Download 7) NATURAL SELECTION: the process by which forms of life having

7) NATURAL SELECTION: the process by which forms of life having
traits that better fit a specific environmental pressure, such as predators,
changes in climate, or competition for food or mates, will tend to survive
and reproduce in greater numbers than others of their kind, thus
ensuring the continuance of those favorable traits in succeeding
generations.
8) CHROMOSOME: Threadlike strands of DNA and protein
located in the cell’s nucleus; they carry the gene codes
9) GENE: The basic unit of heredity carried by the
chromosomes; composed of two paired alleles; it codes
for features or traits of organism.
FEATURE:
structure,
characteristic,
or behaviorinofanan
TRAIT: AAspecific
way
a feature is expressed
organism, such as eye color, fur pattern, or timing of
individual organism.
migration.
TRAIT: A specific way a feature is expressed in an
individual organism.
Trait: some zebras know how to ride a motorcycle to escape
predators
Table of Contents (the TOC)
Unit 2, Population Diversity
Date
10/
10/27
Description
Pg #
Features and Traits
1
Genetics
2
Inside the nucleus is
the inheritance
messenger, DNA.
(Deoxyribonucleic
acid). DNA molecules
are “huge” containing
millions of atoms.
In order to fit inside the
nucleus, they are coiled
and coiled again into
structures called
CHROMOSOMES - the
______________
structures that carry the
message of inheritance.
This drawing shows the
nucleus of a cell from
our animal, the larkey.
Notice that there are
eight chromosomes,
looking a little bit like
bent hot dogs of
different lengths.
If you look closely, you
will see that these two
chromosomes are the
same, these two are
the same, and so on.
Chromosomes always
come in pairs. So our
larkey actually has four
pairs of chromosomes
rather than eight
different ones.
Now look at the dark
areas. Both
chromosomes in a pair
have dark areas exactly
the same location. The
dark areas are called
alleles.
Note: Alleles are not really dark. The dark color is used to represent
the location of the alleles on the chromosomes
The two alleles on the paired
chromosomes work together.
Together they constitute a gene.
Summary
•  Nuclei contain chromosomes.
•  Chromosomes come in
almost identical pairs.
•  Chromosomes have specific
active locations called alleles.
•  The two alleles in identical
locations on paired
chromosomes constitute a
gene
A gene (two alleles working
together) controls a trait.
This gene could be the one that
determines the larkey’s eye
color, or perhaps the pattern of
its fur. Let’s say it determines
eye color.
The larkey has four features of
interest to us. Each feature is
controlled by one gene. Each of
the four genes is on a different
chromosome (although they could have
all been on the same chromosome).
The gene location for
appendages (legs) is these
two alleles on this pair of
chromosomes. The alleles
are labeled with the letter A
for appendages.
Find the gene locations
for eye color (letter E),
fur pattern (letter F), and
tail shape (T).
Notice that some of the
alleles are labeled with
uppercase letter and
some are lowercase
letters. Both upper and
lowercase letter Es are
alleles for eye color.
Alleles don’t all have
equal influence in
determining traits. Moreinfluential alleles are
dominant alleles, and
they are represented by
an uppercase letter.
Less-influential alleles
are called recessive
alleles, and they are
represented by a
lowercase letter.
The alleles are the code
that determines the traits
of the larkeys. The chart
at the bottom is the
genetic code for one of
the 32 larkeys we
viewed previously.
The alleles for legs is aa,
eye color = Ee, fur
pattern = FF, and tail
shape = tt;
The alleles for legs is aa,
eye color = Ee, fur
pattern = FF, and tail
shape = tt;
The combination of
alleles in an organism's
chromosomes is the
organism’s genotype.
The genotype lists the
paired alleles that are
particular to that
organism.
Let’s look at the
genotype of our larkey to
see what is dominant
and what is recessive.
•  Two recessive alleles
for leg length (aa)
•  One dominant and one
recessive allele for eye
color (Ee)
•  Two dominant alleles
for fur pattern (FF)
•  Two recessive alleles
for tail shape (tt).
Let’s look at the
genotype of our larkey to
see what is dominant
and what is recessive.
•  Two recessive alleles
for leg length (aa)
•  One dominant and one
recessive allele for eye
color (Ee)
•  Two dominant alleles
for fur pattern (FF)
•  Two recessive alleles
for tail shape (tt).
The parents of a Larkey both have red eyes. Is it possible for
them to produce an offspring with grey eyes? In your
notebook use a Punnet Square to prove or disprove this grey
eye question. (The alleles for eyes are E or e.)
The parents of a Larkey both have red eyes. Is it possible for
them to produce an offspring with grey eyes? In your
notebook use a Punnet Square to prove or disprove this grey
eye question. (The alleles for eyes are E or e.)
Female Ee
E
Male Ee
e
E
E E
E
e
E e
e e
e
WORD BANK (top)
chromosomes (2x)
dominant, DNA, genes,
genotype, nucleus, paired
alleles, phenotype,
recessive;
WORD BANK (bottom)
allele, chromosome,
gene, nucleus.
Top (in order)
nucleus, DNA,
chromosomes,
Chromosomes, genes,
paired alleles, genotype,
phenotype, dominant,
recessive.
Bottom (in order)
chromosome, gene,
nucleus, allele
Survival of the fittest
Peppered Moth
example, an adult giraffe grows a longer neck because it has difficulty
reaching the leaves in its ecosystem