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Wednesday, January 7, 2015

BIO 201
Lecture 1 - Chemistry

- Definitions
- Element - a substance that cannot be broken down into other kinds of substances by
ordinary chemical means
...
0073 units

Charge = +1

• Neutron

Mass = 1
...
0005 units

Charge = -1

• The number of protons in an atom determines the element
- Isotopes - Atoms with the same number of protons (i
...
the same element), but
different number of neutrons

-

- Chemically identical, but have different properties
...
e
...

• Osmosis: the diffusion of water across a semi-permeable membrane

- Mean Speed of oxygen molecules: 460 m/s ~ faster than the speed of sound
- Mean free path: distance a molecule can travel before it hits another molecule - 60
nm

- Collision Frequency: the frequency of collisions - 10 billion per second
- MACROMOLECULES
- Lipids: oil, fat, wax
• Made up of glycerol and fatty acids
• Non-polar molecules: hydrophobic - don’t mix with water
• Water molecules tend to stick together and ignore the lipid molecules
• Relatively high in chemical energy
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Wednesday, January 7, 2015

- Carbohydrates: sugar, starch, cellulose
• High in chemical energy
• Polar molecules: hydrophilic - dissolves in water
• Simple Carbohydrates - Monosaccharide
• Each molecule has a single sugar unit
• Monosaccharides can be bonded together to form a disaccharide - each molecule
has two sugar units
• Polysaccharide - long chain of saccharide units joined together
• Example of a polymer - made up of a simple repeating part i
...
repeating chains of
glucose

- Nucleic Acids: DNA, RNA
• Genes, expression of Genes
• Example of a polymer: nucleotides

- Proteins: enzymes, hormones, structure
• Polymer: made up of units called amino acids
• Some parts may be polar; other parts may be non-polar
• There are 20 different kinds of amino acids that are used to make proteins
• Characterize the protein by the specific chain of amino acids
• Primary Structure: sequence of amino acids
• Secondary structure: repeated coils/folds
• Tertiary Structure: irregular folding
• All proteins have primary, secondary, and tertiary structure
• Quaternary Structure: two or more chains aggregated to form a functional unit - only
few proteins have this type of structure
• All for levels exist simultaneously - they don’t replace each other

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Wednesday, January 7, 2015

- LIFE
• Response to the environment
• Exchange of material with the environment
• Metabolism
• Growth
• Reproduction
• Life is an emergent property of a particular arrangement of certain molecules
• Everything that is alive is made up of one or more cells

- Prokaryotic Cells: no true nucleus
• Bacteria

- Eukaryotic Cells: have a true nucleus
• Humans, animals, plants, etc…

- Unicellular: each cell carries out all life processes
• all prokaryotes are unicellular

- Multicellular: made up of many cells, with different cells specialized to perform
different functions

• Most eukaryotic cells are 10-100 um
• Typical prokaryotic cells are between 1-10 um
• The smaller an object gets the higher the surface area to volume ratio gets - allows for
faster exchange of material with the environment
• Cells are small because they require a high surface to volume ration to exchange
materials with their environment

- Cytosol: complex mixture of enzymes and many other molecules in water
• many of the chemical reactions take place here

- Plasma Membrane: Boundary between cell and environment
• controls exchange material with the environment
• Phospholipid: makes up most of the plasma membrane
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Wednesday, January 7, 2015
• Made up of a polar head and two non-polar tails
• Polar heads like to form hydrogen bonds with water molecules - non-polar tails tend
to get isolated away from the water
• Phospholipid Bilayer - structure of a plasma membrane
• The Non-Polar layer makes it relatively impermeable to polar molecules
• Non-polar molecules (Oxygen, CO2, Lipids) diffuse through freely
• Small polar molecules (H20, ethanol) diffuse through much more slowly
...
) Synthesis of Lipids
• 2
...
e
...
R
...
)
• Cytoplasm: refers to everything in the cell membrane - contains the organelles &
cytosol
• All through the cell there is a network of tubules called the cytoskeleton
• Give the cell shape, allow the cell to move and allow for intracellular transport
• Centrosome: with a pair of centrioles, organizes the cytoskeleton
• Particularly noticeable during cell division because it has to be reorganized
• “Microtubule organizing centre” - more broad term
• Allows to manipulate the cytosol
• Outside of the phospholipid bilayer - Extracellular Matrix
• Web that attaches to an animal cell
• Helps to strengthen tissues, helps cell to react to environment ( with glycoproteins,
e
...
collagen)
• Embedded in the phospholipid bilayer is cholesterol - non-polar molecule; helps
to maintain membrane fluidity

