation to life on land?

Answer 13

haploid (n) multicellular and diploid (2n) multicellular body forms alternate

Question 14

What is adaptive radiation?

Answer 14

an adaptive radiation occurs when a single lineage produces a large number of descendant species that are adapted to a wide variety of habitats

angiosperms represent one of the greatest adaptive radiations in the history of life

Question 15

What are bryophytes?

Answer 15

nonvascular plants

not a monophyletic group

Question 16

What are the characteristics of bryophytes?

Answer 16

lack true vascular tissue: limits their size

most tissues only one or a few cells thick

haploid (1n) gametophytes are the most conspicuous, dominant phase of the life cycle (diploid sporophytes smaller, diploid present only part of the time)

often entire plants are either male or female (sperm swim through water film to fertilize eggs, must live in moist places, not yet full terrestrial)

Question 17

What are the key concepts of how plants colonized land?

Answer 17

land plants evolved from green algae (specifically charophytes)

three innovations allow plants to colonize land (sporopollenin, multicellular, nourished embryo)

mosses and other nonvascular plants have life cycles dominated by gametophytes

ferns and other seedless vascular plants were the first plants to grow tall

Question 18

What was the origin of vascular plants?

Answer 18

bryophytes probably earth’s only plants for first 100 million years

aglaophyton first plant to have sporophytes not continuously nutritionally dependent on gametophytes (a feature of vascular plants)

fossils of other simple plants from early Devonian show evidence of vascular tissue in the stem

later came leaves, and then roots

Question 19

What are the characteristics of extant vascular plants?

Answer 19

Vascular Tissue (xylem: contains lignin, strengthening polymer, dead hollow cells act as water pipes. phloem: living cells, distribute nutrients, organic products) gave plants a competitive advantage, ability to resist gravity and grow taller

Complex multicellular roots: absorb nutrients, provide anchor

Complex multicellular leaves: photosynthetic organs

Sporophylls: modified leaves that bear sporangia (spore-producing organ)

Sporophyte dominant in life cycle: increased size, complexity and persistence, not continuously nutritionally dependent on gametophyte

Question 20

What are the two phylums of seedless vascular plants?

Answer 20

Phylum Lycophyta (quillworts, club “mosses”, spike “mosses” (not really mosses!))

Phylum Pterophyta (ferns, horsetails, whisk ferns)

Question 21

What are the characteristics of seedless vascular plants?

Answer 21

sporophyte: dominant form
gametophytes: tiny independent plants on or just below soil surface

flagellated sperm: must swim in a film of water to reach eggs (similar to bryophytes, seedless vascular plants most common in relatively damp habitats, still need water to reproduce)

Question 22

What is Phylum Lycophyta?

Answer 22

microphylls (small leaves)

carboniferous period: lycophytes existed as small, herbaceous plants and as giant woody trees

giant lycophytes thrived in warm, moist swamps

became extinct when the climate became cooler and drier

smaller lycophytes survived and are represented by about 1,000 species today

Question 23

What is the Phylum Pterophyta?

Answer 23

whisk ferns once considered “living fossil” (no roots or leaves)

horsetails (in carboniferous, horsetails grew to 15 m, often found in marshy habitats and along streams and sandy roadways)

Question 24

What are true ferns?

Answer 24

megaphylls: large leaves with extensively branched vascular system, some tree-size

most successful of extant seedless vascular plants

produce clusters of sporangia called sori on undersides of leaves

sporangia often have spring-like devices that catapult spores from the parent plant (spores can also be carried by the wind)

Question 25

What are the advantages of seeds?

Answer 25

seeds provide some evolutionary advantages over spores

they may remain dominant 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

Question 26

What are the key concepts of seedless vascular plants?

Answer 26

ferns and other seedless vascular plants were the first plants to grow tall (had well developed roots and leaves)

in contrast to bryophytes, seedless vascular plants have life cycles dominated by free-living sporophytes

a change in environment at end of carboniferous reduced moisture leading to seed plants evolving