Download Review for BCT

Review for BCT
Landa, 2012
Six elements needed for life

CHNOPS

Remember these are in the Carbon
(CO2) , water (H2O), nitrogen (N2 and
NO2 and NO3) cycles. P an S are small
Molecule
Two or more ATOMS bonded together
O2 and CO2 are molecules as is H2O
When two or more DIFFERENT elements
are bound together  its called a
compound.
Organic Molecules

In non-living things: C and H

In living things: C, H , O
Macromolecules (Organic)
Class name
Element Function
s
Carbohydrate C, H, O Monosaccharides: simple
fast energy
Polysaccharides: Short term
energy storage
Examples
Structure:
Carbs can be single
carbon rings (mono.)
or chains of many rings
linked together (poly.)
Lipid
C, H, O
Long term energy storage
Insulation
Waterproofing (plants)
Mono: sugars
(glucose,
fructose)
Poly: starch, fiber
(cellulose)
Fats, waxes, oils
Protein
C, H, O,
N, S
Speeds up chemical
reactions,
Fights infection
Builds structures
Sends chemical messages
Enzymes
Antibodies
Cartilage
Hormones
NOT a chain of
repeated units
Does not form
polymers
Proteins are large
chains of amino acids
that need to be folded
into a specific shape to
work.
Macromolecules (Organic)
Nucleic C, H, O, Stores information
Acids
N, P
on how to make
proteins,
Makes up our
genes (single
recipes for a
protein)
DNA –
master copy
of all genes
RNA – temp
copy of single
gene
Nucleic acids are
chains of
nucleotides
Sequence of
nucleotides
(ATGC) determines
information
Enzymes

What class of organic compounds?
◦ Proteins

Job
◦ Speed up chemical reactions by lowering the
amount of energy needed

Conditions which affect an enzyme.
◦ Temperature, pH, concentration
Enzymes and Structure

Enzymes (folded chains of amino acids)
must
◦ be folded in a specific way (correct 3D
structure) in order for their substrate (the
molecule they are breaking down/linking
together) can fit together with the enzyme
Processes requiring enzymes

ALL chemical process in a living
thing require enzymes

Examples:
photosynthesis, digestion, cell respiration,
mitosis, meiosis. Replication, transcription,
translation…..
Homeostasis

stable internal environment that is regulated
and maintained regardless of what is going
on outside the cells/body

Three conditions that must be maintained
◦ Temperature, pH, chemical levels (glucose in
the blood, sodium, etc)
Functions of Water
Temperature regulation – sweat
 Lubrication – joints




Transportation of nutrients – blood
Senses -in vision/taste/smell/hearing
Medium – for reactions
Regulating flow in/out of cell



Cells regulate the flow of molecules in and out of
the cell using the CELL MEMBRANE (PLASMA
MEMBRANE).
__DIFFUSION____ is the process that moves
solutes from high concentration to low
concentration.
 ___OSMOSIS____ is the process that moves
water from hypotonic (low solute/high water) areas
to hypertonic (high solute/low water) areas
 ____ACTIVE TRANSPORT______________ is a
process that requires energy to move charged ions
through the membrane.
How does the membrane control
flow?

Depends on the size, charge and
solubility (polar or nonpolar) of the
substance.
◦ Small, uncharged and non-polar chemicals
dissolve easily (diffusion/passive transport)
◦ Large, charged and polar molecules need help
of a transport protein and/or energy
(facilitated diffusion or active transport)
How are different molecules used?

Sugars are used by the
____mitochondria__ for cell respiration

Proteins are broken down into subunits
called ____amino acids______ and
used to build new proteins
Cells are made of:

many small structures called
___organelles______________ each of
which has a specific job. List several jobs
performed by the parts of the cells:
When do Cells Divide?
Growth and reproduction
 Repair injury
 Replace dead cells

Replication and DNA

How do cells ensure that the new cells
will have all the same information that the
old cells do?
◦ Copy the DNA using DNA replication
Identical DNA..but different cells????

