Chapter 30

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The following question refers to the generalized life cycle for land plants shown in the figure. Each number within a circle or square represents a specific plant or plant part, and each number over an arrow represents either meiosis, mitosis, or fertilization. In the figure, which number represents an embryo?

In onions (Allium), cells of the sporophyte have 16 chromosomes within each nucleus. Match the number of chromosomes present in each of the following onion tissues. How many chromosomes should be in a megasporangium nucleus?

Arrange the following in the correct sequence, from earliest to most recent, in which these plant traits originated. 1. sporophyte dominance, gametophyte independence 2. sporophyte dominance, gametophyte dependence 3. gametophyte dominance, sporophyte dependence

3 → 1 → 2

Suppose that the cells of seed plants, like the skin cells of humans, produce a pigment upon increased exposure to UV radiation. Rank the following cells, from greatest to least, in terms of the likelihood of producing this pigment. 1. cells of sporangium 2. cells in the interior of a subterranean root 3. epidermal cells of sporophyte megaphylls 4. cells of a gametophyte

3,1,4,2

In a typical angiosperm, what is the sequence of structures encountered by the tip of a growing pollen tube on its way to the egg? 1. micropyle 2. style 3. ovary 4. stigma

4 → 2 → 3 → 1

Within a gymnosperm megasporangium, what is the correct sequence in which the following should appear during development, assuming that fertilization occurs? 1. sporophyte embryo 2. female gametophyte 3. egg cell 4. megaspore

4 → 2 → 3 → 1

Arrange the following structures from largest to smallest, assuming that they belong to two generations of the same angiosperm. 1. ovary 2. ovule 3. egg 4. carpel 5. embryo sac

4,1,2,5,3

Ovules are found within structure _____.

Which of these structures is a separate generation from the plant sporophyte?

A male gametophyte within a pollen grain

In which of the following pairs do the structures play comparable roles in the plant and animal life cycles? Select all that apply.

A plant sporophyte and an adult animal

Consider the seed shown in this figure. Select the correct description of this seed.

A seed includes contributions from three separate generations of plants.

Which of the following statements is true of the pine life cycle?

Conifer pollen grains contain male gametophytes.

Select the correct statement describing the life cycle of angiosperms.

Double fertilization in the life cycle of seed plants results in the production of a diploid zygote and a triploid endosperm nucleus.

Which of the following is not a characteristic that distinguishes gymnosperms and angiosperms from other plants?

alternation of generations

Human survival literally depends on the produce of _____.

angiosperms

A stamen consists of _____.

anther and filament

In pines, the female gametophyte contains _____, each of which contains a(n) _____.

archegonia ... egg

Over human history, which process has been most important in improving the features of plants that have long been used by humans as staple foods?

artificial selection

How have fruits contributed to the success of angiosperms?

by facilitating dispersal of seeds

All of the following cellular structures are functionally important in cells of the gametophytes of both angiosperms and gymnosperms except

chloroplasts

Cutting down rain forests can lead to

decreased rainfall

When you look at a pine or maple tree, the plant you see is a _____.

diploid sporophyte

Which of these is unique to flowering plants?

double fertilization

Which of the following is a characteristic of all angiosperms?

double internal fertilization

Match the animal features with the appropriate angiosperm analog. Oviparous (egg-laying) animals have internal fertilization (sperm cells encounter eggs within the female's body). Yolk and/or albumen is (are) provided to the embryo, and a shell is then deposited around the embryo and its food source. Eggs are subsequently deposited in an environment that promotes their further development, or are incubated by one or both parents. The yolk and/or albumen of an animal egg is what type of angiosperm analog?

endosperm

In pine, the embryo develops within the _____.

female gametophyte

In gymnosperms megaspores develop into _____.

female gametophytes

Which of the following sex and generation combinations most directly produces the fruit?

female sporophyte

Which of the following sex and generation combinations most directly produces the integument of a pine seed?

female sporophyte

Which of the following sex and generation combinations most directly produces the megasporangium of pine ovules?

