Zoology Exam 3

Zoology

Phylum Arthropoda Part 3

Subphylum Hexapoda

§     Six legs

§     All legs are uniramous

§     Three tagmata (regions): Head, thorax, and abdomen

§     Along with Crustacea, the hexapods are grouped in the clade Pancrustacea

§     Two classes:

l     Entognatha (“ento”: inside,  “gnatha”: jaw)

l     Insecta

Class Entognatha

§     Bases of the mouthparts enclosed within the head capsule

§     Small group

§     Example: Order Collembola – Springtails

l     Live in the soil or in freshwater

l     Are able to spring from place to place (name = springtails)

l     Some species emerge from the snow and people call them “snow fleas”

Class Insecta

§     The most diverse and abundant of all groups of arthropods

l     There are more species of insects than species of all other animals combined

l     1.1 million insects have been classified, but some project that as many as 30 million species exist

§     Entomology: study of insects

§     Insects are ectognathous which means the bases of the mouthparts are outside of the head capsule

§     Usually have two pairs of wings and they are attached to the thorax

l     Some insects have one pair of wings and some have no wings

§     Distribution:

l     Occur in almost every terrestrial and freshwater habitat

•       Only a few occur in marine habitats

§     The exoskeleton is formed of a system of plates called sclerites

l     The sclerites are connected by concealed, flexible hinge joints

§     Muscles between sclerites enable insects to make precise movements

§     The exoskeleton contains mostly chitin which provides rigidity, but is also light enough to allow for flight (not much calcium carbonate because it would be too heavy)

l     Chitin is also waterproof

§     Head usually bears:

l     Two compound eyes

l     A pair of antennae – vary greatly in form and function

•       Can act as: tactile (touch) organs, olfactory (smell) organs and/or auditory (hearing) organs

l     Mouthparts – Made of exoskeleton (cuticle) and vary greatly

•       The type of mouthpart that an insect possesses determines how it feeds

–      Chewing mouthparts – Example: Grasshopper

–      Sucking mouthparts – Example: Mosquito

–      Siphoning mouthparts – Example: Butterfly

–      Sponging mouthparts – Example: House fly

§     Alimentary canal – digestive system

l     Foregut- esophagus and crop (lined with cuticle)

l     Midgut – stomach & gastric ceca

l     Hindgut – Intestine & rectum (lined with cuticle)

§     Malpighian tubules – Excretory system

l     Tubules that attach between the midgut and the hindgut

l     Take nitrogenous wastes out of the hemolymph and placed in the posterior part of the alimentary canal

l     Also control water balance

§     Circulatory system:

l     A tubular heart, located posteriorly in the insect, creates peristaltic waves that moves the hemolymph (blood) forward through the only blood vessel, the dorsal aorta

l     The brain receives the freshest hemolymph

l     The hemolymph then passes major muscle masses (legs, wings, etc.)

l     It moves posteriorly pass the alimentary canal where it receives nutrients

l     Further past the Malpighian tubules which cleanses the hemolymph of metabolic waste

l     And then back into the heart through the ostia

§     The hemolymph contains plasma and amebocytes, but usually carries no oxygen (so it usually contains no hemoglobin)

§     Gas exchange in terrestrial insects

l     Tracheal system:  A network of thin walled tubes that branch to every part of the body

l     The system opens to the outside through spiracles

l     The tracheae are lined with cuticle and must be shed during molting along with the insects exoskeleton

l     Tracheoles are smaller tubes and are not lined with cuticle

•       Tracheoles are not shed with molting

•       O₂ diffuses from the tracheoles to the cells and CO₂ diffuses from the cells to the tracheoles

§     Gas exchange in aquatic insects

l     Most aquatic insects have closed tracheal system

l     There are no spiracles, the gases cross the thin exoskeleton and move into the tracheae

•       Gases move through the body wall and / or gills

•       Gills in aquatic insects are just areas with high surface to volume ratios

l     The rest of the tracheal system remains the same as for terrestrial insects

§     Metamorphosis:  Change in form during postembryonic development

l     A/metabolous (direct) development:  Young are similar to adults except in size and sexual maturity

•       Example: Silverfish

l     Hemimetabolous (Incomplete) metamorphosis: Gradual changes in form during growth from an immature to adulthood

•       Nymphs to adult

•       Wings develop externally in pads and then a winged adult develops

•       Examples: grasshoppers and mayflies

l     Holometabolous (Complete) metamorphosis: Drastic changes in form during growth from an immature to adult

•       Larva to Pupa to Adult

•       Wings develop internally during pupa stage

•       88% of all insects

•       Examples: Butterfly and Beetles

l     Classification of insects:

l     Subclass A/pterygota

•       Order Thysanura – Silverfish

–      Long antennae and three terminal cerci

l     Subclass Pterygota

•       Infraclass Paleoptera

–      Order Ephemeroptera – Mayflies

»      Membranous forewings longer than hindwings

–      Order Odonata – Dragonflies and damselflies

»      Long, narrow, membranous wings on a long slender body

•       Infraclass Neoptera

–      Order Orthoptera – Grasshoppers, etc

»      Hindwings folded like a fan under thickened forewings

-       Order Hemiptera: Leaf bugs, stink bugs, etc.

