MC:
Which of the following groups is definitely monophyletic?
answer
green plants
question
MC:
The appearance of cuticle and stomata correlated with what event in the evolution of land plants?
answer
growth on land
question
MC:
What is a pollen grain?
answer
male gametophyte
question
MC:
What do seeds contain?
answer
embryo and nutritive tissue
question
Land plants may have reproductive structures that:
(a) protect gametes as they develop
(b) allow sperm to be transported in the absence of water
(c) provide stored nutrients and a protective coat so that offspring can be dispersed by wind away from the parents plant
(d) provide nutritious tissue around seeds that facilitates dispersal by animals
Name each of these four structures, and state which land plant group or groups have each structure.
answer
(a) Gametangia are found in all land plant groups except angiosperms
(b) pollen is found in gymnosperms and angiosperms
(c) seeds are found in gymnosperms and angiosperms
(d) fruit is found in angiosperms
question
What does it mean to say that a life cycle is gametophyte dominant versus sporophyte dominant?
answer
In a gametophyte-dominant life cycle, the gametophyte is larger and longer lived than the sporophyte and produces most of the nutrition. In a sporophyte-dominant life cycle, the sporophyte generation is the larger, longer-lived, and photosynthetic phase of the life cycle.
question
MC:
In the life cycle of an angiosperm, the egg
answer
is one of the cells formed by mitosis in the ovule.
question
Soils, water, and the atmosphere are major components of the abiotic (nonliving) environment. Describe how green plants affect the abiotic environment in ways that are advantageous to humans.
answer
Plants build and hold soils required for human agriculture and forestry, and they increase water supplies that humans can use for drinking, irrigation, or industrial use. Plants release oxygen that we breathe.
question
The evolution of cuticle presented land plants with a challenge that threatened their ability to live on land. Describe this challenge, and explain why stomata represent a solution. Compare and contrast stomata with pores found in liverworts.
answer
Cuticle prevents water loss form leaves but also prevents entry of CO2 required for photosynthesis. Stomata allow CO2 to diffuse but can close to minimize water loss. Liverwort pores allows gas exchange but cannot be closed if conditions become dry.
question
Why was the evolution of lignin-reinforced cell walls significant?
answer
They provided support needed for plants to grow upright and not fall over in response to wind or gravity. Erect growth allowed plants to compete for light.
question
Explain the difference between homosporous and heterosporous plants. Where are the microsporangium and megasporangium found in a tulip? What happens to the spores that are produced by these structures?
answer
Homosporous plants produce a single type of spore that develops into a gametophyte that produces both egg and sperm. Heterosporous plants produce two different types of spores that develop into two different gametophytes that produce either egg or sperm. In a tulip, the microsporangium is found within the stamen, and the megasproagium is found within the ovule. Microspores divide by mitosis to form male gametophytes (pollen grains); megaspores divide by mitosis to form the female gametophyte.
question
Describe the advantage that flowering plants gain by using animals to transfer pollen from one individual to another.
answer
Animal pollinators increase the efficiency of pollination so plants can save energy by making less pollen.
question
MC:
Which of the following statements is NOT true?
answer
According to the fossil record and phylogenetic analyses, angiosperms evolved before the gymnosperms. Angiosperms are the only land plants with vessels.
question
Angiosperms such as grasses, oaks, and maples are wind pollinated. The ancestors of these subgroups were probably pollinated by insects, however. As an adaptive advantage, why might a species "revert" to wind pollination? (Hint: Think about the costs and benefits of being pollinated by insects versus wind.) Why is it logical to observe that wind-pollinated species usually grow in dense stands containing many individuals of the same species? Why is it logical to observe that in wind-pollinated deciduous trees, flowers form very early in spring -- before leaves form?
answer
A "reversion" to wind pollination might be favored by natural selection because it is costly to produce a flower that can attract animal pollinators. Because wind-pollinated species grow in dense clusters, they can maximize the chance that the wind will carry pollen from one individual to another (less likely if the individuals are far apart). Wind-pollinated deciduous trees flower in early spring before their developing leaves begin to block the wind.
question
Vessel elements transport water much more efficiently than tracheids, but they are much more susceptible than tracheids to being blocked by air bubbles. Suggest a hypothesis to explain why the vascular tissue of angiosperms consists of a combination of vessel elements and tracheids.
answer
The combination represents a compromise between efficiency and safety. Tracheids can still transport water if vessels come blocked by air bubbles.
question
You have been hired as a field assistant for a researcher interested in the evolution of flower characteristics in orchids. Design an experiment to determine whether color, size, shape, scent, or amount of nectar is the most important factor in attracting pollinators to a particular species. Assume that you can change any flower's color with a dye and that you can remove petals or nectar stores, add particular scents, add nectar by injection, or switch parts among species by cutting and gluing.
answer
Alter one characteristic of a flower, and present the flower to the normal pollinator. As a control, present the normal (unaltered) flower to the normal pollinator. Record the amount of time the pollinator spends in the flower, the amount of pollen removed, or some other measure of pollination success. Repeat for other altered characteristics. Analyze the data to determine which altered characteristic affects pollination success the most.
question
Explain why:
(1) morphological data
(2) the fossil record
(3) molecular phylogenies
all support the hypothesis that land plants evolved from green algae.
answer
(1) Green algae and land plants share an array of morphological traits that are synapomorphies, including the chlorophylls they contain
(2) Green algae appear before land plants in the fossil record
(3) On phylogenetic trees estimated from DNA sequence data, green algae and land plants share a most recent common ancestor -- green algae are the initial groups to diverge, and land plants diverge subsequently.
