Week 9 Bio 191 animals

Animal

Multicellular heterotrophic eukaryote with specialized cells and a fixed body plan

Determinate growth

Growth that stops once a defined body size and shape is reached

Embryonic development

Early developmental stage where the organism’s body plan is established

Locomotion

Ability to move at some point during the life cycle

Diploid dominant life cycle

Life cycle where the main organism is diploid and produces gametes

Choanoflagellates

Single celled organisms closely related to animals that resemble sponge collar cells

Ediacaran biota

Earliest known animal fossils dating to about 560 million years ago

Cambrian explosion

Period of rapid diversification of animal body plans around 542-488MYA

Poriferans (sponges)

Simple animals without true tissues that have porous bodies

Choanocytes

Flagellated collar cells in sponges that move water and capture food

Hox genes

Regulatory genes that control body plan and segment identity during development

Homeobox genes

Genes that encode transcription factors controlling developmental processes

Transcription factors

Proteins that regulate gene expression by turning genes on or off

Evo-devo

Study how changes in developmental genes influence evolution

Asymmetry

Body plan with no plane of symmetry

Radial symmetry

Body plan arranged around a central axis

Bilateral symmetry

Body plan with left and right mirror image halves

Cephalization

Concentration of sensory and nervous structures at the head

Germ layers

Embryonic layers that develop into tissues and organs

Ectoderm

Outer germ layer that forms skin and nervous system

Endoderm

Inner germ layer that forms digestive organs

Mesoderm

Middle germ layer that forms muscles and internal structures

Diploblastic

Having two germ layers; ectoderm and endoderm

Triploblastic

Having three germ layers; ectoderm, mesoderm, and endoderm

Coelom

Fluid filled body cavity fully lined by mesoderm

Acoelomate

Animal lacking body cavity

Pseudocoelomate

Animal with a body cavity not fully lined by mesoderm

Protostomes

Animals where the blastopore develops into the mouth

Deuterostomes

Animals where the blastopore develops into the anus

Blastopore

First opening formed during early embryonic development

Metazoa

All multicellular animals

Eumetazoa

Animals with true tissues

Parazoa

Animals with lacking tissues

Clade

Group of organisms that share a common ancestor

Role of hox genes in development

Hox genes control body plan and organization by regulating segment identity and positioning during embryonic development

Differences in animal body plans

Animal body plans differ based on symmetry, number of germ layers and presence or type of body cavity

Metazoan phylogenetic tree interpretation

The metazoan phylogeny shows evolutionary relationships based on traits like tissues, symmetry, and developmental patterns