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Wednesday, January 7, 2015
• Receptor Proteins: respond to specific chemicals
• Does not transport material across the membrane - changes shape and can
perform different function
• Enzymes - embedded in the phospholipid bilayer
• Identification Markers - allows for other cells to be recognized by other cells
• Tight junction proteins: Hold cells together

CYTOSIS - transport via folding of a membrane
• PLasma membrane folds in around the bacterial cell
• Gets folded into a vacuole or a vesicle
• Endocytosis: enter the cell via cytosis
• Exocytosis: exiting the cell via cytosis

Lecture 4:
• Lysosome contains active hydrolytic enzymes
• Food vacuole
• Proteins that are built in the Rough E
...
- can be moved by cytosis forming vesicles to
the Golgi apparatus to be sorted, moved, exited the cell through endocytosis

Plant Cell
• Has membrane bound nucleus
• Do not have a centrosome with centrioles - it has a microtubule organizing center on
nuclear envelope
• Have a cell wall - rigid, gives cell shape and protects it from bursting cellulose)
• Have one large central Vacuole
• Fucntions: Storage & turgor (stiffness caused by water pressure)
• May also contain chloroplasts
• Site of photosynthesis in plant cells
• In the inner membrane fliud called stroma
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Wednesday, January 7, 2015
• In the storma there are sacs called thylakoids - provide a membrane for
photosynthesis
• There are ribosomes present
• Also contains a loop of DNA
• Plasmodesma
• Openings from one cell to the next
• Connect cells to their neighbours
• The phospholipid bilayer continues from one cell to the next
• Allows the passage of cytosol from cell to cell
• Allows for material to move easily from cell to cell in the tissue

BACTERIAL CELLS
• No true nucleus - no membrane bound nucleus
• No Endoplasmic reticulum
• No Golgi Apparatus
• No mitochondria
• No Chloroplasts
• No vesicles or vacuoles
• No centrosome

ANIMAL CELLS
• No Cell Wall
• No Plasmodesmata
• No Chloroplasts
• No Central Vacuole

PLANT CELLS
• No centrosome
• No Lysosomes

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• Cell wall composed of cellulose

FUNGAL CELLS
• Eukaryotic cells - true Nucleus
• Cell Wall - composed of chitin
• Pores between cells but no plasmodesmata
• Pores are big enough that organelles can pass easily from cell to cell
• Sometimes there are no division among cells - one big supercell
• No centrosome
• No Chloroplasts

Metabolism
• Refers to all chemical reactions taking place in an organism

Metabolic Pathway
• A particular sequence of connected reactions
• Largely controlled by enzymes - protein that facilitates a specific chemical reaction
• Doesn't exist in isolation - part of a wider web of interacted chemical reactions

ATP (Adenosine TriPhosphate)
• A high energy molecule to provide energy in cells
• Provides energy by being connected into ADP (Adenosine DiPhosphate)
• The lower energy form of ATP
• ATP loses a phosphate - turns into ADP = releases energy that can be used for active
transport
• To convert ADP into ATP - you need an extra phosphate molecule and energy to fuse
it on to the ADP Cell

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Wednesday, January 7, 2015
NADH, FADH2, NADPH
• High-energy molecules (carrying high-energy electrons)

NAD+, FAD+, NADP+
• Lower energy forms of the above molecules (without high energy electrons)

Cellular Respiration
• Taking sugar + Oxygen = Carbon Dioxide + Water + energy (in ATP and heat)
• Whole point of cellular reparations is to generate ATP
1
...
) Glucose undergoes glycolysis to become pyruvate - has less chemical energy than
glucose
3
...
) In the Citric Acid Cycle turns Pyruvate into Carbon Dioxide - less energy than
Pyruvate
• releases energy which is used to create NADH & FADH & ATP
5
...

