Unit 4 AOS2 - Species Relatedness - OCR PDF

Unit 4 AOS2 How are species related over time? Chapter 9- How species evolve  causes of changing allele frequencies in a population’s gene pool, including environmental selection pressures, genetic...

Unit 4 AOS2 How are species related over time? Chapter 9- How species evolve  causes of changing allele frequencies in a population’s gene pool, including environmental selection pressures, genetic drift and gene flow; and mutations as the Key knowledge source of new alleles biological consequences of changing allele frequencies in terms of increased and decreased genetic diversity manipulation of gene pools through selective breeding programs consequences of bacterial resistance and viral antigenic drift and shift in terms Genetic changes in a of ongoing challenges for treatment strategies and vaccination against population over time pathogens evidence of speciation as a consequence of isolation and genetic divergence, including Galapagos finches as an example of allopatric speciation and Howea palms on Lord Howe Island as an example of sympatric speciation  causes of changing allele frequencies in a population’s gene pool, including environmental The gene pool selection pressures, genetic drift and gene flow, and mutations as the source of new alleles The gene pool refers to the complete set of alleles present within a 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. Calculating frequency of alleles You may be asked to calculate the allele frequency in a gene pool. They are usually shown as a decimal ie. 0.90 and 0.10. They must add up to 1. In a population of 500 butterflies, the following genotypes are observed: 200 butterflies have the genotype BB, 150 butterflies have the genotype Bb, 150 butterflies have the genotype bb. Calculate the allele frequencies for the B and b alleles.  causes of changing allele frequencies in a population’s gene pool, including environmental Mutations selection pressures, genetic drift and gene flow, and mutations as the source of new alleles Mutations are responsible for introducing new alleles into a population via changes to DNA. These changes can involve substitution, addition or deletion of a single nucleotide of larger blocks of DNA. Mutations can occur spontaneously or can be induced by agents called mutagens, eg. UV radiation.  causes of changing allele frequencies in a population’s gene pool, including environmental Mutations selection pressures, genetic drift and gene flow, and mutations as the source of new alleles A mutation in the DNA can affect the expression of a gene by changing the characteristics of the resulting protein. Mutations can be advantageous, neutral or deleterious (disadvantageous).  causes of changing allele frequencies in a population’s gene pool, including environmental Inheriting mutations selection pressures, genetic drift and gene flow, and mutations as the source of new alleles For a mutation to be heritable, it must occur in an individual’s germline cells. If the mutation occurs in a somatic cell, then it is not heritable.  causes of changing allele frequencies in a population’s gene pool, including environmental Point and block mutations selection pressures, genetic drift and gene flow, and mutations as the source of new alleles Mutations are either point or block mutations, depending on if they affect a single nucleotide in a gene or a larger cluster of nucleotides.  causes of changing allele frequencies in a Types of point mutations population’s gene pool, including environmental selection pressures, genetic drift and gene flow, and mutations as the source of new alleles Base substitution mutations One nucleotide is replaced by another type of nucleotide. Silent mutation – nucleotide changes, however DNA triplet codes for the same amino acid. Missense mutation – nucleotide changes, different amino acid in the polypeptide changes. Nonsense mutation – Nucleotide changes, codes for an early STOP codon. Polypeptide will be shortened Frameshift mutations nucleotide is added or removed, altering every codon in that sequence from that point onwards. This results in a non-functional protein.  causes of changing allele frequencies in a population’s gene pool, including environmental Types of block mutations selection pressures, genetic drift and gene flow, and mutations as the source of new alleles Block mutations involve changes to larger sections of DNA. Duplication- part of a chromosome is copied, often increases gene expression. Deletion- removes sections of a chromosome, leads to disrupted or missing genes Inversion- a section of the chromosome rotates 180° Translocation- part of a chromosome breaks and moves to attach to another chromosome.  causes of changing allele frequencies in a population’s gene pool, including environmental Aneuploidy and polyploidy selection pressures, genetic drift and gene flow, and mutations as the source of new alleles Aneuploidy- Missing Polyploidy- extra whole sets chromosome (monosomy) or of chromosomes (ie. extra chromosomes (trisomy). strawberries have 8 sets of chromosomes 8N instead of 2N).  causes of changing allele frequencies in a population’s gene pool, including environmental selection pressures, genetic drift and gene flow, and mutations as the source of new alleles Environmental selection pressures biological consequences of changing allele frequencies in terms of increased and decreased genetic diversity Environmental selection pressures is a factor in an organism’s environment that removes unsuited individuals. It consequently determines the alleles to be passed on to the next generation. As advantageous traits become more common in a population, the frequency of the advantageous allele increases. This can eventually lead to genetic diversity decreasing. → eg. predation, disease, competition, and climate change, food availability.  causes of changing allele frequencies in a population’s gene pool, including environmental selection pressures, genetic drift and gene flow, and mutations as the source of new alleles Environmental selection pressures biological consequences of changing allele frequencies in terms of increased and decreased genetic diversity Populations with low genetic diversity are often at risk of extinction due to their inability to have favourable alleles when environmental selection pressures change. Inbreeding is also more common in populations with low genetic diversity, which can lead to a high prevalence of disadvantageous alleles.  