Plants
Kingdom: Plantae
Sporophytes are diploid and gametophytes are haploid.
Review Photosynthesis and Cellular Respiration
Plant provide the base for food chains on land. They
also provide shade, shelter and oxygen for animals.
Plant Life Cycle
Plant life cycle has 2 alternating phases, a diploid (2N)
phase and a haploid (N) phase. This is known as
alternation of generations.
Mitosis and meiosis alternate to produce the 2 types of
reproductive cells which are the spores and gametes.
Diploid (2N) phase is known as the sporophyte or spore
producing plant.
Haploid (N) phase is known as the gametophyte or
gamete producing plant.
Plant Life Cycle
Plant spores are haploid (N) reproductive cells formed in the
sporophyte plant by meiosis that can grow into new
individuals is the gametophyte.
Gamete is a reproductive cell that is produced by mitosis
and fuses during fertilization with another gamete to
produce a new individual, the diploid sporophyte.
The earliest type of plants, mosses and ferns, required water
to reproduce. Seed plants have evolve reproductive cycles
can be carried out without water. Many plants have forms of
vegetative or asexual reproduction. See Figure 22-2
Movement of H2O and Nutrients
Plants takes up water and mineral through their roots
and make food in their leaves.
Specialized tissues carry water and nutrients upward
from the soil and distribute the products of
photosynthesis throughout the plant body. Simpler
types of plants carry out these function by diffusion.
Early Plants
The first plant evolved from an organism much like the
multicellular green algae living today. Land plants
evolved from green algae.
Early plants evolved structures that acquire, transport ,
and conserve water.
Green algae have cell walls and photosynthetic pigments
that are identical to those of plants. They have
chlorophyll that captures energy from the sunlight
during photosynthesis. Both use starch as a storage
product
Early Plants
Most green algae have cell walls made of cellulose which is
found in the cell wall of all plants.
Evidence from genetic analysis points to an ancient species of
green algae that is the common ancestor of all plants. Today
the species would be classified as a member of the class
Charophyceae.
Today, charophyceans are common in freshwater habitats.
Ancestral charophycean species may have grown in shallow
water the dried out from time to time
Early Plants
Several important plant characteristics likely originated
in the charophyceans are:
1. multicellular body, which lead to specialize cells
and tissues
2. Cell division which produced cells with small
channels in their walls
3. Reproduction where the sperm travels and
fertilize an egg cell.
True plants have multicellular embryos that remain
attached to the female parent as they develop
Early Plants
The earliest plant fossil date to more than 450
million years ago. The first true plant grew on
the edges of lakes and streams. They relied
on droplets of water that bought sperm to
eggs to produce the next generation of plants.
Their structure was similar to moss, keeping
low to the ground to retain moisture.
Descendants were able to live in even drier
areas
Early Plants
Fossils suggest the first true plant depended on water to
complete their life cycles. The evolved of plants are
more resistant to the drying sun. These plants are
capable of conserving water and reproduce without
water.
Plant Adaptation for Land
Algae is constantly surrounded by water
which is needed for photosynthesis. The
buoyancy of water supports the weight of
most algae. Water provides the medium
through which the sperm and spores can
travel, allowing for reproduction and
dispersal. Water prevents sperm, eggs, and
the developing offspring from drying out.
Plant Adaptation for Land
The challenges of living on drier land acted as
selective pressures for plants. Plants evolved
adaptations that allowed them to retain
moisture, transport water and other resources
between plant parts, grow upright, and
reproduce without free standing water.
Plant Adaptation for Land
Retaining Moisture
The surfaces of plants are covered with a cuticle. A
cuticle is a waxy, waterproof layer that helps hold in
moisture. The are tiny holes in the cuticle called the
stomata. Special cells that allow stomata to close to
prevent water loss or to open to allow air to move in and
out. Without the stomata the movement of air would be
prevented by the cuticle.
