Biological Species Concept Quiz

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Questions and Answers

What does the Biological Species Concept (BSC) primarily focus on?

The evolutionary history of organisms

The habitat preferences of different populations

The physical characteristics of organisms

Reproductive isolation among groups of populations (correct)

Which of the following scenarios best describes allopatric speciation?

Two species share a habitat but do not interbreed due to behavioral differences

A population migrates to a new area and establishes a separate gene pool

A population is divided by a physical barrier causing reproductive isolation (correct)

Genetic drift occurs in a small isolated group leading to new species

What distinguishes sibling species from sister species?

Sister species share a more recent common ancestor (correct)

Sibling species have different reproductive behaviors

Sister species do not interbreed under any circumstances

Sibling species occupy the same geographic area

Which of the following describes the founder effect in peripatric speciation?

A small group establishes a new population with limited genetic diversity Signup and view all the answers

Which of the following best exemplifies vicariance in speciation?

A river forms, separating two populations of a species Signup and view all the answers

In the context of the Biological Species Concept, what is reproductive isolation?

Biological differences that reduce gene exchange between groups Signup and view all the answers

What might lead to rapid speciation in a small isolated population?

Genetic drift affecting allele frequencies significantly Signup and view all the answers

What is a characteristic of two populations that are considered sibling species?

They have distinct ecological roles in their environment Signup and view all the answers

What is the primary factor influencing the proportion of hybrid offspring in the studied species?

Genetic differences between parental types Signup and view all the answers

What happens to a diploid species when its entire genome is doubled?

It becomes a tetraploid with four copies of every chromosome. Signup and view all the answers

How is sexual isolation among local populations of crickets represented?

By genetic differences in mating calls and preferences. Signup and view all the answers

Which species pair resulted in the tetraploid species T.miscellus?

T.dubius and T.pratensis Signup and view all the answers

What reproductive strategy contributes to speciation in larger islands?

Sexual selection among populations. Signup and view all the answers

What distinguishes tetraploids from diploids in the context of chromosome count?

Tetraploids have twice as many chromosomes as diploids. Signup and view all the answers

Why is speciation more likely in species with restricted gene flow?

It promotes genetic divergence over time. Signup and view all the answers

What factor is least likely to influence the offspring ratio of hybrids when two parental types are crossed?

Identical mating calls among males. Signup and view all the answers

What primarily influences sex determination in environmental sex determination (ESD)?

External environmental factors Signup and view all the answers

Which reproduction method is associated with haplodiploid sex determination?

Fertilized eggs develop into females and unfertilized eggs develop into males Signup and view all the answers

What is a key benefit of individuals with more attractive floral displays?

They attract more pollinators, increasing fitness Signup and view all the answers

How can females control the sex ratio in haplodiploid systems?

By choosing whether to fertilize eggs Signup and view all the answers

In terms of sex ratios, what does an unequal sex ratio indicate?

Significant environmental influence Signup and view all the answers

What role does temperature play in environmental sex determination?

It can determine the sex during egg development. Signup and view all the answers

Which of the following is NOT a characteristic of environmental sex determination?

Sex determined by chromosomes Signup and view all the answers

What is one distinct feature of haplodiploid sex determination in species such as ants and bees?

Unfertilized eggs develop into males Signup and view all the answers

What is a primary disadvantage of specialization in organisms?

Vulnerability to environmental changes Signup and view all the answers

Which of the following best describes morphological trade-offs in specialization?

Improved ability in one task while limiting others Signup and view all the answers

What can be a consequence of genetic drift in small populations?

Accumulation of deleterious mutations Signup and view all the answers

What type of environments do populations tend to evolve broader niches?

Variable environments Signup and view all the answers

Which mechanism can lead to specialization without trade-offs?

Unequal selection pressures Signup and view all the answers

What might happen to specialized traits in constant environments over time?

They may experience negative correlations in fitness Signup and view all the answers

What is a physiological trade-off associated with specialization?

Ability to adapt to salt-rich environments Signup and view all the answers

Which aspect of specialization can lead to reduced behavioral flexibility?

Host plant preference in insects Signup and view all the answers

What does relatedness (r) measure in the context of evolutionary biology?