If the DNA is identical, how do we get
specialized cells?
◦ can use different sets of the genes (within
the same DNA to make different proteins.
◦ Analogy: two people with the same cookbook
can have different dinner parties just by
making different recipes.

The process by which cells become
specialized is called _differentiation_
Why don’t cells get smaller as they
divide?
Because they GROW!!!!!
 After fertilization, what happens to a
zygote?

◦ Must begin to divide through mitosis.

How do cells differentiate?
◦ They “move around” cells in different
chemical environments have different
genes activated (turned on).

What happens if early cells in the embryo
separate? IDENTICAL TWINS
Mitosis and Meiosis

Mitosis
◦ Happens when we need more body cells
◦ Produces two IDENTICAL cells

Meiosis:
◦ Happens when we make reproductive cells
◦ Produces different cells (due to crossing
over/genetic recombination) with ½ as
many chromosomes as a body cell.
# of Chromosomes

Body (Somatic) Cells

Reproductive (Gamete) Cells
◦ ½ as many chromosomes as body cells
◦ Will fuse with another reproductive cell
during fertilization (embryo now has cells that
has a complete set (2N) of chromosomes).
If mistakes during cell division occur

During meiosis, a mistake would lead to
a defect in the entire body of an offspring.

During mitosis, a single body part will
probably be affected
Stem cells vs. Regular body cells

Stem cells are not specialized
(undifferentiated) and have the capacity to
differentiate into any type of cell.

Body cells are already specialized
and can only produce one type of cell
Stem cells

Mostly in embryonic tissue

Some partially differentiated stem cells
are found in body parts (ie bone marrow)

Potential to cure/prevent disease
◦ if we can learn how to direct stem cells to
become specific cell types we might be able to
“grow” organs and repair spinal cord injuries.
Disrupting Normal Body Functions

The structure of the body is necessary to
maintain proper function of the body.
Damaging cells, organs and organ systems
all have a significant impact on how the
organism as a whole functions. For each
of the following describe how it disrupts
the normal functions of the body as well
as possible causes.
Disruption: Mutation
change in the DNA;
 changes the recipe for the protein;
protein may or may not work properly;


Example
◦ : defective enzyme = lactose intolerance
Pathogens
bacteria and viruses;
 destroy cells or compete with our cells
for nutrients in our body; throw off
internal homeostasis

Drugs/Poisons
can alter the effectiveness of proteins in
the body and prevent them from doing
their job;
 can disrupt homeostasis

Sample Problems

Many diseases are caused when the body
cannot digest particular molecules in our
diet. For example, Lactose intolerance is
caused when individuals cannot digest the
sugar found in milk. What type of molecule
is a person missing if they are lactose
intolerant?
◦
◦
◦
◦
Lipid
Monosaccharides
Nucleic Acids
Proteins
Problem 2

Which of the following is NOT made of a
long chain of repeating units called
monomers?
◦
◦
◦
◦
Lipid
Carbohydrates
Nucleic Acids
Proteins
Problem 3

The information on how to make
_____________________ is stored in
the _______________________.
◦
◦
◦
◦
Carbohydrates; Proteins
Proteins; Nucleic Acids
Nucleic Acids; Proteins
Proteins; Carbohydrates
Problem 4

The MOST essential inorganic molecule
for all living things is _______________.
◦
◦
◦
◦
CO2
Sugars
Water
Oxygen
Problem 5

The human body can make certain amino
acids, but has to get others from their
diet. Lacking certain amino acids will
interfere with your body’s ability to make
which of the following?
◦
◦
◦
◦
Lipid
Carbohydrates
Nucleic Acids
Proteins
Problem 6

The body can extract energy from several
different types of molecules. Which one
of the following provides SIMPLE FAST
energy?
◦
◦
◦
◦
a. Monosaccharides
b. Lipids
c. Polysaccharides
d. Proteins
Problem 7

Which of the following best explains why
enzymes are necessary for many cellular
reactions?
◦ A. Enzymes supply the oxygen necessary for the
reactions.
◦ B. Enzymes change reactants from solid to liquid
during the reactions.
◦ C. The reactions take up too much space in the
cell if enzymes are missing.
◦ D. The reactions are too slow to meet the needs
of the cell if enzymes are missing
Problem 8.

