cell membrane

Surface membrane bleb (2 layers)

The macronucleus: metabolism, development, and membrane organelles

Micronucleus: sexual reproduction

Asexual reproduction (good conditions)

Sexual reproduction (harsh conditions)

Quinine (side effect: heart inhibitory effect) is extracted from the bark of the cinchona tree

Artemisinin is extracted from Artemisia annua

Acanthus

trumpet bug

clockworm

amoeba

Foraminifera (pseudopods protruding from the shell mouth or small holes in the shell)

Euglena (freshwater)

Noctiluca (fish gills): The fish dies due to lack of oxygen. After death, the algae consume a large amount of oxygen and release toxins.

Hairworms (termites): eat wood and buildings

Trypanosomiasis (blood): sleeping sickness

complete cleavage

incomplete cleavage

ectoderm

mesoderm

endoderm

single groove system

Double ditch system

complex ditch system

Primitive cells: differentiate into other types of cells

awn cells

Collagen fibers

Bone spicules

body wall

Hydra

hook-hand jellyfish

Yabuzhi Polyps

Peach Blossom Jellyfish

Moon jellyfish (massive reproduction in polluted areas): fertilized eggs → floating larvae → polypoid larvae (falling to the bottom of the sea) → row bodies → disc-shaped larvae

jellyfish

Green wart anemone

sea ​​gills

sea ​​cockscomb

coral

skin muscle bursa

Muscles that connect the dorsum and abdomen (maintain body shape)

Abdominal cilia (glandular cells secrete mucus and cilia move forward)

Feeding and digestion

Epithelial layer syncytium (no clear boundaries between cells, only cell membrane and cytoplasm)

Muscle layer (nuclei settle into the muscle layer)

Feeding and digestion

Epithelial layer

Muscle layer (nuclei settle into the muscle layer)

Feeding and digestion

planarian

Clonorchis sinensis

tapeworm

planarian

Monenterales

Trichomonales

polyenterata

Clonorchis sinensis

Fasciolopsis brucei

Schistosoma japonicum

third generation insects

head

foot

mantle

visceral mass

stratum corneum: scleroprotein, marginal secretion

Prismatic layer: calcareous, marginally secreted

Nacre: Calcium and chitin, secreted throughout the mantle

trocarid larvae

Facial disc larvae

Gamma larvae

Shell top, front end, rear end, ventral edge

Drilling in the sand: The blood is squeezed forward, forming a mao-like structure, pulling itself into the sand, and then stretching and pulling. Only the outlet pipe is left outside to complete breathing and feeding.

adductor muscle

gill

Feeding and digestion: gills → mouth → stomach → rectum (through the pericardial cavity) → anus

open tube circulation

Excretion: The kidneys filter and excrete through the kidney pores and out of the body through the outlet pores.

Reproduction: gonads, reproductive ducts

chiton

No hinge teeth, one row of hinge teeth, 3 main teeth

In addition to hinged teeth, bivalves are classified based on: how many radial ribs there are, whether there are growth lines, and traces of the anterior adductor muscle after opening (round, heart-shaped, triangular, etc.)

Pearl oysters, Chlamydia scallops (the adductor muscles are eaten), oysters, mirror clams, razor clams, and clams

squid

Nautilus: 4 gills, 4 kidneys, 4 auricles, 400 million years ago

giant squid

Octopus (octopus): 8 arms, not much endoskeleton

The movement is completed by contracting the abdominal muscles

The largest one at the bottom: whorl layer; the top one: whorl part

Flat jade snail (worm grub)

Bao: Its shells can be used as medicine, which is Cassia seed.

Baby: It used to be a currency

Apple snail: intermediate host of Angiostrongylus cantonensis, biological invasive species

Brown cloud snail (African giant snail): biologically invasive species

Nudibranchs: Manatees eat corals, sea anemones, etc., and then transfer stinging cells to their own nudibranchs.

Non-vegetative species: Aplysia (herbivore), Aplysia leucophylla (swallowing algae to extract chlorophyll, photosynthesis)

Sectioning: inside → outside; back → front

The left and right body cavity membranes meet to form the mesangium; the front and rear body cavity membranes meet to form the septum.

Setae: through the synergistic action of muscles and nervous system.

