Biology U4 AOS 2

• Gene pool

• Alleles

• Allele frequencies + how to calculate?

• Genetic diversity

Gene pool all alleles present within a particular population or species 

Alleles are alternate forms of a gene 

 

Allele frequencies refer to the proportion of a particular allele appearing at a certain gene locus in a gene pool 

• Which can be calculated by totalling the number of a particular allele divided by the total number of alleles present in the population 

 

A larger and more diverse gene pool will contain a greater variety of genes and alleles, leading to a greater number of genotypes and phenotypes, and thereby resulting in increased genetic diversity - variation in genetic makeup or alleles within a population 

• Genotype

• Phenotype

• Genotype the genetic composition of an organism at a particular gene locus/combination of alleles for a specific trait 

• Phenotype the observable physical or biochemical characteristics of an organism that are influenced by gene expression and the environment 

• Mutations

• How can they occur?

• Depending on the mutation’s overall effect on the survivability of the individual affected, the mutation can be classified as —--, —— or —-

Mutations involve permanent changes to the DNA sequence of an individual  

• They create new alleles 

• They can occur either spontaneously or be induced by agents known as mutagens (e.g. UV radiation) 

 

Depending on the mutation’s overall effect on the survivability of the individual affected, the mutation can be classified as advantageous, neutral, or deleterious  

For these mutations are they heritable

• Germline cell mutation

• Somatic cell mutation

• For the mutation to be heritable (passed down from parent to offspring), it must occur in an individual’s germline cells (involved in the generation of gametes) 

• If the mutation occurs in a somatic cell, then it is not heritable 

Point mutations 

Describe changes to a single nucleotide in a gene  

• Silent mutation 

• Why is it this way (Hint: nature of genetic code)

• T or F? f the last nucleotide in the sequence is substituted, then the mutation is less likely to be silent 

• Missense mutation 

• Does it always alter the functioning of the protein?

• Nonsense mutation 

• T or F? These mutations are generally considered the most dangerous when they are early in the sequence

Frameshift mutation 

• Block mutations + list the different types

• Deletion

• Duplication

Involve changes to larger sections of DNA or an entire gene 

• These mutations usually occur during the process of meiosis

Different types include:

• Deletion

• Duplication

• Inversion

• Translocation

• Inversion

• Translocation + what can it be further classified as? Explain

• In inversion – the section breaks off,  rotates 180°, and reattaches to the same chromosome 

• In translocation, it could classified as balanced (No extra/missing DNA (fertility may be reduced) or unbalanced net extra/missing DNA, less functional organism 

• Aneuploidy

• Polyploidy

• Draw a image of an example of the above on a karyotype

• Aneuploidy refers to a chromosomal abnormality in which an organism possesses an incorrect number of total chromosomes caused by the addition or loss of an individual chromosome 

• Polyploidy refers to a chromosomal abnormality in which an organism has an incorrect number of sets of each chromosome  

• Environmental selection pressures

• Give examples

Environmental selection pressures are factors within the environment that influence an organism’s ability to survive and reproduce, hence influencing allele frequency in a population 

 

Examples – don't need to memorise just know 

Physical agents	Biological agents	Chemical agents
Climate conditions  Extreme temperature changes  Drought  Competition   Food  Water  Shelter  Mates	Infectious disease  Predation	Pollutant in soil or water  Pesticides

• Natural selection

• What are the 4 basic conditions that facilitate natural selection

Natural selection a mechanism for evolution in which organisms that are better adapted to their environment have an increased chance of surviving and passing on their alleles

Evolution 

Evolution the change in the genetic composition/allele frequencies of a population over consecutive generations 

• Natural selection is a mechanism of evolution 

The survivability of a species relies upon a population having large genetic diversity. Explain why:

--> This is because a population with a greater variation in alleles has a higher chance of possessing a favourable allele that will help them survive if a new selection pressure arises 

Describe evolution with this:

1. There is heritable, pre-existing variation of colour between green and brown beetles  

 

2. Predation of the crows acts as a selective pressure against the green beetles 

 

3. The brown beetles camouflage better with the environment. Their colour confers a selective advantage.  

 

4. Brown beetles are more likely to survive, reproduce and pass on their favourable traits The allele frequency changes over time where the frequency of the alleles specific to the brown phenotype increase, whereas alleles specific to green beetles decrease over generations. 

• Interbreeding

• Inbreeding

Interbreeding	Mating between individuals.
Inbreeding	Closely related individuals in a population mating and producing offspring.