»      Piercing sucking mouthparts

»      Forewing - Front half thick, back half membranous

–      Order Coleoptera – Beetles

»      Front wings hard and thick

»      Hindwings membranous

–      Order Lepidoptera – Butterflies and moths

»      Membranous wings covered with overlapping scales

»      Mouthparts form a sucking tube

–      Order Diptera – True flies

»      Single pair of wings

»      Halteres for balancing

–      Order Hymenoptera - Ants, bees, wasps

»      Wings coupled distally

»      Hindwings smaller

Zoology

Insect Metamorphosis

(A challenge to Evolution)

Molting is not so simple

•       Molting for growth or for metamorphosis is an intricate process

•       The initiation of molting and the timing of the various processes must be exact otherwise the insect will not survive

•       A number of hormones control the molting process

–      Brain hormone (Prothoracicotropic hormone) initiates molting

–      Ecdysone activates the epidermal cells to produce a new exoskeleton and molting fluid

–      Juvenile hormones interact with ecdysone to determine which stage of metamorphosis the insect should be in

–      Bursicon triggers the sclerotization of the exoskeleton

·       Molting not only requires the shedding of the old cuticle and the making of the new cuticle that surrounds the insect, but also:

–      The cuticle in the tracheal system

–      The cuticle that lines the foregut and hindgut

Metamorphosis is Complex

•       Before a caterpillar becomes a butterfly pupa (chrysalis) tiny packets of cells called imaginal discs begin forming in different places

–      imaginal discs: undifferentiated cells that are set aside during embryonic development and carried through the larval stages

•       Some differentiate to form pupal characteristics

•       Some wait and then differentiate to form adult features

•       Certain imaginal discs become attached underneath the caterpillar’s exoskeleton and then form the pupal exoskeleton

•       Once the pupal exoskeleton is completed most of the insides of the caterpillar are broken down except for a few nerves and muscles

•       The imaginal discs then begin generating an adult butterfly

–      Leaf chewing mouthparts must be replaced by nectar siphoning mouthparts

–      Simple eyes are replaced by compound eyes

–      They must produce four wings covered with scales where no wings occurred before

–      A new respiratory system that can sustain flight is created

–      The digestive system changes from digesting plant food to digesting nectar

–      A new thorax and abdomen are formed

•       New nerves and muscles are created

•       Some nerves and muscles are reused, but must be rearranged

–      Some imaginal disks cling to the inside of the pupal exoskeleton to produce an adult exoskeleton

•       Since the pupa doesn’t feed, all of these new features must come from the materials accumulated during the larval stage

•       Finally n adult butterfly emerges from the pupa

•       In many ways, the creation of a holometabolous insect is the creation of three “different” organisms

Zoology

Phylum Chaetognatha & Phylum Echinodermata

Phylum Chaetognatha – Arrow worms

•       Marine animals that are highly specialized for planktonic environments

•       A small group of animals that fall between the protostome and deuterostome clades

•       Mouth does not arise from the first opening, but development is different from the deuterostomes

•       They are coelomates and the coelom is used as a hydrostatic skeleton

•       Small (1 to 12 cm), straight bodies resemble torpedoes

•       Planktonic predators that spend much of the time floating, but can dart quickly after prey

•       Complete digestive system and a nervous system

•       But no respiratory or excretory system

•       Beneath the head is a large depression called a vestibule that leads to the mouth

•       The vestibule contains teeth

•       On both sides of the vestibule are sickle-shaped, chitinous spines for grasping prey

•       The only invertebrates with a multi-layered epidermis

•       Fossils of chaetognatha have been found in the Cambrian rock layers

•       The fossil forms are very similar to modern forms

Phylum Echinodermata
(Prickly – skin)

•       Marine coelomates

•       Deuterostomes: Develop mouth from the second opening

•       Spiny endoskeleton of plates

•       No ability to osmoregulate

•       Most have radial symmetry (there are some exceptions with bilateral symmetry)

•       Basic pentaradial symmetry in most adults

•       Pentaradial symmetry: Any one-fifth "pie slice" of an echinoderm should have all of the same structures as any other

•       Water vascular system

•       Unique to echinoderms

•       A set of canals and specialized tube feet that work with the dermal ossicles to form a hydraulic system

Class Asteroidea - Sea stars

•       A central disc that merges with the tapering arms (rays)

•       Body covered with a ciliated, pigmented epidermis

•       A ventral ambulacral groove runs from the mouth to the tip of the arm

•       The groove is bordered by rows of tube feet which usually have suckers

•        The groove and tube feet are not covered with ossicles (open)

•       The aboral (dorsal) side

•       Covered with spines (often flattened)

•       Around the bases of the spines are minute, pincerlike pedicellariae

•       Keep the body free of debris

•       Papulae (dermal gills): Soft projections covered with only epidermis are involved with respiration

•       Madreporite: A circular sieve leading to the water vascular system

•       Endoskeleton

•       Ossicles, calcareous plates, bounded together by catch collagen

•       Catch collagen:  Collagen that is under neurological control

•       Changes collagen from “liquid” to “solid” very quickly allowing the sea star to hold various postures without muscular effort

•       Spines project from the ossicles

•       Spacious body coelom filled with fluid which bathes internal organs and moves into the papulae

•       Exchange of respiratory gases and excretion of ammonia occurs by diffusion through the thin walls of the papulae and tube feet

•       Water-vascular system

•       A ring canal surrounds the mouth

•       Radial canals diverge from the ring canal and run up the ambulacral groove of each ray

•       A series of lateral canals connects the radial canals to the tube feet

•       Many sea stars feed on molluscs especially bivalves

•       They use their tube feet in relays to pull apart the valves

•       When the bivalve’s adductor muscles fatigue a small gap opens

•       The sea star inserts its stomach in between the valves and around the bivalves soft parts and begins digestion

•       Most sea stars are dioecious

•       Fertilization is external

•       In addition to regeneration, sea stars exhibit autotomy and can cast off an injured arm near its base and then regenerate it

•       Autotomy: Detachment of a part of the body by an organism

•       Most sea stars produce free-swimming, planktonic larvae

•       The free-swimming larvae have cilia arranged in bands and are called bipinnaria

•       When the bipinnaria develop three arms and a sucker it is called a brachiolaria

Class Ophiurodea – Brittle stars

•       Largest class of echinoderms in both number of species and individuals

•        Most active at night

•       Differ from sea stars:

