Systemic lupus erythematosus, often abbreviated as SLE or lupus, is a systemic autoimmune disease (or autoimmune connective tissue disease) in which the bodyâs immune system mistakenly attacks healthy tissue.ystemic lupus erythematosus, often abbreviated as SLE or lupus, is a systemic autoimmune disease (or autoimmune connective tissue disease) in which the bodyâs immune system mistakenly attacks healthy tissue.
Natural selection will only cause evolution if there is enough genetic variation in a population. Before the discovery of Mendelian genetics, one common hypothesis was blending inheritance. But with blending inheritance, genetic variance would be rapidly lost, making evolution by natural selection implausible.
In most cases, such changes are neutral and have no effect or they are deleterious and cause harm, but occasionally a mutation can improve an organism's chance of surviving and of passing the beneficial change on to its descendants. Mutations are the necessary raw material of evolution. Mutations can be caused by many factors including environmental insults such as radiation and mutagenic chemicals. Mutations are sometimes attributed to random chance events.