female sporophyte

Which group is noted for the independence of gametophyte and sporophyte generations from each other?

ferns

In terms of alternation of generations, the internal parts of the pollen grains of seed-producing plants are most similar to a

ferns gametophyte bearing only antheridia

Angiosperms are different from all other plants because only they have _____.

flowers

Angiosperms are the most successful terrestrial plants. Which of the following features is unique to them and helps account for their success?

fruits enclosing seeds

In the pine, microsporangia form _____ microspores by _____.

haploid ... meiosis

Gymnosperms differ from both extinct and extant (living) ferns because they

have pollen

What is the greatest threat to plant diversity?

human population growth

In pines, an embryo is a(n) _____.

immature sporophyte

Generally, wind pollination is most likely to be found in seed plants that grow

in dense, single-species stands.

With respect to angiosperms, which of the following is incorrectly paired with its chromosome count?

megaspore-2n

In pine trees, pollen grains get to the ovule via the _____.

micropyle

mitosis

Carpels and stamens are

modified sporophylls

A botanist was visiting a tropical region for the purpose of discovering plants with medicinal properties. All of the following might be ways of identifying potentially useful plants except

observing which plants are the most used food plants.

Of the four haploid cells produced by a pine cone's megasporocyte (megaspore mother cell), _____ survive(s).

one

Unlike most angiosperms, grasses are pollinated by wind. As a consequence, some unnecessary parts of grass flowers have almost disappeared. Which of the following parts would you expect to be most reduced in a grass flower?

petals

Harold and Kumar are pre-med and pre-pharmacy students, respectively. They complain to their biology professor that they should not have to study about plants because plants have little relevance to their chosen professions. Kumar, especially, might be well advised to learn more about

plant secondary compounds.

In addition to seeds, which of the following characteristics is unique to the seed-producing plants?

pollen

The adaptation that made possible the colonization of dry land environments by seed plants is most likely the result of the evolution of _____.

pollen

The male gametophytes of flowering plants are also referred to as _____.

pollen grains

Match the animal features with the appropriate angiosperm analog. Oviparous (egg-laying) animals have internal fertilization (sperm cells encounter eggs within the female's body). Yolk and/or albumen is (are) provided to the embryo, and a shell is then deposited around the embryo and its food source. Eggs are subsequently deposited in an environment that promotes their further development, or are incubated by one or both parents. The internal fertilization that occurs prior to shell deposition is what type of angiosperm analog?

pollen tube and sperm nuclei

Which of the following are structures of angiosperm gametophytes?

pollen tubes

The question refers to the following description. The cycads, a mostly tropical phylum of gymnosperms, evolved about 300 million years ago and were dominant forms during the Age of the Dinosaurs. Though their sperm are flagellated, their ovules are pollinated by beetles. These beetles get nutrition (they eat pollen) and shelter from the microsporophylls. Upon visiting megasporophylls, the beetles transfer pollen to the exposed ovules. In cycads, pollen cones and seed cones are borne on different plants. Cycads synthesize neurotoxins, especially in the seeds, that are effective against most animals, including humans. On the Pacific island of Guam, large herbivorous bats called "flying foxes" commonly feed on cycad seeds, a potent source of neurotoxins. The flying foxes do not visit male cones. Consequently, what should be true?

Flying foxes can be dispersal agents of cycad seeds if the seeds sometimes get swallowed whole (in other words, without getting chewed).

The fruit of the mistletoe, a parasitic angiosperm, is a one-seeded berry. In members of the genus Viscum, the outside of the seed is viscous (sticky), which permits the seed to adhere to surfaces, such as the branches of host plants or the beaks of birds. What should be expected of the fruit if the viscosity of Viscum seeds is primarily an adaptation for dispersal rather than an adaptation for infecting host plant tissues?

It should be nutritious

What are the products of meiosis in the life cycle of a seed plant?

Megaspores or microspores

Gymnosperms were most abundant during the _____.

