Chapter 21 Introduction to Plants

21.1 Plant Evolutions and Adaptations

Main idea

!  Adaptations to environmental changes on Earth contributed to the evolution of plants

What evidence is there that present-day plants and present-day green algae have common ancestry?

!  Cell walls composed of cellulose !  Cell division includes formation of cell plate !  Same type of chlorophyll used in

photosynthesis !  Food stored as starch

Plant Adaptations to Land Environments

!  Cuticle – fatty waxy coating on outer surface of cells !  helps prevent the evaporation of water from

plant tissues and as a barrier to microorganisms

Plant Adaptations to Land Environments

!  Stomata – openings in the outer cell layer of leaves and stems !  Allows exchange of gasses betwwn plant

tissues and the environment

Plant Adaptations to Land Environments

!  Vascular Tissue – specilalized transport tissue !  Enables faster movement of substances over

greater distances !  Provides structure and support

!  Vascular plants - plants with vascular tissue !  Nonvascular plants – plants without vascular

tissue

Reproductive Stragegies

!  Water is the limiting factor the environment of these plants !  The sperm and egg cannot unite without a

film of water in which to swim !  Seed – a plant structure that contains an

embryo, nutrients for the embryo, and is covered with a protective coat

Seed p. 607

! 

Nutrients Nutrients

Alteration of Generations

!  Alteration between a haploid gametophyte generation and a diploid sporophyte generation ! Gametophyte produces gametes – sperm

and egg !  Sporophyte produces spores that can grow

to form the next gametophyte generation

Plant Classification p. 608

!  12 plant classifications !  3 nonvascular (liverworts, mosses,

hornworts) !  3 vascular, nonseed (ferns, horsetails,

club mosses) !  5 vascular seed plants (anthophytes,

conifers, gnetophytes, cycads, and ginkgo)

21.2 Nonvascular plants

!  Main idea – Nonvascular plants are small and usually grow in damp environments

!  Must be in the presence of water in order for materials to move within them

Division Bryophyta - mosses

!  No true roots, stems, or leaves

!  Have rootlike rhizoids that anchor the plant to the soil or other surface

!  Example: Sphagmum

Sphagnum moss

Division Athocerophyta - hornworts

!  Smallest division of nonvascular plants !  Large chloroplast in each cell of

gametophyte and sporophyte !  Spaces around cells are filled with mucilage

(slime) for cyanobacteria to grow and live in – example of mutulaism

Hornwort

Division Hepaticophyta - liverworts

!  Classified as thallose or leafy !  Thallose – has a body that resembles a

fleshy, lobed structure !  Leafy appears to have tiny leaves

Liverwort

21.3 Seedless Vascular Plants

!  Seedless vascular plants generally are larger and better adapted to drier environments than nonvascular plants because they have vascular tissue.

Diversity of Seedless Vascular Plants

!  Strobilus – a compact cluster of spore-bearing structures

Division Lycophyta

!  Club mosses !  Dominant sporophyte generation !  Epiphyte – plant tha ilves anchored to an

object or other plant

Club mosses

Division Pterophyta

!  Ferns and horsetails !  Rhizome – a food-storage organ !  Sporangium – where fern spores form !  Sorus – clusters of sporangia

Ferns

Horsetails

21.4 Vascular Seed Plants

Main Idea

!  Vascular seed plants are the most widely distributed plants on Earth

Cotyledons

!  Structures that store food or help absorb food for the tiny plant

Diversity of Seed Plants

!  Seed dispursal methods ! Cocklebur hooks ! Witch hazel ejects ! Coconut floats !  Pine seeds have winglike structures ! Milkweed seeds have parachute structures

Division Cycadophyta

!  Cones – contain male or female reproductive strucrures, these evolved before seeds

!  found in tropics and subtropics, with one

species found in southern Florida

Cycad

Division Gnetophyta

!  Plants in this division can live 1500-2000

Welwitschia

! 

Ginkgophyta

!  Leaves are small and fan shaped

Leaf of Ginko Biloba

Reproductive Structures of Conifers

!  Most develop into cones

Pine or Evergreen Trees

Adaptations seen in conifers

!  Drooping branches – to carry the weight of snowfall

!  Waxlike coating (cutin) covers needlelike leaves to reduce waterloss

Conifer – Bald Cypress

How are flowering plants classified?

!  As monocots or dicots

!  Annual – completes its life span in one growing season

!  Biennual – completes its life span in two growing seasons

!  Perennial – can live for several years and usually produces flowers and seeds yearly

Flowering Plants

End of 21