Unit 2 Animal Diversity
Phylum Mollusca
-very diverse group
-one of the largest animal phyla
-more than 90,000living species and 70,000 fossil species
-soft bodied
-range in size from microscopic to 900kg and 20 m long, 80% are under 10cm in size
-range from herbivores, grazers, predacious carnivores, filter feeders, detrius feeders, and parisites
-can be free floating, pelagic forms, or sessile, or burrow bottom feeder types
-most are marine, some are terrestrial, or live in freshwater, range in habitats from warm to polar seas
Phylum Mollusca Form and Function
-protostomes
-triploblastic body
-generalized mollusk body plan: head-foot, visceral mass (soft body), many with shell structure, most have well developed head, mouth, sensory organs, eyes can be simple to complex but most comlex in cephalapods
Radula (Phylum Mollusca)
-unique to mollusks
-protruding, rasping, tongue-like organ
-serves as a conveyor belt to move food towards digestive tract
-som ecan be specialized
-EX: moon snails bore through hard material, harpooning prey and can inject some of the worlds most lethal venom
Muscular Foot (Phylum Mollusca)
-used as attachment or for locomotion
-secreted mucus for adhesion or gliding
-numerous modifications include: attachment disc of limpets, hatchet foot of clams, siphons for jet propultion in cephalapods
Visceral Mass (Phylum Mollusca)
-mantle and mantle cavity
-mantle is a sheath tissue on each side of the body that protects soft parts
-mantle cavity houses gills or lungs
Shell (Phylum Mollusca)
-secreted by the mantle
-calcium for the shell comes from food and environment
Reproduction & Life History (Phylum Mollusca)
-no asexual reproduction
-develop via spiral cleavage
-most are dioecious (some hermaphroditic)
-many larval stage (aquatic)
-some direct development
Class Polyplacophora: Chitons
-flattened dorsoventrally
-dorsal surface has 7 or 8 articulating plates
-range from 2-30 cm
-head and cephalic organs are reduced
-at low tide, chitons press tightly against rocks to seal edges and prevent water loss
Class Gastropoda
-most diverse class, more than 70,000 living and more than 15,000 fossil species
-shells used as main defense
-some snails are specialized for climbing, swiming or burrowing
-range in forms: marine snails, limpets, slugs, whelks, etc.
Gastropd Shells (Class Gastropoda)
-one piece- univalve, coiled or uncoiled
-apex is smallest and oldest part of whorl
-many snails have an operculum covering shell opening (aperture)
-occupy all kinds of habitats that range from great altitudes to polar regions and the deep sea
Class Bivalvia
-also called pelecypoda or hatchet foot
-range in size from 1mm in length to the giant south pacific clams of 1m in length and 225 kg
-most are sedentary filter feeders
-lack a head, radula, or other aspects of cephalization
-most are marine, many live in brackish water, also in streams, ponds, and lakes
Reproduction and Development (Class Bivalvia)
-sexes usually seperate
-fertilization usually external with embryos developing as trochophore, veliger and spat larval stages
-freshwater clams hav einternal fertilizationwith sperm entering the incurrent siphon to fertilize eggs
Glochidium Larve
-specilized veligers that attatch to the gills of passing fish where they live breifly as parisites to complete their development
Class Cephalopoda
-all are marine predators like squids, octopi, and nautiluses
-foot is merged with the head region and modified for expelling water from the mantle cavity
-range from 2cm to 20m
-giant squid largest invertebrate
-nautilus is the remaining survivor of nautiloids which are the culmination of shell coiling
-octopi and squids evolved from early straight-shelled ancestors
-octopi are mostly intertidal and hide in rocks and crevices
-squids are deep sea animals
Locomotion (Class Cephalapoda)
-cephalapods swim by forcefully expelling water through a mobile ventral funnel or siphon
-squids and cuttlefish are streamlined with lateral fins as stabilizers
-nautilus swims mainly at night using gas chambers to. maintain position
-octopi have globular bodies and no fins so normally crawls over rocks and coral using tentacles and suction cups
Nervous and Sensory Structures (Class Cephalopoda)
-cephalopod brain is the largest of any invertebrate with several lobes and millions of nerve cells
-squids have the largest nerve fibers in the animal kingdom
-sense organs are well developed with complex eyes similar to vertebrates (fish)
-high visual activity but are generally color blind
Ink Sac (Class Cephalopoda)
-sepia (dark fluid with melanin) empties into rectum and used as protective device
Communication (Class Cephalopoda)
-most nearshore species use chemical and visual signals to communicate
Reproduction (Class Cephalopoda)
-sexes are seperate (dioecious)
-one arm of a male is modified, a hectocotylus, used to insert a spermatophore into the female