•       Arms are slender and sharply set apart from the central disc

•       Tube feet without suckers

•       No pedicellariae or papulae

•       Ambulacral grooves are closed and covered with arm ossicles

•       Madreporite is located on the oral surface

•       Most brittle stars are dioecious although a few are monoecious

•       Regeneration and autotomy occur often

Class Echinoidea – Sea urchins and sand dollars

•       Have a compact body enclosed in a test or shell

•       Dermal ossicles are closely fitted plates that form the test

•       The plates bear small tubercles on which the round ends of spines articulate as ball-and-socket joints

•       Spines are moved by small muscles

•       No arms but tube feet with suckers are arranged in five ambulacral grooves

•       Ambulacral grooves are closed

•       Like sea stars, they have pedicellariae to keep their bodies clean

•       Aristotle’s lantern is a complex chewing mechanism with 5 pairs of retractor muscles and 5 pairs of protractor muscles

•       Dioecious

•       Regular Echinoidea

•       Most species

•       Radial symmetry

•       Medium to long spines

•       Rocky and hard substrates

•       Irregular Echinoidea

•       Sand dollars and heart urchins

•       Bilateral symmetry

•       Short spines

•       Burrow into sandy substrates

Class Holothuroidea – Sea cucumbers

•       Elongate, cucumber-shaped bodies

•       No arms or spines

•       Ossicles greatly reduced and so they are more soft bodied

•       Tube feet with suckers

•       Ambulacral grooves are closed

•       Oral tentacles are used for feeding

•       Pedicellariae absent

•       Most are dioecious although some are monoecious

•       Defense mechanism

•       Can cast out its viscera through the ruptured body wall or evert its contents out the anus

Class Crinoidea – Sea lilies and feather stars

•       The fossil record reveals crinoids were once far more prevalent than they are now

•       Crinoids remain attached to a substrate during much of their lives

•       Body disc (calyx) is covered with leathery skin containing calcareous plates

•       Five flexible arms branch to form many more arms

•       The calyx and the arms form the crown

•       Ambulacral grooves are open and ciliated to carry food to the mouth

•       Tube feet without suckers line the grooves

•       No pedicellariae

•       No madreporite

•       Therefore, no exchange of fluid with the environment

•       Water-vascular system must function entirely on existing coelomic fluid

•       Sea lilies have a flower-shaped body at the tip of an attached stalk

•       Feather stars have long, many branched arms

•       Larvae are sessile

•       Adults are free-moving, but tend to stay in the same place for long periods of time

Zoology

Ecology

§     Environment: All external factors, living and nonliving, that affect a living organism

§     Ecology: The study of the interactions of living organisms with each other and the nonliving (physical) environment

§     Environmental Science

l     The study of the interaction of humans with the earth

l     Uses the physical, biological (especially ecology) and social sciences to assess and develop solutions to environmental problems

§     An organism’s habitat is where it lives in the community (bog, forest floor, swift river, or ocean’s edge)

§     An ecological niche is the role an organism plays in the community:

•       Habitat

•       Interaction with other species

§     Terrestrial and aquatic habitats for animals are described differently

l     When describing habitat terrestrial ecologists often focus on plants because they dominate a community and strongly influence the physical environment

l     Aquatic ecologists, however, emphasize physical and chemical factors instead of biological factors when describing habitat because organisms less conspicuously affect aquatic habitats

•       Four physical factors that are often measured when describing aquatic habitats are light penetration, dissolved oxygen, temperature, and pH

Major Ecological Themes

§     Population: all the organisms within an area belonging to the same species.

•       Interested in:

–      Growth:

»      Endangered species, fish and game animals

–      regulation

»      Predators, disease, hunting

§     A community consists of all the various populations at a locale and the structure that results

l     The analysis and classification of communities is important in the preparation of maps that form the basis of natural resource management

§     Ecological Succession: a change in community composition over time

l     An area goes through many predetermined communities before reaching the climax community

•       Example: see picture

l     Pioneer species: first species to colonize area

l     Climax community:  the final community to occupy an area.  Often determined by climate

•       Coniferous forest (northern zone)

•       Deciduous forest (temperate zone) (winters and summers are different)

•       Tropical rain forest (tropics)

l     Primary succession - Bare earth or rock is colonized by organisms

•       Volcanic, glacier retreat, sand dune

l     Secondary succession - Previously vegetated areas that are disturbed

•       A soil already occurs here

•       Examples:

–      abandoned farmland

–      areas burned by fire

§     An ecosystem is the community of populations and the abiotic (nonliving) environment.

l     Two important principles:

•       Energy flows

•       Chemical cycling

§     Ecosystem composition

l     Producers (autotrophs) - produce food for themselves and others

•       Most use photosynthesis

l     Consumers (heterotrophs) - Eat producers

•       Herbivores (primary consumers) -

–       Eat plants

–       i.e. Deer

•       Carnivores (secondary consumers)

–      eat consumers

–       i.e. mountain lions

•       Omnivores

–      eat plants and herbivores

–       i.e. Opossums, Humans

•       Decomposers

–      Break down and absorb dead material

–      i.e. fungi

–      Although decomposers have been ignored for a long time by ecologists it is becoming apparent that they play an extremely important role in chemical cycling

Relationships within ecosystems

§     Food chains (linear) - Simplistic picture of who eats whom.

§     Food web

l     More complicated but more realistic

l     Allows for multiple relationships

§     These feeding relationships form pyramids of energy

l     Energy pyramid- Energy does NOT cycle, it flows. Light energy captured by the sun is eventually lost to work or heat.

