The Living Environment
Regents Review
Topic 1: Similarities & Differences
Among Living Organisms
Organelle
Function
Human System
Nucleus
Control center
Nervous & endocrine
Mitochondria
Aerobic respiration
Circulatory, digestive,
respiratory
Ribosome
Protein synthesis
Digestive, circulatory
Cytoplasm
Holds organelles,
transport
Circulatory
Vacuole
Storage of wastes
Excretory
Lysosome
Intracellular digestion
Digestive, immune
Cell membrane
Regulates passage of
substances in and out of
cell
Immune system
Topic 1 cont’d
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Transport
 Cell membrane is a lipid bilayer (two layers of lipids with proteins in
between- some acting as channels and receptors)
 Concentration gradient (when a difference in the amount of a particular
substance exists across a barrier such as the cell membrane)
 Passive transport (diffusion)- substances move along concentration
gradient (from high concentration to low) WITHOUT the use of energy
 Ie. O2,, CO2 & H2O (osmosis)
 Saline solution (water moves out of cells  dehydrate)
 Distilled water (water moves into the cells  swell & potentially
burst)
 Active transport- substances move against concentration gradient
WITH the use of energy in the form of ATP
 Na+ and K+ are kept at high levels in and out of the cell to
maintain a gradient for nerve impulses (sodium/potassium pump)
Osmosis
Red onion cells in
concentrated salt
solution (osmosis
out of cell)
Red onion cells in distilled
(100% water) (osmosis into
the cell)
Topic 1 cont’d
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Cell receptors
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Extend off of cell membrane
Have a specific shape
Only recognize certain substances to
allow in or out of the cell
Neurons (nerve cells) have receptors
for specific chemicals
(neurotransmitters)
Certain cells have receptors for
certain hormones as the hormones
travel throughout the circulatory
system to reach target cells
Antibodies
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Proteins produced by B cells in
immune system (white blood cells)
Specific in shape for particular
pathogens
They isolate pathogens for
destruction by other white blood cells
Topic 2: Homeostasis in Organisms
Process
Location
Raw
Products
materials
Photosynthesis chloroplast CO2 & H2O Glucose,
O2, & H20
Respiration
mitochondria Glucose &
O2
(aerobic)
Role in
homeostasis
Provides
food (simple
sugars) for
producers
ATP, CO2 Releases energy
from chemical
& H2O
bonds of
glucose to the
usuable form of
ATP
Topic 2 cont’d
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Enzymes:
 Proteins
 Specific shape so that they
only fit with a certain
substrate
 Enable (allow) reactions to
occur faster and with less
energy (organic catalysts)
 Have optimal pH and
temperature (if outside of
optimal range the enzyme can
be denatured (change shape)
and be unable to function
properly
Topic 2 cont’d
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Feedback mechanisms
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Most common type in the human body is negative feedback
Something is off unless activated, once its job is completed
it is deactivated
Comparable to a thermostat (it only signals the oil burner to
turn on when the temperature drops below predetermined
level- once temp. is restored a signal is sent to turn off the
oil burner)
Our hormones typically work in this fashion
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Insulin is produced by the pancreas in response to an increase in
blood sugar levels
the sugar is taken in by the liver and converted to the
polysaccharide glycogen
once levels are low enough a signal is sent to the liver to stop
insulin production
Topic 2 cont’d
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Guard cells w/
open stomate
(top view)
Guard cells and feedback:
 Guard cells are
specialized cells found
mainly in the lower
epidermis of a leaf
 They regulate an opening
called a stomate, which
allows gases such as CO2,
H2O & O2 in and out as
needed by the plant
 The guard cells keep the
stomate closed unless the
plant needs gases to enter
or leave
Cross section of leaf
epidermis w/ guard
cells & stomate
Topic 3: Genetic Continuity
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DNA= deoxyribonucleic acid
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Nucleic acid
Double helix
Building blocks = nucleotides
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Sugar (deoxyribose)
Phosphate
Nitrogen base (A,T,C,G)
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A-T & C-G
RNA = ribonucleic acid
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Nucleic acid
Single stranded
Building blocks = nucleotides
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Sugar (ribose)
Phosphate
Nitrogen base (A,U,C,G)
Topic 3 cont’d
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DNA replication
