tsfx unit 4, 2014 final revision lecture · replicating its genetic material, the cell divides into...

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TSFX Unit 4 2015AOS 2‐Change Over

Time

Veronica ParsonsVeronica Parsons 2015

2013 Exam

Veronica Parsons 2015

Revision‐What Can you Do Semester 2?

• Lecture today-Listen!• Past VCAA Exams from

Website Going Backwards from 2014 including Sample. Start printing or collecting and keep in a folder. Aim for 15 by EOY

• Keep Notebook Close by divided into 4 sections for each area of Study-write down theory from questions you are getting wrong

• Read over TSFX notes with highlighter regularly.

• Each week, write one dot point on 20 areas of Unit 3.

• Study Groups-Make Kahoots• Teach

• ATAR Notes Forum• VCAA Biology Page• GTAC Website• Youtube: Bozeman• Youtube: Crash course in Biology• Youtube: Mr W and Amoeba Sisters• Bioninja webpage• Douchy’s Podcasts• Study On Jacaranda• Checkpoints-Order now but save for

Swot Vac.• NEAP VCE Biology APP

My Favourite Resources

Look for Patterns and Make Acronyms

• STARR (Sample-Treatment-All Factors Same-Results-Repeat)• RUDD(Rapid Burial-Undisturbed-Decomposer Free-Downward

Pressure)• BADFEW(Biochemistry-Anatomy-Distribution-Fossils-Embryology-

Witness)• IPMAT (Stages of Cell Cycle)• UGA UAA UAG (Stop Codons)• COD (Cross with homozygous Recessive-Observe Offspring-

Decision)• VSSI (Variation-Struggle-Survival of Fittest-Inheritance)• VSSI with a B (Barrier)• GIFTS (Gene-Insert-From-Transform-Select)• Crocs Are Never Fine- (CO2-ATP-NADH-FADH2)• SHIP- (Storage-Hormones-Insulation-Protection-Structure)• HITSME ( Hormone-Structure-Immunity-Transport-Movement-

Enzymes)• CATSEXSPIRE (Catabolic-Exergonic=Respiration)

Exam Horror Stories

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Exam Horror Stories

2014 Exam Horror Stories

Exam Horror Stories

Drawing or Labelling a Plasma Membrane

AB

C

D

Exam Horror Stories

VCAA 2006 EXAM

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VCAA 2012


VCAA 2012


VCAA 2011 (2 Marks)


Answer


Plasma Membrane

Exam Questions Tricks• Name: 2 words• Compare: whereas• Explain: So So• Draw: Label & Simple• Don’t Repeat the

question.• Strucure (features)

Function (Role)-Don’t confuse

• Use data to support answers from tables or graphs.

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Part 1Human

Intervention

Part 2Change in Population

Part 3HomininEvolution

Area of Study 2

Unit 4: Change Over Time


Practice Exam Question


Binary Fission• All prokaryotic cells divide by

binary fission

• Basically, one cell splits into two!

• DNA replicates and attaches to

cell membrane

• Cell growth pulls DNA loops apart

(cytokinesis)

• Cell wall growth between loops

separates cell into two.


Binary FissionIt is the most common form of

reproduction in prokaryotes and occurs

in some single-celled eukaryotes. After

replicating its genetic material, the cell

divides into two equal sized daughter

cells. The genetic material is also equally

partitioned, therefore, the daughter cells

are genetically identical (unless a

mutation occurred during replication) to

each other and the parent cell. They

then split into two.


Cell Cycle


DNA REPLICATION


• DNA replication is the process by which DNA is copied and occurs in the S phase of interphase (part of the cell cycle)

• It involves unwinding and separating the double stranded molecule, before synthesising complementary strands to the separated templates

• DNA replication is a semi-conservative process, because when a new double-stranded molecule is formed:

• One strand will be from the original molecule• One strand will be newly synthesised

Stages of DNA Replication

• 1. Separation of DNA strands• Helicase unwinds and separates the double stranded

DNA by breaking the hydrogen bonds between base pairs

• DNA gyrase moves ahead of helicase and reduces the torsional strain created by the subsequent unwinding of the double helix

•

• 2. Synthesis of an RNA primer• RNA primase synthesises a short RNA primer on each

template strand to provide an attachment and initiation point for DNA polymerase

•

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DNA Replication cont…


• 3. Copying of the template strands • DNA polymerase adds nucleotides to the 3'

end of the polynucleotide chain, synthesising in a 5' - 3' direction

• The nucleotides pair up opposite their complementary base partner

o Adenine and thymine pair via two hydrogen bondso Cytosine and guanine pair via three hydrogen bonds

• DNA polymerase moves in opposite directions on the two anti-parallel strands

o Synthesis is continuous on the strand moving towards the replication fork (leading strand)

o Synthesis is discontinuous on the strand moving away from the replication fork (lagging strand) leading to the formation of Okazaki fragments

