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Biology
Keystone Exam SG
Name ______________________
Date ___________________
Chapter 1 (Introductory Material)
1. The theory of biogenesis states that . . .
2. The lower the magnification, the ________________ the resolution.
3. The changeable part of any experimental design is the __________________________.
4. Cellular suspensions can be separated by spinning them at high speeds. This process is called ____________________.
5. Which of the following would be considered quantitative?
a. shape of a tree’s leaves
b. height of a tree
c. consistency of a tree’s sap
d. texture of a tree’s bark
6. Which of the following would not be considered a characteristic of life?
a. An elephant’s life span is about 70 years.
b. Elephants will encircle their young when danger threatens.
c. An elephant consumes about 5% of its body weight per day.
d. An elephant weighs between 3.5 and 6.5 tons.
7. Which of the following is not a biotic factor?
a. The Atlantic hurricane season is from June 1 to November 30.
b. The 2005 Atlantic hurricane season caused about 2300 deaths.
c. Hurricane Katrina devastated Louisiana’s sugar cane crop.
d. A large number of people died as a result of bacterial infections following Hurricane Katrina.
8. Which scientist first challenged the theory of spontaneous generation? _______________
9. ________________ ___________________ irrefutably disproved spontaneous generation.
10. In what year was spontaneous generation finally disproved? _____________
11. Pasteur let his experiment sit for a year. Why did he do this?
12. What problem did supporters of spontaneous generation have with Spallanzani’s experiment?
13. This is made when using past knowledge, information, and observations: _____________________
14. Process of breaking cells apart: __________ _________________________
15. Identification tool that utilizes two contradictory statements: ________________________ __________
16. Group in an experiment that does not receive the item being tested: _________________
17. Belief that states life arises from nonliving material: ________________________ ________________________
18. Know the characteristics of life. They are:
a. All forms of life contain carbon as their base element.
b. The molecule that controls all inheritance patterns and cellular functions is DNA.
c. All life needs energy to survive.
d. All organisms exhibit stimulus-response reactions.
e. All organisms must remove waste products (excretion).
f. All organisms must reproduce to carry on life.
g. All organisms exhibit a life span.
h. All organisms are affected by biotic and abiotic limiting factors.
Chapter 2 (Biochemistry)
1. The pH range for an acid is ____ to _____. The pH range for a base is _____ to _____.
2. If a compound has a suffix of “-ine”, it is an ________________ ___________.
3. If a compound has a suffix of “-ose”, it is a _______________________.
4. If a compound has a suffix of “-ase”, it is an _______________________.
5. The three elements that make up a carb are _______________, ________________, _______________.
6. Give the monomers of the following biomolecules (macromolecules):
a. protein ____________ _________
c. carb ________________________
b. nucleic acid ___________________
d. lipid _______________, ____________ ________
7. _________________ are transferred in ionic bonds and shared in ___________________ bonds.
8. The ratio of C to H to O in most carbs is ___________.
9. A substance that can dissolve another substance is a __________________________.
10. The substance that gets dissolved is a ____________________________.
11. The combination of the two is called a ____________________________.
12. Monomers make up ______________________________.
13. In a solution, an acid increases the ________ ion concentration, while a base increases the _______ ion concentration.
14. A protein that lowers the activation energy of a chemical reaction: ___________________
15. The ability of water to move upward against the force of gravity is called __________________ _____________.
16. The area of the enzyme where the substrate is catalyzed is called the _______________ ____________.
17. A __________________________ neutralizes strong acids and bases.
18. An enzyme will _______________________ if it’s exposed to high temperatures, strong acids/bases, or pressure extremes.
19. CHONS _______________ CHO _______________, _______________ PONCH _______________ _________
20. Attraction between different substances: _________________________ Same substances? ______________________
21. The splitting of polymers into monomers is accomplished by the process of _____________________, while the building up
of polymers from monomers is accomplished through the process of _______________________ _________________.
Chapter 3 (Ecology)
1. ________ = the percentage of energy that is passed on from one trophic level to the next.
2. Bacteria convert nitrogen from the air into nitrates and nitrites through the process of ___________________
___________________.
3. Organisms that can produce their own food are called _____________________.
4. Organisms that cannot produce their food are called _______________________.
5. Identify the following ecological pyramids:
a. amount of living tissue____________________
b. quantity of organisms ____________________
c. displays amount of heat lost (often in Calories) __________________
6. Linear representation of the flow of energy from one organism to another is a __________ ______________.
7. A more complex representation showing the network of energy flow within a community is a __________ ______.
8. ________________________ is the process of producing food from chemical compounds.
9. Identify the following levels of the biosphere:
a. organisms that can interbreed and produce fertile offspring _____________
b. different groups of organisms living together __________________
c. groups of ecosystems that have the same climate ________________
d. group of the same species __________________
e. contains both biotic and abiotic parts of a given area ____________________
10. Identify the following consumers:
a. eats plants and animals _________________
b. eats only plants ____________________
c. eats only meat __________________
d. break down organic matter _________________
e. absorb chemical compounds from dead organisms ___________________