Michelle is working in a lab. She is trying to use
an enzyme to digest starch into single
monosaccharides. She adds starch to a tube and
then adds the enzyme. She knows that heat helps
chemical reactions so she places the tube on a
hot plate and waits for a reaction. After 10
minutes nothing has happened. What went
wrong?
◦
◦
◦
◦
Michelle added the wrong enzyme
Starch cannot be broken down into monosaccharides
The heat probably denatured the enzyme
10 minutes is too short, you need to wait for hours
for enzymes to work
Problem 9.

If an animal cell is placed in distilled water
it may swell and burst. The bursting of
the cell is a result of which process?
◦
◦
◦
◦
Enzyme activity
Active transport
Osmosis
Respiration
Problem 10.

Joe is studying different types of cells. He
notices cells all have a unique shape and
sometimes even have special structures that
aren’t found in other cells. Which of the
following would be the best conclusion for
Joe to make about his observations?
a. Some of the cells he is examining are mutated
b. Different cell types are specially adapted to work
for specific organisms
c. Every different species has a different type of cell.
d. He must be looking at prokaryotic and
eukaryotic cells.
Problem 11.

The body as well as individual cells, is in
charge of keeping homeostasis. Which of
the following could be the result of the
body failing to regulate a stable internal
environment?
◦
◦
◦
◦
Diabetes
Dehydration
Fever
All of the above
Problem 12.

Which two processes must happen
before a cell goes through mitosis?
◦ The DNA must replicate and the
chromosomes must separate
◦ Two cells must form and the cells must grow
◦ Cells must grow and DNA must replicate
◦ Cells must divide and the DNA must replicate
Problem 13.

DNA is folded into ___________ during
mitosis and then unraveled again at the
end.
◦
◦
◦
◦
Proteins
Chromosomes
The nucleus
RNA
Problem 14.

Which of the following can happen if cell
division is not regulated properly?
◦
◦
◦
◦
Diabetes
Cystic fibrosis
Cancer
Influenza
Problem 15.

Normal cell division is involved in all of
the following EXCEPT:
◦
◦
◦
◦
Repair of an injury
Growing
Making reproductive cells
Protein synthesis
Problem 16.

Neurons, cells in the nervous system, and skin
cells are very different. They have a different
shape, different function and are even found in
different places in the body. BUT upon close
inspection, neurons and skin cells have the exact
same set of DNA. What causes all the
differences?
◦ In reality their DNA is different it only looks the
same.
◦ They have the same DNA but access different genes
to make different proteins.
◦ Neurons don’t use their DNA
◦ Skin cells are actually dead cells.
Problem 17.

Place the following stages in the order
that they happen:
a. Fertilization  mitosis  differentiation 
organ formation
b. Fertilization  differentiation  mitosis 
organ formation
c. Mitosis  organ formation  differentiation
 fertilization
d. Fertilization  differentiation  organ
formation  mitosis.
Problem 18.

The body cell of a carrot has 18
chromosomes. That means that the carrot’s
reproductive cells will each have
_________ chromosomes and a carrot
zygote will have _________________
chromosomes.
a. 18; 18
b. 18; 36
c. 9; 9
d. 9; 18
Problem 19.

A doctor performs amniocentesis on an
embryo to find that it contains an extra
chromosome. Which is a possible
diagnosis for the baby?
◦
◦
◦
◦
Cancer
Down Syndrome
Influenza
Color blindness
Problem 20

A young patient is diagnosed with the
genetic disorder, Lactose Intolerance, which
results in the inability to digests milk
products due to a missing enzyme called
lactase. What is most likely the cause of
lactose intolerance in this patient?
a. The patient is allergic to milk.
b. The patient stopped consuming milk products.
c. A disease destroyed the lining of the digestive
tract.
d. A mutation occurred in the gene that is
responsible for producing lactase.
Problem 21.

