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ANATOMICAL TERMINOLOGY + GENERAL STUFF
SYMMETRY - a body pattern of similarity
* Spherical symmetry: the animal can be bisected through any plane that passes through its center point (i.e. Volvox) - this is the most primitive type of symmetry
* Radial symmetry: the animal can be bisected into equal halves when a plane cuts through a central line (i.e. anemones, jellyfish)
* Bilateral symmetry: the animal can be bisected by one plane into relatively equal halves - the plane must go through a central line for symmetry to occur (i.e. planarians, vertebrates)
* Closed circulatory system: blood is contained within a system of blood vessels
* Open circulatory system: blood kind of just pools within the body
KINGDOM ANIMALIA
* Multicellular eukaryotic heterotrophs
* Does not contain prokaryotes, protists, fungi, or plants + lack a rigid cell wall
* Most (except for sponges) ingest and digest food in an internal cavity and are composed of cells divided into organs and tissues
* 2 main groups: Invertebrates (without a backbone) and vertebrates (with a backbone)
ESSENTIAL LIFE FUNCTIONS
* Feeding: a way to gather food
* Respiration: a way to obtain oxygen from the environment
* Internal transport: circulation - moving nutrients from one area of the body to another
* Excretion: removal of nitrogenous waste from the body
* Sensitivity (responding): nervous system: used to sense + gather information form the environment
* Reproduction: a way to generate offspring
* Movement: self-explanatory
COELOM
* The space between an animal’s outer covering (epidermis / ectoderm) and the lining of the gut (endoderm)
* Acoelomates - animals without a coelom (i.e. flatworms, cnidarians)
* Pseudocoelomates - animals with a “false” coelom (i.e. roundworms)
* Coelomates - animals with a “true” coelom (i.e. annelids + vertebrates + most bilaterally symmetrical organisms)
PHYLUM PORIFERA
* Sponges -
* Invertebrates: some are radially symmetrical, some have no symmetry at all
* Aquatic, mostly marine
* No specialized tissue or organs: essential life functions take place at a cellular level
* Filter feeders: they sift particles from the water to obtain nutrients
Anatomy:
* Central cavity: an area enclosed by the sponge’s body
* Osculum: dorsal hole through which water exits the sponge
* Porocytes: cells through which water enters the sponge
* Pores: thousands of openings that allow water to enter
* Epidermal cells: outer, surface cell layer
* Spicule: “skeletal” support, made of silica or calcium
* Amebocytes: cells that produce the spicules
* Choanocytes: cells facing the inside of the sponge’s body with flagella (whip-like appendages used for locomotion) that create water currents and trap food
Form + function:
* Feeding: filter feeders: nutrients are trapped by the choanocytes
* Internal transport: the water that is pulled through the sponge acts as a transport system
* Excretion: also carried by water movement
* Respiration: oxygen and carbon dioxide are absorbed through the water
* Reproduction: both sexual and asexual -
* Sexual reproduction: hermaphroditic - sponges produce both male and female gametes, but they are not self-fertilizing
Eggs produced + kept, then are fertilized - forms larva, which become planktonic
* Asexual reproduction: small, new growths break off the main sponge (budding) which produces genetically identical offspring.