• 4. Removal and replacement of RNA primer• The lagging strand requires the addition of

multiple RNA primers to generate Okazaki fragments - these must be removed and replaced

• DNA polymerase removes the RNA primers and replaces them with DNA

• DNA ligase joins the Okazaki fragments together to create a continuous strand

MITOSIS


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HAPLOID vs DIPLOID • Haploid:

o One set of chromosomes

o In humans, number (n) = 23

o In humans, gametes (sperm & ova) are haploid

• Diploid:

o Two sets of chromosomes

o In humans, 2n = 46

o In humans, all body cells (other than gametes) are diploid


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CHROMOSOMES

• Homologous chromosomes are chromosomes that share the same structural features and the same genes, but may have a different combination of alleles


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PROCESS OF MEIOSIS

• Meiosis must occur in organisms that reproduce sexually to prevent doubling of the DNA during fertilisation

• Involves 2 divisions ‐Meiosis I and Meiosis II

• Occurs in the diploid germ cells in the gonads (testes & ovaries)


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PROCESS OF MEIOSIS

• Produces four daughter cells

• Gametes are haploid and not identical to original cell


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31

PROCESS OF MEIOSIS

MEIOSIS I1. Homologous chromosomes

pair up.

2. Non‐sister chromatids may cross over at points called chiasmata.They may exchange genetic material – crossing overduring prophase 1


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CROSSING OVER

& RECOMBINATION• Occurs in Prophase I

• Sections of non‐sister chromatids may touch (cross over).

• This point is called a chiasma (pl. chiasmata).

• Sections of the chromosomes may be swapped between the non‐sister chromatids.

• This produces recombinant chromosomes (ie. unlike either parent chromosome)

• Increases variation


PROCESS OF MEIOSIS

MEIOSIS I1. Homologous chromosomes pair up.

2. Non‐sister chromatids may cross over at points called chiasmata.They may exchange genetic material = crossing over.

3. Homologous pairs line up at equator.Maternal and paternal chromosomes of each pair line up independently of other pairs = independent assortment.

4. Homologous chromosomes separate and move towards opposite poles.If they fail to separate = non‐disjunction


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CHROMOSOMAL

NON‐DISJUNCTION• Occurs in Anaphase I

• Homologous chromosomes fail to separate properly.

• This is a form of chromosomal mutation.

• Extra or fewer chromsomes are drawn to each pole and packaged into the new cells.

• Results in trisomy (3 copies) or monosomy (1 copy)

• eg. Down Syndrome = trisomy 21

• The chance of non‐disjunction increases with maternal age. Ref: Biology Key

IdeasVeronica Parsons 2015

Genome• The genome is the total genetic

material of an organelle, cell or

organism.

• The proteome is the total protein

complement that can be

translated by a cell or individual

organism.

• A gene is a short section of DNA

that codes (structural) or

regulates (homeotic)for a

specific polypeptide/protein.


Gene Expression


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Transcription(the synthesis of RNA from a DNA template)

1. RNA polymerase attaches to the promoter

region of DNA upstream of the gene.

2. The double stranded DNA making up this

gene is unwound by the RNA polymerase by

the breaking of the weak hydrogen bonds

exposing unpaired bases on template

strand.

3. RNA polymerase constructs mRNA by

collecting free complementary RNA

nucleotides using the exposed DNA

template strand and attaching them

according to base pairing rule to form single

stranded pre-mRNA molecule.Veronica Parsons 2015

Pre‐mRNA• Pre-mRNA contains both

introns (non-coding ‘interruption’ nucleotide sequences) and exons (‘expressed’ nucleotide sequences).

• RNA is assembled in 5’ to 3’ direction


Post‐Transcription Modification

4. Enzymes cut out the introns and remaining exons are joined together.A methyl cap is added to one end of the molecule and a poly-A tail added to other.The shorter mRNA leaves the nucleus via nuclear pore.


Translation


1. Initiation: At the ribosome, the start codon AUG, causes the large subunit joins the small one to form a complete ribosome.

2. Elongation: A new tRNA+amino acid enters the ribosome, If its anticodon matches the mRNA codon it base pairs at the 3’ end and peptide bonds with the amino acid. The ribosome then moves one triplet forward and a new tRNA+amino acid can enter the ribosome and the procedure is repeated.

3. Termination: When the ribosome reaches one of three stop codons, termination proteins bind to the ribosome and stimulate the release of the polypeptide chain (the protein), and the ribosome dissociates from the mRNA.

Gene Regulation• There are 25000 genes in

human genome yet 400,000 proteins.

• Genes are regulated in different ways and one gene can code for more than one protein.

• One way may be differences in intron retention.

• One gene could produce one protein at different stages of development and in different tissues.


The Lac Operon• An operon is a cluster

of genes under the control of a single regulatory signal or a promoter.


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Identifying Active Genes• Microarrays-technology

to identify• Which genes are

active or switched off• Compare gene

expression in different cells

• Compare active genes in same cell under different conditions


Switching Genes Off• RNA interference (RNAi)


Gel ElectrophoresisFragments of DNA are separated according to their size and charge.DNA has an overall negative charge due to the phosphate groups.

