Biology EOC Semester 1 and 2 Review
Part 1:
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Characteristics of Life
Made of cells
Reproduction
Based upon a universal genetic code
Grow and develop
Obtain and use energy
Respond to their environment
Maintain a stable internal environment (homeostasis)
As a group, change over time (evolve)
Part 2: Cell Structure and Function
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Cell theory
1. All living things are made of one or more cells
2. Cells are the basic units of structure and function in organisms.
3. All cells arise from existing cells.
Cell membrane
1. Lipid bilayer
2. Semipermeable membrane
Two key types of cell
1. Prokaryotic—no true nucleus or membrane bound organelles
2. Eukaryotic
Transport across a cell membrane
1. Passive transport—movement from high to low concentration without use of
energy. Examples include diffusion and osmosis (diffusion of water across a
selectively permeable membrane). Facilitated diffusion uses transport proteins to
carry the substance across the membrane; no energy is required for this, either.
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Diffusion
Diffusion or passive
transport is the movement of
materials from a region of
higher to a region of lower
substance concentration. The
diagram at the right shows the
movement of molecules from
higher concentration on side A
to a lower concentration on
side B.
2. Active transport—use of energy to move materials against the concentration
gradient; carrier proteins can be used for this as in the sodium-potassium pump;
endocytosis moves materials into a cell and exocytosis moves materials out of
the cell.
Active Transport
In active transport, molecules move from a
region of lower concentration to a region of
higher concentration. As this process does not
naturally occur, the cell has to use energy in the
form of ATP to make active transport occur.
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Cell components—contain parts called organelles that are used to provide the framework
and functional units of the cell
A Typical Animal Cell
Some Cell Organelles
Cell Organelle
Function
control center of the cell
nucleus
contains DNA which directs the synthesis of
proteins by the cell
mitochondrion
carries on the process of cell respiration
converting glucose to ATP energy the cell
can use
endoplasmic reticulum
transport channels within the cell; can be
rough with ribosomes on it or smooth
ribosome
found on the endoplasmic reticulum and free
within the cell
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responsible for the synthesis of proteins for
the cell
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cell membrane
selectively regulates the materials moving to
and from the cell
Golgi apparatus
final processing of cell products
food vacuole
stores and digests food
contractile vacuole
pumps out wastes and excess water from
the cell
chloroplast
found in plant cells and algae; carries out
the process of photosynthesis
cell wall
surrounds and supports plant cells, fungi,
bacteria, and some protists; not found in
animal cells
Energy Production
1. Photosynthesis—in chloroplast
Light Energy + 6CO2 + 6H2O  C6H12O6 + 6O2
2. Cellular respiration—in mitochondrion
C6H12O6 + 6O2  6CO2 + 6H2O + ATP (energy)
3. Release of energy from ATP is used to power chemical reactions needed to carry
out life activities.
ATP  ADP + P + energy
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Levels of organization in multicellular organisms
1. organelles
2. cells
3. tissues
4. organs
5. organism
Viruses
1. Non-living—viruses do not demonstrate the characteristics of life because they
cannot replicate without the use of a host cell; viruses are noncellular
2. Structure—composed of an inner core of nucleic acid (DNA or RNA) and an
outer protein coat (capsid); some also have an additional outer envelope and
some surface proteins; some viruses are retroviruses which use reverse
transcriptase to make DNA from the RNA template; AIDS is a retrovirus
3. Cause of many diseases such as AIDS, Polio, Mumps, Herpes
4. Viruses have two cycles; they can be in the lysogenic cycle causing no signs of
illness and then go into the lytic cycle and cause an outbreak of the disease.
AIDS and Herpes act like this.
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Cell reproduction or division (Mitosis)—A. Cell starts with 2N (diploid) number of
chromosomes, B. the chromosomes (contain DNA) are replicated to become 4N, C. the
chromosomes and cytoplasm divide to produce 2 smaller 2N daughter cells.
Part 3: DNA Structure and Function
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DNA is the symbol for deoxyribose nucleic acid.
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In eukaryotic cells it is found in the nucleus of the cell; along with proteins,
it makes up the chromosomes.
