Introduction To Animals And Non Bilaterians Flashcards
What are Choanoflagellates
A unicellular sister group to animals (protists)
What is the group metazoa
Metazoa = animals
What ambiguities remain when looking at the evolutionary history of animals
Early branching taxa are the most ambiguous, we don’t know if sponges or placozoans came first
What does diploblast mean
2 germ layers and radial symmetry
What is meant by bilateria
3 germ layers and bilateral symmetry
Why was the development of a mesoderm layer in bilaterians important
It allowed for the development of specialised internal structures and organs
What is the morula
A compact cluster of cells formed after the zygote has started to decide
What is the blastula
A hollow ball of cells with an inner cavity (blastocoel) formed during early embryonic development
What happens during gastrulation
Cells migrate through the blastopore into the blastocoel forming either 2 (non bilateria) or 3 (bilateria) germ layers: the ectoderm, mesoderm and endoderm
How are protostomes and deuterostomes seperated
In deuterostomes the blastopore becomes the anus
In protostomes the blastopore becomes the mouth
What is meant by organogenesis
The formation of organs
What are hox genes
Highly conserved genes that control positional identity within an animals body plan
What groups are in the non bilaterians
Ctenophores
Placazoans
Porifera
Cnidaria
What is the phylogeny of ctenophores
Fully marine
250 species
Earliest group to split from other animals
What is the body plan of ctenophores
Diploblastic (2 germ layers)
Complete gut
Hermaphroditic
Uncentralised nervous system
What is the body plan of Porifera
Simplest animals (sponges)
No symmetry
Most body cells are totipotent
Filter feeders
Water is drawn into the sponge via beating flagella
What is the reproductive cycle or Porifera
Hermaphoridtic
Can reproduce asexually through budding and splitting
Sperm is transported between individuals by water currents
Fertilised eggs develop into larvae
What is the body plan of placozoans
Flat asymmetrical disks
Fully marine
Made up of two layers of cells
No mouth, gut or nervous system
Structural simplicity may have been secondarily derived
What are eumetazoans
Cnidaria + bilateria
Must have body symmetry, a gut, and a nervous system
What is the gastrovascular cavity in cnidarians responsible for
Digestion, circulation, gas exchange and provides a hydrostatic skeleton
What are the stages in the cnidarian life cycle
Medusa stage: free swimming, produces gametes for sexual reproduction
Polyp stage: attaches to substrates whilst it develops
What is a nematocyst
The specialised stinging cells
What are the subgroups of Cnidaria
Anthozoa: sea anemones and corals
Scynophozoa: true jellyfish
Hydrozoa: siphonophores, colonial hydroids
Cubozoa: box jellyfish