•       Only about 10% of the energy is passed from one trophic level to the next

§     Biogeochemical cycles: Chemicals circulate through ecosystems and involve components that are:

l     Living (biosphere)

l     Nonliving (geological)

l     Biogeochemical cycles help us to understand where important nutrients and pollutants travel

§     Biogeochemical cycles have the following parts

l     A reservoir: chemicals unavailable to producers i.e. rocks

l     An exchange pool: organisms can obtain these chemicals

•       Atmosphere (gaseous cycle)

•       Soil (Sedimentry cycle)

l     Biotic community - chemicals move along the food chains

l     Carbon cycle

•       Includes greenhouse gasses such as carbon dioxide and methane

§     The biosphere is the thin layer of water, land, and air inhabited by living organisms

§     Biomes - The largest units of the biosphere and these are primarily defined by climate:

l     Temperature

l     rainfall

§     Influenced also by topographical features

l     \rain shadows

§     Biomes change with latitude and altitude

§     Biome Example: Grasslands

•        Savanna (e.g. Africa) - Cool dry season, hot rainy season

•       Temperate grasslands - prairies of North America

–      Most have been converted to farming because of very fertile soils

–      Plants

»      tall grass prairie - wetter

»      short grass prairie – drier

Climate diagrams

§     The distribution of terrestrial ecosystems is closely related to regional climate

§     Climate diagrams describe:

l     Temperature (Mean annual & Mean monthly)

l     Precipitation (Mean annual & Mean Monthly)

l     Topography (Elevation above sea level)

§     It is especially important to contrast the seasonality of temperature and precipitation

l     Example: Various grasslands

§     Biogeography: is the study of the distributions of organisms   

l     Its goal is to describe and understand the many patterns found in the distribution of species

(biodiversity hotspots)

§     The eight biogeographical realms of the world:

l     Eastern Hemisphere:

•        Palearctic (Russia and Europe)

•       Afrotropic (Ethiopian)

•       Indo-Malay (Oriental)

l     Western Hemisphere

•       Nearctic (North America and Canada)

•       Neotropic (South America)

l     Australasia

l     Oceana (islands of the Pacific Ocean)

l     Antarctic

The proper relationship between a Christian and creation

§     Francis A. Schaeffer - Pollution and the Death of Man: The Christian View of Ecology 1970 –Tyndale House Publishers

§     Two important points:

l     Since humans, animals and plants are all created by God

•       We are all equally separated from God in that He is the Creator

•       Man, therefore is united to all other creatures as being created

l     Man’s relationship with God, however, is different from the rest of creation in that people have been made in the image of God

Stewardship of Creation

§     God is the creator and is the sustainer of Creation (Gen. 1, Psalm 104, etc.)

§     We are to use the creation

l     Everything that lives and moves will be food for you.  Just as I gave you the green plants, I now give you everything. Genesis 9:3

§     Stewardship - responsibility

l     The Lord God took the man and put him in the Garden of Eden to work it and take care of it. Genesis 2:15

§     God maintains ownership of His Creation (Deut. 10:14, Psalm 24:1, Psalm 95:4-5)

l     The earth is the Lord’s, and everything in it, the world, and all who live in it. Psalm 24:1

§     God cares about his creation (Not just in Genesis but other Books talk about His creation)

l     God saw all that he had made, and it was very good. … Genesis 1:31

l     Look at the birds of the air; they do not sow or reap or store away in barns, and yet your heavenly Father feeds them … Matt 6:26

l     Are not five sparrows sold for two pennies?  Yet not one of them is forgotten by God   Luke 12: 6

§     God is still in control of his creation

l     Are not two sparrows sold for a penny.  Yet not one of them will fall to the ground apart from the will of your Father. Matt 10: 29

§     Human life is sacred

l     So God created man in His own image …” Genesis 1:27

§     Accountability

l     And if you have not been trustworthy with someone else’s property, who will give you property of your own? Luke 16:12

Zoology

Phylum Chordata

l     Coelomates

l     Deuterostomes

l     Five chordate characteristics

–      Notochord

–      Dorsal tubular nerve cord

–      Pharyngeal pouches and slits

–      Endostyle or thyroid gland

–      Postanal tail

l     Notochord

–      Flexible, rodlike structure

–      First part of the endoskeleton to appear in an embryo

–      Contains fluid-engorged cells

–      Muscles attached to the notochord provide undulatory movements of the body

–      In most vertebrates, the notochord is replaced by vertebrae

l     Dorsal tubular nerve cord

–      Dorsal to the digestive tract

·       Most invertebrate phyla have a ventral nerve cord

–      Begins as a tube

·       Most invertebrate nerve cords start out solid

–      The anterior end is enlarged to form a brain among vertebrates

l     Pharyngeal slits and pouches

–      Slits are openings that lead from the pharyngeal cavity to the outside

·       Aquatic chordates

·       Work as filter feeding mechanisms or as gills

–      Pouches

·       Do not open to the outside

·       In terrestrial (tetrapod) vertebrates the pouches give rise to:

–      Eustacean tube

–      Middle ear

–      tonsils

–      Parathyroid glands

l     Endostyle or thyroid gland

–      Endostyle

·       Found in protochordates and lamprey larvae

·       Some cells secrete iodinated ….

