Plants have 4 main characteristics: photosynthesis, a cuticle layer, cell walls, and a two-stage life cycle of sporophyte and gametophyte stages. Plants can be divided into 4 main groups: nonvascular plants like mosses and liverworts, seedless vascular plants like ferns and club mosses, gymnosperms like conifers, and angiosperms or flowering plants. Scientists believe plants originated from ancient green algae based on their many similarities like chlorophyll, cell walls, photosynthesis, and life cycles.

1. IntroductionIntroduction
to Plantsto Plants

2. PlantPlant
CharacteristicsCharacteristics
 Plants have 4Plants have 4
characteristicscharacteristics
that they all share:that they all share:
 (1) Photosynthesis(1) Photosynthesis
– Plants arePlants are greengreen
because theybecause they
containcontain
chlorophyllchlorophyll
– ChlorophyllChlorophyll: green: green
pigment thatpigment that
captures energycaptures energy
from sunlight,from sunlight,
found infound in
chloroplastschloroplasts

3. – Plants use energyPlants use energy
from sunlight tofrom sunlight to
make food frommake food from
carbon dioxide andcarbon dioxide and
water—this processwater—this process
is known asis known as
photosynthesisphotosynthesis
– Plants arePlants are
producersproducers—they—they
make their own foodmake their own food

4.  (2) Cuticles(2) Cuticles
– Plants don’tPlants don’t dry outdry out
because they arebecause they are
protected by aprotected by a
cuticlecuticle
– CuticleCuticle: a waxy: a waxy
layer that coatslayer that coats
most of themost of the
surfaces of plantssurfaces of plants
that are exposed tothat are exposed to
airair

5.  (3) Cell Walls(3) Cell Walls
– Plants do not have aPlants do not have a
skeletonskeleton like animalslike animals
– They stay upright andThey stay upright and
are protected becauseare protected because
they are surrounded bythey are surrounded by
a rigid cella rigid cell wallwall
– Cell wall is made ofCell wall is made of
carbohydrates andcarbohydrates and
proteinsproteins
– Some plants form aSome plants form a
secondary cell wallsecondary cell wall
this stops them fromthis stops them from
growing largergrowing larger

7.  (4) Reproduction(4) Reproduction
– Plants have 2 stages in their life cycle:Plants have 2 stages in their life cycle:
sporophyte stagesporophyte stage andand gametophyte stagegametophyte stage
– In the sporophyte stageIn the sporophyte stage plant makesplant makes sporesspores
– In suitable environment, spores grow & theseIn suitable environment, spores grow & these
new plants are callednew plants are called gametophytesgametophytes

8. – During gametophyte stage, female gametophytesDuring gametophyte stage, female gametophytes
produceproduce eggseggs and male gametophytes produceand male gametophytes produce
sperm.sperm.
– Sex cells cannotSex cells cannot growgrow directly into new plants—adirectly into new plants—a
sperm must fertilize an eggsperm must fertilize an egg
– The fertilized egg grows into a sporophyte, makesThe fertilized egg grows into a sporophyte, makes
more spores, and the cycle starts againmore spores, and the cycle starts again

9. Check for UnderstandingCheck for Understanding
 What are 4 characteristics that allWhat are 4 characteristics that all
plants share?plants share?
Photosynthesis, cuticle, cell wall, andPhotosynthesis, cuticle, cell wall, and
reproductionreproduction

10. 4 Main Groups of Plants4 Main Groups of Plants
 First theyFirst they can be classified as nonvascular plants andcan be classified as nonvascular plants and
vascularvascular plantsplants
 Vascular plants are further divided intoVascular plants are further divided into 33 groups:groups:
– (1) seedless plants(1) seedless plants
– (2) nonflowering(2) nonflowering seedseed plants (gymnosperms)plants (gymnosperms)
– (3) flowering seed plants ((3) flowering seed plants (angiospermsangiosperms))

11. Seedless PlantsSeedless Plants
***2 groups of plants don’t make seeds***2 groups of plants don’t make seeds::
 (1) Nonvascular Plants(1) Nonvascular Plants
– Three groups of plants that lack specializedThree groups of plants that lack specialized
conductingconducting tissues and true roots,tissues and true roots, stemsstems, and leaves, and leaves
– Depend onDepend on diffusiondiffusion to move materials from one partto move materials from one part
of plant to anotherof plant to another
– Most areMost are smallsmall
– Usually live inUsually live in dampdamp placesplaces
– Don’t have true stems, roots, or leavesDon’t have true stems, roots, or leaves

12. – 3 groups of nonvascular plants are3 groups of nonvascular plants are
liverworts, hornworts, and mossesliverworts, hornworts, and mosses
liverworts hornworts mosses