causes of changing allele frequencies in a population’s gene pool, including environmental selection pressures, genetic drift and gene flow, and mutations as the source of new alleles Natural Selection biological consequences of changing allele frequencies in terms of increased and decreased genetic diversity Process variation already exists in the population Presence of an environmental selection pressure. Individuals with the advantageous phenotype are more likely to survive and produce viable offspring, passing the alleles for the favourable trait onto offspring Over generations the allele frequency and therefore number of individuals in the population with favourable trait increases. Natural selection and the peppered moth  manipulation of gene pools through selective breeding programs Selective breeding biological consequences of changing allele frequencies in terms of increased and decreased genetic diversity Selective breeding (or artificial selection) is the process by which humans choose individual organisms with desirable traits and deliberately interbreed them to increase the allele frequency of those desired traits in the gene pool. Selective breeding decreases genetic diversity Process Determine the desired trait. Interbreed parents who show the desired trait. Select the offspring with the best form of the trait and interbreed these offspring. Continue this process until the population reliably reproduces the desired trait and the frequency of the alleles for the desire trait increase.  manipulation of gene pools through selective breeding programs The effect on genetic diversity biological consequences of changing allele frequencies in terms of increased and decreased genetic diversity By restricting breeding to these individuals, the generational increase in the frequency of the selected allele will decrease genetic diversity as the phenotypes of the population are driven towards a specific allele. Reduced genetic diversity can lead to increased inbreeding, which can increase the prevalence of deleterious alleles, and a lower adaptive potential.  manipulation of gene pools through selective breeding programs Selective breeding example biological consequences of changing allele frequencies in terms of increased and decreased genetic diversity  causes of changing allele frequencies in a population’s gene pool, including environmental selection pressures, genetic drift and gene flow, and mutations as the source of new alleles Genetic drift biological consequences of changing allele frequencies in terms of increased and decreased genetic diversity Genetic drift is a random change in allele frequency by chance. It causes a decrease in genetic diversity as individuals will not have all the variations of alleles as seen in the original population, the descendants of remaining individuals will not be able to inherit other alleles and there will be less variation. The effect is more pronounced in smaller populations. It may cause alleles of a particular gene to completely disappear or may cause an allele to become more common purely by chance. The lack of genetic diversity can lead to extinction. Genetic drift either occurs through either the bottleneck effect or the founder effect.  causes of changing allele frequencies in a population’s gene pool, including environmental selection pressures, genetic drift and gene flow, and mutations as the source of new alleles The bottleneck effect biological consequences of changing allele frequencies in terms of increased and decreased genetic diversity The bottleneck effect occurs when a large portion of a population is wiped out by a chance event such as a natural disaster. These events severely reduce the population size, significantly changing allele frequencies by chance, decreasing genetic diversity in the new population.  causes of changing allele frequencies in a population’s gene pool, including environmental selection pressures, genetic drift and gene flow, and mutations as the source of new alleles The founder effect biological consequences of changing allele frequencies in terms of increased and decreased genetic diversity The founder effect occurs when a small unrepresentative sample of individuals separates from a larger population to colonise a new region and start a new population. The founding population has an unrepresentative sample of the original population’s alleles. Founder effect decreases genetic diversity.  causes of changing allele frequencies in a population’s gene pool, including environmental selection pressures, genetic drift and gene flow, and mutations as the source of new alleles Consequences for genetic diversity biological consequences of changing allele frequencies in terms of increased and decreased genetic diversity  causes of changing allele frequencies in a population’s gene pool, including environmental selection pressures, genetic drift and gene flow, and mutations as the source of new alleles Gene flow biological consequences of changing allele frequencies in terms of increased and decreased genetic diversity Gene flow is the movement of alleles through genetic exchange between individuals of different populations. It occurs through interbreeding. It introduces new alleles into the gene pool of a population. Gene flow results in an increase in genetic diversity.  causes of changing allele frequencies in a population’s gene pool, including environmental selection pressures, genetic drift and gene flow, and mutations as the source of new alleles Gene flow biological consequences of changing allele frequencies in terms of increased and decreased genetic diversity Extinction Extinction is when no members of a particular species exist. Decreasing genetic variations can threaten the survival of a species. There may be a change in a selection pressure and if no variation exists all individuals within the population will respond to the change in the same way. This means that many of the individuals within the population may die. Increasing the genetic/diversity variation within a species, the more likely it is able to survive a change in the selection pressures. Gene flow can increase genetic diversity. Species with limited genetic diversity that continue to thrive are either well adapted to environment, or there have been no change in selection pressures.  evidence of speciation as a consequence of isolation and genetic divergence, including Galápagos finches as Speciation an example of allopatric speciation and Howea palms on Lord Howe Island as an example of sympatric speciation Individuals are recognised as different species if they can no longer interbreed with one another to produce viable and fertile offspring. If there are DNA differences large enough to classify them as different species There are two types of speciation Allopatric Sympatric  evidence of speciation as a consequence of isolation and genetic divergence, including Galápagos finches as Allopatric speciation process an example of allopatric speciation and Howea palms on Lord Howe Island as an example of sympatric speciation Allopatric speciation involves the formation of a new species as a result of a geographical barrier ie. presence of a mountain range or the development of a river. 1. Geographical separation due to physical barrier 2. No gene flow 3. Different selection pressures exist 4. Some individuals at a selective advantage for particular traits. 5. Individuals reproduce and passes on alleles. 6. Different mutations accumulate in each population. 