The PlantsPlants dominate most of the land on Earth. A small patch of forest contains thousands of trees (Figure 1(a)), while a golf course is covered in millions of individual grass plants (Figure 1(b)). Plants are ubiquitous in cities as well as in rural settings, indoors and outside. Even if you stay inside all day, you will almost certainly use plant prod-ucts and eat a variety of plant foods (Figure 1(c)). Plants are so abundant that we may forget just how important they are.

3.2

Figure 2 These Arctic poppies are found in Arctic and High Arctic climates, including Baffi n Island.

Although we are surrounded and supported by ecosystems dominated by plants, most people know very little about them. But as you are about to learn, with more than 270 000 known species, plants are fascinating and incredibly diverse. Th e largest plants tower more than 100 m into the air, and the smallest are little more than a mil-limetre across. Today’s oldest living tree has a root system that is over 9550 years old! Th is section gives an introduction to the characteristics and diversity of plants as well as an overview of how they adapted to life on land. Th e Plants unit provides a more detailed study of plant anatomy, growth, and function.

Why Plants Are ImportantPlants can survive in many diff erent climatic conditions, from hot and humid tropics to parched deserts and the extreme cold of the High Arctic (Figure 2). Because plants are producers of food, other terrestrial life forms follow wherever plants live. In fact, the rich diversity of terrestrial ecosystems depends heavily on the diversity of plants. Without plants to supply food through photosynthesis, there would be little life on land.

In addition to supporting food webs, plants also provide other organisms with places to live, such as nesting locations for birds and supports for a spider’s web. Humans are particularly dependent on plants for a wide range of valuable substances including medicines, clothing, wood, and paper products.

Unfortunately, many of the world’s plants are threatened with extirpation or extinction. Habitat destruction, invasive species, pollution, and climate change all pose serious threats to plants and the organisms that depend on them. Today, 77 of Ontario’s native plant species are listed as “species at risk.” Of these, three species are extirpated—no longer living anywhere in the province.

Classifi cation and PhylogenyPlants are thought to have evolved from charophytes, a group of green algae (which belong to the kingdom Protista), between 425 million and 490 million years ago. Th ere is very strong evidence supporting this evolutionary relationship. Plants and green algae both contain chlorophyll a and chlorophyll b, two forms of the green pigment used in photosynthesis. Th ey also contain pigments that are not found in other photosynthetic eukaryotes. Plants and green algae share several other characteristics. At the end of mitosis, only the cells of plants and green algae begin cytokinesis by building a cell plate across the middle of the cell. Th eir cell walls contain large amounts of cellulose, a com-plex sugar molecule. Plants and green algae also store excess food as starch.

charophyte the common name for organisms in the order Charophyceae; green algae in the kingdom Protista

“phyte”?Many plant terms end with the suffi x –phyte. Phyte is derived from the ancient Greek word phut (ón) meaning “plant.”

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Figure 1 (a) From forests to (b) golf courses, much of Earth’s surface is covered by plants. (c) Plants and plant products are all around us, in the products we use and the foods we eat.

(a) (b) (c)

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Today there are more than 270 000 living species of plants. Th ese are classifi ed into four major groups. Th e phylogenetic tree in Figure 3 shows the evolutionary relation-ships between the major groups of plants.

Millions of Years Ago

CronozoicMesozoicPaleozoic

200 0100300400500

nonvascular plants,bryophytes

green algae

seedlessvascular plants,pteridophytes

early vascular plants

first seed plants

diversification of flowering plants

gymnosperms

angiosperms

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Figure 3 A simplifi ed phylogenetic tree of the Plant Kingdom. Many biologists now include green algae within the Plant kingdom and refer to the other groups as the “higher plants.”

CharacteristicsAll higher plants are multicellular eukaryotic organisms. Unlike animals and fungi, almost all plants perform photosynthesis. All have cell walls composed primarily of cellulose. Like fungi, all terrestrial plants are sessile—they cannot move from place to place. Although all plants share these basic features, plants show an incredible diver-sity of characteristics (Figure 4).