11. The process of converting nitrates into nitrogen gas is ____________________________.
12. A large deposit of a limiting nutrient in a water ecosystem may cause an ______________ ________________.
13. A _________________________________ cycle is a process in which matter is passed from one organism to another and
from one part of the biosphere to another.
14. A close long-term relationship between two species: ______________________.
15. The three types of symbiosis are: ____________________, ____________________, and ____________________.
Chapter 7 (Cells)
1. There are many kinds of _____________________ in cell membranes; they help move material into and out of the cell.
2. The FIRST person to observe cells was ________________ _________________.
3. The organelle that contains DNA and RNA _________________________.
4. The two major regions of eukaryotic cells are the _______________________ and the __________________________.
5. The modern view of the plasma membrane structure is the ________________ ________________ _______________.
6. Organisms whose cells do not contain a nucleus are called __________________________, and they are all species of
_______________________ and _____________________.
7. Organisms whose cells do contain a nucleus are called ___________________________.
8. Suspended in the cell's cytoplasm are _______________________, the structures that carry out all of a cell’s functions.
9. Whip-like structures made of microtubules used for cell locomotion: ____________________
10. The organelle that digests molecules, old organelles, and foreign substances in the cell: ________________________.
11. The first person to observe living microorganisms was _____________ _______ ________________________.
12. Short, hairlike organelles that can move and may cover a unicellular organism or act as a filter in the respiratory tract are
called ________________________.
13. The statement "Cells arise only from existing cells" is part of the ______________ _____________________. This
statement was first made by Rudolf ___________________.
14. The system of protein fibers that supports the shape of the cell is called the _____________________________.
15. Matthias Schleiden studied ___________________ cells, and Theodor Schwann studied ____________________ cells.
16. A plasma membrane is said to be ________________________ permeable because it allows the passage of some solutes
and not others.
17. Why must a cell’s organelles, like the Golgi, mitochondria, and ER, to be a complex of tightly folded membranes?
18. What are the three statements of the Cell Theory?
19. A cell that requires a lot of energy (like a muscle cell) would possess a large number of which organelle? Why?
Chapter 7 (Cell Transport)
1. Identify the following types of solutions:
a. Concentration of solutes outside the cell is greater than inside ______________________
b. Concentration of solutes outside the cell is less than inside ________________________
c. Concentration of solutes inside and outside the cell is equal ________________________
2. A __________________________ _____________________ is the concentration difference across a space.
3. The movement of substances without any input of energy but requires “helper” proteins is called
________________________ ________________________.
4. The movement of substances from areas of high concentration to areas of low is called ___________________.
5. If the molecular concentration of a substance is the same, the substance is in ____________________________.
6. Excessively hypotonic solutions will cause animal cells to burst, a process called __________________________.
7. ____________________________refers to the rupturing of cells because of dehydration.
8. Transport that requires the cell to expend energy is called __________________ ______________________.
9. Identify the following types of active transport
a. Movement of substances out of a cell _________________________
b. Movement of liquids into a cell ____________________________ (“cell drinking”)
c. Movement of solids into a cell _____________________________ (“cell eating”)
d. Movement of solid or liquid into a cell ____________________________
10. The diffusion of water through the cell membrane is called ___________________.
11. ____________________ is the most common solvent in cells.
12. Transport that requires no energy expenditure is called __________________ ___________________.
13. Protein channels that assist in the transport of water through the cell membrane are called _______________________.
14. Organelles involved the most in exocytosis: _______________ __________________ and _________________
15. The random motion of all particles named after the Scottish botanist Robert Brown is called _____________________
________________________.
16. ___________ ____________________ are protein passageways in the cell membrane that allow the passage of charged
particles/molecules.
17. _______________ ___________________ refers to the water pressure within plant cells.
18. Identify the solutions as either hypertonic, hypotonic, or isotonic:
Chapter 8 (Photosynthesis)
1. Nearly all organisms use an energy storage molecule called ____________________ ______________________ or simply
_______ to carry out their life processes.
2. Disk-shaped structures with photosynthetic pigments are known as _______________________.
3. A molecule that can absorb certain light wavelengths and reflect others is a ___________________.
4. The 2 most common photosynthetic pigments in plants are ________________________ ____ and _____.
5. __________________ is a gel-like matrix (a solution) that surrounds the thylakoids.
6. Photosynthesis occurs in two stages called the ____________ - __________________ ________________ and the
_______________ __________________.
7. Chlorophyll reflects which color? _________________________
8. Folded thylakoids that resemble stacks of pancakes are called _______________________.
9. The enzyme that adds a phosphate group to ADP is called _________ ________________ to form _________.
10. Scientist who first described the electron transport chain: _________________ __________________
11. Discovered that most of a plant’s mass is derived from water: _______ _______ _______________
12. Discovered how carbon forms glucose: _________________ _________________
13. Joseph Priestly discovered that plants release ______________________.