Genetic information is stored in the DNA which is located in the nucleus.
The 5 carbon sugar of DNA is where it gets its name from: deoxyribose.
DNA is made up of many nucleotides. Each nucleotide consists of three parts: a 5carbon sugar, a phosphate group, and a nitrogenous base.
The structure, which was discovered by James Watson and Francis Crick (Watson and
Crick), is a double helix. It is like a twisted ladder.
The genetic code is written in the order of the nitrogen bases. The four bases are:
Adenine (A), Thymine (T), Cytosine (C), and Guanine (G). The bases pair together as
follows: A-T and C-G
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The process of copying DNA is called replication. This occurs in both mitosis (cell
division) and meiosis (gamete formation).
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RNA (ribose nucleic acid) is used to carry the DNA message from the nucleus to the
ribosome of the cell where the instructions are carried out (the protein is made). The
specific type of RNA that does this is messenger RNA or mRNA. RNA is different from
DNA because it is single stranded and uses Uracil (U) instead of Thymine (T).
The process of copying the code from the DNA to mRNA is transcription.
For the code to be carried out, the mRNA attaches to a ribosome in the cytoplasm.
Another type of RNA, transfer RNA or tRNA, brings amino acids to the ribosome. They
are attached in the order specified by the codons (3 nitrogen bases) to make a protein.
The process of decoding the message on the mRNA into a protein is called translation.
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Decoding Chart
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You read the chart from left to right; for example, GGC AAU would decode to Gly, Asp
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DNA fingerprinting can be used as an identification tool for people. It is much more
accurate than a traditional hand fingerprint. When a DNA fingerprint is made the
following steps are taken: collection of a sample of DNA, cutting of DNA into fragments
with restriction enzymes, separation of DNA into fragment by electrophoresis on a
gel plate, preparation of the actual fingerprint.
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Example of DNA fingerprints to study:
DNA Electrophoresis
Which child is not the biological child of both parents?
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Based upon the following DNA evidence, who committed the crime?
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Mutations—a change in the DNA of a gene
1. Gene mutations—affect only a gene; if it affects only one nucleotide, it is referred
to as a point mutation.
2. Chromosomal mutations—affect larger segments of a chromosome
3. Significance of mutations—rare because of cell’s self-correcting mechanisms;
can lead to cancer by changing genes that lead to regulation of cell cycle;
production of faulty proteins can lead to genetic disorders; can lead to resistance
of bacteria to antibiotics and insects to pesticides
Part 4: Classical Genetics
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Gregor Mendel is considered to be the father of genetics.
Mendel’s Laws
1. Law of segregation—alleles of the same generation segregate during gamete
formation.
2. Law of Independent Assortment-- the law of independent assortment; during
gamete formation the segregation of the alleles of one allelic pair is independent
of the segregation of the alleles of another allelic pair
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Some Language of genetics:
1. Monohybrid cross.
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Cross involving parents differing in only one trait.
2. Dominant trait.
A trait expressed preferentially over another trait.
3. Recessive trait.
The opposite of dominant. A trait that is preferentially masked.
4. F1 generation.
Offspring of a cross between true breeding plants.
5. F2 generation.
Offspring of a cross involving the F1 generation.
6. Phenotype.
The physical appearance of an organism with respect to a trait, i.e. yellow (Y) or
green (y) seeds. The dominant trait is normally represented with a capital letter,
and the recessive trait with the same lower case letter.
7. Genotype.
The genetic constitution. Yellow seeds are dominant, but yellow seeded plants
could have a genotype of either YY or Yy.
8. Alleles.
The different forms of a gene. Y and y are different alleles of the gene that
determines seed color. Alleles occupy the same locus, or position, on
chromosomes.
9. Homozygous.
Both alleles for a trait are the same. They can be homozygous dominant (YY), or
homozygous recessive (yy).
10. Heterozygous.
Differing alleles for a trait, such as Yy.
