Big Idea 2:
Biological systems utilize free energy and molecular building blocks
to grow, to reproduce and to maintain dynamic homeostasis.
Enduring understanding 2.A:
Growth, reproduction and maintenance of the organization
of living systems require free energy and matter.
Essential knowledge 2.A.3: Organisms must
exchange matter with the environment to grow,
reproduce and maintain organization.
Subobjective 2.6: I can use calculated surface
area-to-volume ratios to predict which cell(s)
might eliminate wastes or procure nutrients
faster by diffusion.
These are the equations you
need to be able to use (you
don’t have to memorize
them)
Use the video to review
https://www.khanacademy.org/math/
basic-geo/basic-geo-volume-surfacearea/basic-geo-volumes/v/cylindervolume-and-surface-area
How is surface to volume ratio calculated and
how does an increase in cell size affect it?
Which cell has a greater surface area?
(calculate the surface area of each cell)
The big one: 5cm X 5cm = 25 cm2
6cm2
There are 6 sides, so surface area =
25cm2 X 6 = 150cm2
The little one’s surface area =
1cm X 1cm = 1cm2
There are 6 sides, so surface area =
1cm2 X 6 = 6cm2
150cm2
Which cell has a greater volume? (calculate the
volume of each cell)
The big one:
1cm3
5cm X 5cm X 5cm = 125 cm3
The little one’s volume =
1cm X 1cm X 1cm = 1cm3
125 cm3
Which cell has a greater surface to volume ratio?
(calculate the reduced surface to volume ratio of each
cell)
2
The little one
The big one has a
surface area of
150cm2 and a volume
of 125cm3
6cm
 6 :1
3
1cm
150cm 2
 1.2 :1
3
125cm
6:1
1.2 : 1
This means more stuff can get into and out of the little cell faster
than the big cell
Why does surface area increase at a slower rate than
volume when we scale up the same shape?
1000
The dependent variable
is volume and surface
area
900
800
700
600
Volume
500
Surface area
400
300
200
100
0
0
The independent
variable is length of one
side of a cube
1
2
3
4
5
6
7
8
9
10
1000
900
800
700
600
Volume
500
Surface area
400
300
200
100
Since volume increases to
the power of 3 and surface
area increases to the
power of 2, the volume
increases at a much faster
rate causing the ratio of
surface area to volume to
decrease rapidly with an
increase in size when the
shape is constant
0
0
1
2
3
4
5
6
7
8
9
10
How does surface to volume ratio effect how an
organism exchanges matter and energy with the
environment?
Explain the video below in terms of surface to volume ratio
https://www.youtube.com/watch?v=Ee0o8goqfOc
As an animal grows, its volume increases at a greater rate than
its surface area because the shape of the dog stays the same.
Little dogs have a higher surface to volume ratio than big dogs,
so they lose heat at a faster rate and therefore have a harder
time maintaining temperature homeostasis
Define diffusion
The spontaneous movement of molecules from an area of
relatively high concentration to an area of relatively low
concentration
http://www.youtube.com/watch?v=gXJMBgyT_hk
Pretend the 2 cubes to the right are single-celled
organisms. Which organism would have a harder
time getting nutrients and eliminating wastes?
Explain in terms of surface to volume ratio
Since molecules move randomly from
areas of high concentration to low
concentration, the big cell would have a
harder time getting nutrients in and
eliminating waste because its surface to
volume ratio is 1.2 : 1 which is much
smaller than the 6 : 1 ratio of the small
cell.
https://www.khanacademy.org/science/biology/cellularmolecular-biology/cell-division/v/diffusion-and-osmosis
Imagine the red dot
is some waste
product like CO2 and
it is moving randomly
in the cell. Just by
chance, it will stay in
the large cell longer.
Subobjective 2.7: I can explain how cell size and
shape affect the overall rate of nutrient intake
and the rate of waste elimination.
Why are mouse cells the same size as elephant
cells?
Which organism wins in a battle?
The little one
Why did that happen?
Many essential molecules move
into, out of , and within the cell by
diffusion
Diffusion is fast over small
distances, but slow over large
distances
Volume increases by the cube (power
of 3) and surface area only increases
by the square (power of 2)
1.2 : 1
6:1
So a big cell has too much volume to be serviced by too little
surface area and diffusion is too inefficient over large distances
Which organism wins in a battle?
The big one
Why did that happen?
All things being equal; bigger is
better
The big organism has the exact
same surface to volume ratio as
the small one
So organisms like elephants grow
by adding more small cells rather
than increasing the size of their
cells
How do cells increase surface to volume ratio?
1) They stay small
2) They grow long and thin (neurons)
3) They extend their plasma membranes forming microvilli
Plants increase absorption
of nutrients by increase the
surface area of roots with
“root hairs”
Subobjective 2.8: I can justify the selection of
data regarding the types of molecules that an
animal, plant or bacterium will take up as
necessary building blocks and excrete as waste
products.
