EVOLUTION

• fossil record: -the identification, interpretation and dating of fossils gives us some of the most direct evidence for evolution • biogeography: -the study of where species occur, and why. this is based on the finding that different regions with similar climatic conditions contain very different animals and plants • modification by descent: -similar structures with same body plan that perform different functions are known as homologous structures -homologous structures provide evidence of evolution because the similarities suggest a common ancestor • genetic evidence: -closely related organisms have more similarities in their DNA -shows how changes in genotype and phenotype are transferred to successive generations

hypothesis: * a tentative explanation of a phenomenon that can be tested and may be accepted or rejected theory: * explanation of an observation that is supported by facts, models and laws

MEIOSIS: * crossing over involving the exchange of genetic material during prophase 1 leads to the formation of gametes with different gene combinations * the random assortment of homologous chromosome pairs on the equator during metaphase 1 also leads to greater variation REPRODUCTION: * random fertilisation where different gene combinations are formed which increases variation in species * random mating of individuals and successful fertilisation occur in a population, the variety of gene combinations formed is even greater MUTATIONS: * changes in sequence of nucleotides may lead to change in the amino acid sequence of protein synthesised

• a type of variation that has a range of phenotypes for the same characteristic • no distinct categories, no limit on value, tends to be quantitative • height, weight, heart rate, etc. • represented by line graph, histogram • controlled by a lot of genes and the environment

• a type of variation where phenotypes fit into seperate categories with no intermediate forms • distinct categories, tends to be qualitative • tongue rolling, fingerprints, eye colour • represented in a bar graph • controlled by a few genes

• lamarckism • darwinism • punctuated equilibrium

LAW OF THE INHERITANCE OF ACQUIRED CHARACTERISTICS: * characteristics developed during the life of an individual can be passed on to their offspring LAW OF USE AND DISUSE: * as an organism uses a structure or organ more regularly, it becomes better developed or enlarged. if an organism does not use a structure or organ frequently, it becomes less developed or reduced in size and may disapear altogether

• there is no evidence that acquired characteristics are inherited to the DNA of an organism’s gametes

• organisms produce a large number of offspring • there is a great deal of variation • some have favourable characteristics and some do not • when there is a change in the environmental conditions or if there is a competition, • then organisms with characteristics, which make them more suited, survive • whilst organisms with unfavourable characteristics, which make them less suited, die • the organisms that survive, reproduce • and thus pass on the allele for the favourable characteristic to their offspring • the next generation will therefore have a higher proportion of individuals with the favourable characteristic • in this way, the characteristics of a population gradually change over a long period of time

• evolution involves long periods of time where species do not change or change gradually through natural selection. • this alternates with short periods of time where rapid changes occur through natural selection • during which new species may form in a short period of time

• a change in the gene pool of a population over millions of years

• a group of organisms of the same species that occupy the same area at a same time • a group of organisms with similar characteristics that can interbreed to produce fertile offspring

• if a population of a single species • becomes seperated by a geographical barrier • then the population splits into two • there is now no gene flow between the two populations • since each population may be exposed to defferent environmental conditions • natural selection occurs independently in each of the two populations • such that the individuals of the two populations become very different from each other • genotypically and phenotypically • even if the two populations were to mix again they will not be able to interbreed • and therefore a new species has formed

• galapagos finches • galapagos tortoises • plants on different land masses -baobabs in africa and madagascar -proteas in south africa and austrailia • any example of mammals on different land masses

• breeding at different times of the year • species-specific courtship behaviour • adaptation to different pollinators in plants • infertile offspring • prevention of fertilisation

• use of insecticides and consequent resistance to insecticides in insects • development of resistant strains of TB causing bacteria to antibiotics, due to mutations in bacteria and failure to complete antibiotic courses • HIV resistance to antiretroviral medication • bill and body size of galapagos finches

• bacteria populations develop resistance by natural selection • bacteria reproduce rapidly • within the population, mutations occur which may produce bacteria that are resistant to antibiotics • mutations introduce variation within the population making some bacteria resistant to antibiotics while others are not • antibiotics kill non-resistant and the resistant bacteria survive • the resistant bacteria reproduce and pass on their mutated genes to their offspring producing a bacterial population with a greater proportion of resistant bacteria

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• two hands, each with five fingers; two feet each with five toes • long arms that rotate freely as shoulder joints allow movement in all directions • naked fingertips and toes ending in flat nails • reduced snout with weakened sense of smell • stereoscopic vision as the eyes face forward providing depth of field • eyes have cones and rods making colour vision possible • brain centres that process information from hands and eyes are enlarged • no tail • sexual dimorphism where males and females are clearly distinguished • have molars and premolars with rounded cusps

BIPEDALISM: * humans - foramen magnum in a forward position. more curved spine. short-wide pelvis * african apes - foramen magnum in a backward position. less curved spine. long, narrow pelvis BRAIN SIZE: * humans - large frontal area, which requires a large cranium and a higher forehead to house and protect it. * african apes - smaller brain, less developed TEETH (DENTITION): * humans - small teeth. canine is smaller. no gaps between incissors and canines. * african apes - large teeth. large canines. gaps between incisors and canines PROGNATHISM: * humans - shorter jaw. does not need strong muscles for their diet of softer foods. face is small and flatter in the front. * african apes - longer jaw. stonger muscles required for their diet of tough foods. face is large and protruding in the front. PALATE SHAPE: * humans - palate is small and semi-circular in shape * african apes - palate is long and rectangular in shape CRANIAL RIDGES: * humans - no cranial ridge as humans have smaller jaws and do not need large jaw muscles * african apes - cranial ridge across the top of the cranium BROW RIDGES: * humans - not well developed. more upright brow, which holds a larger brain * african apes - brow ridges well developed

• evidence from fossils of different ages show that the anatomical characteristics of organisms changed gradually over time.

• age: 5 - 4 mya • scientist : tim white • found in the afar valley of ethiopia anatomical features: * brain size: 300-350 ml * forward position of foramen magnum * protruding jaws * heavy brow ridges * pelvis structure: bipedal and tree climbing

• age: 4 - 2.7 mya • scientist: donald johnson • found in the afar valley in ethiopia anatomical features: * brain size: 375-550 ml * forward position of foramen magnum * bipedal * protruding jaws * heavy brow ridges * canines large and pointed