1. Aim: What are plants and how are they classified?

2. What are plants?
A plant is a multicellular autotroph that have cell walls
and in which the embryo develops within the female
parent.
Developing Seed
Embryo

3. Origin of Plants:
The closest modern relatives of the ancestors of plants
are the multicellular green algae (live in water).
The evolution of modern
plants required many
adaptations for the
survival of autotrophic
organisms on dry land.
Adaptations:
Roots
Stems
Leaves

4. Challenges of Life on Land:
Obtaining Resources from Air & Soil – algae and
other aquatic organisms acquire the resources they
need from the surrounding water. Land plants have
to obtain resource from land (roots) and air (stems &
leaves).
Vascular Tissue – vessels
responsible for transporting
materials from leaves and
roots.

5. Challenges of Life on Land:
Staying “Afloat” in Air – In an aquatic environment,
the buoyancy of water provides physical support for
large algae. Lignin is a chemical that hardens the
plants’ cell walls and allows them to stand upright on
land.

6. Challenges of Life on Land:
Maintaining Moisture – Plants have to maintain a
moist internal environment even on dry land.
Cuticle – waxy substance that coats the plant to
keep in moisture.
Stomata – pores in the leaf surface that allow
for gas exchange and regulate water loss.
Stomata
Guard Cells

7. Challenges of Life on Land:
Reproducing on Land – Terrestrial plants require
adaptations that ensure that the gametes and the
developing embryo will not dry out. Plants must also
have some means of dispersal other than water currents
**Pollen & Seeds
are usually
dispersed by wind
and animals.
Pollen prevents sperm
from drying out
Seeds prevent embryo
from drying out

8. How are plants classified?
Bryophytes:
First land plants
Include mosses
Nonvascular plants
(grow close to the ground)
4) Lack Seeds
Mosses

9. How are plants classified?
Pteridophytes:
Have Vascular Tissue
Lack Seeds
Have Lignin in cell walls
Ferns

10. How are plants classified?
Gymnosperms:
Have Vascular tissue
Have seeds (plant embryo & food supply)
Seeds are “naked”
(not enclosed in an ovary)
4) Have Pollen (male sperm)
Female Pollen Cone contains
Female gamete (egg)
Pine Tree

11. How are plants classified?
Angiosperms:
Have Vascular tissue
Flowering plants (flower is a reproductive structure)
Have seeds surround by ovaries
(fruit)
4) Have pollen
Ovary
Seed

12. Diversity of Angiosperms:
Cotyledon – part of
the seed responsible
for storage of food
for the embryo.