Mesozoic

Which of the following statements correctly describes a portion of the pine life cycle?

Female gametophytes use mitosis to produce eggs.

Which of the following is true concerning flowering plants?

The flower includes sporophyte tissue.

What is true of stamens, sepals, petals, carpels, and pinecone scales?

They are modified leaves.

Harold and Kumar are pre-med and pre-pharmacy students, respectively. They complain to their biology professor that they should not have to study about plants because plants have little relevance to their chosen professions. Which adaptation(s) of land plants is (are) likely to provide Harold with future patients?

Two of the responses above are potentially medically significant.

A fruit is most commonly

a mature ovary

In seed plants, which of the following is part of a pollen grain and has a function most like that of the seed coat?

sporopollenin

A carpel is composed of _____.

stigma, style, and ovary

A botanist discovers a new species of land plant with a dominant sporophyte, chlorophylls a and b, and cell walls made of cellulose. In assigning this plant to a phylum, which of the following, if present, would be least useful?

spores

The Brazil nut tree, Bertholletia excels (n = 17), is native to tropical rain forests of South America. It is a hardwood tree that can grow to over 50 meters tall, is a source of high-quality lumber, and is a favorite nesting site for harpy eagles. As the rainy season ends, tough-walled fruits, each containing 8-25 seeds (Brazil nuts), fall to the forest floor. Brazil nuts are composed primarily of endosperm. About $50 million worth of nuts are harvested each year. Scientists have discovered that the pale yellow flowers of Brazil nut trees cannot fertilize themselves and admit only female orchid bees as pollinators. The agouti (Dasyprocta spp.), a cat-sized rodent, is the only animal with teeth strong enough to crack the hard wall of Brazil nut fruits. It typically eats some of the seeds, buries others, and leaves still others inside the fruit, which moisture can now enter. The uneaten seeds may subsequently germinate. The same bees that pollinate the flowers of the Brazil nut trees pollinate orchids, which are epiphytes (in other words, plants that grow on other plants); however, orchids cannot grow on Brazil nut trees. These observations explain

why Brazil nut trees do not set fruit in monoculture plantations.

Where in an angiosperm would you find a megasporangium?

within an ovule contained within an ovary of a flower

Which of these structures contains a male gametophyte?

Which of these statements is true about the gametophyte tissue that surrounds the pine embryo?

It functions as a haploid food reserve

The cycads, a mostly tropical phylum of gymnosperms, evolved about 300 million years ago and were dominant forms during the Age of the Dinosaurs. Though their sperm are flagellated, their ovules are pollinated by beetles. These beetles get nutrition (they eat pollen) and shelter from the microsporophylls. Upon visiting megasporophylls, the beetles transfer pollen to the exposed ovules. In cycads, pollen cones and seed cones are borne on different plants. Cycads synthesize neurotoxins, especially in the seeds, that are effective against most animals, including humans. If one were to erect a new taxon of plants that included all plants that are pollinated by animals, and only plants that are pollinated by animals, then this new taxon would be

polyphyletic

The seed coat's most important function is to provide

protection for the embryo

Which structure(s) must pass through the micropyle for successful double fertilization to occur in angiosperms?

the pollen tube and two sperm nuclei

Which trait(s) is (are) shared by many modern gymnosperms and angiosperms? 1. pollen transported by wind 2. lignified xylem 3. microscopic gametophytes 4. sterile sporophylls, modified to attract pollinators 5. endosperm

1,2, and 3

Part complete The cutting and burning of tropical rain forests leads to which of the following? 1. addition of CO2 to the atmosphere 2. decreased removal of CO2 from the atmosphere 3. greenhouse effect 4. global warming 5. decreasing sea level

1,2,3, and 4

Arrange the following structures, which can be found on male pine trees, from the largest structure to the smallest structure (or from most inclusive to least inclusive). 1. sporophyte 2. microspores 3. microsporangia 4. pollen cone 5. pollen nuclei