Which of the following diseases/disorders
is contagious?
a. Cancer
b. Strep throat
c. Color blindness
d. Down syndrome
Problem 22.

Which of the following diseases/disorders
is heritable (inherited)?
◦
◦
◦
◦
Cancer
Strep throat
Color blindness
AIDS
Problem 23.

Disease, in general, can basically be
defined as:
a. When our bodies are infected with foreign
pathogens.
b. When mutations disrupt our ability to make
proteins.
c. When organs are not formed properly
d. When an imbalance is created that
prevents our body from functioning
normally.
MATTER AND ENERGY
TRANSFER
The atoms we are built out of cycle
through the ecosystem constantly.
Describe in words or labeled drawings
how each of the following
atoms/molecules cycles through our
ecosystems:
 Pictures of each of these can be found in the
book. Understand CONCEPTS don’t worry
about specific chemical changes

Cycles of matter (C, N, H, O)
Carbon
 Nitrogen
 Water
 Once in an organism, what are these
atoms used for?

◦ To build new cells
Moving matter and energy

How are these atoms passed from one
organism to the next?
◦ When we eat a plant the atoms that make up
the plant get digested and then our body uses
them to build new cells for us.

How can these atoms be returned to the
non-living parts of our ecosystem?
◦ When we die all our atoms are returned to
the soil through decomposition or released
into the atmosphere (CO2)
Can we make new matter
NO….NO…..NO
 We just recycle the matter that is here.
Living things today are made of the exact
same atoms that living things were made
of back in dinosaur times

What about energy?

The initial source of all energy is the SUN

How is this true even for strict
carnivores?
◦ The sun provides energy for the plants to
photosynthesize. Herbivores eat the plant
and energy gets transferred to them. Then
the carnivores eat the other animals and
the energy is transferred to them.
The energy pyramid
The shape of the pyramid implies there is
“less” at the top. “Less” what and why is
this necessary for success of the
ecosystem?
 Less energy and less biomass (atoms!)
 WHY?: because it is the lower levels
that feed and support the upper levels.
Need to have more food than eaters
or else you run out.

What does a food web demonstrate?

Flow of energy and matter from the
producers through the apex consumers
Impact of removal of a single species:
 Species that depend on the removed
species (predator) for food will decline in
population
 Species that the removed species
consumes (prey) will become over
populated causing a shortage of their
(the prey’s) food source.
Amt of energy passed from one
trophic level to the next

10% is passed from one level to the next

What happens to the rest?
◦ Ultimately becomes thermal energy (heat)
Biologically, how do we extract
energy from food?

Cellular respiration:
◦ Key enzymes in the cell along with the
mitochondria break the glucose down into
CO2 and Water and transfer the energy to
ATP molecules.
◦ Other foods, like protein and fats are first
converted into types of sugars that can go
through the same cellular respiration process.
Diagram of PS and Respiration
Three forms of energy in an
ecosystem
Light – sun
 Chemical – glucose
 Thermal – body heat released after using
energy

Two purposes of food:
Energy (we make ATP)
 Building materials

◦ We use atoms and rearrange them to make
cells for “us”.
◦ (also specific nutrients that are used directly
like vitamins, amino acids, minerals)
Why does an organism NOT
disintegrate when it is alive?
A constant supply of energy keeps our
body maintained
 When we die the energy supply ceases
and body processes no longer are
maintained.

Interdependence of 2 or more
Organisms

Symbiosis
◦ Three forms
 Mutualism
 Commensalism
 Parasitism
Problem 1.

