2. Think. Pair. Share.
Try thinking of some reasons that plants are so important. (Hints below)
They...
1) Are the source of
all of our food.
2) Produce O2 3) Are sources of medicines
and materials.
4) Are habitats for
many species.
5) Filter/store
water.
6) Are carbon sinks, helping
to control climate change.
3. Plants Plants Plants
One of the first
medicines known to
humans was the bark of
the willow tree, which
was known to relieve
pain when chewed.
We now know it contains
salicylic acid, which is
almost the exact same
drug found in today's
Aspirin and acne creams.
A willow tree, genus Salix
4. Plants, Plants, Plants
Plants are producers
(autotrophs) – this means
they get their energy
from the sun.
Carnivorous plants
typically grow in nutrient-
poor soil. They rely on
bugs as their main source
of nitrogen.
Since they still
photosynthesize for
energy, they are
producers.
A sundew
plant, Drosera
A pitcher plant
5. Plants Plants Plants
The typical plant is multicellular, sessile, sexual, and
autotrophic, with a cellulose cell wall. There are some exceptions.
6. Green Algae
Green algae are the simplest plants. Some may be unicellular and have
flagella for motility. The are believe to be the first plants on Earth.
They are aquatic.
7. Plant Reproduction
Plants reproduce similarly to fungi; they have a life cycle that goes
through an "alternation of generations".
Alternation of Generations – The organism is sometimes haploid (n)
and sometimes diploid (2n).
(Sporophyte)
8. Plant Reproduction
The stage of a plants lifecycle is named based on whether it is in the
haploid stage or the diploid stage:
Sporophyte – a plant in its diploid stage
Gametophyte – a plant in its haploid stage
10. Plant Reproduction
A gametophyte
creates sex cells
(sperm and
eggs, called
gametes).
When two sex cells
fertilize each
other, they become
a single zygote
which grows into a
sporophyte.
11. Plant Reproduction
Simple plants spend
most of their time as
gametophytes.
Complex plants
spend most of their
time as sporophytes.
12. Non-vascular Mosses (Bryophytes)
The simplest land plants are the bryophytes. They are non-
vascular, which means they have way to move nutrients around the
organism; no roots, steams, or leaves. This limits their growth height to
~5 cm high.
Hornworts (left) and liverworts (right) are bryophytes.
13. Non-vascular Mosses (Bryophytes)
Gametophyte bryophytes produce sperm in their antheridia and eggs in
their archegonia. They rely on wet conditions (rain, fog) for their sperm
to swim to nearby eggs and fertilize to make a gametophyte.
15. Vascular Mosses (Lycophytes)
Lycophytes are the oldest and simplest vascular plants on Earth.
Their appendages
(leaves) have a
single unbranched
vein to transport
nutrients.
16. Vascular Mosses (Lycophytes)
Vascular tissues are called either xylem or phloem, depending on what
they are transporting. Their main functions are:
xylem – carries
water and some
nutrients upward
phloem – carries sugar
and other nutrients
downward
18. Ferns (Pterophytes)
Pterophytes are vascular plants that typically have branching
veins in their appendages. They are commonly called ferns.
19. Seed-Bearing Plants
In mosses and ferns, after the sperm from a gametophyte fertilizes the
egg from another gametophyte, the new sporophyte grows and begins
to make spores that can be spread to make new gametophytes.
male
gametophyte
female
gametophyte
sperm
egg
fertilization
sporophyte
spores
male and female
gametophytes
20. Seed-Bearing Plants
Seed-bearing plants, like the dandelion, are different. After the
sperm fertilizes the egg, the plant makes diploid seeds that must be
planted and germinate to make more sporophytes.
The gametophyte stage only occurs in the part of the plant that
makes the seeds.
Sperm and eggs
are made by the
sporophyte.
Seeds are made. New sporophytes
grow from the seeds.
Fertilization
21. Seed-Bearing Plants
A seed consists of a protective coat, an embryo sporophyte, and
nutrients to feed the embryo for a short time after germination.
22. Conifers (Gynosperms)
Gymnosperms are seed-bearing plants that use cones as reproductive
structures.
Male cones contain pollen (sperm). When pollen reaches a female cone
containing the ovule (eggs), the egg is fertilized and becomes a seed.
The cones of
Agathis
philippinensis.
Left: Male
Right: Female
24. Flowering Plants (Angiosperms)
Angiosperms are plants that flower. Flowers contain pollen and/or
ovaries (eggs).
After fertilization, the fertilized ovary becomes surrounded by a
fruit, which helps protect and disperse the seeds that are made.