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Unwinds
Unzips between bases
Two identical molecules are created
Occurs prior to mitosis
Protein synthesis
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DNA has instructions for a particular protein
The portion needed unwinds and unzips
mRNA is created from the DNA template to carry code from nucleus to
ribosome (transcription)
At the ribosome the mRNA is read in groups of three bases (codons)
tRNA delivers the appropriate amino acids over to the codons on
mRNA and then leaves
Peptide bonds join the amino acids together to create a polypeptide
(protein)
Topic 3 cont’d
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Genetic engineering:
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Gene splicing- restriction enzymes used to cut out
desired gene from DNA
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Desired gene from one organism is inserted into the
DNA of another organism
The gene for human insulin has been successfully
inserted into a plasmid (circular portion of DNA) of
bacteria  bacteria produce human insulin and pass this
trait onto their offspring
Genes for herbicide resistance, frost resistance, nutrient
content etc. have been inserted into plant DNA (crops
such as corn, rice, tomatoes)
Chromatography
Gel Electrophoresis
Topic 3 cont’d
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Selective breeding:
 Farmers have been doing this for
years
 Select seeds from desirable
plants (biggest corn, juicy
tomato etc.) and only grow the
seeds from those plants
 This is also done with livestock,
racehorses and dogs
 Certain individuals are
chosen to mate so that their
desirable traits are passed on
to offspring
 Decreases biodiversity
 Recessive traits (such as
diseases) can become more
prominent
Topic 4: Reproduction &
Development
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Meiosis – cuts chromosome number in half in the
creation of gametes (egg and sperm- contain
monoploid/haploid (n) amount of chromosomes)
Crossing over and genetic shuffling increase variety
in gametes
Meiosis occurs in the gonads or sex organs (ovaries
& testes)
Fertilization is the union of egg and sperm to restore
diploid number (2n) of chromosomes to create a
zygote
Cleavage or mitosis in a zygote increases the number
of identical cells
Stages of cleavage
Topic 4 cont’d
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Differentiation is the process by which cells are given specific
instructions through the activation of certain portions of their
genetic code
Fertilization occurs in the fallopian tube of a human female
(oviduct)
The zygote implants in the uterus and a placenta develops
from the uterine wall for the transport of nutrients and wastes
between mother and fetus
Feedback is involved in regulating the menstrual cycle
involving the pituitary gland in the brain, the ovary and the
uterus
Topic 4 cont’d
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Reproductive technology:
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IVF- egg and sperm are harvested from parents and united
in a petri dish
Cloning- a nucleus from a body cell of the organism to be
cloned is put into an empty egg
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The egg with the transplanted nucleus is treated with growth factors
When the zygote has divided (morula stage) it is put in a surrogate
for gestation
Screening:
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Amniocentesis- amniotic fluid is sampled to screen for genetic
disorders
Karyotype- chromosomes in amniotic fluid are harvested and
arranged in order from # 1 – 23 to screen for chromosomal
disorders such as Down Syndrome
Ultrasound
Karyotype of Individual withDown
Syndrome
Normal Karyotype
Topic 4 cont’d
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Mitosis: involved in asexual reproduction
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IPMAT:
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Interphase- majority of the lifespan of a cell (all life
functions and chromosomes replicate)
Prophase- chromosomes become visible and nuclear
membrane begins to break down
Metaphase- double-stranded chromosomes line up at the
middle
Anaphase- chromatids separate toward poles of the cell
Telophase- nuclear membrane reappears around each set
of chromosomes and the cell membrane begins to pinch
in (or in a plant cell a cell plate forms from the inside
out)
Topic 4 cont’d
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Types of asexual reproduction:
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Binary fission (equal cytoplasmic division)- bacteria
Budding (unequal cytoplasmic division) – yeast
(unicellular) and hydra (multicellular)
Vegetative propagation – part of a plant is used to grow an
exact copy of that plant (leaves, stems etc.)
