Evolutionary Processes, Constraints, and Speciation (Video Notes)

Vocabulary flashcards covering key terms from topics on evolutionary processes, heterozygote advantage, malaria and Plasmodium biology, limitations and constraints on evolution, speciation, and species concepts. The cards aim to reinforce definitions and relationships discussed in the video notes.

Heterozygote advantage

The heterozygote has the highest fitness among genotypes, helping to maintain genetic diversity; exemplified by sickle-cell trait in malaria regions.

Sickle cell allele (HbS)

Mutant β-globin allele caused by a point mutation; produces “sticky” hemoglobin that sickles red blood cells in low O2.

Sickle cell trait (HbB/HbS)

Heterozygous genotype; usually normal sickling and requires very low O2 to sickle.

Sickle cell disease (HbS/HbS)

Homozygous for HbS; frequent sickling leading to pain, tissue damage, and potential death if untreated.

Plasmodium

Malaria-causing parasite with a complex life cycle that infects red blood cells.

Malaria

Disease caused by Plasmodium; transmitted by mosquitoes; affects red blood cells.

Plasmodium life cycle

Complex cycle; some stages infect RBCs, Plasmodia multiply and burst from cells, triggering immune responses.

Fitness (genetic fitness)

Relative reproductive success of a genotype or phenotype in a given environment.

Homozygote

Individual with two identical alleles at a genetic locus.

Heterozygote

Individual with two different alleles at a genetic locus.

Genetic constraints

Limitations on evolution due to limited genetic variation or genetic correlations among traits.

Genetic correlations among traits

Constraints where selection on one trait affects another due to shared genetics.

Trade-offs

Limited biological resources (energy, time, materials) mean improvement in one trait often reduces another.

Historical constraints

Selection acts on existing traits; new traits must evolve from old ones, not de novo.

Chemical and physical constraints

Basic laws limit rates/natures of biochemical processes and physical characteristics of materials.

Variable selective conditions

Changing environments cause inconsistent patterns of selection; adaptations cannot perfectly track changes.

Speciation

Process by which new species arise.

Morphological species concept

Species defined by phenotype; practical but can be misled by convergent evolution.

Biological species concept

Species defined by reproductive isolation and potential to interbreed and produce fertile offspring.

Phylogenetic species concept

Species defined by sufficient separation on a phylogenetic tree (monophyly and diagnostic differences).

Linnean taxonomy

Classification system developed by Linnaeus using binomial nomenclature and hierarchical groups.

Dusky Seaside Sparrow (example)

Used to illustrate how different species concepts apply to real populations (morphological, biological, phylogenetic).