Evolution

Evolution

1. Phylogeny

   • PHYLOGENY is the evolutionary relationships between organisms
   • PHYLOGENETICS is the study of evolutionary history of groups of organisms, it shows which organisms are related and how closely related they are
   • PHYLOGENETIC TREES
     • 1) A PHYLOGENETIC TREE ( or evolutionary tree) is a diagram used to represent tthe evolutionary relationships between organisms, they have branches which show that different species have evolved from a common ancestor
     • 2) The earliest species is found at the base of the tree and the most recent species are found at the tips of the branches
     • 3) The trees are made by looking at the sim and diff in the species' physical characteristics and genetic makeup. Most of the evidence has been gained through fossils
     • 4) The tip of the tree shows descendant organisms, The nodes ( points new lines break off) show a common ancestor of the two. They are called sister groups if they branch out from same ancestor. The closer the branches the closer the evolutionary relationship
   • ADVANTAGES FOR PHYLOGENETIC CLASSIFICATION
     • Relationship between classification and phylogeny
       • Phylogeny can be done without reference to classification.Whereas classification uses knowledge of phylogeny to confirm the classification groups are correct or causes thhem to change
         • For example dolphin has many of the fish's characteristics so it could be classified as a fish, but the knowledge of the phylogeny of dolphins confirms it's classification as a mammal
     • Phylogeny produces a continuous tree where classification uses taxonomical groups. Scientists aren't forced to put organisms in specific groups that they don't quite fit
     • The hierachy of classification can be misleading because it implies different groups within the same rank are equivalent. However some have longer history than others , different levels of diversity and different biologically
     • Linnaean system is the classification system

