BIO1022 Week 1 – Natural Selection & the Tree of Life

Vocabulary flashcards covering key terms and concepts for BIO1022 Week 1: Natural Selection, Speciation, and Phylogenetics.

Natural Selection

Process whereby heritable traits that improve biological fitness become more common in a population over generations.

Artificial Selection

Intentional breeding by humans to enhance desirable traits in organisms.

Sexual Selection

Type of natural selection in which individuals with certain traits are more likely to obtain mates and reproduce.

Advantageous Mutation

Genetic change that increases an organism’s fitness and tends to rise in frequency via positive selection.

Deleterious Mutation

Genetic alteration that reduces fitness and is usually removed by negative (purifying) selection.

Allele Frequency

Proportion of a specific allele among all allele copies in a population’s gene pool.

Gene Pool

Complete set of alleles present in all individuals of a population.

Biological Fitness

Relative ability of an individual to survive and produce viable, fertile offspring.

Positive Selection

Selection that increases the frequency of a beneficial allele in a population.

Negative Selection (Purifying)

Selection that removes harmful alleles, lowering their frequency.

Balancing Selection

Natural selection that maintains two or more alleles in a population.

Stabilising Selection

Selection favouring intermediate phenotypes while acting against extremes.

Directional Selection

Selection favouring one extreme phenotype, shifting the population mean.

Disruptive Selection

Selection favouring both extreme phenotypes over intermediate forms.

Intra-sexual Selection

Competition among individuals of the same sex (often males) for access to mates.

Inter-sexual Selection

Mate choice by one sex (often females) selecting among individuals of the opposite sex.

Biological Species Concept (BSC)

Defines species as groups of actually or potentially interbreeding natural populations that are reproductively isolated from others.

Morphospecies Concept

Species identification based on morphological similarity and distinctiveness.

Ecological Species Concept

Defines species by their unique ecological niche and role in the environment.

Phylogenetic Species Concept

Defines a species as the smallest monophyletic group on a phylogenetic tree.

Common Ancestor

The most recent ancestral organism from which two or more descendants evolved.

Gene Flow

Movement of alleles among populations through migration and reproduction.

Hybridization

Interbreeding between individuals from two distinct populations or species, producing hybrids.

Hybrid

Offspring resulting from mating between two different species or genetically distinct populations.

Reproductive Isolation

Barriers preventing gene flow between populations, leading to new species formation.

Pre-zygotic Isolation

Reproductive barriers acting before fertilisation (e.g., behavioural, temporal, mechanical, gametic).

Post-zygotic Isolation

Barriers acting after fertilisation that reduce hybrid viability or fertility.

Allopatric Speciation

Speciation that occurs when populations become geographically separated.

Peripatric Speciation

Allopatric speciation in a small peripheral population isolated from the main population.

Vicariance

Physical splitting of a population by a barrier, leading to allopatric speciation.

Co-speciation

Parallel speciation of two interacting groups (e.g., host and parasite) due to shared evolutionary history.

Sympatric Speciation

Speciation occurring within the same geographic area, often via disruptive selection or hybridisation.

Gamete

Haploid reproductive cell (sperm or egg) that fuses with another to form a zygote.

Zygote

Diploid cell formed by the fusion of two gametes.

Phylogenetic Tree

Branching diagram representing evolutionary relationships inferred from shared derived characters.

Monophyletic Group

Clade consisting of an ancestor and all of its descendants.

Paraphyletic Group

Group containing a common ancestor and some, but not all, of its descendants.

Polyphyletic Group

Group composed of organisms that do not share a recent common ancestor within the group.

Character (Phylogenetics)

Observable trait used to infer evolutionary relationships; may be morphological, molecular, or behavioural.

Character State

Specific condition of a character (e.g., presence or absence of wings) in a taxon.

Homologous Characters

Traits inherited from a common ancestor; useful for reconstructing phylogenies.

Analogous Characters

Similar traits evolved independently via convergent evolution; can mislead phylogenetic inference.

Synapomorphy

Shared derived character that indicates common ancestry within a clade.

Parsimony (Phylogenetics)

Principle favouring the phylogenetic tree requiring the fewest evolutionary changes.

Convergent Evolution

Independent evolution of similar traits in unrelated lineages due to similar selective pressures.

Divergent Evolution

Accumulation of differences between closely related lineages leading to speciation.

Outgroup

Taxon outside the study group used to root the tree and infer character polarity.

Root (Phylogenetics)

Basal node representing the most recent common ancestor of all taxa in the tree.

Node

Branching point on a phylogenetic tree indicating a common ancestor of descendant lineages.

Branch

Line on a phylogenetic tree representing a lineage between two nodes.