• The H+ gradient is used to change ADP to ATP
• Involves 10 electron carriers
• 2 Parts of focus
• 1)Eletron Transport Chain - Focus is to pump Hyrogen ions out of the cell to create a
gradient
• FOund in the plasma membrane in the Prokaryotic cell
• Found in the inner mitochondrial membrane in a Eukaryotic cell
• NADH will drop its hydrogen electrons off = NAD+
•
• Energy used to fuel active transport of hydrogen ions across the membrane
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Wednesday, January 7, 2015
• Electrons transported used to fuel active transport along the membrane (Electron
Transport Chain)
• Used to pump Hydrogen ions out of the cell
• Water molecule is created from Oxygen and hydrogen ions created from the
Electron transport chain
• Oxygen’s job is to pick up loose hydrogen ions
2
...
) Calvin Cycle (dark/light-independent reactions)

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Wednesday, January 7, 2015

Lecture 7:

Eukaryote: Plant
• Cell wall do not get stretched out during the anaphase
• New nucleus form in each end of the cell
• Cytokinesis: Accumulation of vesicles in the middle of the cell instead of the
cleavage furrow - generated before mitotic phase began
• Contain the particular material for building a cell wall - adjacent vesicles begin to
fuse together; more start to accumulate = start to form a cell wall - cell plate
• Grows and grows until it forms two cells and cytogenesis is complete

MEOISIS AND SEXUAL LIFE CYCLES

Zygote: a single cell; fertilized egg - goes through the cell cycle - forms a multicellular
organism

Gametes: Sperm and egg cells involved in the process of fertilization which forms a
zygote
• Haploid

Haploid: One complete set of genes or one complete set of chromosomes
• Number of chromosomes = n
• do not have homologous pairs

Diploid: two complete set of genes or two complete sets of chromosomes
• Number of chromosomes = 2n
• Homologous pairs: one complete set of chromosomes

Fertilization: the zygote ends up being diploid
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Wednesday, January 7, 2015
• the 23 chromosomes from the egg & 23 chromosomes from the sperm fuse together
• Each homologous pair is made up of one chromosome from the sperm and one
chromosome from the egg

Meiosis: change the diploid cells into haploid cells - only in the production of gametes
1
...
) Prophase I: chromosomes condense & nucleolus disperses; nuclear envelope
breaks up; spindles being to from around the centrosomes
• Homologous pairs of chromosomes are found together - 2 chromosomes; 4
chromatids
• Crossing Over: the homologous pairs condense together and begin to cross
over each other - genetic material is exchanged between the pair - can be made
up of a mix of genetic material
• 2
...
) Anaphase I: homologous pairs are being split; chromosomes pulled to
opposite ends of the cell; the cell elongates
• 4
...
) Prophase II
• 2
...
) Anaphase II

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Wednesday, January 7, 2015
• 4
...
)Telophase II

Cytokinesis II
• each cell divide - end up with four cells with chromosomes and no pairs

Variations - Life Cycles

Fungi - some Algae
• Zygote does not go through the cell cycle - it undergoes meiosis
• Produces a bunch of haploid cells - not gametes - they are spores
• No Fertilization occurring
• Cell Cycle occurs where they settle and where there is food
• End up with a multicellular organism that is haploid
• Continues through the cell cycle to generate gametes
• Gametes fuse together through fertilization to produce another gamete

