The availability of fresh pasture growth in spring makes this a prime lambing season. However, a secondary lambing also occurs in Autumn. Pastures at this time of year are good, but not as much as Spring.

Looking at the results of the Experiment 1 (Spring vs Autumn):

Table 1 shows the live and carcass weight

Table 2 shows placental morphology

Table 3 shows muscle weights

Table 4 shows the myofibre numbers and cross-sectional area

Which of the following responses best describes the effects of season on foetal growth?

Question

The availability of fresh pasture growth in spring makes this a prime lambing season. However, a secondary lambing also occurs in Autumn. Pastures at this time of year are good, but not as much as Spring.

Looking at the results of the Experiment 1 (Spring vs Autumn):

Table 1 shows the live and carcass weight

Table 2 shows placental morphology

Table 3 shows muscle weights

Table 4 shows the myofibre numbers and cross-sectional area

Which of the following responses best describes the effects of season on foetal growth?

BlackTom AI · Accepted Answer

The question asks how season affects foetal growth, referencing Results from Experiment 1 (Spring vs Autumn) and multiple data tables.
Option 1: 'Spring lambs were born with higher placental mass and increased hypertrophy in some muscles' — This option ties together two plausible findings: larger placental mass in spring and evidence of hypertrophy (increased muscle cross-sectional area or hypertrophic growth) in some muscles. If the tables show greater placental mass in spring and at least some muscles with hypertrophy, this option correctly reflects a season-related enhancement in foetal growth biology.
Option 2: 'Season did not impact foetal muscle fibre hyperplasia' — This claims no effect of season on the number of muscle fibers formed (hyperplasia). However, foetal muscle development often involves both hyperplasia and hypertrophy, and if the experiment reports differences in placental mass or in muscle growth, this statement would be inconsistent with those findings. The presence of changes in placental morphology or hypertrophy in some muscles would undermine this blanket claim.
Option 3: 'The reduced foetal size in Autumn lambs was due to a reduction in the gravid uterus weight' — This suggests Autumn foetuses are smaller because the gravid uterus weight decreased, implying a causal link from maternal/fetal size to uterine size. Unless the data explicitly show autumn fetal size reduction connected to gravid uterus weight, this is a speculative explanation. If the tables indicate other determinants (placental changes, muscle development) rather than uterine weight as the driver, this option would be less supported.
Option 4: 'Spring lambs had a placental insufficiency due to placental hyperplasia (enlargement) with no corresponding improvement in foetal growth' — Placental hyperplasia usually denotes placental enlargement, but the phrase 'placental insufficiency' contradicts the idea that a larger placenta should support growth. If the data instead show that spring placentas are larger and associated with improved or at least preserved foetal growth (e.g., increased placental mass with hypertrophy), this option would be inconsistent with the observed positive relationship between placental size and foetal growth.
In sum, each option hinges on specific interpretations of the tables: placental mass, muscle hypertrophy, and the relationship between placental changes and foetal outcomes. The most directly supported statement, given a typical positive link between placental investment and foetal/muscle growth during spring, is the first option. The remaining choices introduce causal claims or interpretations that would require data to support them, but do not align with a straightforward description of spring advantages observed in the experiment.

MERGE_2025_0317 Tutorial 1: muscle fibre dynamics and animal growth

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