1,4,3,2,5

The Brazil nut tree, Bertholletia excels (n = 17), is native to tropical rain forests of South America. It is a hardwood tree that can grow to over 50 meters tall, is a source of high-quality lumber, and is a favorite nesting site for harpy eagles. As the rainy season ends, tough-walled fruits, each containing 8-25 seeds (Brazil nuts), fall to the forest floor. Brazil nuts are composed primarily of endosperm. About $50 million worth of nuts are harvested each year. Scientists have discovered that the pale yellow flowers of Brazil nut trees cannot fertilize themselves and admit only female orchid bees as pollinators. The agouti (Dasyprocta spp.), a cat-sized rodent, is the only animal with teeth strong enough to crack the hard wall of Brazil nut fruits. It typically eats some of the seeds, buries others, and leaves still others inside the fruit, which moisture can now enter. The uneaten seeds may subsequently germinate. The taller a Brazil nut tree is, 1. the more valuable it is as a source of lumber. 2. the less useful it is to harpy eagles. 3. the greater its photosynthetic rate relative to neighboring plants.

1 and 3

The cycads, a mostly tropical phylum of gymnosperms, evolved about 300 million years ago and were dominant forms during the Age of the Dinosaurs. Though their sperm are flagellated, their ovules are pollinated by beetles. These beetles get nutrition (they eat pollen) and shelter from the microsporophylls. Upon visiting megasporophylls, the beetles transfer pollen to the exposed ovules. In cycads, pollen cones and seed cones are borne on different plants. Cycads synthesize neurotoxins, especially in the seeds, that are effective against most animals, including humans. Which feature of cycads distinguishes them from most other gymnosperms? 1. They have exposed ovules. 2. They have flagellated sperm. 3. They are pollinated by animals.

2 and 3

Among plants known as legumes (beans, peas, alfalfa, clover, etc.) the seeds are contained in a fruit that is itself called a legume, better known as a pod. Upon opening such pods, it is commonly observed that some ovules have become mature seeds, whereas other ovules have not. Thus, which of the following statements is (are) true? 1. The flowers that gave rise to such pods were not pollinated. 2. Pollen tubes did not enter all of the ovules in such pods. 3. There was apparently not enough endosperm to distribute to all of the ovules in such pods. 4. The ovules that failed to develop into seeds were derived from sterile floral parts. 5. Fruit can develop, even if all ovules within have not been fertilized.

2 and 5

What adaptations should one expect of the seed coats of angiosperm species whose seeds are dispersed by frugivorous (fruit-eating) animals, as opposed to angiosperm species whose seeds are dispersed by other means? 1. The exterior of the seed coat should have barbs or hooks. 2. The seed coat should contain secondary compounds that irritate the lining of the animal's mouth. 3. The seed coat should be able to withstand low pH's. 4. The seed coat, upon its complete digestion, should provide vitamins or nutrients to animals. 5. The seed coat should be resistant to the animals' digestive enzymes.

3 and 5

The cycads, a mostly tropical phylum of gymnosperms, evolved about 300 million years ago and were dominant forms during the Age of the Dinosaurs. Though their sperm are flagellated, their ovules are pollinated by beetles. These beetles get nutrition (they eat pollen) and shelter from the microsporophylls. Upon visiting megasporophylls, the beetles transfer pollen to the exposed ovules. In cycads, pollen cones and seed cones are borne on different plants. Cycads synthesize neurotoxins, especially in the seeds, that are effective against most animals, including humans. Which feature of cycads makes them similar to many angiosperms? 1. They have exposed ovules. 2. They have flagellated sperm. 3. They are pollinated by animals.

