Download Biology Notes-Teacher (chapters 7, 8, 9)

Science Focus 10
Unit 3
Cycling of Matter in Living Systems
p.254-359
In this unit we will explore:
 microscope technology
 the cell theory
 cellular structures and
function
 cellular transport
 The specialized cells of
multicellular organisms
 plant cell mechanisms (gas exchange, water transport)
Chapter 7: The Basis of Life
p.258
7.1 Life From Life
The development of the theories of the origin of living
matter:
A. Aristotle (384 BC – 322 BC) – a Greek philosopher
whose theory of abiogenesis or spontaneous generation
was accepted for over 2000 years.
Abiogenesis – living things could arise from non-living
matter
Examples:
a) eels came from the slime in river mud
b) rats came from garbage or dirty laundry
c) maggots came from rotting material
d) mice came from a pile of wheat husks
e) frogs came from mud
Aristotle created his theories on the origin of life based
on his many observations, however, he did not conduct
any scientific experiments to test his ideas.
Q: Choose one of the above examples and describe
how to refute the idea using scientific
experimentation.
B. Francesco Redi (1626 – 1697) – Italian physician who
used controlled scientific experiments to refute the
theory of spontaneous generation
- Redi’s experiment: see figure 7.2 p.259
Jar 1: meat, left uncovered -> maggots appeared
Jar 2: meat, covered in cloth -> no maggots
appeared
Maggots appeared in Jar 1 because _____________
________________________.
NOTE: Within a few years, the discovery of
microscopic single celled organisms, renewed the
idea of abiogenesis. People believed a “vital force”
or “active principle” in the air created these microorganisms.
C. Louis Pasteur (1822 – 1895) – French scientist who
finally settled the continued debate of the theory of
abiogenesis.
Pasteur’s experiment:
< --------- airborne
_________
settled here
a) a swan-neck glass flask (figure 7.3) full of nutrientrich broth was boiled to force out air and kill any
microbes
b) flask was cooled and broth remained clear even
after many days because any microbes entering,
settled with gravity in the neck of the flask.
c) When flask was tipped so broth reached neck, soon
broth became cloudy. Explain: ________________
_______________________________________
As a result: The accepted theory became biogenesis
– living things could only arise from other living
organisms (suggested by Vichow in 1858)
*WORD
Biogenesis - Latin root “bio” = of living
CONNECT
things and “genesis” = origin
Discovering Cells
Prior to seeing bacteria, the common assumption was
that curses or supernatural spirits caused diseases!
The invention of the microscope allowed scientists
to magnify objects and examine the microscopic
world, and as a result, cells were discovered.
Cell – the smallest functional unit of life found
in all living organisms
See cells Figure 7.4
p.261
TRIVIA
(p.265) * The largest cells are egg cells (largest:
ostrich eggs which are 1.2 kg, 14 cm wide)
* The longest cells are nerve cells (longest is the sciatic
nerve that runs down your leg)
Developing the Cell Theory
- the cell theory explains and defines the boundary
between the living and non-living and is integral to
our understanding of life on Earth
The molecules that are food for a cell and the
organic molecules that make up a cell are non-living,
yet the cell is ALIVE!
A. Robert Hooke (1635 – 1703) – looked at cork with a
compound light microscope (30X magnification) and was
the first to see and name “cells”.
B. Antony van Leeuwenhoek (1632 – 1723) – Dutch linen
merchant who first described single-celled
microorganisms. He used a single lens microscope
(500X magnification) to study blood cells, pond water
& teeth scrapings
- called his sightings “animalcules”
C. Matthias Schleiden (1804 – 1881) and Theodor
Schwann (1810 – 1882) – German scientists who studied
cells in hundreds of plants and whose research
contributed to the cell theory, stating that “all
organisms are made of cells ”
(NOTE: they still believed that cells were created by
spontaneous generation.)
D. Rudolf Vichow – German physician who made
microscopic observations of cells dividing and
completed the cell theory still accepted today.
The Cell Theory
1. All organisms are composed of one or more cells.
2. The cell is the smallest functional unit of life.
3. All cells are produced from other cells.
Do Check Your Understanding p.265 #1, 2, 3, 6, 9
Do 7.1 Review Worksheet
7.1 Quiz on __________________
Science Focus 10
Unit 3 Chapter 7
p. 266
7.2 Cells and Technology
A. Light Microscopes – use to view objects illuminated by
visible light
1. Simple microscope – used only one lens (similar to a
magnifying glass)
2. Compound microscope – uses two or
more lenses placed one on top of the
other
- first created on 1595 by Zacharias
Janssen, a Dutch maker of reading
glasses
- commonly has one lens in the
eyepiece and one in each objective
- can magnify as much as 2000 X
B. Electron microscope – specimens are
illuminated with a beam of electrons instead of a beam
of light
- magnifies up to 1.2 million times
electron micrograph – the photograph of the image
produced by an electron microscope
a) TEM – transmission electron microscope
- built in 1931 in Germany
- specimens are thinly sliced, then
placed under a vacuum to
remove moisture & particles.
