Animal Phylogeny and Development Flashcards

Flashcards covering the vocabulary of animal phylogeny, symmetry, embryonic development stages, and developmental genetics as presented in the lecture.

Choanoflagellata

A unicellular, colonial, and flagellated protist group that serves as the sister group to animals.

Bilateria

A major group of animals characterized by bilateral symmetry, 3 germ layers, and a head-tail axis.

Protostomia

A clade of bilaterians in which the blastopore developed during gastrulation becomes the mouth.

Deuterostomia

A clade of bilaterians in which the blastopore developed during gastrulation becomes the anus.

Lophotrochozoa

A subgroup of protostomes that includes animals like molluscs and annelids, often characterized by trochophore larvae or a lophophore.

Ecdysozoa

A subgroup of protostomes, including nematodes and arthropods, characterized by an exoskeleton and the process of moulting.

Cephalization

The concentration of sensory organs and nervous tissue at the anterior end or head, correlated with bilateral symmetry.

Diploblast

Animals such as Cnidaria and Ctenophora that possess two germ layers (or sometimes three) and typically exhibit radial symmetry.

Xenacoelomorpha

A phylum of animals with a new body plan that was recently recognized in 2011.

Zygote

The product of the fusion of two haploid ($n$) gametes, restoring diploidy ($2n$).

Morula

A compact conglomerate of cells formed during the early stages of cleavage in an embryo.

Blastocoel

The cavity that forms inside the embryo to initiate the blastula stage.

Gastrulation

A key event in embryogenesis where cells migrate through the blastopore into the blastocoel to establish germ layers.

Ectoderm

The outer germ layer that gives rise to the skin and the nervous/sensory system.

Mesoderm

The middle germ layer, found only in Bilateria, which develops into muscles, the circulatory system, blood, and various organs.

Endoderm

The innermost germ layer that gives rise to the digestive system, including the gut and associated organs.

Organogenesis

The process of formation of the organs from the specific germ layers.

Trochophore

A typical larval stage found in molluscs and annelids.

Nauplius

A typical larval stage characteristic of crustaceans.

Pax6

A conserved gene within the genetic toolkit that controls eye development across different animal phyla.

Homeobox

A sequence of approximately $180$-base pairs ($\text{bp}$) that encodes the DNA-binding homeodomain in homeotic genes.

Hox genes

A group of homeobox genes that control positional identity along the body axis in all bilaterians.

Homeotic transformation

A mutation in Hox genes that results in the change of one body part into another, such as legs growing instead of antennae.

Antennapedia

A specific mutant in Drosophila where flies grow legs in the place of antennae due to Hox gene mutation.

Ultrabithorax (Ubx)

A Hox gene that patterns body regions and, in insects, suppresses leg formation in the abdomen by repressing the Distalless (Dll) gene.