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Secondary 3 Biology Evolution Diversity Quiz
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Secondary 3 Biology Quiz - Evolution Diversity (Answer Key)
Total Marks: 40
Section A: Multiple Choice Answers
1. B
Explanation: Variation refers to differences between individuals of the same species. A refers to diversity between species. C refers to acquired characteristics (not heritable). D is too narrow; variation includes recombination, not just mutation.
2. C
Explanation: This is the core mechanism of natural selection. A is incorrect (Lamarckian view). B is incorrect (reproduction rate isn't the primary driver here; survival is). D is incorrect (organisms do not choose to change phenotype).
3. C
Explanation: Discontinuous variation has distinct categories with no intermediates (e.g., blood groups). Height, weight, and leaf length are continuous variations.
4. B
Explanation: Mutations are random and occur before exposure to the antibiotic. The antibiotic selects for the existing resistant mutants. A, C, and D are incorrect mechanisms.
5. A
Explanation: The correct hierarchy is Kingdom, Phylum, Class, Order, Family, Genus, Species.
Section B: Structured Answers
6.
(a) Homologous structures [1]
(b) They share a similar bone structure/layout [1], suggesting they inherited this structure from a common ancestor [1], but adapted for different functions (grasping, flying, swimming) due to different environmental pressures. [1] (Max 2 marks)
7.
(a) Individuals within a population show differences in characteristics. [1]
(b) Individuals compete for limited resources (food, space, mates). [1]
8.
(a) Light-coloured moths [1]
(b)
- Tree trunks became blackened by soot, making light moths visible to predators and dark moths camouflaged. [1]
- Dark moths were less likely to be eaten by birds (higher survival rate). [1]
- Dark moths survived to reproduce and passed the allele for dark colour to their offspring. [1]
(Note: Must mention survival, reproduction, and inheritance of alleles.)
9.
(a) Blood group / Eye colour (if simplified) / Presence of attached earlobes [1] (Must be purely genetic)
(b) Height / Weight / Skin colour [1]
(c) Genetic variation ensures that some individuals may possess traits that allow them to survive new environmental conditions (e.g., disease, climate change) [1]. If all individuals were identical, a single change could wipe out the entire population. [1]
10.
(a) Canis [1]
(b) They share the same Genus (Canis) and many higher taxonomic groups, indicating a recent common ancestor. [1]
(c) Common names vary by language/region and can be ambiguous (e.g., "starfish" is not a fish). Binomial names are universal and precise. [1]
11.
(a)
- Random mutations occur in bacteria, some conferring resistance to antibiotics. [1]
- When antibiotics are used, non-resistant bacteria die, but resistant bacteria survive. [1]
- Resistant bacteria reproduce and pass the resistance gene to offspring, increasing the proportion of resistant bacteria in the population. [1]
(b) Sterilise equipment / Wash hands regularly / Isolate infected patients / Use antibiotics only when necessary. [1] (Any one valid measure)
12.
(a) Natural selection is driven by environmental pressures and survival [1], whereas artificial selection is driven by human choice for desired traits. [1]
(b) Higher yield / Disease resistance / Drought tolerance / Larger fruit size. [1]
13.
(a) Continuous variation [1]
(b) It is controlled by many genes (polygenic) and/or influenced by environmental factors. [1]
14.
(a) The preserved remains or traces of an organism from the past. [1]
(b) Fossil record is incomplete (not all organisms fossilise) [1] OR Soft tissues rarely fossilise [1] OR It is difficult to determine exact colour/behaviour from fossils.
15.
(a) Adaptive radiation (or Speciation) [1]
(b) They feed on different food sources (seeds vs. insects), so they do not compete for the same food resource. [1]
Section C: Free Response Answers
16.
Mutations are changes in the DNA sequence [1]. They create new alleles/variants of genes, which introduces new genetic variation into a population. This variation is the raw material upon which natural selection acts. [1]
17.
In biology, "fitness" does not mean physical strength. It refers to an organism's ability to survive in its specific environment [1] and successfully reproduce to pass its genes to the next generation. [1]
18.
Bacteria reproduce very rapidly (short generation time) [1]. When exposed to antibiotics, the selection pressure is strong, killing non-resistant strains quickly [1]. The resistant survivors reproduce exponentially, leading to a dominant resistant population in a short time (years/decades) compared to larger organisms (millions of years). [1]
19.
Continuous Variation:
- Shows a range of values with no distinct categories.
- Usually controlled by many genes and environment.
- Example: Height, Weight. [1.5 marks for description + example]
Discontinuous Variation: - Shows distinct categories with no intermediates.
- Controlled by one or a few genes, little environmental influence.
- Example: Blood group, Tongue rolling. [1.5 marks for description + example]
20.
- Biodiversity ensures ecosystem stability/resilience. If one species declines, others can fill its niche. [1]
- It provides resources for humans (medicine, food, materials). [1]
- It maintains ecological balance (e.g., pollination, nutrient cycling). [1]
(Accept other valid ecological or economic reasons.)