Chapter 32: Evolution and Diversity of Modern Gymnosperms and Angiosperms (Part 1, Week 6)

Question 1

What are particularily important in our everyday lives because they are the sources of many products, including wood, paper, beverages, food, cosmetics, and medicine?

Answer 1

The seed plants–Gymnosperms and Angiosperms

Question 2

What are some examples of seed plants helping in medicine?

All of these are secondary metabolites which are distinct from the products of primary metabolism (carbs, lipids, proteins, and nucleic acids).

Answer 2

Madagascar periwinkles provide extracts for leukemia and lymphatic cancers.

Taxol, found in the bark of Pacific yew tress, is used to treat breast and ovarian cancers.

Question 3

T/F Secondary metabolites are particularily diverse in gymnosperms and angiosperms.

Answer 3

True. Their roles help in protecting plants from disease-causing organisms and plant-eating animals, and also aid plant growth and reproduction.

Question 4

[Start 32.1 Overview of Seed Plant Diversity]

What did gymnosperms originate from?

Answer 4

Now extinct seedless plants known as progymnosperms.

These were woody, representing the first trees.

Few gymnosperm, especially conifers, exist today.

Question 5

T/F Angiosperms arose from an unknown gymnosperm lineage, thereby inheriting the capacity to produce wood and other seed plant features.

Answer 5

True

Question 6

[Start 32.2 The Evolution and Diversity of Modern Gymnosperms]

What is a plant that produces seeds that are exposed rather than seeds enclosed in fruits?

Answer 6

Gymnosperms Greek gymnos, meaning naked (referring to the unclothed state of ancient athletes), and sperma, meaning seed.

Question 7

What do most modern gymnosperms occur as?

Answer 7

Woody plants such as shrubs or trees.

Question 8

What modern gymnosperms include that are native to the Sierra Nevada mountains of the western U.S. and are among Earth’s largest organisms weighing as much as 6,000 tons and reaching an amazing 100 m in height?

Answer 8

Famous giant sequoias (Sequoiadendron giganteum)

Question 9

What is a secondary plant tissue composed of numerous pipelike arrays of empty, water-conducting cells whose walls are strengthened by an exceptionally tough polymer known as lignin?

The large size of the sequoias and other trees is based on the prescence of this!

Answer 9

Wood

These properties enable woody tissues to transport water upward for great distances and also to provide the structural support needed for trees to grow tall and produce many branches and leaves.

Question 10

In modern seed plants, what is a special tissue that produces both thick layers of wood and thinner layers of inner bark?

Answer 10

Vascular cambium

A secondary meristematic tissue of seed plants.

Question 11

What is a thin layer of secondary phloem that transports watery solutions of organic compounds in a woody stem?

Answer 11

Inner bark

Question 12

What helps gymnosperms and woody angiosperms to compete effectively for light and other resources needed for photosynthesis? (3)

Answer 12

Vascular cambium, wood, and inner bark.

Question 13

How did the vascular tissue of progymnosperms (first trees with leafy tiwgs; from Greek meaning before gymnosperms) differ from earlier vascular plants?

Answer 13

The vascular tissue of progymnosperms differed from that of earlier vascular plants in being arranged in a ring around a central pith of nonvascular tissue.

This is called an eustele.

Question 14

What are regarded as the earliest diverging modern gymnosperm phylum, originating more than 300 mya?

Answer 14

Cycads (cycad comes from a Greek word meaning palm)

Nearly 300 cycad species occur today, primarily in tropical and subtropical regions.

Many cycads are listed as endangered, and commercial trade in cycads is regulated by CITES (Convention on International Trade in Endangered Species of WildFauna and Flora), a voluntary international agreement between governments to protect such species.

Question 15

Bonus Question! Are palm trees and cycads the same thing?

Answer 15

No, because cycads (which are gymnosperms) do not produce flowers while palm trees do.

Question 16

What do cycads produce that are extended above ground and have branching shapes resembling corals?

What do they harbor within themselves?