Electrons are then transmitted
through the specimen to view 2D internal structures & details.
b) SEM – scanning electron microscope
- designed in 1930’s in Germany
- a beam of electrons sweeps over
an object to create a 3-D image
(only the surface can be detected)
c) CLSM – confocal laser scanning microscope
- invented in the 1960’s
- a laser beam directed at numerous planes creating a
series of 2-D images or “optical slices”
- computer software then “stitches” images
together
d) STM – scanning tunnelling microscope
- invented in the mid-1900’s
- enables scientists to obtain an image of atoms on an
object’s surface (eg. DNA molecule)
- a fine metal probe emits electrons towards
specimen’s surface and information is
interpreted by a computer producing a 3-D
image
Do: Microscope Review Worksheet
Science Focus 10
p. 272
7.2 A Molecular World
Genes – sections of DNA that direct the
activities of our cells
- changes in the gene can cause
improper cell function
eg. Sickle cell anemia
DNA – carries all genetic information of the organism, coiled to
form chromosomes, found in the nucleus
of every cell
- constructed of 4 bases:
Adenine pairs with Thymine
Cytosine pairs with Guanine
- the order of thousands of pairs of bases make up
each organism’s unique genetic code
Q: Fill in the missing bases on this piece of DNA.
Gene sequencing – mapping the order of all of a gene’s bases
Human Genome Project (HGP) – an international project
to sequence all 30,000 to 40,000 human genes
- sequence information can be used to diagnose
and treat genetic disorders
eg. gene therapy – human gene is “corrected” to
help cure a disorder or cancer
Demo: Extract DNA from pea soup
Cancer - most cancers are caused by gene damage,
some of which create mutations
- cancerous cells divide indefinitely and form
layers upon layers to form a tumor
Mutations – changes in the base sequence of a gene
- some mutations may cause a cancer where
cells
grow and divide uncontrollably forming a tumor
(SEE Fig. 7.15, p. 274)
Living or Not?
Virus – non-cellular structure made of a piece of genetic
material enclosed in a protein coat
- in order to reproduce, a virus must infect a cell
and use this host cell’s organelles (cell parts)
Prion – a protein that can convert into a harmful
particle which can reproduce in living tissue
- cause BSE (bovine spongiform encephalopathy) or “mad
cow disease”
Culturing Cells
Cell culture – isolated cells are given nutrients and their
growth and division are studied
Cell lines – the generations of cells produced from a
culture; can be grown indefinitely in a lab
Eg. HeLa cells
Stem cells – “blank slate” cells that divide to produce all other
types of specialized cells
- found in:
a) one week old embryos (aborted fetuses)
b) adult bone marrow (these form different types of
blood cells)
c) unused embryos from in vitro fertilization
treatments
d) cord blood (from umbilical cord after birth)
e) genetically engineered from human egg cells
- mature into specialized cells which can only reproduce to
form more of their own kind
(liver cells -> liver cells)
- scientists hope to grow tissues and organs for
transplants and to cure diseases using stem cells (eg.
Parkinson’s, Alzeimer’s, diabetes & spinal cord injuries)
Rudolf Virchow – the first scientist to link illnesses to
malfunctioning cells
Science Focus 10 Unit 3
What’s in a Cell?
p.277
7.3
Cells – sustain life by performing the tasks essential for
the cell to function:
a) obtain food & energy
b) convert energy (eg. photosynthesis)
c) construct & maintain the molecules making up the
cell structure
d) carry out chemical reactions
e) eliminate wastes
f) reproducing
Organelles – internal cell parts that carry out specific
functions
Prokaryotes – one-celled organisms lacking a membranebound nucleus & organelles (do contain
ribosomes)
- are the most abundant cells on Earth
- eg. bacteria and algae
Eukaryotes – cells with a more complex internal
structure including a membranebound nucleus & organelles
- eg. most plant and animal cells
In Latin:
“karyon” means nucleus
“pro” means before
“eu” means true
therefore: prokaryote means before nucleus.
eukaryote means true nucleus.
