Week 7 Flashcards
What are the Nematoda (Phylum)
“Nemato = threadlike”
Roundworms (25,000 species recognised – but may be 1 million)
Two types: free living, parasites
Sexually reproduce with separate sexes
Characteristics of the Phylum Nematoda?
Bilateral symmetry, cylindrical body with tapering ends, pseudocoelomates - there is a distinct head end
Body plan of the Phylum Nematoda?
- Psedocoelomates, internal cavity but internal organs not surrounded by mesoderm
- Tubular – mouth at blunt end starts the complete gut
What are the two types of body plan for Phylum Nematoda?
Psedocoelomates
Tubular
What does the multi-layered cuticle help with?
(Phylum Nemotoda body plan)
helps maintain high pressure inside a hydrostatic skeleton
(Muscles not antagonistic – they twitch side-to-side and hydrostatic skeleton pulls them into shape)
What are the two types of lifestyle Phylum Nematoda have?
Free living or parasites
Free living nematodes?
marine, freshwater, terrestrial
found in all habitats from deserts to polar regions
90% of animals on the seabed
may account for 80% of all individual animals
In soil, most feed on bacteria and fungi
Most free-living species are microscopic
Example of a potato cyst nematodes?
Globodera pallida
G. rostochiensis
Root feeders, important plant pest - estimated to destroy 12% of world’s crops annually
Examples of Nematodes that are parasitic?
Virtually all animal and plant groups have nematode parasites
E.g. Ascariasis, Guinea Worms, pinworms
What is Elephantiasis caused by?
- Caused by infection with Filariasis type Nematodes
- Infects lymphatic system and causes swelling
Why are Caenorhabditis elegans important (Phylum Nematodes)?
- important model for cell and developmental biology
- First multicellular organism to have its genome sequenced
- A very rare example of an androdioecous species – most are hermaphrodites, but males exist (rare) when stressed
What is a hermaphrodite?
An organism with sex organs that are not clearly male or female
How do Nematoda grow?
Have thick external cuticle that needs to shed to grow
What are the Phylum Echinodermata?
“Echin = spiny, derma = skin”
Sea lilies, sea urchins, starfish or sea stars and sea cucumbers
All marine organisms
Characteristics of the Phylum Echinodermata?
Bilateral symmetry in larvae but 5-fold radial symmetry in adults, coelomates
Sexual reproduction with separate sexes, free swimming larvae
What are the body plan types for Phylum Echinodermata?
- Radial body symmetry (pentatomerous)
- Thin epidermis covering a endoskeleton (calcareous plates) and external spines.
- Water-vascular system (internal canals and external tube feet)
Examples of Echinodermata diversity?
Class Crinoidea: Sea lilies, feather stars
Class Asteroidea: Starfish
Class Ophiuroidea: Brittle stars
Class Echinoidea: Sea urchins, sand dollars
Class Holothuroidea: Sea cucumbers
What is the growing process of Phylum Arthropoda?
Moulting
Outline the process of moulting?
o Endocuticle separates from the epidermis, which secretes a new epicuticle
o As new exocuticle is secreted, moulting fluid dissolves old endocuticle and solution products are reabsorbed
o At exolysis, the old epicuticle and exocuticle are discarded
o In postexolysis new cuticle is stretched and unfolded and endocuticle is secreted
What are the 4 types of gas exchange that can occur in Arthropoda?
Through the skin (small organisms),
Gills (aquatic, crustaceans)
,
Book lungs (terrestrial, scorpions and spiders),
Tracheae (terrestrial, insects, millipedes)
What are the stages of moulting in Arthropoda?
Intermoult,
Premoult,
Moult,
Postmoult
What are the advantages of a hard exoskeleton in Arthropoda?
Independence from the environment
Protection
Reduce water loss
More efficient locomotion (muscles)
What are disadvantages of a hard exoskeleton in Arthrodpoda
Limit growing (needs to be shed)
Limit gas exchange (need for respiratory organs)
Limit movement (flexible between segments & appendices)
What do hard exoskeletons consist of? (Phylum Arthropoda)
Chitin (a polysaccharide) and proteins.
Segregated by the epidermis
What are the three sensorial organs in Arthropoda?
Mechanoreceptors
(touch and vibrations)
Chemoreceptors
(smell and taste)
Photoreceptors
(ocelli & compound eyes)
Characteristics of Phylum Arthropoda?
“Arthro” = joint, “poda” = feet
> 1M species
Bilateral symmetry, celomates
Exoskeleton
Segmented body
Paired jointed appendages
Respiratory, excretory, blood & sensorial systems well developed
Sexual reproduction with separate sexes