14. H+ ions are moved into the thylakoid using energy from ___________________ as they move down the ___ ___ ___.
15. Where in the chloroplast do the light-dependent reactions occur? _____________________
16. Where in the chloroplast do the reactions of the Calvin cycle occur? ___________________
17. The chemical equation for photosynthesis: __________________________________________________________
18. The abundance of oxygen in Earth’s atmosphere is a direct result of the breakdown of ______________ in the
___________-_________________ reactions.
19. ___________ carries electrons from the light-dependent reactions to the ____________ ______________.
20. Photosynthesis occurs in what organelle of plants and algae? _______________________
Chapter 9 (Cellular Respiration)
1. Cellular respiration in the presence of oxygen is called ________________ ______________________.
2. What is the scientific unit of energy required to raise the temperature of 1 gram of water 1 degree Celsius? ____________
3. What is the first pathway of cellular respiration called? _______________________
4. The absence of oxygen is called _____________________________.
5. Where in a cell does glycolysis take place? ________________________________
6. The processes of glycolysis and the two anaerobic pathways are called _________________________________.
7. The breakdown of organic compounds to produce ATP is called __________________ _______________________.
8. Glycolysis begins with __________________ and produces ____________________ acid.
9. Where in a mitochondrion do the reactions of the Krebs cycle occur? _____________________________
10. Where in a mitochondrion is the ETC located? _____________ _____________________
11. The equation for aerobic cellular respiration:__________________________________________________________
12. The buildup of _______________ ___________ causes temporary muscle soreness after strenuous exercise.
13. Most of the chemical energy in glucose (62%) is released as __________ from our bodies.
14. Aerobic cellular respiration produces _______ ATP molecules per glucose molecule.
15. What is the process by which glucose is converted into pyruvic acid? _______________________________
16. The conversion of pyruvic acid to carbon dioxide and ethanol is called ____________________ __________________.
17. How efficient is aerobic respiration? _______%
18. In cellular respiration, more energy is produced in the __________ than in any other pathway.
19. What is the purpose of electrons as they are transported along the electron transport chain?
20. In aerobic cellular respiration, acetyl-CoA combines with a four-carbon molecule to form citric acid as part of the
_____________ _________________.
21. The element ___________________ dictates which metabolic pathway follows glycolysis.
22. The names of the pathways that take place when organic compounds are broken down in the absence of oxygen are
______________ ___________ _______________________ and _________________ _________________________.
Chapter 10 (Cell Division)
1. ______________________ are proteins that control the cell cycle.
2. In eukaryotic cells, __________________________ takes place after the nucleus divides.
3. ________________ condenses into chromosomes of two sister ____________________, joined together by the
_____________________ during __________________________.
4. Microtubules that extend from the poles of a cell to the centromeres on chromosomes during cell division are called
_________________ ___________________.
5. The sequence of events that occurs in a cell from one mitotic division to the next is called the _________ ____________.
6. The group of diseases caused by uncontrolled cell division is called __________________________.
7. A protein disk that attaches two chromatids to each other in a chromosome is called a _____________________.
8. During the G2 phase, ____________________ and _____________________ needed for mitosis are produced.
9. The stages of mitosis in order are ______________, ______________, ______________, and ______________.
10. Interphase consists of what three phases? Describe each.
a.____________ ___________________________________________________________________________
b.____________ ___________________________________________________________________________
c.____________ ___________________________________________________________________________
11. Chromatids separate from each other during __________________________________.
12. The cell cycle consists of the three general periods: ________________, _______________, and ________________.
13. A chemical compound that causes cancer is called a ___________________________________.
14. Chromosomes line up along the center (equatorial plate) of the cell during _____________________________.
15. During __________________________ the cytoplasm pinches in half.
16. Tumor cells that do not spread to other body tissues are called ______________________. Cancerous tumor cells that do
spread (via the blood and lymph) are called ___________________________________.
17. During cell division, plant cells form a _____________ ___________________ in the center of the cell.
18. Human somatic (body) cells contain _______ chromosomes.
19. How many chromosomes are in a daughter cell whose parent cell had 56 chromosomes? ________
20. As a cell increases in size, its ____________________ increases more rapidly than its _______________ __________.
21. Chromosomes are rod shaped structures made of ___________ and ____________________.
Chapter 11 (Genetics)
1.
.
8.
Offspring that are the result of mating between two genetically different kinds of parents--the
opposite of purebred.
The study of gene structure and action and the patterns of inheritance of traits from parent to
offspring. This is the branch of science that deals with the inheritance of biological characteristics.
A 19th century central European monk-scientist who published his ideas about genetics in 1865 but
largely went unrecognized until 1900, which was 16 years after his death. He acquired his
understanding of genetics mostly through pea plant breeding experiments.
Offspring that are the result of mating between genetically similar kinds of parents--the opposite of
hybrid.
Units of inheritance usually occurring at specific locations, or loci, on a chromosome. These units