Cell Organelles
1. Cell membrane (plasma membrane)
- a protective barrier for the cell allowing
transport of needed materials in and out
- consists of protein molecules imbedded in a lipid
bilayer
2. Vesicles – small membrane sacs pinched off of the cell
membrane
- store or transport materials in and out of the cell
3. Cytoplasm – jelly-like cell contents
- 70% water with suspended
organelles
4. Nucleus – contains DNA, the genetic material of the
cells (genes)
- directs all cellular activities
- materials leave the nucleus through nuclear pores
in the nuclear membrane (or nuclear envelope)
5. Nucleolus – region of the nucleus where ribosomes are
produced
6. Ribosomes – dense granules that may be found
attached to rough ER or
free in the cytoplasm
- are the site of protein synthesis – where amino
acids are assembled into proteins according to the
information stored in the DNA
7. Endoplasmic reticulum (ER) – network of tubes
branching from the
nucleus through which materials can be transported
a) rough ER – has ribosomes on the surface
b) smooth ER – has no ribosomes, produces and
packages lipids
8. Lysosomes – vesicles containing digestive enzymes
- function to break down food particles, kill
bacteria & destroy old or damaged cell parts
9. Golgi apparatus – flat disc-shaped sacs that sort,
modify & replace molecules sent from the ER; the
needed materials are pinched off into vesicles and
sent to other parts of the cell or to the cell membrane
for transport out of the cell
- lysosomes are produced here
10. Mitochondria – rod-shaped organelle with folded
inner membranes
- site of cellular respiration in which chemical
energy stored in sugars is converted into useable
energy for the cell (ATP)
Cellular Respiration
C6H12O6 + 6O2  6CO2 + 6H2O + energy
11. Centrioles – cylindrical structures located just
outside the nucleus of animal cells
- during cell division, centrioles help direct the
separation of genetic material
12. Vacuoles – balloon-like vesicles that store water,
food, minerals, or wastes
- animal vacuoles are smaller; plants usually have
one large central vacuole
13. Cell wall – rigid structure that protects
and provides shape and support to plant,
fungi & some bacterial cells
- composed of cellulose, a complex
carbohydrate (a.k.a. fibre or roughage in our
diet)
14. Chloroplasts – found only in green plants
- contain stacks of flattened discs containing the
green pigment chlorophyll
- are the site of photosynthesis in which the Sun’s
energy is converted into chemical energy (sugars)
Photosynthesis
sunlight
6CO2 + 6H2O ----------- > C6H12O6 + 6O2
chlorophyll
Do: p.284 Check Your Understanding
# 2, 3, 4, 6, 7, 8
Do: p.286 CH. 7 Review
# 4, 5, 7, 9, 11, 12, 15
Science Focus 10
Unit 3
8.1 Membrane Properties
p. 290
The activities of a living cell depend on the ability of its
membrane to:
1. transport raw materials into the cell (and out of)
2. transport manufactured products and wastes out of
the cell
3. prevent unwanted matter from entering the cell
4. prevent the escape of matter needed to perform
cellular functions
Cell Membrane Structure
1. phospholipid bilayer – each phospholipid molecule has a
head that is hydrophilic (water-loving) and two tails
that are hydrophobic (water-fearing)
2. proteins – are embedded throughout the membrane
serving the following functions:
a) moving substances across the membrane
b) carrying out chemical reactions (they act as
enzymes)
c) some have “marker” molecules (carbohydrate chains)
on their surface allowing cells to recognize each
other
d) allow messenger molecules (such as hormones) to
attach
e) assist in cell-to-cell communication and control of
cell functions
Protein position within a membrane:
1. Peripheral proteins – are partially embedded in the
inside or outside surface of the membrane
2. Integral proteins – extend through the entire bilayer
and project from both surfaces
The Fluid-Mosaic Model
Cell membrane molecules are in constant motion (drifting
past each other) resulting in:
a) membrane flexibility
b) cell’s ability to change shape
Do BLM 8-1 Cell Membranes
Cell Membrane Function
1. A Biological Barrier
- a cell membrane prevents many materials from
entering the cell. Name 6:
- salts
- atoms
- viruses
- sugar
- ions
- bacteria
- proteins
- most organelles are surrounded by membranes with
the same structure as a cell membrane
Apoptosis – when the lysosome bursts and
releases it’s digestive enzymes into the
cell, resulting in cell destruction
2. A Selective Filter
Cell membranes are semi-permeable, allowing some
materials to cross, while excluding others. They can
select
a) by particle size
- small enough to enter membrane - O2, H2O
- too large to cross - sugar
b) particular materials to transport across (they
bind to chemicals based on their size, shape or
charge)
p. 296 Cool Tools – Describe the freezefracture method and how it provided evidence
for the fluid mosaic model.