Figure 4 (a) In tropical rainforests, a great variety of plant species cover every square metre of available space, including the branches of trees. (b) Sundews are carnivorous plants native to Ontario bogs. Their leaf hairs secrete a sweet, sticky liquid that attracts and traps insect prey. These hairs and the leaf blade then slowly curl inward on the prey.

(a) (b)

Alternation of GenerationsPlants have a very diff erent life cycle than that of animals. Th is life cycle is known as an “alternation of generations.” Th is life cycle has diploid and haploid states, or generations. Th e diploid generation produces spores, and the haploid generation produces gametes.

BotanistBotanists specialize in the study of plants. To learn more about botanists,

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Typical animal body cells are diploid (2n), containing two sets of chromosomes. Th ese cells undergo meiosis, producing haploid sex cells, or gametes. Two haploid (n) cells fuse in the process of fertilization, forming a diploid zygote that then grows into the adult animal (Figure 5(a)).

A plant in the diploid stage is called a sporophyte (Figure 5(b)). As in animals, the sporophyte’s diploid cells divide by meiosis to produce haploid cells. In plants, however, these haploid cells form asexual spores. As the haploid generation begins, the spores grow into gametophyte individuals. Th e gametophytes mature, then pro-duce haploid sex cells—gametes. Th ese gametes undergo fertilization to form diploid zygotes. Th e zygotes grow into sporophyte individuals, and the cycle continues.

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adult(multicellular)

(2n )

Animal Life Cycle

diploid(2n )

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Plant Life Cycle

haploid(n )

fertilization meiosis

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haploid) sex cells (n )

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Figure 5 (a) A typical animal life cycle consists only of diploid individuals that produce haploid sex cells. (b) Plant life cycles alternate between a diploid sporophyte generation and a haploid gametophyte generation.

Climate has a dramatic infl uence on the distribution and success of plant communities. Each plant species is ideally suited for a particular range of temperatures, water availability, and seasons. The greenhouse gases that humans release into the atmospherearecontributingtoclimatechange.Themainhuman-generated greenhouse gas is carbon dioxide—a key reactant in photosynthesis. In this activity you will research some of the ways in which the changing climate and increasing levels of atmospheric carbon dioxide are likely to affect plant distribution and diversity.

1. Use print and online resources to research the following topics: (i) How might an earlier spring and later fall infl uence plants? (ii) Explain how climate change is causing Ontario’s plant

communities to move northward.

(iii) What effects could a changing climate have on plant pests and disease? On forest fi res?

(iv) How are increasing concentrations of carbon dioxide in the atmosphere likely to infl uence plants?

A. Based on your research, how will climate change and increasing levels of carbon dioxide in the atmosphere likely affect plant distribution? T/I

B. How will climate change and the resulting changes in plant distribution affect biodiversity? Consider the effects on the biodiversity of plants as well as the ecosystems and food webs they support. T/I A

Climate Change and Plant Communities

Research This

Skills: Researching, Analyzing, Evaluating, Communicating SKILLSHANDBOOK A2.1, A5.1

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Early Adaptations for Life on LandMost plant species living today live on the land. Th ere are some aquatic species, but most are freshwater—only a few are marine. Th e primitive ancestors of today’s plants, however, lived in the water. Th ey were probably very much like green

Unit tasK BOOKMARK

Compare and contrast the life cycles of the organisms in your chosen group. Do the conservation efforts aimed at this group need to take into account any features of this life cycle?

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algae—relatively small, photosynthetic, multicellular organisms. Th ese early plants, like green algae living today, would have reproduced sexually using eggs and sperm that swam through the water.

When plants fi rst began to live on land, they developed characteristics that allowed them to live and reproduce in that new environment. Although life on land gave plants lots of light and carbon dioxide—both essential for photosynthesis—it forced plants to adapt in other ways.

