Plant Diversity & Life
Cycle
Section 1: Intro to Plants
I. What is a Plant?
A. Basics
1.
2.
3.
4.
Multicellular
Eukaryotic
Autotrophic
Cells have cell walls made of
cellulose
B. Autotrophic
1. Photosynthesis – produces organic
compounds (a.k.a. food) using
sunlight and CO2
2. Requires Chloroplasts – organelles
where photosynthesis takes place
II. Establishment of Plants on Land
A. Nonvascular Plants – 1st evolved
from a multicellular green algae
1. Lack vascular tissue for transporting
water & nutrients
2. Grow close to the soil to get moisture
B. Vascular Plants – later evolved from
a group of nonvascular plants
1. Have vascular tissue for transporting
water & nutrients from roots to leaves
and organic material back down to the
roots.
2. 1st vascular plant was named Cooksonia
C. Absorbing Nutrients
1. Early plants lacked roots. Relied on fungi
for nutrients from the soil.
D. Preventing Water Loss
1. Cuticle – waxy covering that covers
leaves & stems to prevent water loss
through evaporation
2. Stomata – pores in leaves that allow O2,
CO2, & water to move in/out of plant
3. Roots obtain water from soil, replacing
water lost to the atmosphere
Cuticle
Stomata
E. Dispersal on Land
1. Spores – early plants produced spores
that dried out & were carried by wind
2. Pollen – special type of spore used by
seed plants; carries sperm cell
3. Seeds – plant embryo packaged with a
food source that can be carried by wind,
water, or animals
III. Plant Life Cycle
*Alternation of Generations
A. Plants have 2 stages:
1. Sporophyte Stage – multicellular,
diploid stage that produces haploid
spores through meiosis
2. Gametophyte Stage – multicellular,
haploid stage (a spore grows into this)
that produces gametes (sex cells)
through mitosis
*Plant life cycles alternate between haploid
gametophyte & diploid sporophyte.
Alternation of Generations
Section 2: Seedless Plants
*2 Groups of Seedless Plants:
Nonvascular & Seedless Vascular
I. Nonvascular Plants
A. Characteristics
1. Small, short – water transport is
through osmosis which only occurs
over short distances
2. Reproduce through spores
3. Lack true roots, stems, & leaves –
no vascular tissue for transporting
water
B. 3 Groups of Nonvascular Plants:
Bryophytes
1. Mosses
• Has cuticle, stomata, & conducting cells
• Green, leafy mosses are the haploid
gametophyte
• A bare stalk with a spore capsule on
top is the diploid sporophyte
2. Liverworts
• No cuticle, stomata, or conducting
cells
• Gametophytes are flattened, lobed
leaf-like structure
• Sporophyte is a short stalk with a
spore capsule
3. Hornworts
• No conducting cells
• Gametophyte is green & flattened
• Sporophyte is hornlike & has
stomata & cuticle
II. Seedless Vascular Plants:
Pteridiophytes
A. Characteristics
1. Sporophyte is larger because it has
vascular tissue & has true roots,
stems, & leaves
2. Gametophyte is much smaller as it
lacks vascular tissue
• Also grows on or under the soil
B. 2 Groups of Seedless Vascular Plants
1. Club Mosses
• Has roots, stems, & leaves
• Rhizome – underground stem; roots
grow down from this, while leafy
green stems grow up & out of the
ground from it.
2. Ferns - what you know of as a fern is
the sporophyte
• A rhizome is anchored by roots
• Leaves are called fronds
• Sorus (sori, plural) – cluster of
sporangia, structures that produce
spores; found on the underside of
the fronds
• Gametophyte is flat, heart-shaped,
& less than 1 cm across (1/2 inch)
Fern Gametophyte:
Fern Example:
Sori:
C. Spores of Seedless Vascular Plants
1. Have thickened walls to withstand
drying out
2. Easily dispersed by wind
3. Are produced either in cone-like
structures or in sori.
Section 3: Seed Plants
I. 2 Groups of Seed Plants
A. Gymnosperms
•
•
Seeds do not develop with in a fruit
Most seeds develop inside a cone
B. Angiosperms
•
•
•
Seeds develop within a fruit
Fruits develop from part of a flower
Angiosperms are also called
flowering plants
II. Reproduction is Seed Plants
*Greatly reduced gametophyte (microscopic!)
& dominant sporophyte
A. Basics
1. Sporophytes produce 2 types of
spores, each develop into a specific
type of gametophyte (male or female)
• Female gametophyte develops
inside an ovule & produces the
female egg.
• Male gametophyte develops inside
a pollen grain & produces sperm.
B. Pollination & Fertilization
1. Pollination – transfer of pollen from
male reproductive structure of a plant
to the female reproductive structure.
• Wind & animals help in dispersing
pollen
2. Fertilization – fusion of an egg with a
sperm
• A pollen tube grows from pollen
grain to the female ovule
• Sperm can then travel to the ovule
& fuse with the egg.
C. Seed Formation
1. After fertilization, the ovule develops
into a seed.
2. Outer layers of the ovule develop into
the seed coat, which protects the
embryo inside.
3. Inner layers of the ovule develop into
nutrients for the embryo.
D. Seed Dispersal
1. Many seeds have structures that help
wind, water, or animals carry them
away from the parent plant.
