Arthropoda Flashcards
What is the basics to the Phylum Arthropoda?
- Hard exoskeleton
- Jointed legs
- Many paired limbs
- Very successful phylum
- More than 80% of all described species are Arthropods (Most of these are insects)
- 3 germ layers
- Coelomate
- Mouth formed from blastopore
- Complete gut
- Mostly sexual reproduction
- Bilateral symmetry
What are the Subphylum’s to the phylum Arthropoda?
Chelicerata
Myriapoda
Crustacea
Hexapoda
What is the subphylum Chelicerata?
- Spiders, ticks, mites, horseshoe crab, scorpion
- 8 legs
- 2 tagmata (cephalothorax and abdomen)
- No antennae
- Most have 6 pairs of cephalothoracic appendages
1 pair of chelicerae (mouthparts)
1 pair of pedipalps (second pair of appendages)
4 pairs of walking legs
What is the subphylum Myriapoda?
- Millipedes and centipedes
- Number of legs is variable
- 2 tagmata (head and trunk)
- 1 pair pf antennae
- Paired appendages on most of trunk segments
What is the subphylum Crustacea?
- Lobsters, crayfish, shrimp, crabs, water fleas, copepods and barnacles
- 6 legs
- 2 tagmata (cephalothorax and abdomen)
- 2 pairs of antennae
- Appendages on each body segment (variable number)
- Only arthropod subphylum that is primarily aquatic
- Most free living, but some are sessile, commensal or parasitic
What is the subphylum Hexapoda?
- Mainly insects: butterflies, bees, wasps, flies, beetles, moths
- 6 legs
- 3 tagmata (head, thorax, abdomen)
- 1 pair of antennae
- Appendages are on the head and thorax
- Class Entognatha
small class
wingless
base of mouthparts enclosed - Class Insecta
enormous group
base of mouthparts visible
usually two pairs of wings on thorax
What are the adaptations of Arthropods?
1) Versatile exoskeleton
2) Segmentation and specialized appendages
3) Air piped directly to cells
4) Highly developed sensory organs
5) Complex behaviours
6) Trophic breadth through metamorphosis
Explain the exoskeleton
- External skeleton (called the cuticle in arthropods and nematodes)
- Cuticle is secretes by the underlying epidermis
- The cuticle contains chitin, a nitrogenous polysaccharide
What is the cuticle?
- Heavy (limits body size)
- Hard and waterproof (great protection)
- Thin and flexible between segments (permits free movement of joints)
- The cuticle is secreted not grown
What does moulting mean?
- Exoskeleton doesn’t expand, no room for growth
- To increase body size, arthropods must molt
- Moulting means shed old feathers, hair, skin or shell to make way for new growth
What is ecdysis?
Shedding of outer cuticle, as in insects or crustaceans
- a more specific term than moult - defining feature of the clade ecdysozoa
Explain segmentation
- Arthropods exhibit metamerism (segmentation)
- Segments often combined or fused into functional groups, called tagmata
- Appendages are also often differentiated (specialized for walking, swimming, flying, eating)
What is a tagmata?
Compound body section of an arthropod resulting from embryonic fusion of two or more segments
What are the types of circulatory systems?
Closed
Open
What is the closed circulatory system?
- Blood is contained within vessels
- Vertebrates and some invertebrates
What is the open circulatory system?
- Blood is confined to vessels in only a portion of circuit through body
- Blood mixes with interstitial fluids in the hemocoel
- Because it is mixed with fluid, it is properly called hemolymph
- Arthropods and some molluscs
What is their respiration?
- In vertebrates, oxygen is carried and delivered to cells through the blood
- Most land arthropods use a system of air tubes called tracheae for gas exchange (hemolymph does not carry oxygen in these species)
- The tracheae branch to more and more narrow tubes
- They deliver oxygen directly to tissues and cells through holes or valves
- Aquatic arthropods breathe mainly through gills
Explain the highly developed sensory organs
- Compound eye
- Some have antennae
- Keenly alert to environmental stimuli
Explain their complex behaviours
- Most behaviour is innate (unlearned)
- Many arthropods also demonstrate learned behaviours
- Social insects are capable of most basic forms of learning used by mammals, but not of insight learning
What is insight learning?
When faced with a new problem, can organize memories to construct a new response
What is metamorphosis?
- Sharp change in form during postembryonic development
- Occurs in any species with indirect development
- Particularly striking in insects
- Larval and adult forms live in different niches; have difference sources of food, experience different selective pressures
What are the types of development?
Ametabolous (direct)
Hemimetabolous (indirect)
Holometabolous (indirect)
Explain ametabolous development
- Direct development
- Young or juveniles are similar to adults except in size and sexual maturation
- A few (primitive wingless) insects exhibit this type of development
- Egg, juvenile, adult
Briefly explain the indirect development
- Passes through larval stage capable of feeding itself
- Undergoes metamorphosis to reach adult stage
Explain hemimetabolous development
- Incomplete metamorphosis
- Wings develop externally as budlike growths
- Nymph resembles adult in form and eating habits
- Nymph differs from adult in size, body proportion, and colour pattern
- Egg, nymph, adult
Explain holometabolous development
- Approx 88% of insects undergo this
- Complete metamorphosis
- Separate stages for growth (larva), differentiation (pupa), and reproduction (adult)
- Larva are wormlike
- Pupae are usually inactive (non feeding) and enveloped by a case
- No further moulting occurs in adult stages
- Egg, larva, pupa, adult