Th e fi rst requirement for life on land was the ability to prevent water loss. When exposed to dry air and warm temperatures, unprotected living cells quickly lose water through osmosis and evaporation. Plants developed a fl exible, waxy cuticle on their outer surfaces that eff ectively prevents water loss (Figure 6(a)).

Although preventing water loss is critical for land plants, they must be able to take in small amounts of carbon dioxide gas from the atmosphere in order to perform photosynthesis. To meet this need, plants developed stomata (singular: stoma), tiny openings between specialized cells on the plant’s surface (Figure 6(b)). Th ese stomata are like windows that can be opened and closed. When they are open, gases can dif-fuse into and out of the plant. When they are closed, the plant is eff ectively sealed off from the surrounding air.

cuticle a waterproof, waxy coating produced by the epidermis of most plants

stoma a small opening in the epidermis of a plant that allows gas exchange

Bryophytes: The MossesTh e bryophytes are the simplest of land plants. Th is group includes the mosses, liver-worts, and hornworts. Th e most recognizable of these are the mosses—there are more than 1000 species of moss in North America alone! Th e peat mosses, of the genus Sphagnum, may be the most numerous plants on Earth. In many ecosystems, including Canada’s boreal forest, Sphagnum mosses can form a continuous ground cover over hundreds and thousands of square kilometres (Figure 7).

Like the earliest of land plants, bryophytes have a protective cuticle and stomata for gas exchange. Th ey do not have specialized vascular tissue or true leaves, roots, or seeds. Most bryophytes are only a few centimetres in height.

Th e gametophyte generations of bryophytes produce swimming sperm in struc-tures called antheridia (singular: antheridium) and eggs (in structures called archegonia (singular: archegonium). Bryophytes can therefore only live and reproduce in places with at least occasional wet conditions, such as rains or heavy dew.

Th e green plants we recognize as mosses are the photosynthetic gametophyte indi-viduals. Aft er fertilization, the new, non-photosynthetic sporophyte individuals grow out of the archegonia on the female gametophyte and get their nourishment from the gametophyte. Th ese sporophytes seem to be part of the gametophyte but are actually the off spring of the gametophyte plants. Th e sporophytes grow a tall stalk that bears a structure called a sporangium (plural: sporangia), in which haploid spores are produced. Th ese tiny spores are easily carried by winds and dispersed over a large area.

bryophyte a small seedless plant that lacks vascular tissue

Figure 7 Various species of sphagnum moss form a thick covering in this bog.

sporangium the structure in which spores are produced

Figure 6 (a) Almost all plant surfaces produce a waterproof, waxy cuticle. (b) Stomata are small openings in the epidermis that allow gas exchange with the air. Most leaves have thousands of stomata per square centimetre.

cuticle epidermal cell

epidermis stoma

epidermal cell

epidermal cell

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antheridium the specialized structure on a gametophyte that produces sperm

archegonium the specialized structure on a gametophyte that produces eggs

(b)

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Figure 8 illustrates the alternation of generations life cycle of a typical moss. Some moss gametophytes can also reproduce asexually. Small clumps of photosynthetic haploid cells called gemmae (singular: gemma) are produced in cup-shaped structures on the surface of the gametophytes. Th e gemmae are dispersed by splashes of rain and grow into new gametophyes.

gemma a small clump of haploid photosyntheticcellsproducedinlittlecup-shaped structures on the gametophyte plant; dispersed by splashes of rain to grow into another gametophyte plant

Lycophytes and Pterophytes: The FernsTh e next major adaptation by land plants was the development of vascular tissue. Vascular tissue consists of xylem and phloem. It is specialized for the transportation of water and nutrients. Plants with vascular tissue can grow to great heights, thereby accessing more sunlight. Lignin is a key chemical component of vascular tissue. It is an extremely strong compound that makes cell walls more rigid. It is responsible for the great strength of woody tissues.

Th e lycophytes (club mosses) and pterophytes (ferns and their relatives) are groups of seedless vascular plants that still have many characteristics of the earliest vascular plants. During the Carboniferous period, about 360 million to 300 million years ago, these plants dominated the landscape. Some grew as large as 2 m in diameter and more than 40 m in height! Today’s 13 000 or so species remain widespread and common, but most are relatively small.

