QCAA Biology Continuity of life on Earth

A clade (or monophyletic group) is specifically defined in phylogenetics as a group containing a common ancestor and all of its lineal descendants.

While a clade is a subset of a larger group, 'subgroup' is a generic term and does not specifically define a lineage consisting of an ancestor and all its descendants.

A population refers to a group of individuals of the same species living in a specific geographic area at the same time, not a complete evolutionary lineage.

A community is an ecological term describing a group of interacting populations of different species in a shared environment, not a group defined by ancestry.

Point mutations involve a change in the DNA sequence of a gene; this alteration creates a new variant of the gene, which is the definition of a new allele.

Non-disjunction is an error during cell division where chromosomes fail to separate, leading to an abnormal number of chromosomes (aneuploidy) rather than creating new alleles.

Random fertilisation combines existing alleles from two parents to create unique genotypes in offspring, but it does not generate new genetic variants.

Independent assortment shuffles existing chromosomes into new combinations during meiosis, increasing genetic diversity without creating new alleles.