DNA samples are placed in wells at the negative end of a piece of agar gel in a tray.

The wells are created by placing a plastic comb into the gel as it sets.

Positive and negative electrodes are located at each end of the gel.

When the electric current runs, the fragments are repelled from the negative electrode and move towards the positive electrode at the other end.

The smaller fragments travel faster than the larger fragments.

The DNA sample is mixed with a loading dye that attaches to the DNA before loading it into the gel.

This dye fluoresces under UV light, producing a discrete pattern of bands that can then be photographed.


Fragments Used in Gel Electrophoresis


1. RFLP’s (restriction Fragment Length Polymorphisms) sections of DNA produced by cutting homologous DNA strands with specific restriction enzymes. Different alleles have different numbers of recognition sites2. Intact alleles eg CC Cccc3. STR’s used in DNA profiling Short Tandem Repeats- DNA sequences of 2-5 bases which repeat egCATCATCATCAT

Polymerase Chain Reaction

Requirements• DNA to be copied• DNA polymerase (taq

polymerase) • Buffer solution that contains salts

and other chemicals that help the polymerase to function

• A supply of the 4 nucleotides• Two primer sequences of DNA :

The primers are short sequences of single stranded DNA, complementary to the nucleotide sequences at either end of the DNA section that is to be copied. These are necessary as a starting point from which the DNA polymerase can start adding new nucleotides.


Steps in Polymerase Chain Reaction

1. Denaturation: The double strand of DNA is heated to 950, breaking the hydrogen bonds between the bases, causing the two strands to separate.

2. Attachment of Primers: Temperature is reduced to 50-550C allowing the primers to anneal (join) to opposite ends of each strand. The reduced temperature is necessary to allow base pairing and the formation of hydrogen bonds.

3. Extension: The temperature is raised to 720C. starting from the primer molecules, new DNA strands are synthesised using DNA polymerase and the available nucleotides. There are now two copies of the double stranded DNA.

This cycle is repeated until sufficient quantities of DNA are obtained to work with. Just 20 cycles will produce over one million copies of the target DNA


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DNA Sequencing• 1. DNA is separated into single

strands, and a small starter piece of DNA called a primer binds to the template strand.

• 2. Extension - a new DNA strand is made that is complementary to the template strand. Starting at the primer, DNA polymerase uses the template strand as a guide to recreate the second DNA strand.

• 3. Termination dye-labeled terminator nucleotide,(ddNTPs) identifies the base at the position where strand extension stopped.

• Each labeled with one of four dyes, are now sorted by length using Gel electrophoresis.


DNA Profiling


• Identification depends on the existence of segments of DNA that vary greatly between individuals.

• Such regions of DNA are termed hypervariable.

• Short tandem repeats (STRs) or microsatellites. STRs are termed ‘short’ because the repeat sequences are only 2 to 5 base pairs long, and ‘tandem’ because the repeats occur one after the other. The number of repeats at an STR locus can vary between people and each variation is a distinct allele.

• Hypervariable regions (HVRs) in the non-coding region of mtDNA. mtDNAidentification is less precise because persons from the same maternal line have identical mtDNA profiles.

Labelled Chromosome


Allele• One specific form of a

gene, differing from

other alleles by one or

a few bases only and

occupying the same

gene locus as other

alleles of the gene.


Genotype


• The genotype of an organism is the inherited instructions it carries within its genetic code.

• Not all organisms with the same genotype look or act the same way because appearance and behaviour are modified by environmental and developmental conditions.

• Likewise, not all organisms that look alike necessarily have the same genotype.

• One's genotype differs subtly from one's genomic sequence.

• A sequence is an absolute measure of base composition of an individual, or a representative of a species or group; a genotype typically implies a measurement of how an individual differs or is specialized within a group of individuals or a species.

• So typically, one refers to an individual's genotype with regard to a particular geneof interest and, in polyploid individuals, it refers to what combination of alleles the individual carries homozygous, heterozygous).

• The genetic constitution of an organism is referred to as its genotype, such as the letters Bb. (B - dominant genotype and b -recessive genotype)

Phenotype


• A phenotype is the composite of an organism's observable characteristics or traits, such as its morphology, development, biochemical or physiological properties, phenology, behaviour, and products of behavior (such as a bird's nest). Phenotypes result from the expression of an organism's genes as well as the influence of environmental factors and the interactions between the two. When two or more clearly different phenotypes exist in the same population of a species, it is called polymorph.

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Variation‐the spice of life• Genetic variation, variation

in alleles of genes, occurs both within and among populations.

• Genetic variation is important because it provides the genetic material for natural selection.

• – the causes of phenotypic variation: mutations; recombination of parental alleles in sexual reproduction; polygenes; and interactions of environmental factors with genes


Polygenes

When characteristics are controlled by more than one gene.Examples are height, skin colour, tail length, hair colour.Traits controlled by polygenes are said to show continuous variation.Often it is the number of dominant alleles for the genes that determines the variation shown.