[specimens are frozen in liquid nitrogen
then cracked with a cold knife. The lipid
bilayer can be separated, exposing the
membrane proteins. Can coat with platinum
and examine with electron microscope]
Do Check Your Understanding p. 296 #1-6
Science Focus 10 Unit 3
8.2 Transport Across Cell Membranes
Selective Transport – the movement of only certain
substances across the cell membrane
Particle Model of Matter – all matter is
made of tiny particles
Brownian Motion – in a liquid or gas, particles are in
constant, random motion
p.297 Find Out Activity – Brownian Motion
Concentration Gradient – the difference in concentration
between two areas for any given molecule produces a
gradient or path of movement in which molecules move
toward areas where the concentration of particles is
lower
- molecules move down a concentration gradient
Equilibrium – a state at which molecules are evenly
distributed (the concentration is equal throughout the
medium)
- molecules continue moving but equilibrium is
maintained
Types of Transport Across Membranes
A. Passive Transport – movement across cell membranes
without an input of energy
Q. Name 2 reasons molecules move.
1. Brownian Motion
1. Concentration gradients
Three Types of Passive Transport
1. Diffusion – the net movement of particles from an area
of high concentration to an area of low concentration
- no energy is expended
- in a cell, very small particles can cross the cell
membrane by moving between the phospholipid
molecules
Q: Why does oxygen diffusing into the cell never reach equilibrium?
A: Your cells continually consume oxygen for cellular respiration,
making the concentration inside always lower than the outside
Q: Describe the concentration gradient of carbon dioxide.
A: Higher concentrations in the cell so net movement is
out of the cell.
Do BLM 8-3 Particle Model of Matter and Diffusion
Demo: p.298 The Amount of Water in Solutions
2. Osmosis – the diffusion of water molecules
across a membrane (water molecules move
from where they are more highly
concentrated to where they are less
concentrated)
Solutions are described in terms of their
concentration relative to another solution
a)
Hypotonic solution – has a lower concentration of
solute compared to inside the cell
- The solution is therefore more concentrated inside the
cell and water will move into the cell. The cell will
explode
b)
Hypertonic solution – has a higher concentration
of solute compared to the inside of the cell
- The solution is therefore less concentrated inside the
cell and water will leave the cell. The cell will shrivel
up
c)
Isotonic solution – has the same solute
concentration on both sides of the cell membrane.
Equilibrium has been reached. EQUAL FLOW of
water into and out of the cell
Q: a) What happens when a cell is placed into
distilled water?
A: The cell is hypertonic and water moves into the
cell & the cell may burst
Q: b) What is turgor pressure?
A: The cell wall of a plant resists the pressure of a
water-filled vacuole keeping the plant firm
Q: c) What happens when a cell is placed into
strong salt water?
A: The solution is hypertonic and water leaves the
cell. The cell shrinks and may die (plasmolysis)
Q: d) What is plasmolysis?
A: Loss of water in a plant cell resulting in WILTING
Q: e) Why would drinking saltwater pose a
problem?
A: Hypertonic solution outside cells would cause cells
to lose water, shrink and die (dehydration)
Do BLM 8-4 Concentration Gradients
3. Facilitated Diffusion – diffusion of molecules across
the cell membrane by way of transport proteins.
- necessary for glucose, ions, and other substances
that cannot cross the membrane by simple diffusion
Transport proteins have 3-D shapes that make them
highly selective, recognizing atoms or molecules by shape,
size or charge.
Two types of transport proteins:
a)
carrier proteins – facilitate the diffusion of glucose
across the cell membrane
Q: Explain how glucose enters the cell.
A: Glucose fits into a groove on the carrier, the protein’s
shape changes, and glucose is released on the inside of
the cell
b)
channel proteins – have tunnel-like pores filled with
water that allow charged ions in and out of the cell
B. Active Transport – the movement of molecules and
ions against the concentration gradient which requires
ATP energy and carrier proteins to pump these
molecules from an area of low solute concentration to an
area of high solute concentration.
- used to accumulate nutrients, or remove toxic
materials or wastes
Most cells use 40% of their energy
on active transport; kidney cells use
90% of their energy on using active
transport to filter wastes out of
your blood!
C. Bulk Transport – the use of vesicles to facilitate
movement of substances that are too large to enter
or exit the cell via transport proteins
Two types:
1. ENDOCYTOSIS – the cell membrane forms a pocket
around the material to be transported, then either
pinches off as a vesicle or a vacuole.
Q: Differentiate between a vacuole & vesicle.