Genetic drift + identify some of its forms

Genetic drift a random event that results in the removal of alleles from the gene pool which reduces a population's genetic diversity 

• This occurs through either the bottleneck effect or the founder effect 

Bottleneck effect

Bottleneck effect the reduction in genetic diversity that occurs when a large proportion of a population is removed due to a chance event (e.g. natural disaster) 

• Due to the severe reduction in population size, many individuals carrying unique alleles can be lost --> Therefore, the new population has lower genetic diversity than the pre-disaster population 

 

TIP to remember: 

• Bottle – some liquid (members of the population) has leaked out of the bottle – resulting in lower content within the population 

Founder effect

Founder effect the reduction in genetic diversity that occurs through the establishment of a new population that is derived from a small unrepresentative sample of the original population 

 

So: 

• Small group of individuals from a larger population  

• Move to a new location and establish an isolated population 

 

TIP to remember: 

• Founder – they found/establish a new population 

Outline which of these are founder effect and bottleneck effect:

A) In a multicolored population of beetles: 

• Due to a random event, the original population size is dramatically decreased, leading to the loss of various alleles 

• This significantly decreases the genetic diversity of the beetle population, leaving only green and yellow beetles 

B) There is a population of green beetles

• Ten green beetles left their original multicolored population to form a new population

C) There is a population of beetles of many different colors 

• If ten green beetles left their original multicolored population to form a new population - it would not mirror the initial gene pool and would therefore be considered an unrepresentative sample 

• This means that the genetic diversity of the new population is significantly lower than the original  

• Bottleneck effect

• Neither

• Founder effect

What are major risks associated with reduction in genetic diversity:

• Inbreeding sexual reproduction between two related individuals 

--> this keeps harmful alleles in the gene pool 

 

• Lower adaptive potential (the ability for a population to adjust to new environmental selection pressures) 

--> populations become vulnerable to new selection pressures as there is a lower possibility that they have the advantageous allele that could protect against the pressure – this could challenge and potentially wipe out the entire population 

• Gene flow

• T or F? It only decreases genetic diversity

• Immigration 

• Emigration 

Gene flow the exchange of alleles between populations due to the migration or interbreeding of individuals between two populations – this can either increase or decrease the genetic diversity  

 

• Immigration movement into a population  

• Emigration movement out of a population  

Explain whether it is immigration or emigration that

• Increases genetic diversity

• Decreases genetic diversity

• When individuals enter a population via immigration, their alleles are added to the gene pool of that particular population + when individuals temporarily enter a population and interbreed with local individuals, they contribute to the gene pool of that particular population – this increases the genetic diversity of that population 

• Conversely, when individuals exit a population via emigration, their alleles are removed from the gene pool, decreasing genetic diversity 

• Speciation

• T or F? It is a slow and gradual process

Speciation process by which new species arise from pre-existing/ancestral species 

• T. Speciation is a slow and gradual process 

When are two populations recognised as different species?

Individuals are recognised as different species if they can no longer interbreed with one another to produce viable (able to survive) and fertile (able to reproduce) offspring

List of genetic evidence techniques to see if populations are different species (bcs u can't always force them to try make babies with each other): 

• Comparing DNA sequences: 

Differences in nucleotide sequences within DNA molecules (or DNA hybridisation techniques) 

 

• Comparing mitochondrial DNA 

 

• Comparative genomics: 

Comparing whole genome sequences (differences between the two populations) 

Speciation requires two things. What are they?

• A division that prevents sub-populations from interbreeding successfully 

--> Division could include geographical barrier or reproductive barrier 

• No gene flow between populations (isolated gene pools) 

The mechanisms which prevent species from interbreeding to produce fertile and viable offspring can be categorised into pre- and post-reproductive isolating mechanisms (also known as pre-zygotic and post-zygotic isolating mechanisms) 

Give examples in each:

(However these mechanisms are unlikely to be assessed by the VCAA) 

Allopatric speciation + explain the process using an example

Allopatric speciation when populations are divided by a geographical/spatial barrier, preventing gene flow and hence resulting in the formation of a new species  

 

• Geographic barriers which is are physical factors that prevents gene flow, and thereby stops two populations from interbreeding – this includes the presence of a mountain range or the development of a river 

Note:

The Galápagos Islands are a collection of 19 islands situated in the Pacific Ocean west of Ecuador – where each of the 19 islands represents a specific ecological niche, each with its own different selection pressures and species 

• These islands are separated by the ocean, which serves as a geographical barrier, preventing gene flow between them 

