Ch 26: Colonization of Land

Question 1

Contrast environmental conditions in the aquatic and terrestrial environment and describe how these differences impacted the evolution of land plants

Answer 1

As organisms adapted to life on land, they had to contend with several challenges in the terrestrial environment. Desiccation, or drying out, is a constant danger for an organism exposed to air. Even when parts of a plant are close to a source of water, the aerial structures are likely to dry out. Water also provides buoyancy to organisms. On land, plants need to develop structural support in a medium that does not give the same lift as water. Additionally, the male gametes must reach the female gametes using new strategies, because swimming is no longer possible. Therefore, both gametes and zygotes must be protected from desiccation.

Question 2

Identify the sister group to land plants

Answer 2

Charophytes (Green Algae)

Question 3

Define alternation of generations and diagram the generalized plant life cycle (list all of the stages, indicate whether they are unicellular or multicellular, and the processes that occur between stages)

Answer 3

Alternation of generations: alternates between two multicellular forms - Multicellular Haploid (Gametophyte) and Multicellular Diploid (Sporophyte)

Gametophyte (Multicellular Haploid) → Gamete (Unicellular Haploid via mitosis) → Fertilization (gamete + gamete) → Zygote (Unicellular Diploid) → Sporophyte (Multicellular Diploid)→ Spores (Unicellular Haploid via meiosis) → Gametophyte (Multicellular Haploid via mitosis)

Question 4

Explain the advantage of alternation of generations

Answer 4

Evolution of the multicellular sporophyte enhanced dispersal on land

Question 5

Explain why sporopollelin is adaptive

Answer 5

Adaptive because it protects spores from drying out, and other environmental challenges; made out of polymers

Question 6

Describe the characteristics of bryophytes and give examples of bryophytes

Answer 6

liverworts, hornworts & mosses; dominant life cycle stage is the gametophyte

Question 7

Explain what limits the size of bryophytes

Answer 7

no vascular tissue; The lack of roots for absorbing water and minerals from the soil, as well as a lack of reinforced conducting cells, limits bryophytes to small sizes.

Question 8

Explain the evolutionary significance of vascular tissues and lignin to the evolution of land plants

Answer 8

vascular tissue lets them grow taller and outcompete bryophytes for resources; lignin for strength and structure

Question 9

Give examples of seedless vascular plants

Answer 9

Lycophytes, Monilophytes (ex: Ferns, Horsetails)

Question 10

Explain the evolutionary significance of pollen and seeds

Answer 10

The evolution of seedsallowed plants to reproduce independently of water; pollen allows them to disperse their gametes great distances

Question 11

Describe the structure of a seed

Answer 11

Most seeds consist of three parts:embryo, endosperm, and seed coat

Question 12

Distinguish between male and female cones in gymnosperms

Answer 12

The female cones are larger than the male cones and are positioned towards the top of the tree; the small, male cones are located in the lower region of the tree. Because the pollen is shed and blown by the wind, this arrangement makes it difficult for a gymnosperm to self-pollinate.

Question 13

Compare and contrast monocots and eudicots

Answer 13

• Monocots have one cotyledon, while eudicots have two.
• Dicot flower parts are organized in multiples of four or five, while in monocots flowers are organized in multiples of three.
• Overall, eudicots generally have tap roots while monocots have fibrous roots
• Eudicots have reticulate (net-like) venation on their leaves, while monocots usually have parallel venation.
• Monocots have their vascular bundles scattered in the stem, while eudicots have them organized in a ring around the stem.

Question 14

Contrast life cycles of angiosperms, gymnosperms, seedless vascular plants and bryophytes with a particular emphasis on which life cycle stage is dominant

Answer 14

Bryophytes - Gametophyte dominant

Vascular Plants - Sporophyte dominant

Question 15

NOTES

Answer 15

• Sporopollenin and an embryo protected and nourished by the parentplant are adaptations for terrestrial life seen in all plants.
• Spores and seeds have basically the same function—dispersal—but are vastly different because spores are unicellular and seeds are not.
• Bryophytes differ from other plant groups because their gametophyte generation is dominant.