Chapter 29 Notes
Plant Diversity I: How
Plants Colonized Land
Concept 29.1
More than 280,000 species of plants
inhabit the earth today
Although some are aquatic, most are
terrestrial: deserts, grasslands, forests
Land plants evolved from certain green
algae called charophyceans
Concept 29.1
There are four main groups of land
plants: bryophytes, pteridophytes,
gymnosperms, and angiosperms
Bryophytes: mosses; distinguished from
algae by advances that allow for life on
land
Concept 29.1
Pteridophytes: ferns; contain vascular
tissue (transport water and food);
“seedless plants”
Gymnosperms: conifers; “naked seed”
(seeds are not enclosed in a special
chamber)
Seed: consists of a plant embryo packaged
with food and a protective coat
Concept 29.1
Angiosperms: flowering plants;
“container seed”; most modern-day
plants
algal ancestors  bryophytes  vascular
plants  the origin of seeds  the
evolution of flowers
Concept 29.1
Concept 29.1
Charophyceans are the green algae most
closely related to land plants
Plasma membranes contain rosette
cellulose-synthesizing complexes
- synthesize the cellulose of cell walls
Same enzymes in peroxisomes that help
minimize the loss of product due to
photorespiration
Concept 29.1
Concept 29.1
Several terrestrial adaptations distinguish
land plants from charophycean algae
- growth in length is from apical
meristems
- multicellular, dependent embryos
- alteration of generations:
gametophyte and sporophyte
Concept 29.1
Concept 29.1
Concept 29.1
Concept 29.2
There are other adaptations that are
common in many land plants
Adaptations for water conservation:
- formation of a cuticle
- stomata contain guard cells
Concept 29.2
Concept 29.2
Adaptations for water transport:
Except for bryophytes, land plants have
true roots, stems, and leaves with
vascular tissue
- xylem: carry water and minerals up
from root
- phloem: distribute sugars and amino
acids throughout the plant
Concept 29.2
Concept 29.2
Land plants evolved from charophycean
algae over 500 mya
- chloroplasts: chlorophyll b and betacarotene
- homologous cell walls
- peroxisomes
Concept 29.2
Alteration of generations in plants may
have adapted by delayed meiosis
Charophycean zygote undergoes meiosis
to produce haploid spores
Plant zygote undergoes mitosis to
produce a multicellular sporophyte to
produce haploid spores by meiosis
Concept 29.2
Adaptations to shallow water preadapted
plants for living on land
- natural selection would favor those
that could withstand occasional drying
Concept 29.3
Bryophytes are represented by 3 phyla:
Hepatophyta (liverwarts),
Anthocerophyta (hornworts), and
bryophyta (mosses)
Concept 29.3
Concept 29.3
The gametophyte is the dominant
generation in the life cycle of
bryophytes
- sporophytes are typically smaller and
present only part of the time
- up to 50 million spores can be
generated in one spore capsule
Concept 29.3
Concept 29.3
Concept 29.3
Concept 29.3
Mosses are able to exist in very harsh
climates
- able to loose most of their body water
without dying, then rehydrate later
Bryophytes were the only plants on earth
for 100 million years
Concept 29.4
Modern vascular plants include ferns
(pteridophytes), gymnosperms, and
flowering plants (angiosperms)
Differ from bryophytes
- contain phloem and xylem
- dominant sporophyte generation
Concept 29.4
2 phyla of seedless vascular plants:
phylum Lycophyta and phylum
Pterophyta (ferns)
Pteridophytes provide clues to the
evolution of roots and leaves
Concept 29.4
Most pteridophytes have true roots with
lignified vascular tissue
Lycophytes have small leaves with only a
single unbranched vein; known as
microphylls
- modern leaves are known as
megaphylls
Concept 29.4
Concept 29.4
A sporophyte-dominant life cycle evolved
in seedless vascular plants
Homosporous plants: produce one type
of spore
Heterosporus plants: produce
megaspores (female) and microspores
(male)
Concept 29.4