7. Eventually enough differences exist that when brought back together they can no longer produce viable or fertile offspring. Galapagos finches Geographical separation across the various islands No gene flow Selection pressure of different food sources on each of the islands. Selective advantage for particular beak shape/sizes. These finches reproduce and passes on alleles. Different mutations accumulate in each population. Eventually enough differences exist that when brought back together they can no longer produce viable or fertile offspring.  evidence of speciation as a consequence of isolation and genetic divergence, including Galápagos finches as Galapagos finches an example of allopatric speciation and Howea palms on Lord Howe Island as an example of sympatric speciation  evidence of speciation as a consequence of isolation and genetic divergence, including Galápagos finches as Sympatric speciation an example of allopatric speciation and Howea palms on Lord Howe Island as an example of sympatric speciation Formation of a new species in populations located in the same geographical location (or without geographical isolation). It is often due to reproductive isolation. Different selection pressures act on different phenotypes within a population, causing individuals with certain phenotypes to diverge from others and form a new species. The different phenotypes, creating a reproductive barrier, make it difficult for the individuals to reproduce Examples of reproductive isolation. Time of day or year for breeding Mating behaviours varying Different physical characteristics of reproductive organs (genitalia) prevent mating. Different populations within a species exploit different ecological opportunities, such as food resources or habitats Polyploidy individuals cannot interbreed with their diploid counterparts. Sympatric speciation process 1. Within the same geographical area, different subgroups of the population experience different selective pressures. 2. Different traits in the subgroups are at a selective advantage and only individuals with the advantageous trait survive. 3. Over time genetic differences accumulate between the subgroups. 4. The accumulated differences eventually lead to reproductive isolation mechanisms. 5. the subgroups no longer interbreed successfully or produce viable, fertile offspring. Howea palms On Lord Howe Island, two palm species are of particular interest and demonstrate sympatric speciation: Howea forsteriana and Howea belmoreana 1. These species exist on the same island, without any significant geographical barriers separating them. 2. differing soil pH levels on Lord Howe Island acted as a selection pressure. 3. Advantageous traits allowed Howea forsteriana to adapt to the alkaline (high pH) soil conditions, while Howea belmoreana adapted to the neutral and more acidic soils (low pH). 4. Over time, they accumulated genetic differences. 5. These differences included changes in flowering times, causing reproductive isolation. 6. Eventually, the two palm species could no longer interbreed to produce viable, fertile offspring.  consequences of bacterial resistance and viral Evolving pathogens- bacteria antigenic drift and shift in terms of ongoing challenges for treatment strategies and vaccination against pathogens Formation of antibiotic-resistant bacteria can be attributed to the process of natural selection → the antibiotics serve as an environmental selection pressure Bacteria can also exchange genetic material with each other through a process known as bacterial conjugation.  consequences of bacterial resistance and viral Evolving pathogens- bacteria antigenic drift and shift in terms of ongoing challenges for treatment strategies and vaccination against pathogens Variation and the emergence of new alleles leading to resistance against antibiotics is facilitated largely by mutations. Through mutations, new alleles can help bacteria develop mechanisms which increase their ability to combat the action of antibiotics.  consequences of bacterial resistance and viral Evolving pathogens- viruses antigenic drift and shift in terms of ongoing challenges for treatment strategies and vaccination against pathogens Viruses are constantly adapting and changing, allowing them to increase their virulence and resistance against the immune system and existing medications. The surface antigens of viruses frequently undergo changes in an effort to avoid detection by immunological memory cells developed from past infection or vaccination on subsequent exposure. In doing so, any medications targeting specific surface antigens on the virus are also rendered ineffective. Therefore, it is extremely difficult to develop effective, long-term vaccinations and medications against viruses.  consequences of bacterial resistance and viral Antigenic drift antigenic drift and shift in terms of ongoing challenges for treatment strategies and vaccination against pathogens Antigenic drift and antigenic shift contribute to the modification of viral surface antigens. Antigenic drift: small and gradual changes in the genes encoding for viral surface antigens. As the mutations continue to accumulate, a new subtype of virus can form, which will no longer be recognised by previously generated memory cells.  consequences of bacterial resistance and viral Antigenic shift antigenic drift and shift in terms of ongoing challenges for treatment strategies and vaccination against pathogens Antigenic shift: sudden and significant changes in the genes encoding for viral surface antigens. This commonly occurs when two or more different strains of a virus combine when coinfecting the same host to form a completely new subtype through a process known as viral recombination. Natural immunity to this new virus subtype is likely to be uncommon, making it extremely infectious, with the potential to develop into an epidemic or pandemic.  consequences of bacterial resistance and viral Challenges for treatment strategies antigenic drift and shift in terms of ongoing challenges for treatment strategies and vaccination against pathogens Ongoing challenges for treatment strategies to bacterial resistance and viral antigenic drift and shift Current antibiotics/antivirals used for treatment become ineffective More people become infected so more pressure on healthcare. Requires research/development of a new drug and this requires money/investment Develop a vaccine and establish herd immunity Patients resisting isolation are spreading the pathogen. Education required of people or communities around the spread of bacterial pathogen. Chapter 10- How species evolve Key knowledge changes in species over geological time as evidenced from the fossil record: faunal (fossil) succession, index and transitional fossils, relative and absolute dating of fossils evidence of relatedness between species: structural morphology – homologous and vestigial structures; and molecular homology – DNA and amino acid sequences the use and interpretation of phylogenetic trees as evidence for the relatedness between species  changes in species over geological time as The fossil record evidenced from the fossil record: faunal (fossil) succession, index and transitional fossils, relative and absolute dating of fossils Life on Earth has changed a lot over the last 4 billion years. Beginning with the emergence of prokaryotes around 3.8 billion years ago (bya) – evolving into eukaryotes 2 bya – to multicellular life around 1 bya – before finally reaching our genus, Homo, two million years ago (mya).  