Download Diversity of Life

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Lesson 3.1 – What is a Plant?
 Oldest
plants are 400 million years old.
 Contain chlorophyll, just like algae and some
bacteria
 Most are autotrophs (producers)
 Most are multicellular
 All have cell walls
 Plants
undergo photosynthesis -- recall that
in this process, plants use sunlight, water,
and carbon dioxide to produce food and
oxygen.
 All
plants (except green algae) have many cells
organized into tissues.
 The
cells differ from animal cells because they
have a cell wall made of cellulose to make them
stronger.
 They also have chloroplasts and a large central
vacuole.
 Obtain
water through roots.
 Retain water using the waterproof cuticle layer.
 Support their structure with cell walls and tissue.
o Vascular tissue: xylem and phloem transport materials
throughout the plant
 Reproduction
in the absence of water.
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Lesson 3.2 – Classifying Plants
 Nonvascular
plants: plants that lack vascular
tissue to transport materials.
 Low-growing
 Thin cell walls
 Do not have roots for absorbing water
 Most live in damp, shady places and obtain
materials from their surroundings.
 Most
diverse NV plant (10,000+ species)
 Thin, root-like structures (rhizoids) anchor
the moss and absorb materials.
 A slender stalk grows with a capsule at the
end.
o The capsule contains spores for reproduction.
 8,000+
species
 “wort” means “plant”
 Shaped like a human liver
 Often found growing like a crust on moist
rocks or soil.
 Less
than 100 species
 Have curved structures (horns) growing out
of the plant
 Usually live in moist soil
 Vascular
plants have much more strength and
stability than NV plants.
 Phloem moves food made in the leaves to other
parts of the plant.
 Xylem moves water and minerals from the roots
into the stems and leaves of the plant.
 Reproduce by using spores.
 12,000+
species
 Shady, moist areas
 Stems,
roots, and leaves; stems are
mostly underground.
 Leaves are called fronds and are
divided into smaller parts that look
like small leaves.
o Each frond has a cuticle to help retain
water.
 Young
leaves are called fiddleheads
and uncurl as they mature.
 Have
vascular tissue
 “ground pine” “princess pine” because it looks like
a pine tree branch.
 Grow in woodlands and near streams.
 About
30 species
 Grows in a whorled pattern
 “scouring brushes”
 Have
vascular tissues
 Use pollen and seeds to reproduce
 Roots, stems, and leaves
 Live in variety of climates
 Pollen:
tiny structures containing cells that become
sperm cells.
 Pollen delivers the sperm cells to the egg cells.
 After fertilization, seeds develop.
o Seed: structure that contains a young plant inside a
protective covering.
 Gymnosperm:
a seed plant that produces naked
seeds (not enclosed in a fruit).
 Needle-like or scale-like leaves
 Deep-growing roots
 Oldest type of seed plants (360 mya)
Cycads:
 Grow mainly in tropical areas
 Look like palm trees with cones
Conifers:
 Cone-bearing plants
 Most are evergreens that keeps their leaves or
needles all year
 Largest and most diverse group
Ginkgoes:
 Only one species, Ginkgo biloba
 Planted in cities because they tolerate air
pollution
Gnetophytes:
 Hot deserts and tropical rain forests
 Trees, shrubs, and vines
 Angiosperm:
flowering plants; produce flowers and
have seeds enclosed in fruits.
 Divided into two groups based on the number of
cotyledons they have – seed leaves that provide
food for the embryo inside the seed.
 Monocot:
only have one seed leaf; grasses, lilies,
and tulips are examples.
 Parallel veins
 Floral parts in multiples of 3
 Vascular tissue scattered throughout stem
 Many roots that spread out
 Dicot:
have two seed leaves; roses, maple trees,
and apples are examples.
 Branched veins
 Floral parts in multiples of 4 or 5
 Vascular tissue arranged in a ring
 One main root
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Lesson 3.3 – Plant Structures
 Functions:
o Anchor the plant
o Absorb water and minerals from soil
o Store food
 Structure:
o Root cap at the tip to protect
the root
o Root hairs grow out of the
surface to absorb materials
o Vascular tissue in the center
of the root

Desert roots spread far out
but stay close to the surface
so they can collect as much
rain as possible.

