Question 1

What is a flower?

Accepted Answer

Branches specialized for reproduction found in some seed-bearing plants, containing either specialized male or female organs or both male and female organs.

Question 2

What is fruit?

Accepted Answer

Thickened tissue derived from ovary wall that protects the embryo after fertilization and facilitates seed dispersal.

Question 3

What is an ovule?

Accepted Answer

A female gametophyte.

Question 4

What is a pollen grain?

Accepted Answer

A structure containing the male gametophyte of the plant.

Question 5

What is a pollen tube?

Accepted Answer

An extension from the pollen grain that delivers sperm to the egg cell.

Question 6

What is a progymnosperm?

Accepted Answer

A transitional group of plants that resembled conifers because they produced wood, yet still reproduced like ferns.

Question 7

What is a seed?

Accepted Answer

A structure containing the embryo, storage tissue and protective coat.

Question 8

What is a spermatophyte?

Accepted Answer

A seed plant; from the Greek sperm (seed) and phyte (plant).

Question 9

What are some examples of the uses of seed plants?

Accepted Answer

For millennia, human societies have depended on seed plants for nutrition and medicinal compounds: and more recently, for industrial by-products, such as timber and paper, dyes, and textiles. Palms provide materials including rattans, oils, and dates. Wheat is grown to feed both human and animal populations. The fruit of the cotton boll flower is harvested as a boll, with its fibers transformed into clothing or pulp for paper. The opium poppy is valued both as an ornamental flower and as a source of potent opiate compounds.

Question 10

What are the sizes of the sporophytes and gametophytes in seed plants?

Accepted Answer

In seed plants, the evolutionary trend led to a dominant sporophyte generation, and at the same time, a systematic reduction in the size of the gametophyte: from a conspicuous structure to a microscopic cluster of cells enclosed in the tissues of the sporophyte.

Question 11

Are seed plants homosporous or heterosporous?

Accepted Answer

Whereas lower vascular plants, such as club mosses and ferns, are mostly homosporous, all spermatophytes are heterosporous.

Question 12

What are the two types of spores produced by seed plants?

Accepted Answer

Spermatophytes produce two types of spores: megaspores (female) and microspores (male). Megaspores develop into female gametophytes that produce eggs, and microspores mature into male gametophytes that generate sperm.

Question 13

Are the gametophytes of seed plants free-living?

Accepted Answer

Because the gametophytes mature within the spores, they are not free-living, as are the gametophytes of seedless vascular plants.

Question 14

What are the evolutionary forerunners of seed plants?

Accepted Answer

Heterosporous seedless plants are seen as the evolutionary forerunners of seed plants.

Question 15

Which adaptations distinguish seed plants from other vascular plants?

Accepted Answer

Seeds and pollen - two critical adaptations to drought, and to reproduction that doesn't require water - distinguish seed plants from seedless vascular plants. Both adaptations were required for the colonization of land begun by the bryophytes and their ancestors.

Question 16

When did gymnosperms evolve?

Accepted Answer

The first reliable record of gymnosperms dates their appearance to the Pennsylvanian period, about 319 million years ago.

Question 17

What was the evolutionary success of gymnosperms versus angiosperms?

Accepted Answer

Gymnosperms dominated the landscape in the early (Triassic) and middle (Jurassic) Mesozoic era. Angiosperms surpassed gymnosperms by the middle of the Cretaceous (about 100 million years ago) in the late Mesozoic era, and today are the most abundant plant group in most terrestrial biomes.

Question 18

What are the names of the eons and when did they occur?

Accepted Answer

Phanerozoic, from 541 million years ago to present Proterozoic, from 2.5 billion years ago to 541 million years ago Archean, from 3.8 to 2.5 billion years ago Pre-Archean, from the formation of the Earth to 3.8 billion years ago

Question 19

What are the names of the eras of the Phanerozoic eon and when did they occur?

Accepted Answer

Cenozoic, from 66 million years ago to present Mesozoic, from 252 million years ago to 66 million years ago Paleozoic, from 541 million years ago to 252 million years ago

Question 20

What are the names of the periods of the Cenozoic era and when did they occur?

Accepted Answer

Quaternary, from 2.6 million years ago to present Tertiary, from 66 million years ago to 2.6 million years ago

Question 21

What are the names of the periods of the Mesozoic era and when did they occur?

