Download Science Focus 10 Chapter 9 Review KEY

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MHR • Unit 3 Cycling of Matter in Living Systems
Some proteins cause allergic reactions in people who ingest them. Peanuts and shellfish contain some of the most dangerous proteins for
people without oral tolerance to peanut and shellfish
proteins. Ingestion can result in swelling of the lips
and other parts of the body and even anaphylaxis.
You may want to use Assessment Checklist 24, Using
the Internet for assessment of this activity.
ICT OUTCOMES
This feature could be used to address ICT Outcomes
C.1.4.1, C.7.4.1, or C.7.4.3.
CHECK YOUR UNDERSTANDING ANSWERS
Student Book Page 348
1. (a) light triggers phototropism
(b) gravity triggers gravitropism
(c) touch triggers nastic responses
2. Phototropism causes plants to orient their leaves
toward the light, intercepting more light for photosynthesis. The added photosynthetic capacity helps
the plant generate more energy for growth.
3. Auxin causes the cells of plant stems to grow more
quickly. When the cells on one side of a stem are
exposed to auxin, their rapid growth causes the
stem to curve.
4. Uneven rates of cell growth on opposing sides of a
root or stem cause it to bend.
5. Apply The plant stems would be in the same position as they were at the start of the experiment.
Auxin is the chemical that causes plant stems to
bend toward the light during the phototropic
response. Without auxin, the plants would be
unable to respond to the light source.
6. Thinking Critically Given that there would be no
gravity to stimulate gravitropism in the sunflowers,
and assuming light struck all the plants at the same
angle, the sunflowers would grow horizontally from
the walls, straight downward from the ceiling, and
straight up from the floor.
7. Thinking Critically Phototropism is triggered by
light. The bending of the plant towards light results
from the growth of cells in the side of the stem facing
away from the light. The closing of the Venus’s-flytrap leaf in response to touch is the result of a drop of
turgor pressure in leaf cells, not their growth.
8. Apply One method would be to examine pea plant
cells before and after the winding had occurred, on
both sides of the tendril. Microscopic examination
of the pea plant cells would reveal if there were
changes in their growth patterns.
CHAPTER AT A GLANCE ANSWERS
Student Book Page 349
(a) Single-celled organisms must be able to meet all the
requirements for life. These functions are performed by various organelles within the cell. In
multicellular organisms, specialized cells are
grouped together to perform specific tasks in the
organism. Cells can be organized into tissues,
organs, and systems, all of which have specialized
structures and functions.
(b) Epidermal cells, spongy tissue cells, stomata and
guard cells, palisade tissue cells, vascular tissue cells
(xylem and phloem).
(c) Tissue: clusters of similar cells that share structure
and function, e.g., epidermal tissue cells.
Organs: multiple tissues that are arranged in combination to form organs, e.g., a plant root is an organ.
System: organs and tissues that work together to
perform a complex function, e.g., vascular system in
plants uses roots, stems, and leaves.
(d) Air diffuses through the stomata and into the leaf.
Air circulates in the spaces between spongy and palisade tissue cells, and carbon dioxide diffuses down
the concentration gradient and into fluid around
the cells. Eventually the gas diffuses into the cells
themselves. The carbon dioxide is used during photosynthesis. Oxygen produced during photosynthesis passes out of the cells and into the air spaces
around cells and eventually out of the plant through
the stomata.
(e) The loss of water vapour from plants.
(f) When stomata are open, water vapour also exits
from the leaf.
(g) Guard cells: As water moves into guard cells, the
water pressure inside the cells increase, causing the
cells to swell. As they swell, they push against the
cell wall and open the stomata. As water is lost,
pressure decreases in the guard cells and they get
smaller, also causing the stomata to be smaller.
Plant structure: With reduced water available to a
plant (i.e., when the soil has dried out), all cells in
the plant have reduced turgor pressure, causing the
plant to droop.
Water transport: In roots, fluid is pushed up
because of turgor pressure in the root xylem. This
is called root pressure.
