Definitions of Species Scientists have been classifying organisms into species for hundreds of years, in order to investigate the diversity of life that exists today and in the past There is diffic...
Allopatric & Sympatric Speciation Evolution?causes?speciation: the formation of?new species?from pre-existing species over time, as a result of?changes to gene pools?from generation to generati...
Theory of Evolution A species can be defined as a group of organisms that are able to?interbreed?and?produce fertile offspring Members of one species are reproductively isolated from members of ano...
Examples of Selective Breeding Selective breeding (or artificial selection) is the process by which?humans choose?individuals with?desired traits?to reproduce, with the aim of producing offspring w...
Artificial Selection Artificial selection is the process by which?humans choose?organisms with?desirable traits?and selectively breed them together to enhance the expression of these desirable trai...
Natural Selection: Hardy-Weinberg Principle The Hardy-Weinberg principle states that if certain conditions are met then the?allele frequencies of a gene within a population will not change from one...
Natural Selection: Antibiotic Resistance When humans experience a pathogenic bacterial infection they are often prescribed?antibiotics?by a healthcare professional Antibiotics are chemical substanc...
Natural Selection: Changes in Allele Frequencies Evolution involves changes in allele frequencies over time This can be caused by?natural selection Selection pressures (caused by the environment) i...
Natural Selection: Types of Selection Environmental factors that affect the chance of survival of an organism are?selection pressures For example, there could be high competition for food between l...
Natural Selection Every individual within a species population has the?potential to reproduce?and have offspring which contribute to population growth If the offspring for every individual survived...
Variation: t-test Worked Example Worked Example The ear length of two populations of rabbits was measured.Ear lengths of population A (mm): 62, 60, 59, 61, 60, 58, 59, 60, 57, 56, 59, 58, 60, 59, 5...
Variation: t-test Method A statistical test called the?t-test?can be used to?compare the means of two sets of data?and determine whether they are?significantly?different or not The formula for the ...