Inheritance Terminology


One gene can have several alleles (forms/variations). The alleles are normally assigned letters. The dominant is given the Capital letter and the recessive the lowercase of the same letter.

Homozygous (Pure breeding): Alleles for the one gene are the same. (For Example: A A).

Heterozygous: (carrier/hybrid) Alleles for the one gene are different. (For Example: Aa).

Dominant: If the allele is present in the heterozygous genotype it will be expressed, always written with a capital letter. (For Example: A).

Recessive: Only expressed if in homozygous state, no allele is present to be expressed. Always written with a small letter. (For Example:a).

F1 = First filial generation, the offspring from 2 pure breeding parents.

F2 = Second filial generation, the offspring resulting from a cross between 2 F1 or the

A monohybrid cross

Inheritance Terminology


• To get the above predicted ratios you need a lot of offspring to be produced. Often in humans there is not enough offspring to show the predicted results.

• Also the predicted results/ratios are the same for each offspring as the gamete predictions are the same for each sperm of egg produced.

• Note if the question asks for phenotype or genotype ratios, you must give a ratio such as 3 Normal : 1 Affected. If the question asks for genotype or phenotype probabilities, you must give either a fraction or decimal such as 75% Normal, 25% Affected.

• Important-traits are dominant or recessive. It is incorrect to say genes or alleles are dominant or recessive.

Co Dominant‐Multiple Alleles


• Some genes have more the 2 alleles. For Example: The blood group gene called the ABO gene.

• Each person has 2 copies of the ABO blood group gene. The gene is found on chromosome 9.

• There are 3 alleles (versions) of the gene. However, because we only have 2 copies of chromosome 9 we can only have a maximum of 2 versions at one time.

• If the 2 dominant alleles are together in the cell the individual shows the phenotype

• AB type blood. We call this a co-dominantsituation.

• Multiple allele genes usually show more than 2 phenotypes.

Dihybrid‐Unlinked


• The two genes are independent genes meaning that they are found on different chromosomal pairs.

• Let T = tall, t = dwarf and R = red and r = white for a certain plant.

• If two TtRr individuals are crossed then the predictable result is:

• 9 tall and red: 3 tall and white :3 dwarf and red :1 dwarf and white

• A total of 16 possibilities.

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Dihybrid‐Linked


• Genes that are located on the same chromosomes are termed linked.

• Because the genes are on the same chromosome they are always inherited together. Certain alleles for the different genes can be carried together but the allele combination can be altered by crossing over during meiosis

Test Cross (COD)


• To check if an individual’s genotype is homozygous dominant (say BB) or heterozygous (say Bb) we can use a test or back cross.

o

• In mice B=black and b=white. A black mouse was found by a student and they wanted to know if the mouse was homozygous or heterozygous. Show a back cross to answer the question.

Sex Linkage


Autosomal DominantFor Example: Huntington’s disease,

Alzheimer’s disease, achrondroplasia

(dwarfism)

An idealised pattern includes:o both males and females can be affected

o all affected individuals have at least one affected

parent

o transmission can be from fathers to daughters and

sons, or from mothers to daughters and sons

o once the trait disappears from a branch of the

pedigree, it does not reappear

o in a large sample, approximately equal numbers

of each sex will be affected.

o Two heterozygous parents can have recessive

offspring with a different phenotype.


Autosomal RecessiveExamples: Albinism, CF, thalassemia.

An idealised pattern includes:o both males and females can be affected

o two unaffected parents can have an

affected child

o all the children of two persons with the

condition must also show the condition ie. 2

recessive parents will have affected children

o the trait may disappear from a branch of the

pedigree, but reappear in later generations

o over a large number of pedigrees, there are

approximately equal numbers of affected

females and males.


Sex Linked Dominant• For Example: A form of

rickets.

• An idealised pattern includes:

o An affected male will pass the trait to all his daughters.

o An affected father cannot pass the trait to his sons.

o A homozygous female will pass the trait to all her daughters and sons.

o every affected person has at least one parent with the trait

o If the trait disappears from a branch of the pedigree, it does not reappear

o over a large number of pedigrees, there are more affected females than males.


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Sex Linked Recessive• For Example: Red/green

colour blindness, haemophilia, muscular dystrophy.

• An idealised pattern includes:o All sons of an affected mother show the

trait.o For an affected female to show the trait

her father must be affected.o all the daughters of a male with the trait

will be carriers of the trait and will notshow the trait; the trait can appear in their sons

o none of the sons of a male with the trait and an unaffected female will show the trait, unless the mother is a carrier

o all children of two individuals with the trait will also show the trait

o in a large sample, more males than females show the trait.


Tools and Techniques

Gene technology involves removing and introducing DNA into new cells and therefore requires tools for synthesising, cutting and pasting DNA, plus tools and techniques for viewing and analysing.

