Questions and Answers
How may different subspecies of giraffe have evolved from a common ancestor?
No interbreeding / gene pools are separate / geographic isolation; mutation linked to different markings; selection/survival linked to different markings; adapted organisms breed; change in allele frequencies.
How did biologists conclude that six of the nine subspecies of giraffe are separate species?
Comparison of DNA base sequences; differences in six species compared to similarities in three.
Describe the changes which occur in lemming and stoat populations over time.
Lemming populations fluctuate in 4-year cycles; stoats peak after lemmings; lemming increases due to low stoat numbers; more stoats lead to decreased lemmings.
How is the movement of lemmings important for maintaining genetic variability?
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Explain how two species of lemming evolved from the original species.
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What is sympatric speciation?
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List two differences between forms T and M of Littorina saxatilis based on environmental factors.
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Study Notes
Giraffe Subspecies Evolution
- Nine giraffe subspecies developed through geographic isolation over long periods.
- Distinct skin markings among subspecies are adaptations influenced by mutation.
- Different markings provide advantages linked to survival and reproductive success.
- As a result, allele frequency changes lead to the differentiation of subspecies.
DNA Analysis and Giraffe Classification
- Mitochondrial DNA comparison among giraffe subspecies indicates species relationships.
- Six out of the nine subspecies have significant DNA differences, supporting separate species classification.
- DNA similarities suggest three remaining subspecies are closely related, classified within the same species.
Lemmings and Stoats Population Dynamics
- Lemming and stoat populations exhibit a four-year cyclical pattern.
- Stoat population peaks follow increases in lemming numbers due to lower predation pressure.
- Lemmings thrive when stoat numbers are low, leading to increased food availability for stoats.
- As stoat numbers rise, predation on lemmings intensifies, resulting in a subsequent decline of the lemming population.
Genetic Variability in Lemmings
- Isolated lemming populations exhibit limited genetic diversity due to fewer alleles and increased homozygosity.
- Migration between populations introduces new alleles, enhancing the gene pool and maintaining genetic variability.
Evolution of Two Lemming Species
- Geographical isolation after glacier melting led to the development of two distinct lemming species.
- Variation and different environmental conditions exert different selection pressures, causing divergent evolution.
- Changes in genetic constitution and allele frequencies resulted in the formation of separate species from the original population.
Sympatric Speciation
- Sympatric speciation occurs without geographic isolation, resulting in the formation of new species within the same area.
- Reproductive isolation is a key factor, disrupting interbreeding between populations.
Littorina saxatilis Snail Forms
- Littorina saxatilis has two forms based on habitat: Form T (top shore) and Form M (middle shore).
- Form T has smaller, thinner shells and lives among rock cracks with less crab predation.
- Form M has larger, thicker shells to withstand greater wave action and increased crab presence.
- Differential survival is influenced by environmental factors such as wave action and predation rates on each form of the snail.
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Description
Explore the fascinating concepts of evolution and speciation through this quiz. Understand how giraffes and their subspecies evolved from a common ancestor. This quiz will test your knowledge on the factors influencing speciation and diversification in species.