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π‘ Broad first, then fine
Scientists start with big, easily seen features and then look closer — right down to DNA — to decide how organisms are truly related.
What criteria are used to classify living organisms?
- External features (shape, size, body organisation) and internal structures (skeletons, organs, tissues).
- Mode of nutrition (autotrophic or heterotrophic), cell structure (uni/multicellular, eukaryote/prokaryote, cell wall) and ecological role (producer, consumer, decomposer).
- Reproduction (asexual and/or sexual) and genetic similarity (inherited features, studied using DNA); similar features suggest a common ancestor.
NCERT Question 3 — Observe two different animals in
Observe two different animals in your immediate environment. What features help you distinguish between them? How do these features help place them into different groups?
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NCERT Question 4 — How would a scientist justify
How would a scientist justify choosing cellular organisation as a more fundamental characteristic for the basis of classification rather than the presence of xylem and phloem?
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βΈβΆ Pause and Ponder
1. If many organisms share common features, could they also share a common ancestry? Yes — similar inherited features suggest that organisms have evolved from common ancestors.
