Homework Questions--emailed to valenciabiologyhw@gmail.com 

1.        Compare developmental differences between protostomes and deuterostomes includng

a.        plane of cleavage

b.        determination

c.        fate of balstopore

d.        coelom formation

                        2. Describe the anatomy and generalized life cycle of a tapeworm

                        3. List characteristics of arthropods (Phylum Arthropoda) that distinguish them from other animal phyla

                        4. Distinguish among the following arthropod classes and give an example of each

0.      Arachnida

1.      Crustacea

2.      Diplopoda

3.      Chilopoda

4.      Insecta

                        5 Distingush between incomplete and complete metamorphosis

6 )  Which of the following factors, when used to label the horizontal axis of the previous graph, would account most directly for the shape of the plot?



Animal 2 Lecture Notes
• Overview: Life Without a Backbone
• Invertebrates
– Are animals that lack a backbone
– Account for 95% of known animal species
• A review of animal phylogeny
• Exploring invertebrate diversity
• Sponges are sessile and have a porous body and choanocytes
• Sponges, phylum Porifera
– Live in both fresh and marine waters
– Lack true tissues and organs
• Sponges are suspension feeders
– Capturing food particles suspended in the water that passes through their body
• Choanocytes, flagellated collar cells
– Generate a water current through the sponge and ingest suspended food
• Most sponges are hermaphrodites
– Meaning that each individual functions as both male and female
• Cnidarians have radial symmetry, a gastrovascular cavity, and cnidocytes
• All animals except sponges
– Belong to the clade Eumetazoa, the animals with true tissues
• Phylum Cnidaria
– Is one of the oldest groups in this clade
• There are two variations on this body plan
– The sessile polyp and the floating medusa
• Cnidarians are carnivores
– That use tentacles to capture prey
• The tentacles are armed with cnidocytes
– Unique cells that function in defense and the capture of prey
• The phylum Cnidaria is divided into four major classes
– Hydrozoa, Scyphozoa, Cubozoa, and Anthozoa
• Most hydrozoans
– Alternate between polyp and medusa forms
• In the class Scyphozoa
– Jellies (medusae) are the prevalent form of the life cycle
• In the class Cubozoa, which includes box jellies and sea wasps
– The medusa is box-shaped and has complex eyes
• Class Anthozoa includes the corals and sea anemones
– Which occur only as polyps
• : Most animals have bilateral symmetry
• The vast majority of animal species belong to the clade Bilateria
– Which consists of animals with bilateral symmetry and triploblastic development
• Members of phylum Platyhelminthes
– Live in marine, freshwater, and damp terrestrial habitats
– Are flattened dorsoventrally and have a gastrovascular cavity
• Although flatworms undergo triploblastic development
– They are acoelomates
• Flatworms are divided into four classes
• Turbellarians
– Are nearly all free-living and mostly marine
• The best-known turbellarians, commonly called planarians
– Have light-sensitive eyespots and centralized nerve nets
Monogeneans and Trematode
• Monogeneans and trematodes
– Live as parasites in or on other animals
– Parasitize a wide range of hosts
• Trematodes that parasitize humans
– Spend part of their lives in snail hosts
• Most monogeneans
– Are parasites of fish
• Tapeworms
– Are also parasitic and lack a digestive system
• Rotifers, phylum Rotifera
– Are tiny animals that inhabit fresh water, the ocean, and damp soil
• Rotifers are smaller than many protists
– But are truly multicellular and have specialized organ systems
• Rotifers have an alimentary canal
– A digestive tube with a separate mouth and anus that lies within a fluid-filled pseudocoelom
• Rotifers reproduce by parthenogenesis
– In which females produce more females from unfertilized eggs
Lophophorates: Ectoprocts, Phoronids, and Brachiopods
• Lophophorates have a lophophore
– A horseshoe-shaped, suspension-feeding organ bearing ciliated tentacles
• Ectoprocts
– Are colonial animals that superficially resemble plants
• Phoronids
– Are tube-dwelling marine worms ranging from 1 mm to 50 cm in length
• Brachiopods superficially resemble clams and other hinge-shelled molluscs
– But the two halves of the shell are dorsal and ventral rather than lateral, as in clams
• Members of phylum Nemertea
– Are commonly called proboscis worms or ribbon worms
• The nemerteans unique proboscis
– Is used for defense and prey capture
– Is extended by a fluid-filled sac
• Nemerteans also have a closed circulatory system
– In which the blood is contained in vessels distinct from fluid in the body cavity
