Download Plant Diversity - Mr. Mathews` Science Spectacular

Plant Diversity
Chapter 22
22-1 Introduction to Plants
Oldest fossil evidence-470 million years
ago
 Plants dominate the landscape
 Provide the base for food chains on land
 Provide shade, shelter and oxygen for
animals of all sizes

What is a Plant?
Members of the Kingdom Plantae.
 Multicellular eukaryotes
 Cell walls of cellulose
 Develop from multicellular embryos
 Carry out photosynthesis using chlorophyll
a and b
 Most are autotrophs, few are parasites or
saprobes (feed on decaying organisms)

How have plants become so successful if
they can’t move to get away from
predators or to get food?
 Think of plants as “Stationary animals that
eat sunlight”

The Plant Life Cycle

Two alternating phases known as the
alternation of generations
Diploid (2N)- the sporophyte plant or spore
producing
 Haploid (N)- the gametophyte plant or gamete
producing
 Phyte-means plant

Generalized Plant Life Cycle
Section 22-1
Haploid
Diploid
MEIOSIS
Spores
(N)
Gametophyte Plant (N)
Sporophyte Plant (2N)
Sperm
(N)
Eggs
(N)
FERTILIZATION
Mosses and Ferns- Require water to
reproduce
 Seed Plants- reproduce without water
 Many plants also have vegetative or
asexual reproduction

What Plants Need to Survive
Developed adaptations to survive as
sessile organisms
 Plants need sunlight, water & minerals,
gas exchange and transportation of water
and minerals through the plant body

Sunlight
Need sunlight to carry out photosynthesis.
 Adaptations to gather sunlight

Leaves broad and flat
 Arrangement on stem to maximize light
absorption

Water and Minerals
Need a constant supply of water
 Need to get water to all cells, above
ground too
 Structures to limit water loss
 Minerals absorbed with the water needed
for plant growth

Gas Exchange
Require oxygen to carry out respiration
and carbon dioxide for photosynthesis
 Can’t lose water vapor in the process

Movement of Water and Nutrients
Specialized tissues that carry water up
from the soil and distribute food through
the plants
 Simple plants do this by diffusion

Early Plants
Most of Earth’s history-no plants
 Algae and photosynthetic prokaryotes
provided the planets oxygen and food
 Plants appeared, life on Earth changed
 New ecosystems, soil formed, organisms
developed
 How did plants adapt to land, how did they
evolve structures to allow life on land?

Origins in the Water
First plants evolved from an organism
much like the green algae today
 Algae have size, color and appearance of
plants
 Similar reproductive cycles
 Cell walls and photosynthetic pigments
like plants

The First Plants
DNA sequencing confirms that plants are
closely related to certain groups of green
algae.
 Oldest known fossils of plants, 450 million
years ago-similar to today’s mosses
(cooksonia)
 Suggest that they were still dependent on
water to complete life cycle.


From plant pioneers two lineages
Mosses and their relatives
 All other plants on Earth today


Evolved different adaptations to living on
dry land.
Flowering
plants
Cone-bearing
plants
Ferns and
their relatives
Flowers; Seeds
Enclosed in Fruit
Mosses and
their relatives
Seeds
Water-Conducting
(Vascular) Tissue
Green algae
ancestor
Overview of the Plants Kingdom

Plants divided into four major divisions
based on three features
Water conducting tissues
 Seeds
 Flowers

Mosses, Ferns, Cones, Flowers
 Today classified more precisely by DNA
sequencing

Cone-bearing plants
760 species
Ferns and
their relatives
11,000 species
Mosses and
their relatives
15,600 species
Flowering
plants
235,000 species
22-2 Bryophytes






Nonvascular plants- No vascular tissue to
conduct water and nutrients
Life cycles that depend on water for
reproduction
No vascular tissue so they draw up water by
osmosis only a few cm’s above ground
This keeps them very small
Produce sperm that swim to reach eggs
Have to live where rain or dew for part of yr.
Groups of Bryophytes
Most recognizable feature is that they are
low growing plants in moist shaded areas
 Plants thrive in areas where water is in
regular supply
 Three separate phyla.

Mosses or Bryophyta
 Liverworts or Hepaticophyta
 Hornworts or Anthocerophyta

Mosses
Most common Bryophyte.
 Grow abundantly in areas with water and
nutrient poor soil
 Tolerate low temperatures, most abundant
plants in the polar regions
 Vary in appearance from mini evergreen
trees to filament plants that form carpet of
green

Gametophyte of moss looks like a stem
with tiny leaves-one cell thick so lose
water quickly
 Reproduce with a thin stalk with a capsule
that contains spores-sporophyte
 No true roots-rhizoids anchor to the
ground and absorb water and minerals
 Water moves from cell to cell through
rhizoids to rest of plant

Capsule
Sporophyte
Stalk
Stemlike
structure
Gametophyte
Leaflike
structure
Rhizoid
Liverworts
Flat leaves attached to the ground is what
these plants look like.
 Named because some species look like a
flattened liver
 Leaf forms an umbrella shaped object that
produces the sperm and eggs.
 Some form gemmae that are in cuplike
structures that wash out and produce new
individual

Hornwort
Look very much like the liverwort
 Only difference is that the sporophyte
looks like a tiny green horn
 Most found where soil is moist year round

Life Cycle of Bryophytes
Life cycle involves alternation of
generations
 Gametophyte is dominant, recognized
form and carries out the plants
photosynthesis
 Sporophyte is dependent on the
gametophyte for water and nutrients

Dependence on Water
Sperm must swim to the egg to fertilize
 Bryophytes must live in habitats where
water is available at least part of the year

Life Cycle of Moss




When spore lands in a moist place it germinates
and forms a protonema-mass of tangled green
filaments.
Protonema grows to form rhizoids (rootlike
structures and shoots that grow into the air.
Shoots form the familiar green part of the plants.
The gametophyte
At the tips of the gametophyte are the
archegonia (eggs) or antheridia (sperm).
Life cycle of Moss




Some have both on the same gametophyte
some have separate gametophytes
When sperm and egg fuse and fertilization takes
place the diploid zygote is formed
This zygote develops into the sporophyte part of
the moss. It grows right out of the gametophyte
part of the plant and depends on the
gametophyte for food and water
When sporophyte matures it produces haploid
spores in a capsule by meiosis and the capsule
ruptures and releases the spores into the air and
the cycle continues.
Figure 22–11 The Life Cycle of a Moss
Section 22-2
Haploid (N)
Diploid (2N)
MEIOSIS
Spores
(N)
Protonema
(young gametophyte)
(N)
Male
gametophyte
Female
gametophyte
Mature
sporophyte
(2N)
Capsule
(sporangium)
Gametophyte
(N)
Antheridia
Young
sporophyte
(2N)
Sperm
(N)
Archegonia
Zygote
(2N)
Gametophyte
(N)
Egg
(N)
FERTILIZATION
Go to
Section:
Sperm
(N)
Human Uses of Moss
Sphagnum moss grow in acidic water of
bogs
 The dead sphagnum moss are called peat
and accumulate in thick layers.
 Peat can be harvested and used as fuel or
in gardening to retain moisture near the
plants or to increase the acidity of the soil
near the plants.

22.3 Seedless Vascular Plants
Bryophytes can only move water from cell
to cell by osmosis.
 420 million years ago moss were joined by
plants up to a few meters high
 How did they grow that tall.
 New transport system with vascular tissue.
 Able to get water to a higher height

Evolution of Vascular Tissue: A
Transport System

Tracheids-new type of cell that allows
transport of fluids and nutrients in plants

Makes up xylem-the system of plants that
transports water.
Def.-hollow cells with thick cell walls to
resist pressure
 Connected end to end like straws so that
the water flows through them
 More efficient movement than by diffusion

Evolution-cont.
2nd type of vascular tissue is Phloem
 Used to transport solutions of nutrients
and carbohydrates produced by
photosynthesis
 Both xylem and phloem move nutrients
through the plant even against gravity
 Combination of xylem and lignin enables
plants to grow much higher

Ferns and their Relatives
Include the club moss, horsetails and ferns
 All have true roots, stems and leaves
 Roots-underground organs that absorb
water and nutrients. Xylem in center of
root
 Stems-supporting structure to connect root
with the leaf
 Leaves-Photosynthetic organs of the
plants

Club Mosses-Phylum Lycophyta
Once very large and ancient group of land
plants
 Now much smaller phylum containing club
mosses
 Ancients grew up to 35 meters tall and
made some of the Earth’s first forests that
are now huge beds of coal.
 Look like miniature pine trees so also
called the ground pines.

Horsetails
Only living genus is Equisetum that grows
about 1 meter tall.
 Has true leaves, stems and leaves which
are nonphotosynthetic.
 Leaves are nonphotosynthetic, scalelike
and are arranged in whorls
 Scouring rush looks like a horses tail and
has crystals of silica and used to scour
pots and pans

Ferns





Phylum Pterophyta evolved 350 mya when the
club moss forests covered the Earth.
Ferns survived in greater numbers than any
other spore-bearing vascular plants
Have true vascular tissues, strong roots
creeping stems called rhizomes and large
leaves called fronds
Can thrive in areas of little light and most
abundant in wet or seasonally wet habitats
Often found in forests of larger trees
Life Cycle of Ferns
Large plant that we recognize as the fern
is the diploid sporophyte and is the
dominant state.
 Develop haploid spores in structures
called sporangia in clusters called sori and
are usually on the underside of the fronds
 When spores germinate they develop into
a haploid gametophyte.

Small gametophyte develops rootlike
rhizoids and then flattens into a thin, heart
shaped green structure that is the mature
gametophyte
 Small , tiny and develops independently
from the sporophyte
 Antheridia and archegonia are found on
the underside of the gametophyte. Why??





Fertilization requires at least a thin film of water
so sperm can swim to eggs
The zygote produced immediately develops into
a new sporophyte plant
As the sporophyte develops the gametophyte
withers away.
The sporophytes can live for many years as the
fronds produced in spring die in the fall but the
rhizomes live through the winter and produce
new leaves
Figure 22–17 The Life Cycle of a Fern
Section 22-3
MEIOSIS
Sporangium
(2N)
Haploid gametophyte (N)
Diploid sporophyte (2N)
Frond
Spores
(N)
Mature
sporophyte
(2N)
Developing
sporophyte
(2N)
Antheridium
Young
gametophyte
(N)
Mature
gametophyte
(N)
Sperm
Gametophyte
(N)
Egg
Sporophyte
embryo
(2N)
Go to
Section:
Archegonium
FERTILIZATION
Compare/Contrast Table
Section 22-3
Comparing Spore-Bearing Vascular Plants
Characteristics
Club Mosses
Horsetails
Ferns
Water
transportation
By vascular
tissue
By vascular
tissue
By vascular
tissue
Structure
Look like
miniature pine
trees; scalelike
leaves
True leaves,
stems, and roots
Creeping or
underground
rhizomes (stems);
fronts (leaves);
some have no
roots or leaves
Go to
Section:
22.4 Seed Plants



Whether acorns, pine nuts, dandelion seeds, or
kernels of corn seeds are found everywhere.
Plants with this single trait have evolved to
become the most dominant group of
photosynthetic organisms on land
Two major groups

Gymnosperms-bear seeds on surface of cones
Angiosperms-flowering plants bear seeds inside a
layer of tissue that protects the seed
Reproduction Free From Water

Like all plants-alternation of generations

Gametophyte and sporophyte stage
Difference from moss/ferns in that they
don’t need water for fertilization of
gametes
 Because of this they can live everywhere
 Adaptations that allow this


Flowers or cones, transfer of sperm by
pollination, protection of embryo in seeds
Cones and Flowers

Gametophytes of seed plants grow and
mature in sporophyte structures called
cones or flowers.
Cones are seed bearing structures of
gymnosperms
 Flowers are angiosperms seed bearing
structures

Pollen
The entire male gametophyte is contained
in a tiny structure called a pollen grain.
 Doesn’t travel through water
 Carried to the female reproductive
structure by

Wind
 Insects
 Animals


Transfer of pollen to female is called
pollination
Seeds
Def.-Seed is the embryo of a plant that is
encased in a protective covering and
surrounded by a food supply.
 Embryo-organism in an early stage of
development
 Plant embryo is diploid and is the early
developmental stage of the sporophyte
plant





Seed food supply provides nutrients to the
growing embryo
Seed coat-surrounds and protects the embryo
and keeps it from drying out
Seeds may have specialized structures to help
with dispersal to other habitats
Embryos in seeds can remain dormant for long
periods of time and start growing again only
when the conditions are good for survival
Evolution of Seed Plants
Fossil record shows that ancestors of seed
plants evolved adaptations (seed) in order
to survive in places where moss/ferns
couldn’t
 Fossils show that the first seed plants
existed 360 mya and that they resembled
ferns
 Remains exist as large coal deposits

Gymnosperms-cone bearers
Most ancient surviving seed plants
 Include the Gnetophytes, Cycads,
Ginkgoes and the Conifers
 Seeds are all exposed- naked seeds

Gnetophytes
70 species are known
 Reproductive scales are clustered in
cones
 Welwitschia-representative species

Cycads
Cycadophyta-palmlike plants with large
cones
 1st appeared 225 mya
 9 genera exist
 Found in tropics and subtropics

Ginkgoes
One species left-Ginkgo biloba
 Common during dinosaur reign
 Living fossil-looks just like ancestors
 Tough and resistant to air pollution

Conifers
Over 500 species
 Pines, spruce, firs, cedars, sequoias etc
 Some live long others grow tall

Ecology of Conifers
Thrive in a wide variety of habitats
 Leaves have adaptations to survive dry
conditions

Long thin
 Waxy coating

Most are evergreen-retain leaves
throughout year
 Replaced every 2-14 years

Compare/Contrast Table
Section 22-4
Comparing Features of Seed Plants
Feature
Gymnosperms
Angiosperms
Seeds
Bear their seeds on cones
Bear their seeds within
flowers
Reproduction
Can reproduce without
water; male gametophytes
are contained in pollen
grains; fertilization occurs
by pollination
Can reproduce without
water; male gametophytes
are contained in pollen
grains; fertilization occurs
by pollination
Examples
Conifers, cycads, ginkgoes,
gnetophytes
Grasses, flowering trees
and shrubs, wildflowers,
cultivated flowers
Go to
Section:
22.5 Angiosperms—Flowering
Plants
Members of the Phylum Anthophyta
 Appeared 135 mya, most recent of plants
 Originated on land and dominate the plant
life on Earth
 Most have reproductive method involving
flowers and fruit

Flowers and Fruit
Angiosperms develop unique reproductive
organs known as flowers
 Flowers are an advantage because they
attract animals which then transport pollen
from flower to flower.
 Much more efficient than wind pollination
of the gymnosperms
 Flowers contain ovaries that surround and
protect the seeds.

After pollination the ovary develops into a
fruit which protects the seed and aids in
dispersal
 Fruit-a wall of tissue surrounding the seed

Another adaptation that led to success of
angiosperms
 Spreads plants over large areas of land

Diversity of Angiosperms

Very diverse group with many ways to
classify them
Monocots vs. Dicots
 Woody vs. Herbaceous
 Annual vs. Perennial vs. Biennial

Categories can overlap
 Just provides a way to organize them

Monocots and Dicots

Two classes in the angiosperms
Monocotyledonae-single seed leaf or
cotyledons
 Dicotyledonae-two seed leaves

Cotyledon is the first leaf or first pair of
leaves that are produced by the embryo.
 See chart in next slide for different
characteristics of Monocots vs. dicots

Figure 22–25 Comparison of
Monocots and Dicots
Section 22-5
Monocots
Go to
Section:
Dicots
Seeds
Single
cotyledon
Two
cotyledons
Leaves
Parallel
veins
Branched
veins
Flowers
Floral parts
often in
multiples of 3
Floral parts often
in multiples
of 4 or 5
Stems
Vascular
bundles
scattered
throughout stem
Vascular
bundles
arranged in
a ring
Roots
Fibrous roots
Taproot
Woody and Herbaceous Plants
Characteristics of the stems of these
plants puts them into these two categories
 Woody-have cells with thick cell walls to
support the plant



Ex. Trees, shrubs, vines
Herbaceous-stems are smooth and
nonwoody.

Produce no wood as they grow
Annuals, Biennials & Perennials
Categories based on life spans
 Annuals-complete a life cycle in one
growing season


Many garden plants
Biennials-Complete a life cycle in two
years
 Perennials-plants that live for more than
two years


Some herbaceous, most are woody