Plants - some algae
• Zygote: goes through the cell cycle to produce a diploid multicellular organism
• a few cells may go through meiosis - produces haploid spores and not gametes
• Spores if they find a place to live go through the cell cycle - the cells are haploid
• Multicellular organism being generated which is haploid
• Multicellular organism can continue through the cell cycle to produce gametes
• The gametes can be fertilized to produced a zygote

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GENETICS

Character or Trait: A potentially variable quality or quantity in an organism
• E
...
flower colour - purple, white

• When pea plants reproduce, if the new generation of pea plants always has the same
characters, it is a true breeding variety

Hybrid: the offspring of two different varieties
Monohybrid Cross: Studying the inheritance of single character in a hybridization
experiment

P Generation: parental generation - starting point for experiment
• F1: First filial generation - offspring of P generation
• F2: Second filial generation - offspring of F1 generation
• Gave Mendel insight into how inheritance occurred

Particles of Inheritance:
• There would be a P: purple particle of inheritance and a P: white particles of
inheritance
• Each pea plant inherits two such particles
• For some reason one particles id dominant: it determines the colour of the flower even
when the other type of particle is present

Lecture: Eight

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Wednesday, January 7, 2015
GENETICS CONT’D

Punnet Square: see diagrams
Definitions
Gene: a sequence of genetic material (DNA)
Locus: the place on a chromosome where a gene is located
Allele: one form of a gene found at a particular locus
Diploid: having two alleles at each locus
Haploid: having one allele at each locus
Homozygous: The two alleles at a particular locus are the same
• Only makes sense when taking about a diploid organisms
Heterozygous: the two alleles at a particular locus are different
Dominant: an allele that is fully expressed in a heterozygote
Recessive: an allele that is not expressed at all in a heterozygote
Genotype: the specific alleles that an organism has
Phenotype: the character that the organism has (due to the genotype and the
environment)

Pea Plant: are diploid (2 alleles at each locus)
• Flower color locus
• Purple allele (dominant) & White allele (recessive)

Examples
...
g
...
g
...
g
...

• On Average 50% will be boys; 50% will be girls

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• Meiosis is not perfect - it sometimes makes “mistakes”
• Sometimes when the chromosomes line up in Meiosis I - Anaphase I a chromosome
might be pulled the wrong way - NONDISJUNCTION - too many chromosomes being
pulled to one end of the cell; not enough being pulled to the other
• Neither of the cells is either Diploid or Haploid
• It is possible for Nondisjunction to occur in Meiosis II
• If it happens in Oogenesis - Can have an egg with two XX Chromosomes or no
chromosomes
• If it happens in Spermatogenesis - can prodcue XY, XX, YY or no chromosomes
• If the egg is fertilized:
• XO: No Second X chromosome - Turner Syndrome - 1 in 2,500 Girls
• XXY: Kleinfelter Syndrome - 1 in 500 boys
• XXX: Tiplo X Syndrome - 1 in 1,000 Girls
• YO: No X chromosome - Lethal
• XYY: Jacob Syndrome - 1 in 1,000 boys

• Humans have 23 homologous pairs of chromosomes • This include 22 pairs of autosomes and 1 pair of sex chromosomes - numbered from
largest to smallest 1-22
• Having three of chromosome 21 (trisomy 21) results in Down Syndrome
•
Heterozygote at two Loci
• 4 possible combinations from the gametes - Depends on how they line up - could be
pulled into different directions
• LInkage - can have independent assortment or linkage - indicated when the numbers
dont match dependent assortment or independent assortment
• Due to Crossing Over - genetic material to be exchanged - creates new
combinations
• Allows for the Combination of all 4 alleles

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Non-Mendelian Inheritance
• Prokaryote with asexual reproduction (Bacteria)- goes through binary fission produces Clones
• Plasmids - Conjugation: two cells connecting to each other through their plasma
membrane
• Bacterial Cell can pick up a plasmid - exchange of genetic information
• Eukaryotic with asexual production
• Euglena - goes through mitosis & cytokinesis - produces clones
• Haploid Eukaryote with sexual reproduction
• Chlamydomon - haploid cell can fuse together to produce a diploid zygote - goes
through meiosis and produces haploid cells
• Mitochondria • Sperm do not transfer mitochondria DNA from the males - only from Females