2. EVOLUTION is the slow and continual change of organisms from one generation to the next

3. Evidence for evolution

   • DEVELOPING THE THEORY OF EVOLUTION
     • DARWIN
       • His observations
         • 1) Organisms produce more offspring than survive
         • 2) There's variation in the characteristics of members of the same species
         • 3) some of the characteristics can be passed on from one generation to the next
         • 4) individuals best adapted to the environment are more likely to survive
         • 5) He noticed different islands had different finches. The birds were similar in many ways but their beaks and claws were different shapes and sizes
         • 6) He realised the finches' beaks was linked to the food available on the island, the bird born with the beak more suited for the island would survive longer
         • 7) Throughout his trip he sent specimens organisms back to the uk for other scientists to preserve and classify
       • Natural selection
         • 1) Individuals within a population show variation in their phenotypes (their characteristics )
         • 2) Selection pressures ( environmental factors like predation , disease and competition) make it hard to survive
         • 3) The individuals with better adaptations are more likely to survive and reproduce successfully and pass on their advantageous characteristics to their offspring
         • 4) Over time, the proportion of the population that have the advantageous characteristics increase
         • 5) Over generations this leads to evolution as the favourable characteristics become more favourable adaptions become more common in the population
         • There's genetic variation, then selection pressures, then reproductive success
     • WALLACE
       • 1) He was working at the same time as Darwin
       • 2) He independently came up with the idea of natural selection and wrote to Darwin for peer review
       • 3) His ideas were similar to Darwin's so they published their papers together
       • 4) Wallace realises that the warning colours on butterflies are used by some species to deter predators from eating them, this was an example of advantageous adaption that had evolved by natural selection
       • 4) Darwin pulished "on the origins of species" the book was controversial as evolution conflicted with the idea that God created animals and plants . Contradicted as he said humans evolved from apes whereas bible says God made man in his image
   • PALAEONTOLOGY
     • 1) PALAEONTOLOGY is the study of fossils and fossil records
     • 2) FOSSILS are the remains of prehistoric plant or animals preserved in a rock
     • 3) By arranging fossils in chronological (date) order, gradual changes in organisms can be observed that provide evidence for evolution
     • Evidence provided by fossil record
       • 1) Fossils of simplest organisms like bacteria and algae are found in the oldest rocks while fossils of more complex organisms like vertebrates are found in recent rocks.
         • This supports the evolutionary theory that simple life forms gradually evolved over long period of time into more complex ones
       • 2) The sequence which organisms are found matches their ecological links to each other e.g plant fossils appear before animal fossils, it's consistent because animals need plants to survive
       • 3) By studying similarities in the anatomy of fossil organisms, scientists can show how closely related organisms have evolved from the same ancestor
       • 4) Fossils allow us to investigate relationships between extinct and living organisms
       • 5) However the fossil record is not complete, the conditions needed for fossils to form are not always present and many of the fossils have been destroyed by the Earths movement like volcanoes and not been found
   • COMPARATIVE ANATOMY
     • 1) COMPARATIVE ANATOMY is the study of sim and diff between the anatomy of organisms
     • 2) Because the fossil records are incomplete scientists can look at the sim and diff in anatomy of living species to see evolutionary relationships
     • Homologous structure
       • 1) HOMOLOGOUS STRUCTURE is a structure that appears different in different organisms but has the same underlying structure due to a common ancestor. Fossil records can be used to see structures of those that live in the past
       • 2) An example is a pentadactyl limb of vertebrates. The same bones are adapted to carry out a range of functions. Shows all vetebrates have evolved from a common ancestor so a vertebrate limb has evolved from the same structure
       • 3) The presence of homologous structures gives evidence for DIVERGENT EVOLUTION
       • 4) DIVERGENT EVOLUTION is when different species have evolved from a common ancestor each with different adaptive features
       • 5) This type of evolution will occur when closely related species diversify to adapt to new habitats as a result of migration or loss of habitat
   • COMPARATIVE BIOCHEMISTRY
     • 1) COMPARATIVE BIOCHEMISTRY is the sim and diff between the chemical makeup of organisms (proteins and other molecules)
     • 2) Some important molecules are highly conserved among species
     • 3) Slight changes in the molecules can identify evolutionary links
     • 4) Scientists compare the sequence of amino acids in proteins and compare antibodies. Organisms that diverged ( evolved to become diff species) away from each other more recently have similar molecules, because less time has passed for changes In proteins and other molecules to occur
     • DNA
       • 1) Evolution is caused by gradual changes in the base sequences of organisms' DNA.
       • 2) So organisms that diverged away from each other more recently should have more similar DNA because less time had passed for changes in DNA sequence to occur
       • 3) Scientists study the DNA in mitochondria and not the nucleus to see how closely related organisms are
       • 4) Ribosomal RNA has a very slow rate of substitution so it's commonly used together with fossil info to determine relationships between ancient species