• Organisms that inhabit these islands include the Galápagos finches, which are also known as Darwin’s finches – they all originated from one finch ancestral species (a ground dwelling, seed eating finch) 

--> Currently, there are 18 known species of Galápagos finches 

--> It has been hypothesised that the formation of these different species of Galápagos finches has largely been a result of allopatric speciation 

--> It has been hypothesised that the formation of these different species of Galápagos finches has largely been a result of allopatric speciation 

Sympatric speciation

Sympatric speciation the divergence of a species from an original species without the presence of a geographical barrier 

• Sympatric speciation occurs within populations sharing the same geographical location, where different selection pressures act on different phenotypes within a population, causing individuals with certain phenotypes to diverge from others and form a new species 

Note:

Howea palms 

• Location: Lord Howe Island, a small island off eastern Australia. 

• Species involved: Howea belmoreana and Howea forsteriana. 

 

• Possible cause of speciation: Different soil pH acted as a selection pressure. 

• H. belmoreana grows in neutral and acidic soils. 

• H. forsteriana grows in alkaline (calcarenite) soils. 

 

• Researchers think that a population of palms colonised the alkaline soil and gradually adapted to it. 

• As adaptations accumulated, physiological differences developed between the populations. 

• One important difference was flowering time. 

• The two groups flowered at different times - The H. forsteriana flowered roughly SIX weeks before H. belmoreana. 

• This reduced interbreeding and acted as a reproductive isolation mechanism. 

• Over many generations, the differences became so great that they could no longer interbreed to produce viable, fertile offspring. 

• Because Lord Howe Island is small, the palms were unlikely to have been geographically isolated, supporting the idea of sympatric speciation 

• Selective breeding/artificial selection

• What are humans in this process?

• What are the requirements for selective breeding

Selective breeding/artificial selection process of changing a population’s gene pool due to humans altering the breeding behaviour of animals and plants to develop a selected trait 

• Humans act as selective agents 

Compare selective breeding and natural selection

What are some examples of selective breeding?

Examples include: sheep that produce high quality wool; chickens that lay large eggs; domestic dogs that are good at herding; horses that are strong for pulling ploughs; cows that produce lots of milk 

Note:

While the primary method of selective breeding is to simply select for and breed individuals with a desirable trait together, it is also possible to select against an unwanted trait to remove it from the population 

Antimicrobial agent + give examples

Antimicrobial agent an agent that kills or slows the growth of microorganisms 

• E.g. antiseptics, disinfectants, antifungals, antivirals and antibacterial agents  

Antimicrobial resistance + is it an example of natural selection?

Antimicrobial resistance  the ability of a microorganism to survive exposure to an antimicrobial agent, causing existing antimicrobials to be no longer effective 

• This is an example of natural selection 

• Note that antibiotics do not cause bacteria to evolve resistance - rather, resistance to certain antibiotics already exists within the population 

Explain the process of antibiotic resistance:

Outline some mechanisms of antibiotic resistance

What are some factors which contribute to the formation of antibiotic-resistant bacteria?

• Inappropriate compliance with a treatment plan  

--> where a course of antibiotics is prematurely stopped (e.g. when a patient feels better and believes that continued use of their prescribed antibiotics is no longer required) 

• An incomplete course may not sufficiently eliminate all the pathogenic bacteria present -  which allows them to continue replicating within the body and provides them with a greater time to accumulate mutations which may confer antibiotic resistance 

 

• Inappropriate use of antibiotics, where antibiotics are prescribed when they are not required 

  • e.g. the prescription of antibiotics for treating viral infections (e.g. the common cold or the flu) can expose the normal flora inhabiting the body to antibiotics, which can select for antibiotic resistance (encourage growth of antibiotic-resistant bacteria) 

 

• Widespread use of antibiotics  

--> where the general increased use of antibiotics can increase the probability that an individual prescribed antibiotics will be inhabited by antibiotic-resistant bacteria – so when antibiotics are prescribed, these resistant bacteria have a survival advantage over susceptible bacteria and are therefore more likely to survive and reproduce 

Note:

Doctors often use a combination of various different antibiotics with differing mechanisms of action, increasing the chances of destroying the bacteria 

• This ensures that even if some of the bacteria were resistant against one of the antibiotics, the other would be able to destroy them 

The surface antigens of viruses frequently undergo changes in an effort to avoid detection by immunological memory cells developed from past infection or vaccination  

--> In doing so, any medications targeting specific surface antigens on the virus are also rendered ineffective 