11. Dihybrid cross
Cross between parents involving 2 different traits
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Monohybrid cross
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Dihybrid cross
Female Gametes
GW
Gw
gW
gw
GGWW GGWw GgWW GgWw
GW (Yellow, (Yellow, (Yellow, (Yellow,
round) round)
round) round)
Male
Gametes
GGWw GGww GgWw Ggww
Gw (Yellow, (Yellow, (Yellow, (Yellow,
round) wrinkled) round) wrinkled)
GgWW GgWw ggWW ggWw
gW (Yellow, (Yellow, (Green, (Green,
round) round)
round) round)
GgWw Ggww
ggWw ggww
gw (Yellow, (Yellow, (Green, (Green,
round) wrinkled) round) wrinkled
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How to determine the gametes in a dihybrid cross:
Exceptions to simple inheritance
1. Incomplete dominance—neither allele shows complete dominance over the
other; the resulting heterozygote will show an in between phenotype; ex. red and
white “four o’clock”flowers produce a pink hybrid
2. Codominance—both alleles are dominant; ex. sickle cell anemia; the herozygote
contains both alleles; this provides an advantage as these people do not get
malaria
3. Polygenic inheritance—more than one gene controls the trait; ex. eye color,
skin color
4. Multiple alleles—more than two alleles are possible; ex. human blood groups
with A, B, and O alleles
5. Sex-linked inheritance—the trait is carried on one of the sex chromosomes,
usually the X; ex. Hemophilia, Color blindness, Duschenne Muscular Dystrophy;
usually males inherit the trait more than females because they only have one X
chromosome.
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Meiosis—this process is for gamete (egg and sperm) formation; meiosis occurs only in
sexually producing organisms; it starts with a diploid (2N) cell and ends with haploid cells
(1N) which are the egg (oocyte) or sperm (spermatid) cells.
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Crossing over—during meiosis, chromosomes cross over and exchange genetic material;
this leads to variation in gene combinations
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Nondisjunction—during meiosis, the chromosomes do not always separate properly;
this can result in the egg or sperms having fewer or more chromosomes than is normal;
this leads to diseases such as: Down Syndrome (extra chromosome #21), Turner’s
Syndrome (female with only 1X), Kleinfelter’s Syndrome (males with an extra X—XXY).
Karyotypes can show this:
Normal
Down Syndrome
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Part 4: Evolution
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Charles Darwin developed the theory of evolution by natural selection.
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Evolution is a process that where a change is the gene pool occurs over time. The
process may be very slow (gradualism) or occur in spurts (punctuated equilibrium).
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In order for natural selection to occur, the following must happen:
1. Variation in offspring
2. Overproduction of offspring
3. Competition (struggle for survival)
4. Differential survival and reproduction (survival of the fittest)
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Evolution can occur due to mutations (changes in the structure of DNA) and gene
shuffling; these can make an organism better able to survive in its environment. This
type of change is called an adaptation. The most important advantage that an
adaptation gives a living thing is to help it survive so that it can reproduce. Evolution by
natural selection produces organisms that are better adapted to their environment.
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There is a great deal of evidence for evolution. One example is found in the present
with the evolution of bacteria that are resistant to antibiotics—remember the video on
the TB in the Russian prisons? Other evidence includes: biochemical similarities in
organisms, homologous structures, vestigial structures (structures we have, but no longer
use such as the appendix), embryological similarities, and fossils. All of these point to
common ancestry.
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Part of understanding evolution is a knowledge of speciation, the evolution of new
species. A species is defined as organisms that can produce fertile offspring—
fertile means that they can also reproduce. The horse and donkey are not members
of the same species because their offspring, the mule, is not fertile—cannot produce
offspring. Speciation usually occurs when a population gets separated (such as
geographically by a river or canyon) into two or more groups for long periods of time.
During this time each group accumulates mutations that eventually prevent them from
being able to reproduce with the other group. This is divergent evolution.
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Biological fitness refers to an organisms ability to survive and reproduce.
Part 4: Classification
 Taxonomy—The science of naming organisms. Developed by Carl Linneaus; organisms
are grouped by common characteristics and similarities. Now we include genetic
similarities, as well. Taxonomic levels include (starting from the most general): Domain,
Kingdom, Phylum, Class, Order, Family, Genus, species. (Did King Philip come over for
good spaghetti?)