Verrucopodia: a complex synergy of muscles, setae, and coelomic fluid.

structure

Function

The color of the back is similar to the environment

Internodal groove: the groove between nodes

Annulus: body segments XIV to XVI

External→Internal: parietal coelomembrane, visceral coelomic membrane, longitudinal muscle, circular muscle, ectoderm, endoderm

body wall

intestinal wall

Respiration: Respiration is completed through the body wall. Oxygen is first dissolved in the mucus of the body wall, and then penetrates into the blood in the capillaries in the body wall. Carbon dioxide in the blood is also excreted through the body wall. Therefore, the body wall of the worm can secrete mucus to keep the body wall moist at all times to ensure normal breathing and reduce friction with the soil.

Blood circulation (closed tube circulation)

excretion

nerve

hermaphroditic, heterosexual mating

Male reproductive organs: testicular sac, seminal vesicle, vas deferens, prostate

Female reproductive organs: ovaries, egg funnel, fallopian tubes, spermatheca

When the adult becomes sexually mature, the girdle will secrete mucus during the reproductive period to form an egg cocoon.

Nereis

Amaranthus spp.

Tremorworm

love trumps earthworms

Leeches

South American leech (herbivorous)

Echinococcus uniannularis: The adult is not segmented, while the larvae are segmented and have a well-developed body cavity.

Cross

Cuticle: This is the outermost layer of the body wall, well developed and somewhat elastic.

Epidermis: Also called the epithelial cell layer, it lies beneath the stratum corneum and forms the syncytium.

Muscle layer: This is the innermost layer of the body wall, with only the thicker longitudinal muscle layer and no circular muscle layer. It can only swing, not telescopic movement.

Foregut and hindgut: formed by invagination of ectoderm with cuticle on the inner wall. The foregut includes the mouth, buccal cavity, and pharynx (esophagus), and the hindgut includes the rectum and anus.

Midgut: A layer of cells derived from the endoderm that digests and absorbs food.

Intestinal granules: There are a large number of granular structures in the intestinal wall cells of nematodes, called intestinal granules. The interior of the intestinal granules is an acidic environment and participates in endocytosis. It is similar to lysosomes, but larger in size.

The vast majority of nematodes are dioecious, with some terrestrial rod nematodes and many plant nematodes being hermaphroditic.

Some nematodes have only female worms and no male worms are found, so they reproduce parthenogenetically.

Male: testes, vas deferens, seminal vesicles (opening in the cloaca, and the anus opening outside the body) and muscular ejaculatory ducts. The ejecta duct is connected to the end of the digestive tract and is also called the cloaca.

Female: Generally double-tubular, with a few single-tubular, including ovaries, fallopian tubes, and uterus. The union of the two uteruses forms the vagina.

Infection mode: Bite through the skin and enter the bloodstream (bite through the intestinal epithelium)

Parasite site: small intestine

Ancylostoma americana has one pair of teeth; Ancylostoma duodenale has two pairs of teeth.

Mode of infection: Injection of filarial larvae when bitten by Culex and Anopheles mosquitoes

Parasite site: lymphatic system. Lymphatic vessels are blocked, and the retained lymph stimulates the skin to become thicker and harder.

Wudzeri bancrofti, Brucella malayi - lymphatic filariasis, ivermectin reduces the incidence.

Onchocerciasis - river blindness

free life

The development of each somatic cell can be tracked (body transparency)

Bi-branched appendages: primary limb, inner limb, outer limb

Single appendage: base, turn, leg, tibia, tarsus, pretarsal (segment)

Head: feeding, feeling

Chest: sporty

Abdomen: houses internal organs, reproduction

Cephalothorax and abdomen, cephalothorax and abdomen, cephalothorax and abdomen (the abdominal appendages have basically degenerated, leaving only trace organs)

Epidermal cells secrete to form exoskeleton

Upper epidermis layer: wax layer (waterproof)

Outer layer: calcium layer or protein (defense)

Inner epidermis: Chitin layer (increases flexibility and defense)

age calculation

No molting. First instar larvae, molt once. Second instar larvae...

Molting process: Epidermal cells secrete enzymes to digest and reuse the chitin layer and protein layer. The wax layer is not used and continues to dissolve while the inside continues to grow, cracking the outer bones to complete molting.

Head: Eyes, a pair of compound eyes and three single eyes. The compound eye is composed of many small eyes (which image independently without interfering with each other) and are sensitive to moving objects.

