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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

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