NSSCAS Biology Grade 12 AS Level Study Guide: Classification, Biodiversity, Conservation & Microscopy

Comprehensive practice flashcards for NSSCAS Biology AS Level covering classification systems, species concepts, biodiversity indices, sampling techniques, conservation strategies, microscopy specifications, and metric calculations.

What is the biological definition of classification, and what four critical functions does it fulfill?

Classification is the systematic grouping of organisms based on structural, physiological, and evolutionary similarities. Its four critical functions are:

1. Identification: Allows systematic identification and naming of newly discovered species.
2. Cataloging: Enables tracking and recording of global species diversity.
3. International Communication: Provides a single, universally accepted binomial name, avoiding regional confusion.
4. Simplification: Reduces the complexity of studying millions of distinct organisms into organized groups.

Who devised the binomial system of nomenclature, and what are its naming and formatting rules?

Devised by Carolus Linnaeus, it assigns a two-part Latin name: the Generic Name (Genus), which starts with a capital letter, and the Specific Epithet (Species), which starts with a lowercase letter. Exam formatting rules: • When typed: Must be in italics (e.g., Homo sapiens). • When handwritten: The Genus and species names must be underlined separately (e.g., Homo sapiens).

What is the sequence of the taxonomic hierarchy from broadest to most specific taxon?

Domain → Kingdom → Phylum → Class → Order → Family → Genus → Species.

What are the Three Domains and Five Kingdoms of living organisms, and where do viruses fit?

• Three Domains: Archaea, Bacteria, and Eukarya. • Five Kingdoms: Monera (Prokaryotae), Protoctista, Fungi, Plantae, and Animalia. • Viruses: Non-cellular and excluded from the five kingdoms.

What is natural classification, and how do homologous and analogous features differ?

Natural classification groups organisms based on shared evolutionary ancestry and lineage, relying exclusively on homologous features. • Homologous Features: Anatomical structures sharing a common evolutionary origin, even if modified for different functions (e.g., pentadactyl limb in humans, horses, bats, and whales). • Analogous Features: Structures performing similar functions that evolved independently from distinct ancestral origins (e.g., wings of birds vs. wings of insects); excluded from natural classification.

What three rules must be followed when constructing a dichotomous key?

1. Use clear structural features.
2. Avoid subjective terms like 'large' or 'small'.
3. For $N$ organisms, use exactly $N - 1$ pairs of statements.

What is the Biological Species Concept, and what are its key limitations?

It defines a species as a group of naturally interbreeding organisms producing viable, fertile offspring. Its limitation is that it cannot be applied to fossils, extinct species, or asexual organisms.

How do the Morphological, Ecological, and Behavioural Species Concepts define a species?

• Morphological Concept: Groups organisms based on shared, observable physical and anatomical structures (used in field identification and fossil taxonomy). • Ecological Concept: Defines a species by its unique ecological niche and resource utilization (focuses on functional roles and resource partitioning). • Behavioural Concept: Groups organisms by species-specific behavioral patterns, such as courtship calls or mating displays that prevent interbreeding between sympatric groups.

How are an ecosystem and an ecological niche defined?

• Ecosystem: A self-sustaining community of living organisms (biotic factors) interacting with each other and their physical environment (abiotic factors). • Niche: The unique functional role and position an organism occupies within its ecosystem, including habitat, activity patterns, and resource usage.

What are the three levels of biodiversity?

1. Ecosystem Diversity: Range of varied habitats, communities, and ecological processes.
2. Species Diversity: Combines Species Richness (total number of different species) and Species Evenness (relative abundance of each species).
3. Genetic Diversity: The variety of alleles and genes present within a species' gene pool.

What is the formula and interpretation for Simpson's Index of Diversity ($D$)?

Formula: $D = 1 - \sum \left( \frac{n}{N} \right)^2$ where $n$ = total number of organisms of a single species and $N$ = total number of organisms of ALL species. Interpretation: $D$ ranges from $0$ to $1$. Values close to $1$ indicate high biodiversity, complex food webs, and high ecosystem stability.

What quantitative formulas are used with frame quadrat sampling to measure Species Density and Frequency?

• $\text{Species Density} = \frac{\text{Total Count}}{\text{Total Area}\,(\text{m}^2)}$ • $\text{Frequency}\,(\%) = \left( \frac{\text{Quadrats Present}}{\text{Total Quadrats}} \right) \times 100$

What is the difference in purpose between a line transect and a belt transect?

• Line Transect: A marked line across an environmental gradient that records species touching the line at fixed intervals to measure species distribution. • Belt Transect: Quadrats placed at regular intervals along a transect line to measure changes in both species distribution and abundance.

What formula is used in the Mark-Release-Recapture method to estimate population size?

The Lincoln Index: $N = \frac{n_1 \times n_2}{n_3}$ where $n_1$ = 1st capture count, $n_2$ = 2nd capture count, and $n_3$ = number of marked individuals recaptured.

