Structure and
Function in Living
Systems
Chapter 8: Systems in Organisms
8.1: Systems help organisms meet their needs
8.2: Plants have several levels of organization
8.3 Animals have several levels of organization
8.4 Human health depends on a balance among systems
Plants have several
levels of organization
 1. Living organisms need only water and air to survive.
 Living organisms need energy, materials, water, and air to
survive.
 2. Plants and animals are multicellular organisms.
 true
 3. If the muscles in the heart stop working, blood will continue
moving through the blood vessels and circulatory system.
 If the heart muscles stop working, the whole circulatory system
will fail to function correctly.
Plants are a diverse group of
organisms
 Earth = amazing variety of plant
life
 Each is suited to its own
environment
 **All have in common…
 multicellular organisms, their cells
have cell walls, and they capture
energy from sunlight in the process
of photosynthesis
 Examples:
 cold and harsh tundra:
 birch trees - shrubs that can be only
a few centimeters tall
 warm and rich central California:
 giant sequoias grow 90 meters
(about 300 ft) tall
 dry climates: plants tend to have thick
leaves and stems that conserve
moisture
 dense tropical rain forests: tall trees
prevent sunlight from reaching the
forest floor - orchids grow on the
trunks of trees
Plants have three main
types of tissue
 Some plants, like mosses, are
nonvascular
 *We are most familiar with vascular
plants
 Specialized plant cells form three
basic tissues in vascular plants
 dermal tissue for protection and
exchange
 vascular tissue for support and
transport
 ground tissue for photosynthesis,
storage, and support
Dermal Tissue
 Covers a plant - like skin
 Protects the underlying tissue from injury or drying out
 Can be:
 thin and flexible - a blade of grass, or
 rigid and tough - the bark of trees
 At the root ends, dermal tissue is only one cell thick
 allows the roots to absorb water and nutrients from the soil.
 Dermal tissue is thicker in the stems and leaves
Dermal Tissue
 Photosynthesis:
 Through stomata – allow enough CO2 without
drying plant out…to prevent this:
 outermost layer of dermal cells on the leaves and
stems may secrete a waxy coating
 protects against water loss and repels bacteria and
fungi
 Stomata closing in dry weather
 water vapor, oxygen, carbon dioxide
 Salty environment: may have salt glands to get
rid of excess salt
Vascular Tissue
 Provide support and transport
 specialized cells move water, nutrients, and the
products of photosynthesis throughout the plant
 Usually two types of long, tubelike cells:
 xylem: transports water and dissolved
nutrients from the roots up a stem to the
leaves
 like straws bundled together
 Phloem: carries the energy-rich sugars and
carbohydrates down a stem and to the roots
Ground Tissue
 makes up the bulk of a plant
 Found between vascular bundles and dermal tissue in all
parts of the plant
 three main functions:
 contain most of the chloroplasts  most of the
photosynthesis
 Some cells are specialized for storing sugars and starches
 found in stems, roots, fruits, and seeds
 provides support for the plant
Plant tissues work together in
systems
 Most plants have three main organs—roots, stems, and
leaves
 make up two organ systems, the
 root system and shoot system
 Both are subsystems of the vascular system
 Also have reproductive organs and a reproductive system
The Root System
 Anchors plant
 Exchange of materials with
soil
 Stores excess sugar (as
starch)
 Examples:
 Beets, turnips, and carrots
The Shoot System
 Stems and leaves
 Structures for photosynthesis, support,
storage, and the exchange of materials
with the atmosphere
 Stems:
 provide support for plants above ground
 Pathways of the vascular system
 Some plants modify this for food storage
 Potatoes, taro, yams, garlic, and onions
 Leaves: the organs of photosynthesis
 Most chloroplasts are found here (produce
sugar)
System Failure
 Trees: damage by
 Natural: strong winds, lightning, ice storms, and heavy snow can break
limbs…deer can strip bark
 Construction

injure a tree’s trunk or roots
 Healthy trees can repair small wounds
 Weakened trees cannot
 wound becomes an entry place for viruses, fungi, and insects
 Houseplants:
 Roots can outgrow their space


grow around and around into a tangled ball
can no longer absorb enough water for the plant, and the plant weakens
Plants have adapted to their
environments – modified stems
 Adaptations by species to their environments
 Modified Stems
 Ex: Desert plants, cactus:
 Thick, leathery dermal tissue covering their stems – protective
 resist the drying effects of sunlight and wind
 stems are swollen with water
 Roots vs stems:
 stem has joints along its length, called nodes
 shoots and buds can grow from these
 root does not have these nodes
Plants have adapted to their environments – modified stems