changes in species over geological time as Change over time evidenced from the fossil record: faunal (fossil) succession, index and transitional fossils, relative and absolute dating of fossils All living things on Earth evolved from a single-celled prokaryote that existed around 3.8 bya. Some prokaryotic offspring evolved the ability to photosynthesise This oxygenated the atmosphere and allowed for organisms that respire aerobically (such as simple eukaryotes) to survive. 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. This widespread explosion of complex species across the Earth’s surface is where the fossil record comes from, and we are still uncovering more evidence to this day.  changes in species over geological time as Fossils evidenced from the fossil record: faunal (fossil) succession, index and transitional fossils, relative and absolute dating of fossils Fossils are the preserved remains, impressions or traces of organisms found in rocks of different ages. Given the right set of conditions, the remains of an organism can be preserved and form a fossil. These fossils, form the fossil record. Other types of fossils include trace fossils which are indirect evidence of an organism’s existence, such as their footprints or nests and soft tissue yet to decompose (mummified organisms stuck in ice or amber)  changes in species over geological time as Process of fossilisation evidenced from the fossil record: faunal (fossil) succession, index and transitional fossils, relative and absolute dating of fossils 1. Body is not eaten by scavengers 2. Body is rapidly covered in sediment/frozen and does not decay 3. There is a lack of oxygen 4. Uplift, erosion or melting of glaciers expose the remains.  changes in species over geological time as Increasing the chance of fossilisation evidenced from the fossil record: faunal (fossil) succession, index and transitional fossils, relative and absolute dating of fossils No matter the fossil type, the conditions that increase the likelihood of fossilisation include: - rapidly covered by sediment. - hidden from scavengers - decreased rate of decomposition - hard tough exoskeleton - protection from weather (wind/sunlight water) - constant humidity - constant temperature – usually cold temperature.  changes in species over geological time as Dating fossils evidenced from the fossil record: faunal (fossil) succession, index and transitional fossils, relative and absolute dating of fossils The fossil record is used to date fossils. By determining the age of fossils, researchers are able to compare fossils across time and put together a picture of evolution that maps changes to species. Relative dating and absolute dating are two methods for dating fossils.  changes in species over geological time as Relative dating evidenced from the fossil record: faunal (fossil) succession, index and transitional fossils, relative and absolute dating of fossils Stratigraphy is used to determine relative age. Stratigraphy is the study of the relative positions of the rock strata or layers- lower strata are older and upper strata are younger. The law of faunal (fossil) succession states fossils closer to the surface must be younger than those that are found below them. It also states once a fossil species goes extinct, it disappears and cannot reappear in younger rocks  changes in species over geological time as Index fossils evidenced from the fossil record: faunal (fossil) succession, index and transitional fossils, relative and absolute dating of fossils This means that we can assign fossils a relative age – an approximate age based on the position of the fossil compared to other fossils. Also, If a fossil is found in the same sedimentary layer an index fossil (fossil of a known age) then it can be assumed they are the same age. They are useful because they enable researchers to quickly and easily define the relative age of a target fossil.  changes in species over geological time as Index fossils evidenced from the fossil record: faunal (fossil) succession, index and transitional fossils, relative and absolute dating of fossils Index fossils come from an organism - physically distinctive - have had a large population - have existed in many geographical areas (widespread) - only lived within a known short period and precisely known period of time  changes in species over geological time as Transitional fossils evidenced from the fossil record: faunal (fossil) succession, index and transitional fossils, relative and absolute dating of fossils Researchers can also use transitional fossils to assist with relative dating. Essentially, these are fossils that can be thought of as ‘intermediaries’ between an ancestral species and a descendant species and are especially useful when these two species are morphologically very distinct. They exhibit traits that are common to both an ancestor and its descendants. Transitional fossils A classic example of a transitional fossil is Archaeopteryx, which exhibits features both ancestral to dinosaurs and descendants leading towards modern birds. Key features include : Ancestral Features (Similar to Dinosaurs): Teeth in its beak. Claws on its wings. Long bony tail. Derived Features (Similar to Birds): Feathers for flight Lightweight bones suited for flight. A wishbone (furcula), a key feature in modern birds. Absolute dating - radioactive isotopes Absolute dating techniques can be used to calculate the absolute age of a fossil in years. Absolute dating uses radioisotopes with a known half-life Radio carbon dating is used to date fossils less than 50,000 years old. changes in species over geological time as evidenced from the fossil record: faunal (fossil) succession, index and transitional fossils, relative and absolute dating of fossils Radiocarbon dating 1. Radioisotopes are unstable elements that will break down over time into a more stable product. For instance, carbon-14 (a radioisotope) will break down into nitrogen-14. 2. While these radioisotopes can break down at any point, on average the rate of breakdown is constant and can be modelled. One of the ways in which we model this breakdown is by calculating the half-life of that radioisotope. 3. Half-life describes the amount of time before half of the mass of a radioisotope is broken down into predictable and stable products. For example, carbon-14 is a radioisotope that has a half-life of 5 730 years. This means that after 5 730 years of an organism’s death, half of its carbon-14 atoms will have broken down into nitrogen-14 atoms (Figure 10).  