4. Variation

   • VARIATION is the difference in characteristics between organisms
   • TYPES OF VARIATION
     • INTERSPECIFIC VARIATION
       • It's the difference between organisms of different species e.g mouse has 4 legs, teeth, fur and birds have 2 legs, 2 wings, beak
       • It's the widest type of variation
     • INTRASPECIFIC VARIATION
       • The differences between organisms of the same species e.g people vary in height build, hair color and intelligence
   • CAUSES OF VARIATION
     • GENETIC
       • Differences in genetic material an organisms inherits from its parents leads to GENETIC VARIATION
       • GENETIC VARIATION is is a variety of different combinations of alleles in a population
       • Genetic variation is due to genes and alleles an individual processes
       • 1) ALLELES- ( diff versions of same gene) genes have different alleles. Each characteristic has a gene and alleles produce different effects. e.g blood has 4 alleles A,B,AB,O. Individuals in a species may inherit diff alleles
       • 2) MUTATION- (change in genetic material which can affect phenotype of organism) changes in DNA sequence leads to changes in genes and the proteins they are coded for and can affect physical and metabolic characteristics. If mutaion happens in body cells just individual is affect butt if it happens in gamets, it's passed on to offspring. Both can led tp variation
       • 3) MEIOSIS- gamets (sex cells-ovum and sperm) are produced by meiosis in organisms that produce sexually Each gamete has half the genetic material of a parent cell.The genetic material inherited from 2 parents is mixed up this leads to the gamets of an individual showing variation
       • 4) SEXUAL REPRODUCTION- The offspring produced from 2 individuals inherits genes (alleles) from each parent and therefore differs from parents
       • 5) CHANCE- during sexual reproduction there is random fertilisation . The individuals produced differ from their siblings because each has a unique combination of genetic material
       • 3-5 are all aspects of sexual reproduction, there's more variation in organisms that reproduce sexually than asexually. Asexual reproduction makes clones. You can only increase variation in these b mutation
         • Eye colour
         • Blood type
         • Antibiotic resistance
     • ENVIRONMENT
       • 1) All organisms are affected by environment they live in, plants are affected more than animals because they cant move e.g roses planted where they have more sunlight will grow larger than the ones in the shade
       • 2) An example of a characteristic caused by environmental variation are scars, they come because of accidents or disease, no genetic origin
         • Accents
     • ENVIRONMENTAL + GENETIC CAUSES OF VARIATION
       • 1) If you have tall parents you'll most likely be tall cause of the genes however if you have a poor diet or suffer from disease you may only grow below average height
       • 2) Another example of both is skin colour, how much melanin it has. The more melanin the darker, your skin colour at birth is determined by genes but if you expose your skin to sunlight your skin turns darker because more melanin is produced
         • Height
         • Flagellum
   • REPRESENTING VARIATION GRAPHICALLY
     • CONTINUOUS VARIATION
       • This is when individuals in a population vary within a range-there are no distinct categories
         • Height
         • Mass
         • milk yield
         • Surface area of plants
         • Length of flagellum
     • DISCONTINUOUS VARIATION
       • This is when there are 2 or more distinct categories-each individual falls into only one of the categories there are no intermediates
         • Blood group ( A, B, AB or O)
         • Colour of courgettes ( yellow dark green or light green)
         • Seed shape ( pea plants have smooth or wrinkled)
         • Antibiotic resistance of microorganisms ( it either is or isn't)
         • Pigment production of microorganisms ( some can make coloured pigment others cant
     • NORMAL DISTRIBUTION CURVE
       • When continuous variation data are plotted on a graph the give a bell shaped normal distribution curve
       • bell shaped
       • CHARACTERISTICS OF NORMAL DC
         • 1) The mean, mode and median are the same
           • Mean can be used to tell if there's variation between samples, if they have the same mean then the mean number doesn't vary
         • 2) Has a bell shape which is symmetrical about the mean
         • 3) 50% of the values are greater than the mean and 50% are less
         • 4) Most values lie close to the mean value, extremes are rare
   • Other Statistical tests
     • T TEST
       • The T TEST is used to compare the means of data values between 2 populations
         • Data must be normally distributed. Use diff sample sizes
       • Use the standard deviation of both values
       • n1 and n2 is the total of values in each samples 1 and 2
       • NULL HYPOTHESIS- a prediction that there will be no significant difference between specified populations any observed difference will be due to chance
         • Reject null hypothesis if p is less that 5% (0.05) ( significant diff between 2 means)
         • Accept null if p is 5% more than 5% (0.05) (no significant diff)
       • To work out DEGREE OF FREEDOM you find the total of number of samples then take away 2
     • SPEARMAN'S RANK CORRELATION
       • 1) SPEARMAN'S RANK CORRELATION shows correlations (relationships) between 2 sets of data
       • 2) no correlation- no relationship
       • 3) Positive correlation- as one increases so does the other
       • 4) Negative correlation- as one increases the other decreases
       • Calculate
         • 1) You have to rank the data and find the difference then square it and find the sum
         • 2) n is the number of samples
         • 3) you do 1-(6 times the sum of d squared, divided by n(n squared-1)
         • 4) If value is closer to +1 then it's perfect correlation, if closer to -1 it perfect negative, if its 0 then no correlation
         • if p= 0.5 or less reject null,5% chance that correlation that it's due to chance

