Zadanie 8, Paper 2, listopad 2022, Biologia IB HL

(a) Several descendant species diversify from a shared ancestor. ✔

Homologous structures retain similarities. ✔

These structures can acquire different functions. ✔

Different environments or selection pressures favour different adaptations. ✔

A correctly explained example, such as diversification of finch beaks or modified mammalian limbs, supports the account. ✔

(b) Polyploidy means more than two complete chromosome sets. ✔

It can arise through meiotic errors producing unreduced gametes. ✔

Genome replication without subsequent nuclear or cell division can increase ploidy. ✔

A ploidy difference can cause reproductive isolation. ✔

A diploid–tetraploid cross can produce a sterile triploid. ✔

Failure to interbreed successfully separates the gene pools and can establish a new species. ✔

A valid example of speciation by polyploidy, such as in Persicaria. ✔

Chromosome doubling can restore fertility in an otherwise sterile interspecific hybrid. ✔

(c) Use a binomial scientific name. ✔

The first word is the genus and the second identifies the species OR the genus begins with an uppercase letter and the second word with lowercase. ✔

Scientific names allow international communication OR names are formally published. ✔

Study morphology, reproductive traits, chemical features or DNA. ✔

Place the plant with species sharing relevant traits, such as in an appropriate genus. ✔

Classification should reflect evolutionary relationships OR use multiple informative features. ✔

Convergent analogous traits should not be mistaken for shared ancestry. ✔

Traditional taxa form a hierarchy, for example kingdom, phylum and class. ✔

A clade comprises descendants of a shared ancestor. ✔

DNA or amino-acid sequences help infer clades and relationships. ✔

Cladograms represent hypothesized relationships among clades. ✔

Nodes represent divergence of lineages. ✔

Nested clades can be used instead of imposing fixed taxonomic ranks. ✔

Quality: the response is understandable on first reading, concise and has little repetition or irrelevant content. ✔

(a) Any3, maximum3. (b) Any5, maximum5; a claim about non-disjunction of a single chromosome pair does not define whole-genome polyploidy. (c) Any7, maximum7; also accept two valid old plant-phylum names if volunteered, but these are not required and seven current-guide points are available. Independent quality mark1. Total16.