Plant diversity

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Plant E l ti
Pl t Evolution & Diversity
Di
it

AP Biology Rapid Learning Series
Wayne Huang, PhD
Andrew Graham, PhD
Elizabeth James, PhD
Casandra Rauser, PhD
Jessica Habashi, PhD
Sara Olson, PhD
Jessica Barnes, PhD

© Rapid Learning Inc. All rights reserved. :: http://www.RapidLearningCenter.com

www.RapidLearningCenter.com/
© Rapid Learning Inc. All rights reserved.

1


Learning Objectives
By completing this tutorial, you will learn about:
Ordovician Period
488 Million Year Ago

Plant Evolution
Plant Diversity
Plant Classification
Plant Adaptations

Oldest Land Plant Fossils

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Concept Map: Evolution and Diversity
Evolution

Origin of plants from algae
-500 x 106 years

300,000 types of plants
Evolved from algae

Photosynthetic Eukaryotes
Land Adaptation

Roots, cuticle
stomata etc

Cell type
Land plants

Multicellular
Cell wall of cellulose
chlorophyll

Divided into 10 phyla

Embryophytes

Tracheids Vs Non Tracheids

Definition

Bryophytes

Tracheids

Protect embryo
Seedless

No real
roots

Seed bearing

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2


Plant Evolution
Introduction
Evolution
Fossil Records
Ancestral Origin
Invasion of Land
Adaptation to Land
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Plant Introduction and Overview
Plants are
photosynthetic
multicellular
eukaryotes.

Embryophytes are a group of
plants made up of bryophytes
and vascular plants: trees,
flowers,
flowers ferns mosses and other
green land plants.

Embrophytes
produce an
embryo that is
protected by
tissues of the
parent plant.

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3


Evolution of Plants
Fossil evidence indicates plants are derived
from green algae between 400-500 million
years ago when some algae moved on land.

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cyanobacteria aka
blue-green algae
3 Billion years ago

Age of Plants
350 MYA
Vascular
plants
appeared

300 MYA
Forests
appeared
d

.
Mosses

Ferns
500 MYA
Land plants
from green
algae 500
million years
ago.

Cycads
360 MYA
Origin of the
seed

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150 MYA
Angiosperms
Flowering plants

MYA=Million Years Ago

4


Fossil Records of Plants
This is the fossil records of some protists and plant groups.
The width of the shaded area is an indicator of the number
of species.
Algae is the oldest and angiosperm is the most recent.

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Ancestral Origin of Plants
From a single
ancestral organism
t oug t
thought to be algae,
a gae,
a host of land plants
evolved with even
greater complexity.

Ancestral
organism

Stramenopiles

Red algae

“Brown Plants”

“Red Plants”

Chlorophytes

Charophytes

“Green
Plants”

Embryophytes
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5


Invasion of the Land
Embryophytes
invaded land about
500 million years ago.
What were some of
challenges they had
to overcome?

Water not as
readily available
and rapidly lost
from plant in the
terrestrial
environment.

Dispersal of
gametes is
much more
difficult outside
of an aquatic
environment.

Gravity
prevented
vertical growth.
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Difficulties on the Land
Desiccation

Temperature regulation

Gas exchange

Support

Other problems
plants faced
when they
invaded the
land included:

Reproduction

Dispersal

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6


Adaptation From Water to Land
Plants adapted by becoming
multicellular on land and
developing a thicker cell wall to
prevent drying.

They also developed a
transport system for
nutrients and
minerals, as well as
root, stems, leaves
and seeds

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Plant Diversity
Embryophytes
Plant Species
Plant Kingdom
Plant Life Cycle

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7


Embryophytes: Role of Tracheids

The first plants on earth
p
lacked vascular tissue or like
some mosses, had very
simple conducting tissue that
developed from dead cells.

Tracheids are specialized cells for
conducting water. When plants
moved onto the land, some of them
developed these cells and are
called tracheophytes. Those that
didn’t are called nontracheophytes.

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Diversity of Embryophytes

Embryophytes 10 Phyla

Tracheophytes
7 Phyla

Non-Tracheophytes
3 Ph l
Phyla

Have well developed
vascular systems

Lack tracheids
Members: mosses,
hornworts and liverworts

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8


From Green Algae to Plants
Ancestral
alga

Chlorophytes

Charophytes
Hornworts

Liverworts

Mosses

Club
mosses
Gymnosperm

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Fern

Angiosperm

Reproduction of Embryophytes
Reproduction Evolution For Land Plants
Gametes must be
dispersed in a non
aquatic environment.

Plants adapted by producing
gametes within gametangia
and the egg gets fertilized
within the female organ.

The zygote develops into an
embryo that was retained within
the protective cells of the
female s gametangia.
female’s gametangia

Embryos must be protected
from desiccation.

This adaptation results in
plants being referred as
embryophytes.

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9


Species of Plants
More than 300,000 plants are estimated to
exist. Many thousands remain unknown.
Angiosperms

Gymnosperms
y
p

300,000

1000

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Plant Kingdom: Characteristics
More than 300,000
species exist

Often have plastids in
cytoplasm

Cell wall is
made of
cellulose

Store reserve
food as starch

.

