Life Science Notes 2 PDF

↳ Our DNA and that of a chimpanzee is more than 98 5 %....

↳ Our DNA and that of a chimpanzee is more than 98 5 %. identical othis suggets a close relationship and a relatively recent divergence from a common ancestor o Gorillas and Baboons have somewhat less 195-97 %) and mice have 80 % identical DNA shows that wastes excreted from birds and reptiles have the same chemical ↳ fridence make up ↳ Hormones (ie. Insulin) from cows and pigs can be injected into humans ↳ Protein and Enzymes C, respitory enzyme to all animals is only slightly different in different species. · Ex. Cytochrome a common DNA of the gene codes for cytochrome c in a human, and in a mouse · Here are sequences differ between the species. nucleotides this gene only 30/shaded in blue) two in of the 315 F. Biogeographical ↳ The geographic distribution of species No rabbits in South America Marsupials only found in Australia · o Fossils of Ferns found in Antartica Species only found geographical in Endemic species - one location and nowhere else in the world ↳ Patterns in Natural Selection NO SELECTION : If the population is large , mating random and no selective pressure on the traits , then individuals will show a range of traits Polygenetic · There are more individuals that traits eg. show the middle range of a trait Height leg medium. coat lengths) , and fewer at the extremes leg. short and long coats) o Over time little change will occur in the population  STABAILISING SELECTION : the two extremes of trait. For example , plant height A plant that is too selective pressures against a. short may not be able to compete with other. However, extremely plants for sunlight tall plants may be more susceptible selection pressures select against the extremes and maintain Wind damage. Combined these two plants of medium height. to , · The number of plants of medium height will increase while the number of short and tall plants will decrease DIRECTIONAL SELECTION : Envoirmental conditions favour individuals of one extreme , and the other extreme of the trait expirences selection against. The result it is that the population's trait distrubtion shifts towards the other /favoured) extreme , there was once selection pressure Eg. giraffe necks - · short necks, since individuals with short necks could not against leaves to feed on. As a result, the distribution of reach as many · The mean of the populations graph neck length shifted to favour individuals with long necks. Shifts to right the Caverage) DISRUPTIVE SELECTION individuals in the middle of the trait selection pressures act against distribution · The result is a bi-modal , or two peaked curve , in which the two create their smaller curves extremes of the curve own fg. Imagine a plant of extremely varied heights , that is pollinated by 3 different pollinators attracted to short plants preferred the plants of medium heigh dissappeared from an area, ↳ One If the pollinator that ↳ Another that preferred plants of medium height medium height plants would be selected against and the population would 4 A third that only visited the tallest plants tend to lear towards both short and tall, but not medium height plants · such a population , in which multiple distinct forms or morphs exist is said to be polymorphic selection could · Given enough time , this type of result in the formation of two new separate species Speciation Species : a group of organisms that can breed together to produce fertile offspring They reproductively isolated no genetic exchange - are ↳ with this definition : Problems ↳ Does not include organisms that reproduce by other means ↳ some separate species can produce fertile offspring ex. The "Pizzly hear" How does One species Split into Two ? · Reproductive Isolation must happen · Geography (geografical isolation) - examples : river formation /forms and separates species like insects) · Time Itemporal isolation) same habitat mate during different seasons leading to reproductive isolation species of frog - in the - examples : two · Behaviour (behavioural isolation( -examples : a species of bird uses a unique mating song that other species don't recognize · Habitat (ecological isolation) two species live in the same habitat but one lives by the water and the other prefers dry land. - example : · Reproductive Isolation means that different selective pressures exist between the two populations from generation to the next , evolve. Natural selection modifies populations · one causing them to · Sometimes evolutionary changes are so great that some organisms can no longer interbreed with the original species · When this happens it is called speciation