A: Vesicle transports contents; vacuole stores the ingested material
Two types of Endocytosis:
a)
phagocytosis - when cells “eat” by
taking in large particles or other cells
Q: What happens after a new vesicle enters the cytoplasm of a cell?
A: It fuses with a lysosome and the enzymes would digest the
material
b)
pinocytosis – when cells “drink” by taking in droplets
of fluid
Receptor – mediated endocytosis – receptors, like antennae,
detect specific compounds or cells and bind with them, triggering
endocytosis.
Q: Give 2 examples of molecules entering by R.M.E.
A. Cholesterol & HIV
2. EXOCYTOSIS – the reverse of endocytosis, whereby
the membrane of vesicles or vacuoles fuses with the
cell membrane and the stored contents are expelled
from the cell.
Q: Give 2 examples of expelled materials.
A: Wastes, enzymes, hormones
Do BLM 8-6 Types of Transport Across Cell Membranes
Do BLM 8-7 The Role of Cell Membranes in Endocytosis
and Exocytosis
Membranes at Work
1. Water Purification
Reverse osmosis – uses pressure to force
contaminated water through a
membrane with fine pores that will not
allow bacteria, salts, and other
dissolved molecules through, resulting in
water with fewer impurities
2. Kidney Dialysis - filters toxic wastes that accumulate
in the blood while retaining necessary proteins,
glucose, amino acids & ions
- the patient’s blood is pumped through dialysis tubing,
a synthetic, semi-permeable membrane. When
immersed into a salt solution, needed salts don’t
diffuse, but wastes, which are hypertonic to the
dyalysate, diffuse out of the blood.
3. Controlled Delivery of Medications –
a) medication can be placed in a flat
transdermal patch that sticks to the
skin. A semi-permeable membrane
lining the inner surface allows drugs to diffuse
out of the patch at a slow, constant rate.
Q: Give 4 examples of medications available in patches.
A:
- nicotine (to quit smoking)
- motion sickness drugs
- pain reducers
b)
- hormones for imbalances
- contraceptive hormones
- weight-loss
Liposomes – artificial vesicles that can safely
transport medications from one part of the body
to another
Two examples:
1)
2)
used to transport anti-cancer medications to
tumours in cancer patients
liposomes, coated with the gene needed
to cure cystic fibrosis, are sprayed
into the patient’s nostrils
Do Check Your Understanding p.307 #2Do 8.2 Review Worksheet
Science Focus 10 Unit 3
8.3 Cell Size and Function
- Particles entering the cell reach more to other areas
of the cell by diffusion, due to a differing
concentration gradient in the two areas.
Q. Compare rate of diffusion across a cell membrane
with diffusion within a cell.
A. Concentration gradient within a cell is lower so
diffusion in a cell is slow and inefficient.
Two reasons an amoeba could not function were it humansized:
1. substances could diffuse through the cell
membrane in less than a second, but would
take more than a week to reach the
centre of the cell.
2. It would have a very low surface area – to – volume
ratio making it difficult for adequate amounts of
oxygen and nutrients to diffuse in
Q. What do scientists believe was the reason that the
Paleozoic Era could sustain the existance of giant
insects?
A. The air was believed to be 35% oxygen
(now 21%) making the concentration
gradient of oxygen much steeper and O2
was able to efficiently move through
longer tracheoles.
Do p.309 Charting Cell Size
The
Importance of Surface Area – to – Volume Ratio
***As a cell grows, volume increases faster than
surface area.
Eg. If cell size is doubled, it would require eight
times more nutrients and produce eight times more
waste, but surface area would only have increased four
times.
Result:
1. not enough surface area for oxygen,
nutrients, and waste exchange
2. cell would starve OR
3. cell would be poisoned from a buildup of
waste products
A cell with a surface area-to-volume ratio of 30:6 has to
acquire 3 times the nutrients of a cell with a ratio of
10:2.
Q. Cell ratio of 18:6 requires ___ times the
nutrients as a cell with a ratio of 3:1.
A. 6
The human body has more than 10 trillion
cells. If 1000 average-sized cells were lined
up, they would total less than 2 cm in length.
Cell Shape and Surface Area
Certain cell shapes increase surface area-to-volume
ratio’s
Q. Complete the chart with two types of cells whose
shape produces a large surface area.
Name of Cell
Sketch
Function of Cell
1.
2.
From One Cell to Many Cells
How do some organisms function at enormous sizes?
A. They are multicellular and grow by adding more cells
instead of simply growing larger cells,
Result: Rapid diffusion within cells exists
Cell Specialization – in multicellular organisms, cells are
organized into tissues that do specific jobs.