5. Standard Deviation

   • 1) STANDARD DEVIATION is a measure of how spread out the data is from the mean|
   • 2) The greater the standard deviation the greater the spread and therefore has a higher variation
   • 3) If all the values are similar and close to the mean then the data varies little so the graph would be steep and standard deviation is small
   • Work out the value by finding the mean and taking it away from the value, then square it and add all the values up ad divide by n-1 then square root it

6. Adaptation

   • ADAPTIONS are characteristics that increase an organisms chance of survival and reproduction in it's environment
   • BEHAVIOURAL ADAPTIONS
     • 1) BEHAVIOUAL ADAPTIONS are ways organisms act to increase it's chance of survival, they can be learnt or inherited from parents
     • Examples
       • 1) POSSUMS sometimes play dead if they are being attacked by predator, this increases their chance of survival
       • 2) SCORPIONS dance before mating to attract a mate of the same species, increases chance of successful mating
       • 3) Brown BEARS hibernate during winter this conserves energy
       • 4) BIRDS migrate when environmental conditions are more favourable
   • PHYSIOLOGICAL ADAPTIONS
     • 1) PHYSIOLOGICAL ADAPTIONS are processes that take place in an organisms body to increase the chance of survival
     • Examples
       • 1) SNAKES make venom to kill their prey and PLANTS make poisons in their leaves so they don't get eaten
       • 2) Some BACTERIA make antibiotics to kill other species of bacteria. This means there's less competition
       • 3) WATER HOLDING FROG can store water in it's body allowing it to survive in the desert for more than a year without access to water
   • ANATOMICAL ADAPTIONS
     • ANATOMICAL ADAPTIONS are physical features (internal and external)
     • Examples
       • 1) BODY COVERING animals have: hair, scales. feathers and shells. This help animals to stay warm, to fly (feathers)
       • 2) CAMOUFLAGE - the colour of an animals skin helps it blend in with the environment so it's harder for predators to spot
       • 3) TEETH- the shape and type of teeth an animal has is related to its diet
     • EVIDENCE FOR CONVERGENT EOLUTION
       • ANALOGOUS STRUCTURE are structures that have adapted to do the same function but have different origins
       • CONERGENT EVOLUTION is when unrelated species start to share similar traits because of similar environments or other selection pressures ( factors that affect an organisms chance of survival or reproductive success)
       • Examples
         • MARSUPIAL AND PLACENTAL MOLES they aren't closely related, they evolved on different continents-they share similar anatomical structures like they look alike ( similar environments)
           • They have small eyes- don't need them cause they go underground to get their food
           • Claws are specialised for digging and body is tube like to go through tunnels

7. Examples of evolution

   • ANTIBIOTIC RESISTANT BACTERIA
     • 1) When bacteria replicate, DNA can be altered and this often leads to death
     • 2) Some bacteria are resistant due to mutations
     • 3) Allele for resistance is passed on and number of individuals with allele increase
   • PEPPERED MOTHS
     • 1) Most peppered moths were pale in colour and this was camouflage for the light coloured trees-higher chance of survival. The dark moths were easily seen and eaten by birds
     • 2) Industrial revolution led to darker trees because of the soot from the factories
     • 3) Dark moths became better adapted, more of them survived and the allele was passed on to offspring. Population of dark moths increased
   • SHEEP BLOWFLIES
     • 1) They lay eggs near sheep's tail and thru can cause sores and be fatal
     • 2) Pesticides were used to kill them, within 6 years they developed resistance
     • 3) Allele for the resistance was passed on and resistant population evolved
   • FLAVOBACTERIUM
     • 1) Evolution is negative result of selection pressures ( factors that affect an organisms chance of survival and reproduction)
     • 2) Flavobacterium digest nylon 6 ( waste product from factories)
     • 3) They are beneficial to humans as they clear waste and nylon 6 is a source of nutrient for the flavoabacterium