The genetic overlap between individuals Signup and view all the answers

Which situation would most likely promote altruism according to Hamilton's Rule?

High relatedness with significant benefits to the recipient Signup and view all the answers

How is direct fitness defined in relation to fitness strategies?

Fitness related to the number of offspring produced Signup and view all the answers

What is a key characteristic of the evolutionary stable strategy (ESS)?

It remains stable when adopted by a population Signup and view all the answers

In haplodiploid species like bees, how is relatedness among sisters described?

r = 0.75 Signup and view all the answers

What is the result when cooperative bacteria like Pseudomonas aeruginosa operate under high relatedness and weak competition?

Enhanced cooperation occurs Signup and view all the answers

What is typically the cost to the subordinate male in the context of altruistic mating displays in wild turkeys?

0.9 offspring Signup and view all the answers

Which statement best describes kin selection?

It promotes altruistic behavior among relatives Signup and view all the answers

What is the relationship between population size and cannibalism rates according to the findings?

Higher population sizes are associated with lower cannibalism rates. Signup and view all the answers

What factor is primarily favored by selection in pathogens?

Traits that increase the number of hosts they infect. Signup and view all the answers

Which of the following correctly distinguishes vertical from horizontal transmission in parasites and pathogens?

Vertical transmission occurs when pathogens infect the offspring of the current host. Signup and view all the answers

How does cooperation differ from altruism in evolutionary terms?

Cooperative behavior can provide benefits without reducing the actor’s fitness. Signup and view all the answers

What evolutionary outcome is observed with highly virulent pathogens?

They may infect a new host more frequently. Signup and view all the answers

Which statement accurately describes endosymbionts?

They can be mutualists found within the cells of their hosts. Signup and view all the answers

Which statement best characterizes the fitness implications of altruism?

Altruism provides benefits to others while reducing the fitness of the actor. Signup and view all the answers

What is a significant feature of the transmission strategies of pathogens and parasites?

They sometimes evolve to become highly virulent for better host infection. Signup and view all the answers

Study Notes

Species and Speciation

Species are groups of organisms that biologists define as a Latin word for "kind"
Early taxonomists, like Linnaeus, viewed species as distinguishable groups.
Organisms' knowledge grew, and this criterion became inadequate.
For example, two types of small owls are so similar in eastern North America that distinguishing them as different species needed a broader criterion.

Biological Species Concept (BSC)

A species is a group of actually or potentially interbreeding populations.
Reproductive isolation separates them from other groups.
Even if they are not geographically separated, biological differences in the groups greatly reduce gene exchange.
The BSC recognizes variation within populations and between geographic populations, including cases of "sibling species."
Sibling species are very similar in appearance but differentiated by ecology, behavior, genetic markers and chromosomes

Modes of Speciation: Allopatric

Speciation through geographic isolation: Separated populations.
Vicariance: A physical barrier divides a population.
Dispersal: A subset of individuals colonizes a new area, creating isolation.

Modes of Speciation: Peripatric

A special case of dispersal: A small group of geographically isolated individuals colonize an area.
Genetic drift: Random changes in allele frequencies can lead to rapid speciation.
Founder Effect: Establishing a new population with reduced genetic diversity.

Modes of Speciation: Parapatric

Speciation with partial isolation: Populations are partially isolated.
Ecological Isolation: Species occupy different ecological niches in the same area.
Ecological Speciation: Selection for different ecological adaptations drives speciation.

Modes of Speciation: Sympatric

Speciation without geographic isolation.
Populations diverge within the same area.
Sexual Isolation: Differences in mating preferences or behaviors lead to reproductive isolation.
Disruptive Selection: Selection favors extreme phenotypes, leading to speciation.

Phylogenetic Species Concepts

Defining species based on evolutionary history: The smallest group of organisms that share a common ancestor and are distinct from other groups.
Focus on monophyly; a species is a monophyletic group, meaning all members descend from a single common ancestor.

Key Concept: Reproductive Isolation

The inability of individuals from different populations to interbreed and produce viable, fertile offspring.
Gene flow: The movement of genes between populations.
Reproductive isolation: The absence of gene flow between populations.
Reproductive Isolating Barriers: Mechanism that prevent gene flow (before or after fertilization).