Among the simplest of vascular plants are members of the genus Equisetum called horsetails. Th ey are considered “living fossils” because they are the only remaining genus of what was once a very diverse group of plants. As they grow, silica crystals form on their stems.

Figure 8 The life cycle of a moss. In order to fertilize the eggs, sperm must swim through water on the surface of the gametophytes.

diploid

haploid

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archegonia witheggs (n )

stalk (2n )

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plant(n )

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lignin an important structural compound found in the vascular tissues of plants; it is responsible for the strength of wood

lycophyte a seedless vascular plant; club mosses are examples of lycophytes

pterophyte a seedless vascular plant; ferns are examples of pterophytes

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Similar to bryophytes, the gametophyte individuals of lycophytes and pterophytes reproduce sexually using sperm and eggs. Unlike the bryophytes, however, the sporo-phytes are photosynthetic and much larger than the gametophytes (Figure 9). Both groups have simple roots and stems. Th e stems of ferns are usually in the form of rhizomes that grow horizontally just below the surface of the ground. Ferns also have large green leaves called fronds.

Figure 9 Life cycle of a fern. Note that the sporophyte is photosynthetic and much larger than the gametophyte. The gametophyte (less than 1 cm across) is greatly enlarged in this diagram.

In addition to simple roots, many lycophytes and pterophytes have also developed symbiotic mycorrhizal relationships that help them obtain water and other nutrients from the soil. In fact, the gametophytes of lycophytes are non-photosynthetic and live hidden underground, where they get nutrients directly from symbiotic fungi.

Gymnosperms and Angiosperms: The Seed PlantsToday almost all lycophytes and pterophytes grow in the shadows of seed plants. In most of these plants, the entire male gametophyte is carried from one plant to an-other by the wind or by animals, instead of travelling through water. Seed plants are therefore not restricted to reproduction over short distances in wet conditions, and they have become the dominant land plants on Earth.

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young sporophyteplant (2n ) growingout of gametophyteplant

mature sporophyteplant (2n )(a) frond(b) rhizome(c) roots

sporangium onunderside of frond (a)

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HaploidGametophyteGeneration

rhizome a horizontal underground stem

frond a fern leaf; young curled fronds are often called “fi ddleheads” because of their distinctive shape; some fi ddleheads are edible, but many are toxic

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Pollen grains are waterproof capsules that contain microscopic haploid male gameto-phytes (Figure 10(a)). Pollination occurs when the male gamete in a pollen grain penetrates an ovule containing a female gametophyte. Th e male gamete fertilizes the egg, producing a diploid zygote. Th is diploid zygote, or embryo, becomes a seed.

Seeds contain a food supply for the embryo inside a seed coat (Figure 10(b)). Th ey vary dramatically in size from the gigantic seeds of the Coco de Mar, or sea coconut, with a mass of more than 17 kg, to the microscopic seeds of certain orchids, with a mass of less than 0.001 g! Seeds can remain dormant, allowing the embryo to survive for extended periods of time until conditions are suitable for it to germinate.

pollen small structures called “grains” that contain a microscopic haploid male gametophyte

ovule a small structure that contains a microscopic haploid female gametophyte

seed a plant structure containing an embryo and a food supply, surrounded by a protective outer covering called the seed coat

gymnosperm a vascular plant that produces seeds in special structures called cones; gymnosperms are a major plant group

cone in plants, the reproductive structure of a conifer; produce either pollen or ovules

Figure 10 (a) Pollen grains are microscopic and have variable shapes and surface features. (b)Seedscontainayoungsporophyteembryo,anutrient-richtissue,andanouterprotectivecoating.

