Animal phylogeny Flashcards
What is an animal?
Feeds on organic matter (but so do fungi)
Typically has specialised sense organs & nervous system – able to respond rapidly to stimuli (but sponges move slowly)
Typically able to move around – sometimes restricted to a stage in their life cycle. Lots of animals are sessile at stages in their life cycle
Eukaryotic and lack rigid cell walls
Usually heterotrophic, highly responsive, motile and multicellular.
Epithelial cell sheets.
Sperm and eggs
Significance of the epithelial cells in animals?
Form watertight sheets.
Allow ion concentrations to be maintained in different areas of the body.
Tough and can be folded to make complex sheets.
Significance of differently sized gametes in animals?
Difference in investment of resources, having a massive effect on subsequent evolution of animal behaviour.
Where do animals fit into the tree of life?
One very diverse clade in the eukaryotes. Multicellular.
Closest relatives: Choanoflagellates.
Group of microscopic single celled protists, marine and freshwater, which feed on bacteria.
Long flagellum, surrounded by a collar of actin supported tentacles and a cell body.
Some can secrete a glass basket and some form simple colonies.
Definition of multicellular?
Possessing different types of cells
Why did multicellularity evolve?
Ecological – is it better to be big? Could swim further, set up bigger water current to catch more bacteria, harder to be eaten. First would still have been very small
Cell biology – Flagellar constraint? Animals retract cilia before breaking down nuclear membrane and dividing as the centriole and basal body are the same.
In a single celled organism, it wouldn’t be able to move towards food whilst dividing.
Multicellularity allows some cells to divide whilst others wave flagellum for swimming or feeding.
Ecological – self cannibalism? If you eat your sister cells whilst food is scarce can grow back when the environment changes.
Difference between taxonomy and phylogeny?
Phylogeny – evolutionary trees, working out who is related to whom.
Can switch the branches around to show same relationships
Monophyletic group = clade
Can only do phylogeny with things that evolve
Taxonomy – classification
Dividing up things into sets, and those into smaller subsets
Making up names for each set/subset
Taxonomy should use phylogeny
What are diploblasts?
Diploblasty is a condition of the blastula in which there are two primary germ layers: the ectodermand endoderm.
Cnidarians
The endoderm allows them to develop true tissue. This includes tissue associated with the gut and associated glands. The ectoderm, on the other hand, gives rise to the epidermis, the nervous tissue, and if present, nephridia.
What are triploblasts?
All the more complex animals (from flat worms to humans) are triploblastic with three germ layers (a mesoderm as well as ectoderm and endoderm).
The mesoderm allows them to develop true organs.
What is an acoelomate?
An acoelomate is defined as an animal that does not possess a body cavity. Unlike coelomates (eucoelomates), animals with a true body cavity, acoelomates lack a fluid-filled cavity between the body wall and digestive tract.
Platyhelminthes, Cnidaria
What is a coelomate?
Coelomate animals or Coelomata (also known as eucoelomates — “true coelom”) have a body cavity called a coelom with a complete lining called peritoneum derived from mesoderm (one of the three primary tissue layers).
Molluscs, Annelids, Chordates
What is a pseudo-coelomate?
Pseudocoelomate animals have a pseudocoelom (literally “false cavity”), which is a fluid filled body cavity. Tissue derived from mesoderm partly lines the fluid filled body cavity of these animals. Thus, although organs are held in place loosely, they are not as well organized as in a coelomate.
Nematodes
Phylogenetic map of protostomes and deuterostomes?
Differences between protostomes and deuterostomes?