Dobzhansky-Muller Incompatibilities (DMIs)

Incompatible interactions between genes inherited from two parents.
Example in Drosophila: Male F1 hybrids sterile; females fertile. Combination of chromosomes from the two species reduces male fertility.
Interactions between autosomes of simulans and the X chromosome of mauritiana is an example.

How fast does reproductive isolation evolve?

The time required for reproductive isolation to become strong, after it has started to evolve, varies greatly.
Polyploidy (especially common in plants) requires only one or two generations.

Genetic Mechanisms

Epistasis: Interactions between genes at different loci can contribute to reproductive isolation.
Inversion: A chromosomal rearragement reduces gene flow.
Reciprocal translocation: Exchange of genetic material between non-homologous chromosomes.
Segregation Distortion: Genes bias their own transmisson leading to reproductive isolation.
Genetic Conflict: Conflicts between genes drive speciation.

Introgression

Transfer of genetic material from one species to another by hybridization.
Can introduce new alleles, or counter the effects of reproductive isolation by mixing gene pools.
Examples: Human-Neanderthal gene transfer.

Classification of Isolating Barriers: Premating

Ecological isolation: Potential mates don't meet.
Temporal isolation: Species breed at different times(seasons or days).
Habitat isolation: Species mate in different habitats.
Immigrants between divergent populations don't survive long enough to interbreed.
Sexual isolation in animals: Individuals prefer mating with members of their own species.
Pollinator isolation in plants: Pollinators don't transfer pollen between species.

Classification of Isolating Barriers: Postmating, Prezygotic

Mechanical isolation: Reproductive structures don't fit.
Copulatory isolation: Female isn't stimulated by males of the other species.
Gametic isolation: Failure of fertilization.

Classification of Isolating Barriers: Postzygotic

Extrinsic: Hybrids have low fitness for environmental reasons.
Ecological inviability: Hybrids poorly adapted to both parental habitats.
Behavioral sterility: Hybrids are less successful in obtaining mates.
Intrinsic: Low hybrid fitness is independent of environmental context.
Hybrid inviability: Reduced survival due to genetic incompatibility.
Hybrid sterility: Reduced production of viable gametes.

Reinforcement

The process by which prezygotic barriers become stronger due to selection against hybridization.
Natural selection favors individuals that avoid mating with other species.
Introgression and reinforcement; Introgression sometimes leads to reinforcement by increasing prezygotic barriers.

Speciation by Sexual Selection

Evolution of sexual isolation by sexual selection.
Pulse rate of mating calls of Laupala cerasina and the preferred pulse rate of females differ among populations.

Speciation by Polyploidy

When a diploid species' entire genome is doubled, the result is a tetraploid. This has four copies of every chromosome.
Examples in goatsbeards (Tragopogon) illustrate allotetraploidy through hybridization. The tetraploids have twice as many chromosomes as their diploid parents.

Speciation, Geographic Isolation, and Gene Flow

Speciation is more likely on larger islands and in species with restricted gene flow.
Measured as 1/FST between populations.
FST is a measure of genetic differentiation that decreases with greater gene flow.

Speciation Conclusion

Speciation is necessary for biodiversity by driving the emergence of new species, contributing to ecosystem richness and enabling adaptation to different environments and ecological niches across Earth.
Understanding speciation enables evolutionary research and conservation efforts, and addresses human impacts on biodiversity.

Sex

Sex refers to biological characteristics that define organisms as male or female.
Usually determined by chromosomes and reproductive systems
Also includes sexual activity, involving physical intimacy for reproduction or pleasure.

Males and Females

In eukaryotes, females produce large, immobile eggs and males produce, small, mobile sperm (anisogamy).
Some species have separate sexes and those determined by genetics or environment.
Other species are hermaphroditic to enhance reproductive assurance when mates are scarce
Sexually dimorphic traits are important for species identification.