(h) Roots are covered by epidermal cells. At the root
tip, epidermal cells are permeable to water so water
enters the root at the tips by osmosis. Dissolved
minerals are transported into the root cells via active
transport, which keeps the concentration of dissolved solutes in the root cells relatively high. The
growth of tiny root hairs, which are outgrowths of
single epidermal cells, increases the surface area of
Chapter 9 From Cell to Organism: Focus on Plants • MHR
the root, allowing for greater absorption.
(i) Xylem: transports water and dissolved minerals
from the roots to the leaves.
Phloem: carries sugar-rich sap from the leaves
throughout the rest of the plant.
(j) Root pressure pushes fluid up. Transpiration in the
leaves generates a pulling force. Because of the
physical properties of water (cohesion and adhesion), as water evaporates from leaves, the cohesive
force of water causes water to be pulled up the
xylem vessels and into the leaves, replacing the
water that had evaporated.
(k) Cohesion is the tendency of water molecules to
adhere to other water molecules, just like links in a
chain. During transpiration, this property results in
water molecules moving upwards to replace those
that have just evaporated. Adhesion is the tendency
of water molecules to adhere to certain surfaces,
such as the inside of the xylem vessels. Cohesion
and adhesion both fight the properties of gravity,
allowing water to flow upwards against the force of
gravity.
(l) Temperature: Water evaporates more rapidly at
higher temperatures; therefore, transpiration is
greater in warmer environments.
Humidity: The rate at which vapour diffuses out of
the leaves depends on its concentration gradient. In
humid environments, the levels of water vapour in
the air are high. Therefore, the water vapour concentration gradient in the air and inside the leaf is
small. As a result, transpiration is reduced.
Wind: As water vapour diffuses through the stomata, it creates a high-humidity environment just
around the leaf. Winds carry the humid air away
and replace it with dry air. As the water vapour
concentration gradient increases to favour diffusion
out of the leaf, transpiration increases.
Soil water: The ultimate source of water for transpiration is the soil. If there is too little water in the
soil to replace the water lost through transpiration,
the plant begins to dry out. Reduced turgor pressure in the guard cells causes the stomata to close,
and transpiration slows. If there is a loss of turgor
pressure in the stem and leaves, the plants will wilt.
(m) Plant tropisms cause plants to respond (positively or
negatively) to environmental stimuli, such as light,
gravity, and touch.
(n) The Darwins’ concluded that the tip of a seedling
somehow detects light.
(o) Auxin stimulates cell elongation or plant growth.
Auxin plays a role in gravitropism and phototropism.
Prepare Your Own Summary
• Students can use the micrograph of a cross section
through a leaf on student book page 314 as a guide
for their diagrams. Students should label the following leaf cells:
– epidermal cells (protect inner leaf cells)
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– palisade tissue cells (main site of photosynthesis)
– spongy tissue cells (gas exchange and some photosynthesis)
– guard cells (regulate gas exchange)
– xylem tissue cells (transport water and minerals)
– phloem tissue cells (transport sugars)
Students can use Figures 9.11 and 9.13 in the student
book as a reference for drawing cross sections
through a plant stem and root. Diagrams should
include labels for xylem and phloem tissue cells.
•
leaf hair
Water and
minerals enter
leaf through
xylem.
palisade
tissue cells
air space
leaf vein
spongy
tissue cells
Sugar exits
leaf through
phloem.
guard cell
CO2 enters leaf
through stoma.
O2 and H2O
exit leaf
through stoma.
• Students’ diagrams should address the following
points:
– transpiration from the leaves draws water up from
the roots and stem
– turgor pressure keeps non-woody plants upright
and causes stomata to open
– root pressure forces water up from the roots
– as sugars from the leaves are transported into
other plant cells, water follows the sugar by
osmosis
• Students’ diagrams could address any three of the
following environmental effects on transpiration:
increased/decreased humidity (decreased/increased
transpiration); increased air movement (increased
transpiration); increased/decreased soil water content
(increased/decreased transpiration);
increased/decreased temperature
(increased/decreased transpiration);
increased/decreased sunlight (increased/decreased
transpiration).