-juviniles hatch with no free-swimming larve
Dividing the Body (Annelids)
-annelids illustrate segmentation (metamerisim)
-bodies usually have serially repeated units (somites)
-units contain components of most organ systems
Evolution of Metamerisim (Annelids)
-allowed for.increased burrowing efficency (independent movement of segments)
-more sophisticated nervous system
-provided saftey factor, if one segment faied others could still function
Characteristics (Annelids)
-about 15,000 species
-about 2/3 are obscure marine worms
-annelids have worldwide distribution
-metamerisim (segmentation)
-walls called septa separate segments
-have tiny chitonous bristles called setae (except for leeches)
-setae used for swimming or crawling
-wormlike ceolomate protostomes
Class Polychaeta
-clam worms, neresis, fire worms:
-burrow near the low tide level
-nocturnal, carnivores
-undulating movements of the body provide burrowing and free swimming abilities
-hollow, brittle setae that contain poisonous secretions
-feed on cnidarians
Class Oligochaeta & Class Hirudinidea
-unique reproductive structure (clitellum) which is a ring of secretory cells found in a ring around the body
-permanent in oligochates but visible only during reproductive season in leeches
-hermaphrodites
-young develop inside cocoon secreted by clitellum and emerge as small worms
-usually do not self fertilize
Class Oligochaeta (Earthworms)
-over 3,000 species that have various sizes and live in a variety of habitats
-most are terrestrial, few are marine or brackish water, some parisitic
-detrivores (decaying plant material)
Class Hirudinidea (Leeches)
-most freshwater, few marine, most live in moist terrestrial environments
-more common in tropics
-range in size from 2-6 cm but can get to 30cm as found in he giant medicinal leeches
-some carnivores
-some temporary or permanent parisites
Origins of Metamerisim and the Coelom
-no satisfactory explanation for the origins of metamerisim and ceolom
-ceolomic fluid would have acted as circulatory fluid and reduce need for flame cells everwhere
-current evidence supports the hypothesis that segmentation arose independently multiple times
-however does not segmentation in athropods givien the rigidity of the exoskelton in terms of burrowing efficency
Phylum Nematoda (Roundworms)
-about 25,000 species are described
-due to new grouping, as many as half a million species may exist
-free living nematodes feed on bacteria, yeasts, fungus, hyphae and alge
-predatory nematodes eat rotifers, tardigrades, small annelids, and other nematodes
-food source for mites, insects, larve, and nematode eating fungi
-nematodes may be the most important pseudoceolomate animals in both abundance and impact on man
-found in virtually all habitats worldwide in soil, oceans, freshwater, plants and all kinds of animals
-most people only know some species as parisites in both man and domesticated animals
-occurs in up to 25% of people in some areas of the southeastern U.S. with more than 1 billion affected worldide
-female ascaris can lay up to 200,000 eggs a day that are passed out host's feces
Ecdysozoa
-ecdysis (shedding)
-many protozomes posess a cuticle which is a nonliving outer layer secreted by the epidermis
Cuticle
-stiff, hardened, outer body wall that restricts growth and must be molted with ecdysis
Hookworms
-small worms that have anterior ends with hook-like curves
-large plates in mouth cut into intestinal mucosa and suck host's blood
-blood is pumped through intestines, partially digesting and absorbing nutrients
Pinworms
-enterobius vermicularis is the mosrt common oinworm parisite in the U.S. but cause little disease
-adults live in the large intestine and cecum
-females about 12mm long migrate to anal region at night to lay eggs caysing itching
Phylum Tardigrada
-tardigrades/ water bears
-very small, less tlan 1mm long
most of the known 900 species are terrestrial but live in water film around mosses and lichens
-generally share many characteristcs with arthropods
-terrestrial tardigrades can suspend metabolisim to survive harsh conditions calle cryobiosis
-can dehydrate from 85% to 3% water with very little movement and body becomes barrel shaped
-resist extreme temps, oxygen deficency, and adverse situations for years
-when water is avalible they become metabolically active again
Exoskelton (Phylum Arthropoda)
-suit of armor
-precambrian era, developed hard exoskeleton made of chitin and protein
-protection against preators and enviromental hazards
-provide more secure site for muscle attachments
-greatly improved locomotion and flight
-chitonous outer shell
-may have waxy laayer (cuticle) to reduce water loss
-weight of exoskeleton limits final size
Phylum Arthropoda
-most diverse phylum of animals
-insects make up 60% of all species in phylum
-contains over 3/4 of all known species
-more than one million species of arthropods
-fossils date to late precambrian period