Regeneration – a part of the organism can be replaced or an
entire organism can be created from that piece (starfish,
lizard tail)
Budding in yeast
Unicellular Bud
Multicellular
bud
Budding in hydra
Topic 5: Evolution
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Natural selection (Charles Darwin)
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Overproduction = more offspring produced than can
possibly survive
Competition (struggle for survival)- there are limited
resources
Variation- some will have a particular trait or set of traits
that are favorable while others will not
Survival of the fittest- those with the favorable trait will be
more likely to survive reproduce and pass the trait on to
their offspring
** Over time the population SHIFTS to CONSIST of
mostly those with the favorable trait (DO NOT SAY
BECOME RESISTENT ETC.!!!!!!!)**
Topic 5 cont’d
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Evidence of evolution:
 Homologous structures –
similar in origin and layout but
may be different in function
and appearance (suggest a
common ancestor)
 Comparative embryology,
cytology and biochemistry are
all types of molecular evidence
based on DNA and are
therefore more reliable than
physical evidence
Topic 5 cont’d
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Adaptations = favorable traits for a particular
environment at a particular time that increase chances
of survival
Selecting agents (an environmental factor such as
food source that determines which traits in a
population are favorable)
Speciation – creation of a new species as the result of
accumulating enough different adaptations from the
main population to be able to successfully reproduce
fertile offspring
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Reproductive and geographical isolation contribute to this
Adaptive radiation – development of several new species
from a single common ancestor (finches)
Variation in shell
coloration/pattern
Overproduction of
clownfish eggs
Topic 6: Ecology
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Levels of organization:
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Biosphere  biomesecosystemcommunitypopulation (greatest
biodiversity to least amount of biodiversity)
Abiotic = all nonliving factors in an ecosystem (ie. Carbon
dioxide, water, sunlight, temperature, pH)
Biotic= all living factors in an ecosystem (algae, trees, frogs,
minnows, foxes, sharks etc.)
Food webs provide illustrations of all possible pathways of
energy/nutritional relationships in an ecosystem (more stable)
Food chains indicate one pathway of energy/nutritional
relationships in an ecosystem
Topic 6 cont’d
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Producers are always found at the base in an
ecosystem/foodweb/foodchain/food pyramid because
they contain the most available energy
Energy CANNOT be recycled in an ecosystem and
must be constantly SUPPLIED for it to remain stable
Materials such as carbon dioxide, water, oxygen,
nitrogen must be RECYCLED by decomposers such
as bacteria and fungi for an ecosystem to remain
stable
Topic 6 cont’d
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Nutritional Relationships/trophic levels
 Producers/autotrophs convert light energy into chemical
energy in organic compounds (glucose)- a.k.a- make their
own food (inorganic raw materials  organic product)
 Primary consumers (herbivores)- consume only producers
 Secondary consumers (can be omnivores or carnivores)consumer other consumers and sometimes some producers
 Teriary consumers (typically carnivores) consume
primarily other consumers
 Scavengers consume dead organisms (turkey vultures,
hyenas, raccoons)
 Decomposers break the remains of dead organisms (and
their wastes) down to recycle their nutrients back into the
ecosystem
Topic 6 cont’d
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Symbiotic relationships:
Mutualism (both benefit: +,+) (ie. Remora
cleaning parasites off of a shark)
 Parasitism (one harmed, one benefits: -,+) (ie.
Ticks and dogs, tapeworm and human)
 Commensalism (one benefits, one unaffected: +,0)
(best example is barnacles on a whale)
**Predator/prey is NOT a symbiotic relationship
because it is short term- once the prey is caught the
relationship is over 
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Barnacles on a whale
A remora and a shark
Tick on a dog
Topic 6 cont’d
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A habitat is where an organism lives and its niche is its role in that habitat
(ie. What it consumes)
Competition results over limited resources as there can only be one species
per niche in an ecosystem
Limiting factors help keep populations in an ecosystem in check: ie.
Predators keep their prey populations in check and visa versa, light
intensity controls where plants can grow, temperature, pH (they can be
biotic or abiotic)
Carrying capacity = the amount of a particular population that can be
maintained indefinitely in an ecosystem (determined by limiting factors)
Ecological succession (due to natural disaster such as a volcanic eruption or
forest fire)
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Pioneer organisms are the first to show up and can survive harsh conditions (ie.
Lichens, grasses, mosses)
Climax community is the final, stable, self-sustaining stage that can last until a
major disruption
Each stage paves the way for the next, making them self-sacrificing
Carrying Capacity Graphs
Topic 7: Human Impact
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Global Warming
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Cause- excess greenhouse gases in atmosphere trap heat
Carbon dioxide is the most common greenhouse gas
released
Burning fossil fuels and deforestation are two major
sources of increased atmospheric carbon dioxide
Cleaner fuel sources such as solar power, wind etc. are
ways to reduce greenhouse gas emissions
Reforestation is another way as trees take in CO2 from the
atmosphere for photosynthesis
Burning fossil fuels also releases sulfur dioxide which can
cause acid rain!