What are the building blocks of life?
What are the 4 macromolecules essential for life?
1)
2)
3)
4)
Carbohydrates
Lipids
Proteins
Nucleic acids
What kinds of atoms are these macromolecules made of?
Carbohydrates
Lipids
Proteins
Nucleic acids
Oxygen
Oxygen
Oxygen
Oxygen
Carbon
Carbon
Carbon
Carbon
Hydrogen
Hydrogen
Hydrogen
Hydrogen
(some have
nitrogen)
(some have
nitrogen)
Nitrogen
Nitrogen
(some have
phosphorous)
Phosphorous
Sulfur
What are essential elements?
Elements living things need to survive
The major essential elements are about the same in all
living things, but there is variation in the trace elements
required
An element required in minute
quantities (examples are iron and
iodine)
What are the 6 most
abundant elements in
living things?
If you can’t name the reactants and products of
photosynthesis and cellular respiration and name the
waste products of each, review subobjective 2.5
Subobjective 2.9: I can represent graphically or
model quantitatively the exchange of molecules
between an organism and its environment, and
the subsequent use of these molecules to build
new molecules that facilitate dynamic
homeostasis, growth and reproduction.
How do nutrients cycle?
Define detritus
Dead organic matter (bits of
organisms and feces)
Define decomposer
An organism that consumes detritus
(they are essential for returning the
nutrients locked up in producers and
consumers to the environment)
The most important decomposers
are bacteria and fungi
Describe a general
model for
biogeochemical
cycles
Compare and contrast the movement of energy through and
ecosystem and the movement of nutrients through and ecosystem
Nutrients cycle (this means you are composed of the same nutrients
that composed the dinosaurs and your favorite historical person)
Energy must be constantly added to the ecosystem because it is
constantly lost; not destroyed, it radiates out of the ecosystem and
out into space.
How does carbon cycle?
Describe the carbon
cycle
What is the biological importance of carbon?
Carbon is used to make the 4 macromolecules all life are
composed of (carbohydrates, proteins, lipids, and nucleic acids
How is carbon made available to living things?
Photosynthetic organisms (plants, some protists, and some
bacteria) fix carbon dioxide from the atmosphere by
photosynthesis
This carbon passes through consumers
How does carbon get into the atmosphere
All organisms (plants, animals, protists, fungi, and bacteria) add
carbon dioxide to the atmosphere by cellular respiration
Humans add additional CO2 by burning fossil fuels
Carbon compounds (oil, coal, and natural gas) that haven’t been in
the carbon cycle for millions of years
How does nitrogen cycle?
Describe the
nitrogen cycle
What is the biological importance of nitrogen?
It is used to make nucleic acids and proteins
Describe nucleic acids
Nucleic acids
have nitrogen
and
phosphorous
Nucleic acids carry
the hereditary
information for
making proteins
Nucleic acids are polymers of
nucleotides
Describe proteins
Proteins are folded up chains of amino acids (shown with
different colors below)
Proteins have sulfur
and nitrogen
How is nitrogen made available to living things?
Nitrogen in the atmosphere (N2) is made available to plants by
nitrogen fixing bacteria, and a small amount by lightening
Nitrogen cycles from plants to consumers to decomposers, and
ammonifying bacteria make nitrogen available to plants again
Humans add enormous quantities of nitrogen in fertilizers made
by combining N2 gas from the atmosphere with methane
forming ammonia (NH3)
How does nitrogen get into the atmosphere
Nitrifying bacteria convert ammonia to nitrite (NO2-), nitrite to
nitrate (NO3-), and nitrate to nitrogen gas (N2)
Define mutualism
A symbiotic relationship between 2 different species where
both species benefit from the relationship
Describe the relationship between rhizobacteria
and plants
Nitrogen fixing bacteria use N2 gas from the atmosphere to
make ammonia
Nitrifying bacteria transform NH3 (ammonia) to nitrate (NO3-)
Plants can absorb NH4+ (ammonium) and NO3Plants return the favor by nurturing the bacteria with as
much as 20% of their photosynthetic output
By feeding this diverse community of bacteria, the plant gets
more of a limiting nutrient, nitrogen, and grows more than it
otherwise would
Describe the sources of nitrogen and where this nitrogen goes
(lightening and fertilization are left out in this diagram)
Nitrogen fixing bacteria take N2 from the atmosphere and
ammonifying bacteria release NH3 locked up in the organic
compounds from detritus
Describe the role of bacteria in transforming ammonia (NH3)
Nitrifying bacteria oxidize ammonium to Nitrite and then Nitrate
(different species oxidize each step)
Describe how plants get the nitrogen they need for
synthesizing proteins and nucleic acids
Plant roots absorb nitrate and ammonia and transport it via
xylem cells to the rest of its body
Describe how nitrogen cycles between the soil and the
atmosphere
Denitrifying bacteria reduce nitrate (NO3-) to N2 gas, but not all of
the NO3- is completely reduced to N2 gas. Some is partially
reduced to NO2 which is a powerful greenhouse gas that stays in
the atmosphere for about 114 years.