-abundant and wide ecological distribution
-active lifestyle
-varied modes of feeding, carnivory, herbivory, omnivory
-adapted to live on land, in sea, air, freshwater and in the bodies of many living things
Effects of Phylum Arthropoda
-Negative: some can be agents of disease and compete with humans for food
-Positive: plant polination, serve as food within ecosystem, produce various products with economic value (wax, dyes, silks, honey)
Joints (Phylum Arthropoda)
-joints have thin flexible sections to provide fliexibility between hard segments
-extensions of jointed segments become appendages
-sequence of molts necessary to allow for growth and recive hormonal control
-shed exoskeleton
Segmentation and Appendages (Phylum Arthropoda)
-many segments may be fused or combined into specalized groups called tagmata
-appendage function can vary: food handling, sensing, walking, swimming, flying
Tracheal System (Phylum Arthropoda)
-in terrestrial arthropods, air is piped directly to cells through a tracheal system
-allows high metabolic rates but limits body size
-aquatic arthropods respire with internal or external gills
Sensory Organs (Phylum Arthropoda)
-arthropods have highly developed sensory organs
-eyes vary from simple light sensing ocelli to a compound mosaic eye
-other sensory structures are well defined for touch, smell, hearing, balancing, and chemical reception
Behavioral Patterns (Phylum Arthropoda)
-arthropods have complex behavioral patterns
-social insects
-arthropods surpass most other invertebrates in complex and organized activities
Resources in Metamorphasis (Phylum Arthropoda)
-many arthropods undergo. metamorphic changes that have seperate larval and adult staages
-larve and adults feed on different organisims and occupy different habitats to avoid intraspecific competition
Subphylum Trilobita (Phylum Arthropoda)
-extinct arthropods
-trilobites arose before the cambrian, flourished, and became extinct 245 mya
-dorsoventally flattened bottom dwellers that were probably scavengers
-ranging from 2-67cm long
-could roll up like rollie pollies
-exclusively contained chitin, strengthened by calcium carbonate
Subphylum Chelicerata (Phylum Arthropoda)
-horshoe crabs
-chelicerites are known from the ordovician period more than 445 mya
-have 2 body regions, cephalothorax and abdomen
-generally 6 pairs of cephalothoracic appendages includong chelicerae, pedipalps, and 4 pairs of legs
-lack mandibles, have no antenne
-most species suck liquid food from prey
Class Arachnida (Subphylum Chelicerata)
-have great anitomical diversity
-more than 80,000 species
-most are predaceous and have fangs, poison glands, or stingers
-most arachnids are harmless to humans and provide essential of many insect pests
-humans benefit with fewer disease carrying ticks and mites in environment
-some spiders are venemous and cause pain or death in humans
-web spinning habits, spinning silk is a critical ability for spiders
-liquid scleroprotein secretions harden as it extruded from spinnerettes
-silk is used for orb webs, lining burrows, forming egg sacs, nest lining, nursery webs, and wrapping prey
Scorpions (Subphylum Chelicerata)
-postabdomen has long slender tail of 5 segments that ends in a stinging aparatus
-stinger on last segment has venom that varies from mildly painful to dangerously lethal with small ones being more toxic
Mites and Ticks (Subphylum Chelicerata)
-medically and economically the most important arachnid group
-hundreds of individuals of several species can be found in a few square meters of leaf mold in forests
-found worldwide
Subphylum Myriapoda
-myriapods mean "many footed" which describes the members of this group
-generally have 2 tagmata (head and trunk) with paired appendages along most segments
-class chilopoda (centipedes)
-class diplopoda (millipedes)
Phylogeny and Adaptive Diversification (Phylum Arthropoda)
-biologists assume that ancestral arthropods had a segmented body with one pair of legs per segment
-selection caused adjacent segments to fuse and make body regions
-much of arthropod diversity is due to modification and specialization of cuticular exoskeleton and appendages that allowed variation in feeding and movement (EX flight)
-small overall size also fostered higher diversity for arthropods and allowed them to thrive as compared to larger organisims
Subphylum Crustacea (Phylum Arthropoda)
-named for the hard exoskeleton
-over 67,000 species
-insects and crustaceans make up over 80% of our named animal species
General Nature of Crustaceans (Subphylum Crustacea)
-the main distinguishing characteristic - 2 pairs of antennae
-the head also has a pair of mandibles and 2 pairs of maxillae
-there is one pair of appendages on each additionl segment
-all appendages except first antanne are biramous (have 2 main branches)
-in most crustacea, one or more thoracic segments are fused within the head as a cephalothorax
