krit.club logo

Evolution and Biodiversity - Classification of Biodiversity

Grade 11IBBiology

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

•

The Binomial System: Species are identified by a two-part name consisting of the GenusGenus (capitalized) and speciesspecies (lowercase), both written in italics or underlined, such as HomoHomo sapienssapiens.

•

Hierarchy of Taxa: Organisms are classified into a hierarchy of taxa: Domain, Kingdom, Phylum, Class, Order, Family, Genus, and Species. A mnemonic is 'Dear King Philip Came Over For Good Soup'.

•

The Three Domains: All organisms are classified into three domains: ArchaeaArchaea (extremophiles), BacteriaBacteria (true bacteria), and EukaryotaEukaryota (organisms with a membrane-bound nucleus).

•

Plant Phyla: Major phyla include BryophytaBryophyta (no vascular tissue, e.g., mosses), FilicinophytaFilicinophyta (vascular, spores, e.g., ferns), ConiferophytaConiferophyta (seeds in cones, e.g., pines), and AngiospermophytaAngiospermophyta (flowers and fruits).

•

Animal Phyla: Key invertebrate phyla include PoriferaPorifera (no symmetry, pores), CnidariaCnidaria (radial symmetry, stinging cells), PlatyhelminthaPlatyhelmintha (bilateral, flat, no heart), AnnelidaAnnelida (segmented, bilateral), MolluscaMollusca (mantle, muscular foot), and ArthropodaArthropoda (exoskeleton, jointed appendages).

•

Chordata: A phylum characterized by having a notochord at some stage of development. Includes sub-classes like AmphibiaAmphibia, ReptiliaReptilia, AvesAves (birds), and MammaliaMammalia.

•

Natural Classification: Groups together species that share a common ancestor. This allows for the prediction of characteristics within a group and helps in the identification of new species.

•

Reclassification: Taxonomists may reclassify groups of species when new evidence (often molecular, such as rRNArRNA sequences) suggests a different evolutionary pathway.

📐Formulae

D=N(N−1)∑n(n−1)D = \frac{N(N-1)}{\sum n(n-1)}

T=D2RT = \frac{D}{2R}

Percent Sequence Divergence=Number of base differencesTotal number of bases×100\text{Percent Sequence Divergence} = \frac{\text{Number of base differences}}{\text{Total number of bases}} \times 100

💡Examples

Problem 1:

Calculate the Simpson's Diversity Index (DD) for a sample containing three species: Species A (n1=10n_1 = 10), Species B (n2=5n_2 = 5), and Species C (n3=15n_3 = 15).

Solution:

N=10+5+15=30N = 10 + 5 + 15 = 30 ∑n(n−1)=10(9)+5(4)+15(14)=90+20+210=320\sum n(n-1) = 10(9) + 5(4) + 15(14) = 90 + 20 + 210 = 320 D=30(29)320=870320≈2.72D = \frac{30(29)}{320} = \frac{870}{320} \approx 2.72

Explanation:

Simpson's Diversity Index measures the probability that two individuals randomly selected from a sample will belong to the same species. A higher value usually indicates greater biodiversity.

Problem 2:

Identify the plant phylum: A plant has vascular tissue, does not produce flowers, and reproduces via seeds found in woody cones.

Solution:

ConiferophytaConiferophyta

Explanation:

The presence of vascular tissue eliminates BryophytaBryophyta. The use of seeds rather than spores eliminates FilicinophytaFilicinophyta. The presence of cones and lack of flowers identifies it as ConiferophytaConiferophyta.

Problem 3:

Two species show a 5%5\% difference in their DNADNA sequences. If the estimated mutation rate (RR) is 1%1\% per million years, calculate the time (TT) since they shared a common ancestor.

Solution:

T=52×1=2.5 million yearsT = \frac{5}{2 \times 1} = 2.5 \text{ million years}

Explanation:

Using the molecular clock hypothesis, the divergence time is calculated by dividing the total divergence by twice the mutation rate (to account for mutations accumulating in both lineages).