–      Thyroid gland

·       Adult lampreys and all other vertebrates

·       Secretes iodinated hormones

l     Postanal tail

–      A structure added behind the digestive system

–      Many vertebrates have postanal tails, but not all

·       I would not call the coccyx in humans a tail

–      Coccyx: A series of small vertebrae at the end of the spinal column

–      An important attachment for various muscles, tendons and ligaments

Subphylum Urochordata - Tunicates

–      Adults are sessile

–      Larvae bear the characters of chordates

–      Class Ascidiacea – sea squirts

·       Incurrent and excurrent siphons

·       Endostyle secretes a mucous net

–      Food particles that are brought in by the incurrent siphon are trapped on the mucous net

Subphylum Cephalochordata – Lancelets (Amphioxus)

–      Slender and laterally compressed

–      Inhabit sandy coastal waters

–      Water enters the mouth, driven by cilia in the buccal cavity and pharynx

·       The water then passes through numerous pharyngeal slits where the food is trapped in mucus secreted by the endostyle

–      The nervous system is centered around a hollow nerve cord lying above the notochord

–      Closed circulatory system is fairly complex for such a simple organism

·       There is no heart, but the flow is similar to a fish’s circulatory system

·       Blood is pumped forward in the ventral aorta by peristaltic-like contractions of the vessel wall

–      It then passes upward through branchial arteries (aortic arches) in the pharyngeal bars to paired dorsal aortas which join to become a single dorsal aorta

–      From there blood is distributed by microcirculation and then collected in veins and returned to the ventral aorta

–      There are no gills specialized for respiration in the pharynx

»      Gas exchange occurs over the surface of the body

l     Subphylum Vertebrata (Craniata)

–      Most possess both an exoskeleton and endoskeleton of cartilage or bone

·       Exoskeleton develops from the skin

–      Reptilian scales, hair, feathers, claws and horns

·       A living endoskeleton

–      Allows continuous growth

–      Permits almost unlimited body size

–      A framework for efficient muscle action and attachment

–      Most vertebrates have central discs that surround the spinal cord instead of a notochord

·       Dorsal projections called neural spines are present and provide more area for attachment of segmented muscles

–      Anterior end of the nerve cord is enlarged to form a tripartite brain

·       Forebrain

·       midbrain

·       Hindbrain

·       Protected by a cartilaginous or bony cranium

–      Vastly increased respiratory efficiency

–      Muscularized gut

–      Chambered heart

l     Extinct vertebrates found in the fossil layers

–      Conodonts: Microscopic toothlike fossils used to classify geologic layers

·       In the early 1980s a complete conodont fossil was discovered

·       Resemble lancelets, but have eyes and greater cephalization

–      Ostracoderms – Armored jawless fish

·       Heterostracans:  Armed with bone in the dermis and lack paired fins

·       Osteostracans: 

–      Single piece headshield

–      Paired pectoral fins

·       Anaspids:  More streamlined than other ostracoderms

–      Armored jawed fish

·       Placoderms

–      Paired fins

–      Heavily armored

–      Diamond shaped scales or large plates of bone

·       Acanthodians

–      Paired fins with large spines

–      Larger anterior set eyes

–      Less armor than placoderms

Vertebrate Tissue types

l     Four types of tissues in vertebrates:

–      Epithelial tissues

–      Connective tissues

–      Muscular tissues

–      Nervous tissues

Epithelial tissue

l     Epithelial tissue: a sheet of cells that covers external and internal surfaces

–      Act as chemical and/or physical barriers

–      Simple (a single layer)

·       Squamous: flattened cells

·       Cuboidal:  Short, boxlike cells

·       Columnar: Cells are taller with elongated nuclei

–      The columnar cells that line the intestine are an example of a chemical barrier

–      They are selective as to which chemicals they let through to the tissues

–      Stratified: Two or more layers of cells

·       The stratified squamous cells of the skin are keratinized and act as a physical barrier to scratching, etc.

·       Transitional:  Cells can be greatly stretched

–      Example: As the bladder fills, the cells expand and as it empties the cells compress

–      Microvilli vs cilia

»      Microvilli:

·       Non-motile

·       Are used in the absorption process

·       Located on the surfaces of the columnar epithelial cells of the small intestine and kidney tubules

»      Cilia:

·       Motile

·       Are used to move cell bodies and other sweeping processes

·       Example: Fallopian tube cilia move the eggs

–      Blood vessels never penetrate into epithelial tissues

–      All types of epithelia are supported by an underlying basement membrane

»      Basement membrane: A condensed region of connective tissue matrix

·       It is secreted by both the epithelial and connective tissue cells

Connective tissues

l     Connective tissue is composed of relatively few cells and a matrix (lots of extracellular fibers suspended in a ground substance)

–      Fibers are often composed of collagen

·       Collagen is a protein of great tensile strength

–      Is the most abundant protein in the animal kingdom

l     Connective tissue types:

–      Loose: anchors blood vessels, nerves and body organs

–      Dense: forms tendons, ligaments and fasciae

·       Fasciae: sheets or bands of tissue surrounding skeletal muscles

–      Specialized connective tissue: blood, lymph, adipose (fat), cartilage and bone

·       Fibrin and platelets form a blood clot

Muscular tissues

l     The basic unit of the muscular tissues is the muscle fiber (or cell)

l     Striated muscle

–      Appears transversely striped (striated) with alternating dark and light bands

–      The appearance results from repeating bands of the proteins, actin and myosin

–      Two types of striated muscle:

·       Skeletal: Extremely long, cylindrical fibers which are multinucleated

–      Voluntary:  Can consciously control its movement

·       Cardiac: Shorter with only one nucleus per cell (uninucleated)

–      Involuntary:  Cannot consciously control movement

–      Found only in the vertebrate heart

l     Smooth (or visceral) muscle:

–      Lack striated bands

–      Involuntary

–      Long and tapering, contain a single nucleus

–      Surrounds blood vessels and internal organs such as the intestines

Nervous tissue

l     Two basic cells in nervous tissue:

–      Neurons:  receive stimuli and conduct impulses

»      It is the functional unit of the nervous system

»      A neuron consists of:

·       Cell body (soma)

–      The soma produces the enzymes needed to make the neurotransmitters

·       Nerve fibers: thin processes

–      Axon: Carries impulses away from the soma

·       There is usually one axon per neuron

–      Dendrites: Transmit incoming electrical impulses toward the soma

·       There can be one or many dendrites

–      Neuroglia:  Non-neuron cells that insulate neuron membranes, provides nutrients to the neurons and many other functions

Zoology

Fish

n     Aquatic vertebrates

n     Gill breathing

n     fins

n     Heart (except in jawless fish) consists of a sinus venosus, atrium, ventricle and conus (bulbus) arteriosus