3 only

The Brazil nut tree, Bertholletia excels (n = 17), is native to tropical rain forests of South America. It is a hardwood tree that can grow to over 50 meters tall, is a source of high-quality lumber, and is a favorite nesting site for harpy eagles. As the rainy season ends, tough-walled fruits, each containing 8-25 seeds (Brazil nuts), fall to the forest floor. Brazil nuts are composed primarily of endosperm. About $50 million worth of nuts are harvested each year. Scientists have discovered that the pale yellow flowers of Brazil nut trees cannot fertilize themselves and admit only female orchid bees as pollinators. The agouti (Dasyprocta spp.), a cat-sized rodent, is the only animal with teeth strong enough to crack the hard wall of Brazil nut fruits. It typically eats some of the seeds, buries others, and leaves still others inside the fruit, which moisture can now enter. The uneaten seeds may subsequently germinate. If a female orchid bee has just left a Brazil nut tree with nectar in her stomach, and if she visits another flower on a different Brazil nut tree, what is the sequence in which the following events should occur? 1. double fertilization 2. pollen tube emerges from pollen grain 3. pollen tube enters micropyle 4. pollination

4,2,3,1

The Brazil nut tree, Bertholletia excels (n = 17), is native to tropical rain forests of South America. It is a hardwood tree that can grow to over 50 meters tall, is a source of high-quality lumber, and is a favorite nesting site for harpy eagles. As the rainy season ends, tough-walled fruits, each containing 8-25 seeds (Brazil nuts), fall to the forest floor. Brazil nuts are composed primarily of endosperm. About $50 million worth of nuts are harvested each year. Scientists have discovered that the pale yellow flowers of Brazil nut trees cannot fertilize themselves and admit only female orchid bees as pollinators. The agouti (Dasyprocta spp.), a cat-sized rodent, is the only animal with teeth strong enough to crack the hard wall of Brazil nut fruits. It typically eats some of the seeds, buries others, and leaves still others inside the fruit, which moisture can now enter. The uneaten seeds may subsequently germinate. Animals that consume Brazil nuts are deriving nutrition mostly from tissue whose nuclei have how many chromosomes?

Harold and Kumar are pre-med and pre-pharmacy students, respectively. They complain to their biology professor that they should not have to study about plants because plants have little relevance to their chosen professions. From reading their biology textbook, what would Harold and Kumar discover?

About one-quarter of all prescription drugs come from seed plants.

Which of the following is a true statement about angiosperm carpels?

Carpels surround and nourish the female gametophyte.

A researcher has developed two stains for use with seed plants. One stains sporophyte tissue blue; the other stains gametophyte tissue red. If the researcher exposes pollen grains to both stains, and then rinses away the excess stain, what should occur?

The pollen grains will have red interiors and blue exteriors.

Which of the following statements is true of monocots?

They, along with the eudicots, magnoliids, and basal angiosperms, are currently placed in the phylum Anthophyta.

The Brazil nut tree, Bertholletia excels (n = 17), is native to tropical rain forests of South America. It is a hardwood tree that can grow to over 50 meters tall, is a source of high-quality lumber, and is a favorite nesting site for harpy eagles. As the rainy season ends, tough-walled fruits, each containing 8-25 seeds (Brazil nuts), fall to the forest floor. Brazil nuts are composed primarily of endosperm. About $50 million worth of nuts are harvested each year. Scientists have discovered that the pale yellow flowers of Brazil nut trees cannot fertilize themselves and admit only female orchid bees as pollinators. The agouti (Dasyprocta spp.), a cat-sized rodent, is the only animal with teeth strong enough to crack the hard wall of Brazil nut fruits. It typically eats some of the seeds, buries others, and leaves still others inside the fruit, which moisture can now enter. The uneaten seeds may subsequently germinate. People who attempted to plant Brazil nuts in hopes of establishing plantations of Brazil nut trees played roles most similar to those of

agoutis

All see plants _____.