PHYLUM CNIDARIA
* aka Coelenterate: ex. jellyfish, hydra, anemones, coral
* Aquatic, soft-bodied invertebrates
* Acoelomates w/ radial symmetry
* Earliest example of specialized cells + tissue: nematocysts are specialized stinging cells located on the tentacles of jellyfish - they have dart-like structures which are triggered by touch and deliver poison to kill prey
Body shapes:
* Polyp: hydra, anemones, coral: sessile, flower-like
* Medusa: jellyfish, man of war: free-swimming, planktonic, bell-shaped
Structure + function:
* Tentacle: finger-like projections that contain the nematocysts and bring prey items to the mouth
* Mouth: opening through which prey items enter the gastrovascular cavity
* Gastrovascular cavity: “stomach” - where digestion occurs
* Body wall w/ three layers:
1. Ectoderm: epidermis
2. Mesoglea: mesoderm - jelly-like, acellular
3. Endoderm: gastroderm - secretes digestive enzymes into the gastrovascular cavity
* Basal disk: sticky base that attaches to the substrate and holds the polyp in place
Physiology:
* Digestion: incomplete digestive system
* Internal transport: no specialized tissue, thin enough for substances to move freely
* Excretion + respiration: no specialized tissue, thin enough for diffusion to suffice
* Nervous system: primitive network of nerves, no true “brain” or central system
Reproduction:
* Both sexual and asexual reproduction: asexual reproduction is through budding, the same as sponges
* Hermaphroditic, but not self-fertilizing
PHYLUM PLATYHELMINTHES
* Flatworms: tapeworms, blood flukes, planaria
* Acoelomates, invertebrates - most simple bilaterally symmetrical organisms
* Simplest organism w/ cephalization + a tail region
* Mostly aquatic - either free-living or parasitic
Flatworms:
* “Planarians” - a free living example of platyhelminthes
* Dorsoventrally flattened, hermaphroditic
* Circulation and respiration take place through diffusion
* Incomplete digestive system
* Excretory system: flame cells that propel wastes out of the body
* Nervous system: anterior cerebral ganglia functions as a brain, longitudinal nerve cords, some lateral nerves + light-sensing eye spots.
* Muscular system: under epidermis, w/ both circular and longitudinal muscles.
* Reproduction: both sexual (they are hermaphroditic) and asexual (through fission + regeneration)
Tapeworms and blood flukes:
* Parasitic
* Complex, multi-host life cycles
* Can be over 30 feet in length: their eggs and larvae can be found in uncooked fish + meat
* No digestive system: nutrients are absorbed
* Scolex: anterior head region with hooks and suckers that attaches to their host’s intestinal wall.
* Proglottids: extending from the neck region, containing the reproductive organs. Each mature proglottid can release thousands of fertilized eggs into the host’s digestive tract.
PHYLUM ANNELIDA
* Segmented worms: i.e. earthworms, marine worms, leeches
Class oligochaeta (earthworms):
* Earthworms fertilize the soil by taking in organic matter + eliminating the wastes
* Annelids have a closed circulatory system which transports oxygen, carbon dioxide, etc.
* Circulation: dorsal + ventral blood vessels, five pairs of aortic arches
* Skin must remain moist for an earthworm to breathe, otherwise diffusion cannot occur
* Nephridia are excretory tubules beneath the skin used to remove nitrogenous waste from the body
* Nervous system: ganglia + nerve cords
* Several ganglia form together to form a makeshift “brain”
* No specialized sense organs
* Hermaphroditic, but not self-fertilizing
* Mating occurs when two worms fuse their bodies together at the clitellum
* They exchange sperm which is then stored in the seminal receptacle
* After several days, the clitella secrete a tube made of mucus and chitin - fertilization occurs within the tube, which then closes to form a protective case.
* The worms develop for 2 to 3 weeks before hatching.
Class polychaeta (marine annelids):
* They have paired, paddle-like appendages tipped with setae
* “Polychaete” translates to “many bristles”
* They differ from other worms in that they have antennae and specialized mouthparts.
* Polychaetes are mostly predatory and feed on smaller, weaker animals
* Most polychaetes breathe using gills
Class hirudinea (leeches):
* Smallest class of annelids (around 300 species)
* They primarily live in freshwater but can also live in rainforests and swamps
* Leeches are external parasites that suck the blood and body fluids of their host
* At the anterior end there is a sucker that attaches to the host’s body
* Leeches can secrete an anesthetic that prevents their hosts from feeling them, and a substance that prevents the blood from clotting
* Leeches can be used for medicinal purposes, by sucking out blood clots from a wound
PHYLUM NEMATODA
* Roundworms: i.e. ascaris, hookworms, pinworms
* Bilaterally symmetrical pseudocoelomates
* Both free-living and parasitic, aquatic and terrestrial
* Some of the most abundant organisms that exist
* The simplest invertebrates with a complete digestive system
* They lack circulatory + respiratory systems and have primitive excretory cells
* Muscular system: only longitudinal muscles, can move back and forth but require something to push against to go forward
* Nervous system: main ventral nerve cord
* Sexual reproduction, distinct sexes (male + female)
PHYLUM ECHINODERMATA
* “Spiny-skinned” animals - sea stars, sea urchins, sea cucumbers, sand dollars
* Aquatic invertebrates, mostly marine - pentaradial symmetry
* Most have a spiny, hard endoskeleton consisting of calcium carbonate plates called ossicles, covered by a thin layer of skin.