question
Explain why the groups called green algae, nonvascular plants, and seedless vascular plants are paraphyletic.
answer
If you find the common ancestor of all the green algae (at the base of the Ulvophyceae), the lineages that are collectively called green algae don't include that common ancestor and all of its descendants -- only some of its descendants. The same is true for non-vascular plants (the common ancestor here is at the base of the Hepaticophyta) and seedless vascular plants (the common ancestor here is at the base of the Lycophyta).
question
Biologists claim that vessels are more efficient than tracheids at transporting water, in part because vessels are shorter and wider than tracheids. Why does this claim make sense?
answer
Water flows more easily through a short, wide pipe than through a long, skinny one because there is less resistance from the walls of the pipe.
question
Explain the logic that biologists use to map the location of the innovations on phylogenetic trees.
answer
To map an innovation on a phylogenetic tree, biologists determine the location(s) on the three that is (are) consistent with all descendants from that point having the innovation (unless, in rare cases, the innovation was lost in a few descendants).
question
If you understand the basic principles of alternation of generations, you should be able to describe this type of life cycle and explain one hypothesis for why this life cycle might have evolved in land plants.
answer
Alternation of generations occurs when there are multicellular haploid individuals and multicellular diploid individuals in a life cycle. One hypothesis is that this life cycle evolved because the plants with a large sporophyte were more successful at using the wind to disperse many spores, while a small gametophyte produces gametes that can swim.
question
How can you tell that alternation of generations occurs in mosses (Figure 31.13) and terms (Figure 31.14)?
answer
There are multicellular haploid stages and multicellular diploid stages in these plants.
question
If you understand the difference between gametophyte-dominant and sporophyte-dominant life cycles, you should be able to examine the photos of hornworts (a nonvascular plant) and horsetails (a seedless vascular plant) in Figure 31.15 and identify which is the gametophyte and which is the sporophyte.
answer
In the hornwort photo, the sporophyte is the spike-like green and yellow structure; the gametophyte is the leafy-looking structure underneath. The horsetail gametophyte is the microscopic individual on the left; the sporophyte is the much larger individual on the right.
question
Compare the life cycle of the pine tree in Figure 31.18 with that of the fern pictured in Figure 31.14. Is the gymnosperm gametophyte larger than, smaller than, or about the same size as a fern gametophyte? Compared with ferns, is the gymnosperm gametophyte more or less dependent on the sporophyte for nutrition?
answer
Gymnosperm gametophytes are microscopic, so they are even smaller than fern gametophytes. The gymnosperm gametophyte is completely dependent on the sporophyte for nutrition, while fern gametophytes are not. Fern gametophytes are photosynthetic and even supply nutrition to the young sporophytes.
question
Gymnosperm pollen grains typically contain from 4 to 40 cells; mature angiosperm pollen grains contain three cells. Gymnosperm female gametophytes typically contain hundreds of cells; angiosperm female gametophytes typically contain seven. Do the observations conflict with the trend of reduced gametophytes during land plant evolution, or are they consistent with it? Explain your logic.
answer
Consistent -- the fossil data suggest that gymnosperms evolved earlier, and gymnosperms have larger gametophytes than angiosperms.
question
Why did the researchers measure pollination in a greenhouse? Why did they plot flower visit on different scales?
answer
To eliminate all other variables except for the one being tested, such as the possibility of pollination by other insects in the field. Scales differ because the two insect species visited flowers at very different frequencies.
question
Explain why the evolution of cuticle, UV-absorbing compounds, and vascular tissue was important in survival or reproduction.
answer
Cuticle prevents water loss form the plant; UV-absorbing compounds allow plants to be exposed to high light intensities without damage to their DNA; vascular tissue moves water up from the soil and moves photosynthetic products down to the roots.
question
You should be able to mark the origin of plasmodesmata on Figure 31.6.
answer
Green Algae > Charophyceae (Stoneworts)
question
You should be able to mark the origin of egg retention on Figure 31.6.
answer
Green Algae > Charophyceae (Stoneworts)
question
You should be able to mark the origin of the simple water-conducting cells and tissues in this moss subgroup on Figure 31.6.
answer
Nonvascular Plants > Bryophtya (Mosses)
question
You should be able to mark the origin of microphylls on Figure 31.6.
answer
Seedless Vascular Plants > Lycophyta (Lycophytes, or Club Mosses)
question
After reviewing where leaves and roots originated during land plant evolution (see Figure 31.9), you should be able to mark the loss of leaves an roots in whisk ferns on Figure 31.6.
You should be able to mark the origin of the distinctive cycad leaf on Figure 31.6.
answer
Seed Plants > Gymnosperms > Cycadophyta (Cycads)
question
You should be able to predict how the ongoing and massive loss of plant species and plant communities will affect soils around the world.
answer
Rates of soil formation will decline; rates of soil loss will increase.
question
You should be able to describe the synapomorphies that define all green algae and land plants.
answer
All green algae and land plants contain chlorophyll a and b, have similar arrangements of thylakoid membranes, and store starch.
question
You should be able to discuss (compare and contrast) the advantages and disadvantages of having spores or seeds serve as the dispersal stage in a plant life cycle.
answer
Both spores and seeds have a tough, protective coat, so they can survive while being dispersed to a new location. Seeds have the advantage of carrying a store of nutrients with them -- when a spore germinates, it must makes its own food via photosynthesis right away.
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