POPULATION GENETICS
• Regular genetics is not circled with how common any genotype is in a population
• Concerned with how common certain genotypes are in a population rather than the genotypes
of specific parents their offspring
• The probability that two particular things will happen at two particular times may be calculated
as the probability of the first multiplied by the probability of the second
Cystic Fibrosis:
• 1 in 25 Europeans are carriers of cystic fibrosis, they are heterozygous at this locus (Cc)
• 1 in 25 = 1/25 = 0
...
04 x 0
...
00016
A different Approach
• If 1 in 25 people are heterozygous at this locus, then 1 in 50 alleles are cystic fibrosis alleles
• What is the probability of getting 2 cystic fibrosis alleles = 1/50 x 1/50

DNA - Guest Lecturer

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Wednesday, January 7, 2015
DNA Structure
• Made up of subunits called nucleotides
• nucleotides made of
• 1
...
) 5-Carbon sugar
• 3
...
) break the hydrogen bonds apart
• 2
...
) Form complementary strand for each template strand - end up with 2 double
stranded DNA each with its new complimentary strand
• DNA Polymerase: main enzyme in DNA replication
• Works its way along the template strand and bring in complementary bases
• Adds to new complementary strand
• 5’ and 3’ prime end - opposite ends
• Called Antiparallel for complimentary strands
• Legging Strand & leading Strand
• Leading Strand: when DNA gets pulled apart DNA polymerase can work in one
direction when replicating
• Lagging Strang: because it can only go one way it has to copy in fragments and go
back to position

GENE EXPRESSION
• DNA —-> Protein —-> Trait (Central Dogma)
• Ex
...
—> Insulin
• Ex
...
) Messenger RNA (mRNA)
• Carries protein blueprint from DNA to ribosomes
2
...
) Ribosomal RNA (rRNA)
• With certain proteins, makes up ribosomes

Ribosomes
• Made up of Subunits - Small & Large Subunits
• Subunits get built in the nucleolus

In Prokaryotes
Transcription: the process of copying DNA to RNA
Translation: Use the sequence of mRNA to direct the production of a protein

In Eukaryotes
• Also has transciption
• RNA Processing: Pre-mRNA goes through

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Transcription
• Along DNA strand there is a region called the Promoter region
• Next to the Promoter is the Transcription Unit
• After the Transcription Unit is the Terminator
1
...
) Elongation
• RNA polymerase works its away long the template strand adding in complementary
bases
• Transcription Unit
3
...
) Initiation
• Small Subunit ribosome and mRNA
• There is a particular sequence called the Start Codon
• There is a tRNA with a complementary sequence to the Start Codon

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• Large subunit comes together and forms a whole
2
...
) Termination
• Gets to a stop codon - no tRNA has a complementary base to the mRNA
• Releases the free polypeptide of amino acids and ejects the ribosomes

Eukaryotic Cells
• The extra Step: RNA Processing
• A Cap and Tail are attached to the ends of the pre-mRNA
• Introns are removed from the pre-mRNA
• Cap and tail help to protect the mRNA from degradation
• In eukaryotes, some proteins will be translated into the rough endoplasmic reticulum
• Ribosome with mRNA in it that jams • Can’t get rid of the mRNA unless it goes to the Rough E
...