(a)

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seed coat

embryosporophyte

nutritivetissue

(b)

Th e food supply within the seed provides the young plant embryo with the nutrients it needs to grow a small root, a stem, and leaves before it is able to rely on photosynthesis. Th is food supply is a concentrated mix of starch, plant oils, and some protein. It is therefore a very important food source for many animals—including humans. More than 70 % of all human food supplies are derived from the seeds of just three plants: wheat, rice, and corn.

You will study the life cycles, structure, and functions of seed plants in much greater detail in the Plants unit. What follows now is an introduction to the most important members of the Plant kingdom.

Gymnosperms: The ConifersGymnosperms include the coniferous trees such as pines, spruce, cedars, and junipers, and other less well known groups of plants including the cycads and ginkgoes.

Cones are the reproductive structures of conifers. Male cones produce and release pollen, and female cones produce eggs. When an egg is successfully pollinated and fertilized within a female cone, an embryo develops within a seed in the cone.

Th ere are about 800 species of modern gymnosperms. Many of these are woody trees, and most have needle- or scale-like leaves. Th ese narrow leaves and their thick cuticles are adaptations that help the trees reduce water loss. Gymnosperms have large, shallow root systems that form a mycorrhizal relationship with symbiotic fungi (Figure 11). Many gymnosperms are well adapted to resist hot dry summers and cold winters.

Gymnosperms are very valuable. Th ey provide about 85 % of all wood used in construction and furniture manufacturing and are also the source of almost all pulp and paper.

Some gymnosperms are gigantic. Th e largest single conifer on Earth is in California. Th is giant sequoia named “General Sherman” is 83 m tall and has a cir-cumference at its base of 33 m. Its estimated mass of 1400 tonnes is equivalent to the mass of about 10 000 average-sized adult humans! Th is single tree contains enough lumber to build more than 100 average-sized homes.

Figure 11 Thiscross-sectionshowsthemycelium of the fungus extending far beyond the root system of the seedling.

b. Mycorrhiza

a. Lodgepole pine

Small,youngtree root

Hyphalstrands

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Th e boreal forests of northern Ontario are dominated by spruce trees and are a major source of lumber and pulp and paper. Th ey also support many large ecosys-tems—they are home to many species of wildlife. Some gymnosperms can live for hundreds of years and are the foundation of well-established and complex ecosystems. For example, the Th ree Sisters (Figure 12) live in Carmanah Walbran Provincial Park in Vancouver, British Columbia. Th ey are three Sitka spruces that share a root system. Th ese 80 m tall trees are part of an ecosystem that is hundreds of years old!

Th reats to the boreal forest, including from climate change and harvesting prac-tices, have raised some serious concerns about future sustainability. In May 2007 more than 1500 scientists from around the world endorsed a document called the Canadian Boreal Forest Conservation Framework. Continued eff orts have since led to a truly remarkable agreement between the Forest Products Association of Canada and nine leading environmental organizations. In May 2010 these organizations signed what is considered the largest forest conservation plan in history. Th e plan calls for strict envi-ronmental safeguards for 700 000 km2 of boreal forest, including 300 000 km2 where cutting will be halted to protect threatened woodland caribou.

Figure 12 The Three Sisters

Biodiversity is seriously at risk in most parts of the world, including Canada. Close to one-third of all vascular plants are threatened with extinction within 30 years unless action is taken soon to protect them. Canada is home to more than 3000 species of native vascular plants. About 1000 of these have been classifi ed as rare by the Canadian Museum of Nature. Scientists, government and non-profi t agencies and institutions, and members of the public are all involved in taking action to conserve biodiversity in their region and elsewhere. In this activity you will research a specifi c conservation initiative aimed at protecting a particular plant or plant community.

1. Research several public and private conservation agencies and organizations involved in plant conservation. Consider international and regional environmental organizations and botanical gardens. Choose one program or initiative that you believe is important.

2. Investigate the program in detail and report back on the following aspects of the program:(a) What plant or plant community is the program designed

to protect? Why was this particular plant or plant community considered in need of protection?

(b) What are the benefi ts of protecting this plant or plant community?

(c) What are the specifi c goals of the program? How are they being put into action?