Answer 16

Coralloid roots

Coralloid roots harbor light-dependent, photosynthetic cyanobacteria within their tissues. The cyanobacteria, which form a bright blue-green ring beneath the root surfaces, convert atmospheric nitrogen (N2) into ammmonia (NH3), providing their plant hosts with the nitrogen that is crucial to growth.

Question 17

How is cycad reproduction unique?

Answer 17

They produce conspicuous conelike structures that bear either ovules and seeds or pollen.

When matured, they emit odors to attract beetles that carry pollen to the ovules where the pollen produces tubes that deliver sperm to eggs.

Question 18

What is the single remaining species of a phylum that was much more diverse during the Age of Dinosaurs?

Its species name from the two-lobedshape of its leaves, which have unusual forked veins

Answer 18

Ginkgo bilboa trees

Question 19

What is an interesting fact about G. bilboa trees and how they came to be widely cultivated today?

Answer 19

They descended from seeds produced by a tree found in a remote Japanese temple garden and brought to Europe by 17th-century explorers.

Question 20

Why are Gingko seeds often mistaken as fruits?

Answer 20

Because of their colorful appearance. They have fleshy, foul-smelling seed coats.

Question 21

What are G. biloba trees widely planted along city streets? (2)

Answer 21

1. Because they areornamental and also tolerate cold, heat, and pollution better than manyother trees.
2. In addition, these trees are long-lived—individuals can live for more than a thousand years and grow to 30 m in height.

Question 22

T/F G. biloba trees can have a specific sex.

Answer 22

True.

Individual trees produce either ovules and seeds or pollen, based on a sex chromosome system much like that of humans.

Ovule-producing trees have two X chromosomes; pollen-producing trees have one X and one Y chromosome.

Question 23

How does a G. biloba tree reproduce?

Answer 23

• Wind disperse pollen to ovules which then germinate and grow through ovule tissues for several months.
• The tubes burst, delivering flagellate sperm to egg cells.
• After fertilization, zygotes develop into embryos, and the ovule integument develops into a fleshy, foul-smelling outer seed coat and a hard inner seed coat.

Question 24

What is the lineage of trees named for their seed cones, of which pinecones are familiar examples?

Answer 24

Conifers! More than 50 genera.

Question 25

T/F All conifers are deciduous.

Answer 25

False. Some are and some are not. Deciduous means that they drop all of their leaves in the fall.

Question 26

Since confiers develop simple pollen cones and more complex ovule-bearing cones, how do you distinguish between the two?

Answer 26

- For simple pollen cones, have many leaflike structures, each bearing a microsporangium in which meiosis occurs and pollen grains develop. - For the more complex ovule-bearing cones, also called seed cones, are composed of many short branch systems that bear ovules. These ovules contain female gametophytes, within which eggs develop.

Question 27

Information to better understand conifer reproduction terms! 1. Mature sporophyte produces 2 types of cones: Ovule cones (2n) and Pollen cones (2n). 2a. For ovule cones, megaspores (n) are produced by meiosis within megasporangia. - Within the scales of the cone, the megasporangium is the structure of the plant body that contains the female reproductive organ, which is the megaspore itself! - This whole structure to include the scale can be called the ovule. 2b. For pollen cones, microspores (n) are produced by meiosis within microsporangia. - Within the scales of the cone, like you might think, the microsporangia is the structure of the plant body that contains the male reproductive organ, which is the micropores themselves! 3a. The megaspores then undergo mitosis and produce female gametophytes that containing eggs within archegonia. - Again, this whole structure is considered as the ovule. - To image this, think of the russian nesting doll. The integument (which comes from the scale) covers the entire ovule except for the small opening for fertilization. Just inside the integument, lies the megasporangium (2n). Then the female gametophyte (n) and the two archegoniums (n) containing 1 egg (n) a piece. 3b. The microspores undergo mitosis as well, and develop into pollen grains, which are are young male gametophytes (not yet mature!) - The microsporangium is lost, and the pollen grains are dispersed into the wind and encounter ovules. 4. The pollen grain's male gametophyte (with its antheridium which is the equivalent to the female archegonium that houses the egg cells) matures, producing sperm cells in a pollen tube. 5. The pollen tube delivers sperm to eggs, where fertilization occurs. Only 1 egg per ovule is fertilized and develops! 6. After fertilization, the zygote (diploid cell resulting from the fusion of two haploid gametes (sperm and egg)), produces an embryo within a seed. Mature seeds are then dispersed. 7. Seeds germinate, and embryo sporophytes grow into seedlings! THIS process takes 2 years! From gamete development to seed development!

