Exam 2 Study Guide Flashcards

A set of 60 vocabulary flashcards based on the Exam 2 Study Guide covering evolution, genetic drift, and species concepts.

Darwin's Peacock Dilemma

The observation that the elaborate tail of a male peacock seemed to contradict natural selection because it made the bird more vulnerable to predators.

Weaponry

Physical structures such as horns or tusks that differ between males and females in many species due to competition for mates.

Selection Pressure

The evolutionary force that causes differences in size, strength, and weaponry between males and females in many species.

"Good genes" hypothesis

A theory suggesting that females choose mates with exaggerated traits because those traits serve as indicators of high genetic quality and fitness.

Unequal contribution by heterozygotes

A phenomenon where individuals with two different alleles do not contribute those alleles equally to the next generation, leading to genetic drift.

Genetic Drift

A mechanism of evolution characterized by random changes in allele frequencies within a population.

Population Size and Drift

The principle that unequal contribution by heterozygotes has a significantly larger effect on small populations compared to large ones.

Phenotype Mortality Chance

The situation where a relatively large fraction of a certain phenotype dies or fails to breed by chance, causing a change in allele frequency.

Natural Selection vs. Genetic Drift

Natural selection is driven by unequal survival and fitness, whereas genetic drift is driven by random chance events.

Law of Large Numbers

A statistical principle stating that as a sample size increases, its attributes will more closely reflect the average of the whole population.

Bottleneck Event

A sharp reduction in the size of a population due to environmental events or human activities, such as catastrophes.

Bottleneck Result

A situation that typically leads to a drastic reduction in genetic diversity and a significant shift in allele frequencies.

Conservation Biologists' Concern

The worry that populations with low genetic diversity following a bottleneck may lack the ability to adapt to environmental changes.

Elephant Seals

A specific species used to illustrate a bottleneck event, resulting in a population with very low genetic variation.

Low Evolutionary Potential

A condition where a population lacks the genetic variation necessary to adapt to future environmental shifts or diseases.

Founder Effect

A type of genetic drift that occurs when a new population is established by a small number of individuals from a larger population.

Island Communities

Geographic locations where founder effects are especially prevalent due to physical isolation and limited migration.

Insular Cultures

Human societies where marriage to individuals outside the culture is discouraged, leading to increased prevalence of founder effects.

Typological Species Concept

A species concept based on the naming and classification of organisms according to a fixed "type" specimen.

Naming Species Complications

Difficulties in modern taxonomy caused by old systems that do not account for the natural variation within a species.

Reproductive Isolation

The existence of biological factors or barriers that prevent members of two different species from interbreeding.

Evolution of New Species

A process that fundamentally requires reproductive isolation to allow populations to diverge genetically.

Biological Species Concept (BSC)

A species definition centered on the ability of individuals to interbreed and produce fertile offspring.

BSC Central Component

The requirement of reproductive isolation between different groups to define them as separate species.

Pre-zygotic Isolation Mechanism

A reproductive barrier that prevents an egg and sperm from ever meeting or forming a zygote.

Post-zygotic Isolation Mechanism

A reproductive barrier that occurs after fertilization, such as the production of sterile or inviable offspring.

Ecological Isolation

A reproductive barrier where two species occupy different habitats within the same area and rarely encounter each other.

Behavioral Isolation

An isolation mechanism based on species-specific courtship rituals or other behaviors that prevent interbreeding.

Temporal Isolation

A mechanism where two species are prevented from interbreeding because they breed at different times of day, seasons, or years.

Mechanical Isolation

A reproductive barrier where morphological differences, such as incompatible genitalia, prevent successful mating.

Gametic Isolation

A condition where the sperm of one species is unable to fertilize the egg of another species.

Sterile Hybrid

An offspring produced by two different species that cannot reproduce, such as a mule, signifying the parents are different species.

Phylogenetic Species Concept (PSC)

A species definition based on the smallest monophyletic group that can be distinguished by a diagnostic trait.

Monophyletic Group

A group of organisms that consists of a common ancestor and all of its lineal descendants.

Diagnostic Trait

A unique characteristic (physical or genetic) that identifies a specific species within the phylogenetic species concept.

Phylogenetic Tree

A diagram used to interpret evolutionary relationships and determine which traits a particular species possesses.

Paraphyletic Group

A group of organisms that includes a common ancestor but only some of its descendants.

Over-splitting

A potential problem with the phylogenetic species concept where very small genetic differences lead to the naming of many new species.

Conservation of Rare Species

An area of biology where the choice between the biological and phylogenetic species concepts can influence which groups receive protection.

Unique Genetic Identities

The distinct hereditary characteristics of a population that conservationists aim to preserve through proper species classification.

Allopatric Speciation

The formation of new species that occurs when populations are geographically isolated from one another.

Sympatric Speciation

The formation of new species that occurs within the same geographic area without physical isolation.

Vicariance

A process leading to allopatric speciation where a physical barrier, like a mountain range, splits a population's habitat.

Dispersal

A process leading to allopatric speciation where a few individuals move to a new, isolated geographic area.

Environmental Divergence

The role of different habitats in driving the evolution of new traits during allopatric speciation.

Blackcap Example

A case study of sympatric speciation involving birds with different migratory paths and mating preferences.

Butterfly Example

An illustration of sympatric speciation where mate choice or host plant preference leads to reproductive isolation.

Fish Example

Instances of sympatric speciation often observed in lake environments, where different feeding niches lead to divergence.

Male Selection Pressure

Evolutionary forces often focused on competition for mates, leading to increased size or weaponry.

Female Selection Pressure

Evolutionary forces often focused on mate choice and survival for the purpose of raising offspring.

Breeding Age

The stage of life at which an organism is capable of reproduction; random death before this stage contributes to genetic drift.

Allele Frequency Change

The specific shift in the proportion of an allele in a population’s gene pool, which can be caused by drift or selection.

Small Populations

Groups of organisms where random events like genetic drift have a disproportionately high impact on the gene pool.

Geographic Barrier

A physical feature like a river or mountain that prevents gene flow between populations, facilitating allopatric speciation.

Inherited Traits

The characteristics passed from parents to offspring that are tracked using phylogenetic trees.

Asexual Species Problem

A major limitation of the biological species concept because it cannot define species that do not interbreed.

Ancestral Population

The original group from which new species evolve during the process of speciation.

Common Ancestor

The shared progenitor of different species represented at the nodes of a phylogenetic tree.

Selection for Mates

The primary mechanism driving the evolution of traits like a peacock's tail under the sexual selection model.

Speciation Mechanism

The evolutionary process (such as mate choice or niche adaptation) that results in the split of one species into two.