Biol 111 – Exam II Practice: Phylogeny and Plant Structure

Vocabulary flashcards covering phylogenetic tree interpretation, homology versus homoplasy, and primary/secondary plant anatomy and growth based on Biol 111 Exam II review materials.

Hierarchical Classification System

A taxonomic system whose nested levels (such as phyla, classes, and genera) differ from one another on the basis of their inclusiveness.

Homoplasy

A character shared by a set of species but not present in their common ancestor, resulting from convergent evolution or independent adaptation (e.g., the legless condition in extant lizards or four-chambered hearts in birds and mammals).

Homologous Structures

Anatomical features in different species that share common evolutionary ancestry, such as the skeletal bones of a bat wing and a human forelimb.

Convergent Evolution

The independent evolution of similar structural or functional adaptations in distinct lineages, such as the antler-like head structures found in beetles, flies, and male deer.

Principle of Parsimony

The methodological principle applied in phylogenetic tree reconstruction based on the rationale that similarity due to common ancestry should be more common than similarity due to convergent evolution.

Outgroup

A closely related species or taxon (such as a lily in an orchid study) used when constructing a phylogenetic tree to determine ancestral versus derived character states.

Basal Taxon

A lineage that diverges early in the evolutionary history of a group and originates near the common ancestor of the clade (such as the salamander lineage relative to lizards, goats, and humans).

Paraphyletic Group

A taxon consisting of an ancestral species and some, but not all, of its descendants (such as the subgroups A–D of Giardia intestinalis excluding Giardia microti).

Monophyletic Group

A clade consisting of an ancestral species and all of its descendants (such as the grouping of taxa E, F, and G sharing a common node).

Parenchyma Cells

Loosely packed, thin-walled plant cells with prominent chloroplasts that retain the metabolic capability to divide, carry out photosynthesis, and store photosynthate.

Sclerenchyma Cells

Rigid plant cells with thick, lignified secondary cell walls that provide structural support to mature, non-elongating tissues.

Collenchyma Cells

Elongated plant cells characterized by unevenly thickened primary walls that provide flexible structural support to young, actively growing parts of a plant.

Root Hairs

Tubular outgrowths of epidermal cells located near the growing root tip that absorb the majority of water and dissolved minerals from the soil.

Tracheids

Tubular, non-living xylem cells with lignified secondary walls that transport water and are incapable of DNA transcription at maturity.

Sieve-Tube Elements

Living conducting cells of the phloem vascular tissue that lack a nucleus at maturity and transport sugars long distances via translocation.

Stele

The central vascular cylinder of a primary root, composed of xylem, phloem, and surrounding pericycle tissue.

Cuticle

A waxy epidermal coating that covers leaves and stems to restrict water loss, but is typically absent from absorbing root surfaces.

Indeterminate Growth

A pattern of growth characteristic of most plants in which the organism continues to grow, elongate, and add new organs throughout its life via meristematic activity.

Zone of Maturation

The section of the primary root where cells complete their differentiation and achieve full functional maturity, such as vessel elements losing their protoplasts.

Spongy Mesophyll

A loosely organized internal leaf tissue with abundant intercellular air spaces that facilitate the gas exchange necessary for photosynthesis.

Compound Leaf

A leaf whose blade is divided into multiple separate leaflets, providing the physiological advantage of greater photon capture in intermittently shady areas and reduced tearing damage in high winds.

Meristem

A persistent region of undifferentiated, perpetually dividing cells whose primary role is to produce more cells for primary and secondary plant growth.

Zone of Elongation

The area situated just behind the root apical meristem where cell lengthening primarily drives and pushes the root tip through the surrounding soil.

Pericycle

The outermost cell layer of the root stele, located directly interior to the endodermis, which gives rise to lateral roots.

Preprophase Band

A dense band of microtubules aligned parallel to the meristem surface in subsurface cells of the shoot apical meristem that marks the earliest physical site of a developing leaf primordium.

Stoma

A microscopic pore in the leaf epidermis flanked by guard cells that regulates transpiration and allows the diffusion of $CO_2$ into the photosynthetic tissues.

Apical Dominance

The hormonal suppression of lateral axillary buds by auxin synthesized in the terminal shoot tip, concentrating growth toward vertical height to increase light exposure in dense plant canopies.

Pinching Back

A horticultural technique in which terminal shoot tips are pruned away to eliminate apical dominance, thereby stimulating dormant axillary lateral buds to grow into branches.