Underground Stems:



Potatoes
 have nodes, called eyes, from which new
plants can grow
Iris:
 underground stem called rhizomes
 horizontal stems just below the
surface of the ground
Onion bulbs - underground stem
 the short, central part of the bulb is the
stem
 the layers of flesh around the stem are
modified leaves

Some stems are soft, and some are
hard
 Some plants (ex: trees and shrubs),
have tough, thick stems that do not
die each year



stems keep growing taller and
thicker
develop a type of tough xylem tissue
that is not found in soft stems
This tough tissue is called wood
Plants have adapted to their
environments – modified leaves
 Some plants develop long, thin organs
– tendrils
 Usually modified leaves
 Ex: peas, morning glories, tropical
vines, grape vines,
 grows out from the plant – when it
touches a source of support, the
tendril winds itself around it
 helps the plant grow upward = more
sunlight
 The leaves of the cactus have become
modified into spines, and the
chloroplasts are in the stem
 Spines do not dry out
 protection
Plants have adapted to their
environments – modified roots
 Shallow, broad root system allows the plant to
capture as much water as possible from a quick
rain
 Ex: Cactus
 Some plants have roots that never reach the
ground
 adapted to being exposed to air - aerial roots
 Ex: orchids grow on the trunks of the very tall
trees in rain forests



High enough for photosynthesis
Tree trunk is support
Do not harm tree (commensalism)
 Ex: mistletoe
 roots that grow into the vascular tissue of tree
branches to obtain water and nutrients
 take nutrition from the trees - can harm their
hosts (parasitic)
PLANTS HAVE SEVERAL LEVELS
OF ORGANIZATION
 Comparing Structures During photosynthesis, plants
capture energy from sunlight and convert it to chemical
energy in the form of sugars. Plants often store extra sugars
as starches. When the plant needs energy, the starches are
broken down into sugars and energy is released. Many plant
stems or roots, such as the examples shown below, are
adaptations for storing sugar or starch.
1.
Sugar cane is a commercially valuable crop plant that stores large
amounts of sugar in its stems. Where does the sugar come from?
2.
A sugar beet is a biennial plant. A biennial plant is a plant that takes
two growing seasons to produce seeds. The flowers and seeds of
biennial plants do not form until the second growing season. Explain
an advantage that the storage root offers to sugar beets.
3.
A potato forms sprouts that can become new plants. What is the
energy source for the sprouts?
4.
Plants living in extreme environments sometimes have unusual
adaptations. For example, the desert cactus has a fleshy, green stem
covered with spines instead of leaves. Suggest two purposes of the
unusual cactus stem.
1.
Sugar cane is a commercially valuable crop plant that stores large amounts of sugar in its
stems. Where does the sugar come from?
2.
A sugar beet is a biennial plant. A biennial plant is a plant that takes two growing seasons
to produce seeds. The flowers and seeds of biennial plants do not form until the second
growing season. Explain an advantage that the storage root offers to sugar beets.
3.
A potato forms sprouts that can become new plants. What is the energy source for the
sprouts?
4.
Plants living in extreme environments sometimes have unusual adaptations. For example,
the desert cactus has a fleshy, green stem covered with spines instead of leaves. Suggest
two purposes of the unusual cactus stem.
1. The sugar is produced during photosynthesis.
2. The plant will use the stored sugars in the root as an energy source
for producing flowers and seeds during the second growing season.
3. The starch stored in the potato will provide energy for the growing
sprouts.
4. The cactus stem captures sunlight and performs photosynthesis.
The cactus stem also stores a large amount of water.