Answer 27

N/A

Question 28

What are the specialized vascular cells within the wood of conifers that are efficient water and mineral conduction even in dry conditions?

Answer 28

Tracheids Like the tracheids of other vascular plants, those of conifers are devoid of cytoplasm and occur in long columns that function like plumbing pipelines

Question 29

What do tracheids possess in their side and end walls that are circular which allow water to move both vertically and laterally from one tracheid to another?

Answer 29

Pits Definition - A thin-walled circular area in a plant cell wall where secondary wall materials such as lignin are absent and through which water moves.

Question 30

What is the nonporous, flexible central region of a conifer pit that functions like a valve?

Answer 30

The torus (plural, tori)

Question 31

Why does the presence of tori within the tracheids of conifers help explain why they have been successful for hundereds of millions of years?

Answer 31

When tracheids are dry in arid or cold habitats, they fill with air and cannot conduct water. For this, the torus presses against the pit opening, sealing it. This conifer adaptation localizes air bubbles, preventing them from stopping water conduction in other tracheids.

Question 32

What do the conspicuous resin ducts that be display on conifer woods and leaves accomplish?

Answer 32

Flow of syrup-like resin that helps prevent attack by pathogens and herbivores. Resin that exudes from tree surfaces may trap insects and other organisms, then harden in the air and fossilize, preserving the inclusions in amber.

Question 33

What helps confiers shed snow, preventing heavy snow accumulations from breaking branches?

Answer 33

Their conical shapes and flexible branches.

Question 34

What helps confiers survive when liquid water is scarce? What about attack by organisms?

Answer 34

Their leaves are scale-like or needle-shaped, which reduces surface area of the leaves from which water could evaporate. In addition, a thick, waxy cuticle coats conifer leaf surfaces retarding water loss and attack by disease organisms.

Question 35

What is a benefit of the fact that many confiers are evergreen?

Answer 35

Leaves live for more than 1 year and do not shed all in one season like deciduous trees. This allows them to start photosynthesis earlier. Advantage in the short growth season of alpine or high altitude environments.

Question 36

What is a conifer clade that has three genera, Gnetum, Ephedra, and Welwitschia?

Answer 36

Gnetales. Gnetum is unusual among modern gymnosperms in having broad leaves similar to those of many tropical plants. Such leavesmaximize light capture in dim forest habitats. More than 30 species of the genus Gnetum occur as vines, shrubs, or trees in tropical Africa or Asia. Ephedra, native to arid regions of the southwestern U.S., has tiny brown scalelike leaves and green, photosynthetic stems. These adaptations help the plant conserve water by preventing water loss that would otherwise occur from the surfaces of larger leaves. Ephedra produces secondary metabolites that aid in plant protection but also affect human physiology. Early settlers of the western U.S. used Ephedra to treat colds and other medical conditions. The modern decongestant drug pseudoephedrine is based on the chemical structure of ephedrine, a substance that was named for and originally obtained from Ephedra. Welwitschia has only one living representative species. Welwitschia mirabilis is a strange-looking plant that grows in the coastal Namib Desert of southwestern Africa, one of the driest places on Earth.

Question 37

[Start 32.3 The Evolution and Diversity of Modern Angiosperms] One extinct gymnosperm group, although it’s unclear which one, gave rise to the angiosperms—the flowering plants how many years ago?

Answer 37

124 mya

Question 38

What are the defining features of angiosperms?

