IB Biology

A Unity and Diversity

A1.1 Water

A1.2 Nucleic acids

A2.1 Origins of cells

A2.2 Cell structure

A2.3 Viruses [HL only]

A3.1 Diversity of organisms

A3.2 Classification and cladistics [HL only]

A4.1 Evolution and speciation

A4.2 Conservation of biodiversity

B Form and Function

B1.1 Carbohydrates and lipids

B1.2 Proteins

B2.1 Membranes and membrane transport

B2.2 Organelles and compartmentalization

B2.3 Cell specialization

B3.1 Gas exchange

B3.2 Transport

B3.3 Muscle and motility [HL only]

B4.1 Adaptation to environment

B4.2 Ecological niches

C Interaction and Interdependence

C1.1 Enzymes and metabolism

C1.2 Cell respiration

C1.3 Photosynthesis

C2.1 Chemical signalling [HL only]

C2.2 Neural signalling

C3.1 Integration of body systems

C3.2 Defence against disease

C4.1 Populations and communities

C4.2 Transfers of energy and matter

D Continuity and Change

D1.1 DNA replication

D1.2 Protein synthesis

D1.3 Mutation and gene editing

D2.1 Cell and nuclear division

D2.2 Gene expression [HL only]

D2.3 Water potential

D3.1 Reproduction

D3.2 Inheritance

D3.3 Homeostasis

D4.1 Natural selection

D4.2 Stability and change

D4.3 Climate change

Question rangeA3.2.4 (HL)—Clades

Analysis of the genome of primates reveals many DNA segments that have been duplicated. It is possible to deduce the stage in evolution at which segmental duplications (SDs) occurred by comparing human and other primate genomes. Human-specific SDs occurred after humans and chimpanzees diverged. Human-chimpanzee shared SDs occurred after the common human-chimpanzee ancestor diverged from gorillas and so on. It is possible to estimate the rates at which SDs occurred during evolution using knowledge of when the primates changed. In the chart the bars indicate numbers of shared SDs and the line shows estimates of the rate of SDs per millions of years (Myr).

[Maximum number: 1]

Which encircled area shows a clade?

[Maximum number: 1]

The scientific name of the great egret has recently been changed from Casmerodius albus to Ardea alba.

What is a possible reason for the reclassification of egrets?

Allopatric speciation

Discovery of different ancestry

A change in the mating behaviours

Change in habitat and geographic range

[Maximum number: 1]

What can be deduced from this cladogram?

Baboons do not share a common ancestor with gorillas, humans and chimpanzees.

Humans and chimpanzees are more closely related to each other than to gorillas and baboons.

The common ancestor for all four groups is the baboon.

The splitting events which separated the four groups took place at equal time intervals.

[Maximum number: 1]

The cladogram shows one theory of how species of hominin evolved.

What can be deduced using the information in the cladogram?

The closest species to K. platyops is A. africanus.

A. afarensis is extinct.

The DNA of H. sapiens is the same as that of H. ergaster.

H. sapiens and P. robustus shared a common ancestor.

[Maximum number: 1]

The cladogram shows the evolutionary relationships between a number of animal groups.

What can be concluded from this cladogram?

Tuna evolved from sharks.

Crocodiles are more closely related to birds than to whales.

Frogs, humans and whales do not share a common ancestor.

Shark and tuna evolved later than humans.