Tools

Gene Probe

Primer

DNA Ligase

Reverse Transcriptase

Restriction enzyme

DNA Polymerase (eg Taq)

TECHNIQUES

PCR (polymerase chain reaction)

Gel Electrophoresis

DNA Sequencing

DNA Hybridisation

Making a Recombinant Plasmid

Bacterial Transformations

DNA Profiling

Gene Transfer using Plasmids

GM (genetic modification)

CloningVeronica Parsons 2015

Book 2 Page 38 Genetic Engineering


G= Gene of InterestI= Insert into VectorF= From Vector to CellT= TransformationS=Select

Pg 43 Transformation of Bacteria


Genetic Engineering

Transformation

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Gel Electrophoresis

Pg 49 Gel Electrophoresis


Book 3 Pg 1 Human Intervention


• Selective breeding is where a mating is

decided to give the offspring the

desired genes of the parents.

• Are Designer Babies considered

Selective Breeding?

• In designer babies the parents have

chosen each other as partners and have

decided to have a baby. There is then

selection of the embryo with the

desired characteristics/phenotype.

Pg 3‐ Reproductive & Therapeutic Cloning

• Issues• Increase in cures for diseases vs

destruction of human embryos with human potential

• Allowing individuals that would not naturally survive to live. It does this by directly inhibiting the action of natural selection against individuals with disadvantageous phenotypes.

• Natural selection will not be able to act against individuals with the condition and the frequency of the allele causing the condition will not be lowered. As a result, the condition will remain in members of a population when its occurrence should naturally decrease.


Pg 3 Telomeres• The older the animal is, the shorter its

telomeres will be, because the cells have divided many, many times.

• So, what happens to the clone if its transferred nucleus is already pretty old?

• Will the shortened telomeres affect its development or lifespan?

• When scientists looked at the telomere lengths of cloned animals, they found no clear answers.

• Chromosomes from cloned cattle or mice had longer telomeres than normal.

• On the other hand, Dolly the sheep's chromosomes had shorter telomere lengths than normal. This means that Dolly's cells were aging faster than the cells from a normal sheep.


Pg 3‐ Categories of Stem Cells

Description of Stem Cell

Potential of Stem Cell Example

Totipotent all Embryo

Pluripotent many Embryo

Multipotent Some Adult Somatic‐Bone Marrow


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Pg4 Transformation & Transfection


Issues• Loss of genetic diversity

(loss of alleles from a population)

• These alleles may have the potential to protect the population in case of disease, natural disaster, sudden change.

GMO Mosquitos


Book 3 Pg 13‐ Speciesthen Q6 pg 26


• Interbreed to produce fertile, viable offspring.

Or

?• Based on similarity of DNA of

individuals or populations. Techniques to compare similarity of DNA include DNA-DNA hybridization, and genetic fingerprinting (or DNA barcoding).

• Note DNA is an organic molecule-400000y

Pg 15 GENE POOL

• The genetic information present in a population of organisms.

• Expressed in terms of the frequencies (proportions) of the various alleles in a population.

• Agents that can cause allele frequencies to change over time include: selection (natural &artificial) migration and chance.


Pg 16‐Gene Flow‐MIGRATION AS AN AGENT OF

CHANGE

• Migration, also known as gene flow, can change the allele frequencies of a population.

• changes due to migration can occur very quickly.

• Emigration can also change allele frequencies if the emigrant group is not a representative sample of the original population.

• Imagine a small population that comprises mainly homozygous AA but a few heterozygous Aa and homozygous aa. If all the heterozygotes and the homozygous aa organisms emigrate from this population, the allele frequencies are altered immediately. The gene pool now contains only one allele for the trait concerned. When only one allele is present in the gene pool of a population, the allele is said to be fixed.


Pg 17 CHANCE AS AN AGENT OF CHANGE

• In a very small population, genetic drift can lead to the decrease, andeventual loss, of favourable alleles from the gene pool.

• For this reason, when a species is reduced to one or a few small populations, the species is at great risk of extinction.

• Genetic drift is important when the size of a population is drastically reduced by a major calamity, such as a widespread fire or flood.

• The few survivors that reproduce to give the next generation may by chance be an unrepresentative sample of the original population.

• This is known as the bottleneck effect. • So,when a small unrepresentative

sample of a population leaves to colonise a new region, this is known as the founder effect.


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Book 3 Pg 20‐Natural Selection (VSSI)

•V ariation

•S truggle for survival

•S urvival of Fittest

• I nheritance


Evolution in Action‐Tasmanian Devils


• Devils may be responding to DFTD by breeding earlier — before they are likely to be killed by the disease.

• Before the disease, most females began breeding at two years of age and that many devil females now begin to reproduce at just one.

• Females with genes for early-breeding would have a significant reproductive advantage over females with genes for standard breeding times, and because of this differential reproduction, the population may have evolved.

• Alternatively, it could be that the genetic makeup of the population has not changed, but that with reduced competition from older females and with more access to food because of diminished devil populations, younger females are now able to breed.