Accepted Answer

Cretaceous, from 145 mya to 66 mya Jurassic, from 201 mya to 145 mya Triassic, from 252 mya to 201 mya

Question 22

What are the names of the periods of the Paleozoic era and when did they occur?

Accepted Answer

Permian, from 298 to 252 mya Pennsylvanian, from 323 to 298 mya Mississippian, from 358 to 323 mya Devonian, from 419 to 358 mya Silurian, from 443 to 419 mya Ordovician, from 485 to 443 mya Cambrian, from 542 to 485 mya

Question 23

How do seeds facilitate reproduction in seed plants?

Accepted Answer

The small haploid cells are encased in a protective coat that prevent desiccation and mechanical damage. Pollen grains can travel far from their original sporophyte, spreading the plant's genes. The seed offers the embryo protection, nourishment, and a mechanism to maintain dormancy for tens or even thousands of years, ensuring germination can occur when growth conditions are optimal. Seeds therefore allow plants to disperse the next generation through both space and time.

Question 24

What is the earliest seed plant discovered?

Accepted Answer

The fossil plant Elkinsia polymorpha , a “seed fern” from the Devonian period - about 400 million years ago - is considered the earliest seed plant known to date.

Question 25

What are some characteristics of the first true seed plants and when did they appear?

Accepted Answer

Seed ferns produced their seeds along their branches without specialized structures. What makes them the first true seed plants is that they developed structures called cupules to enclose and protect the ovule - the female gametophyte and associated tissues - which develops into a seed upon fertilization. Seed plants resembling modern tree ferns became more numerous and diverse in the coal swamps of the Carboniferous period.

Question 26

When did progymnosperms appear?

Accepted Answer

Fossil records indicate that the first gymnosperms (progymnosperms) most likely originated in the Paleozoic era, during the middle Devonian period, about 380-390 million years ago.

Question 27

Why were seed plants successful during the Permian period?

Accepted Answer

Following the wet Mississippian and Pennsylvanian periods, which were dominated by giant fern trees, the Permian period was dry. This gave a reproductive edge to seed plants, which are better adapted to survive dry spells.

Question 28

What were the first gymnosperms to appear during the lower Jurassic?

Accepted Answer

The Ginkgoales, a group of gymnosperms with only one surviving species – the Ginkgo biloba .

Question 29

When did gymnosperms reach their evolutionary peak?

Accepted Answer

Gymnosperms expanded in the Mesozoic era (about 240 million years ago), supplanting ferns in the landscape, and reaching their greatest diversity during this time. The Jurassic period was as much the age of the cycads (palm-tree-like gymnosperms) as the age of the dinosaur. Ginkgoales and conifers also dotted the landscape.

Question 30

What ecosystems do gymnosperms dominate nowadays?

Accepted Answer

Although angiosperms are the major form of plant life in most biomes, gymnosperms still dominate some ecosystems, such as the taiga (boreal forests) and the alpine forests at higher mountain elevations because of their adaptation to cold and dry growth conditions.

Question 31

How are seeds an evolutionary adaptation to dry land?

Accepted Answer

Unlike bryophyte and fern spores (which are haploid cells dependent on moisture for rapid development of gametophytes), seeds contain a diploid embryo that will germinate into a sporophyte. Storage tissue to sustain growth and a protective coat give seeds their superior evolutionary advantage. Several layers of hardened tissue prevent desiccation, and free reproduction from the need for a constant supply of water. Furthermore, seeds remain in a state of dormancy - induced by desiccation and the hormone abscisic acid - until conditions for growth become favorable. Whether blown by the wind, floating on water, or carried away by animals, seeds are scattered in an expanding geographic range, thus avoiding competition with the parent plant.

Question 32

How do pollen grains facilitate sexual reproduction?

Accepted Answer

Pollen grains are male gametophytes and are carried by wind, water, or a pollinator. The whole structure is protected from desiccation and can reach the female organs without dependence on water. Male gametes reach the female gametophyte and the egg cell gamete through a pollen tube: an extension of a cell within the pollen grain.

Question 33

Do the male gametes of gymnosperms have flagella?

Accepted Answer

The sperm of most modern gymnosperms lack flagella, but in cycads and the Ginkgo , the sperm still possess flagella that allow them to swim down the pollen tube to the female gamete; however, they are enclosed in a pollen grain.

Question 34

When did angiosperms appear?