Sexual Selection

Selection due to competition for mates among individuals of the same sex.
Traits that decrease survival, if reproductive advantage compensates for it, can evolve via sexual selection.
Alternative mating strategies exist in some species
Example: Paracerceis sculpta isopods
Sperm competition - a tactic males use to increase the chance of successfully fertilizing a female's eggs (often by interfering with rival sperm)

Sexual Selection by Female Choice

Direct benefits: Males enhance female fitness by providing resources
Pleiotropic effects: Genes influencing non-mating functions influence mating preferences.
Good genes hypothesis: Females select mates with traits indicating high genetic quality, like health or foraging ability to increase their offspring's survival and reproductive success.
Fisher's runaway: A feedback loop between female preference for a male trait and enhanced expression of that trait, driving exaggerated traits over time.

Sexual Selection in Flowering Plants

Male-male competition for pollen donors and male preference as pollen receptors
Individuals with more attractive floral displays typically attract more pollinators, positively influencing fitness.

Sex Ratios

The relative number of males and females.
Sex is determined by chromosomes (e.g., humans with XX for females and XY for males).
Environmental sex determination (ESD): external factors such as temperature influences sex in some organisms.
Haplodiploid sex determination: The sex of offspring is determined by whether the egg is fertilized or not.

Fitness in Age-Structured Populations

Fitness is the organism's ability to survive and reproduce, passing on genes to the next generation.
Iteroparity: Reproduction multiple times over lifespan.
Semelparity: Reproduction only once in a lifetime

Lifetime Reproductive Success (R)

Total reproductive output across an organism’s life span
Life tables help calculate and illustrate R.

Reproductive Timing

Absolute fitness, or rate that genes spread within a population depends on reproductive timing.
Those that reproduce earlier generally spread genes faster.

Senescence and Natural Selection

Gradual decline in biological function with age. Illustrates how natural selection shapes life histories.
Natural selection favors traits enhancing survival and fecundity at earlier ages.

Antagonistic Pleiotropy

Some genes may have opposing effects on early versus late life.
Alleles that increase reproductive effort early in life often reduce biological functions later.

Population Growth

In simple models, population's per capita growth rate decreases proportionally with increasing density.
Carrying capacity (K) is where birth and death rates are balanced.
r selection occurs more so at low population densities.
k selection occurs at higher densities.

Ecological Succession

Dynamics between r-selected and K-selected species illustrate ecological succession.
R-selected species are typically fast-growing weeds that reproduce quickly to take advantage of available resources in habitats such as landslides.
K-selected species, such as slow-growing trees, reproduce later in time but sustain longer reproductive life.

Diverse Life Histories

Strategies organisms use for growth, reproduction and survival.
Species adapt reproductive strategies to ecological pressures and survival rate.
Specialist traits in some organisms and generalist in others.

Specialist and Generalist

Specialists are highly adapted to specific environmental conditions and resources. Narrow niches.
Generalists can adapt to a wide range of environmental conditions and resources. Broad niches.
Trade-off frequently exists between specialization and generalization

Factors Influencing Specilization and Generalization

Trade-offs between specialization and generalization.
Environmental variability
Genetic drift.

Advantages of Specialization

Efficiency, Predator Avoidance, Reduced Competition

Cost of Specialization

Resource Limitation
Vulnerability to environmental changes

Trade-offs in Specialization

Morphological trade-offs
Physiological trade-offs
Behavioral trade-offs.

Specialization Without Trade-offs

While many cases of specialization involve trade-offs, it's possible for a population to evolve specialization without sacrificing performance.
Unequal Selection, Genetic Drift, and Mutational decay.

Experiments on Niche Evolution: Variable vs. Constant Environments

Variable environments: Tend to evolve broader niches, including generalist and specialist genotypes.
Constant environments: Tend to be more specialized, potentially leading to negative fitness correlation and loss of traits.