CHAPTER 9 REVIEW ANSWERS
Student Book Pages 350–351
Key Terms
See glossary in the student book.
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MHR • Unit 3 Cycling of Matter in Living Systems
Understanding Key Concepts
1. (a) a xylem vessel is a tissue
(b) a leaf is an organ
(c) a root hair is a cell
(d) a sheet of epidermal cell is a tissue
(e) a stem is an organ
2. The stomata permit gas exchange across the leaf
surface. Guard cells surround each stoma and regulate the size of the stomatal opening.
3. I. cuticle
II. epidermis
III. palisade tissue cells
IV. spongy tissue cells
V. vascular tissue (xylem and phloem)
VI. stomata and guard cells
4. Gas exchange on leaves occurs through stomata.
Lenticels occur in the bark of woody plants, which
have layers of dead cork cells and waxy substances
that prevent gas exchange with the environment.
(Plants that are not woody will have some gas
exchange occurring at the surface of stems and
roots.) Lenticels allow some gas exchange between
the plant and the environment.
5. (a) In response to hot, dry weather, the guard cells
lose their turgidity, which closes the stomata.
Water vapour is, therefore, unable to exit the
leaves.
(b) In general, the guard cells are turgid during the
day. An opening (a stoma) results between each
pair of swollen guard cells. Carbon dioxide, oxygen, and water vapour can pass in and out of the
leaf through the stomata. At night, water flows
out of the guard cells, causing them to lose their
turgidity and close the stomata.
6. (a) palisade tissue cells – site of photosynthesis
(b) guard cells – control the opening and closing of
the stomata
(c) xylem vessels – transport water throughout the
plant
(d) leaf epidermal cells – protect the inner tissues of
the leaf
(e) phloem vessels – transport sugars throughout
the plant
(f) root hair cells – take up water from the soil
7. Plant responses to stimuli include gravitropism,
phototropism, sleep movements, and nastic
response
8. (a) To perform photosynthesis, plants require light
energy, carbon dioxide, and water. Sunlight (or
an artificial light) reaching the photosynthetic
cells of the leaf is trapped by chlorophyll in the
chloroplasts. The light energy is used to power
the reactions that make sugars. Water travels
from the roots to the leaves through the xylem
vessels. Carbon dioxide enters the leaf through
open stomata, and diffuses into the leaf cells.
(b) Photosynthesis results in the production of oxygen and carbohydrates.
Developing Skills
9. Students’ drawings will vary but they should show
the following information:
• Water from the soil enters the xylem in the root.
This happens because root cells actively transport minerals into the xylem. This increases the
mineral concentration in the xylem sap and sets
up a concentration gradient that results in water
diffusing into the root xylem by osmosis. Water
flows in and creates root pressure in the xylem
vessels, which pushes the water column up.
• Tension created by transpiration at the leaves
creates a force that pulls the water in thy xylem
in the roots and stems upward to the leaves.
• The water column is held together by cohesion
and adhesion of water molecules to the xylem
cell wall keeps the water column in place.
water vapour
lost through
transpiration
sugars created
in leaves during
photosynthesis
and transported
through the plant
in the phloem
water and
minerals flow
into roots
and through
the plant
in the xylem
10. (a) Line B best represents the control.
(b) Line C best represents the plant in the bag.
(c) Line A best represents the plant placed in front
of the fan.
(d) The environment of a plant affects its water loss.
Moving air around the leaves increases the rate
of transpiration.
11. Province D likely has the least rainfall, and province
A likely has the greatest rainfall. The number of
stomata would be expected to increase with increasing rainfall. Because water is lost through stomata,
plants in arid regions would tend to have fewer
stomata.
Problem Solving/Applying
12. A flower is an organ. It is composed of tissues,
which are in turn composed of specialized cells.
Differences in the tissue structures are observable at
the macroscopic level. For example, petals look and
feel different from sepals. A flower could be dissected and examined microscopically to show that the
cells making up the different flower tissues also
Chapter 9 From Cell to Organism: Focus on Plants • MHR
have different structures. These structures may provide clues about the cells’ specialized functions.
