Theme A: A3 Unity and Diversity Organisms - A3.2 Classification and Cladistics

Question 1

Hybridisation

Answer 1

The process of crossing two genetically different individuals or species to produce offspring with characteristics of both

Question 2

Introgression

Answer 2

Hybrids form over many generations but, instead of having an equal share of the original 2 species’ genetics information, there is an unequal contribution from each species. Achieved by repeated backcrossing where the hybrid organisms breeds with one of the original parent species to produce offspring.

Question 3

Molecular systematics

Answer 3

classifying organisms using molecular differences in protein sequences and DNA.

Question 4

Phylogeny

Answer 4

study of the evolutionary past of a species

Question 5

Phylogenetic tree

Answer 5

comparing genetic profiles of different species allows us to construct a phylogenetic tree, one showing the evolutionary relationships between species by showing which develop from a common ancestor

Question 6

Clade (a.k.a. monophyletic group)

Answer 6

a group comprised of the most recent common ancestor of that group and all its descendants. Characteristics of organisms within such a group can be predicted as they’re shared within a clade. A clade can comprise of one or multiple species.

Question 7

Cladistics

Answer 7

a natural system of classification for grouping taxa, based on the characteristics that have evolved most recently. the concept of common descent in crucial to the system.

another definition: A method of classifying organisms based on common ancestry and evolutionary relationships.

Question 8

taxa (sing. taxon)

Answer 8

are hierarchical groups used in biological classification to organize and categorize organisms based on shared characteristics and evolutionary relationships. Examples include domain, kingdom, phylum, class, order, family, genus, and species.

Question 9

Common Descent

Answer 9

The principle that all living organisms share a common ancestor and have diverged over time through evolutionary processes such as mutation, natural selection, and genetic drift.

Question 10

primitive traits (plesiomorphic traits)

Answer 10

characteristics that have a similar structure and function and evolved early in the history of the organisms being studied.

Question 11

derived traits (apomorphic traits)

Answer 11

characteristics with a similar structure and function and evolved more recently, in the form of modifications of a previous trait.

Question 12

DNA hybridization

Answer 12

The process of combining two complementary single-stranded DNA (or RNA) molecules to form a double-stranded molecule through base pairing. It is used to identify genetic similarities or to detect specific nucleotide sequences in experiments.

Question 13

molecular clock

Answer 13

A method that uses quantitative biochemical data (the number of differences between DNA, RNA, or protein sequences in different species) - or the rate of genetic mutations - to estimate the time of speciation events between different species or populations.

Question 14

homologous

Answer 14

Structures, chromosomes, or sequences that share a common evolutionary origin but may serve different functions in modern organisms.

Question 15

cladogram

Answer 15

a diagram used to visually represent the findings of cladistics.

Question 16

Internal Transcribed Spacer (ITS) region

Answer 16

The ITS region is a segment of non-coding DNA located between the small subunit (SSU) and large subunit (LSU) ribosomal RNA (rRNA) genes in the genome. It is transcribed as part of the precursor rRNA and later removed during RNA processing. The ITS is highly variable among different species, making it a valuable genetic marker for phylogenetic studies and species identification, especially in fungi, plants, and some protists.

Question 17

monophyletic

Answer 17

A group of organisms that includes a common ancestor and all its descendants, representing a single branch on the tree of life.

Question 18

paraphyletic

Answer 18

text book: term used to describe species on separate branches.

chatgpt: A group that includes a common ancestor and some, but not all, of its descendants.

Question 19

circumscription

Answer 19

the process of placing taxa where they clearly show monophyletic groups, indicating they all a share a recent common ancestor. reclassifying a taxon and moving branches means changing a species’ circumscription.