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← Theoretical 2

Q87 — Rearing Environment and Social Bonds in Ravens

Theoretical 2 Real exam question — full text reproduced under IBO's CC BY-NC-SA 4.0 license
Development & Learning

To investigate the social behavior among ravens (Corvus corax), young individuals were divided into three groups. In Group A, all individuals came from four different families raised by their parents (“parent-raised”). In Group C all individuals came from a mixed population raised by a human (“hand-raised”). In Group B, some individuals came from the human-raised population and some from a raven family (“parent-raised and hand-raised”). The strength of social relationships was measured during various seasons and shown on a graph.

Three rows of social-network graphs across three seasonal periods (October-December, January-March, April-July). Row (a) parent-raised individuals; row (b) a mixed group with some parent-raised individuals marked by red squares; row (c) hand-raised individuals. Node size reflects sociability, and edge thickness/color reflects relationship strength: blue for siblings, brown for individuals raised together from hatching, gray for newly acquainted individuals. Figure 1. Relationships between individuals (October–July). Male (dark-gray node), female (light-gray node), with bigger nodes for more sociable individuals. Two-letter combinations in the nodes are IDs of individual ravens. In the mixed group B, parent-raised individuals are marked with a red square. The relationship strength (“friendliness”) between a pair of individuals corresponds to the thickness of the edge between their nodes, with blue for siblings, brown for individuals raised together from hatching, and gray for newly acquainted individuals.

Using the information and the figures above, determine which of the statements are true or which are false.

A. To develop a stronger relationship with a sibling, individuals have to receive parental guidance.
B. Siblings will always stay closer together than with non-relatives if raised by parents.
C. Even after being introduced to each other, previously unacquainted individuals never created close relationships.
D. Individual sociability always stays the same throughout development.
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Question reproduced from IBO 2022, Theoretical Paper 2, licensed under CC BY-NC-SA 4.0 — attributed to the International Biology Olympiad. Open the full exam PDF · Community solutions (unofficial)