• Explain what antigenic drift is

• Draw a diagram to show it

Antigenic drift 

Which involves small and gradual changes in the genes encoding for viral surface antigens  

• Where initially previous memory cells generated will be capable of recognising these mutated surface antigens 

• However as the mutations continue to accumulate, a new subtype of virus can form, which will no longer be recognised by memory cells 

Antigenic shift + draw diagram

Involves sudden and significant changes in the genes encoding for viral surface antigens 

• This commonly occurs when two or more different strains (specific variants) of a virus combine when coinfecting the same host to form a completely new subtype through a process known as viral recombination 

Note:

• the emergence of prokaryotes (3.8 bya) 

• widespread photosynthesis (2.4 bya) 

• the first eukaryotes (2 bya) 

• the first multicellular organisms (900 mya) 

• the Cambrian explosion (535 mya) 

• animals on land (530–400 mya) 

• mammals (251 mya) 

• flowering plants (140 mya) 

 

1. All living things on Earth evolved from a single-celled prokaryote that existed around 3.8 bya 

2. This prokaryote had generations of offspring, some of which evolved the ability to photosynthesise --> In turn, the ability to photosynthesise oxygenated the atmosphere, which allowed for organisms that respire aerobically (such as simple eukaryotes) to survive 

3. From here, multicellularity arose and the Cambrian explosion occurred, marking a massive rise in the diversity of living things -->  it is during this period that almost all of the major animal groups began appearing, including those with hard shells and skeletons 

Palaeontology

Palaeontology: “Study of ancient life represented by fossils” 

• Fossils

• Mould fossil

• Cast fossil

Fossils: the preserved remains/body, impressions or traces (RIT) of a dead organism 

 

• Mould fossil formed when a living thing decomposes underneath sediment, creating a cavity in the shape of the dead organism  

• Cast fossil formed when a mould fossil is filled with sediment  

• Fossilisation

• Fossil record

• Is fossilisation common?

Fossilisation: the preservation of hardened remains/traces of organisms  

 

Fossil record the collection of all fossils and the information they provide about the history of life on Earth 

• The fossil record is arranged in chronological order and helps us map the history of life on Earth, placing species in the appropriate geologic time frame 

 

No. Usually, when an animal dies, it is either consumed or its body decomposes completely, leaving no evidence that it ever really existed --> but sometimes, given the right set of conditions, the remains of the body can be preserved and form a fossil 

Soft bodied organisms are unlikely to be preserved. Why is this?

• Soft-body parts decay readily  

• Subject to predation/scavenging 

Describe process of fossilisation:

1. Remnants of an organism are rapidly buried by sediment (naturally-occurring solid material such as rock, silt, mud) --> meaning that the dead organism is not exposed to oxygen, microorganisms and other disturbances that would increase its rate of decomposition 

• Lack of oxygen for decomposer microorganisms 

• Hides the organism from scavengers - keeps them intact, undisturbed 

• protected from erosion by wind/rain 

 

2. Over time, sediment layers build upon each other and compact, layer by layer, until pressure cements them together to form sedimentary rock  

3. Within this rock, the fossilised remains can take many forms, including a permineralised, mould, or cast fossil

• Trace fossils + give examples

• Give examples of fossils that still contain soft tissue yet to decompose

Trace fossils, which are indirect evidence of an organism’s existence, rather than the organisms themselves (e.g. their footprints, nests, burrows) 

 

There are examples of fossils that still contain soft tissue yet to decompose (e.g. human mummies, mammoths frozen in ice, and insects stuck in amber) 

The conditions that increase the likelihood of fossilisation include + explain why:

• Rapid burial by sediment that quickly covers dead remains to [provide physical protection to ensure scavengers do not interfere (or decomposers) (e.g. fungi, bacteria)  

• Low oxygen levels thus it is not a suitable environment for decomposers, leading to a low decomposition rate.  

• Lack of scavengers 

• Lots of pressure from layers of sediment (hardening the fossil, less likely to decompose) 

• Alkaline soil as acidity damages tissues. 

• Dry climate promotes water leaving remains and reduces decay. 

• Extreme cold climates lead to low decomposition rate.  

• Hardened remains do not readily decompose 

• Low light exposure 

 

(Note that fossilisation is more likely to occur in aquatic systems – due to less oxygen, lower temp and more sediment accumulation) 

• Relative dating

• The law of fossil/faunal succession

• Geographical time scale 

Relative dating a dating technique used to determine the relative age of a fossil by comparing its position to other fossils or rock in surrounding rock strata (layers) 

 

The law of fossil/faunal succession states that because sedimentary rock is formed by the accumulation of sedimentary layers on top of each other, the fossils closer to the surface must be younger than those that are found below them 

We can be able to determine the age of the rock stratum (layer of sedimentary rock) in which the fossil is found 

--> Where the aging of rock strata is called a geological time scale 

Index fossils

• What are they used for?