(d) Who funds or fi nancially supports the program?

A. Do you believe the program is worthwhile? Is it likely to be successful in the long term? Why or why not? T/I

B. Write a 30-s radio ad that describes and promotes the program. Share your ad with the class. C

Plant Conservation Initiatives

Research This

Skills: Researching, Analyzing, Evaluating, Communicating SKILLSHANDBOOK A2.1, A5.1

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Angiosperms: The Flowering PlantsMore than 90 % of all modern plant species are angiosperms, or fl owering plants. Th e more than 260 000 species of angiosperms dominate the modern world of plants. With the exception of coniferous trees, mosses, and ferns, virtually all familiar trees, shrubs, and herbaceous plants are angiosperms.

As their common name suggests, angiosperms have specialized reproductive structures called fl owers. Flowers perform the same function as cones in producing both pollen and eggs. However, in female fl ower parts, the eggs are protected in an enclosed ovary. Aft er fertilization, seeds form within the ovary and the outer tissues of the ovary become a fruit. Th e main function of the fruit is to help disperse the seeds. Th e development of fl owers and fruits is key to the success of the angiosperms.

Th ere are two types of seeds in angiosperms. Each seed contains either one (“mono”) or two (“di”) cotyledons. Cotyledons are structures that store food used by the growing embryo during germination.

angiosperm a plant that produces fl owers; angiosperms form the largest group of living plants

fl ower the specialized reproductive structure of an angiosperm; produces pollen and/or ovules

fruit mature ovary of an angiosperm, which contains the seed(s)

cotyledon a structure in the seeds of fl owering plants that stores nutrients

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Th e two largest groups of fl owering plants are the monocots and the eudicots. Th e monocots, comprising some 60 000 species, include more than 10 000 species of grasses and 20 000 species of orchids. Th e eudicots, with more than 200 000 spe-cies, account for most of the rest. Almost all fl owering trees are eudicots. Th ere are a number of smaller groups that do not belong to either the eudicots or monocots. Th ese plants, which include magnolias, cinnamon, black pepper, and water lilies (Figure 13), also have seeds with two cotyledons.

Flowers are extremely diverse (Figure 14(a) to (d)). Th ese structures are special-ized for the way the plant is pollinated. Many fl owering plants are wind pollinated. Th e fl owers on such plants are typically small and drab looking. Examples include the fl owers of grasses. Other fl owers are pollinated by animals such as bees, bats, and humming-birds. Th ese are oft en colourful and fragrant and produce nectar. Th ese special features attract and reward pollinating animals. By carrying pollen from one plant to another, animal pollinators enable plants of the same species to engage in sexual reproduction.

Fruits are equally diverse (Figure 14(e) to (h)). Each fruit is adapted to protect and disperse the seeds within it. Dispersal methods include using wind, water, and other organisms. Th ese adaptations help ensure that the plant reproduces successfully.

Figure 13 Water lilies belong to a small group of fl owering plants called Nymphaeales.

(a) (c)(b) (d)

(e) (g)(f) (h)

Figure 14 Flowersandfruitsreflectthegreatdiversityofthefloweringplants.(a)Irises,(b)forget-me-nots,(c)yellowlady’s-slippers,and(d)leatherleafsareallpollinatedbyanimals.(e)Somefruitsstick to animals, such as burdock, (f) some are eaten by animals, such as these twisted stalk berries, (g) some fl oat in the air, such as this goat’s beard, and (h) some fl oat in the water, like these coconuts.

Plants are a large and diverse group of organisms. In this investigation you will examine two or more plant specimens and note their key distinguishing features. You will classify each into one of the major groups of plants described in this section and make labelled biological drawings of the plants.

Equipment and Materials: hand lens or dissecting microscope; 2 or more plant samples

1. Carefully examine each plant, noting any distinguishing features. Consider whether you are examining a gametophyte or sporophyte specimen.