Q. Give an example of cell specialization in your
body.
A. - lungs – gas exchange
- heart & blood vessels – transport of O2, nutrients &
wastes
- kidneys – water regulation and excretion of wastes
- digestive system – nutrient digestion and absorption
- etc.
Do p.314 Check Your Understanding Q. 1 – 7
Science Focus 10
Unit 3
p.318
Chapter 9: From Cell to Organism:
Focus on Plants
9.1 Specialized and Organized
Q. What functions need to be carried out by the leaf of a plant?
A.
gas exchange
leaf
release water
protect leaf cells
photosynthesis
transport water & nutrients through
In single-celled organisms, one cell performs all the functions of
life.
In multi-cellular organisms, groups of similar cells (called tissues)
are specialized to perform specific tasks.
Q. Name 4 specialized cells in the human body.
A. cells of the intestinal lining
muscle cells
nerve cells
skin cells
Cell Specialization in Leaves
Photosynthesis occurs in the chloroplasts of plant cells
6CO2(g) + 6H2O(l)
light
------------ C6H12O6(s) + 6O2(g)
chlorophyll
Cellular respiration occurs in the mitochondria of plant and
animal cells.
C6H12O6(s) + 6O2(g) --------- 6CO2(g) + 6H2O(l)
Cells of the Leaf
Do BLM 9-1 Photosynthesis and Respiration in Plants
1. Epidermal Cells – make up the epidermis
a) Description - flat, single cell layer
covering the upper and lower surfaces of the leaf
- transparent, which allows solar energy to pass through to
cells beneath
- a waxy cuticle coats the cells to prevent evaporation of
water
b) Function – to protect the leaf, therefore do not contain
chloroplasts
2. Palisade Tissue Cells
a) Description – long and narrow (columnar) cells packed
closely together lying just below the epidermis
b) Function – major photosynthesis, therefore packed with
chloroplasts
3. Spongy Tissue Cells
a) Description – round, loosely packed cells found just below
palisade layer; contain chloroplasts
b) Function – gas and water exchange, minor photosynthesis
4. Stomata and Guard Cells
a) Description – stomata (singular-stoma) are tiny openings on
the underside of a leaf
- each stoma is controlled by 2 guard cells
b) Function – stomata allow exchange of carbon dioxide,
oxygen and water vapor
5. Vascular Tissue Cells
a) Description – a series of tubes or leaf veins called phloem
and xylem, which are arranged together in vascular bundles
b) Function –
XYLEM – carries water and minerals from roots to
leaves
PHLOEM – carries sugars made by the leaves to other
parts of the plant
Q. Do an analogy of leaf tissues and human body
tissues
A. skin = epidermis; circulation system = vascular tissue;
lungs = stomata
Do BLM 9-2 Cell Specialization in Leaves
Do F.O. Activity Turn Over a New Leaf p. 322
Cell, Tissue, Organ, System
Q. Name 3 advantages multicellular organisms have
over single-celled organisms.
A. – larger size
- a variety of specialized cells
- an ability to thrive in a broader range of environments
Multicellularity, however, requires a high degree of
organization of the numerous cells in order to perform
their functions efficiently. (The human body contains
approx. 100 trillion cells.)
Levels of Organization
Cells – basic unit of organization
eg. Human – stomach cell
Plant - phloem cell
Tissues – many cells with the same structure and functions
clustered together
eg. Human – muscle tissue of stomach
Plant – epidermal tissue
Organs – multiple tissues working together to perform a specific
function
eg. Human – stomach
Plant – leaf
Systems – organs working together to perform a complex
function
eg. Human – digestive system
Plant – vascular system
Science Focus 10
Unit 3 9.2
Gas Exchange in Plants
During cellular respiration in animal and plant cells, exhaled air
contains lower O2 levels and higher CO2 level than inhaled air.
During photosynthesis, plants consume CO2 and H2O and produce
O2.
Leaves and Lenticles
Leaves
Gases diffuse into stomata of plant leaves and
move through air spaces between the spongy and
palisade tissue cells. CO2 dissolves into the
watery film around the cells and diffuses into the
cells of the leaf where chloroplasts use the CO2 for
photosynthesis. O2 produced diffuses out of the
leaf cells and leaves through the
stomata.
Roots and Stems
- some gas exchange occurs in surface cells
- in woody plants, layers of dead cork cells and waxy
substances prevent gas exchange
- Lenticels, which appear as slashes on stems of trees and
herbaceous plants, are natural pores through which gas
exchange can occur.