 Binomial nomenclature—2 naming system; each species has a genus name that is
capitalized and a species name that is not. Latin words are used so that scientists
understand each other world wide. Organisms with the same genus name show
close common ancestry! Example: Canis familiaris (the dog) and Canis lupus
(the wolf) are close relatives. The scientific name of an organism includes the Genus
and species name; an example is humans are referred to as Homo sapiens.
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GROUP
NAME
ORGANISM
HOUSE
CAT
LION
HOUSEFLY
Animalia
Animalia
Animalia
Animalia
HUMAN CHIMPANZEE
KINGDOM Animalia
PHYLUM
Chordate
Chordate
Chordate Chordate Arthropoda
CLASS
Mammal
Mammal
Mammal
ORDER
Primates
Primates
FAMILY
Hominidae
Pongidae
Felidae
Felidae
Muscidae
GENUS
Homo
Pan
Felis
Felis
Musca
SPECIES
sapiens
troglodytes
domestica
leo
domestica
Scientific
Name
Homo
sapiens
Pan
troglodytes
Felis
Felis leo
domestica
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Mammal
Carnivora Carnivora
Insect
Diptera
Musca
domestica
In the above chart, you can see that the Lion and House Cat show the closest
evolutionary relationship because they are members of the same Genus.
Organisms can be identified using a dichotomous key.
Organisms are placed into 6 kingdoms: Archaebacteria, Eubacteria, Protista, Fungi,
Plantae, and Animalia. The kingdoms are placed in 3 domains based upon evolutionary
relationships: Bacteria, Archaea, and Eukaryota
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The presence or absence of a cell wall, as well as its composition, is also important in
assigning an organism to a kingdom. Only members of the animal kingdom have no cell
wall!
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Bacteria
1. Shapes
2. Disease causing are called pathogens (viruses, some Protista and some Fungi are
also pathogens).
3. Diseases caused by Bacteria
4. Antibiotics kill bacterial but not viral infections. The picture below shows the effect of
various types of antibiotics on bacteria growing in a Petri dish.
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5. Bacteria can also be useful
a. Decomposers
b. Digestion
c. Manufacturing
d. Food production—yogurts, cheese, etc.
e. Using E. coli to produce human insulin
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Part 5: Body Systems
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Part 6: Plants
 Plants have the following characteristics:
1. Multicellular
2. Eukaryotic cells
3. Autotrophic (make their own food) by photosynthesis
Light + 6CO2 + 6H2O
C6H12O6 +6O2
4. Cell wall of cellulose
5. Alternation of generations
Plants have a life cycle in which a haploid plant that makes gametes (a
gametophyte) alternates with a diploid plant that makes spores (a
sporophyte). This is known as alternation of generations. In nonvascular plants,
the gametophyte is dominant and in vascular plants, the sporophyte is larger.
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Plants are classified by the presence or absence of vascular tissue. This tissue
forms “tubes” that carry water and minerals (xylem) and nutrients (phloem).
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Plants with no vascular tissue are the Bryophytes which are the mosses and
hornworts. They must live in a moist environment.
Plants with vascular tissue are the Tracheophytes. They have “true” roots, stems,
and leaves. Three key structures of tracheophytesa are the roots, stems, and leaves.
1. Roots—anchor the plant in the ground and absorb minerals and water from the
ground
2. Leaves—absorbs sunlight for photosynthesis and is the location for that process
 Cuticle—protective, waxy coating on the epidermis of the leaf
 Palisade layer—most of the photosynthesis takes place here
 Stomata—openings in the leaf surface that allow for the exchange of gases;
surrounded by guard cells to control opening and closing
3. Stems—to hold the plant upright so that the leaves get sunlight; contain xylem (carries
water and minerals up from the roots) and phloem (carries food from the leaves to the
rest of the plant).