* Internal water vascular system - controls the tube feet, allowing for mobility and helps open the shells of prey items, such as clams and oysters
* Incomplete digestive system
* Lack excretory and respiratory systems - excretion and respiration take place through diffusion
* Able to regenerate
* Coelomates, lacking a centralized nervous system
* Have simple, light-sensing eyes called ocelli
* Most reproduce sexually, but some reproduce asexually through fission
* Divided into three main classes: asteroidea (sea stars), echinoidea (sea urchins, sand dollars) and holothuroidea (sea cucumbers)
Water vascular system:
* Need to know how the flow works, sadly:
* madreporite - stone canal - ring canal - radial canal - lateral canal - ampullae - tube feet
PHYLUM MOLLUSCA
General characteristics:
* Unsegmented, soft bodied organisms w/ bilateral symmetry
* Shell formed by mantle secretions
* Body is often protected by a valve / shell
* Separate sexes
* Both aquatic and terrestrial
* Complete digestive system
* Gastropods and bivalves have an open circulatory system, while cephalopods have a closed circulatory system
Classification:
* Based on the presence / absence of a shell, number of shells present, and the type of feet
* Gastropoda: “stomach foot” - one shell - slugs, snails, abalone, nudibranchs
* Bivalvia: “two folding doors” - two shells - clams, scallops, mussels, oysters
* Cephalopoda: “head foot” - squid, octopus, cuttlefish, nautilus
Class gastropoda:
* Most have one valve, some have no valves at all
* Feeding with a cat tongue-like radula
* Movement: creeping on a single foot
* A tight-fitting, trapdoor-like plate called an operculum is attached to the foot that can be closed to protect the animal
Class bivalvia:
* 2 shells secreted by the mantle
* Edges of the mantle have sensory tentacles and/or eye spots
* Muscular foot, no radula present
Class cephalopoda:
* Squid, cuttlefish, octopus, nautilus
* Shell either extremely modified or absent
* Most intelligent invertebrates, well-developed vision
* All members of this class have arms or tentacles, and are all marine predators
* Octopus: no shell present, foot modified into 8 arms
* Squid: shell modified into flexible internal “pen”
* Cuttlefish: internal hard shell
* Nautilus: external shell, many small tentacles
PHYLUM ARTHROPODA
* Largest phylum of invertebrates: around 80% of earth’s living species (or around 1 million) are part of this phylum
* Insects, spiders, lobsters, centipedes
General characteristics:
* Segmented body divided into head, thorax, and abdomen
* Appendages on at least one segment - they can be used for feeding, reception, defense, and locomotion. Antennae and mouthparts are considered modified appendages.
* Nervous system present
* Hard exoskeleton made of chitin that provides protection and resistance to drying out. They shed it in a process called molting in order to grow.
* Open circulatory system
* Complete digestive system
* Aquatic arthropods have gills for gas exchange, while terrestrial arthropods have special internal surfaces.