In an experiment, chickens were fed grain that
contained a chemical marker in its proteins. The
presence of the marker can be detected in organisms.
Which of the following is the most reasonable
prediction from this experiment?
a. The marker will only be found in the grain.
b. Both chickens and wolves will have the marker
c. Wolves will have
the marker, but
chickens will not.
d. The marker will
only be found in
the animals’ wastes.
Problem 2

What two things are passed from one
organism to another in the food chain?
◦
◦
◦
◦
Energy and Heat
Matter and Atoms
Energy and Matter
Water and food
Problem 3

Which types of organisms assist in cycling
atoms back into the soil?
◦
◦
◦
◦
Producers
Primary consumers
Apex consumers
Decomposers
Problem 4





. Which hypothesis would most likely be
tested using this setup?
A. Green water plants release a gas in the
presence of light.
B. Roots of water plants absorb minerals in
the absence of light
C. Green plants need light for cell division.
D. Plants grow best in the absence of light.
Problem 5
At position Y, carbon is most likely to be
in which of the following forms?
 A. protein
 B. carbon solid
 C. carbohydrate
 D. carbon dioxide

Problem 6

Which of the
following
diagrams
correctly
represents an
energy pyramid
from this web?
B
Part C Interdependence
Define the following terms in relationship to their
position in the hierarchy of ecosystems
 Populations: all of one single species that lives in a
region


Communities: all of the living things in a region
(multiple species combined)

Ecosystems: All of the living things AND the non-living
things they depend on

Biomes: All the ecosystems at a particular climate

Biospheres: The entire region of the planet in/on
which life can exist
Food Webs

Explain how each organism in a food web
can be dependent on eachother.

They can depend on each other for
food, reproduction, habitat selection;
no organism can survive entirely on its
own.
What does the term
symbiosis mean?
Relationship between two organisms that
is necessary for the survival of one or
both the species.
 THREE TYPES
 Mutualism – win/win
 Commensalism – win/no effect
 Parasitism – win/lose

Human Impact on Environment

List five activities and explain HOW
◦ Excessive use of fossil fuels – build up of CO2;
traps extra heat; global warming
◦ Over developing wooded areas – destroys
habitats of organisms; impacts the food chain
◦ Deforestation – removes trees which reducing
oxygen production and CO2 removal
◦ Excessive use of chemicals like CFC’s –
depletion of the ozone layer; more harmful UV
rays hitting earth
◦ Pollution of lakes and rivers – damages water
life; contaminates water supply
When left alone (naturally)

How does an ecosystem balance itself to
keep all the organisms at the top of the
food chain from wiping out all the
organisms below?
◦ As a consumer increases the food supply
of that consumer decreases; eventually
there will not be enough food and the
consumers will die off; As the consumers
die, the food supply is rebuilt and so on
Problem 1
1. Which of the following is
most likely to lead to an
increase in the number of
foxes over time?
A. a decrease in owls
B. an increase in hawks
C. an increase in mountain
lions
D. a decrease in raspberry
bushes
Problem 2
If many trees are removed from a forest,
what is the most immediate effect on the
carbon cycle in that forest?
 A. increased rates of decomposition
B. decreased use of atmospheric CO2
 C. decreased combustion of fossil fuels
D. increased production of organic
compounds

Heredity and Reproduction
Organisms reproduce, develop, and have
predictable life cycles.
 Organisms contain genetic information
that influences their traits, and they pass
this on to their offspring during
reproduction.

Heredity and Reproduction
1. Genes are segments of DNA molecules located in
the chromosome of each cell. DNA molecules contain
information that determines a sequence of amino
acids, which result in specific proteins.
 2. Inserting, deleting, or substituting DNA segments
can alter the genetic code
 3. An altered gene may be passed on to every cell
that develops from it. The resulting features may help,
harm, or have little or no effect on the offspring’s
success in its environment.
 4. Sorting and recombination of genes in sexual
reproduction result in a great variety of possible gene
combinations in the offspring of any two parents

Basic Information
According to the central dogma of all living things:
_DNA__contains the master copy of all our information.


This information is broken up into sections, or recipes,
called ___genes__.