Key Findings from Experimental Studies

Loss of unused traits
Pleiotropic effects

Cooperation and Conflict

Cooperation and conflict: Found at all levels of biological organization, from within the organism to among populations. There is both cooperation and conflict among individuals in many situations.
Genes compete with one another. Offspring often compete with parents
Examples include families, social groups and interactions among populations.
Cooperation among unrelated individuals: Mutualistic behavior is mutual benefit for both parties involved. Benefits include survival, success and well-being.
The costs and benefits of interaction
Mutualistic
Selfish
Altruistic
Spiteful
Social interactions and cooperation: Fundamental aspects of animal and human behaviour, enabling individuals to work together for mutual benefit.
Reciprocity (Social principle of responding to a positive action with another positive action.)
Game Theory (Mathematical approach to understanding strategies in situations of conflict or cooperation between individuals).
Evolutionary Stable Strategies (ESS): Strategy in game theory, when adopted in a population, cannot easily be overtaken by any alternate strategy.
Shared Genes and the evolution of altruism: Direct fitness, Indirect fitness, Inclusive Fitness
Calculating relatedness (r): Measure of genetic overlap between individuals. Diploid species (Parents contribute 50% of their alleles; full siblings on average share 50% of their alleles)
Calculating relatedness in haploid diploid organisms
Kin selection and indirect fitness- When relatedness is high or when benefits are substantial, altruistic behaviours are more likely.
Implications of kin selection: Altruistic behaviours are more common among closely related organisms.
Eusocial animals: species where some individuals do not reproduce much to instead rear offspring. (ex. Ants)
Cooperation in bacteria and the green bead effect: High relatedness and low competition leads to cooperation. Low relatedness and high competition favours cheating.
Spite and conflict in bacteria
Parental investment conflicts: Trade-offs in parental care among different species

Examples of parental care in different species

Cooperative Care: Both parents actively care for offspring
Male-Only Care: Male guard eggs to attract mates
Trade-off: Higher energy investment by males, but potential for additional mating.

Parental investment conflicts

Species variation in parental care depending on costs and benefits.
ESS Outcome: One parent may invest less if the other is highly invested.
Scorpions and poison dart frogs

Murder (infanticide and siblicide) in families

Behavior: Individuals killing offspring for resources, increasing their reproduction.
Examples: Baboons and lions.
Parent-Offspring conflict: Conflict of interest between parent and offspring over the allocation of resources.
Examples: Between mother and embryo.

Eusocial animals

Species in which some individuals don't reproduce (much/at all) to instead rear offspring (usually parents).

Levels of DNA Selection

Selfish DNA
Selfish Mitochondria.

Why- Evolved Cooperation through Vertical and Horizontal Transmission

Because Mitochondria are maternally inherited, any mutation in mitochondria which increases the number of ovules, is favoured.
The effect on male reproduction does not matter to the mitochondria, since they are not transmitted through pollen.
The CMS+ allele knocks out male reproductive function and resources become diverted to making more ovules

Group Selection

Evolution by group selection - changes in allele frequencies when selection acts on groups, the same as when it acts on individuals.
Competition between individuals.
Group vs individual trade offs

Experiment-Flour Beetle (Tribolium castaneum) Experiment

Shows that group selection can cause large evolutionary changes.
Noticed three particular trends in the experiment.
Nine times more beetles per group that selected for larger sizes, when compared to low size.
Population size decreased in all three treatments due to cannibalism
In the high population size treatment, cannibalism rates were lower, which is seen as the evolution of an altruistic behavior.

Pathogens

Virulence: pathogens favour traits that increase the number of hosts they infect.
Multiplication in the host.
Some reproduce slowly which increases chances of infecting a wider range of hosts.

Cooperation and Major Evolutionary Transitions

Fitness of parasites and pathogens depends on horizontal transmission.
Parasites and pathogens sometimes selected for higher virulence.
Endosymbionts are mutualists inside hosts, and passed on by vertical transmission.

Differences Between Parasites and Pathogens to Endosymbionts

Endosymbionts and their hosts are chained together – their fitness depends entirely on each other
In extreme cases, the symbiont becomes essential for the host, forming a new collective entity.

General Study Notes

The concept of a cost of reproduction is crucial for understanding life history evolution.
Genotypes with more resources for reproduction may have decreased survival or growth, leading to a negative genetic correlation.
Variation in resource acquisition can positively correlate with reproduction and survival.

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Description

Test your understanding of the Biological Species Concept and speciation processes with this quiz. Cover topics such as allopatric speciation, reproductive isolation, and the founder effect. Determine how these concepts relate to real-world scenarios and species dynamics.