Plant Diversity I: How Plants Colonized Land

Why do researchers identify the charophytes rather than another group of algae as the closest living relatives of plants?

Identify four derived traits that distinguish plants from charophyte green algae and facilitate life on land. Explain.

WHAT IF? What would the human life cycle be like if we had alternation of generations? Assume that the multicellular diploid stage would be similar in form to an adult human.

How do bryophytes differ from other plants?

Give three examples of how the structure fits function in bryophytes.

MAKE CONNECTIONS Review the discussion of feedback regulation in Concept 1.1. Could the effects of global warming on peatlands alter CO₂ concentrations in ways that result in negative or positive feedback? Explain.

Why did the researchers add filtrate from which macerated moss had been removed to the control microcosms?

Make two bar graphs (for granite and andesite) comparing the mean amounts of each element weathered from rocks in the control and experimental microcosms. (Hint: For an experimental microcosm, what sum represents the total amount weathered from rocks?)

Overall, what is the effect of moss on the chemical weathering of rock? Are the results similar or different for granite and andesite?

Based on their experimental results, the researchers added weathering of rock by non-vascular plants to simulation models of the Ordovician climate. The new models predicted decreased CO₂ levels and global cooling sufficient to produce the glaciations in the Late Ordovician period. What assumptions did the researchers make in using results from their experiments in climate simulation models?

“Life has profoundly changed the Earth.” Explain whether or not these experimental results support this statement.

List the key derived traits found in monilophytes and seed plants, but not in lycophytes.

How do the main similarities and differences between seedless vascular plants and nonvascular plants affect function in these plants?

In Figure 29.12, if fertilization occurred between gametes from one gametophyte, how would this affect the production of genetic variation

from sexual reproduction?

Three of the following are evidence thatcharophytes are the closest algal relatives ofplants. Select the exception.

(A) similar sperm structure

(B) the presence of chloroplasts

(C) similarities in cell wall formation during celldivision

(D) genetic similarities in chloroplasts

Which of the following characteristics of plants is absent in their closest relatives, the charophyte algae?

(A) chlorophyll b

(B) cellulose in cell walls

(C) sexual reproduction

(D) alternation of multicellular generations

In plants, which of the following are produced by meiosis?

(A) haploid gametes

(B) diploid gametes

(C) haploid spores

(D) diploid spores

Microphylls are found in which plant group?

(A) lycophytes

(B) liverworts

(C) ferns

(D) hornworts

Suppose an efficient conducting system evolved in a moss that could transport water and other materials as high as a tall tree. Which of the following statements about “trees” of such a species would not be true?

(A) Spore dispersal distances would probably increase.

(B) Females could produce only one archegonium.

(C) Unless its body parts were strengthened, such a “tree”

would probably flop over.

(D) Individuals would probably compete more effectively for

access to light.

Identify each of the following structures as haploid or diploid.

(A) sporophyte

(B) spore

(C) gametophyte

(D) zygote

EVOLUTION CONNECTION DRAW IT Draw a phylogenetic tree that represents our current understanding of evolutionary relationships between a moss, a gymnosperm, a lycophyte, and a fern. Use a charophyte alga as the outgroup. (See Figure 26.5 to review phylogenetic trees.) Label each branch point of the phylogeny with at least one derived character unique to the clade descended from the common ancestor represented by the branch point.

The feather moss Pleuroziumschreberiharbors species of symbiotic nitrogen-fixing bacteria. Scientists studying this moss in northern forests found that the percentage of the ground surface “covered” by the moss increased from about 5% in forests that burned 35 to 41 years ago to about 70% in forests that burned 170 or more years ago. From mosses growing in these forests, they also obtained the following data on nitrogen fixation:

(a) Use the data to draw a line graph, with age on the x-axis and the nitrogen fixation rate on the y-axis. 

(b) Along with the nitrogen added by nitrogen fixation, about 1 kg of nitrogen per hectare per year is deposited into northern forests from the atmosphere as rain and small particles. Evaluate the extent to which Pleurozium affects nitrogen availability in northern forests of different ages.

Giant lycophyte trees had microphylls, whereas ferns and seed plants have megaphylls. Write a short essay (100–150 words) describing how a forest of lycophyte trees may have differed from a forest of large ferns or seed plants. In your answer, consider how the type of forest may have affected interactions among small plants growing beneath the tall ones.

These stomata are from the leaf of a common horsetail. Describe how stomata and other adaptations facilitated life on land and ultimately led to the formation of the first forests.