• The idea here is that devil populations always had the potential for early breeding but that this was previously suppressed by competition from other devils.

• A phenomenon known as phenotypic plasticity — alternate traits an organism might have depending, not on different gene versions, but on the organism's current or past environment.

• Devils used to be broadly distributed across Australia. • When sea levels rose 12,000 years ago, a small number of devils on Tasmania were cut off

from the mainland population, which soon went extinct. • This founding population of modern Tasmanian devils did not have as many different gene

versions as the larger population had had, resulting in a serious cutback in genetic variation. • Though the Tasmanian population grew in numbers after it was isolated, it was stuck with a

low level of genetic variation and passed this deficiency on to modern devil populations. • Because there is little variation in the genes that form the basis of their immune response —

and because their aggressive breeding behavior allows cell exchange — devils provided a unique opportunity for the evolution of a contagious cancer.

VSSI Devils• Variation existed in an ancestral population of

Tasmanian Devils in relation to breeding age in females.

• The prevalence of the DFTD resulted in a struggle for survival

• Those devils with the allele for earlier breeding are considered ‘fit’ as they are more likely to survive and have an offspring before catching the disease passing on this allele.

• Over time this gene has become more prevalent in the population through inheritance so that devils are more likely to breed earlier.


Pg 21 Selection acts on phenotypes

• In a polymorphic population living under certain environmental conditions, different phenotypes may have different survival and reproductive rates.

• A phenotype that makes the greater contribution to the gene pool in the next generation has a higher fitness value and is said to be ‘at a selective advantage’.

• The phenotype that makes a lesser contribution is termed ‘less fit’ or is said to be ‘selected against’.

• The agent that causes these differences to occur between phenotypes is the selecting agent.


Pg 22 Isolating Mechanisms

Prezygotic Postzygotic


• prevent mating or fertilization between different species

• temporal isolation: when different species reproduce at different times

• habitat isolation: the species remain isolated because they breed in different habitats.

• behavioral isolation: the species have differences in mating rituals

• mechanic isolation: the species are physically unable to reproduce

• reproductive barrier that operates should interspecies mating occur and form hybrid zygotes

• hybrid inviability: the offspring (called a hybrid) does not survive

• hybrid sterility: the hybrid is infertile

• hybrid breakdown :the first-generation hybrids are viable and fertile, but when they mate the offspring are feeble and sterile

Pg 27 EVOLUTION WITHIN A SPECIES

VBSSI

• V ariation• B arrier (no gene flow)• S election pressures

different in different environments

• S urvival of fittest different• I nheritance• S pecies; when

reintroduced cannot interbreed to produce fertile viable offspringVeronica Parsons 2015

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Pg 28 Instant Speciation by Polyploidy

• Polyploidy may arise during meiosis resulting in sudden reproductive isolation from parent species.

• From plants produced reproduction can occur vegetatively or via self pollination resulting in a breeding population.

• Allopolyploidy often arises in plants with the doubling of chromosomes in a hybrid between 2 species the doubling makes the hybrid fertile.


2010 ‐3 marks

2008 ‐3 marks

2007 ‐3 marks


Pg 30‐Extinction


• A diverse or deep gene pool gives a population a higher chance of surviving an adverse change in conditions.

• Effects that cause or reward a loss in genetic diversity can increase the chances of extinction of a species.

• Population bottlenecks can dramatically reduce genetic diversity by severely limiting the number of reproducing individuals and make inbreeding more frequent.

• The founder effect can cause rapid, individual-based speciation and is the most dramatic example of a population bottleneck.

Pg 31‐BADFEW‐Evidence for Evolution


• B= Biochemistry• A= Anatomy• D= Distribution• F=Fossil Record• E= Embyology• W=Witness

Pg 41 Biochemistry


• The genome of each species contains DNA sequences and distinctive features that have been conserved over millions of years of evolution.

• Because living species have evolved from common ancestors, the genomes of related species exhibit similarities.

• The more recent the divergence of two related species from a common ancestor, the greater the degree of conservation of DNA sequences (less time for mutations) and of their arrangement within the genome.

Pg 42 Mitochondrial DNA

• The coding region of mtDNA mutates very slowly, but two non-coding regions in the D-loop of mtDNA have a higher mutation rate.

• Lacks recombination unlike nuclear DNA

• The mtDNA in each of your cells was inherited from your mother — she received her mtDNA from her mother (your maternal grandmother), and she in turn received her mtDNA from her mother (your great-grandmother) and so on, back through thousands of generations.

• Different mutations occurred over time in the mtDNA of various women and, once present in a population, these mutations were faithfully transmitted from mother to offspring across each generation.


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Geological Time Scale


Pg 44 Fossils• R apid Burial• U ndisturbed• D ecomposer Free• D ownwards Pressure


• Evidence of prehistoric life.• Found in sedimentary rocks,

amber, tar, peat, bogs etc• Include whole bodies (rare),

bones, teeth, shells and Trace Fossils-footprints, tracks, coprolites (dung), pollen etc.

