Chapter 29 - Plant Diversity I

Question 1

What is the likely common ancestor of all land plants?

Answer 1

Green algae that is still a mystery

• chlorophytes (aquatic)
• charophyta (sister to all land plants

Question 2

What are the 5 key traits of land plants?

Answer 2

1) alternation of generations and protected embryos
2) multicellular, dependent embryos
3) walled spores produced in sporangia
4) multicellular gametangia
- archaegonia = female
- antherida = male
5) apical meristems
- are localized regions of cell division
- at the tips of roots and shoots

Question 3

How do plants deal with limited water availability?

Answer 3

• a waxy cuticle on exposed surfaces helps prevent water loss as does the exchange of gases through the stomata
• tracheids are specialized for water and mineral transport

Question 4

Charophytes

Answer 4

• rings of cellulose-synthesizing proteins
• peroxisome enzymes
• structure of flagellated sperm is very similar
• formation of a phragmoplast

Question 5

What is the advantage to a shift toward the diploid generation in land plants?

Answer 5

Allows for greater genetic diversity

Question 6

Gametophyte Generation

Answer 6

• haploid generation

* prominent in mosses, ferns, and liverworts

Question 7

Sporophyte Generation

Answer 7

• diploid generation

* more prominent in gymnosperms and angiosperms

Question 8

Bryophytes

Answer 8

• Close living descendants of the first land plants
• includes liverworts, mosses, and hornworts
• are nontracheophytes; no tracheids
• have other conducting cells for moving water and nutrients
• many have mycorrhizal associations: symbiotic relationship between fungi and plants
• liverworts and mosses have a non photosynthetic sporophyte that depends on a gametophyte for nutrients

Question 9

Liverworts

Answer 9

• ancient phylum
• flattened gametophytes w/ flattened lobes that look like liver
• produce upright structures that contain gametangia

Question 10

Mosses

Answer 10

• exhibit alternation of generations
• can withstand droughts
• stomata close in hot, dry conditions to minimize water loss
• have rhizoids
• have water-conducting tissues
• most mosses are highly sensitive to air pollution
• peat moss can absorb up to 25 times their weight in water

Question 11

Hornworts

Answer 11

• stomata in sporophyte open and close to regulate gas exchange
• sporophyte is photosynthetic

Question 12

Ecological and Economical Importance of Mosses

Answer 12

• help retain nitrogen in the soil
• mosses can live in very cold or dry areas as they can lose most of their body water & then re-hydrate when the moisture is available
• Sphagnum or peat moss does not readily decay; low temp, pH, and oxygen level of peat lands inhibit decay of moss and other organisms - some have preserved corpses for thousands of years
• peat is used as a fuel source in Ireland and Canada
• Peat moss is used as a soil conditioner; it can absorb 20 times its weight in water
• Peat lands contain roughly 30% of the worlds soil carbon

Question 13

Xylem

Answer 13

Conducts water and minerals from roots

Question 14

Cooksonia

Answer 14

1st known vascular land plant

- vascular tissues allows for distribution of nutrients

Question 15

Phloem

Answer 15

Conducts sucrose and hormones

Question 16

Vascular tissue

Answer 16

• allows for distribution of nutrients
• develops in sporophytes
• vascular plants have reduced gametophyte

Question 17

Vascular plants exist as these 3:

Answer 17

• Lycophytes
• monilophytes
• seed plants

Question 18

Stems

Answer 18

Evolved before roots did

Question 19

Roots

Answer 19

• provide structural support and transport capability

Question 20

Leaves

Answer 20

• evolved more than once

- Lycophytes; no vascularization in leaves
- ferns and seed plants have true leaves

Question 21

Seeds

Answer 21

• are another innovation in some phyla
• protects embryo from drying out
• protection from predators (somewhat)

Question 22

Lycophytes

Answer 22

• earliest vascular plant

* 1st plants to have a dominant sporophyte generation

Question 23

Monilophytes

Answer 23

• ferns
• horsetails
• whisk ferns
• require water for fertilization and are seedless

Question 24

Whisk ferns

Answer 24

• lost their roots and leaves secondarily

Question 25

Horsetails

Answer 25

• have jointed stems w/brush like leaves

* stems have silica deposits in epidermal cells w/their ribs

Question 26

Ferns

Answer 26

• have fronds that bear sori

 - sori are sporangia located on underside of fern fronds
 - gametophyte is heart-shaped and can live independently