Accepted Answer

Undisputed fossil records place the massive appearance and diversification of angiosperms in the middle to late Mesozoic era. Fossil evidence indicates that flowering plants first appeared in the Lower Cretaceous, about 125 million years ago, and were rapidly diversifying by the Middle Cretaceous, about 100 million years ago. Earlier traces of angiosperms are scarce. Fossilized pollen recovered from Jurassic geological material has been attributed to angiosperms. A few early Cretaceous rocks show clear imprints of leaves resembling angiosperm leaves. By the mid-Cretaceous, a staggering number of diverse flowering plants crowd the fossil record. The same geological period is also marked by the appearance of many modern groups of insects, including pollinating insects that played a key role in ecology and the evolution of flowering plants.

Question 35

How did angiosperms evolve?

Accepted Answer

Although several hypotheses have been offered to explain the sudden profusion and variety of flowering plants, none have garnered the consensus of paleobotanists. New data in comparative genomics and paleobotany have, however, shed some light on the evolution of angiosperms. Rather than being derived from gymnosperms, angiosperms form a sister clade that developed in parallel with the gymnosperms. The two innovative structures of flowers and fruit represent an improved reproductive strategy that served to protect the embryo, which increased genetic variability and range. Paleobotanists debate whether angiosperms evolved from small woody bushes, or were basal angiosperms related to tropical grasses. Both views draw support from cladistics studies, and the so-called woody magnoliid hypothesis - which proposes that the early ancestors of angiosperms were shrubs - also offers molecular biological evidence.

Question 36

What is the most primitive living angiosperm?

Accepted Answer

The most primitive living angiosperm is considered to be Amborella trichopoda , a small plant native to the rainforest of New Caledonia, an island in the South Pacific. Analysis of the genome of A. trichopoda has shown that it is related to all existing flowering plants and belongs to the oldest confirmed branch of the angiosperm family tree.

Question 37

Why are basal angiosperms considered primitive?

Accepted Answer

A few angiosperm groups called basal angiosperms are viewed as primitive because they branched off early from the phylogenetic tree. Most modern angiosperms are classified as either monocots or eudicots, based on the structure of their leaves and embryos. Basal angiosperms, such as water lilies, are considered more primitive because they share morphological traits with both monocots and eudicots.

Question 38

Where does fertilization and embryo development occur in angiosperms?

Accepted Answer

Angiosperms produce their gametes in separate organs, which are usually housed in a flower. Both fertilization and embryo development take place inside an anatomical structure that provides a stable system of sexual reproduction largely sheltered from environmental fluctuations.

Question 39

How diverse are flowering plants?

Accepted Answer

Flowering plants are the most diverse phylum on Earth after insects; flowers come in a vast array of sizes, shapes, colors, smells, and arrangements.

Question 40

What is the relationship between flowers and pollinators?

Accepted Answer

Most flowers have a mutualistic pollinator, with the distinctive features of flowers reflecting the nature of the pollination agent. The relationship between pollinator and flower characteristics is a primary example of coevolution.

Question 41

How do seeds and fruits develop?

Accepted Answer

Following fertilization of the egg, the ovule grows into a seed. The surrounding tissues of the ovary thicken, developing into a fruit that will protect the seed and often ensure its dispersal over a wide geographic range. Not all fruits develop from an ovary, however; such structures are “false fruits”.

Question 42

How do fruits serve as agents of dispersal?

Accepted Answer

Some may be carried away by the wind. Many attract animals that will eat the fruit and pass the seeds through their digestive systems, then deposit the seeds in another location. Cockleburs are covered with stiff, hooked spines that can hook into fur (or clothing) and hitch a ride on an animal for long distances.

Question 43

What invention did cockleburs inspire?

Accepted Answer

The cockleburs that clung to the velvet trousers of a Swiss hiker, George de Mestral, inspired his invention of the loop and hook fastener he named Velcro.

Question 44

Which genes are frequently chosen for DNA alignment analysis?

Accepted Answer

The genes encoding the ribosomal RNA from the small 18S subunit and plastid genes are frequently chosen for DNA alignment analysis.

Question 45

What are conifers?

Accepted Answer

The dominant phylum of gymnosperms with the most variety of trees.

Question 46

What is a cycad?

Accepted Answer

A gymnosperm that grows in tropical climates and resembles a palm tree; member of the phylum Cycadophyta.

Question 47

What does it mean to be dioecious?

Accepted Answer

Describes a species in which the male and female reproductive organs are carried on separate specimens. Literally, “two homes” or unisexual.