are responsible for hereditary characteristics in plants and animals.
Alternate forms of the same gene. Because they are different, their action may result in different
expressions of a trait.
The genetic makeup of an individual for a trait or for all of his/her inherited traits—not the
observable or detectable characteristics.
A genotype consisting of two identical alleles of a gene for a particular trait.
9.
A genotype consisting of two different alleles of a gene for a particular trait.
10.
The observable or detectable characteristics of an individual organism; the detectable expression
of a genotype.
The general term for an allele that masks the presence of another allele in the phenotype.
The general term for an allele that is masked in the phenotype by the presence of another allele.
Gregor Mendel's principle of genetic inheritance stating that, for any particular trait, the pair of
genes of each parent separate (during the formation of sex cells) and only one gene from each
parent passes on to an offspring.
Gregor Mendel's principle of genetic inheritance stating that different pairs of genes are passed to
offspring independently so that new combinations of genes are possible. In other words, the
distribution of one pair of alleles does not influence the distribution of another pair.
2.
3.
4.
5.
6.
7.
11.
12.
13.
14.
15.
A simple graphical method of showing all of the potential combinations of offspring genotypes that
can occur and their probability given the parent genotypes. Named after Reginald Punnett.
16.
The general term for the study of inheritance patterns which can be explained by simple rules of
dominance and recessiveness of genes. Named after the monk scientist who first described it.
A trait that is determined by the combined effect of more than one gene. Human skin and hair
color are examples.
The inheritance pattern in which a trait is expressed in the phenotype of heterozygous individuals
as an apparent blend or an intermediate expression. For instance, in primroses pink flowers result
from the cross between red and white flowers.
The inheritance pattern in which two different alleles for a trait are expressed unblended in the
phenotype of heterozygous individuals. Type AB human blood is an example.
An inheritance pattern in which a gene has more than two alleles. The human ABO blood type
system is an example. It is controlled by at least 3 alleles.
17.
18.
19.
20.
*I’m fairly certain that there will also be a few Punnett square problems on the test
Chapter 11 (DNA and RNA)
1. In __________, James ___________ and Francis ______________ discovered the double-helix structure of DNA.
2. DNA is a long molecule made up of subunits called ____________________. (Nucleotides are the monomers of
________________ ___________.)
3. DNA nucleotides are made of three basic components: a 5-carbon sugar called ____________________, a phosphate group
and a nitrogenous base.
4. The deoxyribose and phosphates make up the “_________________” of DNA while the nitrogenous bases make up the
“_____________” of the DNA ladder.
5. There are four nitrogenous bases: ________________, _________________, ________________, and
____________________.
o Adenine and thymine always pair up; cytosine and guanine always pair up.
6. DNA is copied through a process called _____________________. During replication, the DNA molecule separates into two
strands, then produces two new strands.
7. The principal enzyme involved in replication is _________ ______________________. It “proofreads” each new DNA strand
to make sure that each new copy is ______________________ to the original.
8. RNA is similar to DNA, but it has three main differences: the sugar in RNA is _______________, RNA is a _______________
helix, and RNA contains _____________ in place of _________________.
9. RNA has one main job – _________________ ___________________!
10. The strand of RNA contains the info needed to assemble __________________; it’s like an instruction manual.
11. There are three main types of RNA, all of which are involved in protein synthesis: _____________________ RNA (mRNA),
___________________ RNA (rRNA), and __________________ RNA (tRNA).
12. New RNA molecules are produced from nucleotide sequences of DNA in a process called __________________.
o ________ _________________________ is the principal enzyme involved in this process.
13. The readers of the instruction manuals are the _____________________. The ribosomes read the instructions (RNA
molecules) and then make the necessary ___________________ through a process called _________________________.
14. Process that converts DNA to RNA: _________________________________
15. Nucleotide sequence that codes for the production of proteins: ____________; does NOT code for proteins __________
16. Sequence of three bases that form the “words” to make amino acids; mRNA carries them: _________________
17. In summary, DNA and RNA contain information for making not much else except ___________________. DNA is the
“master plan” while RNA is the “blueprint.” The “job sites” are the ribosomes. The finished products are proteins.
18. Name the chromosomal mutations!
a. reverses the direction of parts of chromosomes _________________
b. loss of all or part of a chromosome ________________
c. part of one chromosome breaks off and attaches to another ________________
d. extra copies produced __________________
* Study gene mutations (substitutions/missense, insertions, deletions, silent, and nonsense) and know that insertions
and deletions are frameshift mutations.
* Also, look over the Codon Wheel.
Chapter 14 (Human Genetics)
1. The chromosomes that determine gender are called __________ chromosomes, while the non-gender determining
chromosomes are called ____________________.
2. Our complete set of genetic information is called the ________________ ___________________.
3. Name the blood type along with its Rh factor designation:
iiRr _____
IAIArr _____
IAIBrr _____
IBIBrr _____
4. Diseases such as PKU and Tay-Sachs only appear if the individual has all _____________________ alleles.
5. The most common error in meiosis is _______________________________, which refers to homologous
___________________________ failing to ___________________________.
6. A female who has inherited only one X chromosome has ______________________ syndrome.
7. A male who has inherited one or more extra X chromosomes has _________________________ syndrome.
