Variation and morphological species

• No two individuals are identical in all traits; variation is a defining feature of life.

• Complex patterns of variation underpin the naming and classification of organisms.

• The morphological species concept groups organisms into species using shared traits.

• This is the original species concept used by Linnaeus.

Gradual speciation and species boundaries

• Speciation is the splitting of one species into two or more.

• It usually occurs gradually as non-interbreeding populations become increasingly different in their traits.

• Because divergence is gradual, deciding whether populations are one species or different species can be arbitrary.

Human chromosome $2$ fusion evidence

• Evaluate the hypothesis that human chromosome $2$ arose from fusion of chromosomes $12$ and $13$ in a shared primate ancestor.

• Use chromosome evidence to judge whether this testable hypothesis is supported.

• NOS: Distinguish a testable hypothesis such as chromosome $2$ origin from a non-testable statement.

Genome-size data and whole genome sequencing

• Use a database to extract genome-size data for taxonomic groups and compare genome size with organism complexity.

• Whole genome sequencing is becoming faster and less costly.

• Current use: research into evolutionary relationships.

• Potential future use: personalized medicine.

Binomial naming and biological species

• Binomial names have two parts: the first identifies the genus; the second distinguishes the species.

• Write the genus with an initial capital and the species name in lowercase.

• Species in the same genus have similar traits.

• The biological species concept defines a species as organisms that can breed and produce fertile offspring.

• This definition has application challenges, and competing species definitions exist.

Chromosome diversity and karyotyping

• Plant and animal species show diversity in chromosome number; humans have $46$ chromosomes and chimpanzees have $48$.

• Diploid cells should have an even chromosome number.

• In a karyogram, classify chromosomes using banding patterns, length and centromere position.

• Apply these chromosome features when interpreting karyotype evidence.

Use the karyogram to compare chromosome length, banding patterns and centromere position, the three classification features required by the syllabus. Source

Genome unity and diversity

• An organism's genome is all of its genetic information.

• Members of one species share most of their genome, while single-nucleotide polymorphisms create some diversity.

• Eukaryote genomes vary in overall size, determined by total DNA, and in base sequence.

• Genome variation between species is much greater than variation within a species.