–      Sinus venosus: a thin-walled sac that collects blood from the fish’s veins and assures smooth delivery of blood to the heart

–      Conus arteriosus: dampens blood pressure oscillations before blood flows into delicate blood capillaries

n     Single cycle circulation

–      Blood makes a single circuit through a fish’s vascular system

–      Blood is pumped from the heart to the gills, where it is oxygenated

–      Then it flows into a dorsal aorta to the body organs

–      The blood returns to the heart by veins

–      The heart must provide sufficient pressure to push the blood through two sequential capillary systems (the gills and the remainder of the body)

–      The disadvantage of the single circuit system is that capillaries offer so much resistance to blood flow that blood pressures to the body tissues are greatly reduced

n     Consists of five classes of vertebrates

–      With close to 28,000 species

n     Two large groupings:

–      Agnatha:  Jawless fish

–      Gnathostomes:  Jawed fish

Agnatha: Jawless fish

n     Jaws absent

n     Brain small, but distinct

n     Cranium present

n     Slender, eel-like, with no paired fins

n     No scales

n     Cartilaginous skeleton

n     Notochord present and vertebrate reduced or absent

n     Heart consists of a sinus venosus, atrium and ventricle

–      Sinus venosus: a thin-walled sac that collects blood from the fish’s veins

n     Includes:

–      Class Myxini:  Hagfish

–      Class Petromyzontida:  Lampreys

Class Myxini: Hagfish

n     Entirely marine

n     Feed on annelids, molluscs, crustaceans and dead animals

–      Almost completely blind, but have keen senses of smell and touch

–      Are quickly attracted to food

–      A dead whale at the bottom of the ocean will attract thousands of hagfish

–      The hagfish will feed on the whale for several years

n     Hagfish enter into a dead animal through a hole or by digging into the body

–      The two toothed, keratinized plates on the tongue fold together in pincerlike action

n     The hagfish uses this to rip bits of flesh away from the animal

–      The hagfish ties a knot in its tail, then passes the knot forward along its body

n     It presses the knot against the side of the animal for extra leverage

n     Hagfish produce enormous amounts of slime

–      If a hagfish is disturbed it exudes a milky fluid from special glands along the sides of its body

n     When the milky substances contacts seawater, the fluid forms a slime so slippery that the hagfish is almost impossible for a predator to grab

n     Have a low pressure circulatory system with a heart positioned behind the gills

–      There are three additional accessory hearts

n     The body fluids of the hagfish are in osmotic equilibrium with seawater

–      This is true of no other vertebrates

–      This is generally the case for most marine invertebrates

Class Petromyzontida – Lampreys

n     All lampreys swim up streams to breed

n     Marine forms are anadromes

–      They spend most of their lives at sea, but ascend streams to spawn

n     Small larvae, called ammocoetes, hatch from eggs

–      The larvae resemble amphioxus (lancelets) and are a model for chordate characters

n     They look more like lancelets than they look like their parents

–      The larvae are suspension feeders

n     Eventually the larvae metamorphosize into adults:

–      Eyes erupt

–      An oral disc with keratinized teeth develops

–      Fins are enlarged

–      Gonads mature

–      Gill openings are modified

n     Parasitic lampreys

n     Freshwater species remain in freshwater, but often move from streams to lakes

n     Parasitic lampreys attach themselves to fish by their keratinized teeth located in the buccal funnel

–      The buccal funnel also provides suction

–      The keratinized tongue protrudes out and rasps an opening through the hosts skin

n     Body fluid and muscle are then eaten

–      To promote blood flow, lampreys inject anticoagulant into the wound

–      After the lamprey has gorged on the fish it releases its hold and migrates to a spawning area

–      This leaves the fish with a gaping wound and can kill the fish especially if it gets infected

n     Nonparasitic lampreys, least brook lamprey, do not feed after metamorphosis

–      Their digestive systems degenerate to nonfunctional tissue

–      Within a few months they spawn and die

n     Sea lampreys do not naturally occur in the Great Lakes

–      In the early 1900s the Welland Ship Canal was constructed to allow ships to go around the Niagara Falls

–      This also allowed sea lampreys to go around the Niagara Falls and enter the Great Lakes

–      Great Lakes fish such as lake trout, rainbow trout, lake whitefish and other species were very susceptible to attack by the lampreys

–      In combination with overfishing, the invasion of the sea lamprey led to a collapse of fisheries for the above species

–      The number of sea lampreys in Great Lakes has been reduced in recent years by an aggressive program that releases chemical larvicides into the main sea lamprey spawning streams

–      Sea lampreys still take their toll on Great Lakes fish

Zoology

Gnathostomes

•       Superclass: Gnathostomata – Jawed fish

•       Jaws present

•       Paired fins

•       Three classes:

•       Class Chondrichthyes – Sharks, rays and chimaeras

•       Class Actinopterygii – Ray-finned fish

•       Class Sarcopteryii – Lobe-finned fish

•       Gnathostomes appear in the Silurean layer with jaws fully formed with no “intermediates” between jawless and jawed fish

Class Chondrichthyes – Cartilaginous fish

•       Cartilaginous skeleton and vertebrae distinct

•       Skeleton made of cartilage and there is no bone

•       The cartilage is extensively calcified

•       Large jaws

•       Teeth not fused to jaw

•       Powerful swimming musculature

•       Most are predators

•       Well-developed sense organs

•       Two subclasses:

•       Elasmobranchii

•       Holocephali

Subclass Elasmobranchii – Sharks, skates, and rays

•       Paired ventral nostrils connected to a large olfactory organ

•       Allows for long distance detection of prey (1 part per 10 billion)

•       Lidless eyes

•       Two dorsal spiracles open into the pharynx to bring water in

•       Five pairs of external gill slits allow the water to exit

•       The gills are not covered by an operculum (gill cover)