changes in species over geological time as Radiocarbon dating evidenced from the fossil record: faunal (fossil) succession, index and transitional fossils, relative and absolute dating of fossils  changes in species over geological time as Summary evidenced from the fossil record: faunal (fossil) succession, index and transitional fossils, relative and absolute dating of fossils Mass extinctions Throughout the fossil record, there is evidence of some significant mass extinction events. Mass extinctions are large-scale extinctions following disruptive changes to the global climate, or loss of sea or land due to the shifting of continents. Mass extinctions lead to empty ecological niches. Remaining species may have taken advantage of the sudden availability of resources and reduced competition or predation. This is known as adaptive radiation - a process in which organisms diverge rapidly from an ancestral species into a multitude of new species.  evidence of relatedness between species: structural morphology – homologous and Structural morphology vestigial structures; and molecular homology – DNA and amino acid sequences Structural morphology is one method of assessing similarity Comparative structural morphology (anatomy) is the comparison of equivalent structures in different species e.g. Human and chimpanzee (two arms, each with a hand a five digits, two legs, each with a foot and five digits.) Can be homologous structures or analogous structures.  evidence of relatedness between species: structural morphology – homologous and Homologous structures vestigial structures; and molecular homology – DNA and amino acid sequences Features found in different species that have a similar basic structure but different function. Eg. the upper limb of humans, cats, whales, and bats → They have different shapes and functions, but have similar bone structure Homologous structures suggests that each of these species diverged from a common ancestor.  evidence of relatedness between species: structural morphology – homologous and Vestigial structures vestigial structures; and molecular homology – DNA and amino acid sequences Structures found within organisms that once served a purpose for an organism’s ancestors but, due to changing selection pressures, have no apparent function and no longer required for survival. Despite having no function, these structures often remain in a species as they are not selected against. It is further evidence of organisms have diverged from a common ancestor. For example, whales have → Eg. the human coccyx and the pelvic bone in snakes and whales.  evidence of relatedness between species: structural morphology – homologous and Molecular homology vestigial structures; and molecular homology – DNA and amino acid sequences Molecular homology is the study of the similarities between organisms at a DNA and amino acid level. DNA sequencing- the greater the similarities in nucleotide sequences the more closely related the two species are. Amino acid sequencing - the greater the similarities in amino acid sequences the more closely related the two species are. Amino acids accumulate changes more slowly due to the effect of silent mutations.  evidence of relatedness between species: structural morphology – homologous and Amino acid sequencing vestigial structures; and molecular homology – DNA and amino acid sequences Haemoglobin When studying amino acid sequence similarities, proteins from conserved genes which are found in a number of different species are analysed eg. Haemoglobin and cytochrome C 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.  evidence of relatedness between species: structural morphology – homologous and vestigial structures; and molecular homology – Cytochrome C DNA and amino acid sequences In this particular segment, rats show more similarity to humans than yeast does. evidence of relatedness between species: structural morphology – homologous and vestigial structures; and molecular homology – DNA and amino acid sequences  evidence of relatedness between species: structural morphology – homologous and DNA sequence similarity vestigial structures; and molecular homology – DNA and amino acid sequences Just like amino acid sequences, a higher similarity in DNA sequence implies a closer level of relatedness between different organisms. 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.  evidence of relatedness between species: structural morphology – homologous and Whole genome sequencing vestigial structures; and molecular homology – DNA and amino acid sequences Whole genomes can also be sequenced to determine the degree of similarity. The higher the degree of similarity between the genomes of different species, the more related they are and the more recent they diverged from a common ancestor.  evidence of relatedness between species: structural morphology – homologous and DNA vs amino acid sequence vestigial structures; and molecular homology – DNA and amino acid sequences It depends on how related the species are as to which comparison technique to use. A limitation to analysing amino acid sequences is that closely related species are likely to share very similar sequences for certain proteins. → In these instances, scientists determine relatedness by comparing nucleotide sequences, looking for silent mutations that, due to the redundancy 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.  evidence of relatedness between species: structural morphology – homologous and Summary vestigial structures; and molecular homology – DNA and amino acid sequences  the use and interpretation of phylogenetic trees as evidence for the relatedness between species Phylogenetic trees A phylogenetic tree is a diagram that shows the evolutionary relationships between different species. The individuals that are the most related are those that ‘share the most recent common ancestor’. Phylogenetic trees the use and interpretation of phylogenetic trees as evidence for the relatedness between species  the use and interpretation of phylogenetic trees Reading as evidence for the relatedness between species A phylogenetic tree can be read backwards to determine the most recent common ancestor. Constructing the use and interpretation of phylogenetic trees as evidence for the relatedness between species A phylogenetic tree of these animals can be constructed using the following steps ( 1. Identify the trait that is shared by the largest number of animals. → Four legs, except for bony fish → draw the bony fish lineage branching off from the rest of the animals. 2. Identify the trait shared by the second-largest number of animals → Fur → draw the amphibians lineage branching off from the rest of the animals before the ‘fur’ label. 