What is the step-by-step sequence of aquatic eutrophication?

Fertilizer Runoff (Nitrates/Phosphates) → Algal Bloom → Light Blocked → Submerged Plants Die → Aerobic Bacteria Multiply → Oxygen Depletion → Aquatic Fauna Dies of Suffocation.

What is the difference between bioaccumulation and biomagnification?

Bioaccumulation is the buildup of non-biodegradable toxins (e.g., DDT, mercury) in the fat tissues of individual organisms (such as producers), whereas biomagnification is the progressive increase of these toxins to lethal concentrations at apex trophic levels across a food chain.

What are the primary roles of Zoos, Botanic Gardens, National/Marine Parks, Frozen Zoos, and Seed Banks?

• Zoos (Ex-situ, Animals): Captive breeding programs, reintroduction, public education. • Botanic Gardens (Ex-situ, Plants): Propagates endangered flora, research, species restoration. • National / Marine Parks (In-situ, Ecosystems): Protects natural habitats, intact food webs, and breeding grounds. • Frozen Zoos (Ex-situ, Genetic): Cryogenic storage of sperm, eggs, tissue, and DNA in liquid nitrogen. • Seed Banks (Ex-situ, Plants): Stores dried, frozen seeds long-term to guard against extinction.

What population control methods can be used to prevent overgrazing, and what is a non-lethal alternative?

Culling selectively removes overpopulated species to prevent overgrazing. Contraception (such as immunocontraceptive vaccines in female elephants) offers a non-lethal alternative.

Why are alien invasive species detrimental to ecosystems, and what are three examples of habitat restoration?

Alien invasive species lack local predators, outcompete native flora/fauna, reduce water availability, and degrade agricultural pastures. Habitat restoration examples:

1. Namaqualand mining soil rehabilitation
2. Opuwo reforestation in Namibia
3. Oshana floodplain wetland restoration

What are the definitions of magnification and resolution in microscopy?

• Magnification: Number of times larger an image appears relative to its real size. • Resolution: Ability to distinguish between two close points (inversely proportional to wavelength).

How do Light Microscopes (LM) and Electron Microscopes (EM) compare in radiation source, focusing lens, resolving power, and maximum useful magnification?

• Radiation Source: LM uses visible light rays ($\sim 400\text{--}700\,\text{nm}$); EM uses a high-velocity electron beam ($\sim 0.005\,\text{nm}$). • Focusing Lens: LM uses glass lenses; EM uses electromagnetic coils. • Resolving Power: LM is $200\,\text{nm}$ ($0.2\,\mu\text{m}$); EM is $0.5\,\text{nm}$. • Max Useful Magnification: LM is $\times 1000$ to $\times 1500$; EM is up to $\times 1{,}000{,}000$.

Why can ribosomes ($20\,\text{nm}$) be resolved by an Electron Microscope (EM) but not a Light Microscope (LM)?

The EM uses an electron beam with an extremely short wavelength ($0.005\,\text{nm}$), providing a much higher resolution ($0.5\,\text{nm}$) than an LM ($200\,\text{nm}$). Structures smaller than $200\,\text{nm}$ cannot be distinguished separately under an LM.

What are the metric conversion factors between millimeters ($\text{mm}$), micrometers ($\mu\text{m}$), and nanometers ($\text{nm}$)?

• $1\,\text{mm} = 1{,}000\,\mu\text{m}$ • $1\,\mu\text{m} = 1{,}000\,\text{nm}$ • $\text{mm} \rightarrow \mu\text{m}$: Multiply by $1{,}000$ • $\mu\text{m} \rightarrow \text{nm}$: Multiply by $1{,}000$ • $\mu\text{m} \rightarrow \text{mm}$: Divide by $1{,}000$

What is the formula for calculating Distance per Eyepiece Unit (EPU)?

$$\text{Distance per Eyepiece Unit (EPU)}\,(\mu\text{m}) = \frac{\text{Stage Divisions} \times \text{Size of 1 Stage Division}\,(\mu\text{m})}{\text{Eyepiece Graticule Divisions}}$$

If 80 eyepiece graticule units match 20 stage divisions, and 1 stage division equals $10\,\mu\text{m}$, what is the distance of 1 EPU?

$$\text{1 EPU} = \frac{20 \times 10}{80} = 2.5\,\mu\text{m/EPU}$$

What are the three magnification formulas derived from the triangle ($I = A \times M$), and what is the golden rule for calculations?

• Magnification: $M = \frac{I}{A}$ • Actual Size: $A = \frac{I}{M}$ • Image Size: $I = A \times M$ Golden Rule for Calculations: Always measure length ($I$) with a ruler in $\text{mm}$, then multiply by $1{,}000$ to convert to $\mu\text{m}$ before dividing by $M$ or $A$.