Question 48

What is a ginkgophyte?

Accepted Answer

A gymnosperm with one extant species, the Ginkgo biloba : a tree with fan-shaped leaves.

Question 49

What is a gnetophyte?

Accepted Answer

A gymnosperm shrub with varied morphological features that produces vessel elements in its woody tissues; the phylum includes the genera Ephedra , Gnetum and Welwitschia .

Question 50

What is a gymnosperm?

Accepted Answer

A seed plant with naked seeds (seeds exposed on modified leaves or in cones).

Question 51

What is an integument?

Accepted Answer

A layer of sporophyte tissue that surrounds the megasporangium, and later, the embryo.

Question 52

What is a megasporocyte?

Accepted Answer

A megaspore mother cell; larger spore that germinates into a female gametophyte in a heterosporous plant.

Question 53

What is a microsporocyte?

Accepted Answer

A smaller spore that produces a male gametophyte in a heterosporous plant.

Question 54

What does it mean to be monoecious?

Accepted Answer

Describes a species in which the male and female reproductive organs are on the same plant. Literally, “one home” or bisexual.

Question 55

What is an ovulate cone?

Accepted Answer

A cone containing two ovules per scale.

Question 56

What is a strobilus?

Accepted Answer

A plant structure with a tight arrangement of sporophylls around a central stalk, as seen in cones or flowers; the male strobilus produces pollen, and the female strobilus produces eggs.

Question 57

What are some characteristics of gymnosperms?

Accepted Answer

Gymnosperms are paraphyletic, and their characteristics include naked seeds, separate female and male gametes, pollination by wind, and tracheids (which transport water and solutes in the vascular system).

Question 58

In what ways are gymnosperm seeds “naked”?

Accepted Answer

Gymnosperm seeds are not enclosed in an ovary; rather, they are exposed on cones or modified leaves.

Question 59

In which types of environments do gymnosperms predominate?

Accepted Answer

They are adapted to live where fresh water is scarce during part of the year, or in the nitrogen-poor soil of a bog. They are still the prominent phylum in the coniferous biome or taiga, where the evergreen conifers have a selective advantage in cold and dry weather. Evergreen conifers continue low levels of photosynthesis during the cold months, and are ready to take advantage of the first sunny days of spring.

Question 60

What is a disadvantage that conifers face?

Accepted Answer

One disadvantage is that conifers are more susceptible than deciduous trees to infestations because conifers do not lose their leaves all at once. They cannot, therefore, shed parasites and restart with a fresh supply of leaves in spring.

Question 61

What are some reproductive characteristics of gymnosperms?

Accepted Answer

The life cycle of a gymnosperm involves alternation of generations, with a dominant sporophyte in which the female gametophyte resides, and reduced gametophytes. All gymnosperms are heterosporous. The male and female reproductive organs can form in cones or strobili. Male and female sporangia are produced either on the same plant (monoecious), or on separate plants (dioecious).

Question 62

What are some reproductive characteristics of pine trees?

Accepted Answer

Pine trees are conifers and carry both male and female sporophylls on the same mature sporophyte. Therefore, they are monoecious plants. Like all gymnosperms, pines are heterosporous and generate two different types of spores: male microspores and female megaspores.

Question 63

How does pollination and fertilization occur in conifers?

Accepted Answer

In the male cones, or staminate cones, the microsporocytes give rise to pollen grains by meiosis. In the spring, large amounts of yellow pollen are released and carried by the wind. Some gametophytes will land on a female cone. Pollination is defined as the initiation of pollen tube growth. The pollen tube develops slowly, and the generative cell in the pollen grain divides into two haploid sperm cells by mitosis. At fertilization, one of the sperm cells will finally unite its haploid nucleus with the haploid nucleus of the egg cell.

Question 64

How does a female gametophyte develop in conifers?

Accepted Answer

Female cones, or ovulate cones, contain two ovules per scale. One megaspore mother cell, or megasporocyte, undergoes meiosis in each ovule. Three of the four cells break down; only a single surviving cell will develop into a female multicellular gametophyte, which encloses archegonia.

26: Seed Plants Flashcards

Evolution of Seed Plants, Gymnosperms, Angiosperms, the Role of Seed Plants

Brainscape's Knowledge GenomeTM

26: Seed Plants Flashcards

Evolution of Seed Plants, Gymnosperms, Angiosperms, the Role of Seed Plants

Brainscape's Knowledge Genome^TM