• Molluscs have a muscular foot, a visceral mass, and a mantle
• Phylum Mollusca
– Includes snails and slugs, oysters and clams, and octopuses and squids
• Most molluscs are marine
– Though some inhabit fresh water and some are terrestrial
• Molluscs are soft-bodied animals
– But most are protected by a hard shell
• All molluscs have a similar body plan with three main parts
– A muscular foot
– A visceral mass
– A mantle
• Most molluscs have separate sexes
– With gonads located in the visceral mass
• The life cycle of many molluscs
– Includes a ciliated larval stage called a trochophore
• There are four major classes of molluscs
• Class Polyplacophora is composed of the chitons
– Oval-shaped marine animals encased in an armor of eight dorsal plates
• About three-quarters of all living species of molluscs
– Belong to class Gastropoda
• Most gastropods
– Are marine, but there are also many freshwater and terrestrial species
– Possess a single, spiraled shell
• Slugs lack a shell
– Or have a reduced shell
• The most distinctive characteristic of this class
– Is a developmental process known as torsion, which causes the animal’s anus and mantle to end up above its head
• Molluscs of class Bivalvia
– Include many species of clams, oysters, mussels, and scallops
– Have a shell divided into two halves
• The mantle cavity of a bivalve
– Contains gills that are used for feeding as well as gas exchange
• Class Cephalopoda includes squids and octopuses
– Carnivores with beak-like jaws surrounded by tentacles of their modified foot
• Most octopuses
– Creep along the sea floor in search of prey
• Squids use their siphon
– To fire a jet of water, which allows them to swim very quickly
• One small group of shelled cephalopods
– The nautiluses, survives today
• Anatomy of an earthworm
• Annelids are segmented worms
• Annelids
– Have bodies composed of a series of fused rings
• The phylum Annelida is divided into three classes
• Oligochaetes (class Oligochaeta)
– Are named for their relatively sparse chaetae, or bristles made of chitin
– Include the earthworms and a variety of aquatic species
• Earthworms eat their way through the soil, extracting nutrients as the soil moves through the alimentary canal
– Which helps till the earth, making earthworms valuable to farmers
• Members of class Polychaeta
– Possess paddlelike parapodia that function as gills and aid in locomotion
• Members of class Hirudinea
– Are blood-sucking parasites, such as leeches
• Nematodes are nonsegmented pseudocoelomates covered by a tough cuticle
• Among the most widespread of all animals, nematodes, or roundworms
– Are found in most aquatic habitats, in the soil, in moist tissues of plants, and in the body fluids and tissues of animals
• The cylindrical bodies of nematodes (phylum Nematoda)
– Are covered by a tough coat called a cuticle
• Some species of nematodes
– Are important parasites of plants and animals
• Early arthropods, such as trilobites
– Showed little variation from segment to segment
• : Arthropods are segmented coelomates that have an exoskeleton and jointed appendages
• Two out of every three known species of animals are arthropods
• Members of the phylum Arthropoda
– Are found in nearly all habitats of the biosphere
General Characteristics of Arthropods
• The diversity and success of arthropods
– Are largely related to their segmentation, hard exoskeleton, and jointed appendages
• As arthropods evolved
– The segments fused, and the appendages became more specialized
• The appendages of some living arthropods
– Are modified for many different functions
• The body of an arthropod
– Is completely covered by the cuticle, an exoskeleton made of chitin
• When an arthropod grows
– It molts its exoskeleton in a process called ecdysis
• Arthropods have an open circulatory system
– In which fluid called hemolymph is circulated into the spaces surrounding the tissues and organs
• A variety of organs specialized for gas exchange
– Have evolved in arthropods
• : Arthropods are segmented coelomates that have an exoskeleton and jointed appendages
• Two out of every three known species of animals are arthropods
• Members of the phylum Arthropoda
– Are found in nearly all habitats of the biosphere
• Molecular evidence now suggests
– That living arthropods consist of four major lineages that diverged early in the evolution of the phylum
• Cheliceriforms, subphylum Cheliceriformes
– Are named for clawlike feeding appendages called chelicerae
– Include spiders, ticks, mites, scorpions, and horseshoe crabs
• Most of the marine cheliceriforms are extinct
– But some species survive today, including the horseshoe crabs
• Most modern cheliceriforms are arachnids