Answer 38

Fruits and flowers Angiosperm is from the Greek words meaning enclosed seed, which reflects the presence of seeds within fruits. The seed nutritive material known as endosperm is another defining feature of the flowering plants.

Question 39

What helps seed production? What favors seed dispersal? What helps embryos within seeds to grow into seedlings?

Answer 39

Flowers, fruits, and endosperm.

Question 40

Most angiosperms possess distinctive water-conducting cells made up of aligned vessel elements called?

Answer 40

Vessels. Wider than tracheids and therefore increase the efficiency of water flow through plants. Relatively wide vessels are commonly present in the water transport tissues of angiosperms and much less commonly in other plants. The vessels occasionally found in nonangiosperms are thought to have evolved independently from those of angiosperms.

Question 41

What do all of the flavorings of our food, beverages, and spices come from within flowering plants that makes us rely on them more than gymnosperms?

Answer 41

Secondary metabolites.

Question 42

What is a reproductive shoot, a short stem branch bearing reproductive organs instead of leaves?

Answer 42

Flowers are complex reproductive structures that are specialized for the efficient production of pollen and seeds. The sexual reproduction process of angiosperms depends on flowers.

Question 43

Where are flowers produced at?

Answer 43

Stem tips

Question 44

What are the four types of flower organs?

Answer 44

Sepals, petals, pollen-producing stamens, and ovule-producing carpels.

Question 45

What is the enlarged region at the tip of a flower peduncle to which flower parts are attached?

Answer 45

Receptacle

Question 46

What is located at the tip of the flower stalk where the receptacle sits?

Answer 46

The pedicel.

Question 47

What explains why carpels are the most central flower organs, why stamens surround carpels, and why petals and sepals are the outermost flower organs?

Answer 47

The functioning of several genes that control flower organ development.

Question 48

What is a flower organ that usually serves to attract insects or other animals for pollen transport?

Answer 48

The petals Heavy role in pollination - The process in which pollen grains are transported to an angiosperm flower or a gymnosperm cone primarily by means of wind or animal pollinators.

Question 49

What is a flower structure that is often green and is part of the outer layer of a bud?

Answer 49

Sepals

Question 50

If sepals look like the petals of a flower (meaning they are not green), what do you then call the petals and sepals?

Answer 50

Tepals (collectively called the perianth) A flower perianth part that cannot be distinguished by appearance as a petal or a sepal.

Question 51

What is a flower organ that produces the male gametophytes, pollen?

Answer 51

Stamens

Question 52

What is a flower shoot organ that produces ovules that contain female gametophytes?

Answer 52

Carpels

Question 53

What do you call flowers that possess all four types of flower organs such as perianths, stamens, and carpels?

Answer 53

Complete flowers Book Definition A eudicot flower that possesses all four types of flower whorls or a monocot flower that has tepals, androecium, and gynoecium.

Question 54

What do you call flowers that lack all or some types of flower organs such as perianths, stamens, and carpels?

Answer 54

Incomplete flowers Book Definition A flower that lacks one or more of the four flower whorls.

Question 55

What do you call flowers that has both stamens and carpels?

Answer 55

perfect flower

Question 56

What do you call flowers that lacks either stamens or carpels?

Answer 56

imperfect flower

Question 57

What is a flower structure that may consist of a single carpel or multiple, fused carpels and is differentiated into stigma, style, and ovary?

Answer 57

pistil (from the Latin pistillum, meaning pestle) because of a resemblance to the device people use to grind materials to powder in a mortar.

Question 58

What is the correlation between flowers having one pistil versus flowers who have many pistils?

Answer 58

If one pistil is present, then flowers only have one carpel or fused carpels. Flowers will multiple pistils will display several carpels.

Question 59

What are the pistil's three structures and their distinct functions?

Answer 59

Stigma - the topmost portion of the pistil, which receives and recognizes pollen of the appropriate species or genotype. Style - the elongate portion of the pistil through which the pollen tube grows. Ovary - the lowermost portion of the pistil that encloses and protects the ovules.

Question 60

How many sperm cells are delivered to the ovules when the pollen tube growths through the style?