3. Both marsupials and placental mammals have fur → marsupials and placental mammals lineages are branching directly from the trait fur. Constructing the use and interpretation of phylogenetic trees as evidence for the relatedness between species Uncertainties in phylogenetic trees the use and interpretation of phylogenetic trees as evidence for the relatedness between species Lack of a node between species Y and Z → the exact divergence point is unknown. The break between species W and X → W is possibly an ancestor of X but there is no evidence of transitional fossils between the two species to support this hypothesis. The branch with species S does not reach the end of the tree → indicating that it is extinct. Sometimes nodes can split into three or more (T, U, and V) → This means that it’s unclear which species diverged from the others first. Exchanging genetic material the use and interpretation of phylogenetic trees as evidence for the relatedness between species Sometimes genetic material is passed between groups after they have diverged. There is strong evidence to suggest that certain groups of modern humans (Homo sapiens) interbred with Neanderthals (Homo neanderthalensis), causing parts of their genomes to be passed between each other. → This is depicted using a line between branches Chapter 11- Becoming human  the shared characteristics that define mammals, primates, hominoids and hominins evidence for major trends in hominin evolution from the genus Australopithecus to the genus Homo: changes in brain size and limb structure the human fossil record as an example of a classification scheme that is open to Key knowledge differing interpretations that are contested, refined or replaced when challenged by new evidence, including evidence for interbreeding between Homo sapiens and Homo neanderthalensis and Human change over time evidence of new putative Homo species ways of using fossil and DNA evidence (mtDNA and whole genomes) to explain the migration of modern human populations around the world, including the migration of Aboriginal and Torres Strait Islander populations and their connection to Country and Place.  the shared characteristics that define mammals, primates, hominoids, and hominins Defining human Humans belong to four main categories: - Mammals - Primates - Hominoids - Hominins  the shared characteristics that define mammals, primates, hominoids, and hominins Mammals Humans are mammals. Mammals Produce milk to feed young hair or fur on their bodies maintain a constant internal body temperature Mammals have three bones in their middle ear that aid in hearing. four-chambered heart diaphragm, a muscle that separates the thoracic cavity from the abdominal cavity and plays a crucial role in breathing. different types of teeth- incisors, canines, molars.  the shared characteristics that define mammals, primates, hominoids, and hominins Primates Within the class Mammalia, humans are further classified into the Primate order. Primates have hands and feet have five digits Opposable thumbs Forward-facing binocular eyes Large and complex brain Prehensile Hands/Feet Nails Instead of Claws Highly Developed Color Vision digits have touch receptors able to gain information. protective bone at outer side of eye-socket. Fully rotating the arm in the shoulder socket.  the shared characteristics that define mammals, primates, hominoids, and hominins Hominoids Humans are further classified into the superfamily Hominoidea- including great apes and lesser apes. Hominoids have Absence of a tail Longer arms relative to legs Highly flexible shoulder joints Increased cranium size- larger and more complex brains.  the shared characteristics that define mammals, primates, hominoids, and hominins Hominins Humans are in the tribe known as Hominini, are include all human-like species (ie. genus Homo and Australopithecus). This tribe has been evolving and developing over the last 7 million years. Humans are the only living hominins. The key characteristics of the hominins include: The ability to walk erect on two legs (bipedalism) Increased brain size and increased cognitive abilities - allowing for complex language and belief systems, allowing for large, complex societies Reduction in canine teeth size (due to a change in diet) Flexible wrists and opposable thumbs to manipulate objects and use tools. Precision and power grip. Bipedalism Structural features that have allowed for bipedalism include: More central position of the foramen magnum, S- shaped curvature of the spinal column shape of the pelvis is more bowl shaped larger femoral angle allows for bipedalism. Parallel big toe Foot arches and wide heel  evidence for major trends in hominin evolution from the genus Australopithecus to the genus Homo: changes in Changes in brain size brain size and limb structure Hominin brains increased in size over time, evidenced by hominins cranial (skull) capacity estimated from recovered fossilised skulls. Increased folding of the cerebral cortex in hominins expanded brain surface area, boosting neuron connections and cognitive abilities, which facilitated the development of complex cultures and transmission of knowledge ie. Speech, feeling complex emotions, higher-order decision making, enhanced self-control, abstract thinking and planning. Improved diet, including increased fruit and animal products, along with the controlled use of fire, significantly enhanced brain growth. Changes in skull structure evidence for major trends in hominin evolution from the genus Australopithecus to the genus Homo: changes in brain size and limb structure The hominin skull has changed in a number of ways since the early australopithecines: - Larger cranial capacity - A more centralised foramen magnum (1) - A shrinking of the sagittal crest (2) - A lessening of the brow ridge (3) - A flattening and shortening of the face (4) - A less protruding chin (5) - A more domed skull (6) - Smaller teeth- especially canines (7)  evidence for major trends in hominin evolution from the genus Australopithecus to the genus Homo: changes in Changes in limb structure brain size and limb structure In regards to limb structure, major trends in evolution from Australopithecus to the genus Homo, students should focus specifically on trends in changes in arm and leg length changes in the length and curvature of the fingers and toes.  evidence for major trends in hominin evolution from the genus Australopithecus to the genus Homo: changes in brain size and limb structure Arm to leg ratio The arm to leg ratio has decreased in hominins over time- shortening of the arms, lengthening of the legs (long leg to arm ratio) and changes in the pelvis shape were all driven by evolution of bipedalism. As our ancestors moved from trees to the ground, their forelimbs, previously used for locomotion, became free for tasks like carrying children, preparing food, and making tools Longer legs enhance stride length, making Long arms for swinging through the trees upright walking more efficient by reducing the energy required for each step. Fingers and toes The human thumb is longer, the palm and fingers are shorter, and the fingers have lost their curvature. Toes became shorter and less curved over time, the big toe parallel, reflecting a shift from climbing to more efficient bipedal walking  the human fossil record as an example of a classification scheme that is open to differing interpretations that are contested, refined, or replaced The human fossil record when challenged by new evidence, including evidence for interbreeding between Homo sapiens and Homo neanderthalensis and evidence of new putative Homo species The human fossil record is far from a complete depiction of our evolution as a species as it only shows very limited, and often imperfect, fossilised fragments