– A group that includes spiders, scorpions, ticks, and mites
• Arachnids have an abdomen and a cephalothorax
– Which has six pairs of appendages, the most anterior of which are the chelicerae
• Subphylum Myriapoda
– Includes millipedes and centipedes
• Millipedes, class Diplopoda
– Have a large number of legs
• Each trunk segment
– Has two pairs of legs
• Centipedes, class Chilopoda
– Are carnivores with jaw-like mandibles
– Have one pair of legs per trunk segment
• Subphylum Hexapoda, insects and their relatives
– Are more species-rich than all other forms of life combined
– Live in almost every terrestrial habitat and in fresh water
• The internal anatomy of an insect
– Includes several complex organ systems
• Flight is obviously one key to the great success of insects
• An animal that can fly
– Can escape predators, find food, and disperse to new habitats much faster than organisms that can only crawl
• Many insects
– Undergo metamorphosis during their development
• In incomplete metamorphosis, the young, called nymphs
– Resemble adults but are smaller and go through a series of molts until they reach full size
• Insects with complete metamorphosis
– Have larval stages specialized for eating and growing that are known by such names as maggot, grub, or caterpillar
• The larval stage
– Looks entirely different from the adult stage
• Metamorphosis from the larval stage to the adult stage
– Occurs during a pupal stage
• Insects are classified into about 26 orders
• Insects are classified into about 26 orders
• Insects are classified into about 26 orders
• Insects are classified into about 26 orders
• The Apterygota
• Protura
• Collembola Springtails
• Thysanura Silverfish
• Diplura Two Pronged Bristle-tails
• The Exopterygota
• Ephemeroptera Mayflies
• Odonata Dragonflies
• Plecoptera Stoneflies
• Grylloblatodea
• Orthoptera
• Phasmida Stick-Insects
• Dermaptera Earwigs
• Hemiptera True Bugs
• Thysanoptera
• The Endopterygota
• Neuropter Lacewings
• Coleoptera Beetles
• Strepsiptera Stylops
• Mecoptera Scorpionflies
• Siphonaptera Fleas
• Diptera True Flies
• Lepidoptera Butterflies and Moths
• Trichoptera Caddis Flies
• Hymenoptera Ants Bees and Wasps
• While arachnids and insects thrive on land
– Crustaceans, for the most part, have remained in marine and freshwater environments
• Crustaceans, subphylum Crustacea
– Typically have biramous, branched, appendages that are extensively specialized for feeding and locomotion
• Decapods are all relatively large crustaceans
– And include lobsters, crabs, crayfish, and shrimp
• Planktonic crustaceans include many species of copepods
– Which are among the most numerous of all animals
• Barnacles are a group of mostly sessile crustaceans
– Whose cuticle is hardened into a shell
• Echinoderms and chordates are deuterostomes
• At first glance, sea stars and other echinoderms, phylum Echinodermata
– May seem to have little in common with phylum Chordata, which includes the vertebrates
• Chordates and echinoderms share characteristics of deuterostomes
– Radial cleavage
– Development of the coelom from the archenteron
– Formation of the mouth at the end of the embryo opposite the blastopore
• Sea stars and most other echinoderms
– Are slow-moving or sessile marine animals
• A thin, bumpy or spiny skin
– Covers an endoskeleton of hard calcareous plates
• Unique to echinoderms is a water vascular system
– A network of hydraulic canals branching into tube feet that function in locomotion, feeding, and gas exchange
• The radial anatomy of many echinoderms
– Evolved secondarily from the bilateral symmetry of ancestors
• Living echinoderms are divided into six classes
Sea Stars
• Sea stars, class Asteroidea
– Have multiple arms radiating from a central disk
• The undersurfaces of the arms
– Bear tube feet, each of which can act like a suction disk
Brittle Stars
• Brittle stars have a distinct central disk
– And long, flexible arms
Sea Urchins and Sand Dollars
• Sea urchins and sand dollars have no arms
– But they do have five rows of tube feet that function in movement
Sea Lilies and Feather Stars
• Sea lilies
– Live attached to the substrate by a stalk
• Feather stars
– Crawl about using their long, flexible arms
Sea Cucumbers
• Sea cucumbers
– Upon first inspection do not look much like other echinoderms
– Lack spines, and their endoskeleton is much reduced
Sea Daisies
• Sea daisies were discovered in 1986
– And only two species are known
• Chordates
– Phylum Chordata
– Consists of two subphyla of invertebrates as well as the hagfishes and the vertebrates
– Shares many features of embryonic development with echinoderms
• A summary of animal phyla
• A summary of animal phyla
• A summary of animal phyla
• A summary of animal phyla