Head: antennae, sense of touch and smell. Inner → Outer: shank section, stem section, whip section (whip section is composed of many sections)

Head: mouthparts. Upper → Lower: upper lip, upper jaw (large jaw), lower jaw (small jaw), lower lip.

Thorax: 3 segments; 2 pairs of wings; 3 pairs of legs (6 segments); 2 pairs of valves. The spines on the feet rub against the wings to produce sounds.

Abdomen: 11 body segments; 1 pair of hearing organs; 8 pairs of valves.

digestion and excretion

blood circulation

reproduce

Central Nervous System

prawns

New Penaeus prawn (Jiwei shrimp): There are many pigments in the body, but they are all decomposed at a certain temperature. Only astaxanthin has the highest melting point and is not decomposed.

Procambarus clarkii (crayfish), biologically invasive species

Scar palm sand crab

Japanese big eye crab

Portunus trituberculatus

Chinese mitten crab

Barnacles: on reefs, resistant to high temperatures and drought

Daphnia flea: It uses its tentacles to stir up the water and move around. Eggs develop inside the body

Spiders have venom in their pincers. When the prey falls on the spider web, the spider senses the direction through vibration, goes to the prey and spins silk to wrap it and inject venom. It waits for the insect to die and then injects digestive juices. The soft parts of the prey are digested and dissolved into liquid. Since the prey has an exoskeleton, The exoskeleton cannot dissolve, forming an envelope of digested material that the spider sucks up with its mouth (by pumping the stomach in and out).

Scorpion, front abdomen, back abdomen, sting (venom). Ctenoid organ: There are sensory cells and sensory organs on the ventral side of the tooth.

tick mite

Horseshoe crab, respiratory organ: book gills

Sea spider: 4 single eyes, vestigial abdomen, egg-carrying legs, snout

Centipede

Road

Antenna types: bristly, filamentous, bead-shaped, serrated, double comb-shaped, awn-shaped, gill-flap-shaped, knee-shaped, hammer-shaped, ring-hair-shaped, club-shaped, etc.

Mouthpart type: chewing mouthparts, also specialized into sucking and siphoning mouthparts

Foot types: walking, jumping, catching feet, swimming feet, hugging feet, digging feet, powder collecting feet, etc.

Wing types: membrane wing, elytra, semi-elytra, lepidoptera, etc. The classification of wings also depends on the basis of wing veins and wing chambers.

perverted type

Adult echinoderms have a water duct system, including external tube feet.

Through the catheter and the tube foot, various functions are realized, such as movement through the bending of the wrist and the suction cup at the end of the tube foot; circulation is achieved through the transmission of body cavity fluid in the catheter.

sea ​​fern

sea ​​lily

Hair, main functions: insulation, touch

skin glands

Claws, nails, hooves

horn

skull

spine

Belt and limb bones

The limbs are well muscled to adapt to various activities of the limbs.

The unique diaphragm is formed by the occurrence and downward movement of the subaxial muscles of the neck, and participates in forming the diaphragm that separates the chest and abdominal cavities; the contraction and relaxation of the diaphragm participate in breathing actions.

The skin and muscles are well developed, allowing the animal to shake its skin and curl up. In primates, facial skin muscles are greatly developed and become expression muscles to express emotions. Expression muscles are particularly developed in humans.

The head has powerful masticatory muscles attached to the zygomatic arch to complete prey hunting, biting and chewing, so that the mouth has physical digestion and other functions.

The rectus abdominis muscle in the abdomen still retains its original segmented state.

The digestive system is well differentiated. The digestive tract includes the oral cavity, pharynx, esophagus, stomach, small intestine (duodenum, jejunum, ileum), large intestine (cecum, colon, rectum), and anus.

Digestive glands include salivary glands, liver, and pancreas.

Monogastric: Insectivores and carnivores have single-chambered stomachs, short digestive tracts, and degenerated cecum.

The stomach (ruminant stomach)

respiratory tract

Lungs: composed of a complex bronchial tree and the alveoli at the blindest end. The alveoli are gas exchange sites with a large gas exchange area that can effectively absorb the required oxygen from the air.

The heart is divided into 4 chambers, with complete double circulation, and oxygenated blood and hypoxic blood are completely separated.

Arteries: Mammals only have the left body arterial arch, which curves back to the dorsal aorta and reaches the tail end.

