Plant Diversity I

Question 1

how did land plants evolve?

Answer 1

from ancestral green algae

Question 2

streptophytes

Answer 2

• charophytes and land plants
• monophyletic
• modern charophytes - sister taxon to land plants (embryophytes)

Question 3

where do streptophytes live and is it always wet or dry?

Answer 3

• many live at edges of ponds

- sometimes dries out -> selection favors survival on dry land

Question 4

what are the derived traits of streptophytes?

Answer 4

• sporopollenin: layer of polymer, surrounds zygote, prevents desiccation
• similar adaptations in plant spores

Question 5

what DTs do streptophytes, modern charophytes and land plants have in common?

Answer 5

• rings of cellulose, synthesizing proteins
• structure of flagellated sperm
• cell plate

Question 6

list the derived traits of land plants

Answer 6

1. alternation of generations
2. Multicellular Dependent Embryo
3. Walled Spores Produced in Sporangia
4. Multicellular Gametangia
5. Apical Meristems
6. Cuticle
7. Stomata

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Question 7

Alternation of Generations

Answer 7

• Haploid gametophyte produces gametes by mitosis
• DIploid sporophyte produces spores by meiosis

2 multicellular stages, 2 unicellular stages

gametophyte (n) -> mitosis -> gametes (n) -> fertilization -> zygote (2n) -> mitosis -> sporophyte (2n) -> meiosis -> spores (n) -> mitosis -> gametophyte (n)

Question 8

Multicellular, Dependent Embryo

Answer 8

2n embryo (-> sporophyte) retained within tissue of female gametophyte (n)

• nutrients transferred to embryo through transfer cells
• (why land plants sometimes called “embryophytes”)

Question 9

Walled Spores Produced in Sporangia (Sporangia, Sporocytes and Spores)

Answer 9

• sporangia: multicellular organs on sporophyte where spores are produced
• sporocytes: diploid cells in sporangia, undergo meiosis -> haploid spores
• spores: haploid reproductive cells (spore wall contains sporopollenin) [resistant to hard conditions]

Question 10

Multicellular Gametangia

Answer 10

• organs on gameteophyte where gametes are produced

- 2 types of gametangia: Archegonia and Antheridia

Question 11

what are the two types of gametangia?

Answer 11

• archegonia: produce eggs, site of fertilization

- antheridia: produce and release sperm

Question 12

Apical Meristems

Answer 12

localized regions of cell division at tips of roots and shoots
-cells differentiate from apical meristems

Question 13

Cuticle

Answer 13

• waxy covering over all above-ground parts
• benefits: prevents desiccation, provides some protection from microbes
• costs: does not allow for gas exchange

Question 14

Stomata

Answer 14

(singular = stoma)

• tiny openings on surface
• can open and close
• allow gas exchange
• allow water evaporation

Question 15

how are extant plants grouped?

Answer 15

based on vascular tissue

Question 16

vascular tissue

Answer 16

transports water and nutrients

Question 17

nonvascular plants

Answer 17

• bryophytes (bryophyta): mosses and relatives
• basal Land plants
• lack specialized vascular systems/transport tissue (rely on diffusion, osmosis -> typically small, require moist environment for: getting water to all cells and reproduction [sperm swim to egg])
• paraphyletic

Question 18

vascular plants

Answer 18

• seedless and seed plants

- seedless vascular plants: Ferns and related plants

Question 19

seed plants

Answer 19

majority of extant plant species

Question 20

seed

Answer 20

embryo with supply of nutrients with protective coat

Question 21

gymnosperms

Answer 21

• “naked seed”
• seeds not enclosed in a chamber
• ex: conifers

Question 22

angiosperms

Answer 22

• “container” seeds
• flowering plants
• seeds enclosed in fruit (peach)
• most dominant type of plant

Question 23

gametophyte (n)

Answer 23

gamete-forming plant

Question 24

sporophyte (2n)

Answer 24

spore-forming plant

Question 25

sporangium

Answer 25

spore-producing structure

Question 26

what is the moss life cycle

Answer 26

alternation of generations - haploid dominant

Question 27

moss life cycle (haploid)

Answer 27

male spore ->mitosis-> male gametophyte->mitosis in antheridium->sperm->swim-> egg in archegonium female spore->mitosis->female gametophyte->mitosis in archegonium->egg in archegonium

Question 28

moss life cycle (diploid)

Answer 28

egg in archegonium (n)->fertilization->zygote->mitosis->sporophyte->meiosis in sporangium->spore

Question 29

what is the importance of mosses?

Answer 29

- extremely common - can colonize bare, sandy soil - sometimes harbor N-fixing bacteria (help retain N in soil) - Peat

Question 30

Peat

Answer 30

partially decayed organic matter - peat moss is important component - important fuel source - important C reservoir (3% of Earth's surface by ~30% of C in soil)

Question 31

vascular plants

Answer 31

- earliest fossil ~425 mya | - dominant today

Question 32

list the derived traits of vascular plants

Answer 32

1. sporophyte dominant 2. transport in vascular tissue 3. roots 4. leaves 5. sporophylls 6. spore variations (homo- and heterosporous)

Question 33

lignin

Answer 33

polymer in cell walls of water-conducting cells of xylem

Question 34

xylem

Answer 34

tube that conducts water and minerals - contain lignin

Question 35

phloem

Answer 35

tube that conducts sugars, AAs, and organic products

Question 36

sporophyte dominant

Answer 36

larger, independent of gametophyte

Question 37

transport in vascular tissue

Answer 37

don't have to be flat anymore (enables tall growth [outcompete shorter plants for light, better spore dispersal]) -lignin, xylem and phloem

Question 38

roots

Answer 38

organs that absorb water and nutrients from soil, anchor plants -> allow for taller growth

Question 39

leaves

Answer 39

main photosynthetic organs, more SA

Question 40

sporophylls

Answer 40

modified leaves with sporangia - very diverse - ferns: leaves with sori - gymnosperms-cones

Question 41

spore variations

Answer 41

2 forms of spore production homosporous: 1 type of sporangium produces one type of spore - most seedless vascular plants - sporangium->meiosis->spore->mitosis->bisexual gametophyte (produces both egg and sperm) heterosporous: 2 types of sporangia producing 2 spore types - megasporangium->meiosis->megaspores->mitosis->female gametophyte->mitosis->egg - microsporangium->meiosis->microspores->mitosis->male gametophyte->mitosis->sperm

Question 42

seedless vascular plants

Answer 42

- paraphyletic - 2 clades- Ferns (monilophytes) and related plants - many are epiphytes, use other plants as substrate, not parasitic (grow on surface of trees)

Question 43

fern life cycle

Answer 43

1. homosporous spore production 2. spores grow into free-living bisexual photosynthetic gametophyte 3. gametophyte develops antheridia and archegonia 4. sperm and egg produced at different times - prevents self-fertilization 5. flagellated sperm swim to egg -> fertilization (requires water) 6. zygote grows in sporophyte, grows out of archengonium 7. spores produced via meiosis in sori: clusters of sporangia under leaves