From Worms to Arthropods Flashcards
Phylum: Annelida
- bilateral
- triploblast
- coelomate (unlike flatworms)
- protostomes
- body segmentation - serial repeition of functinoal units (compare with flatworms)
- earth worms, leeches
Body Segmentation
Serial repetition of functional units
Peritoneum
The peritoneum /ˌpɛrɨtənˈiəm/ is the serous membrane that forms the lining of the abdominal cavity or coelom in amniotes and some invertebrates, such as annelids. It covers most of the intra-abdominal (or coelomic) organs, and is composed of a layer of mesothelium supported by a thin layer of connective tissue.
Annelid Body Plan
- Coelom - acts as a fluid-filled (hydrostatic) skeleton
- Closed vascular system - transport vital gases, food and excretory products (greater potential for increased size)
- Ventral nervous system - nerve cord
- Movement - antagonistic circular and longitudinal muscles (helped by parapodia or chaetae)
Parapodia
(in a polychaete worm) each of a number of paired muscular bristle-bearing appendages used in locomotion, sensation, or respiration.
(in a sea slug or other mollusc) a lateral extension of the foot used as an undulating fin for swimming.
Aids movement in water
Chaetae
any of the chitinous bristles on the body of such annelids as the earthworm and the lugworm: used in locomotion; a seta.
Seta - is a biological term derived from the Latin word for “bristle”. It refers to a number of different bristle- or hair-like structures on living organisms.
Phylum: Annelids
Class: Polychaeta
- Marine worms
- Free-swimming and sedentary
- Have unjointed leg-like ‘parapodia’ on every body segment
- Reproduction - mostly sexual via spawning or hypodermic impregnation; some species hermaphroditic
- Trocophore larvae - free swimming cilliated larva
Hypodermic Impregnation
where the penis injects sperm into the body tissues and sperm migrates to the female reproductive tract.
Hermaphrodite
a person or animal having both male and female sex organs or other sexual characteristics, either abnormally or (in the case of some organisms) as the natural condition.
Phylum: Annelid
Subclass: Oligochaeta
- Earthworms
- Mostly terrestrial - live in soil (feed on organic matter)
- Can grow very long - Gipsland earthrworm, up to 3m
- Hermaphrodites but usually sexual reproduction
- React to vibrations e.g. thinks it’s rain, come up for water - have capacity to perceive environment
- ripple like movement due to chaetae
Earthworm Movement
- Chaetae
- longitudinal and circular muscles relax and contract alternately
Phylum: Annelid
Subclass: Hirudinea
- Leech
- Freshwater and terrestrial
- Mostly feed on vertebrate blood
- Saliva contains anti-coagulant proteins
- have thermo-sensors to detect prey
- coelom - usually reduced in size
- segmentation - found in nervous and excretory system only
- reproduction - internal fertilization (some use hypodermic impregnation)
Annelid Segmentation (leech)
- intestine - reduced segmentation
- Coelom - reduced (allows more space for muscles and intestine)
- suckers - feeding, anchoring and movement
Phylum: Arthropoda
- over 80% of species
- occupy all environments (marine, freshwater, terrestrial, subterranean, aerial)
- enormous range of behaviours and body forms
- split into 4 major sub-phyla
Characteristics of Arthropoda
- Bilateral
- Tripoblastic
- Coelomate
- Protostomes
- Body segmentation
- Also…not part of annelid characteristics
- moult (part of the ecdysozoa)
- hard exterior (exoskeleton)
Phylum: Arthropoda
Sub-phylum: Chelicerata
- terrestrial and marine
- four pairs of legs
- lack antennae
- modified mouthparts (chelicerae)
e. g. spiders
Phylum: Arthropoda
Subphylum: Myriapoda
- centipedes and millipedes
- myriapoda = many legs
- head and segmented body
- mandibles for feeding
- usually compound eyes
- terrestrial (live in leaf litter and soil)
- centipedes are carnivorous
- milipedes eat leaf matter
- odd number of segments
Phylum: Arthropoda
Subphylum: Crustacea
- mostly marine (few terrestrial: e.g. woodlice/slaters)
- two pairs of antennae, biramous appendages
- major component of plankton
- mostly omnivorour; some filter feeders; few carnivorour
- reproduction - sexes usually separate
- unusual forms - the hermaphroditic barnacle
Biramous Appendages
The appendages of arthropods may be either biramous oruniramous. A uniramous limb comprises a single series of segments attached end-to-end. A biramous limb, however, branches into two, and each branch consists of a series of segments attached end-to-end.
Phylum: Arthropoda
Subphylum: Hexapoda (Insecta)
- vast number of species and forms
- mostly terrestrial (why so few marine insects?)
Few marine insects as it would have to compete with crustacea
- reproduction - mostly sexual, although some species asexual
- characterised by evolution of wings and flights
- wing - stiff membrane of exoskeleton strengthened by “veins”
- unbranched limbs
- body divided into 3 sections
- 3 pairs of legs
- specialised mouth part
Evolution of insect flight
- most likely evolved from gills in aquatic forms
- traditionally thought wings evolved from structures that would help ‘gliding’
- evidence from stoneflies suggest early wings aid locomotion across water surface
Insect mouthpart diversity
- chewing e.g. grasshopper, cockroaches
- sucking e.g. mosquitoes
- siphoning e.g. butterflies
- sponging e.g. flies
Arthropods Success
- Exoskeleton
- exoskeleton composed on chitin
- made up of hardened plates, separated by soft membranes (permits movement)
- Advantages
- protection
- support for muscles
- prevent water loss
- can be adapted for unusual uses
Arthropods Success
- Diversification of segmentation
- Body segmentation shows fusion and loss of segments to varying extents
- Some loss of appendages as well
Arthropods Success
- Diversification of appendages
- many body segments bear different types of jointed appendages
Arthropods Success
- Advanced Nervous System
- antenna
- compound eye
- brain
- ventral nerve cord
- segmental ganglion
- Advanced Sensory structures
e.g. compound eyes, antennae
