Metazoa Flashcards
Define metazoa
Multicellular, eukaryotic heterotrophs with an extracellular matrix (ECM). Organised tissue allows motility.
What is an extracellular matrix (ECM)?
A connective tissue between cells, comprising of collagen, proteoglycans, and adhesive glycoproteins.
What does the ECM allow?
The migration of metazoan cells through the mesenchyme (connective tissue), which is important in development.
What is the differences between protozoans and metazoans?
Protozoans are usually unicellular and metazoans are multicellular.
Define the Plant kingdom
Multicellular autotrophs with chloroplasts and cellulose cell walls
Define the Fungi kingdom
Multicellular and unicellular autotrophs with chitin cell walls
What are choanaflagellates the sister taxon to?
Metazoa
Describe choanaflagellates
Can be free-living or flagellum propelled and can form colonies that can act together.
What is the word for a colony that acts together?
Protomulticellularity
What four groups are included in metazoa?
Porifera, ctenophora, cnidaria, bilatera
When are porifera motile and when are they sessile?
Motile as larvae and sessile as adults
Name four things that porifera don’t have
Organs, nerve, muscles, or symmetry
Describe the tissue organisation of porifera
Incipient tissue organisation (external epithelium)
Name a feature of porifera
Choanocytes
What are choanocytes?
Flagellated cells creating internal water currents
How are ctenophores motile?
From groups of cilia (ctenes)
What type of symmetry do ctenophores have?
Radial
What type of digestive system do ctenophores have?
Through gut (diploblastic)
Name three characters of ctenophores
Muscles, nerves, and some sensory capabilities
Describe placozoa
A phylum of small, flat ‘animals’. They are aggregates of cells with no organs.
How many species are there is the placozoa phylum?
3
How do placozoa reproduce?
Asexual budding
Describe how placozoa are heterotrophic
They digest detritus on their ventral system
How do placozoa move?
They have a ciliated epithelium
Name two things that placozoa do not have
Tissues and symmetry
What phylum was traditionally seen as the sister taxon to all other animals?
Porifera
Why were porifera traditionally seed as a sister clade to all other animals?
Their morphology
What phylum is now seen as the sister taxon to all other animals?
Ctenophora (using phylogenomics)
What are the two models of molecular evolution?
Simple and complex
Describe the simple model of molecular evolution
Changes between AGCT have equal probability and rate
What can AGCT sites be?
Homogenous (equal rates of change) or heterogenous (vary in rates of change and evolution)
Describe long branch attraction
When taxa appear to be more closely related because they have both undergone a large amount of change