2. Use the features you observed to classify each plant into one of the major plant groups.

Observing Plant Diversity

Mini Investigation

Skills: Performing, Observing, Analyzing, Communicating SKILLSHANDBOOK

A1.2, A2.1, A3

3. Make labelled biological drawings of each plant.

A. How did you determine whether your specimens were gametophytes or sporophytes? T/I

B. To what major plant groups do your specimens belong? What features did you use to classify your specimens? T/I C

C. Which key adaptations do these plants have for life on land? T/I

D. Use the Internet to fi nd out more about your plant specimens. What type of environment do they live in? T/I

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3.2 Summary

• Plantsarelarge,multicellulareukaryotesthatevolvedfromagroupofgreenalgae more than 400 million years ago.

• Asproducers,plantssupportvirtuallyallterrestrialfoodwebs.• Plantlifecyclesalternatebetweenhaploidanddiploidgenerations.• Bryophytesaresimpleplantswithawaxycuticleandstomatatoreducewater

loss and allow gas exchange.• Fernsareseedlessvascularplantswithlargeleavesandsimpleroots.• Gymnospermsareseedplantsthatreproducewithspecializedconesthat

produce pollen grains and ovules.• Angiospermsarethemostdiversegroupofplantsandreproduceusingflowers.

Angiosperms produce seeds within a specialized structure called a fruit.• Floweringplantsprovidemostofthefoodconsumedbyhumansandour

domesticated animals. The three most important food crops are wheat, rice, and corn. All are monocot grasses.

• Plantsarethreatenedbyanumberofhumanactions,andbyclimatechange.

Conquering the LandWhen plants colonized land more than 400 million years ago, it was one of the most dramatic events in the history of life on Earth. It created a diversity of living habi-tats and food sources for countless terrestrial animals, including you. Unfortunately this diversity is threatened by human actions. The most widespread threat is cli-mate change, which has the potential to affect plants living everywhere on Earth. Overharvesting plants threatens many species, including Ontario’s goldenseal, wild ginseng, and prickly pear cactus. Some plants are also particularly sensitive to various forms of pollution. For example, ground-level ozone—a major pollutant of urban environments—interferes with photosynthesis in some plant species.

3.2 Questions

1. Review the evidence that links plants to charophytes. K/U

(a) List features shared by plants and charophytes that are not shared with most other eukaryotes.

(b) Based on your understanding of endosymbiosis and the evolution of eukaryotes, would you expect any photosynthetic bacteria to share the same pigments as charophytes and plants?

2. Explain how each of the following adaptations dramatically enhanced the success of land plants: K/U C

(a) vascular tissue (d) seeds(b) animal pollination (e) fruit(c) pollen grains (f) mycorrhiza

3. Make a table with check marks to indicate which of the adaptations from Question 2 occurs in the following groups of plants. List the adaptations down the side and the plant groups across the top. K/U C

(a) mosses (c) conifers(b) ferns (d) flowering plants

4. Consider the sporophytes and gametophytes of mosses and ferns: K/U C

(a) In which group(s) does the sporophyte become independent and photosynthetic?

(b) Which forms require liquid water in order to reproduce?(c) Which are able to spread farther, their spores or their

gametes? Explain.

5. Why are seeds a particularly valuable source of food for humans and other animals? K/U

6. Many colourful flowers reward animal pollinators with a supply of sweet nectar. This encourages animals to visit the flowers and, in so doing, carry pollen from one flower to another. Many fruits, containing the seeds of the plant, are also colourful and sweet. Brainstorm the possible benefit(s) to the plant when animals feed on these fruits. A

7. A group of 34 regions on Earth, referred to as biodiversity hotspots, contain more than half of all plant species but cover only 2.3 % of Earth’s land area. Use the Internet and other resources to find out more about these special places. Choose one hotspot and find out where it is located and what types of plants and animals live there. Report your findings to the class. T/I C

go to nelson science

Unit tasK BOOKMARK

As you work on the Unit Task, consider threats to plants and other organisms that support your chosen group. Are any conservation efforts being taken to conserve the ecosystems the group is part of?

3.2 The Plants 95nel

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