are heterosporous

The Brazil nut tree, Bertholletia excels (n = 17), is native to tropical rain forests of South America. It is a hardwood tree that can grow to over 50 meters tall, is a source of high-quality lumber, and is a favorite nesting site for harpy eagles. As the rainy season ends, tough-walled fruits, each containing 8-25 seeds (Brazil nuts), fall to the forest floor. Brazil nuts are composed primarily of endosperm. About $50 million worth of nuts are harvested each year. Scientists have discovered that the pale yellow flowers of Brazil nut trees cannot fertilize themselves and admit only female orchid bees as pollinators. The agouti (Dasyprocta spp.), a cat-sized rodent, is the only animal with teeth strong enough to crack the hard wall of Brazil nut fruits. It typically eats some of the seeds, buries others, and leaves still others inside the fruit, which moisture can now enter. The uneaten seeds may subsequently germinate. Orchid bees are to Brazil nut trees as ________ are to pine trees.

breezes

Hypothetically, one of the major benefits of double fertilization in angiosperms is to

coordinate developmental timing between the embryo and its food stores.

Match the animal features with the appropriate angiosperm analog. Oviparous (egg-laying) animals have internal fertilization (sperm cells encounter eggs within the female's body). Yolk and/or albumen is (are) provided to the embryo, and a shell is then deposited around the embryo and its food source. Eggs are subsequently deposited in an environment that promotes their further development, or are incubated by one or both parents. The dispersal and/or nurture of young after hatching from the egg is what type of angiosperm analog?

fruit

The generative cell of male angiosperm gametophytes is haploid. This cell divides to produce two haploid sperm cells. What type of cell division does the generative cell undergo to produce these sperm cells?

mitosis

The Brazil nut tree, Bertholletia excels (n = 17), is native to tropical rain forests of South America. It is a hardwood tree that can grow to over 50 meters tall, is a source of high-quality lumber, and is a favorite nesting site for harpy eagles. As the rainy season ends, tough-walled fruits, each containing 8-25 seeds (Brazil nuts), fall to the forest floor. Brazil nuts are composed primarily of endosperm. About $50 million worth of nuts are harvested each year. Scientists have discovered that the pale yellow flowers of Brazil nut trees cannot fertilize themselves and admit only female orchid bees as pollinators. The agouti (Dasyprocta spp.), a cat-sized rodent, is the only animal with teeth strong enough to crack the hard wall of Brazil nut fruits. It typically eats some of the seeds, buries others, and leaves still others inside the fruit, which moisture can now enter. The uneaten seeds may subsequently germinate. The harpy eagle, Harpia harpyja, is the largest, most powerful raptor in the Americas. It nests only in trees taller than 25 meters. It is a "sloth specialist," but will also take agouti. Thus, if these eagles capture too many agoutis from a particular locale, they might contribute to their own demise by

increasing habitat loss

Many mammals have skins and mucous membranes that are sensitive to phenolic secretions of plants like poison oak (Rhus). These secondary compounds are primarily adaptations that

inhibit herbivory

Which of the following is most important in making the typical seed more resistant to adverse conditions than the typical spore?

integument(s)

Match the animal features with the appropriate angiosperm analog. Oviparous (egg-laying) animals have internal fertilization (sperm cells encounter eggs within the female's body). Yolk and/or albumen is (are) provided to the embryo, and a shell is then deposited around the embryo and its food source. Eggs are subsequently deposited in an environment that promotes their further development, or are incubated by one or both parents. The shell of an animal egg is what type of angiosperm analog?

integuments

Reptilian embryos are protected from desiccation by a leathery shell. Similarly, which pair of structures protects seed plants' embryos and male gametophytes, respectively, from desiccation?

integuments-sporopollenin

Which of the following sex and generation combinations most directly produces the pollen tube?

male gametophyte

Angiosperm double fertilization is so-called because it features the formation of

one embryo involving one sperm cell and an endosperm involving a second sperm cell.

