Genetics and Evolution Quiz

Microevolution to Speciation

• Microevolution is about change within a species over a short time, impacting a species' gene pool.
• Macroevolution focuses on the evolution of the type and number of species over a longer time.
• Macroevolution explains how different species arise and why they differ, even with a common ancestor.

Problems with Darwin's Model

• Darwin's model of natural selection assumed traits were blended in offspring, which reduces variation.
• Blending inheritance destroys existing variations.
• Darwin's assumptions worked better with the understanding of genetics.

Genetics Rescuing Darwin

• Genetics shows that variation is maintained, not removed, by natural selection.
• Variations that are heritable lead to more successful organisms, which in turn are better adapted.

Mutation and Heredity

• Mutation is the source of new variation by changing DNA
• Mutations provide novelty that selection can act on
• Not all mutations have phenotypic effects; some are silent, some may cause a change in the protein, and some can halt the protein production.

Mendelian Genetics

• Mendelian genetics show that variation is preserved through generations.
• Mendel's theory works well with natural selection to show how traits form from genes, and how population size strongly promotes mutation

Evolution in the Era of Genetics: 1. Mutation

• There are different types of mutation: silent, missense, nonsense.
• Silent mutations don't affect protein function.
• Missense mutations change amino acid sequences that lead to variations in phenotype.
• Nonsense mutations stop production of proteins, dramatically impacting the organism.

Evolution in the Era of Genetics: 2. Mutation and Heredity

• DNA is underpinned by genes
• Genes express phenotype
• Mutations in genetic codes influence phenotype

Other Mutational Events

• Macromutations: Large-scale genetic changes affecting many genes
• Gene duplication: Creates extra copies of genes, which may lead to novel genes
• Endosymbiosis: Explains the evolution of mitochondria and chloroplasts in eukaryotes.
• Change in karyotypes: Modification in chromosome numbers.
• Polyploidy: Duplication of the entire genome.

Evolution and Mutations: Small or Large Effects?

• Which types of mutations are crucial for evolution?
• Normal mutations are small variations.
• Big mutations cause negative physiological reactions and can thus be detrimental.
• Natural selection is more effective on smaller-effect mutations.

Natural Selection and Genetic Variation

• Natural selection can only make use of existing genetic variation.
• Some species have high genetic variation, some have little, which influences how much change can happen

Evolution and Population Size

• Population size is essential for evolution, because mutations happen in every generation.
• Small populations, due to fewer opportunities for reproductions and mates, result in fewer opportunities for changes, which causes slower evolution.

The Influence of Population Size on Mutation and Adaptation

• Every time meiosis happens, there are some mutations
• The number of mutations rises with age in males
• Large populations have more meiotic events and more chances for mutations
• Small populations have fewer opportunities, meaning slower evolution
• HIV is an example of how a small population size can lead to rapid evolution of resistance

Variation in Gene Expression

• Genetic variation in gene expression affects phenotype
• Gene expression impacts which proteins are produced, when they are produced, and where they're produced influencing phenotypes in development stages and in different tissues.

Impact of Dominance and Rate of Adaptation

• Dominant alleles give phenotypes in heterozygotes, and can be selected for quickly even when rare.
• Recessive alleles need both copies of a gene to be expressed. They take longer to be selected for.
• Evolution is strongly biased toward dominant mutations, which are very common.

Quantitative/Complex Traits

• Traits show variation in phenotypic characteristics.
• Genotype determines the expression of traits.
• Traits are influenced by the sum of many genetic loci interactions.
• Heritability of traits can differ across generations because environments are dynamic

Modeling Selection on Mendelian Loci

• Understanding the interplay between genetics, natural selection, and the environment to predict and understand evolution
• Traits are usually controlled by multiple genes in most cases and these interact in complex ways

Understanding Genetic Diversity

• Natural selection should drive good traits, but the amount of genetic diversity in a population is also important, if the bad traits show a higher frequency.
• Every organism has genetic diversity.
• Genetic diversity is abundant.