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Examples of tracheophytes are the gymnosperms (cone bearing), ferns, and
angiosperms (flowers and fruits).
gymnosperm
fern
angiosperm
“naked seeds”/
seeds in cones/
conifers
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moisture needed
for reproduction/
spores/ no seeds
90% of all plants
flowers/ fruit/
dicots and monocots
The flower is the reproductive organ of the angiosperm. The cone is the
reproductive organ of the gymnosperm.
The process of getting the male gamete to the female ovule is called pollination.
Flowers may contain both male and female parts or their can be separate male and
female flowers. The following picture shows a flower with both structures:
Female
Male
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When flowers are separate sexed or have a male part lower than the female part,
they must rely on insects for pollination. Observe the flower below; note the big ball
of pollen on the bees leg.
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Pollination results in the formation of a seed. The seed in angiosperms is evolved to
be enclosed in a fruit. The fruit is designed to protect the seed which contains the
developing embryo. The embryo of the plant does not use the fruit for food. Each
seed contains one (monocot) or two (dicot) cotyledons that store food for their
nourishment. Here is a diagram of a dicot seed; only one cotyledon is pictured here.
This is like the peanut that you saw in lab.
embryo
cotyledon
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Fruits aide the seed in dispersal so that it will have room to grow and develop away
from the parent plant. See example below:
wind dispersal
wind
dispersal
Prickles stick to
animals that carry
seeds to other places.
Animals eat fruit
and drop seeds in
feces in different
locations.
Part 7: Ecology
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Ecology is the study of the ways that organism interact with each other (biotic
factors) and their physical environment (abiotic factors).
A food chain traces one pathway of energy flow through an environment. It must
always have a producer at the bottom or beginning of the chain. The produce
(which is going to be a plant in a terrestrial food chain) captures the suns energy and
changes it into chemical energy that other organisms can use. The process of doing
this is known as photosynthesis. The organism that eats the produce is called a
primary consumer or herbivore. The organism that eats the primary consumer is
called the secondary consumer or carnivore. Some organisms are herbivores and
carnivores. We call these organisms omnivores. The chain can go up to 3y and 4y,
but usually does not go any further because the energy of the chain is used up by the
organisms. A food chain must also have a decomposer; these organisms, which
can be bacteria, fungi, and/or scavengers, help to recycle the nutrients back into the
environment so that they can be reused. The energy is lost to the system and must
be brought in anew by the producers usually via photosynthesis.
Here is an example of a food chain:
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A food web shows how all of the food chains in an environment interact together.
Note: the arrows point in the direction of energy flow or “who is eating who”. Also note that
organisms play more than one role. For example, the skunk is a primary consumer
when it eats the vegetation, a secondary consumer when it eats the insect, and a tertiary
consumer when it eats the lizard.
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The following diagram represents ecological pyramids:
An energy pyramid shows us that there is more energy available for organisms at the
bottom of the food chain. As you go up each trophic level or tier, there is only about 10%
energy available for the next level. This puts a limitation on how many levels you can
have. Notice that the numbers of organisms all decrease as you go up each level. This
is because of the limited amount of energy in the form of food that is available for these
animals. The energy is not destroyed but changed into another form of energy such as
heat.
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Biological magnification—the effect if toxins in the environment are magnified as you
go up the food web so that 3y and 4y consumers are harmed the most.
Concentrations of DDT in an aquatic food chain
In any natural environment there is a regular progression of species replacement as time
passes. This continues to happen until a climax community of organisms is reached.
This process is called succession. The pictures below show progression in a
community after a fire.
The following diagram shows how a bare field progresses over time to become a
climax forest:
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Symbiosis refers to the relationships that organisms have with each other. There are 3
main types of symbiotic relationships.
1. Mutualism—both organisms help each other (i.e. the clown fish and the sea
anemone; lichen= algae and fungus)
2. Commensialism—one organism is helped and the other is not affected (i.e. the
remora attaching to the shark to get food; the shark is not effected.
3. Parisitism—one organism is helped while the other organism is hurt or harmed
(i.e. a tape worm getting into your digestive system and making you sick
Heart worm parasite in a sheep heart
Reference this addition to page 15, “Part 4: Classification”.
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