Lecture 4 Flashcards
what are the characteristic features of the different lineages of Arthropoda?
Amount of walking legs:
- Trilobita=Thorax and abdomen segments bear pairs of walking legs
- Chelicerata= 4 pairs of walking legs
- crustacea= number of legs depends on group. Decapoda have 5 pairs
- Myriapoda =MANY legs (centipedes and millipedes)
- Hexapoda= 6 walking legs
what do the Ecdysozoan phyla have in common, and how do they differ?
In common: Ecdysis- protective outer that occasionally needs to be shed.
Differ:
*nematoda- pseudocoelomate
*onychophora&;arthropoda- coelomate; segmented
How does segmentation in Arthropoda differ from that in Annelida?
Arthropods are invertebrates containing a segmented body , an chitinous exoskeleton and paired appendages. Don’t have metameric segmentation.Body segments= no internal separation and are often fused, reducing the number of segments (e.g. cephalothorax and abdomen)
Annelida are worms segmented by transverse rings and have metameric segmentation.
what are the advantages (5) and disadvantages (2) of having a hard exoskeleton or thick cuticle?
Advantage:
- waterproof
- protection against predators
- attachment sites for muscles-allows for highly co-ordinatedmovement and patterns of locomotion that are more precise than in soft bodied organisms with hydroskeletons
- gives support against gravity
- prevents drying out
Disadvantage:
- non-expandable, limiting growth (ecdysis-shedding)
- O2 can’t be taken up across the skin
Ecdysozoan protostomes:
have protective outer covering that occassionally needs to be shed.
3 phyla:
and which pseudocoelomate , coelomate, segmented
- nematoda : pseudocoelomate, unsegmented
- onychophora: coelomate, segmented
- arthropoda: coelomate, segmented
what are the 5 subphyla of arthropods
- Trilobita
- chelicerata
- crustacea
- myriapoda
- hexapoda
6 traits that put arthropoda where they are in the phylogenetic tree (common names and scientific)
5 and 6 are just traits
- Eumetazoa (tissues)
- Bilateria (Bilateral symmetry & triploblastic)
- Protostomia (schizocoelomate)
- Ecdysozoa (Ecdysis)
- segmentation
- repeated unspecialised appendages per segment
2 main difference between Annelida and Arthopoda
Both Annelida and Arthropoda are composed of segmented animals. The main difference between Annelid and Arthropoda is that Annelida consists of a hydrostatic skeleton whereas Arthropoda consists of an exoskeleton made up of chitin.
Arthropoda also have compound eyes while annelida do not.
locomotion of annelida vs arthropoda
Annelida:Don’t have legs but they have chaetae that may develop in parapodia for locomotion.
Arthropoda: Have segmented appendages for locomotion.
what is metameric segmentation
The repetition of organs and tissues at intervals along the body of an animal, thus dividing the body into a linear series of similar parts or segments (metameres). It is most strikingly seen in Annelida.
what are the 3 phyla of ecdysozoan
- Nematoda
- onychophora
- arthropoda
what are the 2 types of Chelicerata (sub phylum of anthropoda)
- Arachnids
2. merostomata
3 types of crustacea (sub phylum of anthropoda) and examples
- decapoda (crabs, lobsters, shrimps)
- cirripedia (barnacles)
- copepoda (copepods)
2 types of myriapoda
- millipede (2 pairs of walking legs on most of its segments)
- centipede (1 pair of walking legs on most of its segments)
a grasshopper falls under what subphylum of anthropoda?
hexapoda
what part of a parasitic nematode’s anatomy protects it from the digestive enzymes of its host
cuticle
if an arthropod’s rigid exoskeleton cannot be expanded, how does the animal grow
they grow a new, soft exoskeleton inside the existing one. After shedding the old exoskeleton, they grow to a larger size by expanding the new exoskeleton with either water or air before it hardens
how do the number of body regions and the appendages differ among the 4 groups of living arthropods
They differ in how they have become fused.
- Chelicerates have a fused cephalothorax and an abdomen
- crustacean show variable patterns, but mainly have fused cephalothorax and an abdomen
- Myriapods have a head and a trunk
- Hexapods have a separate head, thorax, and abdomen
how do the life stages differ between insects that have incomplete metamorphosis and those that have complete metamorphosis
insects with incomplete metamorphosis hatch from their eggs as wingless nymphs, which vary in how closely they resemble adults; nymphs then undergo metamorphos into adult form.
Insects with complete metamorphosis hatch from from eggs as larvae, which are always very different from adults. After becoming a pupa, their cells and tissues are reorganised into the adult form
metameric segmentation
The repetition of organs and tissues at intervals along the body of an animal, thus dividing the body into a linear series of similar parts or segments (metameres).
It is most strikingly seen in Annelida.