Generate energy
y photosynthesis
y
by p

Contain chlorophyll
and beta carotene
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Usually live on land, but
some live on water

Contains multicellular phototrophs


10


Unique Characteristics of Plants
Meiosis produces
spores that develop
into multicellular
haploid individuals

Most plants
reproduce sexually
and are capable of
asexual propagation
l
ti

Alternation of
generations is a
universal feature
of the life cycles of
plants.

Gametes are
produced by mitosis

Life cycle includes both
multicellular diploid and
multicellular haploid
individuals

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Plant Life Cycle
The 2N sporophyte undergoes meiosis
making a 1n reproductive cell called a spore.
The spore undergoes mitosis to produce a
gametophyte.

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The gametophyte
makes a haploid
gamete that fuses
to form a diploid
zygote sporophyte
sporophyte.

Alternation between haploid
(gametophyte) and diploid (sporophyte)
generations is a distinctive feature of
plants.


11


Alternation of Generations
Multicellular Gametophyte

Spore

Gametes
Haploid (n)

Meiosis

Fertilization

Diploid (2n)
Zygote

Multicellular
sporophyte
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Plant Classification
Introduction
Bryophytes
Tracheophytes
Gymnosperms
Angiosperms
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12


Plant Classification Introduction
There are two major plant divisions depending on if the plant
is a non-vascular (Bryophyte) or a vascular plant.
Notice the types and similarities between the groups.

Vascular
plants

Nonvascular
plants

Mosses
Hornworts

Gymnosperm
Club
mosses

Algae

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Liverworts

Angiosperm

Fern

Bryophytes : Introduction
Require a constantly moist environment
Evolved 500 million years ago

No roots but root like
structures known as rhizoids
Liverworts

Hornworts
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Earliest land plants

Mosses


13


Bryophytes Division Members

Hornworts
(Anthocerophyta)

Liverworts
(Hepatophyta)

Mosses (Bryophyta)

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Bryophytes: Features
Have leaf like structures
that catch and hold water
that splashes onto them.
Many grow in dense
masses through
which water can
move by capillary
action.

Small enough that minerals
can be distributed evenly by
diffusion.

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14


Basic Characteristics of Bryophytes
1. Maternal tissues prevent loss of water
from the embryo
2. Grow in all 6 continents and on the
coast of Antarctica.
3. Grow in dense moist habitats and are
usually small.
4. Have a thin cuticle that is not very
effective in retarding water loss.

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Liverworts

Absorb water via filaments
located on the lower
surfaces of gametophytes.

Most ancient surviving plants
Asexual
A
l
reproduction is by
simple
fragmentation of the
gametophyte.

Several genera have
both sexual and asexual
reproduction
p

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15


Hornworts

The hornworts, phylum
mosses and tracheophytes,
all have special adaptations
for life on land.

These plants have (pores)
stomata that allow the uptake
of CO2 and the release of O2,
but these pores can be closed
to prevent excessive water
loss.

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Non-Tracheophytes
Spores germinate
and give rise to a
multicellular, haploid
gametophyte whose
cells contain
chloroplasts.

Non
tracheophytes
Visible green
structure is the
gametophyte.

Sporophyte produces
S
h t
d
unicellular, haploid
spores through meiosis
within sporangium or
capsules.

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16


Reproduction in Bryophytes
The zygote develops into a
sporophyte which produces 1N
spores in the sporangia which
germinate into another gametophyte.

The male antheridium produces
sperm.
Water is required for the sperm
to swim to the archegonium.

Female gametangia
are called
archegonium and
produces eggs.
The haploid
gametophyte makes
haploid gametes.
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Tracheophytes: Introduction
Sporophyte generation of a
now extinct organism
produced a new cell type
called Tracheid
Tracheid.

Tracheid is the
principal water
conducting element in
the xylem of all
y
tracheophytes except
the angiosperms.

Early vascular plants
had no roots, leaves,
fruits or flowers.

Tracheids

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17


History of Tracheophytes
First tracheophytes

Phylum Rhyniophyta

Had the basic structures observed in all other tracheophyte phyla
Devonian Period
Silurian Period

Club mosses (Lycophyta)
Ferns,
Ferns horsetails and whisk
ferns (Pteridophyta)
Lycophyta and Pteridophyta have true
roots, true leaves, and a
differentiation between two types of
spores.
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Development of Tracheids
Evolution of tracheids had two
important applications.
First it allowed for a pathway to
transport food and minerals.
Second it provided rigid structural
support for vertical growth.

Tracheophytes have a
branching independent
sporophyte.
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18


Evolution of Today’s Plants
Branching
independent
sporophyte

Multiflagellate
sperm, complex
leaves

Club mosses

Horsetails

Whisk fern

Fern

Seeds

Angiosperms

Conifers

Cycads

Flowers

Ginkgos

Gnetophytes

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Reproduction - Gametophytes
Ferns and their
allies have a
heteromorphic
alternation of
generations.

The mature fern is
diploid 2N sporophyte.

The diploid zygote
then grows out of
the prothallus as
the sporophyte.

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The prothallus carries out sexual
reproduction making a 2N zygote.


