Chapter 25: Plants
In order to survive the transition from water to land it was necessary for plants to
make adaptations for obtaining water and to prevent its loss. Water was also
required to provide a medium for the fertilization of eggs by flagellated sperm. In
addition, once plants emerged from the protective cover of water, genetic
material was more susceptible to damage by UV radiation. The following list
summarizes the major plant adaptations for survival on land.
Overview of the Plant Kingdom
 295,000 species of photoautotrophs
 a few heterotrophs
 vascular plants – internal tissues conduct water and solutes through roots,
stems and leaves
 bryophytes – nonvascular plants
 Ex. Liverworts, hornworts, and mosses
 Gymnosperms – seed bearing vascular plants
 Angiosperms – seed and flower bearing vascular plants
 2 groups – dicots and monocots
Evolution of Roots, Stems and Leaves
 root system – underground absorptive structures and help anchor plant
 shoot system – aboveground stems and leaves
 lignin – an organic compound in cell walls that inables the stems to support
themselves
 xylem – distributes water and dissolved ions to cells
 phloem – distributes dissolved sugars and other photosynthetic products
 cuticle – a waxy coat to help conserve water
 stomata – tiny openings across the surface of leaves, help control the
absorption of carbon dioxide and restrict evaporation.
From Haploid to Diploid Dominance
 in most plant life cycles, the diploid phase dominates
 sporophyte – multicelled diploid body
 some cells of sporophytes undergo meiosis and give rise to haploid cells
called spores
 spores divide by mitosis and give rise to gametophytes
 the shift to diploid dominance was an adaptation to land habitats
Evolution of Pollen and Seeds
 gymnosperms and angiosperms, one type of spore develops into female
gametophytes where eggs form and become fertilized
 pollen grains – develop into sperm-bearing male gametophytes
 pollen grains hitch rides to reach eggs
The Bryophytes
 Ex. mosses. Liverworts, and hornworts
 nonvascular plants grow in moist habitats
 mosses are sensitive to air pollution
 do not contain xylem and phloem
 peat bogs – accumulative remains of acids from bacterial and fungal
decomposers compressed into mats
 Rhizoids – elongated cells or threadlike structures that attach gametophytes
to the soil and serve as absorptive structures
Existing Seedless Vascular Plants (Tracheophytes)
 Ex. whisk ferns, lycophytes, horsetails and ferns
 have vascular tissues
 live in wet humid places
 water droplets on plants are the only way flagellated sperm can reach eggs
 all produce spores that germinate into small gametophytes
 4 types
1. Whisk Ferns (Psilophyta)
 Not a fern
 Resemble a whisk broom
2. Lycophytes
 Club mosses – club shaped spore-bearing cones or strobili
 Epiphytes – plants that live on other plants
3. Horsetails (Sphenophyta)
 Thrive in streambank muds, vacant lots, roadsides
 Hollow photosynthetic stems
 Silica – reinforced ribs structurally support these stems and give them
texture
4. Ferns (Pterophyta)
 Largest most diverse group of seedless vascular plants
 Sori – clusters of sporangia develop on underside of fern fronds
 Epiphytes – any aerial plant that grows attached to tree trunks or
branches.
Rise of the Seed-Bearing Plants
 Seed-bearing plants produce pollen grains, two types of spores
1. Microsporangia – produces the microspores (male spores)
 Microspores give rise to pollen grains
 Pollen grains are sperm bearing male gametophytes
2. Macrosporangia – produces the macrospores (female spores)
 Megaspores develop inside ovules
 Ovules – female reproductive structures
 Pollination – the arrival of pollen grains on female reproductive structure
Gymnosperms – Plants with “Naked Seeds”
1. Conifers
 Woody trees and shrubs
 Needlelike or scalelike leaves
 Bear seeds exposed on cone scales
 Cones – clusters of modified leaves that surround spore structures
 Ex. Pines, redwoods, firs, spruces, cypress
2. Cycads
 Pollen bearing and seed bearing cones form on separate plants
 Inhabit tropical and subtropical
3. Ginkgos
 Deciduous – shed leaves
 Only surviving species is Ginkgo biloba
A Closer Look at the Conifers
 Scales of pine cones are parts of a mature female cone in which megaspores
formed and developed into female gametophyte
 Species of pines, fertilization occurs months or a year after pollination
 Seed formation begins at the ovule
 An embryo sporophyte starts developing form the fertilized egg
 Outer layers around female gametophyte matures into a hard coat
Angiosperms – The Flowering, Seed-Bearing Plants
 Flowers – specialized reproductive structures
 Pollinators – insects, birds, bats, etc
 Flowering plants coevolved with pollinators
 Two classes of flowering plants
1. monocots – orchids, palms, lilies, and grasses, including rye, sugarcane,
corn, rice, wheat, etc.
2. dicots – cabbages, daisies, most flowering shrubs and trees, oaks, apple,
water lilies, cacti
Chapter 25: Plants
In order to survive the transition from water to land it was necessary for plants to
make adaptations for obtaining water and to prevent its loss. Water was also
required to provide a medium for the fertilization of eggs by flagellated sperm. In
addition, once plants emerged from the protective cover of water, genetic
material was more susceptible to damage by UV radiation. The following list
summarizes the major plant adaptations for survival on land.
Overview of the Plant Kingdom
 ____________ species of photoautotrophs
 A few heterotrophs
 Vascular plants –
 Bryophytes –