Veins: The main blood vessels tend to be simplified (most mammals only retain the right anterior great vein), and the renal portal vein is completely degenerated, which accelerates blood circulation, increases blood pressure, and improves circulation efficiency.

lymphatic system

reproductive organs

Reproductive cycle: Most mammals mate seasonally, usually in spring or winter.

Reproductive mode

brain

senses

The only mammal that lays eggs. It originated more than 130 million years ago and is only produced in Australia.

Teethless, with horny sheath

Have cloaca

No nipples

oviparous

platypus, echidna

Special-shaped teeth, many incisors

residual cloaca

Has nipples, in the brood sac

viviparous, without placenta

Red kangaroo, koala, thylacine, quoll

Special-shaped teeth, few incisors

No cloaca

There are nipples, obvious, on the chest, groin or abdomen

viviparous, with placenta

Insectivorous order, Tree shrews, Chiroptera, Primates, Lepidoptera, Rodents, Lagomorpha, Carnivora, Cetaceans, Pinnipeda, Proboscidea, Perissodactyla, Artiodactyla, Siratea

The lower jaw is composed of a single tooth

Molars have 3 cusps arranged in a straight line

Feathers: rachis, vanes, barbules, barbules. Molt every year.

Horny beak, claws, scales

axial skeleton

Belt and limb bones

Back muscles: tend to degenerate due to the healing of the spine beyond the thoracic spine.

Neck muscles: The neck muscles are well developed and enable the neck to complete fine movements in many directions.

Chest muscles: Very well developed. The chest muscles are divided into the superficial pectoralis major muscle and the deep superior coracoratus muscle (also known as pectoralis minor). They control the flapping and raising movements of the wings respectively. They are a pair of antagonistic muscles.

Hind limb muscles: Because birds rely on their hind limbs to walk and support their weight on land, the motor muscles of their hind limbs are very developed. The hind limbs have muscles suitable for perching on trees and holding branches. These arboreal-related muscles (such as perforator muscles, flexor digitorum muscles and peroneus medius) can use the ingenious cooperation between tendons, muscle sheaths and bony iliac joints to allow birds to perch on branches. Due to the pressure of body weight and the bending of leg bone joints, the tendons related to toe flexion are tightened, and the toes naturally bend to grasp the branches tightly.

air bag breathing

double breathing

The vocal organ of birds is located at the bottom of the trachea and is called the syrinx.

Syrinx: The syrinx is composed of multiple enlarged rings of cartilage on the trachea. The inner and outer walls of the bifurcated part of the syrinx become thinner and can produce sounds with the vibration of the air flow, which is called the syringe membrane. There is a sound bone in the middle of the bifurcation of the syrinx, and a leaf-like membrane extends along the sound bone, called the meniscus. This structure vibrates and produces sounds with exhalation and inhalation.

How the sound is produced: Like the larynx of mammals, the passage of gas through the vocal organ causes vibrations, thus producing sound. Due to the presence of syringes, some birds, such as parrots and mynas, can make relatively complex sounds and even imitate human speech.

Screaming muscles: Parrots imitate human speech sounds, mainly because they have well-developed syrinx and syrinx muscles. Parrots have three pairs of song muscles. Because the left and right vocal muscles are innervated by different nerves, many birds can emit two completely different frequencies of sound waves at the same time.

Beak: Main feeding tool. The shape of the bird's beak and tongue varies depending on the species, feeding habits and foraging methods. For example, the beak and tongue of ducks are flat and flat, making it easy to feed on aquatic plants and plankton in the water.

Esophagus: Located between the bird's pharynx and glandular stomach, on the dorsal side of the trachea, and accompanying the trachea, it is an easily dilated muscular tube. The diameter of the esophagus is related to the size of the food swallowed by the bird, and the esophagus itself has no digestive function. Its main function is to transfer food from the pharynx to the stomach.

Crop: The crop is a specialized sac-like structure formed by part of the esophagus. Its structure is similar to that of the esophagus. It is mainly used for temporary storage and softening of food.

Stomach: includes the glandular stomach at the front and the gizzard at the back. There are digestive glands in the glandular stomach that secrete digestive juice and have the function of digesting food. The gizzard, also known as the gizzard, is equivalent to the teeth of birds. It stores swallowed sand and gravel and is mainly used to grind food.

big heart

Fast heart rate

high arterial blood pressure

Urinary system: mainly includes the kidneys, ureters and cloaca. Since most birds do not have a bladder, they only have the function of storing urine in the cloaca. When they excrete feces, they excrete the urine together. The white part of bird feces is uric acid.

