Transcript Plants - msdemarco

Plants
What is a Plant?
• Plants are
– Autotrophs
– Eukaryotes
– Multi-cellular
What is a Plant?
• Most plants are autotrophs, which means that
they make their own food.
• Sunlight provides the energy for the plant
food-making process, which is known as
photosynthesis.
– During photosynthesis, plants use carbon dioxide
and sunlight to produce food and oxygen.
What is a Plant?
• Plants are eukaryotes, which means that they
have a nucleus.
• Although plants vary greatly in size, they all
contain multiple cells, which are organized
into tissues.
What is a Plant?
• Unlike animal cells, plant cells contain a cell
wall which protects the cell.
• Plant cells also contain chloroplasts which
capture sunlight and undergo photosynthesis.
This is what gives plants their green color.
Living on Land
• Most plants live on land.
• In order to be able to live on land, plants must
be able to
– Obtain water and nutrients
– Retain water
– Transport materials
– Support their bodies
– Reproduce
Living on Land
• Most plants use their roots to suck water and
nutrients up from the ground.
Living on Land
• Most plants retain water by having a waxy,
waterproof layer that covers their leaves
called a cuticle.
Living on Land
• Like all organisms, plants must be able to
transport materials to different parts of its
body.
• Larger plants have transporting tissue called
vascular tissue. Vascular tissue is a system of
tubelike structures where water and other
substances are transported through the plant.
Living on Land
• For small plants, support is not an issue, but
for larger plants, rigid cells walls and vascular
tissue strengthen and support the plant’s
bodies.
Living on Land
• All plants undergo sexual reproduction.
• Fertilization occurs when the sperm cell unites
with an egg cell creating a fertilized egg, or
zygote.
The Origin of Plants
• The oldest plant fossils are about 400 million
years old.
• These fossils already had many adaptations
for land life, including vascular tissue.
The Origin of Plants
• Land plants and green algae have very similar
forms of chlorophyll, and their genetic
material is similar.
• Because of this, many biologists believe plants
evolved from ancient green algae.
Plant Life Cycles
• Plants have complex life cycles that include
two different stages:
– The sporophyte stage
– The gametophyte stage
Plant Life Cycles
• The sporophyte stage
– The plant produces spores, which are tiny cells
that can grow into new organisms.
– The spore then develops and enters the
gametophyte stage.
Plant Life Cycles
• The gametophyte stage
– The plant produces two kinds of sex cells: sperm
cells and egg cells.
– These cells then join and create a zygote.
– The zygote grows and develops into a sporophyte,
which creates more spores, starting the cycle over
again.
Classification of Plants
• Scientists classify plants into two major
groups:
– Nonvascular plants
– Vascular plants
Nonvascular Plants
• Nonvascular plants do not have a welldeveloped system of tubes for transporting
water and other materials.
• They are low-growing and do not have roots
for absorbing water from the ground.
Nonvascular Plants
• Nonvascular plants obtain water and materials
directly from their surroundings.
• The materials then pass from one cell directly
to another.
• This type of transport is slow and does not go
very far.
Nonvascular Plants
• Nonvascular plants normally live in damp,
shady places so that they can easily access
water.
• Nonvascular plants have very thin cell walls
and cannot grow more than a few centimeters
tall.
Nonvascular Plants
• There are three major groups of nonvascular
plants:
– Mosses
– Liverworts
– Hornworts
Mosses
• Mosses are the most diverse group of
nonvascular plants, with more than 10,000
species.
Mosses
• The familiar green, fuzzy moss is the
gametophyte generation of the plant.
• Thin, rootlike structures called rhizoids hold
the moss and absorb water and nutrients.
• The sporophyte generation then grows up out
of this in long, slender stalks, with a capsule at
the end that contains spores.
Liverworts
• There are more than 8,000 species of
liverworts.
• Liverworts are named because they grow in
the shape of a human liver.
– Wort means “plant”.
• Liverworts grow as a thick crust on moist rocks
or soil along the sides of streams.
Hornworts
• There are less than 100 species of hornworts.
• Hornworts are named after the sporophyte
generation that appear as slender, curved
structures that look like horns.
• Hornworts are found in moist soil, normally
mixed with grass plants.
Vascular Plants
• Vascular plants have true vascular tissue,
which allows transport of materials quickly
and efficiently through the plant’s body.
• Vascular tissue also provides strength,
stability, and support allowing vascular plants
to grow tall.
Vascular Plants
• Vascular plants can be broken down into two
groups:
– Seedless plants
– Seed Plants
Seedless Plants
• Seedless vascular plants do not produce
seeds. Instead they produce spores.
• Because they produce spores instead of seeds,
these plants must live in moist surroundings,
so that the sperm can swim toward the egg
during the gametophyte stage.
Seedless Plants
• Seedless vascular plants have very strong cell
walls, which gives them strength and stability.
• This allows them to grow much taller than
nonvascular plants.
Seedless Plants
• Seedless plants are broken down into three
groups:
– Ferns
– Club Mosses
– Horsetails
Ferns
• There are more than 12,000 species of ferns,
making them the most diverse seedless
vascular plant.
• Ferns range in size from a few millimeters to 5
meters tall.
Ferns
• Like all vascular plants, ferns have stems,
roots, and leaves.
• The stems of most ferns are underground,
while the leaves grow upward from the top of
the stems and the roots grow downward from
the bottom of the stems.
Ferns
• The fern’s leaves, or fronds, are divided into
many smaller parts, that look like small leaves.
Ferns
• The regular fern is the sporophyte generation
of ferns and develops spores on the underside
of its fronds.
• The gametophyte generation appears as tiny
plants low to the ground.
Club Mosses
• There are very few species of club mosses.
• Club mosses are not the same as regular moss
because it has vascular tissue.
• Club mosses grow in moist woodlands and
near streams.
Horsetails
• There are only about 20 species of horsetails
on Earth today.
• The stems of horsetails are jointed and have
needlelike branches coming out of the joints.
• Horsetails get their name because they
resemble a horse’s tail.