Transcript Botany Unit Notes

Botany Unit Notes
Part I
What is a Plant?
When you are asked,
“what color is life?”, the
color that comes to
mind is usually green!
 It is no wonder that all
of Earth’s living
systems ultimately
depend upon plants

What is a Plant?

Plants are multicellular eukaryotes
that have cell walls made of cellulose
Many plants undergo photosynthesis
 Plants include: trees, shrubs, and
grasses

 Also
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ferns and mosses
Most are autotrophs except for a few
parasitic plants and saprobes
 Saprobes
feed on decaying organic material
What Plants Need to Survive
Sunlight ~ plants use the
energy from the sun to
carry out photosynthesis
 Water and Minerals ~ all
cells require water and it is
used during photosynthesis
plants absorb minerals
from the soil needed for
plant growth

What Plants Need to Survive
Gas Exchange ~ plants need Carbon
Dioxide and even Oxygen to carry out
photosynthesis
 Movement of Water and Nutrients:
The water and minerals taken up by
the roots of plants needs to be
transported to the structures that
carry out photosynthesis


These are hundreds of feet in the air
sometimes!
The Origin of Plants
It all started in the water
 Some scientists believe
that the first plants came
from ancient,
photosynthetic prokaryotes
 The oldest known fossils of
plants show them to be
around 500 Million years
old

Green Algae
The Origin of Plants
Overview of the Plant Kingdom

Botanists divide the Plant Kingdom into 4
groups based upon three features:
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Water-conducting tissues
Seeds
Flowers
The Four Groups
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Cone bearing ~ 760 species
Ferns & their relatives ~ 11,000 species
Mosses & their relatives ~ 15,600 species
Flowering plants ~ 235,000 species

The most abundant plants of today are the flowering plants
making up 90% of all plants on Earth
Overview of the Plant Kingdom
Evolution of Land Plants

As plants evolved they obtained important
traits:

Non-vascular tissues (primitive)
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Vascular plants (seedless came first)

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Plants that have specialized tissues capable of drawing water
up from the soil through roots (Ferns & horsetails)
Seed producing plants
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Early plants that needed to be near water to diffuse it into
their cells (bryophytes: mosses, liverworts, hornworts)
Plants able to protect their young in a durable seed
(Gymnosperms: Cycads, Gnetophytes, Conifers, etc)
Seeds enclosed in fruits (advanced)

Plants that adapted an attractive fruit to have animals
disperse their young (Angiosperms: Grasses, fruit trees,
shrubs, etc)
Seedless Vascular Plants
The first seedless vascular
plants arrived on land around
420 million years ago
 The new adaptation of
transporting water and
nutrients through the plant
using vascular tissue allowed
them to grow much taller than
the mosses and other
bryophytes

Vascular Tissues
Vascular tissues allowed
plants to grow taller &
transport water and
nutrients
 Xylem moves water up
the plant from the roots
 Phloem transports sugars
and nutrients of
photosynthesis down
through the plant

Seedless Vascular Plants
This group contains the club
mosses, horsetails, and ferns
 What makes them different from
the earlier plants is that they
have true roots, stems, and
leaves

Club Mosses – Phylum
Lycophyta, millions of years ago
they existed as tall plants towering
over 100 ft!
 Today they are small plants living
in moist woodlands

Seedless Vascular Plants
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Horsetail – Phylum Arthrophyta
The only living species left of this
phylum
 All plants in this Phylum belong to
the Genus Equisetum and has true
roots, leaves, and stems
 They reproduce by way of spores
released from specialized structures
 They look like tall grasses and are
found near water most often

 They
are popular pond plants and used
for decoration in Asian gardens
Seedless Vascular Plants

Ferns are members of
the Phylum Pterophyta
Thought to have begun
around 350 mya
 Survivors of millions of
years and having 11,000
different species existing
today
 True vascular tissues,
strong roots, and
underground stems called
rhizomes

Life Cycle of Ferns

Ferns and relatives are
actually the final stage
of their lifecycle
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Called a Diploid
Sporophyte
Spores are haploid
forming young
gametophytes
The gametophytes
produce sperm and
egg and then fertilize
the egg
After fertilization, a
mature sporophyte
grows from the
gametophyte