Amys Lectures Flashcards
(22 cards)
What is phenotypic plasticity?
Phenotypic plasticity is the environmentally induced variation in phenotype within a single genotype. For example, some plants can alter their leaf shape depending on light availability.
How does phenotypic plasticity differ from local adaptation?
Phenotypic plasticity involves flexible responses within an organism’s lifetime to environmental variation, while local adaptation refers to fixed genetic differences that evolve over generations in response to specific environmental pressures.
Under what conditions is phenotypic plasticity likely to evolve?
Plasticity is favoured in heterogeneous environments or metapopulations, where environmental conditions vary spatially or temporally.
What are the costs and limits of phenotypic plasticity?
Costs include the energy and resources required to maintain plastic traits. Limits may arise if environmental cues are unreliable or if genetic constraints prevent an effective response.
How might phenotypic plasticity contribute to the success of invasive species?
It allows organisms to thrive across a range of environmental conditions, enhancing their ability to colonise new habitats. For example, invasive plants often exhibit high plasticity in growth and reproductive strategies.
What is a point mutation and what is its evolutionary significance?
A point mutation is a base pair substitution in the DNA sequence, often due to errors in replication or repair. It can create new alleles, which may be beneficial, neutral, or deleterious.
Describe gene duplication and its evolutionary role.
Gene duplication involves copying a short DNA stretch, typically through unequal crossing over. The extra copy can acquire new functions (neofunctionalisation) or divide existing functions (subfunctionalisation), contributing to evolutionary innovation.
What is polyploidy and how can it impact evolution?
Polyploidy is the addition of an entire set of chromosomes, usually due to meiotic errors. It can lead to instant speciation, particularly in plants.
What types of diversity can be found within a genome?
Diversity includes single nucleotide polymorphisms, gene duplications, structural variations, and mobile genetic elements. These differences can affect regulation, function, and adaptability.
What are mobile genetic elements and what role do they play in evolution?
Mobile elements (e.g., transposons) are DNA sequences that can move within the genome. They may disrupt genes or regulatory regions (maladaptive), but can also contribute to novel gene regulation or innovation.
What defenses do organisms have against mobile genetic elements?
Common defenses include DNA methylation and RNA interference, which suppress the movement or expression of these elements.
Why is gene duplication important for evolution?
It provides raw genetic material for evolutionary change. Duplicated genes can evolve new functions or be maintained through subfunctionalisation.
How can we identify loci of adaptation in genomes?
By comparing populations or species and looking for signatures of selection, such as high differentiation (F_ST) or selective sweeps around beneficial alleles.
What is the relationship between humans and apes?
Humans share a common ancestor with chimpanzees and gorillas, with the human-chimpanzee split occurring ~5.4 million years ago.
What are key genetic differences between humans, chimpanzees, and gorillas?
These include both small-scale (e.g., SNPs) and large-scale (e.g., gene duplications) changes, particularly in genes related to brain development, language, and tool use.
Which traits distinguish humans from other apes, and what is their evolutionary significance?
Traits like complex language and tool-making are unique to humans and likely conferred survival advantages, aiding in the dominance of Homo sapiens over other hominins.
How do influenza viruses evolve to evade the immune system?
Through antigenic drift (point mutations in surface proteins) and antigenic shift (genetic reassortment), allowing them to avoid immune recognition.
How can evolutionary theory help predict future pathogen strains?
By understanding mutation rates, selection pressures, and fitness trade-offs, researchers can anticipate which strains are most likely to persist and inform vaccine design.
What is the trade-off hypothesis in pathogen evolution?
It suggests that pathogens balance virulence and transmission; higher virulence may be favoured if it increases transmission, but too much virulence can kill hosts too quickly.
Why might modern humans be maladapted to current environments?
Our environments (diet, activity levels, etc.) have changed rapidly due to cultural evolution, while biological evolution is slower. This mismatch may underlie diseases of civilisation.
How can evolutionary theory explain the rise in conditions like myopia and obesity?
These conditions may result from gene-environment interactions, where once-adaptive traits are now maladaptive (e.g., a thrifty genotype promoting fat storage in a calorie-rich world).
Are we selecting for disease in modern populations?
In some cases, yes. Reduced mortality due to medical care allows alleles associated with disease (e.g., Type 2 diabetes risk genes) to persist and even increase in frequency.