Each gene contains the directions to make a single
__protein_____ by linking together the proper
sequence of _amino acids__.

Before building a protein, a temporary copy of the single
recipe must be made. This copy is called __RNA_.

Ultimately it is the __protein_ that gives you the traits
that we have and the __genes/DNA_ that teaches us
how to make them.
DNA

Kept in the NUCLEUS

Wound up DNA:
◦ Chromosomes
Mutation

Change in the DNA

What problems does it cause?
◦ Since the DNA contains the directions
to make proteins, changing the DNA
could change the protein; Can cause
diseases, can have no effect or can
improve the function of a protein;
What types of changes are
considered mutations?
Insertions – add a nucleotide;
 Deletions – remove a nucleotide;
 Substitution – swap one nucleotide
for another


ANY CHANGE IN DNA IS A
MUTATION!
Effect of a mutation on future cells
Since all the DNA is copied before
cell division, a mutation in the
parent cell will be copied and passed
to the new cells.
 Mutations do not have to be
negative. They can be helpful or
have no effect.

What is genetic variation and why is
it important?
Genetic variation is diversity within or
between species because of their DNA
differences.
 IMPORTANCE: It is necessary to have
variation so that natural selection can
occur.
 Differences give individuals different
ability to survive and reproduce. This
allows for evolution

Three things that increase genetic
variation in a population

Mutation

Sexual reproduction – mixing the DNA
of two individuals
Recombination/crossing over – mixing
up your own DNA to make various different
reproductive cell
 Migration – introduction of new alleles
into a population from a different population

Genetic Variation
Which process listed above also explains
how one set of parents can seemingly
have an infinite number of different
children?
 Recombination

Problem 1






Fireflies produce light inside their bodies. The enzyme
luciferase is involved in the reaction that produces
the light. Scientists have isolated the luciferase gene.
A scientist inserts the luciferase gene into the DNA
of cells from another organism. If these cells
produce light, the scientist knows that which of
the following occurred?
A. The luciferase gene mutated inside the cells.
B. The luciferase gene was transcribed and translated.
C. The luciferase gene destroyed the original genes of
the cells.
D. The luciferase gene moved from the nucleus to the
endoplasmic reticulum
Problem 2

Which of the following best describes the
result of a mutation in an organism's DNA?
◦
◦
◦
◦
A. The mutation may produce a zygote.
B. The mutation may cause phenotypic change.
C. The mutation causes damage when it occurs.
D. The mutation creates entirely new organisms.
Problem 3
The diagram shows
the positions of the
genes for flower color
and stem length in a
pea plant.
 For these two genes,
what is the maximum
number of different
allele combinations
that can be formed
normally in gametes
produced from this
cell?

A. 2
B. 4
C. 6
D. 8
PT
Pt
pT
pt
Problem 4

If the DNA is mutated which of the following
statements is true?
◦ ALL other cells in the body will have the same
mutation.
◦ All proteins in the cell will be mutated
◦ Any proteins, RNA or cells that come from the
mutated DNA will have the mutation
◦ The cell will fix the mutation and nothing will happen.
Problem 5

Which of the following populations is likely to
have a high degree of genetic diversity?
◦ An asexual population of bacteria with a very low
mutation rate (asexual = NO VARIATION)
◦ Sexually reproducing species where crossing
over is frequent
◦ A population of sheep created by cloning (NO
VARIATION)
◦ A very small population of sexually reproducing
species. (SMALL POPULATIONS HAVE LOW
NUMBER OF VARIATIONS)
EVOLUTION AND DIVERSITY
Sometimes, differences between
organisms of the same kind provide
advantages for surviving and reproducing
in different environments.
 These selective differences may lead to
dramatic changes in characteristics of
organisms in a population over extremely
long periods of time.