• Soft parts decay quickly while hard marts can undergo mineralisation, a process that turns sediment into hard rock.

• Indication of earlier climates, lifestyles, age of rocks, diet etc.

Pg 49 Transitional Fossil


• Archaeopteryx is a genus of early bird that is transitional between feathered dinosaursand modern birds.

Pg 48 Relative Dating


• Sratigraphy; presumed lowest stratum is oldest

• Index fossils : used to define and identify geologic periods based on the premise that, although different sediments may look different depending on the conditions under which they were laid down, they may include the remains of the same species of fossil.

• If the species concerned were short-lived (in geological terms, lasting a few hundred thousand years), then it is certain that the sediments in question were deposited within that narrow time period.

Pg 53 Absolute Dating


• Determines with accuracy the actual age of a rock or fossils.

• Radioactive Dating-Measures decay rates (half life) of radioactive isotopes.

• Time taken for half of the atoms in radioactive sample to decay.

• Thermoluminescence- used to date human artefacts egcooking utensils.

• Measures light emissions from minerals when heated.

• The intensity of light emitted from objects provides measure of time passed since object was heated

Absolute Dating


Dating Method

Description Dating Range Dating Material

Radiocarbon C14 100‐50,000 years Organic‐Bone, Shell, Charcoal

Potassium‐Argon Radioactive element 100,000‐4.5 billion Volcanic rocks & Minerals

Uranium Series Decay 10 million to 4.5 billion Marine carbonate, coral. shell

Thermoluminescence Measuring accumulated radiation for time elapsed since exposed to heat or sunlight.

1000‐500,000 years Ceramics (burnt clay)

Electron Spin Resonance

Measuring time taken for excited electrons to return to ground state in buried objects to measure time object was last heated or exposed to sunlight.

1000’s to millions Bone, teeth, pottery, burnt flint or fire treated tools.

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PhylogenyThe classification of organisms into groups

is called taxonomy. The best taxonomic schemes are based on relationships due to common ancestry, not just on physical similarities. Evolutionary based classification is called phylogeny.

When devising a phylogenetic classification scheme, taxonomist must ensure that they use homologous structures as opposed to analagous structures.

The aims of phylogenetic classification are to

- assist in the identification of organisms- suggest evloutionary links- allow the prediction of characteristics

shared by other members of the taxonomic group.


Pg 32 Convergent & DivergentEvolution

Divergent Convergent


Pg 52 Marsupial Evolution


• Much variation between mammals of Africa, South America and Australia.

• These 3 land masses have long been separated by oceans of water so evolution in each region has been uniquie.

• The ancestors of Australia’s mammals were isolated from other mammal species when the Australian continent separated from Gondwana(Mesozoic-180mya) before the ancestors of most other land mammal groups were able to colonise the continent.

• Since then Australian marsupials have evolved to occupy niches that have been filled by placental mammals on other continents.

• Mammals of northern hemisphere show less variation. The continents have only been separated by narrow straits so movement across continents has not been as difficult

End of Part 2• Complete the following on pages 84- 86• 14, 15, 16, 17, 18, 19, 20, 21.


Pg 63‐Human Taxonomy


• Historically, modern humans were classified as hominids, from the family name Hominidae

• Great apes were placed in a separate family (Pongidae)

• Now, all the great apes have been placed in the family Hominidae, and humans have been placed into the sub-familyHomininae

• The term hominin now refers to all species (including modern humans) that have evolved since the human lineage split off from the one that gave rise to the great apes

•

Pg 66 Human vs Gorilla


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Ancestral Primate


• Around 8 million years ago (in the late Miocene epoch), a simultaneous global cooling and drying trend created a climate change in Africa, which split the hominin sub-family into two distinct populations

• One population remained in the wet rainforests of western Africa and gave rise to modern chimpanzees (genus = Pan)

• The other population adapted to the increasingly open, dry habitats of east and north central Africa, and eventually gave rise to modern humans (genus = Homo)

•

Origin of Homo sapiens


• Bipedalism developed in late Miocene to early Pliocene hominins (~6 - 4 m.y.a), possibly in response to more open habitats

• An adaptive radiation of African homininstook place between 4 to roughly 1.7 million years ago in response to further climate changes

• In the period between 1.7 million years ago and the present, there has been an explosive geographic expansion and rapid divergence of the genus Homo (including a dramatic increase in cranial capacity)

• This expansion has been followed by a subsequent reduction in species richness until only one lineage of the Homo genus remains - Homo sapiens sapiens (modern man)

• Anthropologists are divided as to whether current human populations evolved in Africa before migrating around the globe ('Out of Africa' model), or evolved as one interconnected global population ('Multiregional' Hypothesis)

Hominin Evolution


• By comparing the different types of hominin fossils, we can identify key evolutionary trends:

• More downward facing foramen magnum (caused by a transition to bipedalism)