Transporting Resources
Taller plants has better access to sunlight and CO2 from
the air but they must get water and nutrients from the
soil. A structure for moving the resources to different
parts of the plant evolved in the form of a vascular
system.
Vascular system is specialized tissue that bring water
and mineral nutrients up from the roots and disperse
the sugar from the leaves. This system allows a plant to
grow higher off the ground
Plants Growing Upright
Lignin a substance which hardens the cell wall of some
vascular tissues. Lignin also strengthens wood and
provides stiffness the stems of other plants. Lignin
allows to retain their structure as they grow toward the
sun.
Reproducing on Land
Eggs are fertilized within the tissue of the parent plant.
The fertilized egg develops into an embryo. Some plants
use raindrops or dew for reproduction. Other plants do
not need free standing water for reproduction. These
plants have adaptations that allow seed plants to
reproduce.
Pollen grain is a 2 celled structure that contain a cell that
will divide to form a sperm. This pollen can be carried
by the wind or animals to a female structure.
Reproducing on Land
Seed is a storage device for a plant embryo. The seed
has a hard coat to protect it from drying wind and
sunlight. When the conditions are right, the embryo can
develop into an adult plant.
Mutualism
Mutualism in interaction between 2 species where both
of the species are benefiting.
Example: plant’s roots and fungi and bacteria
The roots provide a habitat for the fungi and bacteria
while the fungi and bacteria helps the plant to get
nutrients from the soil.
Flowering plants depends on the animal species for
pollination or seed dispersal. The animals are fed by the
pollen, nectar or fruit.
Plant-Herbivore Interactions
Plants have a variety or adaptations to keep animals from
eating them. Plants have spines, thorns and chemical
that act as pesticides against plant eating predators.
The larvae of monarch butterflies, feed on milkweed
species. Milkweed plants produce a chemical that
makes the monarch larvae, adults , and even eggs taste
bad to predators. The butterfly has a chemical
protection as a result of eating the milkweed leaves
during its development.
Fruits and Seed Dispersal
Biologically, a fruit is a flower’s ripen ovary which
surrounds and protects the seed or seeds.
Fleshy fruits are tasty food sources for animals, which
digest the fruit tissue but not the seeds. Seeds pass
through the animal and are deposited along with a
supply of fecal fertilizer that helps during germination.
Others may cling to wildlife or fibers that help spread
seeds by wind.
Flowers and Pollination
Flowers have more efficient pollination than
gymnosperms which relies on the wind for
pollination. Animal pollinators transfer
pollen from flower to flower in a very targeted
way. Therefore; flowering plants pollinated
by animals don’t need to produce nearly as
much pollen as the plants that rely on wind to
randomly transfer the pollen.
Classifying Flowering Plants
Flowering plants are classified into 2 groups
based on 2 basic kinds of seed: seeds with
one or two cotyledons
Cotyledon is an embryonic leaf inside a seed.
They are often called “seed leaves”. As embryo
develop, the seed leaf may remain inside of
the seed while others may break our of the
seed and turn green.
Monocot
Monocots are flowering plants whose embryo has one
seed leaf.
Monocots plants have parallel veins in long, narrow
leaves, like those in an iris of lily. Their flower parts
occur in multiples of 3, and bundles of vascular tissues
are scattered throughout the stem.
Cereals plants such as corn, wheat, and rice. Also
grasses, irises, and lilies.
Dicots
Dicots are flowering plants that have 2 seed leaves.
Dicots have leaves with netlike veins. The flowers are in
multiples of 4 or 5 and bundles of vascular tissue are
arranged in rings.
Deciduous trees that lose their leaves in the Fall are
dicots. Peanuts are dicots.
Herbaceous or Woody Stems
Wood is a fibrous material made up of the vascular
system of some plats. High concentration of lignin and
cellulose make the cell walls of these cells thick and stiff.
Vines have woody stems.
Plants that do not produce wood, such as cucumbers and
marigolds are called herbaceous plants.