8. The process of replacing a faulty or absent gene with a functional one is called _____________ ___________________.
9. ________ ___________________________ has become a powerful tool in the justice system.
10. A diagram that shows an individual’s chromosomes is a __________________________.
11. A diagram that follows the inheritance of a trait through several generations of a family is a _______________________.
12. A trait that results in an overwhelming majority of shaded squares on a pedigree can be described as _________________________.
13. All sex-linked disorders occur on the ______ chromosome because it is the larger of the two sex chromosomes.
14. An individual with three copies of the 21st chromosome has ______________ syndrome.
15. An X chromosome that is inactive is called a ___________ body.
16. ________% of sperm cells carries a Y chromosome.
17. The failure of homologous chromosomes to separate during meiosis is called __________________________.
18. A researcher observed numerous misshapen and improperly folded membrane proteins in a lung cell sample. The
individual from which this cell sample came most likely has ________________ ________________.
19. The disease that results in misshapen red blood cells is called _______________ _______ _____________.
20. Sex-linked disorders are more often found in __________ because they have only one X chromosome.
21. Klinefelter, Turner, and Down syndromes are all the result of ___________________________.
22. Fathers determine the sex of children because . . .
Chapter 19 (Microbiology)
1. A _______________________ is a disease-causing agent, often a bacterium or virus.
2. Regarding their cell wall, prokaryotes are divided into two broad categories. They are ___________-_______________ and
____________-____________________.
3. Bacterial cell walls are quite different from plant cell walls. Plant cell walls are primarily made of ___________________,
while bacterial cell walls are made of _________________________.
4. The first person to show that bacteria cause disease was ________________ _______________.
5. The main form of prokaryotic division is called __________________ ____________________.
6. Many species of archaebacteria live in extremely ___________________ ____________________.
7. In the lysogenic cycle, the viral DNA _______________________ along with the host cell DNA.
8. A vaccination induces the body to produce ________________________ against an _________________.
9. A bacterium that cannot tolerate oxygen is described as being an _______________________ ___________________.
10. Viruses that infect bacteria are called _____________________________.
11. Prions are infectious particles composed only of ________________________.
12. A typical virus is composed of a core of ____________ or ____________ surrounded by a ___________________ coat.
13. A bacterium that requires oxygen in order to complete it metabolic processes is described as being an
_______________________ ___________________.
14. In the lysogenic cycle, the bacteriophage _____________________________ its DNA into the DNA of the
_______________ _____________.
15. A _______________________ is a poisonous substance released by many species of bacteria.
16. The three main shapes of bacteria are ___________________, ____________________, and
________________________.
17. A substance that induces an organism’s immune system to produce antibodies is called an ______________________.
18. The protein coat around a virus is called a ________________________.
19. A bacterium that can live and grow with or without oxygen is described as being a _______________________
___________________.
20. The viral replication cycle that leads to the eventual bursting of the host cell is called the ______________________
____________________.
Plants
1. _________________________ are hormones produced in the apical meristem that stimulate cell elongation.
2. Specialized epidermal cells that control transpiration are called _________________ ____________.
3. The __________________________ is a thick waxy layer that prevents H2O loss and protects the plant.
4. The ________________________ ________________________ is found at the tips of roots and stems. It is the site where
_______________________ occurs.
5. _______________________ are tubes that transport ________________________, while ____________________
transports _______________________ and __________________________.
6. Small openings between guard cells are called _________________________. They regulate the transport of
_____________.
7. Plant growth and development are controlled by ____________________________.
8. The roots of desert plants have an unusually high number of hairs. This greatly increases the H2O-absorbing
______________________ ______________ of the roots.
9. So that aquatic plants can spread out in the environment, they produce seeds that can __________________.
10. During the cold season, _______________________ and _______________________ are pumped down into
_______________ for storage over winter.
11. Salt-tolerant plants have membrane _____________________ that pump excess _________________ out of their cells.
12. In which biome are epiphytes most commonly found? ____________________________________
13. Match the tropisms!
_____ hydrotropism
_____ gravitropism
_____ thigmotropism
_____ phototropism
A. response to touch
B. response to light
C. response to H2O
D. response to gravity
14. Match the plant groups!
_____ carnivorous
_____ aquatic
_____ parasitic
_____ epiphytes
_____ desert
_____ salt-tolerant
A. have very reduced leaves, such as needles
B. grow on the bodies of other plants, but don’t harm them
C. grow in hypertonic environments
D. grow in wet and acidic soils that lack nutrients
E. can’t really photosynthesize, so they live off of other plants
F. grow in mud that is nearly devoid of O2
15. Match the hormones!
_____ gibberellins
_____ auxins
_____ cytokinins
_____ ethylene
A. stimulates fruit to ripen
B. cause increase in the size of stems, fruits, and flowers
C. cause dormant seeds to sprout; initiate mitosis
D. responsible for most of the tropisms
Evolution
 The theory of evolution has been described and presented in various ways since ancient times. (The ancient Greek
philosopher Aristotle wrote about “The Great Chain of Being” – a chain that depicted the progression of life from simple
to complex.)