• S-shaped curvature of the spine (an artifact of an increasingly erect posture)

• Lower and broader pelvis (bipedalism has changed the hominin birthing patterns and behaviours)

• Change in relative lengths of arm and leg bones (arms have become relatively shorter and legs longer due to walking upright)

• Increased size of heel bone and alignment of big toe (changes in feet to become greater weight-bearing structures)

• Flatter faces, with reduced brow ridges and jaw protrusion (head is no longer the most anterior part of the body)

• Larger cranial capacity with increased brain size and greater encephalisation (greater intellectual prowess)

• Smaller teeth and jaws more V-shaped (reflecting changing dietary requirements with less emphasis on tough vegetation)

• Marked reduction in body hair (improved hunting and cultural practices have lead to the development of warm clothing)

• Shift in muscle groups (particularly the gluteal and hamstring groups in order to accommodate new mode

Early Hominins


• Early hominins first appear in the fossil record approximately 4 million years ago

• Collectively, they were very ape-like in structure - with a prognathic profile and longer arms, they were likely facultative bipeds (arms used for support)

• They had large jaws, broad molars and thicker enamel, indicating a diet that was heavily dependent on nuts, grains and hard fruits

• They had a relatively small cranial capacity (roughly 300 - 450 cm3), indicating smaller brains

o Ardipithecus ramidus (~4.4 m.y.a) is one of the oldest fossils and was very ape-like in appearance, with wider zygomatic arches and a sagittal crest

o Australopithecus afarensis (~4.0 m.y.a) and A. africanus (~2.5 m.y.a) had non-opposable big toes and were likely the first bipeds (facultative)

Early Homo


• Early Homo species first appear in the fossil record approximately 2 million years ago

• Compared to Australopithecines, they had a marked increase in brain size (cranial capacity ~ 700 - 1,000 cm3) and reduced sexual dimorphism

• They had a reduction in the size of their teeth, indicating a change in diet and further skeletal changes to support a more erect posture

o H. habilis (~2.0 m.y.a) are thought to be among the first to use stone (Oldowan) tools, with shortened digits suggesting the use of precision grip

o H. erectus (~1.6 m.y.a) was the first to widely distributed thoughout the Old World, may have used fire and possessed rudimentary language

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Late Homo


• Late Homo species first appear in the fossil record under 1 million years ago (~800,000 y.a)

• These species have a significantly increased cranial capacity (~1,300 -1,500 cm3) and demonstrate advanced cultural and technological practises

o H. heidelbergensis (~600,000 y.a) were among the first to bury their dead and are thought to be a direct ancestor of H. sapiens

o H. neanderthalensis (~200,000 y.a) used Mousterian (flint-flake) tools and likely co-existed at the same time as H. sapiens

o H. floresiensis (~80,000 y.a) has been nicknamed 'hobbit' for its small size; debate exists as to whether it is a separate species or a primitvehuman with major genetic deformities

• At some point between 200,000 and 100,000 years ago, a population of early humans crossed the morphological threshold to become modern humans: Homo sapiens sapiens

•

The ʺOut of Africaʺ View• According to this theory,

early modern humans o evolved Homo erectus in Africa, o whose offspring then migrated

from Africa, • perhaps as recently as

100,000 years ago o and populated Europe and Asia, o Out competing &driving the

earlier homini populations to extinction

• Evidence• Modern humans should appear first in

Africa and only later in other parts of the world.

• Transitional fossils from ancestral to modern humans should only be found in Africa

• Variation in mtDNA should be greater in African populations than other poopulations


The ʺMultiregionalʺ View• According to this

hypothesis, o early modern humans did not have

an isolated origin in Africa, o but rather established separate

populations throughout Eurasia• Occasional contact and

interbreeding o between these populations

enabled our species to maintain its overall cohesiveness,

o while still preserving the regional differences in people we see today

Evidence• Modern humans should appear

throughout Africa, Asia & europeduring the same period.

• Transitional forms should be found in Africa, Europe &Asia

• Variation in mtDNA should be approximately the same in human populations from all regions of the Old World.


Pg 82 Cultural Evolution


• Cultural evolution occurs through the development of customs and languages, and involves the transfer of information either within a generation or across many generations

• Any unit of cultural information, such as a practice or an idea, that gets transmitted verbally or by repeated action from one mind to another, is called a meme

Examples of cultural evolution include the change in lifestyle of modern humans from nomadic hunter-gatherers to permanent settlers who domesticated animals and adopted agricultural practices• Evidence of human culture, such as

musical instruments, cave paintings and burial practices, can be seen as early as the Lower Palaeolithic period

Pg 83 Technological Evolution


• Technological evolution refers to the changes over time in technology that give humans increased control over their environment

Examples include• the change from stone

tools to metal tools• development of industrial

technologies (such as steam and electric power),

• agricultural and medicinal procedures

• communication resources (such as the internet) and space travel


tsfx unit 4, 2014 final revision lecture · replicating its genetic material, the cell divides into...

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