Investigation 9-A Carbon Dioxide Consumption by Cabomba p.326
Gas Exchange Is Tied to Water Loss
Q. How do plants carry out evaporative cooling?
A. By transpiration.
Q. How can this process function as a survival mechanism for plants?
A. Can cool leaf 10-15C and prevent heat damage.
Transpiration is the evaporation of water
from leaves of plants. This can be as much as
99% of the water absorbed by the roots.
TRIVIA: A single corn plant can lose between 135 L and
200 L of water through transpiration in one growing season.
Transpiration and gas exchange are controlled by the shape
of guard cells which open stomata to allow CO2 in and O2 and
H2O out. More photosynthesis occurs when stomata are open.
OPENED STOMATA – occurs when high water pressure, called
turgor pressure, causes water to move into the guard cells by
osmosis. The guard cells swell and the stomata open, allowing
transpiration. (Occurs most during the day). (Or on: Sunny
days, humid days, warm temperatures)
CLOSED STOMATA – occurs when the amount of water in the
guard cells decreases and they shrink and the stomata close.
(Occurs most during the night, except in desert plants where
stomata only open at night due to dry conditions).
WILTED PLANTS – result from reduced turgor pressure as a
result of water loss.
p.330 Find Out Activity Open and Shut
Do BLM 9-3 Gas and Water Movement In Leaves
Do Check Your Understanding p.330 #1-4
Science Focus 10 Unit C 9.3 Water Transport in Plants
p.331
Xylem Vessels and Phloem Vessels
Xylem and phloem make up the vascular tissue of plants,
transporting water, minerals, and sugars through a series of
interconnected tubes through the leaves, stems and roots.
XYLEM – transports water and dissolved minerals from soil to
leaves.
- in mature plants, most xylem cells are dead, only
cell walls remain, forming hollow tubes called xylem
vessels.
Detailed Structure of Xylem Vessels – consists of long hollow
cells called tracheids or vessel elements, which are joined by
small pits, allowing water to flow through.
PHLOEM – transports sugars produced during photosynthesis
from leaves to roots. Cylindrical cells joined end to
end form phloem vessels, which are living cells with
porous cell walls. Sugary sap flows down the
phloem vessels and passes through these pores.
Detailed Structure of Phloem Vessels – consists of sieve tubes,
cylindrical cells joined by a sieve plate. A companion cell lies
alongside each sieve tube cell, offering support because the sieve
tube cell lacks many organelles.
Water Uptake in Roots
Roots are covered with epidermal tissue which is permeable to
water only at the root tip. Water enters the root tips by osmosis
until it reaches the xylem.
Root hairs – increase surface area for
absorbing water & dissolved minerals.
- are each an outgrowth of a single
epidermal cell
WOW! The total surface area of a plant’s roots may be
up to 50X greater than the surface area of its leaves
- minerals enter the root by facilitated diffusion or active transport
- the solution of water & minerals in root xylem is called xylem
sap.
- xylem carries the xylem sap up to stems & leaves (branching
into leaf veins) eventually being absorbed by all cells of the
plant
Properties of Water
Two properties of water allow xylem sap to rise great distances
against gravity
1. Cohesion – the attraction of water
molecules to other water molecules
due to their polar nature. (Observed
as water forms droplets)
- the column of xylem sap can be broken by a break in the vessel
or a bubble in the sap.
Q: Explain how each of these situations could be caused.
A: Break – cut in root, stem or leaf
Bubble – freezing in winter
2. Adhesion – the attraction of water molecules to molecules of
other substances. (Observed as water sticks to the glass in a
graduated cylinder, forms a meniscus)
- water also clings to the cellulose wall of a xylem vessel,
preventing the sap from falling back towards the roots, thus
helping to fight the force of gravity.
The two main mechanisms that aid the upward movement of
water in plants are root pressure and transpiration.
A. Root Pressure Pushes
Root pressure occurs when root cells actively
transport minerals into the xylem. This causes water
to diffuse into this hypertonic area, building root
pressure in the xylem which forces fluid up the xylem vessels.
Fluid seeping from a cut stem of a plant occurs due to root
pressure.
Q: Will all transport cease due to a cut halfway up
the stem?
A: Xylem sap will still flow upwards above the cut (compare to a
cut straw)
DEMO p.335 Up With Root Pressure
B. Transpiration Pulls
Transpiration of water from leaf stomata generates a pulling force, aiding the
upward transport of water –
1. The energy for xylem transport ultimately
comes from the heat of the Sun.
2. Water molecules evaporate leaving the air
within the leaf slightly drier
3. Water then diffuses out of leaf cells into
intracellular fluid where solutes are more concentrated
4. As evaporation from the leaf continues, the cohesion of water
molecules draws the water up the xylem vessels, replacing
evaporated water.
