Unit 3 Topic 1
Name the three levels of biodiversity.
Genetic, species and ecosystem diversity.
Two species interact and both benefit. Identify this species interaction.
Mutualism.
State the complementary DNA base pairs.
A–T and C–G.
Distinguish between microevolution and macroevolution.
Microevolution = changes in allele frequencies within populations; macroevolution = larger-scale evolutionary change across species/lineages over long periods.
A population initially grows rapidly before slowing and stabilising around the carrying capacity. Identify the type and shape of population growth.
Logistic growth; S-shaped curve.
Distinguish between primary and secondary succession.
Primary succession begins where an established community/soil is absent; secondary succession occurs after disturbance where soil remains.
What is the role of DNA polymerase during DNA replication?
Adds complementary nucleotides to synthesise the new DNA strand.
A population shifts towards one extreme phenotype over several generations. Identify the type of phenotypic selection.
Directional selection.
A scientist wants to investigate how plant species change from the edge of a beach to inland dunes. Identify an appropriate sampling technique and justify it.
Belt transect (or systematic quadrats along a transect), because it samples changes in distribution along an environmental gradient.
Two species occupy the same niche and compete for exactly the same limiting resource. According to the competitive exclusion principle, predict what will eventually happen.
One species will eventually outcompete/exclude the other from that niche, unless niche differentiation occurs.
One nucleotide is deleted near the beginning of a protein-coding sequence. Identify the type of mutation and predict its likely effect on the polypeptide.
Frameshift mutation. It changes the reading frame and therefore potentially alters many downstream amino acids.
A population contains 40 AA, 50 Aa and 10 aa individuals. Calculate the frequency of allele A.
A alleles = 2(40)+50=130. Total alleles = 200. f(A) = 0.65.
A population of insects is sampled using capture–recapture. 80 are initially captured and marked. Later, 50 are captured, of which 20 are marked. Estimate the population size using the Lincoln index.
N=(80×50)/20= 200 individuals.
A top predator is removed from an ecosystem. Its prey population rapidly increases. Predict one likely effect on organisms at the next trophic level below the prey and explain why.
Increased prey abundance causes greater consumption of the organisms/resources they feed on, so the next trophic level below would decrease.
Explain how crossing over and independent assortment during meiosis produce genetic variation.
Crossing over exchanges DNA between homologous chromosomes, creating new allele combinations; independent assortment randomly distributes maternal and paternal homologues into gametes.
A river forms and separates one population into two. Gene flow becomes negligible and the populations gradually diverge. Identify the type of isolation and mode of speciation.
Geographic isolation → allopatric speciation.
Two ecosystems contain the same number of species, but Ecosystem A has similar numbers of each species while Ecosystem B is dominated by one species. Which ecosystem has greater species diversity and why?
Ecosystem A. Both have equal species richness, but A has greater evenness, producing greater overall species diversity.
An ecosystem has a GPP of 18 000 kJ m⁻² yr⁻¹ and producers lose 7 200 kJ m⁻² yr⁻¹ through respiration. Herbivores receive 1 620 kJ m⁻² yr⁻¹. Calculate NPP and the efficiency of energy transfer from producers to herbivores.
NPP = 18 000 − 7 200 = 10 800 kJ m⁻² yr⁻¹.
Efficiency = 1620÷10800×100 = 15%.
A parent with genotype Iᴬi has children with a parent of genotype Iᴮi. Calculate the probability that their child will have blood group AB.
25% (IᴬIᴮ is one of four equally likely offspring genotypes).
A conserved protein differs by 4 amino acids between Species A and B and by 16 amino acids between Species A and C. Explain which species shares the more recent common ancestor with A. If calibration data indicate 4 differences ≈ 10 million years, estimate when A and C diverged.
B is more closely related to A because it has fewer sequence differences, indicating less time since divergence. 16 differences is four times 4 differences → ≈40 million years ago.