of a small collection of our ancestors. The record could be incomplete for many factors, that include: - Not all individuals die in conditions that promote fossilisation - Not all fossils have been found. Since the fossil record is incomplete, the inferences we are able to make are also incomplete and can be challenged or refined with new evidence. Mitochondrial DNA (MtDNA) mtDNA is inherited from mother only (maternal line), whereas nuclear DNA is inherited from both parents mtDNA has fewer bases compared to nuclear DNA no recombination occurs in mtDNA compared to nuclear DNA mtDNA used for lineage/migration compared to nuclear DNA for parentage/relationship between species mtDNA has a faster mutation rate compared to nuclear DNA. Advantages for using mtDNA include: Advantages for using nuclear faster to sequence DNA include: differences due to more bases and therefore mutation only and not due to recombination information available high copy number (number DNA comes from both of mitochondria) per parents so therefore can cell, so only a small determine if sample is required interbreeding occurred less likely to degrade presence of introns can known or constant rate of reveal more inherited mutation mutations. used for determining lineage. Hominin evolution evidence for major trends in hominin evolution from the genus Australopithecus to the genus Homo: changes in brain size and limb structure African origin of Homo Sapien According to the fossil record, the earliest known hominins first evolved in Africa approximately 4 million years ago (Australopithecines) They remained solely in separate regions of Africa and continued to evolve, resulting in the emergence of new species over time, including the earliest members of the Homo genus. Many of these early hominin species began to migrate out of Africa and into the nearby regions of Europe and Asia. Homo sapiens: 1. evolved in Africa around 200 000 to 300 000 years ago, long after the departure of Homo erectus into Eurasia 2. They remained there for an extended period of time (around 100 000 years) 3. Emigrated in waves and replaced/outcompeted existing hominin species such as Homo erectus and Homo neanderthalensis in different parts of Europe and Asia about 150 000 years ago. This hypothesis means that all modern human beings are of African descent. Fast forward 2 million years and Homo sapiens are the last remaining lineage of the Homo genus Evidence for African Origin some of the oldest Homo sapiens fossils found were uncovered in East Africa and dated to around 160 000 years ago, as well as later fossils uncovered in the Middle East and dated to 100 000 years. mitochondrial DNA (mtDNA) of modern humans demonstrates that mitochondrial lineages can all be traced back to a common ancestor that lived in Africa between 150,000 and 300,000 years ago. Modern-day humans show very little genetic diversity compared to other species, due to our relatively short existence (~200 000 years). The greatest genetic diversity is thought to exist in African populations, where Homo sapiens first appeared- there has been more time for spontaneous mutations to accumulate in mtDNA. artefacts uncovered along deeper parts of Europe (and south-east into Asia), including stone tools, carvings, and cave paintings- indicates increased complexity and cultural evolution. Migration of Homo Sapiens The evidence for humans beginning in Africa and migrating out includes oldest Homo sapien fossils found in Africa. African descendants don’t have any Neanderthal DNA. When Homo sapiens moved out of Africa they first moved towards Europe and had a interbreeding event with Neanderthals. Evidenced by European descents have 1-4% Neanderthal DNA. Some populations then moved into Asia and further. There is thought to have been an interbreeding event with Denisovans. Evidenced by Melanesian populations have Neanderthal and Denisovan (3-5%) DNA.  the human fossil record as an example of a classification scheme that is open to differing Interbreeding with Neanderthals interpretations that are contested, refined, or replaced when challenged by new evidence, including evidence for interbreeding between Homo sapiens and Homo neanderthalensis and evidence of new putative Homo species 1–4% of some human genomes are made up of Neanderthal DNA However, the part of the Neanderthal genome found in each person differs quite a lot. A team of researchers at Princeton University were able to recover around 41% of the total Neanderthal genome from a sample of 2500 individuals.  the human fossil record as an example of a classification scheme that is open to differing Interbreeding with Neanderthals interpretations that are contested, refined, or replaced when challenged by new evidence, including evidence for interbreeding between Homo sapiens and Homo neanderthalensis and evidence of new putative Homo species  the human fossil record as an example of a classification scheme that is open to differing Summary interpretations that are contested, refined, or replaced when challenged by new evidence, including evidence for interbreeding between Homo sapiens and Homo neanderthalensis and evidence of new putative Homo species  the human fossil record as an example of a classification scheme that is open to differing New putative Homo species interpretations that are contested, refined, or replaced when challenged by new evidence, including evidence for interbreeding between Homo sapiens and Homo neanderthalensis and evidence of new putative Homo species Two of the most recent hominin species to have been discovered and added to our evolutionary tree are Homo denisova and Homo luzonensis. Homo denisova Denisovans were a distinct hominin species that lived between approximately 50,000 and 300,000 years ago, primarily identified through genetic evidence. Nuclear DNA extracted from a finger bone showed that Denisovans were closely related to Neanderthals but represented a separate lineage, leading to their classification as a distinct species, Homo denisova. Due to the limited fossil record, which includes only a few teeth and a partial jawbone, most information about Denisovans comes from their DNA, revealing their significant genetic contributions to some modern human populations, particularly in Melanesians and Australian Aboriginals.  the human fossil record as an example of a classification scheme that is open to differing Homo denisova interpretations that are contested, refined, or replaced when challenged by new evidence, including evidence for interbreeding between Homo sapiens and Homo neanderthalensis and evidence of new putative Homo species Discovery: In 2010, fossils, including a finger bone, a tooth, and a jawbone, found in Denisova Cave, Siberia, Russia. Date: Approximately 50,000 to 300,000 years ago. Characteristics: Identified primarily through DNA evidence, Denisovans exhibited a mix of traits similar to Neanderthals and early modern humans. Their genetic legacy is present in modern human populations, particularly in Melanesians and other Oceanians. Bones Discovered: Finger bone, tooth, and jawbone. Denisova Cave  the human fossil record as an example of a classification scheme that is open to differing Homo luzonensis interpretations that are contested, refined, or replaced when challenged by new evidence, including evidence for interbreeding between Homo sapiens and Homo neanderthalensis and evidence of new putative Homo species Homo luzonensis was a relatively small-bodied hominin that lived on Luzon Island in the Philippines between 50,000 and 67,000 years ago. The fossils revealed a unique mix of both ancient and modern traits: the small, simple teeth suggested a more modern lineage, while the foot bones resembled those of ancient Australopithecus. This unusual combination of features led to the classification of these specimens as a new species, Homo luzonensis.  