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 ...
Variation: Discontinuous & Continuous The term variation refers to the differences that exist between at least two things (be it a level, amount, quantity or feature of something) In relation t...
Variation: Phenotype The observable characteristics of an organism are its phenotype Phenotypic variation is the difference in phenotypes between organisms of the same species In some cases, phenot...
Gene Control: Transcription Factors Prokaryotes use operons to control the expression of genes in cells Eukaryotes also use transcription factors to control gene expression A transcription factor i...
Gene Control: Lac Operon Regulatory genes control structural genes and their levels of protein production Regulatory genes sometimes have control over several structural genes at once Structural ge...