• What are they’re qualities?

• Researchers can also use particular fossils known as index fossils to help them determine the relative age of a new fossil --> They are useful because they enable researchers to quickly and easily define the relative age of a target fossil 

--> these are a group of widespread, highly abundant fossils which existed for a short period and have a precisely known age 

For the best index fossils, the species must be: 

• physically distinctive 

• have had a large population 

• have existed in many geographical areas 

• only lived within a known short period of time 

Transitional fossils 

• Are fossils that shows traits that are common to both its ancestral group and its descendant group 

--> they are particularly important/useful when the descendant species is physically very distinct from the ancestral species 

• Help relate an ancestral group with its descendants (contains shared characteristics) 

 

e.g. 

• Assume you have a known species – Species X – and another species – Species Z – and you hypothesise that the two species are related --> However the two species look very different  

--> In this case, a transitional fossil – Species Y – is needed, as it can show the link between both of the species due to the fact that it shares similarities to both and shows how certain features might have evolved progressively over time 

• Absolute dating/radiometric dating

• Radioisotopes

• Half-life

Absolute dating/radiometric dating a dating technique used to determine the absolute age (age in years) of a fossil by measuring the relative amounts of radioisotopes to their products/stable forms 

Radioisotopes are unstable elements that will break down over time into a more stable product (e.g. carbon-14 (a radioisotope) will break down into nitrogen-14) 

--> While these radioisotopes can break down at any point, on average the rate of breakdown is constant  

--> one of the ways in which we model this breakdown is by calculating the half-life of that radioisotope (which is the time taken for half the mass of a radioisotope sample to break down into its predictable and stable products) 

Dating period

The range of time since fossilisation in which a particular radioisotope series can be used - beyond this period, most of the radioisotope will have broken down into its products, where it would be too difficult to estimate the fossil’s age

Radiocarbon dating/carbon dating/radioactive carbon dating

Radiocarbon dating/carbon dating/radioactive carbon dating: a form of absolute dating used to determine the age of a fossil by measuring the proportion (%) of C-14 to C-12 in a sample 

• So it uses the radioisotope series carbon-14 (¹⁴C) to nitrogen-14 (¹⁴N) 

What is radioactive carbon’s half-life? How many half-lives does it usually have?

Note that radioactive carbon half-life is 5730 years --> it has around 10 half-lives and thus could only be used for modern species and objects less than 57300 years old 

Explain the process of radiocarbon dating:

1. All living things contain carbon --> this carbon exists as a ratio of two isotopes – ¹²C (a stable isotope) and ¹⁴C (a radioactive isotope) 

   •  The ratio of these two isotopes will be the same as the ratio in the atmosphere, given that carbon is constantly being cycled between the organism and its environment while it is alive 

    

2. When the organism dies, its ¹⁴C will begin to decay where it breaks down into ¹⁴N (a stable isotope)  

--> While this decay occurs, the carbon in the dead organism will not be replaced by existing carbon in the atmosphere - as such, levels of ¹²C (a stable isotope) will remain the same, while 14C decays at a known rate – causing the ratio between the two isotopes to change 

 

3. Scientists can measure the amount of ¹⁴C present in the fossil and determine how long ago it died --> This is done by comparing the 14C : 12C ratio in the fossil to the ratio of 14C : 12C in the atmosphere 

   • The longer ago the organism died, the less 14C will be present (having broken down into 14N) 

Limitations of Radiocarbon Dating 

• Carbon-14 isotope has a relatively short half-life and can only be used to date fossils less than 57000 years old (<10 half lives).  

• There may be too little Carbon-14 isotope left in the fossil to accurately date.  

Structural morphology

Structural morphology the study of physical structures (e.g. skeletal structures) to establish relatedness  

• Homologous structures

• What type of evolution are they physical evidence of? Explain this evolution type

Homologous structures are features found in different species that may look and function very differently in different species but are derived from a common ancestor 

e.g. 