the human fossil record as an example of a classification scheme that is open to differing Homo luzonensis interpretations that are contested, refined, or replaced when challenged by new evidence, including evidence for interbreeding between Homo sapiens and Homo neanderthalensis and evidence of new putative Homo species Discovery: Fossils found in Callao Cave, Luzon Island, Philippines. Date: Approximately 50,000 to 67,000 years ago. Characteristics: Exhibits a blend of primitive and derived traits, such as small teeth and features shared with other early Homo species, suggesting a unique evolutionary path. Bones Discovered: Includes partial remains such as a femur, finger and toe bones, and teeth. DNA: The preservation of DNA in ancient fossils is Callao Cave challenging, especially in tropical climates like the Philippines, which can affect the quality and quantity of genetic material recovered. Aboriginal and Torres Strait Islander ways of using fossil and DNA evidence (mtDNA and whole genomes) to explain the migration of people’s connection to Country and Place modern human populations around the world, including the migration of Aboriginal and Torres Strait Islander populations and their connection to Country and Place The concept of Country and Place encompasses about 60,000 years of connection. Country and Place are central to Indigenous Australian cultures, reflecting a profound connection to the land and its features. This connection shapes spiritual beliefs, cultural practices, and identity, encompassing a reciprocal relationship where the land provides for the people, and people care for the land. Country: Refers to an area traditionally owned and cared for by an Aboriginal language group or community. It signifies more than just a physical location, encompassing spiritual significance and a deep emotional connection. Place: Describes spaces with defined physical or intangible boundaries that Torres Strait Islander Peoples inhabit and consider their own. These places hold varying levels of spiritual importance.  ways of using fossil and DNA evidence (mtDNA and whole genomes) to explain the migration of Indigenous Australian arrival modern human populations around the world, including the migration of Aboriginal and Torres Strait Islander populations and their connection to Country and Place Indigenous Australians arrived in Australia between 50,000 and 65,000 years ago from Sahul, a prehistoric supercontinent including Australia and New Guinea. The connection to Sahul ended around 10,000 years ago due to rising sea levels. DNA evidence suggests that the first migrants to arrive were distinct groups that came from a single initial migration that, upon arriving, spread rapidly down the western and eastern coasts.  ways of using fossil and DNA evidence (mtDNA Analysis of mtDNA from Aboriginal and whole genomes) to explain the migration of modern human populations around the world, Australians shows that they possess including the migration of Aboriginal and Torres Strait Islander populations and their connection to unique mitochondrial lineages that are Country and Place distinct from those of other populations. These lineages trace back to the initial migration event into Australia, providing evidence of long-term isolation. The separation of the Sahul supercontinent made Aboriginal and Torres Strait Islanders are the longest surviving population of modern humans to have lived in a given location, and are thought to have one of the strongest Connection to Country of any living population on earth. Examples of evidence to connection to ways of using fossil and DNA evidence (mtDNA Country and Place and whole genomes) to explain the migration of modern human populations around the world, including the migration of Aboriginal and Torres Strait Islander populations and their connection to Country and Place Regional Genetic Variation: Within Australia, there are identifiable genetic variations that correspond to different regions, reflecting the long-term adaptation and connection of Aboriginal Australians to specific landscapes. Dreamtime Stories: Over 500 distinct Aboriginal language groups have unique Dreamtime stories that describe the spiritual significance of landscapes and place names. Varied Beliefs and Systems: Aboriginal Australians comprise numerous distinct cultural and language groups, each with its own beliefs, traditions, and social structures.Map Cultural Practices: Rituals and ceremonies tied to specific landscapes are estimated to span over 50,000 years, illustrating an enduring connection. Kakadu National Park: Rock art, including over 20,000 years old, depicts not only daily life but also spiritual and cultural aspects tied to the landscape. Lake Mungo: Evidence from Lake Mungo includes remains of early human activity, such as cremated remains dated to around 42,000 years ago, indicating ceremonial practices. Localised Practices: The way people engage with their Country, such as through land management practices, ceremonies, and storytelling, is often unique to their specific cultural group. This means that practices like fire-stick farming, totemic relationships, and sacred sites are deeply connected to their particular environment and cultural heritage. Land management: Practices such as controlled burning, which has been used for over 30,000 years, demonstrate the sophisticated understanding and management of the land.  ways of using fossil and DNA evidence (mtDNA Challenges of evidence and whole genomes) to explain the migration of modern human populations around the world, including the migration of Aboriginal and Torres Strait Islander populations and their connection to Country and Place The Out of Africa model, which places the advent of Aboriginal Australians at around 50,000–65,000 years, diminishes the traditional view of many First Nations communities who believe that their people have been in Australia since the time of creation. Genomic research carried out by non-Aboriginals into the origins of Aboriginal people in this country can therefore create a degree of angst in these Indigenous communities for a number of reasons: - diminishes their cultural connection to their creation story - challenges their identity and status as First Nations people - risks regarding land rights and status within certain communities