-the secreted cuticle is made of chitin, protein, and calcareous material
Circulatory System (Subphylum Crustacea)
-crustaceans and other arthropods have an open circulatory system
-heart is the propulsive organ
-single chambered sac made of striated muscle
Muscular System (Subphylum Crustacea)
-striated muscles make up a major portion of the crustacean body
-most muscles are antagonistic groups
-flexors draw limb towards body
-extensors straighten a limb out
-strong muscles located on each side of the stomach control the mandibles
Respiratory System (Subphylum Crustacea)
-larger crustaceans have featherlike internal gills for gas exchange
-gills may project from the pleural wall into gill cavity
-articulation of thoracic legs moves water across the gills
Excretory System (Subphylum Crustacea)
-antenal or maxilary glands open at the base of those structures
-decapods have antennal glands called the green glands
-nitrogenous wastes, mostly ammonia, are excreted across thin areas in the gills
Nervous System (Subphylum Crustacea)
-nervous system of crustaceans has more fusion of ganglia compared to annelids-eyes and statocysts are the largest sensory organs
-chemical sensing of taste and smell occurs in hairs on antennae, within mouthparts, and other locations
-eyes are compound made of many units called ommatidia
-in bright light, each ommitidium sees a restricted visual area resulting in a mosaic image
-in dim light, distal and proximal digiments separate to produce a continous image
Adaptive Diversifiaction (Subphylum Crustacea)
-crustaceans are the domainant arthropids in any marine environments
-they also share dominance in freshwater environments with the insects
-class malacostracca is the most diverse
Hexapods
-primarially insects and closely related groups
-named for presnce of 6 legs
-all legs are uniramous
-3 tagmata (head, thorax, abdomen)
-appendages are attached to head and thorax
-there are 2 classes within hexapods
-entognata
-insecta (highest number of species)
Class Entognatha (Subphylum Hexapoda)
-small grouping which is bases of mouthparts are enclosed within the head capsule
-there are 3 orders of entognathans
-protura-diplura
-collembela
Class Insecta (Subphylum Hexapoda)
-enormous class
-have ectothanus mouthpieces
Class Entognatha Overview
-members of protura and diplura are tiny eyeless inhabitants of dark, damp places and soil
-members of collumbola are commonly called springtails because of their ability to leap
-a springtail 4mm long may leap up to 20 times its body length
-live in soil, occupying plant matter along freshwater ponds
-can be very abundant, millions per hectare
Class Insecta Diversity
-most abundant and diverse of all arthropods
-about 1.1 million species worldwide
-ecologically and economically important
Class Insecta Characteristics
-often 2 pairs of wings-vary in size from 1mm-20cm
-larger insects are found in tropical environments
Class Insecta Distribution
-insects are found in nearly all habitats except for sea
-insects are common in freshwater, brackish water and salt marshes
-insects are abundant in soil, forest canopies, and deserts
-many are endo or exo parisites of animals and plants
-flight and small size facilitate dispersal
-structural modifications, legs, wings, antenne, mouthparts, alimentary canal
-specalization for only eating one part of plant allows many insects to coexist on one plant
Class Insecta (head)
-usually one pair of large compound eyes
-one pair of antenne, vary greatly in form across the taxa
-they can feel, taste, and hear
Class Insecta (Thorax)
-reduced thorax
Class Insecta (Wings)
-cuticular, double membrane extensions formed by the epidermis
-veins serve to strengthen the wing
-vein pattern is used to identify insect taxa
Class Insecta (Abdomen)
-insect abdomen has 9-11 segments
Class Insecta (Body Form)
can be:
-thick and sheilded
-streamlined
-flat
Class Insecta (Power of Flight)
-insect wings are not homologous with bird and flying mammal wings
-evolved wings over 400 mya
-most flying insects have 2 pairs of wings
-order diptera (true flies) have 1 pair
Class Insecta (Modification of Wings)
-wings for flight are thin and membranous
-thick and horny front wings of beetles are protective
Class Insecta (Social Behavior)
-most social group
-highly organized
-depend on chemical and tactile communication
Honeybees
-have few male drones, a fertile queen, and many sterile female workers
-males come from unfertilized eggs, fertilized eggs produce females
-fertile queen develops because she alone is fed royal jelly (diet induced gene expression)
-honeybee scouts can inform workers of location of food
Ants
-have wingless soldiers and workers
-ants have evolved slavery, fungust farming, tool use and herding
Order Orthoptera
-grasshoppers and crickets
Order Hymenoptera
-wasps bees, and ants
Order Odonata
-dragonflies
Order Lepidoptera
-moths and butterflies
Order Diptera
-true flies