invertebrates Flashcards
What are ecdysozoans?
group of animals that grow by ecdysis (moulting)
What is a coelom
Fluid filled cavity that largely acts as a hydroskeleton
Lines with mesoderm and place for gas exchange and internal organs
What are Hox genes
Group of genes common among all animals that designates regions of body plans along head to toe axis
What is Cephalization?
The centralization of sense organs and nervous control at the anterior end of the body. Thus, creating a brain and head.
Protostome
Mouth appears before anus during development of blastopore. Coelom is formed from splitting of mesoderm.
Deusterostomes
First opening during development of blastula forms anus and coelom forms from outgrow of primitive gut.
Lophotrocozoa
-Second largest group after arthropods
-Triploblastic and bilaterally symmetrical
ie, annelids and mollusks
What are the 7 main characteristics of animals
- Eukaryotic
- Multicellularity
- Heterotrophic
- No cell wall
- Motile at some life stage
- Have diploid somatic cells
- Diplontic life cycle
How is multicellularity an advantage?
- Allows organism to grow therefore have a longer lifespan
- Cells carry out specific functions
- Cells are small- better function because there is a high surface area to volume ratio
Types of skeletons
- Hydrostatic (jellyfish, octopus)- limited possibility for attachment
- Exoskeleton- molt
- Endoskeleton
What is the closest living relative to animals?
Choanoflagellates
Proof that animals are monophyletic
- Similar gene sequences
- Similar extracellular matrix
- Unique junctions
Germ layers
- Endoderm (inside)
- Mesoderm
- Ectoderm
Triploblastic vs Diploblastic
Triploblastic= three germ layers Diploblastic= Two germs layers (no mesoderm)
Sponges
- Have endoskeleton (spicules for support)
- Sessile as adults motile larvae
- Filter feeders (choanocytes)
- Can be asexual and reproduce via fragmentation or internal budding (gemmules)
- Can reproduce sexually by being hermaphroditic BUT one at a time- sperm but find another “female” sponge
What is the name for jellyfish, anemones, corals…
Cnidaria
Cnidaria characteristics+
When do they stop development?
-Diploblastic
-No brain or ganglia
-Stop development at gastrula stage
Where mesoderm is we have the mesoglea
-Polyp is sessile form and medusa is motile form
Four main groups of Cnidarians
- Hydrozoa (freshwater jellyfish, tentacles contain cnidocytes)
- Scyphozoa (true jellyfish, large amount of mesoglea)
- Cubozoa (box jellyfish-fatal sting)
- Anthozoa (coral, anemones- often form mutualistic relationships)
Nervous system of Cnidarians
Little to no integration or processing of signals
- However, radial symmetry can be an advantage because sensory info comes from any direction
- Radial symmetry can be disadvantage because it does not favour locomotion
3 types of body cavity plans
1) Coelomate - true coelom entirely surrounded by mesoderm (most triploblastic organisms)
2) PseudoCoelomate- “False Coelom” Mesoderm lines outside of pseudocoel
3) Acoelomate- NO CAVITY- Solid except for digestive space ie. flatworms
Two ways to make a Coelom
1) Schizocoely- splitting of mesoderm within protostomes
2) Enterocoely- mesoderm forms pockets from gut within deuterostomes
What is name for organisms such as flatworms? What are their main characteristics?
Platyhelminthes
- triploblastic, acoelomate, bilateral symmetry
- Directed movement due to cephalization
- Can be free living or parasitic
What are the three groups within Lophotrocozoans?
-Annelids, Mollusks, Rotifers
Advantages of segmentation and example of Lophotrocozoans that have it
Annelids have segmentation and closed circulatory system
- Multiple copies of organs
- Efficient nervous control
- Increases body size
- Regeneration
What are Trocophore
Larvae form of lophotrochozoans that are small translucent and free swimming
What are Radula
Radula are small tooth-like structures that most mollusks have other than bivalvia
Main mollusk groups
- Polyplacophora “many plates”
- Bivalvia ie Scallops (have siphon) for water flow-Filter feeders
- Gastropoda (snails) (dioecious or hermaphroditic)
- Cephalopods - Squids- large head reduced foot. Females die after laying eggs, No trocophore
What is hemocoel?
Body cavity in arthropods that contains blood or hemolymph. Part of circulatory system.
What is cryptobiosis?
Physiological state in which metabolic activity is reduced to an undetectable level. Used to survive extreme conditions
Types of ecdysozoa and characteristics
- Nematoda (round worm) mainly parasitic, can sustain the extreme
- Tardigrada (water bears) Go into cryptobiosis to survive the extreme
- Onychophora (velvet worms) segmented, spit really far for defense
- Arthropods MOST DIVERSE EUKARYOTIC GROUP
Characteristic features of Arthropods
- Segmented body
- Jointed appendages
- Highly developed sense organs (eyes of a fly)
- Rigid exoskeleton
Advantages and Disadvantages of an exoskeleton
Advantages: -Physical protection and support -Location of pigment (camo or sexual selection) -faster locomotion Disadvantages: -Inflexible -Heavy -Growth is periodic rather than continuous (wait until shedding of shell) -Requires energy -No respiration through skin
Types of metamorphosis
Metamorphosis enables change in morphology
-Incomplete metamorphosis: gradual change
(egg -> nymph -> adult)
-Complete metamorphosis: specific abrupt morphological changes in which morphology is fully altered
(egg -> larva -> pupa -> adult)
What hormones regulate moulting? How was this discovered through the experiment on R. prolixus?
-The heads of the same R. prolixus were cut off within the hour of feeding and within two weeks of feeding. The R. prolixus that got it’s head cut off right away did not moult.
This experiment led to the conclusion that the hormone that triggers moulting is in the head.
PTTH (in head) –> Ecdysone( in prothoracic gland)
Phenotypic Plasticity
Ability of one genotype to produce more than one phenotype when exposed to a different environment.
Parthenogenesis
Form of asexual reproduction in which embryo develops without fertilization by sperm.
Four majors arthropod groups
- Myriapods (millipedes, centipedes…)
- Chelicerates (6 pairs of appendages, separate sexes, pedipalps)
- Crustaceans ( PARAPHYLETIC) can reproduce by cyclical parthenogenesis
- Insects Wings come from crayfish gills, unique trait is their external mouth parts
Respiratory system of arthropods
- Insects and myriapods have tubular tracheae instead of lungs called spiracles
- Crustaceans breathe through gills
- Chelicerates breathe through book lungs or gills
Arthropod circulatory system
Open (hemolymph fills cavity)
One way valves.
Sexual Reproduction of Arthropods
Most arthropods are dioecious, most lays eggs. Some (like scorpions), care for their young
What are spermatophores?
Packets of sperm used by some arthropods when sexual reproduction isn’t fully internal. (may also be external in water, but this case doesn’t require spermatophores)
What is a nemotocyst?
Spear like structure of most cnidarians
