HWE & Speciations

BIS 2D 2nd Midterm

In a population of 100 otters in HWE, 36 have light brown fur (recessive). What is the frequency of the dominant allele?

b) 0.4 (q²=0.36 → q=0.6; p=1-0.6=0.4)

A gene has alleles A (p=0.3) and a (q=0.7). What is the expected frequency of heterozygotes?

c) 0.42 (2pq=2×0.3×0.7)

Which HWE assumption is violated if a population has excess homozygotes?

b) Random mating (Inbreeding increases homozygosity)

A population with genotype frequencies AA=0.64, Aa=0.20, aa=0.16 is likely experiencing:

a) Inbreeding (Excess homozygotes)

Genetic drift has the strongest effect in:

b) Small populations (Fewer alleles to buffer randomness)

Founder effect vs. bottleneck:

a) Both reduce genetic diversity, but bottleneck affects the entire species (Founder leaves source population intact)

If 16% of a population has curly horns (recessive), what is the frequency of the curly allele?

b) 0.4 (√0.16)

The Biological Species Concept fails for:

a) Asexual bacteria (No interbreeding)

Rank from broadest to narrowest:

b) Reproductive barrier → Prezygotic → Behavioral → Song differences (Correct hierarchy)

Allopatric speciation via vicariance requires:

a) Geographic separation (e.g., mountain formation)

Sympatric speciation often involves:

b) Ecological/behavioral divergence (e.g., apple maggot flies)

Hybrid embryos dying after 1 day is:

a) Postzygotic barrier (reduced viability)

Pollinator specialization speeds speciation by:

a) Reducing gene flow (Behavioral isolation)

Poor dispersers speciate faster because:

a) Smaller populations isolate easily (Less gene flow)

Adaptive radiation example:

a) Hawaiian honeycreepers (Rapid niche diversification)

Monophyletic groups include:

a) An ancestor + all descendants (Clade definition)

Bat wings and bird wings are:

a) Analogous (Convergent evolution)

Shared derived traits indicate:

a) Common ancestry (Homology)

HWE violation with excess heterozygotes suggests:

a) Outbreeding or selection (Heterozygote advantage)

X-linked hemophilia frequency in males (q) is 0.01. Expected frequency in females?

b) 0.0001 (q²=0.01²)