Three Types of Lifespans
Annual – flowering plants mature from the seed,
produce flowers, and die all in one year. Ex. Corn and
lettuce
Biennial – flowering plants that take 2 years to complete
their life cycle. The first year they produce a short stem
leaves that grow close to the ground and underground
food reserves. During the second year, a taller stem,
leaves, flowers, and seeds. Ex. Carrots
Perennial- any flowering plant that lives for more than 2
years. Ex. Trees or die and grow back in the spring.
Type of Plant Cells
Plants cell have the same organelles as an animal cell
plus cell wall, plastids and a large vacuole.
Parenchyma – thin wall and water filled vacuole in the
middle. Found throughout a plant. It stores starch, oils,
and water for the plant.
Photosynthesis takes place in the green chloroplast
within the parenchyma cells in the leaves. Chloroplast
and colorless plastids in parenchyma cells within roots
and stem store starch. They divide their entire lives and
helps with healing or regenerating new parts.
Types of Plant Cells
Collenchyma Cell has cell wall that range from thin to thick,
providing support while allowing a plant to grow. Cells are
found in younger tissue of leaves and shoots. The unique
feature is the cells are flexible. The cells can elongate and
still give the leaf structure.
Sclerenchyma Cells – is the strongest type of cell. They have a
2nd cell wall which contains lignin making the cells very
tough and durable. When the cell dies the dead cell
disintegrate but the rigid cell wall is left behind as skeletal
support of the water-conducting tissue for the plant.
Sclerenchyma forms the fruit pit and the harder outer shell of
nuts. Cells make linen and rope.
Three Tissue Systems
The plasmodesmata is the system that connects
neighboring cells where cytoplasm that pass through
openings in cell walls and connect living cells. The cells
can share water nutrients, and chemical signals.
Three Tissue Systems
Dermal Tissue System – covers the outside of a plant
and protect in a variety of ways. Dermal tissue
epidermis) is made of live parenchyma cells in the
nonwoody parts of the plants.
Epidermal cells secrete a wax-coated substance that
becomes the cuticle.
Dermal tissue made of dead parenchyma cells makes up
the outer bark of woody plants.
Three Tissue Systems
Ground Tissue System – makes up much of the inside of
a plant. It provides support and stores materials in the
roots and stems. The ground tissue in leaves is packed
with chloroplast for photosynthesis.
Ground tissue consist of all 3 simple tissue types:
parenchyma tissue, collenchyma tissue, and
sclerenchyma tissue. Parenchyma is the most common
in ground tissue.
Three Tissue Systems
Vascular Tissue System transport water, minerals
nutrients, and organic compounds (sugars) to all parts
of the plant. The vascular system is made up of 2
networks of hollow tubes somewhat like our arteries and
veins.
Each network has a different type of vascular tissue to
move different resources throughout the plant.
Three Tissue Systems
Xylem is the vascular system that carries water dissolved
mineral nutrients up from the roots to the rest of the
plant. Xylem contains other types of cells so it is called a
complex tissue
Phloem is the vascular tissue that carries the products of
photosynthesis through the plant.
The Vascular System
Tracheid is a long narrow specialized cell in the xylem.
Water can flow from cell to cell through openings in the
thick wall.
Vessel elements are specialized cells in xylem. They are
shorter and wider than tracheids. When the vessel
elements die, the cell wall disintegrates at both ends.
The cell connect end to end and forms a long tube.
The Vascular System
Cohesion-tension theory –the physical properties of
water allow the rise of water through the plant without
metabolic energy. The theory is based strong attraction
of the water molecule to one another and to other
surfaces. The tendency for hydrogen bonds to form
between water molecules creates a force called cohesion.
Plant Kingdom
Four groups based on 3 features:
1. Water conducting tissues
2. Seeds
3. Flowers
4. Reproductive structures
The first plant evolved from a green algae living in fresh
water not in the sea as once thought.
Flowering plants have 235,000 species.