How do humans affect the nitrogen cycle?
We have doubled the
amount of available
nitrogen. By adding more
ammonia than our crops
can use, ammonia in the
atmosphere has tripled
(reducing air quality),
nitrates have increased in
our water supply which is
dangerous for infants,
nitrites and nitrate runoff
causes eutrophication, and
NO2 gas is accelerating
global warming
Water from the
watershed to the
right was tested for
nitrate. What does
the graph show?
The dependent variable
is nitrate concentration
measured in mg/L
The independent
variable is time with two
treatments so the rate of
emissions between
treatments is being
compared
Nitrate concentration
in the two watersheds
is similar and relatively
low from 1965 to 1966.
This shows that trees
and other organisms
take up the majority of
nitrate available in the
soil.
One of the watershed is clear-cut and about 6
months later, nitrate concentration significantly
increased. We can conclude that trees are
essential for stabilizing soil nutrients such as
nitrate
How does phosphorous cycle?
Describe the
phosphorous
cycle
What is the biological importance of phosphorous?
Phosphorous is necessary for making nucleic acids,
phospholipids, and ATP
Nucleic acids
have nitrogen
and
phosphorous
Phospholipids
have phosphorous
ATP has
phosphorous
How is phosphorous made available to living things?
Phosphorous is mostly found as phosphate (PO43-) which binds
tightly with soil, so it tends to cycle within a given ecosystem
New phosphorous is added by weathering of rock
How does the phosphorous cycle differ from the nitrogen and
carbon cycle
There is not a significant amount in the atmosphere and it is
usually the limiting nutrient in an ecosystem
How do the four emergent properties of water
contribute to Earth’s suitability for life
What are the emergent properties of water that make it
critical to life?
1)
2)
3)
4)
It’s polar so it is cohesive and adhesive
Large heat capacity so it regulates temperature
It expands when it freezes
Good solvent
Cohesion and adhesion
https://www.youtube.com/watch?v=45yabrnryXk
Cohesion and adhesion
Water sticks to itself
creating surface tension
Water sticks to other
molecules
Explain how the cohesion and adhesion of water
molecules allow plants to be tall
When a water
molecule
evaporates out a
stomate of a leaf,
it exerts an
upward force all
the way to the
root. This pulls
water up against
gravity without
energy input from
the plant
Water molecules
adhere to the
surface of xylem
cells and cohere
to each other in a
continuous chain
from stomata to
root
http://www.youtube.com/watch?v=umUn8D6gEOg&feature=related
Define temperature
The average kinetic energy of a volume of matter
Define calorie (c)
The amount of heat required to raise the
temperature of 1 gram of water 1⁰C
Define kilocalorie (C)
1000 calories (c)
A lower case ‘c’ is the abbreviation for 1 calorie and a
capital ‘C’ is the abbreviation for kilocalorie
Define joule (J)
A measure of energy like calorie
Define heat capacity
The amount of heat necessary to change the
temperature of a substance
Define specific heat capacity or specific heat
The heat capacity per unit of mass
Water has an unusually high heat
capacity because of hydrogen bonding
This means water absorbs or releases
a lot of energy with a small change in
temperature
http://www.youtube.com/watch?v=SdgUyLTUYkg&feature=fvwrel
Water has a lower density as a solid
The ice covering this lake keeps the water
beneath relatively warm by providing
insulation
If solid water were more dense than liquid
water, lakes and oceans would freeze from the
bottom up and never thaw, making life
impossible over much of the planet.
Water is a near universal solvent
This property of water allows the chemical reactions
necessary for life to happen quickly
http://www.youtube.com/watch?v=gN9euz9jzwc
Define solvent
A liquid that other substances dissolve in
Define solute
A substance that dissolves
in a solvent
Define solution
A liquid with evenly
distributed solute
dissolved in a solvent
How does water dissolve atoms and molecules?
A sphere of water molecules surrounds a dissolved
substance allowing the substance to be suspended in
the solution
NaCl (sodium chloride)
dissolving in water
A water soluble protein
(lysozyme) dissolved in water
Define hydrophilic
A substance that is attracted to water because it is
polar. Hydrophilic substances typically dissolve in
water
Define hydrophobic
A substance that repels water because it
is mostly nonpolar. Hydrophobic
substances do not dissolve in water.
**Substances exist on a
Wax makes leaves
hydrophilic/hydrophobic continuum
hydrophobic