Forest roots do not need to
spread out; they go deep into
the ground to anchor the
trees. Some trees have prop
roots that begin above ground
to keep them very secured.
Many plants have fibrous roots which look like little
tree branches; helps prevent soil erosion and water
loss.
 Some plants have tap roots that grow straight down
into the ground, so they are able to reach water deep in
the ground.
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 Function:
o Carries substances using vascular tissue
o Provides support for the plant
o Holds up leaves to sun
 Structure:
o Woody stems
rigid (trees)
are hard and
• Outer layer of bark (cork)
with cambium inside to
produce new phloem and
xylem layers.
• Heartwood is at the center;
inactive xylem used for
support
o Herbaceous stems are soft
(most flowers)
o Both types of vascular
 Structure:
o Annual Rings: represent a tree’s growth; made
of xylem.
o Width of the rings can give info about the
weather conditions that year.
o Each ring represents one year.
 Function:
o Capture sunlight
o Photosynthesis
 Leaves
have veins going through them, which
hold the xylem and phloem.
 When the veins are full of water/nutrients, the
plant does not wilt.
 The
upper surface of the leaf: upper epidermis.
 Thin and flat; traps sunlight.
 Has a waxy covering which helps prevent water loss;
called a cuticle.
 Below
this layer is the palisade layer, which
contains tightly packed cells containing
chloroplasts.
 Then
is the spongy layer, which has loosely packed
cells to allow carbon dioxide to pass through the
cells.
 The
bottom layer is the lower epidermis.
 This layer contain several tiny pores, called stomata,
that can open and close to allow water and gases to
move in and out of the leaf. (transpiration)
o Guard cells are located around the stomata, and change
their shape forcing the stomata to open or close.
 Three
main parts:
o Embryo: young plant that develops from the zygote
(fertilized egg)
o Stored food: helps the embryo grow
o Seed coat: outer covering of a seed; protects the seed from
drying out
 Scattering
of seeds – the further they go, the better
chance for survival
 Animals eat food and the seeds are deposited in new
areas
 Burrs around seeds get stuck in animal fur
 Wind and water carry seeds
 Germination:
when the embryo begins to grow and
push out of the seed
 Uses water and stored food to grow; first downward
(roots), then upward (stem).
 Flower:
reproductive structure; attracts insects and
animals.
 Pollination: the transfer of pollen from male rep.
structures to female rep. structures.
 Sepals:
leafy
structures that
enclose flower
before blooming;
form base for flower.
 Petals:
leafy
structures arranged
in a circle around
the pistil; colorful to
attract plant
pollination.
 Stamen:
male rep.
part; filament-stalk
and anthersproduces sperm
cells.
 Pistil:
female rep.
part; ovary-at base,
contains egg;
stigma- where
pollen attaches.
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Lesson 3.4 – Plant Reproduction
 Two
stages:
 Sporophyte- the plant produces spores which develop
into a gametophyte.
 Gametophyte- the plant produces two kinds of cells:
sperm cells and egg cells (rep. cells).
 Angiosperms
are classified based on the length of
their life cycles.
o Annuals: complete a life cycle in one growing season
o Biennials: complete a life cycle in two growing seasons;
first year they mostly grow roots, second year they grow
taller with flowers.
o Perennials: plants that live for more than two years
 All
plants reproduce sexually with fertilization
– when a male and female cell unite.
 the fertilized egg is a zygote.
 Some
plants reproduce asexually.
 New plants grow from the roots, leaves, or stems of
“parent plants”.
 Can happen quickly, but can lead to unfavorable
traits (genetically identical).
 These
plants need water in order for male cells
to travel to female cells (produced by the
gametophyte).
 Reproductive
structures called cones – covered with
scales; there are female and male cones.
 Male cones = pollen grains (sperm cells); female
cones = ovules (contains 2 egg cells).
 Wind often carries pollen to a female cone, where the
pollen gets stuck.
 The
ovule encloses the pollen, and it fertilizes an egg.
The zygote develops into an embryo.
 Female cones remain on the tree to allow the embryo
(seed) to develop; the male cones usually fall off.
 When seeds mature, scales open and the wind
carries them away.
 Pollen
falls on a flower’s stigma (pollination).
o Wind and other organisms, called pollinators, help this
process.
 Sperm
and egg join together in ovule (fertilization).
 Zygote develops as part of seed.
 Zygote
develops as part of seed.
 Ovary changes into a fruit; the seeds are dispersed
because of the fruit.
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Lesson 3.5 – Plant Responses and Growth
 Tropism:
a plant’s growth response toward or away
from a stimulus
o Growing toward something is a positive tropism
o Growing away from something is a negative tropism
 Called
phototropism
 Leaves, stems, and flowers grow toward light
 The plant hormone auxin speeds the rate at which
cells grow in response to light.
 Plant’s
response to gravity; caused by the pull of
gravity on cells at the end of the roots.
 Causes the roots to grow down and the stem to
grow up.
 Without this, plants would not be able to grow from
seeds.
 Some
plants, like the Venus Flytrap and mimosa,
respond to touch.
 The VF closes its leaves to trap insects when they
land on it; the mimosa curls all of its leaves when it
is touched.
 Short-day
plants: need only a few hours of
sunlight to grow.
 Long-day plants: need many hours of
sunlight to grow.
 Day-neutral plants: can grow in any amount
of sunlight.
 Dormancy:
a period
when an organism’s
growth or activity
stops.
 Cooler weather
causes plants to
stop making
chlorophyll,
changing green
leaves into red,
orange, and yellow.
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Lesson 3.6 – Plants in Everyday Life
 Food
for people and animals
 Shelter for animals and insects
 Shade and oxygen
 Many other ways also!
 Green
algae is used in scientific research and as a
thickening agent in foods.
 Other plants are used to treat medical conditions.
 Gardening and agriculture
 Paper and lumber
 Linens, furniture, tires, etc.