•       The front row of functional teeth on the edge of the jaw is backed by rows of developing teeth that replace worn teeth throughout the life of the shark

•       Polyphyodont: Several sets of teeth in succession

•       Heterocercal caudal fin

•       Upper lobe larger than lower lobe

•       The vertebral column turns upward and extends into the dorsal lobe of the caudal fin

•       Provides thrust and some lift as it sweeps back and forth

•       The medial part of each pelvic fin is modified to form a clasper which is inserted in the female during copulation

•       Placoid scales (denticles) covering a tough, leathery skin

•       Placoid scale:  A rectangular basal plate embedded in the skin.  Protruding from the basal plate is a backward pointing spine

•       Consists of a central pulp cavity supplied with blood vessels surrounded with dentine.  The dentine of is enclosed by enamel

•       Reduces the turbulence of water flowing along the body surface during swimming

•       Lateral line system

•       Neuromasts: Receptor organs that consist of interconnected tubes and pores along the sides of the body and over the head

•       Mechanoreceptors:  Sense low-frequency vibrations

•       Ampullae of Lorenzini:

•       Electroreceptors that sense the bioelectric fields that surround all animals

•       Located primarily on the shark’s head

•       The straight intestine contains a spiral valve that slows the passage of food and increases the absorptive surface

•       Large livers that contain a lipid called squalene which is low in density and helps keep the fish afloat

•       Rectal Gland

•       Secretes a highly concentrated sodium chloride fluid that assists the kidneys in regulating the salt concentration of the blood

•       Reproduction (all three types):

•       Oviparous: Eggs are laid soon after fertilization, the embryo develops and then hatches

•       Ovoviviparous: Developing young are retained in the uterus while they are nourished by their yolk sacs until they are born

•       Viviparous: Embryos receive nourishment through a placenta or from nutritive secretions, “uterine milk,” produced by the mother

•       Sharks

•       Chondrichthyes with a fusiform body

•       Includes:

•       Whale sharks

•       Great white sharks

•       Hammerhead sharks

•       Carpet sharks

•       Pygmy sharks

•       Rays:

•       Includes rays, skates, and sawfish

•       Most specialized for bottom dwelling

•       Dorsoventrally flattened body

•       Greatly enlarged pectoral fins

•       Large spiracles on top of head

•       Stingrays: Have slender, whiplike tail armed with one or more spines with venom glands at the base

•       Electric rays: Contain large electric organs on each side of the head which put out a high amperage current to stun prey or predators

Subclass Holocephali – Chimaeras

•       No teeth, jaws bear large flat plates                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               

•       Upper jaw completely fused to the cranium (unique in fishes)

•       Gills covered by a cartilaginous operculum to create a single external respiratory opening

•       Less abundant now than in the fossil layers

Osteichthyes – Bony fish

•       Endochondral bone

•       Bone that develops by replacing embryonic cartilage

•       An operculum made of bony plates covers the gills

•       Increases respiratory efficiency

•       Outward rotation of the operculum creates negative pressure so that water is drawn across the gills

•       Most have swim bladders

•       By displacing water with gas the fish can achieve neutral buoyancy

•       The fish can remain suspended indefinitely at any depth with no muscular effort (no energy)

•       Reproduction: Oviparous, ovoviviparous or viviparous

•       Two classes:

•       Actinopterygii - Ray-finned fish

•       Sarcopterygii – Lobe-finned fish

Actinopterygii – Ray-finned fish

•       Most have a homocercal caudal fin

•       Homocercal: Upper and lower lobes symmetrical

•       Vertebral column ending near the middle of the base

•       Fins supported by bony rays

•       Muscles controlling fin movement are within the body

•       Larval stage often very different from adult

•       Teleost fish – Modern bony fish (96% of all living fish, almost ½ of all vertebrates)

•       Cycloid scales or ctenoid scales or naked

•       Cycloid and ctenoid scales:

•       Of dermal origin

•       Made of bone, but light and flexible

•       Cycloid: Posterior margins are smooth

•       Ctenoid: Posterior margins have fine, toothlike spines

•       Naked: eels and catfish lack scales

•       Many teleost fish have pharyngeal teeth

•       Pharyngeal teeth are located on the last gill arch at the posterior region of a fish's head (under the operculum)

•       Nonteleost ray-finned fish

•       Sturgeons and paddlefish

•       A mostly cartilaginous endoskeleton

•       The only ossified bones are found in the skull, jaws, and pectoral girdle

•       Fins positioned towards the posterior and a heterocercal caudal fin

•       Lateral line and scales are absent

•       Gars and bowfin

•       Can surface to gulp air

•       This fills their vascularized swim bladder with air to supplement oxygen obtained from the water by gills

Sarcopterygii – Lobe-finned fish

•       Fins supported by stout bones and bony rays

•       Muscles controlling fin movements are within the fin

•       Diphycercal caudal fin

•       Tapers to a point

•       Vertebral column extends to the tip without upturning

•       Oviparous

•       Lungfish and coelacanths

•       Lungfish

•       Swim bladder used for respiratory gas exchange (“lung”)

•       Some species can live out of water for a long time

•       Coelacanths

•       Thought to be extinct since the Mesozoic fossil layer

•       Rediscovered in 1938

•       Swim bladder filled with fat

Zoology

Additional Bony Fish Features

Hearing in Fish

„  Fish, like other vertebrates, detect sound as a vibration in the inner ear

„  The semicircular canals are attached to three chambers

„  The lagena is the hearing receptor in fish

„  Most fish, however, do not hear well

„  The body of a fish is similar in density to the surrounding water

„  The sound waves tend to pass through the fish’s body nearly undetected

„  Catfish, minnows, and suckers hear better than most fish

„  Weberian ossicles: a set of small bones that allow them to hear faint sounds over a broader range of frequencies