 Gymnosperms –
 Angiosperms –
 2 groups –
Evolution of Roots, Stems and Leaves
 Root system –
 Shoot system –
 Lignin –
 Xylem –
 Phloem –
 Cuticle –
 Stomata –
From Haploid to Diploid Dominance
 In most plant life cycles, the diploid phase dominates
 Sporophyte –
 Some cells of sporophytes undergo meiosis and give rise to haploid cells
called spores
 Spores divide by ____________ and give rise to _________________
 The shift to diploid dominance was an adaptation to land habitats
Evolution of Pollen and Seeds
 Gymnosperms and angiosperms, one type of spore develops into female
gametophytes where eggs form and become fertilized
 Pollen grains –

The Bryophytes
 Ex.
 Nonvascular plants grow in moist habitats


 Peat bogs –
 Rhizoids –
Existing Seedless Vascular Plants (Tracheophytes)
 Ex.
 Have _______________ tissues

 Water droplets on plants are the only way flagellated sperm can reach eggs
 All produce spores that germinate into small gametophytes
 4 types
1. Whisk Ferns (Psilophyta)


2. Lycophytes
 Club mosses –
 Epiphytes –
3. Horsetails (Sphenophyta)
 Thrive in
 Hollow photosynthetic stems
 Silica –
4. Ferns (Pterophyta)
 Largest most diverse group of seedless vascular plants
 Sori –
 Epiphytes – any aerial plant that grows attached to tree trunks or
branches.
Rise of the Seed-Bearing Plants
 Seed-bearing plants produce pollen grains, two types of spores
1. Microsporangia –
 Microspores give rise to __________ __________
 Pollen grains 2. Macrosporangia –
 Megaspores develop inside ____________
 Ovules –
 Pollination –
Gymnosperms – Plants with “Naked Seeds”
1. Conifers

 Needlelike or scalelike leaves
 Bear seeds exposed on cone scales
 Cones –
 Ex.
2. Cycads
 __________ bearing and __________ bearing cones form on separate
plants

3. Ginkgos
 Deciduous –
 Only surviving species is __________ __________
A Closer Look at the Conifers
 Scales of pine cones are parts of a mature female cone in which megaspores
formed and developed into female gametophyte
 Species of pines, fertilization occurs months or a year after pollination
 Seed formation begins at the __________
 An embryo, _______________, starts developing form the fertilized egg
 Outer layers around female gametophyte matures into a hard coat
Angiosperms – The Flowering, Seed-Bearing Plants
 Flowers –
 Pollinators –
 Flowering plants coevolved with pollinators
 Two classes of flowering plants
1. monocots –
2. dicots –