Answer 60

2

Question 61

Explain what double fertilization is in your own words, a distinctive angiosperm process.

Answer 61

One sperm fuses with the egg to form a zygote The second sperm fuses with haploid cells of the female gametophyte

Question 62

Which step in double fertilization is the one that develops the angiospem characteristic of nutritive tissue known as the endosperm?

Answer 62

The sperm that fuses with the haploid cells of the female gametophyte.

Question 63

What happens when the zygote is fed by the endosperm?

Answer 63

The zygote develops into an embryo, and the ovule develops into a seed. The ovaries develop into fruits.

Question 64

What do structural comparisons and molecular data indicate that stamens are homologous to?

Answer 64

Gymnosperm microsporophylls, leaflike structures that produce microspores (young pollen). During angiosperm evolution, the stamens of most modern plants have narrowed to form filaments, or stalks, that elevate anthers, clusters of microsporangia that produce pollen and then open to release it. Filaments and anthers are adaptations that foster pollen dispersal.

Question 65

What do structural comparisons and molecular data indicate that carpels are homologous to?

Answer 65

To gymnosperm megasporophylls, leaflike structures that bear ovules on their surfaces. In early angiosperms, such leaves folded over ovules, protecting them. In support of this hypothesis is the observation that the carpels of some early-diverging modern plants are leaflike structures that fold over ovules, with the carpel edges stuck together by secretions During evolution, this folding resulted in carpels that developed specialized regions and completely enclosed ovules. Most modern flowers produce carpels whose edges have fused together into a tube whose lower portion (ovary) encloses ovules. Plant biologists hypothesize that such evolutionary change increased ovule protection, which would improve plant fitness.

Question 66

What is interesting about flower sepals and petals involving their evoluntionary history?

Answer 66

In contrast, flower sepals and petals have no recognizable homologs in modern gymnosperms. These perianth structures are unique to angiosperms, so plant biologists have long wondered how sepals and petals arose.

Question 67

What are the one of two largest lineages of flowering plants in which the embryo possesses a single seed leaf? One of the two largest lineages of flowering plants in which the embryo possesses two seed leaves?

Answer 67

Monocots Eudicots From oldest to furthest divergence: ``` Extinct gymnosperm anscestor Amborella Water lillies Star anise and relatives Magnolias and relatives then Monocots and Eudicots ```

Question 68

What were the two times that the genome greatly increased in the phylogenetic tree of angiosperms?

Answer 68

A whole genome duplication occurred before the divergence of Amborella. The genome size tripled (a whole-genome triplication) during the evolution of eudicots. Plant evolutionary biologists speculate that these duplication and triplication events strongly influenced the diversification of modern angiosperms.

Question 69

What are monocots and euidots named for in differences in the number of embryonic leaves called what?

Answer 69

Cotyledons

Question 70

What are one difference that distinguish monocots from eudicots? Think petals and tepals.

Answer 70

Monocots typically have flowers with parts numbering three or multiples of three (a monocot with six tepals) Eudicots have flower parts that occur in fours, fives, or a multiple of four and five (a eudicot with five petals)

Question 71

What are fused petals that tend to accumulate sugar-rich nectar that provides a reward for pollinators, animals that transfer pollen among plants?

Answer 71

Floral tubes The diameters of floral tubes vary among flowers and are evolutionarily tuned to the feeding structures of diverse animals, which range from the narrow tongues of butterflies to the wider bills of nectar-feeding birds.

Question 72

What is a distinctive feature of the orchid family?

Answer 72

Orchids provide another example ofways in which flower parts have become fused; stamens and carpels are fused together into a single reproductive column that is surrounded by attractive tepals.

Question 73

What advantage does the nonshowy perianth of grass flowers provide?

Answer 73

A large, showy perianth would not be useful to grass plants because they are wind pollinated; such a perianth would interfere with pollination in grasses. By not producing a showy perianth, grasses increase the chances of successful pollination and save resources that would otherwise be consumed during perianth development.

Question 74

What is a tightly clustered group of flowers produced by a plant?