13. Mosses, Liverworts,Mosses, Liverworts,
and Hornwortsand Hornworts
– Have leafy stalks andHave leafy stalks and
rhizoidsrhizoids
– RhizoidRhizoid: a rootlike: a rootlike
structure in nonvascularstructure in nonvascular
plants that holds theplants that holds the
plants in place and helpsplants in place and helps
plants get water andplants get water and
nutrientsnutrients
– Have 2 stages to theirHave 2 stages to their
life cyclelife cycle

14. – Importance of Nonvascular PlantsImportance of Nonvascular Plants
 Usually the first plants to live in a newUsually the first plants to live in a new
environment, such as newly exposed rockenvironment, such as newly exposed rock
 When they die, they form a thin layer ofWhen they die, they form a thin layer of soilsoil
 Hold soil in place, reducingHold soil in place, reducing erosionerosion
 Some animals eat nonvascular plantsSome animals eat nonvascular plants
 Other animals use them forOther animals use them for nestingnesting materialmaterial
 Peat mosses are important to humansPeat mosses are important to humans
because they can be dried out and burnedbecause they can be dried out and burned
asas fuelfuel

15.  (2) Seedless(2) Seedless
Vascular PlantsVascular Plants
– Ferns, horsetails, andFerns, horsetails, and
club mossesclub mosses areare
usually much smallerusually much smaller
than in the past—somethan in the past—some
ferns grew 8 meters tallferns grew 8 meters tall
in ancient forests!in ancient forests!
– Because they haveBecause they have
vascular tissues, theyvascular tissues, they
are often larger thanare often larger than
nonvascular plantsnonvascular plants

16.  FernsFerns
– Have aHave a rhizomerhizome
an undergroundan underground
stem from whichstem from which
leaves and rootsleaves and roots
growgrow
– Fern leaves areFern leaves are
called “called “frondsfronds””
– -The end of the-The end of the
fronds are calledfronds are called
fiddle headsfiddle heads

17.  Club MossesClub Mosses
– HaveHave vascularvascular tissue, so nottissue, so not
actually a mossactually a moss
 HorsetailsHorsetails
– Stems are hollow andStems are hollow and
containcontain silicasilica—gives them—gives them
gritty texturegritty texture
– Early Americans usedEarly Americans used
horsetails to scrub pots andhorsetails to scrub pots and
panspans

18. – Importance of Seedless Vascular PlantsImportance of Seedless Vascular Plants
 Help form soil & prevent erosionHelp form soil & prevent erosion
 Ferns add to soil depth, helping other plants toFerns add to soil depth, helping other plants to
growgrow
 PopularPopular houseplantshouseplants
 Fiddleheads of ferns and some horsetails can beFiddleheads of ferns and some horsetails can be
eateneaten
 Horsetails are used in some dietaryHorsetails are used in some dietary
supplements, shampoos, and skin-care productssupplements, shampoos, and skin-care products
 Remains of ancient ferns, horsetails, and clubRemains of ancient ferns, horsetails, and club
mosses formmosses form coalcoal, which humans rely on for, which humans rely on for
energyenergy

19. Check for UnderstandingCheck for Understanding
 Name & describe the 4 main groups ofName & describe the 4 main groups of
plantsplants
1)nonvascular: no specialized tissues1)nonvascular: no specialized tissues
2) Seedless vascular: ferns, horsetails,2) Seedless vascular: ferns, horsetails,
club mossesclub mosses
3) Gymnosperms: nonflowering seed3) Gymnosperms: nonflowering seed
4) Angiosperm: flowering seed4) Angiosperm: flowering seed

20.  The Origin of PlantsThe Origin of Plants
– Green algae may look like aGreen algae may look like a plantplant, but it isn’t a, but it isn’t a
plantplant
– Scientists think that green algae and plantsScientists think that green algae and plants
share ashare a common ancestorcommon ancestor because of thebecause of the
following similarities:following similarities:
 Both have the same kind of chlorophyllBoth have the same kind of chlorophyll
 Have similarHave similar cell wallscell walls
 Both use photosynthesis to make ownBoth use photosynthesis to make own foodfood
 Both store energy in form ofBoth store energy in form of starchstarch
 Both have aBoth have a twotwo-stage life cycle-stage life cycle

21. The similarities between a modern green algae
(right) and plants, such as ferns (left), suggest
that both may have originated from an ancient
species of green algae.

22. Check for UnderstandingCheck for Understanding
 Explain the origin of plantsExplain the origin of plants
--scientists think that green algae andscientists think that green algae and
plants share a common ancestorplants share a common ancestor