Life Science Notes PDF

Bottleneck Affect few members to survive ,...

Bottleneck Affect few members to survive , but not necessarily the ones with An event causes only a fitness change in allele frequencies the highest > - oeg forest fire Founder Affect of individuals become isolated and start a new population they may have A small group - different allele frequencies to the original population South unusually high frequency of the eg. Afrikaner population in Africa - give Huntington's disease that causes Gene Flow - When a member of a different population immigrates and joins another population introduce new alleles into the population - They may non-native species transported humans eg. by Evidence For Evolution A. The Fossil Record the remains or evidence of past life recorded in rock (molds impressions, bones , shells, teeth, preserved in ice. etc Fossil : , , be determind fossils position the layers. The oldest fossils found below. 2 Relative dating - age can by the in are surface fossils nearer the Isetopes atoms wh the a re younger are. Absolute dating 2 - uses the principle of radioactive dating same number of and protons ↳ The half-life of known radioactive compounds never changes different numbers of neutrons. Over ↳ Example of absolute dating time Istopes decay and change o Potassium -40 decays to Argon - 40 Potassium -40 deays to half its original amount in 1 3 billion years. o o I there are equal amounts Potassium - 40 and Argon-40 in a rock sample, how old is the rock sample ? Answer: 1 3 billion years. - gradual evolution of the modern horse. Ex. Fossil remains clearly show the. Comparison B of Anatomy These indicate the species are related.. 1 HomologousStructures - (divergent evolution) (similary internally) - internal structure , same starting point These indicate species are not related , but occupy Analogous structures - I. Similar niches /covergent evolution) (similar externally) external structure , shaped by Natural Selection structures : Examples of analogous and porcupines I have similar niche - a hedgehogs Need to be careful when comparing structures - analogous structures don't share evolutionary links /recent common ancestors longer useful function. Vestigal those that structures no serve a 3 - have been useful for our ancestors ↳ May ofx. Human appendix , tailbone /coccyx) 0 Ex. The flightless cormorant (Phalacrocorax harrisi) , also known as the Galapagos Cormorant C. Comparitive Embyology o Embryo : An unborn or unhatched offspring in the process of development similarities in Compactive Embryology - examination of differences and embryo development before birth o ) ↳ ex. comparison of a lizard, tortoise , pig , and early human embryos · Tell which ones are closely related (share a recent common ancestor). Behaviour Comparisons D 0 Tool use -> > Similar behaviours indicate common ancestors - > use as many different types of evidence o Parenting. Biochemical Comparisons E - > the best evidence Project) allowed for the comparison of DNA from different species and · Recent developments /Human Genome have species This new evidence is the strongest yet that consistantly supports evolutionary theory Groups within. ↳ Organisms which have much of their DWA in common must be closely related it. they have split from a common ancestor compactively recently (in geographical terms)  ↳ 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