The upper limb of humans, cats, whales, and bats  

• They have different shapes and functions – humans carry things with their arms, cats walk with their legs, whales swim with their flippers, and bats fly with their wings  

• Yet they all share a similar bone structure --> suggests that they diverged from a common ancestor which had this limb structure 

 

Homologous structures are physical evidence of divergent evolution, which is the process in which a common ancestor evolves into two or more descendant species 

• This process typically occurs as a result of individual populations adapting to different selection pressures or genetic drift which alters population genomes over extended periods of time 

• Analogous structures

• What type of evolution are they physical evidence of? Explain this evolution type

Analogous structures are structures present in multiple species that serve similar biological functions but are not derived from a common ancestor 

 

Analogous structures are evidence of convergent evolution, which is the process in distantly related or unrelated species (without a recent common ancestor) independently evolve similar traits to adapt to similar environments and selection pressures over time 

 

e.g. 

• The wings of birds and insects are analogous structures because they are used to fly 

• They are very different structures, however, as birds and insects evolved independently from one another 

Vestigial structures

Vestigial structures are structures found within organisms that once served a purpose for an organism’s ancestors but, as a result of evolution by natural selection, have lost their original function and are no longer required for survival 

• Despite having no function, these structures often remain in a species as they are not selected against 

 

e.g. 

The human coccyx (also known as the tailbone) does not serve a significant function in modern humans 

• It is a vestigial structure which was used to balance our ancestors' bodies when they lived in trees 

• Over time, more advanced features such as the cerebellum and inner ear evolved in humans to help with balance, meaning that the tail was no longer necessary for survival 

 

e.g. 

• Snakes and whales have pelvic bones despite them not having legs --> this is because snakes are descendants of reptiles that had legs, while whales are descendants of earlier mammals that had legs 

• Molecular homology

• Which genes do we analyse proteins from? Explain them.

Molecular homology the study of the similarities in the nucleotide sequences of DNA or amino acid sequences in proteins between organisms to establish relatedness 

• When studying amino acid sequence similarities, we analyse proteins from conserved genes – which are genes that have remained largely unchanged throughout evolution, and are found across the genome’s of many different species 

Haemoglobin (Hb)

A protein found in red blood cells that is responsible for the transport of oxygen in the body  

•  It is composed of up to 4 polypeptide chains: 2 alpha chains consisting of 41 amino acids and 2 beta chains consisting of 146 amino acids 

--> Researchers can assess the number of amino acid differences between the chains of different organisms to observe their degree of relatedness 

Using this, explain:

• Outline which species is closest/most related to humans in their amino acid sequence for haemoglobin (go from descending order)

• Where compared to humans, chimpanzees have the highest level of similarity in their amino acid sequence for haemoglobin (no difference), followed by gorillas, and finally kangaroos 

--> This suggests that chimpanzees are the most closely related to humans (and, by extension, share the most recent common ancestor) and kangaroos are the most distantly related 

Cytochrome c  

An enzyme present in mitochondria that consists of 104 amino acids which are encoded by a conserved gene in mitochondrial DNA (mtDNA) 

Using this, explain:

• Outline which species is closest/most related to humans in their amino acid sequence of cytochrome c (go from descending order up to 5th most related don’t do all)

Top 5 species

Using this, explain:

• Outline which species is closest/most related to humans in their DNA sequence (go from descending order)

• Humans and rats have three nucleotide differences, whereas humans and yeast have seven nucleotide differences 

--> Indicating that rats are more closely related to humans than yeast 

• What is a limitation of analysing amino acid sequences?

• What are their benefits?

• A limitation to analysing amino acid sequences is that closely related species are likely to share very similar amino acid sequences for certain proteins 

 --> In these instances, scientists determine relatedness by comparing nucleotide sequences, looking for silent mutations that, due to the redundancy (where multiple codons code for an amino acid) of the genetic code, may have accumulated without altering the amino acid sequence 

 

• Amino acid sequences, however, are easier to interpret and are therefore used to determine relatedness in more distantly related species 

Phylogenetics 

the study of the relatedness between organisms 

Note:

Information regarding the relatedness of different species can be represented in a phylogenetic tree, which is a diagram used to illustrate evolutionary relationships between species 

They can be useful in displaying: 

• the timeline of lineages - descendants 

• relatedness between taxa  

• shared characteristics of different taxa 

 

Taxa (singular: taxon) means a group of organisms classified together 

For example, scientists classify living things into different groups: 

• Kingdom → Animalia  

• Phylum → Chordata  

• Class → Mammalia  

• Order → Primates  

• Family → Hominidae  

• Genus → Homo  

• Species → Homo sapiens  

Each of these groups is a taxon, and together they are called taxa 

There are many different components of a phylogenetic tree + label them on the tree

Note: