Download Plant Kingdom cont.

Plant Kingdom cont.
WHAT'S A PLANT

Plants are members of the kingdom plantae. Plants are
photosynthetic multicellular eukaryotes - or PHOTOAUTOTROPHS.
What about the venus flytrap?

Cell walls are made of CELLULOSE - the material that bacteria and
protists in our small intestine digest for us. Cellulose is a kind of
complex sugar or polysaccharide.

Although cellulose plays an important role in structural support in the
cell walls of plants, cellulose is found in other forms - such as cotton.

The green of plants comes from their photosynthetic pigments
(chlorophyll a & b)
LIFE CYCLE OF PLANTS

The life cycle of plants has two different phases. This is called;
ALTERNATION OF GENERATIONS. In this alternation of
generations, the plant takes turns undergoing mitosis and meiosis to
produce haploid (n) and diploid (2n) gametes.

The diploid (2n) phase is called the sporophyte - or spore
producing plant. The haploid (n) phase is called the gametophyte or gamete producing plant.

The spores are haploid (n) and produced thru meiosis in the
sporophyte plant - each spore can grow into a new plant; the
gametophyte!

A gamete is a reproductive cell produced by mitosis and fuses
during fertilization with another gamete to produce a new individual the diploid sporophyte.
Alternation of Generation
WHAT A PLANT NEEDS
 SUNLIGHT
 WATER
 GAS
& MINERALS
EXCHANGE
 MOVEMENT
OF WATER & NUTRIENTS
HISTORY

Plants didn't exist for most of the Earth's history. Life was mainly
found in the oceans, lakes and streams.

Only after photosynthetic prokaryotes (cyanobacteria) and algae put
oxygen in the atmosphere, did the conditions on Earth become
favorable for other forms of life to evolve and therefore,
to move onto land.

The first plants are thought to have evolved from plantlike-protist,
the green algae. "From these pioneers, several major groups of
plants evolved." (Miller, 555)

1. Mosses and their relatives
2. The other lineage gave rise to all the other plants found today.


Botanists divide plants into four major groups depending on three
main characteristics: water-conducting tissue, seeds, & flowers.
Plant cladogram
BRYOPHYTES

"In the cool forests of the northern woods, the
moist ground is carpeted with green. When you
walk, this soft carpet feels spongy. Look closely
and you will see the structure of this carpet mosses.

Mosses and their relatives are generally called
bryophytes, or nonvascular plants. Unlike all
other plants, these organisms do not have
vascular tissues, or specialized tissues that
conduct water and nutrients." (Levine, 556)

Groups of bryophytes: mosses, liverworts, and
hornworts
Mosses (bryophytes)
Bryophytes
SEEDLESS VASCULAR PLANTS


Ferns, club mosses, and horsetails
Because bryophytes can only transport water from cell to
cell, their height and overall size were limited to a few
centimeters. Around 420 m.y.a., something remarkable
happened. The little mosses were joined by plants that
were up to a meter tall.

The first vascular plants had a new type of cell that was
specialized to conduct water. TRACHEIDS. This was a
revolutionary adaptation in the plant kingdom.

These cells are key in xylem - a water transport system
that carries water up the plant from the root. And
phloem - which transports solutions of nutrients and
carbohydrates produced by photosynthesis.
Club mosses (bryophytes)
FERNS
SEED PLANTS: Gymnosperms (cones) &
Angiosperms (flowering plants)

"Whether they are acorns, pine nuts, dandelion seeds, or kernels of
corn, seeds can be found everywhere. Seeds are so common that
their importance may be overlooked. Over millions of years, plants
with a single trait - the ability to form seeds - became the most
dominant group of photosynthetic organisms on land." (Levine, 564)

REPRODUCTION FREE FROM WATER

Like all plants, seed plants have an alteration of generation life
cycle. Unlike mosses and ferns, seed plants do not need water for
fertilization of gametes.

Adaptations that allow plants to reproduce without water are flowers
and cones.

Pollen: male gametophyte / Seed: embryo of a living plant that is
encased in a protective covering and surrounded by food.
GYMNOSPERMS - CONE BEARERS
 These
are the most ancient surviving seed
plant. This group includes the
gnetophytes, cycads, ginkgoes, and
conifers.
 These
plants all reproduce with seeds that
are exposed - gymnosperm means naked
seed.
Gnetophytes: about 70 present day
species exist.
Gnetophytes
Cycads
 Cycads:
beautiful palm-like plant that
reproduce with large cones. Huge forests
of cycads thrived when dinosaurs roamed
Earth. Today only nine genera exist.
Cycads
Ginkgoes
 These
plants were common when the
dinosaurs existed, but today there is only
one species left. Carefully cultivated in
China.
Gynkgo (living fossil)
Conifers
 Conifers:
more than 500 known
species. This group includes the pines,
spruces, firs, cedars, sequoias, redwoods,
junipers, and yews. Some conifers like the
bristlecone, can live for up to 4000
years. Other species like the giant
redwoods, can grow to more than 100
meters in height. Most conifers are
evergreens - that is, they retain their
leaves throughout the year.
Coniferous forest
ANGIOSPERMS - FLOWERING PLANTS

"...First appeared about 135 m.y.a... Angiosperms
develop unique reproductive organs known as
flowers. In general, flowers are an evolutionary
advantage to plants because they attract animals such
as bees, moths, or hummingbirds, which then transport
pollen from flower to flower. This is much more efficient
than the wind pollination of gymnosperms." (Levine, 569)

Flowers contain ovaries which surround and protect the
seeds. The presence of an ovary gives angiosperms
their name which mean enclosed seed.

The unique angiosperm fruit - a wall of tissue
surrounding the seed - is another reason for the success
of these plants. Why?
Diversity of plants today
DIVERSITY: MONOCOTS & DICOTS (number of
seed leaves - cotyledons - in plant embryo)
A
cotyledon is the first leaf or the first pair
of leaves produced by the embryo of a
seed plant.
 There are other differences. What are
they?
 WOODY
vs. HERBACEOUS
 ANNUALS
(completion of one life cycle in
one season) ~ wheat
 BIENNIALS
(completion of one life cycle in
two seasons) ~ parsley & celery
 PERENIALS
(live for more than two years)
~ asparagus, grasses, palms, maple trees.
 The
End