Macroevolution and Phenotype (Notes)

Macroevolution

Focuses on large-scale evolutionary changes over long geological timeframes, specifically looking at how phenotypes change and how new species originate.

Phylogenetic Trees

Diagrams that illustrate evolutionary relationships and ancestral lineages among organisms.

Homologous Structures

Physical characteristics shared by different species inherited from a common ancestor, which may have diverged in function.

Branch Lengths

Represent the amount of evolutionary change or time represented between common ancestors in phylogenetic trees.

Biological Species Concept

Defines a species as a group of natural populations that can interbreed and produce viable offspring.

Morphological Species Concept

Characterizes species based on observable physical traits and anatomical structures.

Ecological Species Concept

Defines species in terms of their ecological niche and role within the environment.

Phylogenetic Species Concept

Defines a species as the smallest group of individuals sharing a unique genetic lineage.

Phenotype

The physical, physiological, or behavioral expression of an organism's traits.

Genotype

The underlying genetic code responsible for the phenotype, represented by pairs of alleles.

Prezygotic Barriers

Mechanisms that prevent fertilization or zygote formation between different species.

Postzygotic Barriers

Mechanisms that prevent a hybrid zygote from developing into a fertile adult.

Allopatric Speciation

Occurs when a geographic barrier physically isolates subpopulations, leading to the formation of new species.

Sympatric Speciation

Occurs without geographic separation, driven by ecological factors or reproductive isolation mechanisms.

Gradualism

Model of evolution where species diverge slowly through steady, incremental changes over time.

Punctuated Equilibrium

Model of evolution characterized by long periods of stability interrupted by rapid bursts of speciation.

Generalists

Species with broad resource tolerances, experiencing slower evolutionary rates due to relaxed selective pressures.

Specialists

Species with narrow, specific dietary or environmental requirements, exhibiting accelerated speciation rates.

Adaptive Radiation

The rapid divergence of an ancestral species into multiple specialized descendant species filling diverse ecological roles.