The plant creates
1N spores by
meiosis dispersed
by the wind.

The spore
germinates and
grows into a
haploid prothallus.

19


Characteristics of Tracheophytes
Roots have their
origins as branches,
either as rhizomes or
above ground portion
of stems.

Early roots were simple
structures that penetrated
the soil, branching and
anchoring the plant.

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Plant Divisions

Vascular Plants

Tracheophytes

Includes seedless plants
Seed bearing forms
Specialized transport cells

Xylem
Phloem
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Transport water and minerals
Transports sugars

These plants are more complex and organized


20


Formation of Leaf Gaps
Most plants above the
fern have
magaphyllous leaves.

The term leaf gap
denotes a gap in the
vascular cylinder above
the leaf insertion.

The petiole is
the leaf stem
and stipules
are the small
processes at
the base of the
petiole.

Vegetative
Stem:
N=node,
I=internode,
B=branch in
whorl, L=fused
megaphylls

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Seedless Tracheophytes
Examples of seedless tracheophytes.

Club moss

Ground pines

Horse tails

Ferns- Most common
vascular plants

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21


Horsetails
Only living genus is
equisetum

Live in damp locations
and have flagellated
sperm

Most are
homosporous

Some have
photosynthetic
gametophytes

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Ferns
Look on the under side of a fern
and you will see their many
sporangia.
Most common
seedless plant

Water is
necessary for
fertilization

Leaves have a
branched vein
system

Sporophylls
bear sporangia
on their
underside

Gametophyte
is fragile &
requires a
moist habitat

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22


Seed Bearing Tracheophytes
Seed Bearing Plants
Successful due to

Efficient vascular system
Extensive root
system

Phloem
Xylem

Two types of seed bearing tracheophytes

Naked seed plants
such as Conifers

Gymnosperms

Angiosperms

Flowering plants

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Gymnosperms

.

Gymnosperms contain
cycads and conifer. The
seeds are naked and not
enclosed in a pericarp as in
angiosperms.

Pine cones

Tracheids transport water and
sieve cells carry organic
materials.

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23


Angiosperms
Angiosperms or flowering plants may be either monocots or dicots.

Monocots have
parallel veined leaves
and floral parts in 3’s.

Dicots have net-veined
leaves and floral parts
in 4’s and 5’s.

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Plant Adaptations
Leaves and Stems
Growth
Seed Production
Pollen
Special Adaptation of Flowering Plants
Senescence and Death
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24


Adaptation of Leaves and Stems
Leaves and stems adapted to
absorb light and CO2. They are
protected by a waxy covering to
prevent loss of water.
water

Have stomata to regulate water
loss, and chlorophyll to absorb
light.

Leaves have a rigid
structure to prevent
wilting.

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Plant Adaptability in Growth
Lignin is a chemical
compound derived
from wood and is an
integral part of the cell
walls of plants
plants.

One possible
form of lignin.

Lignin provides skeletal
support,
support maintains plant
rigidity and reinforces
cellulose.
Lignin is important in plant
evolution because it enables
plants to grow vertically.
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25


Seed Production
Seed production is important
because seeds can survive
for many years and in harsh
conditions.

So why is seed
development so critical to
plant evolution?

It is a good method
to disperse the
plants into new
habitats and avoid
inbreeding.

Also the seeds protect the
plant from pathogens and
competition.

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Role of Pollen
Male Gametophyte

It can be blown/travel great distances by
wind/insects.

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26


Adaptations of Angiosperms
Flowering plants have special
adaptation to help them survive. For
instance they are designed to attract
pollinators.
pollinators

Also they have developed a coevolution with insects that
help them to survive, such
p
,
as pollinators.
Their fruits and seeds are
designed to aid in their
dispersal.

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Flower Specialization
Flowers became specialized
to help them survive and
evolve. Some of their
adaptations included color,
nectar and odor.

Adaptations of growth
characteristics include:
radial or symmetrical,
complete or incomplete.

Characteristics of flower
shape included single
versus composite and
perfect versus imperfect.
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27


Senescence and Death

Perennials live two
years or more.

Annual plants live one
season and die.

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Question: Review
What kingdom do plants
belong to?

Plantae
___________

Fossil evidence indicates
plants evolved from ______.

Of the two major plant
divisions the Bryophyte is __.

Non-vascular
___________

Green plant having a vascular
p
g
system: ferns, gymnosperms,
angiosperms.

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___________
Green algae

Tracheophyte
T
h
h t
___________

A chemical compound
derived from wood and a
important component of plant
cell walls.

Lignin
___________


28


Learning Summary
Embryophytes
are the plants
that produce an
embryo that is
protected by the
parent plant.

Plants are the
multicellular
photosynthetic
organisms
evolved from
green algae.

Plants reproduce
sexually and
have ability of
asexual
propagation.

Non vascular
plants are the
most primitive.
Vascular plants
allow transport
of water and
minerals.

Plants d t d t
Pl t adapted to
land by having
cuticle, stomata,
gametangia,
pigments and
spores.

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Congratulations
You have successfully completed the
core tutorial
Plant Evolution and Diversity


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29


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