Zoology 2024 Paper II 50 marks Describe

Q4

(a) Describe the stages of human evolution and mention the major hominid forms giving their time of origin. (20 marks) (b) What is Hardy-Weinberg law? How is gene frequency changed by mutation and genetic drift in populations? (15 marks) (c) What is the difference between systematics and taxonomy? Differentiate between classical and molecular taxonomy with the tools used. (15 marks)

हिंदी में प्रश्न पढ़ें

(a) मानव उद्विकास के चरणों का वर्णन कीजिए तथा मुख्य होमिनिड अवस्थाओं (फॉर्म) को उनकी उत्पत्ति के काल को दर्शाते हुए उल्लिखित कीजिए। (20 अंक) (b) हार्डी-वीनबर्ग नियम क्या है? समष्टि में उत्परिवर्तन तथा आनुवंशिक विचलन (जेनेटिक ड्रिफ्ट) से जीन आवृत्ति कैसे परिवर्तित होती है? (15 अंक) (c) वर्गीकरण-विज्ञान तथा वर्गिकी में क्या अंतर है? चिरप्रतिष्ठित एवं आणविक वर्गिकी में प्रयुक्त उपकरणों सहित अंतर कीजिए। (15 अंक)

Evaluate your answer to this question → See all 2024 Zoology questions

Directive word: Describe

This question asks you to describe. The directive word signals the depth of analysis expected, the structure of your answer, and the weight of evidence you must bring.

See our UPSC directive words guide for a full breakdown of how to respond to each command word.

How this answer will be evaluated

Approach

The directive 'describe' demands detailed, sequential exposition with factual precision. Allocate approximately 40% of effort to part (a) given its 20 marks—covering primate ancestors through Homo sapiens with geological epochs; 30% each to (b) and (c). Structure: brief introduction on evolutionary principles, then three dedicated sections for each sub-part, with diagrams for (a) and (b), concluding with synthesis on modern evolutionary biology's integrative nature.

Key points expected

Part (a): Chronological progression from Dryopithecus/Ramapithecus through Australopithecus, Homo habilis, H. erectus, H. neanderthalensis to H. sapiens with correct geological timeframes (Miocene to Pleistocene)
Part (a): Key morphological transitions—bipedalism, cranial capacity expansion, dental reduction, tool use correlation with brain development
Part (b): Hardy-Weinberg equilibrium equation (p² + 2pq + q² = 1) with assumptions (large population, random mating, no selection/mutation/migration)
Part (b): Mutation as raw material changing allele frequencies (directional/non-directional) versus genetic drift as random sampling error, especially in small populations including bottleneck and founder effects
Part (c): Systematics as broader science of biological diversity and relationships versus taxonomy as classification practice; classical taxonomy (morphological/anatomical/embryological) versus molecular taxonomy (DNA sequencing, PCR, RFLP, DNA barcoding, phylogenomics)
Part (c): Specific tools—classical: herbarium, museum specimens, dichotomous keys; molecular: BLAST, ClustalW, mitochondrial DNA, ribosomal RNA sequencing

Evaluation rubric

Dimension	Weight	Max marks	Excellent	Average	Poor
Concept correctness	22%	11	For (a): accurate geological dating (e.g., H. erectus 1.8 mya–300 kya, H. sapiens ~300 kya–present) and correct phylogenetic relationships; for (b): mathematically correct H-W equilibrium with all five assumptions stated; for (c): precise distinction between systematics (evolutionary relationships) and taxonomy (naming/classification), with no conflation of terms	Generally correct chronology in (a) but minor dating errors; H-W equation present but assumptions incomplete; systematics/taxonomy distinction vague or reversed; some molecular tools misnamed	Major chronological confusion (e.g., placing Neanderthals before H. erectus); H-W equation wrong or missing; fundamental misunderstanding that taxonomy encompasses systematics; incorrect tool identification
Diagram / labelling	18%	9	For (a): clear phylogenetic tree/hominid timeline with branching patterns, cranial capacity trends, and geographic distribution; for (b): allele frequency change graphs showing drift in small vs. large populations; all diagrams fully labelled with axes, time scales, and key morphological features	One adequate diagram (typically for part a) with partial labelling; OR two diagrams with significant missing labels; no diagram for part (b) genetic drift visualization	No diagrams or extremely crude sketches; diagrams present but unlabelled or misleading (e.g., linear ladder instead of branching tree for hominid evolution)
Examples & nomenclature	20%	10	For (a): specific fossil specimens (e.g., Lucy/Australopithecus afarensis, Java Man/H. erectus erectus, Peking Man, Cro-Magnon); Indian context where relevant (e.g., Hathnora H. erectus, Narmada Man); for (b): concrete drift examples (e.g., Amish Ellis-van Creveld syndrome, Northern elephant seal bottleneck); for (c): specific molecular markers (16S rRNA, COI gene for barcoding)	Generic hominid names without species designation; missing specific fossil specimens; drift mentioned without real examples; tools listed without specification of molecular markers	Incorrect nomenclature (e.g., 'Homo sapiens neanderthalensis' as modern human ancestor); no examples for drift; classical and molecular tools not distinguished or entirely absent
Process explanation	22%	11	For (a): clear explanation of selective pressures driving each transition (e.g., savanna hypothesis for bipedalism, climate variability for encephalization); for (b): step-by-step mechanism of how mutation introduces new alleles versus how drift randomly fixes alleles irrespective of fitness; for (c): logical comparison showing how molecular data resolves cryptic species and convergent evolution problems of classical taxonomy	Descriptive list of features without causal explanation; mutation and drift distinguished but mechanisms unclear; comparison of taxonomic approaches superficial without problem-solving emphasis	No causal mechanisms; conflates mutation and drift as both 'random' without distinguishing source of variation versus sampling error; no comparison structure in part (c)
Evolutionary / applied context	18%	9	Synthesizes across parts: connects human evolution to understanding population genetics (conservation of endangered species, genetic diversity in isolated human populations); notes how molecular systematics revised hominid phylogeny (e.g., molecular clock placing human-chimp divergence, revised Homo taxonomy); mentions applied relevance—forensic DNA, conservation genetics, disease susceptibility in isolated populations	Brief mention of conservation or medicine without integration; no synthesis across the three sub-parts; applied context limited to generic statements	No applied or contemporary relevance; answer ends abruptly with part (c) definitions; complete failure to connect classical and molecular approaches to resolving human evolutionary relationships

Practice this exact question

Write your answer, then get a detailed evaluation from our AI trained on UPSC's answer-writing standards. Free first evaluation — no signup needed to start.

Evaluate my answer →