Topic 7 cont’d
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Ozone depletion:
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Cause is CFCs from coolants in refrigerators, ACs, and in
aerosols
Montreal Protocol banned CFCs however older appliances
if disposed of improperly can release CFCs into the
environment
Not all countries adhere to this ban, thus some CFCs are
still used in products globally
The ozone protects organisms from more harmful UV rays
getting through, but the thinner it is the more rays can
enter, increasing the incidence of skin cancer
Laws must be enforced globally banning CFCs and there
must be stricter penalties for improper disposal
Topic 7 cont’d
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Biological Controls:
 Pesticides can harm species other than those that are being
targeted
 Biological controls are natural remedies for pest control
and include natural predators of pest species and sterilizing
individuals to prevent reproduction
 Advantages = target pest populations only, can be cheaper
 Disadvantages= the natural predators may begin to
consume native species or compete for a niche with a
native species
 Biomagnification = greater quantities of pollutants are
found in top level consumers as each successive level
consumes more of the previous level (ie. DDT still found in
fatty tissue of humans)
Topic 7 cont’d
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Deforestation
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Leads to loss of habitat
Decreases biodiversity
Medicines and other medical advancements may
go undiscovered
Increases carbon dioxide in atmosphere as there
are less trees to take it in for photosynthesis
Stricter laws should be passed to limit and
reforestation can reverse the effects as long as it is
done at a rate to compensate
Topics 8&9:
Lab Skills and Scientific Method
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Scientific Method
Problem: Phrased as a question
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Hypothesis: Phrased as a statement
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Ie. How does pH affect petal color?
Ie. It is hypothesized that an acidic pH will produce flowers with
red petals, while a basic pH will produce flowers with white petals
Design a controlled experiment:
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Only one variable (ie. pH level) = INDEPENDENT
DEPENDENT VARIABLE relies on independent ie. Growth relies
on or depends on the pH, temperature, amount of sunlight etc.
Other factors remain the same (constants) (ie. Plant species, amount
of water, sunlight, temperature)
Collect measurable data (ie. Number of plants with red petals and
number of plants with white petals in each group)
Topics 8&9 cont’d
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Organize data into a table with headings and units and create an
appropriate graph with an even scale and labels
Large sample size (the more specimens in each group the more
reliable the data- accounts for variety)
Draw a conclusion (state whether or not the hypothesis was
supported and provide data from the experiment to support)
(ie. Out of 50 plants in the acidic pH 45 of them had red
petals, while in the basic pH 49 of the 50 plants had white
petals, therefore the hypothesis that flowers grown in acidic
soil will have red petals was supported)
Future research – explain how the experiment could be
improved in the future or expanded upon
Topics 8&9 cont’d
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1cm = 10 mm
1mm = 1000 µm
Microscope:
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Coarse adjustment (only under low power)
Fine adjustment (for both)
Eyepiece (ocular) typically 10x
Objectives (low typically 10x, high typically 40x)
Total magnification = eyepiece x objective
Images appear upside down and backwards and appear to
move in opposite direction
High power has a SMALLER field of view and is
DARKER than low power!!
Topics 8&9 cont’d
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Chromatography- separates pigments into color
components (those that are more water soluble travel
further up the paper)
Gel electrophoresis- restriction enzymes cut DNA
from each individual into fragments of various sizes
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The DNA of each individual is loaded into a separate well
in the gel
The gel is hooked up to a current (negative at the top and
positive at the bottom) as DNA has a negative charge it is
drawn toward the bottom toward the positive charge
A banding pattern is created as the larger fragments settle
toward the top and the smaller ones toward the bottom
Both techniques are used to determine
evolutionary relationships (common ancestry)
Topics 8&9 cont’d
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Indicators:
 Starch indicator (Lugol’s iodine)- goes from an amber/gold
color to a deep blue/purple in presence of starch
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Glucose indicator (Benedict’s solution)- goes from a pale
blue to an orange/green color in the presence of glucose
WHEN HEATED!