Adhesion of water molecules to the walls of xylem vessels aids
the process.
Transpiration increases as temperature rises,
increasing water movement through xylem. Xylem
transport speed can be up to 50 meters/hour
Do BLM 9-4 Transpiration Rate in Plants
Sugar Transport in Phloem
Sugars produced by the palisade and spongy tissue cells of the
leaf are transported to the stems and roots by phloem vessels
1. Sugar, minerals, and other nutrients enter phloem by active
transport
2. Water flows by osmosis, causing phloem cells to swell with
turgor pressure. ( Sugar + nutrients + water = phloem sap)
3. Phloem sap flows down the concentration gradient and the
fluid pressure forces the sap through pores in phloem cell
walls and into surrounding cells
4. The nutrients are continually used up by tissues of the stem
and root resulting in a pressure gradient that causes a
continual flow of solution from leaf to root.
Phloem transport ranges from 20 cm/hr to 100 cm/hr
Q: How do aphids help researchers study phloem?
A: After they probe a phloem cell with their stylet,
researchers cut off the stylet. Phloem continues to
ooze out and can be studied. NOTE: – artificial probes
injure the phloem cells.
Do p.339 Investigation “The Flow in Phloem”
Do p.340 Check Your Understanding Questions 1-7
Science Focus 10
Unit 3
9.4
Plant Control Systems
Tropisms are plant responses in which the plant grows towards or
away from a stimulus (=an environmental factor, ex. Light, gravity,
touch)
1.
Phototropism is the growth of a plant toward a light source.
WHY? This maximizes light absorption for photosynthesis
which fuels plant growth
HOW? Plant cells respond to light by growing at different
rates. When cells on one side of a stem grow more
elongated than cells on the other side, the stem curves.
SKETCH AND LABEL a plant bending towards the Sun,
indicating area of elongation.
(See p.341 Fig. 9.18)
Do p.342 The Darwins Experiment
THE MECHANISM
Charles and Francis Darwin concluded that the tip of the
seedling detects light, transmits that information to the
stem, and the rate of growth of stem cells is affected. The
Darwins suspected a chemical signal triggered the growth.
Decades later, Peter Boysen-Jensen tested the presence of
a chemical signal, finding that the chemical could pass
through gelatin but not mica. (See Fig. 9.19, p.344)
THE HORMONE
In 1926, Frit Went confirmed that a chemical he named
“auxin” (meaning to grow”) was produced in the plant tip.
Auxin is actively transported through the cells towards the
shaded side of the stem causing cells there to grow longer
than cells on the lighted side, resulting in bending towards
the light.
Q: Summarize Went’s experiment on p.345, Fig. 9.20
A: Agar containing auxin caused cell elongation in stems on
which ever side it was placed (light not being a factor)
2. Gravitropism – is the growth of a plant in response to the
force of gravity
1. Negative gravitropism – stem grows towards sunlight and
against the force of gravity
2. Positive gravitropism – roots grow into the soil & towards
the force of gravity
THE MECHANISM
Gravitropism occurs as soon as seeds germinate and the
response of the stems and roots is consistent regardless of
how the seed is oriented when it is planted.
Auxin is responsible for the plant growth response to
gravity.
a) IN THE STEM – when a plant is placed on its side, more auxin
collects in the cells on the stems lower side. These cells then
grow longer resulting in the stem curving upward.
b) IN THE ROOT – increased auxin concentration inhibits root
growth. When a root is placed sideways, auxin collects along
the lower side but cell growth is inhibited here. Cells on the
upper side, however, continue to grow longer, resulting in the
root growing downward.
Another theory of positive gravitropism is that dense starch
grains in the root tip cells may settle at the low point in cells
signalling the direction of gravity and influencing the direction of
growth.
DO p.346 Spinning Seeds
3. Nastic Response is a plant’s response to touch. The stimulus
of touch sends an electrical signal to certain leaf cells resulting in
a drop in turgor pressure. This causes the leaf to collapse.
Q: Give two examples of plants exhibiting a nastic response
(See p.344)
A: Mimosa, Venus Fly Trap
4. Thigmotropism is a rapid growth of certain plant cells in
response to touch. It is seen in plants that use tendrils to wrap
around supports or other plant stems. Eg. The tendrils of a pea
plant that come in contact with a chain-link fence will wrap around
it, gaining support as it grows.
Do BLM 9-6 Discovering Tropisms
Do 9.4 Review: p.348 Q. 1-7
Do Chapter 9 Review p.350 Q. 1-8, 10, 11