KEY LEARNINGS
1 New traits may result from new combinations of
existing genes or from mutations of genes in
reproductive cells within a population
 2. Molecular evidence (e.g., DNA, protein structures,
etc.) substantiates the anatomical evidence for
evolution and provides additional detail about the
sequence in which various lines of descent branched
 3. The principles of evolution (including natural
selection and common descent) provide a scientific
explanation for the history of life on Earth as
evidenced in the fossil record and in the similarities
that exist within the diversity of existing organisms

Key Learnings
4. Evolution occurs as a result of a combination of
the following factors:
A. Ability of a species to reproduce
B. Genetic variability of offspring due to mutation and
recombination of genes
C. Finite supply of the resources required for life
D. Natural selection, due to environmental pressure, of
those organisms better able to survive and leave
offspring
Evolution is defined as:

How a population changes over long
periods of time

What key scientist is credited with the
bulk of our understanding about
evolution?
◦ DARWIN
Physical or molecular features used
to support evolution and shared
common ancestors:
DNA/Protein structures (molecular) – more
similar the sequences or structure the more
closely related two organisms are
 Anatomy – similar body structures can provide
information about relationships and ancestry
 Embryonic development – the stages we go
through during development can be informative
 Fossils – can tell us approximately how long ago
an organism lived

How does natural selection work?
Requires presence of variation!
Environmental stress (limited food and/or
other resources) must be present
 Competition for resources occurs - and
because they are different some are better at
competing that others
 Survival of the fittest – the organisms best
adapted win the competition and increase their
chances of surviving and reproducing
 Descent with modification – winners
reproduce more and the next generation consists
of more individual’s with the “winner’s” traits that
the “loser’s” traits.


How does genetic variation
promote evolution?
Allows organisms to be on different
playing fields as far as competition goes.
 Increases the chances that there is a
“super” trait out there than will give the
organism a survival advantage

Does evolution = new species?

No. EVOLUTION = a shift in the
frequency of certain alleles (variations
of genes) or traits

A population does NOT have to become
a separate new species (or split and
become two species) in order for it to be
“evolving”.
Problem 1



Thousands of years ago, giraffes with short necks
were common within giraffe populations. Nearly
all giraffe populations today have long necks. This
difference could be due to:
A. giraffes stretching their necks to keep their heads
out of reach of predators
 B. giraffes stretching their necks so they could reach
food higher in the trees
 C. a mutation in genetic material controlling neck size
occurring in some skin cells of a giraffe
 D. a mutation in genetic material controlling neck size
occurring in the reproductive cells of a giraffe.
Problem 2

Scientists have concluded that snakes evolved
from an ancestor with legs. Which of the
following statements provides the best evidence
for this conclusion?




A. Most species of snakes live on land.
B. Snakes move extremely fast to catch their prey.
C. Snakes have a well-developed backbone and
muscular system.
 D. Some species of snakes have limb buds during
their embryonic development
◦ The limb buds indicate that ancestors may have had
limbs
Problem 3

Which of the following best explains how the
fossil record provides evidence that evolution
has occurred? (need to look for an answer that
talks about change over time = def of evolution)
◦ A. It indicates that forms of life existed on Earth at
least 3.5 billion years ago.
◦
B. It indicates the exact cause of structural and
behavioral adaptations of organisms.
◦
C. It shows how the embryos of many different
vertebrate species are very similar.
◦
D. It shows that the form and structure of groups of
organisms have changed over time
Problem 4

On island chains like the one shown above, animal
populations that spread from the main island to
the other islands can evolve into separate
species.

CHOOSE THE STATEMENT ON THE NEXT
PAGE THAT best explains what favors speciation
in these situations?
Problem 4 (cont)
◦ A. Predators on the main island can easily migrate
to follow the populations to the other islands.
◦ B. Lack of disease on the other islands enables
the populations to grow and change without limit
◦ C. The physical separation of the islands limits
gene flow and interbreeding between the
populations.
◦ D. The climatic conditions of the islands allow the
populations to breed all year and produce several
generations
WE ARE FINISHED!
Problem 1 answers:
Problem 6