Answer 74

Inflorescence! The sunflower family features a type of inflorescence in which many small flowers are clustered into a head. The flowers at the center of a sunflower head function in reproduction and lack showy petals, but flowers at the rim have showy petals that attract pollinators.

Question 75

What is a structure that develops from flower parts, encloses seeds, and fosters seed dispersal in the environment?

Answer 75

Fruits Seed dispersal helps to prevent seedlings from competing with their larger parents for scarce resources such as water and light.

Question 76

What are a few examples of the diverse mechanisms that flowering plants use to disperse their seeds?

Answer 76

1. Many angiosperm fruits such as cherries, lemons are attractively colored, soft, juicy, and tasty. Animals digest them and elminate the seeds dispering them. 2. Strawberries are aggregate fruits, structures consisting of many fruits that all develop from a single flower having multiple pistils. The ovaries of these pistils develop into tiny, single-seeded yellow fruits on a strawberry surface; the fleshy, red, sweet portion of a strawberry develops from a flower receptacle. Aggregate fruits allow a single animal consumer, such as a bird, to disperse many seeds at the same time. 3. Pineapples are juicy multiple fruits that develop when many ovaries of an inflorescence fuse together. Such multiple fruits attract relatively large animals that have the ability to disperse seeds for long distances. 4. The plant family informally known as legumes is named for itsdistinctive fruits, dry pods that open down both sides when seeds aremature, thereby releasing them 5. Nuts and grains are additional examples of dry fruits. Grains are the characteristic single-seeded fruits of cereal grasses such as rice, corn(maize), barley, and wheat. 6. Coconut fruits are adapted for dispersal in ocean currents and can float for months before being cast ashore 7. Maple trees produce dry and thus lightweight fruits having wings, features that foster effective wind dispersal. 8. Other plants produce dry fruits with surface burrs that attach to animal fur.

Question 77

What involves the synthesis of organic compounds that are not essential for cell structure and growth in organisms but aid their survival and reproduction?

Answer 77

These molecules are called secondary metabolites, which are are produced by various prokaryotes, protists, fungi, some animals, and all plants, but are most diverse in the angiosperms.

Question 78

Of the 100,000 secondary metabolites known, most are produced by?

Answer 78

Flowering plants!

Question 79

What are the three major classes of plant secondary metabolites that occur?

Answer 79

1. terpenes and terpenoids 2. phenolics, which include flavonoids and related compounds 3. alkaloids

Question 80

What is an example of each major class of secondary metabolites that we utilize in modern life?

Answer 80

Natural rubber is an example of a complex terpene. Capsaicin is an example of a phenolic compound. Caffeine is an example of a alkaloid.

Question 81

Information on the three major classes of secondary metabolites! About 25,000 types of plant terpenes and terpenoids are constructed from different arrangements of the simple hydrocarbon gas isoprene. Taxol, whose use in the treatment of cancer was noted earlier, is a terpene, as are citronella and a variety of other compounds that repel insects. Rubber, turpentine, rosin, and amber are complex terpenoids that likewise serve important roles in plant biology as well as having useful human applications. Phenolic compounds are responsible for some flower and fruit colors as well as the distinctive flavors of cinnamon, nutmeg, ginger, cloves, chilies, and vanilla. Phenolics absorb UV radiation, thereby preventing damage to a plant’s DNA. They also help to defend plants against insects and disease microbes. Some phenolic compounds found in tea, red wine, grape juice, and blueberries are antioxidants that detoxify free radicals, thereby preventing cellular damage. Alkaloids are nitrogen-containing secondary metabolites that often have potent effects on the animal nervous system. Plants produce at least 12,000 types of alkaloids, and certain species produce many alkaloids. Caffeine, nicotine, morphine, ephedrine, cocaine, and codeine are examples of alkaloids that influence the physiology and behavior of humans and are thus of societal concern. Like flower and fruit structures, secondary metabolites are useful in distinguishing among Earth’s hundreds of thousands of flowering plant species.

Answer 81

N/A