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The diagrams show the limbs of six organisms - Edexcel - GCSE Biology - Question 3 - 2013 - Paper 1
Question 3
The diagrams show the limbs of six organisms. human lizard cat whale bat frog humerus ulna
Worked Solution & Example Answer:The diagrams show the limbs of six organisms - Edexcel - GCSE Biology - Question 3 - 2013 - Paper 1
Step 1
Describe the similarities in the limb structure of these organisms
Answer
The limbs of various organisms, such as humans, lizards, cats, whales, bats, and frogs, show a significant structural similarity that suggests a common evolutionary ancestor. Each limb contains the basic bone structures: the humerus and ulna, which are adapted for different functions based on the organism's mode of life.
For example, in humans, the forelimbs are adapted for manipulation and grasping. In contrast, the whale's forelimbs have evolved into flippers for swimming. The bat's forelimb is adapted for flight, while the frog's structure supports jumping. This phenotype diversity indicates how different environmental pressures lead to adaptations, despite the underlying similarities.
Step 2
Explain the concept of homologous structures using these diagrams
Answer
Homologous structures are anatomical features in different organisms that share a common ancestry, despite possibly serving different functions. The limb bones observed in humans, cats, bats, and whales exemplify homologous structures, where bones such as the humerus and ulna are structurally similar, reflecting their evolutionary connections. These common features signify that these organisms have diverged from a shared lineage, adapting their limbs for specific environments or functions over time. Additionally, such adaptations can give insight into evolutionary processes and the role of natural selection in shaping the diversity of life.