Different Types of Genetic Variation

• Deleterious - variations are bad, reduce fitness
• Neutral - no effect on fitness
• Advantageous - variations help survival or reproduction

Why Do Genetic Diseases Persist?

• Many genetic diseases are recessive, this means that an individual has to have 2 copies of the harmful version to show signs of the disease and only a small percentage of the population are homozygous for the harmful recessive gene

New Deleterious Mutations

• Many new deleterious mutations occur in every meiosis, but selection swiftly removes them
• They are usually recessive and selection in a large population is slow

Genetic Diversity and Bottlenecks

• Population bottlenecks can occur due to events such as natural disasters or disease outbreaks
• Bottlenecks lead to reduced genetic diversity, as individuals are lost
• The remaining individuals pass on any existing genetic variation, which can cause higher representation of some traits and variations.

Neutral mutations not subject to selection

• Neutral mutations do not affect phenotype.
• These are usually outside of genic regions, like introns or third base pairs (no amino acid change).
• Small populations have more pronounced effects of neutral mutations.
• Large populations have a larger representation of neutral mutations over time.

Speed of Divergence when Separate

• Rate of reproductive isolation differs between species.
• Mammals have lower tolerance of hybridization than other groups, requiring faster reproductive isolation.

How Do Organisms Adapt to Changing Environments

• The rate of speciation is variable.
• Speciation rates depend on niche space and resources available in a new environment
• Diversification occurs when new habitats have sufficient resources.
• When niches become saturated, the rate of speciation slows.

The Paradigm

• Spatial isolation creates independent gene pools (allopatric, peripatric).
• Divergence is based on evolutionary processes, which can happen when groups are isolated from each other leading to speciation.

Spatially Divergent Selection with Gene Flow

• Spatial isolation can promote speciation
• Different phenotypes that live in similar environments can still be different due to different evolutionary pressures

Sky Islands

• Mountain tops/peaks are isolated habitat, like little islands.
• Species evolve in isolated areas due to limited dispersal (i.e. the top of a tall mountain).

Many Mammal Radiations Come After the Landscape

• Geological events like the uplift of mountain ranges or the formation of new land masses may create new or modified habitats, thereby leading to new speciation.

General Summary of Speciation

• Species are defined by their inability to interbreed and exchange genes with other species.
• Speciation can be caused by factors like geographical isolation (allopatric speciation).
• Speciation can also happen when there is a sudden environmental change where populations adapt to new environments (sympatric speciation)
• Natural selection is the main driving force for change in evolution, but genetic drift is a major factor in small populations.

Sexual Dimorphism

• Sexual dimorphism is the distinct differences in physical characteristics between males and females within a species.
• These differences in structure can lead to male-male competition.
• Females will pick a mate who meets their criteria for the best traits for progeny.
• The choice can be arbitrary.

Intrasexual vs Interssexual Selection

• Intrasexual selection: Competition between males within a species for access to females
• Interssexual selection: Females choosing males based on their traits
• These are strategies in the pursuit of reproduction
• Sexual selection leads to male-male competition and mate choice

Sexual Conflict

• Males and females may have conflicting interests in reproduction
• This gives way to sexual conflict– male and female strategies can differ dramatically, in some cases greatly impacting the health of the female.

Summary of Sexual Selection

• Natural Selection leads to the survival and reproduction of organisms with characteristics that are most successful in a given environment.
• Sexual Selection is part of this process involving competition within the same sex (intrasexual) and/or choice by the opposite sex (intersexual).
• The traits produced by these types of selection can have significant costs or benefits to the individual.

Test your knowledge on mutations, natural selection, and reproductive isolation in organisms. This quiz explores the differences between microbes and larger organisms, the mechanisms of genetic isolation, and the implications of sexual selection in evolution. Dive into the world of genetics and see how well you understand these concepts!