• Can only be translated if it gets to the Rough E
...
where they can release the amino
acid chain and the mRNA

Mutation
• Any change in DNA
• Once the mutation has occurred, the new (mutant) DNA is treated just like any other
DNA
• All current DNA was “mutant” DNA at some time in the past
Substitution
• One base is substituted for Another
• Can not have any effect in the organism - amino acid chain could be the same
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Wednesday, January 7, 2015
• Could result in a different amino acid in the chain
• If it creates a Stop Codon where there wasn’t one before could have drastic effects

Insertion
• One or more nucleotides are inserted into DNA
• Can create a Stop Codon

Deletion
• One or more nucleotides are deleted from DNA
• Frame Shift: Changes from of reference for all the rest of Codons from where the
base was removed

Mutagen
• Something that causes mutation
• i
...
High Energy Radiation, Certain Chemicals
DNA Replication
• About 1 error per 1-10 Billion bases

Mutation Rates Vary
• Environmental effects on DNA replication
• The average human has about 128 mutations

Lecture: February 13th
Gene Regulation:
• The expression of genes is regulated; some genes are expressed at certain times, in
certain cells, some more than others
• the control of transcription is the most important mechanism in the control of gene
expression
• Negative Control:
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Wednesday, January 7, 2015
• Something must be removed to allow transcription
• Positive Control:
• Something must be added to allow transcription

Population Genetics

• Example: Sickle-Cell Disease
• Differences in DNA leads to to transcription of RNA being different between
homologous pairs
• Leads to different chains of amino acids produced which fold differently - produce
different proteins
• Neurofibromatosis
• Gene involved in control of cell division
• Huntington Disease
• Gene function unknown
Pattern
• Inherited diseases that prevent reproduction are generally caused by dominant alleles
• Recessive alleles can hide amongst the population; Dominant alleles can’t be
inherited on before reproduction because the likely hood of fatality is high
...


END OF MATERIAL FOR MIDTERM EXAM

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LECTURE: EVOLUTION
Linnaean Classification System:
• Kingdoms: groups of things that were fundamentally different; Animalia, Plantae,
Fungi
• Phylum: smaller subgroup of kingdom based on similarities
• Class: each phylum subdivided into different classes
• Order: each class subdivided into orders
• Family: each order subdivided into families
• Genus: each family into different genera
• Species: within genus can have different species

• Another group added above Kingdom = Domain
• 3 different domains: Eukarya, Archaea, Bacteria
• Within Eukarya - at least 3 Kingdoms - Animalia, Plantae, Fungi
• Dumb
• King
• Philip
• Comes
• Of
• Fairly
• Good
• Stock
• Mnemonic device

Lecture: Evolution

Evolution: an inheritable change from one generation to the next in characteristics of
individuals in a population

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The History of Life on Earth: Living things have evolved by descent with modification
from common ancestors

Natural Selection: A functional association between individual traits and average
reproductive success

Darwin’s Observations:
• Organisms differ from each other, they are variable
• Some of the differences among organisms are inherited
• More organisms are produced than survive to reproduce in their turn
• Some of the carnations among organisms will affect their ability to survive and
reproduce
• Natural Selection is when organisms with certain characteristics tend to produce
more offspring than other organisms in the same population
• If natural selection acts on a characteristic that is inherited then evolution may result

Scientific Terminology
Hypothesis: a statement of what might be true
Fact: A hypothesis “confirmed to such a degree that it would be perverse to withhold
provisional consent”

The Evidence for Evolution
• The Fossil Record: mineralized remains of organisms
• Evolution does not predict that there will be fossilization
• Evolution predicts a pattern: any fossils found will be consistent with descent with
modification from common of ancestors
• Each of the billions of fossils found is a test of evolution

Timeline
• Earth about 4
...
5 BYA: fossil prokaryotes
• 2
...
5 BYA: Fossil Multicellular
• 7-800 Million Years Ago: Fossil Animals
• 500 MYA: Fossil Fungi
• 250 MYA: Fossil Plants
• First see different domains and then different kingdoms

Last 500 Million Years
• 4
...
5 MYA: Amphibians
• 3 MYA: Reptiles
• 250 MYA: Fossil Mammals
• 50 MYA: Fossil Animals

Last 50 MYA
Homo Sapiens - around 150,000 years old

Fossil Transitions
Between intermediate forms and earlier forms

BioChemistry
• Pseudogenes: a gene that has a couple of breaks; particularly in the promoter, so it
doesn’t get transcribed
• Universality of DNA as genetic material:
• Universality of Codons: all living things use exactly the same set
• Pattern of genetic similarity

