Download Biology EOC Class 4

Biology EOC
Class #4
Room 223
Mrs. Gleb
Class Four Plan!
 Writing:
Field Study Procedures
 DNA
 Evolution
 Genetics
 Practice
Test Questions (if there is time!)
Writing on the EOC
 You
MUST write something on these
sections!
 These questions are where the most
students lose points – do not skip
them
 Carefully review each writing
question and underline the
components that your answer
should have
Types of Short Answer / Writing
Questions
 Field
Study Procedure
 Record
environmental conditions
 Identify 2 controlled variables
 Identify manipulated variable
(3 conditions)
 Identify responding variable
 Say RECORD data (not “measure”
data)
 Make your final step “repeat steps
(list steps) two more times and
average the data”
Procedures
Students sometimes write conclusions or predictions instead of
the steps for a procedure.
Students sometimes miss the differences between controlled
experiments and field studies when writing procedures. Many of
those differences are defined by the bullets included with the
item. For example, field studies include recording environmental
conditions and describing the method for collecting data (e.g., a
consistent sampling strategy).
Students need to write procedures that use the manipulated
(independent) and responding (dependent) variables given in
the new experimental or field study question.
Many students use the same responding variable as was used in
the original scenario.
A procedure that does not use the correct manipulated
(independent) variable cannot answer the given investigative
question and no points can be earned on the item.
Procedures Continued
The manipulated (independent) and responding (dependent)
variables do not need to be specifically named or listed (e.g.,
Manipulated variable is water temperature) in order to receive
credit for them; the variables just need to be used correctly in the
procedure to be credited.
Sometimes students switch the identities of the manipulated and
responding variables and contradict their procedure.
Students need to be very clear about what they are measuring.
Many students write “record the data,” “measure the data,” or
“watch what happens and record the measurements” without
actually stating the responding variable. They should write things like
“record the number of organisms in the sample area,” “measure the
height of the plant,” or “measure the time for seeds to germinate” to
earn credit for the responding variable.
Students are expected to include at least three conditions of the
manipulated/independent variable for both controlled experiments
and field studies.
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8
DNA
 DNA
is often called the
blueprint of life.
 In simple terms, DNA
contains the instructions
for making proteins within
the cell.
9
Watson & Crick’s Model
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Why do we study DNA?
We study DNA for
many reasons,
e.g.,
 its central
importance to all
life on Earth,
 medical benefits
such as cures for
diseases,
 better food crops.
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Chromosomes and DNA
Our
genes are on
our chromosomes.
Chromosomes are
made up of a
chemical called
DNA.
12
The Shape of the Molecule
DNA
is a very long
polymer.
The basic shape is
like a twisted ladder
or zipper.
This is called a
double helix.
13
The Double Helix Molecule
The
DNA
double helix
has two
strands twisted
together.
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One Strand of DNA
backbone of the
molecule is alternating
phosphates and
deoxyribose sugar
 The teeth are
nitrogenous bases.
phosphate
 The
deoxyribose
bases
Nucleotides
One
deoxyribose
together with
its phosphate
and base
make a
nucleotide.
O
O -P O
O
O
O -P O
O
O
O -P O
O
Phosphate
Nitrogenous
base
O
C
C
C
O Deoxyribose
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One Strand of DNA
nucleotide
 One
strand of DNA is
a polymer of
nucleotides.
 One strand of DNA
has many millions of
nucleotides.
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Four nitrogenous bases
DNA has four different bases:

