Block 4 + 5 - Animal development Flashcards
What are invertebrates?
Not a meaningful group, they have little in common aside from lacking a spine.
What is a phylum?
Phenetic:
Animals with fundamentally similar body parts. Different phyla show fundamentally different body plans.
Phylogenetic:
Major clades - based on genetic relatedness
What are the 4 fundamental body plasn features?
- Body symmetry (radial vs bilateral)
- Number of germ layers (diplo- vs triploblast)
- Kind of body cavity
- Development fate of blastopore (proto vs deutrostomes)
What are the adaptive values of radial and bilateral symmetry?
Radial:
Adaptive for sessile or slow-swimming life style. Food and threats can come from any direction
Bilateral:
Adaptive for life on the move - goes in hand with cephalisation
What is a body cavity?
- A fluid filled space between ectoderm and endoderm
- Blastocoel: primary cavty within the blastula
- Coelom: secondary cavity within the mesodermal tissue that is lined with a mesodermal epithelium = peritoneum
What is a coelomate?
Have a true coelom, a body cavity completely lined with tissue derived from the mesoderm.
E.g. earthworms
What is a pseudoceolomate?
Have a body cavity lined by tissue derived from the mesoderm AND endoderm.
E.g. roundworms
What is an acoelomate?
Lack a body cavity between the digestive cavity and outer body wall.
E.g. planarians
What is the importance of a body cavity?
- Cushions suspended internal organs
- Decouples growth and movement of organs from outer body wall
- Hydrostatic skeleton
What are proifera?
Animals without tissues:
. no nerve cells
. no muscles
. no germ layers
. no organs
. no planes of symmetry
- 5,500 species
E.g. sponges
What is the basic form and how do proifera fees?
Filter feeders with no mouth:
Pores for water intake
Osculum = outlet
unidirectional water flow - 1x body volume every 5 seconds
Central cavity = spongoceol
Outside = layer of pinacocytes (pinacoderm)
Inside = choanocytes or collar cells (choanoderm)
What are choanocytes?
Flagellum surrounded by a colar or micro milli.
Drive the water current through the sponge.
Food partucles are captured by the colar and phagocytosed
What is the body structure of a sponge?
Main body - mesohyl = acellular protein gel matrix with scattered mobile cells
Reinforced by skeletal elements:
- protein fibres: spongin
- mineral spicules: either calcium carbonate (calcite) or sillica
Explain the movement of a sponge
- Can slowly change shape
- Can close/ open pores to regulate water flow
- Some can move on substrate: 1-4mm/ day
What are eumetazoa?
Distinctive tissues including nerves and muscles.
Gastrulation producces germ layers:
- endoderm; lines gut cavity
- exoderm; covering the outer surface
- +/- mesoderm
What are cnidaria?
Metazoa without mesoderm
- 10,000 species
Mostly marine - radial
- mouth sirreounded by tentacles; carnivorous (tiny crustaceans)
- no seperate anus
- no brain (diffuse nerve net coordinates movements)
- dipoblastic (but with three layered body wall)
- Epidermis; outer epithelium
- Gastrodermis; inner epithelium (coelenteron)
- Mesoglea; acellular emebrane or jelly-like matrix (not a tissue)
Two body types:
- Polyp - sessile, tube with mouth up, thin mesoglea
. asexual, budding to generate medusa
- Medusa - swimming, umbrella with mouth down, thick mesoglea
. sexual, generates egg and sperm. Planula larva settles and develops into polyp
Main groups:
- Hydrozoa; hydroids (often colonial)
- Scyphozoa; jellyfish (medusoid, solitary)
- Anthozoa; polypoid (coral, sea anemones)
What is a cnidocyte?
Unique to cnidarians
- particularly on tenticles
Trigger hair (cnidocil) - fired when touched
- nematocyst: pressurised stinging structure with toxins
What are bilateria?
The rest of the animal kingdom
bilaterally symmetrical
with mesoderm (triploblastic)
How do you differentiate between tooth types?
- Incisors (I)
- Canines (C)
- Premolars (P)
- Molars (M)
Dental formula:
Upper jaw, carnivore - e.g. I3, C1, P4, M2
Upper jaw, herbivore - e.g. I0, C0, P3, M6
Both jaws e.g. I3/3, C1/1, P4/4, M2/2 (can be summed and multiplied by 2 to give total number of teeth)
What are the three major clades of mammals?
1) Monotremes: egg-laying mammals. 5 species
2) Marsupials: with pouch = marsupium. 330 species
3) Placentalia: placenta and umbilical chord. ~5000 species
What are monotremata?
- Confined to Australia and New Guinea
- Eggs, but nurse their young with milk
- No teeth as adults:
. Platypus, Fam. Ornithorhynchidae: 1 species
. Echidna, Fam. Tachyglossidae: 4 species
What are marsupialia (metatheria)?
With marsupium = pouch
- kangaroos and wallabies
- koalas, wombats, opossums
In Australasia, New Guinea and the Americas
- distribution reflects geology at the time of their evolution
What are eutheria (placentalia)?
The rest of the mammals and the most diverse clade
What are eutheria (placentalia)?
The rest of the mammals and the most diverse clade