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Wednesday, January 7, 2015
Comparative Anatomy
• Homologous Structures: demonstrate common descent
• i
...
Same underlying set of bones - same structure
• Structures in different species that are similar because of common ancestry
• Vestigial structures: demonstrate descent with modification
• A feature of an organisms that is historic remnant of a structure that served a
function in the organism’s ancestors
• Superfluous embryonic structures: demonstrate descent with modification
• Agrees with fossil record and biochemical evidence

HUMAN EVOLUTION
** See Human Evolution Comparison Chart ***

Lecture: March 4th

Natural Selection
• Evolution may defined as a change in allele frequency over time
• Natural selection does not result in evolution if the characteristic is not inherited
• If there is no genetic difference between individuals
• Natural selection does not necessarily result in evolution if the characteristic is
inherited

Modes of Selection
• Directional Selection: natural selection in which individuals at one end of the
photooptic range survive or reproduce more successfully than do other individuals
• Stabilizing (Balancing) Selection: Natural selection in which intermediate phenotypes
survive or reproduce more successfully than do extreme phenotypes
• Disruptive Selection: Natural selection in which individuals on both extremes of a
phenotypic range survive or reproduce more successfully than do individuals with
intermediate phenotypes
...

• Natural selection can act directly through reproductive rates
...
) Epithelial Tissue - Surface tissue
• Cuboidal Cells - rounder cells
• Columnar Cells - column cells
• Squamous Cells - flat cells
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Wednesday, January 7, 2015
• Simple: Single layer of cells
• Stratified: Multiple layer of cells
• 2
...
) Muscle Tissue - Contracting
• Skeletal - Voluntary control
• Smooth - Found in internal organs; fibres are shorter and tapered
• Cardiac - Has ribbed appearance of skeletal, not under voluntary control
• 4
...
g
...
) Enteric Division: basic digestive functions
• 2
...
) Sympathetic Division: fight or flight response

Senses
• Initiating action potentials in response to specific stimuli
• Mechanoreceptors: respond to mechanical force
• Chemoreceptors: respond to specific chemicals
• Electromagnetic receptors: respond to electromagnetic energy
• Thermoreceptors: respond to temperature
• Pain receptors: respond to damaged tissues

Statocyst:
• Have mechanoreceptors that form a hollow ball
• The statolith tend to settle at the bottom of the cilia due to gravity, tell the animal which
way is up
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Wednesday, January 7, 2015
Human Hearing
• Outer Ear, Middle Ear, and Inner Ear
• Outer ears has 2 parts:
• Pinna: the visible portion, helps to direct sounds waves into the ear
• direct sound into the auditory canal
• Middle Ear: auditory canal goes along until it hits the Tympanic Membrane which
seals off the aer
• Sounds hit the Tympanic Membrane and make it vibrate and vibrations are
transferred to the ossicles of the middle ear and transfer them to the inner ear
• Inner ear: main part concerned with hearing is the cochlea
• Basilar Membrane: has hair cells sitting on top of it that are mechanoreceptors
• Fluid transmits the pressure waves and press on the basilar membrane causing it to
move up and down
• The hair cells bash up and down with the membrane above it causes the
mechanoreceptors to initiate an action potential which is carried to the brain
• The Basilar membrane is not uniform; different parts of it will vibrate depending on
the frequency
• Also contains the vestibule, and semicircular canals

Human Balance
• Semicircular canals: that are all perpendicular to each other
• The fluid in the ears continue to move if you move in a circle which trigger action
potentials which tell the brain that you’re still moving

Chemoreceptors
Human taste
• Taste Buds: clusters of chemoreceptors on the tongue

Human Smell
• Chemoreceptors embedded within the epithelial cells

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Wednesday, January 7, 2015
Electromagnetic receptors:
• usually taking about light - eyes
•

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