Cytosine C

Thymine T

Adenine A

Guanine G
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Two Kinds of Bases in DNA
Pyrimidines
are
single ring bases.
Purines
are
double ring
bases.
N
N C
O
C
C
N C
N
N C
C
C
N C
N
N
C
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Thymine and Cytosine are
pyrimidines
 Thymine
and cytosine each have one ring of
carbon and nitrogen atoms.
N
O
O
C
C C
N
N
C
C
thymine
O
C
C
N
C
N
C
cytosine
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Adenine and Guanine are purines
Adenine and
guanine each have two
rings of carbon and nitrogen atoms.
N
N
C
Adenine
N
C
C
N
O
N
N
C
N
C
C
C
C
N
Guanine
C
N
N
C
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Two Stranded DNA
Remember,
DNA
has two strands
that fit together
something like a
zipper.
The teeth are
the nitrogenous
bases but why
do they stick
together?
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Hydrogen Bonds
C
N
N
N
C
N
C
C
C
C
N
N
C
C
C
O
bases attract each
other because of
hydrogen bonds.
 Hydrogen bonds are
weak but there are
millions and millions of
them in a single
molecule of DNA.
 The bonds between
cytosine and guanine
are shown here with
dotted lines
N
 The
N
O
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Hydrogen Bonds, cont.
 When
making hydrogen
bonds, cytosine always
pairs up with guanine
 Adenine always pairs up
with thymine
 Adenine is bonded to
thymine here
N
O
O
C
C
C C
N
C
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Chargraff’s Rule:
Adenine and Thymine always
join together
A
T
Cytosine and Guanine
always join together
C
G
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DNA by the Numbers
 Each
cell has about 2
m of DNA.
 The average human
has 75 trillion cells.
 The average human
has enough DNA to go
from the earth to the
sun more than 400
times.
 DNA has a diameter of
only 0.000000002 m.
The earth is 150 billion
m
or 93 million miles from
the sun.
Evolution
Voyage of the Beagle
 During
his travels, Darwin made numerous
observations and collected evidence that led
him to propose a hypothesis about the way life
changes over time.
Darwin’s Observations
 Giant
Tortoises of the Galápagos
Islands
Darwin’s Observations
 Variety
of finches
• Jean-Baptiste Lamarck proposed that by selective use or disuse of
organs, organisms acquired or lost certain traits during their
lifetime. These traits could then be passed on to their offspring.
Over time, this process led to changes in a species.
Lamarck’s
explanation of
how evolution
works was
wrong, but it
helped set the
stage for
Darwin’s ideas
Others that influenced Darwin’s ideas
 Charles Lyell: explained that slow and gradual
processes have shaped Earth’s geological
features over long periods of time.
 Thomas Malthus: Populations can grow much
faster than the rate at which supplies of food or
other resources can be produced.
 Alfred Wallace: Described same basic
mechanisms for evolutionary change that
Darwin had proposed.
Darwin’s Two Main Points
Descent
with modification:
Descendants of earliest organisms
accumulated adaptations to
different ways of life.
Natural
selection: The process by
which individuals with inherited
characteristics well-suited to the
environment leave more offspring
on average than other individuals
Darwin’s Book
The
Origin of Species (1859)
 Natural
selection: The process by which
individuals with inherited characteristics wellsuited to the environment leave more
offspring on average than other individuals
Evidence of evolution
Darwin argued that living things have been
evolving on Earth for millions of years.
Evidence for this process could be found
in:
 the fossil record,
 the geographical distribution of living
species
 homologous structures of living organisms,
 Vestigial structures,
 Similarities in early development,
 Molecular biology.
Fossil Record
 Each
layer of sedimentary rock represents a
time period. Fossil in each layer represent
organisms that lived when the layer was
formed
Geographic Distribution of Living
Species
 Darwin
decided that all Galápagos
finches could have descended with
modification from a common mainland
ancestor.
EXAMPLE OF GEOGRAPHICAL DISTRIBUTION
When pre-New Zealand split of from Australia, a
new specie of birds called the "Kaka" evolved
from its parrot-like ancestor. Then as new
mountain ranges are formed in pre-New
Zealand, these birds further evolve into two
distinct specie: Lowland Kaka and Alpine Kea.
Later, when pre-New Zealand split into two
islands (which is now modern day New
Zealand), the Lowland Kaka evolved into the
North Island Kaka and the South Island Kaka.
Homologous Body Structures
 Structures
that have different mature
forms but develop from the same
embryonic tissues are called
homologous structures.
 Similarities and differences in
homologous structures help biologists
group animals according to how
recently they last shared a common
ancestor.
• Not all homologous structures serve
important functions.
• The organs of many animals are so reduced
in size that they are just vestiges, or traces,
of homologous organs in other species.
• These organs are called vestigial organs.
Similarities in Embryology
The
early stages, or embryos, of many
animals with backbones are very
similar.
The same groups of embryonic cells
develop in the same order and in
similar patterns to produce the tissues
and organs of all vertebrates.
What about DNA
The
use of Genetics and the
knowledge of DNA has allowed for
analysis of the similarities and
differences between organisms.
Common DNA sequences may
support the theory that they share a
common ancestor.
Mendel + Darwin
Genetics
Evolutionary biology
Change within
populations
What is the gene pool of a
population?
 The
sum total of all the
alleles (alternative
forms of genes) in all
individuals that make
up a population.
Microevolution
 Evolution
based on genetic changes
 A generation-to-generation change in
the frequencies of alleles within a
population
Hardy-Weiberg equilibrium
 The
frequency of alleles in the gene pool of
a population remain constant over time (in
contrast to microevolution).
 This equilibrium is not maintained in nature.
What mechanisms can
change a gene pool?
Genetic


Drift (Chance)
Bottleneck effect
Founders effect
Natural
sorting)
 Gene
flow
 Mutation
selection (Chance &
Genetic Drift
Change in a gene pool of a population
due to chance
Effects of genetic drift in small
populations: The bottleneck Effect
Natural
disasters
And The Founders Effect
A
few individuals colonize an isolated island,
lake, or some other new habitat.
Gene Flow
 Exchange
of genes with other populations
 Interbreeding increases variation in the
population’s gene pool
Mutations
 Mutations
carried by gametes enter the
gene pool
What leads to adaptation?
 Natural
selection – a blend of chance and
sorting
 Chance - mutation & sexual recombination
of alleles lead to genetic variation in a
population
 Sorting – differences in reproductive
success among members of the varying
population
 Genetic drift, gene flow, and mutation
cause microevolution or changes in allele
frequencies, but not adaptation
Genetics
Genetics
 Scientific
Study of heredity (how traits are
passed on to future generations)
 Trait: specific characteristics of an
individual
 Hybrid: The offspring of crosses between
parents of different traits
 P1 + P1 = F1 / F1 + F1 = F2
P
is parent generation, F1 is first generation, F2 is
second generation
Genes & Alleles
 Genes
determine traits
 Different forms of a gene are called
alleles
 Principle of dominance
 Some
alleles are dominant, others are
recessive
Principle of Segregation
 Gametes


(sex cells)
During gamete formation, the alleles for
each gene segregate from each other
Each gamete carries only one allele for
each gene
Punnet Squares
Punnet Squares
 Two
identical alleles are called
homozygous

Example: tt or TT
 Two
different alleles are called
heterozygous

Example: tT
Phenotype vs Genotype
 Two
hybrids can have the same
phenotype (physical characteristics), but
different genotypes (genetic make up)
because of dominate and recessive
genes
Incomplete Dominance
 Sometimes
one allele is not completely
dominate over another
Codominance
 In
codominance, both alleles are
expressed