2. Dispersal by Wind
• wing-like or parachute-like
structures carry seeds
3. Dispersal by Animals
• Hooks cling to animal fur
• Fruits surround seeds, are eaten,
and pass undigested through
animal’s body
III. Gymnosperms
A. 4 Groups
1. Conifers
• Needle or scale like leaves
• Some of the tallest, oldest trees
are conifers
• Pollen grains disperse by wind
2. Cycads
• Short stems, palm-like leaves
• Plants are either only male or
female
• Pollen grains dispersed by insects
3. Ginkgoes
• Only 1 living species (maidenhair tree)
• Plants are either male or female
• Pollen dispersed by wind
4. Gnetophytes
• Unique group of trees, shrubs, &
vines
B. Gymnosperms develop Cones
1. Cones – where gametophytes develop
• Are whorls of modified leaves called
scales
2. Two types of Cones
• Male cones produce pollen grains in
sacs under scales
• Female cones produce ovules on scales
3. Many plants produce both male & female
cones on the same plant, while others
only produce one type of cone per plant.
Section 4: Flowering Plants
I. Kinds of Angiosperms
A. Monocots
1. Seeds have 1 cotyledon – embryonic
leaf
2. Long, narrow leaves with parallel veins
3. Flower parts are in multiples of 3
B. Dicots
1. Seeds have 2 cotyledons
2. Broader leaves with branching veins
3. Flower parts are in multiples of 4 or 5
II. The Flower
A. What is a flower?
1. Specialized reproductive structure
2. Both male and female gametophytes
develop within a single flower
B. Flower Structures
1. Sepals – small leaves that protect the
outside of the flower
2. Petals – colored leaves to attract
pollinators
3. Stamen – male part; produces pollen
• Anther – top of stamen where
pollen is produced
• Filament – stalk that supports of the
anther
Plant Sepals
Anther
4. Pistil – female part; produces ovules
• Stigma – sticky tip of pistil to grab
pollen
• Style – stalk that supports stigma
• Ovary – base of pistil where
ovules develop
III. Pollination
A. Types of Pollination
1. Self-Fertilization – plant’s pollen can
fertilize the same plant’s ovules
2. Cross-Fertilization – plant’s pollen
must fertilize ovules from a
different plant
B. Attracting Pollinators – animals pick
up pollen & carry it to another plant
1. Brightly colored petals – bees, birds
2. Sugary nectar
3. Strong odors - bats, moths that feed at
night
4. Attractive shapes
**Wind can also disperse pollen.
IV. Fruits
A. What is a fruit?
1. After ovules are fertilized, the ovary
of a flower develops into a fruit.
2. Fruits provide some protection for
seeds, but function mainly in seed
dispersal.
B. Seed Dispersal
1. Animals eat the fruits & the seeds pass
through the animal undigested as the
animals move around.
2. Some fruits have structures that help
them float on wind or water.
3. Others forcefully eject their seeds.
Exploding Seeds
V. Vegetative Reproduction
A. Asexual Reproduction
1. Plants can reproduce via stems,
roots, and leaves.
2. Reproduction involving these parts
is called vegetative reproduction.
B. Benefits
1. Much faster
2. A single plant can spread rapidly in
an area ideal for its growth
C. Examples
1. Tubers (roots) – potatoes, yams, ginger
2. Stems – celery, green onion, asparagus
3. Leaves – lettuce, spinach
Section 5: Plant Tissue Systems
I. Plant Tissue Types
A. Dermal tissue – protective, outer
layer of a plant
B. Vascular tissue – forms strands
that conduct water, minerals, &
organic compounds through plant
C. Ground tissue – makes up inside
of nonwoody plants (roots,
stems, leaves)
II. Dermal Tissue
A. Epidermis – “skin” of nonwoody
plants
1. Usually a single layer of cells
2. Can form hair-like extensions
• On stems & leaves, hairs trap
moisture close to surface to
prevent water loss
• On root tips, root hairs increase
surface area for more absorption
B. Cuticle – waxy covering over
epidermis
1. Protects plant
2. Prevents water loss by repelling
water
C. Dermal Tissue of Woody Plants
1. Several layers of cells and is called
cork.
2. Contains a waterproof chemical.
3. Lacks a cuticle
4. Protects plant, exchanges gases, &
absorbs minerals
D. Stomata
1. Cuticle will not allow gases to pass
though it, so plants need a way to
bring CO2 in and let O2 out.
2. Stomata are pores that permit the
exchange of these two gases.
3. Guard cells border each stomata
and open/close them.
4. When open, plants gain CO2 but lose
water.
5. When closed, plants conserve water,
but photosynthesis slows (no CO2).
Stomata
III. Vascular Tissue System
A. Xylem
1. Composed of thick-walled cells that
conduct water/minerals from roots
through stems to the leaves.
2. At maturity, xylem cells are dead,
leaving only cell walls.
B. Phloem
1. Composed of cells that conduct sugars
&nutrients throughout plant’s body.
2. Cells are alive at maturity, & contain
cell walls, cell membrane, &
cytoplasm. Cells lack most organelles.
IV. Ground Tissue
A. Location
1. Found between dermal and vascular
tissue.
2. Most abundant in nonwoody plants.
3. Most cells remain alive with thin cell
walls and nuclei.
4. Cells with thicker cell walls lose
their nuclei & cell contents as they
mature (they die ).
B. Function depends on location in a
plant
1. In leaves, ground cells perform
photosynthesis.
2. In stems & roots, ground cells mainly
support the plant & store water,
sugar, & starch.
3. In angiosperms, ground tissue makes
up the flesh of fruits.
4. Ground tissue is mainly absent in
woody plants.