Anthropods Flashcards
(23 cards)
What are chelicerates?
-100,000 species
-ancient group of anthropods
-includes horseshoe crabs, sea spiders and arachnids
-the body has 2 regions: cephalothorax (appendages) and abdomen w no appendages
-mostyl predators
-have no jaw (mandibles) and no antenna
-sexes are separated (internal fertilization)
-expel digestive enzyme into the prey bc they cannot digest solids
6 pairs of appendages:
-#1 chelicerae = fangs can be connected to venom glands
-#2 pedipalps = pincers, sensory organs, locomotion
-#3,4,5,6 = walking legs (4 pairs)
>eg sea spiders (pycnogonids), long legs, small body/head, in shallow waters (external fertilization)
Compare centipedes to millipedes
> centipedes (nocturnal)
-chilopoda
-1 pair of appendages per segment
-carnivores (fangs w poison)
-3,000 species
-eg house centipede (scutigera coleoptrata, invasive and indigenous in the mediterranean
> millipedes (diplopoda)
-2 pairs of appendages per segment
-detritivores, herbivores,
-11,000 species (more diverse)
-sex separated internalized fertilization
What are the four major groups of anthropods and their examples?
-Myriapods (millipedes, centipedes)
-Chelicerates (spiders, mites, and scorpions)
-Crustaceans (crabs, waterflees, barnacles, shrimp, crayfish, isopods)
-Insects (butterflies, moths, beetles, flies, grasshoppers)
What are myriapods
(‘countless feet’)
-found in moist forests
-2 body regions, simple long segmented bodies
-well defined head region
-two jaws: lower and upper
-one pair of antennae, simple eyes
What are crustaceans?
-insects are nested within crustacea (highly specialized crustaceans)
-crabs, crayfish, barnacles, shrimp, isopods
-47,000 species
-dominant marine, but also in freshwater and terrestrial environments
-make up a large part of zooplankton
-structure : segmented, head + thorax (cephalothorax) + abdomen
-appendages off each segment
-separate sexes (few hermaphroditic, few have asexual reproduction)
Are arthropods paraphyletic, monophyletic, or polyphyletic?
Mono
Are animals paraphyletic, monophyletic, or polyphyletic?
Mono
Are crustaceans paraphyletic, monophyletic, or polyphyletic?
Para
What are daphnias?
-water flea
-freshwater cladocera
-zooplankton
-important trophic link important grazer of phytoplankton and can be eaten by fish
-few mm in length
-phenotypic plasticity, can grow long spines, can change under enviro conditions
-model organisms for toxicology & ecological genomics due to its sensitivity to environmenal changes
-reproduced by cyclical parthenogenesis
What is the cyclical parthenogenetic life cycle and how does it work?
Copepods
-small crustaceans
-zooplankton
-important trophic link
What are insects
-dominantly terrestrial
-abundant on land and in the freshwater (few marine species)
-one million species described
-have 3 body regions: head with antennae, mouthparts (like mandibles), and compound eyes
-thorax with 3 pairs of walking legs may have wings (1 or 2 pairs)
-abdomen w no appendages
-sexual reproduction w separate sexes and metamorphosis (direct/indirect)
-have external elaborated mouthparts (unique to insects)
>used for biting
>herbivores, detritivores, fluid-drinkers, predators, scavengers, parasites
The diversity in mouthparts adapted for different feeding modes
a)grasshopper (chewing)
b)bee (lapping)
c)butterfly (siphoning)
d)mosquito (sucking)
Why are wings important in classifying insects?
Wings evolved around 320 mya - critical in identifying species
>very significant for classifying insects
>research suggests wings evolved from outgrowth of thorax or gill like projections from legs
Are the wings of an insect and the gill of crayfish homologous analogous?
homologous
-structures are homologous when they have a common ancestral root
-analogous structures have the same function and often similar appearance but different ancestry
Why are insects important for the ecosystem? What do they provide?
Insects provide ecosystem services
-pollination by native insects (crop pllination0
-decomposers: dung burial by dung beetles
-biological control of pests
-food source for other mammals, birds, fish
-dispersal agents (seeds, pathogens, other invertebrates)
How are insects affected today?
Insects are experiencing sharp decline in biodiversity and biomass (worldwide trend)
-bc of use of insecticide and habitat loss, degeneration, disappearance of plants or animals that insects depend on for food or shelter, displacement, pollution (light/air), insect diseases widespread
>linked to climate change
Protosomes vs Deuterosomes
Protostomes & deuterostomes (differ in cleavage, mesoderm, and origin of mouth and anu0
>polarity of digestive system
What are echinoderms?
Phylum Echinodermata
(‘spiny skin’)
-7000 extant species (sea stars, sea urchins, sea cucumbers, sea lilies)
-strictly marine, found on the seabed at every ocean depth
-diverse modes of nutrition
-appeared in the fossil record at the start of the cambrian
-sexual reproduction: separate sexes and external fertilization
-able to regenerate lost tissues (limbs)
Similarities between deuterostomes and echinoderms
-tripoblastic
-complete digestive tract
-eucoelomate body cavity
-bilateral symmetry during larval stage
-lost of a number of ancestral characters retained by other dueterostomes
-they lost: segmentation, cephalization, bilateral symmetry in the adult form
-derived characters special to the echinoderms:
>water vascular system (hydrolic/canals/chambers)
>dermal endoskeleton –< calcified plates, ossicles
>hemal system (lack true circulation system, parallels water vascular system to distribute nutrients)
>pentaradial symmetry (organs radiating from central disc in a pattern of 5)
How does the water vascular system in echinoderms work?
Water vascular system
-system of water-filled tubes
-end in ‘tube feet’ that extend through pores in endoskeleton
-used for locomotion, feeding, excretion, gas exchange
-sensory structures (chemical, tactile)
What is the skeletal structure of the echinoderm?
Hard endoskeleton
-composed of CaCO3 plates (ossicles) and spines
-continuous growth (plates enlarge and new ones are added)
-covered by thin layers of skin & muscles
Types of echinoderms
Phylum echinodermata
-crinoidea (sea lilies and sea fethers0
-asteroidea (sea stars)
-ophiuroidea (brittle stars)
-holothuroidea (sea cucumbers)
-echinoidea (sea urchins and sand dollars)
-crinoidea