* “Arthropod” translates to “jointed feet”
Development:
* Incomplete metamorphosis: egg - nymph - adult
* Complete metamorphosis: egg - larva - pupa - adult
Life functions:
* Respiration: by gills or tracheal tubes
* Circulation: hearts pumping through an open system
* Excretion: malpighian tubules in most terrestrial arthropods, diffusion w/ “green glands” in marine arthropods
* Nervous system: well developed - antennae, ocelli, compound eyes, tympanum and cerebral ganglia function as the brain
* Reproduction: separate sexes
Classification:
* Insecta: 3 segments, 6 legs
* Arachnida: spiders, ticks, mites, scorpions
* Crustacea: crabs, lobsters, barnacles, crayfish, pill bugs
* Chilopoda: centipedes
* Diplopoda: millipedes
Class chilopoda:
* Many segments, one set of legs per segment
* Long worm-like body
* Carnivorous
Class diplopoda:
* Many segments, two sets of legs per segment
* Long worm-like body
* Herbivorous
Arachnida:
* 2 body segments - cephalothorax + abdomen
* 4 pairs of legs
* No antennae
* Respiration through “book lungs”
Crustacea:
* Typically 2-3 body segments
* 5 or more paired appendages
* Mouth parts formed by appendages called mandibles
* Typically aquatic
Insecta:
* All six-legged arthropods with 3 body segments
PHYLUM CHORDATA
* All chordates must possess the following characteristics at some point within their life cycle to be considered a chordate: a dorsal nerve cord, a notochord, gill slits, and a post-anal tail
* Dorsal nerve cord: tubular in shape, runs along the back
* Notochord: thin, flexible supporting rod, mostly only present during development
* Gill slits (aka pharyngeal pouches) - paired structures in the throat region
* Tail - muscle / bony structure extending past the anus
Classification:
* Urochordata - tunicates
* Cephalochordata - lancelets
* Vertebrata - vertebrates
Subphylum urochordata (tunicates):
* Soft bodied marine organisms
* Sessile during adulthood
* Filter feeders - gill slits trap food + absorb oxygen
* Nerve cord and notochord are only present during development
* Commonly referred to as “sea squirts”
Subphylum cephalochordata (lancelets):
* Marine filter feeders, gill slits trap food + absorb oxygen
* Mobile: adults have all four chordate characteristics
* Fish-like
Subphylum vertebrata (backboned animals):
* Most numerous and complex subphylum of chordates
* 7 classes: agnathis, chondrichthyes, osteichthyes, amphibia, reptilia, aves, mammalia
* Spinal column replaces notochord, anterior end of nerve cord modified into a brain
* Body divided into head, neck, trunk
* 2 pairs of appendages
* Heart w/ 2-4 chambers
* Respiration through gills/ lungs, closed circulatory system
* Endothermic or exothermic (cold / warm-blooded)
* Endoskeleton made of bone or cartilage, a tough collagenous tissue
* An endoskeleton made of bone rather than cartilage allows animals to grow larger and heavier
* Most vertebrates have skin covered with scales, feathers, fur, or hair - they serve a variety of functions such as insulation or waterproofing
* Adaptive immune system - vertebrates can learn to recognize specific pathogens
Reproduction:
* Ovipary: development of an embryo within an egg outside of the mother’s body - found in most amphibians + reptiles and all birds
* Ovovivipary: development of an embryo inside an egg within the mother’s body - found in some fish and reptiles
* Vivipary: embryo develops inside the mother’s body, with a period of parental care after birth - found in almost all mammals
Fish:
* Water-dwelling, usually with gills, scales, and fins
* 3 main groups: agnatha - jawless fish, chondrichthyes - cartilaginous fish, osteichthyes - bony fish
Class agnatha (lampreys, hagfish):
* “Agnatha” - “without jaw”
* Some do not consider them a true fish (they do not have a backbone)
* Marine + freshwater - either parasitic or scavengers
* External fertilization
* Eel-like body - 2 brains and 4 hearts (1 main brachial heart, 3 accessory hearts pump blood to the body)
* Round, suction cup-like mouth with teeth, used to bore into their host
* Lampreys are generally parasitic, hagfish are generally scavengers
Class chondrichthyes (sharks, skates, rays):
* Skeleton entirely made of cartilage, only teeth are calcified
* Backbone present
* Internal fertilization
* 2-chambered heart
* Skates and rays have flattened, wing-like bodies, some with whip-like tails and poisonous spines
* Largest example of this group is the whale shark, which can grow up to 40 feet in length - feeds on plankton
* Ampullae of Lorenzini: tiny, pore-like electroreceptors which are used to detect the magnetic fields of nearby organisms
Class osteichthyes (i.e. salmon, tuna, bass):
* Largest class of vertebrates - bony gill plate + skeleton
* Air / swim bladder adjusts their density
* Complete digestive system, external fertilization
* Oviparous / ovoviviparous
* 2-chambered heart
* Lateral lines - a sense organ to detect movement, pressure, and vibrations in the water
* Ray-finned fish: fins are thin and web-like - skin over flexible, bony spines
* Lobe-finned fish: fins resemble stumps of limbs
Class aves (birds):
* Endothermic, feathered vertebrates
* 4- chambered heart
* Egg-laying
* Nearly hollow bones, limbs adapted for flight
* Bipedal tetrapods
* Their eggs are amniotic, with hard calcium carbonate shells
* Although not all living birds can fly, they all evolved from ancestors that could.