13. (a) Cells that carry out photosynthesis contain
chloroplasts and are usually green. (Some plants
have other pigments that can mask the green of
chlorophyll.)
(b) Generally, the green parts of plants are capable
of photosynthesis although leaves are specialized
for this process.
14. Students should design an experiment where plants
(or seeds) are exposed to different levels of light and
are oriented in different ways. The experiment
could have four sprouted seeds (kept in a plastic bag
with a moist paper towel), which are kept under the
following conditions: (1) seedlings in direct light,
initially oriented with roots pointing straight down
and stems pointing directly up; (2) seedlings in
direct light, initially oriented with roots pointing up
and stems pointing straight down; (3) seedlings in a
dark box with one opening for light, initially oriented with roots pointing straight down and stems
pointing directly up; (4) seedlings in a dark box
with one opening for light, initially oriented with
roots pointing directly up and stems pointing
straight down. All of the seeds must be treated in
the same way, except for the above conditions.
15. Sugar, minerals, and other nutrients are pumped
into leaf phloem by active transport. As the sugar
concentration increases in the phloem cells, water
follows by osmosis. Phloem sap then flows down a
pressure gradient, from leaves to roots. Phloem sap
is forced through pores in the phloem cell walls and
flows into neighbouring phloem cells, where the
pressure is lower.
Critical Thinking
16. When plants are actively photosynthesizing, they
transpire as water escapes from the stomata. When
this happens, the plant produces a lot of food and
grows well; however, there is also the danger of
dehydration. As the plant begins to lose water,
turgidity in the guard cells decreases and the stomata begin to close; thus photosynthesis decreases as
well.
17. Roots are highly permeable, particularly at their
tips, as they need to actively absorb water to supply
the rest of the plant. Leaves are covered in a waxy
cuticle to limit the amount of water lost through
the leaves. Water vapour can only exit the leaves
through the stomata.
18. An amoeba has a greater chance of survival, as it is a
unicellular organism and contains all of the
organelles it requires for carrying out life functions.
A single cell removed from a multicellular animal
would not survive because by itself it cannot carry
out all of the functions required for life.
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19. Carbon dioxide is used within the cells of the leaf
during photosynthesis.
20. As most water loss in plants occurs through the
leaves, plants with reduced leaf area lose less water.
This is a benefit to plants that are adapted to arid
environments, because they conserve what little
water is available to the plant. However, the
reduced leaf area also reduces the amount of photosynthesis possible. As a result, these plants often
grow slowly.
This item encourages students to synthesize the knowledge they have
learned from Chapters 7, 8, and 9. Encourage students to make connections between cell structures
and functions and the functioning of multicellular
organisms.
UNIT 3 ASK AN EXPERT
Student Book Page 352–353
SCIENCE BACKGROUND
• Dr. Miller’s source for stem cells from adult skin is
much less controversial than using fetal stem cells.
Stem cells from adult skin can produce a number
of different cell types, including the type of neural
cells needed to potentially help patients recover
from spinal cord injury or Parkinson’s disease.
• Dr. Miller is a co-author of the paper, “Isolation
of Multipotent Adult Stem Cells from the Dermis
of Mammalian Skin” (by J.G. Toma, M. Akhavan,
K.J.L. Fernandes, F. Barnabé-Heider, A. Sadikot,
D.R. Kaplan, and F.D. Miller), which was published in the scientific journal, Nature Cell Biology.
The paper can be viewed on line at
http://www.nature.com/ncb/future_issues/.
• Dr. Miller and her colleagues isolated stem cells
from the skin of adult rodents and their research
showed that the cells would proliferate and differentiate in culture to produce different cell types,
including neurons, glial cells, smooth muscle cells,
and fat cells. The research team harvested stem
cells from the skin of juvenile and adult rodents.
Human studies have indicated that similar cells are
present in adult human skin.
• Dr. Miller’s work is important because it may
mean that stem cells harvested from a patient
could then be used to help treat the same individual. This would minimize complications that are
often seen in donor transplantations where the
patient’s body rejects the donor’s cells.