Chapter 20 - Biodiversity of Inverts Flashcards
What are the basic animal characteristics?
- eukaryotic
- multicellular
- heterotrophic
- contain muscle cells for movement
- collagen to hold cells together
Standard animal life cycle
- Male and females produce gametes by mitosis
- Sperm + egg = diploid zygote
- Zygote divided by mitosis (8 cell stage)
- Blastula stage (hollow cell ball)
- Gastrula stage (endoderm, ectoderm, mesoderm)
- Many animals directly develop into adults, but some go through a larval stage.
- If they go through the larval stage they must pass through metamorphosis.
Ectoderm
In the gastrula stage;
The ectoderm are the layer of cells on the outside of the gastrula.
These cells become the outer covering of the animal (such as skin)
Endoderm
In the gastrula stage;
The endoderm are the cells on the inside of the gastrula.
These become the cells which line the digestive tract.
Mesoderm
In the gastrula stage;
The mesoderm cells are the middle cells of the gastrula.
These cells become muscle and most internal organs.
How many phyla of animals are there?
35
(and 34 of them are invertebrates)
Radial symmetry
Typically found in more primitive animals.
They have a body plan than radiates from the centre of their body. (They have a top and a bottom, but not a left or a right)
Ex. Starfish
Bilateral symmetry
Found in more developed animals
These animals contain a distinct left and right sides. (Each side is like a mirror of the other side)
Ex. Lobster
Coelom
A fluid filled body cavity between the digestive tract and the outer body wall. Lined on both sides by the mesoderm
Function: to cushion the organs and allow them to grow.
Ex. A segmented worm
Pseudocoelom
The presence of a coelom but it’s only line by the mesoderm on one side.
Ex. A round worm
Acoeolomate
Contains no body cavity
Ex. A flatworm
Parthenogenesis
Producing diploid eggs that do not need to be fertilized
Seen in Rotifera
Cryptobiosis
A state of extreme inactivity in response to bad environmental conditions.
Seen in tardigrades:
They will lose 99% of their water and have a metabolic rate of 0.01%. They can withstand extreme temps and even the vacuum of space.
Gastropods
A type of mollusc which only contains their stomach and foot (sometimes a shell)
Ex. Slugs, snails
Bivalves
A type of mollusc which contains shells that divide in half that are hinged together
Ex. Clams, oysters