* Two basic types of feathers: flight feathers are long, stiff and waterproof: down feathers are short + fluffy and are used for insulation.
* Instead of teeth and jaws, they have a beak made of keratin. Birds’ hearts are relatively large and beat rapidly.
* Like earthworms, birds also have a crop and a gizzard
* Contour feathers provide a streamlined shape
* Skeletons are modified: fused vertebrae and pelvis, large sternum
Class reptilia (reptiles):
* Crocodiles, alligators, turtles, tortoises, lizards, snakes
* Well adapted to life on land, ectothermic
* Keratin scales
* On-land breeding - eggs w/ a leathery shell
* Young born live
* Internal fertilization
* Well developed lungs + protective rib cage
* No metamorphosis, unlike amphibians
Order squamata (lizards, snakes):
* Movable eyelids in lizards, snakes without
* Shedding skin for growth
* Thick, overlapping scales
* Largest lizard: komodo dragon
* Largest snake: anaconda
* Lizards are generally not poisonous except for gila monster + bearded dragons
* 200 out of 2500 known species of snakes are poisonous
Order crocodilia (crocodiles, alligators, gharials, caimans):
* Largest living reptiles - can exceed 7 meters in length
* Alligators: broad, rounded snout: teeth hidden when jaw is shut
* Crocodiles: pointed snout: teeth exposed when jaw is shut
* Females protective of nest + offspring
* Ectothermic
* 4-chambered heart
Order chelonia (turtles, tortoises, terrapins):
* Shells are bony developments from the ribs with bone plates called scutes
* No real scientific distinction between turtles, tortoises, and terrapins, but generally:
* Turtles are aquatic and predatorial
* Tortoises are terrestrial and herbivorous
* Terrapins are technically just a type of turtle but are more terrestrial than regular turtles
Class mammalia:
* Endothermic vertebrates w/ fur or hair
* Nurse offspring with milk (mammary glands)
Teeth modified, with incisors, canines, molars, and premolars
* Young are born live, except for Monotremes
* 3 main groups based on how offspring develop:
* Monotremes - egg layers
* Marsupials - pouched mammals
* Placental mammals
Order monotremata (echidna, platypus):
* “One opening”
* Cloaca - a single opening at the posterior end of the animal where the excretory, digestive, and reproductive systems all end up
Order marsupialia (i.e. kangaroos, koalas):
* Offspring are born at a VERY early stage in development - they climb up the mother’s body into the pouch, where they develop for another 9 months
Placental mammals (i.e. humans, rodents, cats):
* The placenta is an organ that connects the embryo with the mother’s uterus
* It allows for the exchange of gases, nutrients, and waste
* Longer protected embryonic development: up to two years in elephants
* Amniotic sac + amniotic fluid: acts as a shock absorber that protects the embryo
* Longer gestational period means more developed offspring when they are born
* Precocial: mature, developed offspring at birth - able to move shortly after birth
* Altricial: offspring are unable to feed or care for themselves at birth - their eyes are often closed and/or they are otherwise underdeveloped
* Teeth modified:
* Incisors: slicing
* Canines: tearing
* Premolars + molars: grinding
* Carnassial (only found in carnivores): cutting + breaking