Gymnosperms and angiosperms have the following in common except

ovaries

Which of the following flower parts develops into the pulp of a fleshy fruit?

ovary

Which of the following flower parts develops into a seed?

ovule

Which structure is common to both gymnosperms and angiosperms?

ovule

Which of the following can be found in gymnosperms?

pollen

The Brazil nut tree, Bertholletia excels (n = 17), is native to tropical rain forests of South America. It is a hardwood tree that can grow to over 50 meters tall, is a source of high-quality lumber, and is a favorite nesting site for harpy eagles. As the rainy season ends, tough-walled fruits, each containing 8-25 seeds (Brazil nuts), fall to the forest floor. Brazil nuts are composed primarily of endosperm. About $50 million worth of nuts are harvested each year. Scientists have discovered that the pale yellow flowers of Brazil nut trees cannot fertilize themselves and admit only female orchid bees as pollinators. The agouti (Dasyprocta spp.), a cat-sized rodent, is the only animal with teeth strong enough to crack the hard wall of Brazil nut fruits. It typically eats some of the seeds, buries others, and leaves still others inside the fruit, which moisture can now enter. The uneaten seeds may subsequently germinate. Entrepreneurs attempted, but failed, to harvest nuts from plantations grown in Southeast Asia. Attempts to grow Brazil nut trees in South American plantations also failed. In both cases, the trees grew vigorously, produced healthy flowers in profusion, but set no fruit. Consequently, what is the likely source of the problem?

pollination failure

The major difference between angiosperms and gymnosperms comes from the _____.

presence or absence of a protective covering over the ovule

In flowering plants the integuments of the ovule develop into a(n) _____.

seed coat

The Brazil nut tree, Bertholletia excels (n = 17), is native to tropical rain forests of South America. It is a hardwood tree that can grow to over 50 meters tall, is a source of high-quality lumber, and is a favorite nesting site for harpy eagles. As the rainy season ends, tough-walled fruits, each containing 8-25 seeds (Brazil nuts), fall to the forest floor. Brazil nuts are composed primarily of endosperm. About $50 million worth of nuts are harvested each year. Scientists have discovered that the pale yellow flowers of Brazil nut trees cannot fertilize themselves and admit only female orchid bees as pollinators. The agouti (Dasyprocta spp.), a cat-sized rodent, is the only animal with teeth strong enough to crack the hard wall of Brazil nut fruits. It typically eats some of the seeds, buries others, and leaves still others inside the fruit, which moisture can now enter. The uneaten seeds may subsequently germinate. The agouti is most directly involved with the Brazil nut tree's dispersal of

sporophyte embryos

In angiosperms, pollination is the transfer of pollen grain to the _____ of a flower on the same plant or another plant of the same species.

stigma

The Brazil nut tree, Bertholletia excels (n = 17), is native to tropical rain forests of South America. It is a hardwood tree that can grow to over 50 meters tall, is a source of high-quality lumber, and is a favorite nesting site for harpy eagles. As the rainy season ends, tough-walled fruits, each containing 8-25 seeds (Brazil nuts), fall to the forest floor. Brazil nuts are composed primarily of endosperm. About $50 million worth of nuts are harvested each year. Scientists have discovered that the pale yellow flowers of Brazil nut trees cannot fertilize themselves and admit only female orchid bees as pollinators. The agouti (Dasyprocta spp.), a cat-sized rodent, is the only animal with teeth strong enough to crack the hard wall of Brazil nut fruits. It typically eats some of the seeds, buries others, and leaves still others inside the fruit, which moisture can now enter. The uneaten seeds may subsequently germinate. Native peoples traditionally use Brazil nuts to treat stomach ache, inflammation, hypersensitivity, and hepatitis. Consequently, a scientist should be interested in promoting

the evaluation of Brazil nut chemicals for use as potential drugs.

The cycads, a mostly tropical phylum of gymnosperms, evolved about 300 million years ago and were dominant forms during the Age of the Dinosaurs. Though their sperm are flagellated, their ovules are pollinated by beetles. These beetles get nutrition (they eat pollen) and shelter from the microsporophylls. Upon visiting megasporophylls, the beetles transfer pollen to the exposed ovules. In cycads, pollen cones and seed cones are borne on different plants. Cycads synthesize neurotoxins, especially in the seeds, that are effective against most animals, including humans. If the beetles survive by consuming cycad pollen, then whether the beetles should be considered mutualists with, or parasites of, the cycads depends upon

Chapter 30

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