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

  1. Lycophytes

Club mosses – club shaped spore-bearing cones or strobili

Epiphytes – plants that live on other plants

  1. Horsetails (Sphenophyta)

Thrive in streambank muds, vacant lots, roadsides

Hollow photosynthetic stems

Silica – reinforced ribs structurally support these stems and give them texture

  1. 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

  1. 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

  1. Cycads

Pollen bearing and seed bearing cones form on separate plants

Inhabit tropical and subtropical

  1. 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 PlantKingdom

______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)

  1. Lycophytes

Club mosses –

Epiphytes –

  1. Horsetails (Sphenophyta)

Thrive in

Hollow photosynthetic stems

Silica –

  1. 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 -

  1. 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.

  1. Cycads

______bearing and ______bearing cones form on separate plants

  1. 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 –
  1. dicots –