The modern theory of evolution was first devised by Charles Darwin and was presented in his book On the Origin of
Species, published in 1859.

In this book, Darwin presented his idea of evolution, which was based upon his 5-year voyage around the world (18311836).

He stated that all forms of life have arisen from a simple single-celled life form that existed billions of years ago. Since
then, life has gradually evolved and changed into the millions of different life forms in existence today.

Evolution is a universal, continual, and never-ending process. In other words, it occurs anywhere in the universe where
life is present. Also, millions of years from now, nearly all of the species in existence today will have vanished and
been replaced by new species.

What has caused this evolution? According to Darwin, it was the struggle for existence, aka, “survival of the fittest”, or
natural selection.

Natural selection is the force that leads to the selection of beneficial mutations while simultaneously eliminating
deleterious ones, thereby strengthening a species.

Because of this selection and elimination, subtle changes occur within the species, and, over long periods of time, the
species gradually changes into a new fitter species.

Darwin knew that species adapt and change – he witnessed it in hundreds of species while on his world tour. But he
hadn’t the foggiest idea as to what actually changed within organisms that led to these adaptations. He gave a few
explanations, none of which were correct.

The answer, in a word, is genes! But why didn’t Darwin know? Because Mendel hadn’t published his work yet.
Genetics was a completely unknown branch of knowledge!

Once genetics had been explained and understood, it was realized that the minor changes that occurred in organisms
were mutations.

Important statement ahead…Read carefully!!!

Beneficial mutations are extremely uncommon and rare. This is why such long periods of time (hundreds of thousands
to millions of years) are required for one species to gradually evolve into another.
The process of natural selection causes beneficial mutations to be inherited and deleterious
mutations to be eliminated. This illustrates the union of natural selection and genetics. This
is called Neo-Darwinism or the “modern synthesis”.