„  Reception of sound begins at the swim bladder which is easily vibrated because it contains air

„  Vibrations are transmitted from the swim bladder to the inner ear (semicircular canals and lagena) by the Weberian ossicles

Taste

„  Fish have taste buds both internally and externally

„  The mouth and gill rakers are packed with taste buds

„  In catfish, the barbels, fins, back, belly, sides and even the tail contain taste buds

„  A channel catfish just 6 inches long has more than a quarter-million taste buds on its body (humans have 10,000 taste buds in their mouth)

„  Not surprising, catfish have the best sense of taste among the vertebrates

„   For instance, a catfish can taste a single drop of coke in an Olympic size swimming pool

„  Catfish tend to live in dark, murky waters where their vision isn't very useful

„  The taste buds on the barbels and other parts of the body help the fish search out food using their senses of touch and taste

„  A taste bud consists of a cluster of receptor cells surrounded by supporting cells

„  It has a small external pore through which slender tips (microvilli) of the sensory cells project

„  Chemicals being tasted interact with specific receptor sites on the microvilli

Fish Gills

„  There are four gill arches on each side of the fish

„  Each bears numerous thin gill filaments that project to the rear

„  The thin gill filaments are each covered by an epidermal membrane folded repeatedly in platelike lamellae

„  The lamellae are richly supplied with blood vessels

„  The flow of water is opposite the direction of blood flow (countercurrent flow)

„  This is the best arrangement for extracting the greatest possible amount of oxygen from water

„  Gill rakers project forward from the gill arches and strain out food and debris

„  Filter feeding fish such as herring have well developed gill rakers for capturing food

„  Most fish are carnivores as compared to filter feeders

„  Only a small proportion of fish are herbivores (feeding on plants or macroalgae)

„  Fish such as salmon, mackerel, herring, lake trout, sardines and albacore tuna contain large amounts omega-3 fatty acids (fish oil)

„  Omega-3 fatty acids from fish have been proposed to have numerous human health benefits such as reducing triglycerides and relieving rheumatoid arthritis

„  Fish, however, can not synthesize omega-3 fatty acids

„  Microalgae such as plankton produce the omega-3 fatty acids

„  The fish obtain the omega-3 fatty acids by feeding on microalgae or by feeding on fish that feed on microalgae

„  The fish then store the omega-3 fatty acids

„  This also true of krill oil (a source of omega-3 fatty acids), krill cannot produce oil, but obtain it by feeding on microalgae

Fish Migration

„  Freshwater eels are catadromous

„  They spend most of their lives in freshwater

„  Migrate to the ocean to spawn in the Sargasso Sea

„  Pacific salmon are anadromous

„  The salmon hatch out of eggs in freshwater streams and then migrate toward the ocean

„  As they move down the streams and rivers, they molt several times

„  While doing this they imprint on the vegetation and soil odors of those streams and rivers so that they can return to them

„  Pacific salmon live much of their adult lives in the ocean

„  They return to freshwater to spawn after which they die

„  Pacific salmon populations are threatened throughout the world

„  Siltation from logging and agriculture

„  Hydroelectric dams which block adults returning from the ocean to spawn

„  The lakes formed from the dams increase mortality of the juvenile salmon migrating to the ocean

Growth

„  Fish growth is temperature dependent

„  Poikilothermic (ectothermic): Body temperature fluctuates with environmental temperature

„  Fish in temperate regions (warm and cold seasons) grow rapidly in the summer when temperatures are high and food is plentiful

„  Growth in the winter nearly stops

„  Annual rings in scales, otoliths and other bony parts reflect this seasonal growth

„  Each year’s increment in scale growth is a ratio of the annual increase in body length

„  Otoliths: Small oval calcareous plates in the inner ear for sensing gravity and movement

„  Most reproductively mature fish continue to grow (although more slowly) for as long as they live

„  The annual rings can be used to determine the age of many fish

Reproduction

„  Most ray finned fish are dioecious, but are often difficult to sex using external features

„  Males usually have two long, rectangular testes that occupy a large majority of the posterior coelomic cavity especially during breeding season

„  Females typically possess a single ovary posterior to the stomach which varies in size depending on the season

„  Some species of fish, including some of the clown fish and grouper species, are hermaphrodites,

„  They naturally have both male and female sex organs

„  They are born with the ability to change their gender

„  Which can increase their chances of mating and passing on their genes

„  Intersex

„  Feminization of male fish

„  Can happen in species of fish that aren’t hermaphroditic,

„  It doesn’t help reproduction

„  In severe cases, it can make fish sterile

„  The intersex males do not outwardly appear different from normal males

„  This can interfere with mating behavior

„  In severe cases it can lead to death

„  The presence of female eggs in male testes is an indicator of intersex

„  Evidence suggests that intersex in fish may be the result of pharmaceuticals (Ex: birth control pills), pesticides (Ex: the herbicide, Atrazine), and personal care products that move into aquatic environments

„  A survey of fish in 19 national wildlife refuges in the Northeastern U.S. indicted that 60 to 100 percent of all the male smallmouth bass had intersex conditions

„  Another study of the Shenandoah and Potomac Rivers found intersex conditions in more than three-quarters of male smallmouth bass

„  Higher than normal levels of vitellogenin occured in the blood of the male fish

„  Vitellogenin is a protein produced by female fish to form egg yolk and is normally absent in males

„  The gene that tells the body to produce vitellogenin is usually “turned off,” in male fish

„  That gene only “switches on” in the presence of estrogen, a female sex hormone

Tremendous Variation in Teleost Fish

„  Three groups of deep-sea fishes, tapetails, bignose fishes, and whalefishes, were so different in morphology that they were assigned to three different taxonomic families

„   It has now been determined that they are the larvae, males, and females, respectively, of a single species