Reproductive system: consists of gonads, reproductive ducts and accessory glands. The gonads are very developed during the breeding period but underdeveloped during the non-breeding period.

brain

senses

feathers, wishbone

The forelimbs are specialized into "wings"

open pelvis

4 toes on hind limbs (3 in front and 1 in back)

Alveolar teeth

tail vertebrae separation

3 separate metacarpal bones of forelimb

sternum without keel

Resource overutilization

Habitat loss and fragmentation

environmental pollution

In situ conservation (replenished)

Off-site protection

Suitable habitat that was once distributed but is now extinct (reintroduction)

lack of glands

Horny scales, leathery skin (prevents water loss)

Dermal bone plate

Perfect water retention mechanism

Molting with regular replacement of scales

limb bones

skull

Spine (further differentiation)

The thorax appears: It is surrounded by thoracic vertebrae, ribs, and sternum. In addition to protecting internal organs, it also enhances the mechanical equipment for lung respiration, which echoes the development of lungs in terrestrial vertebrates.

Intercostal muscles: The movement of the intercostal muscles (including the external intercostal muscles and the internal intercostal muscles) pulls the ribs to change the volume of the thorax to complete the breathing action.

Cutaneous muscle: Cutaneous muscle is connected to the horny scales, and its contraction can pull the scales to assist crawling. It is especially developed in snakes.

The appearance of the secondary palate separates the digestive tract and respiratory tract, so that the animal does not hinder breathing when feeding.

The oral cavity has a wide range of teeth, but there is no chewing and food is swallowed whole.

Teeth (same type of teeth)

The oral cavity and pharynx are obviously differentiated, and the esophagus is extended.

A cecum appears in the digestive tract.

The cloacal pore is the exit from the digestive tract to the outside of the body.

adult lung respiration

Well-developed trachea and bronchi

Lungs are spongy

The thorax assists in breathing movements

heart

Arteries and veins: The conus arteriosus disappears. Sinus degeneration.

kidney

The excretory product is uric acid.

Extrarenal excretion

Except for primitive species, males have external genitalia

Amniotic egg: fibrous dura mater, calcareous hard shell

oviparous or ovoviviparous

Brain: Neocortex

Diencephalon: Parietal organ, pineal gland, and pituitary gland are developed

Midbrain: optic lobes

Cerebellum: developed

12 pairs of cranial nerves

Eye: Move the lens and change the curvature of the lens

Top eye: sensitive to light, improves body temperature

vomeronasal organ, vomeronasal organ in lizards and snakes

Cheek and lip pits: heat-sensitive receptors

skin pressure receptors

Ear: The tympanic membrane is inverted, forming the external auditory canal

Granular scales on body surface

The square bone cannot move

transverse cloacal orifice

The oldest group of existing reptiles, there is only one genus and one species left, namely the tuatara (wedge-toothed lizard). Bitemporal fossa type. Still retains a series of the most primitive characteristics, such as having a parietal eye located in the middle of the skull. It lives on more than 30 small islands in New Zealand and has a lifespan of 300 years.

No temporal foramen

Keratinous scales or leathery skin

Dorsal and ventral bony plates

The square bone cannot move

Cloacal orifice longitudinal fissure (the excretory orifice has a longitudinal slit)

Turtle, hawksbill turtle, red-eared slider, sea turtle

horny scales

Square bone activity

Terminal or lateral teeth

bitemporal foramen

transverse cloacal orifice

lizards and snakes

bitemporal foramen

The left and right ventricles are completely separated

The square bone cannot move

cloacal foramen longitudinal fissure

The neck is short and the shoulder girdle is placed behind the skull.

The spinal division is not obvious

Labyrinth teeth (patterns on the enamel)

Single occipital condyle

2 sacral vertebrae

Belt and limb bones are thick

Five fingers of forelimb

Degradation of habitat quality

habitat fragmentation

Overuse

pollution and climate change

Epidermis: multiple layers, the innermost layer is the germinal layer

Skin glands, mucous glands (developed), venom glands (the most concentrated place of venom glands: post-auricular glands), Chinese medicine toad venom: secretion of toad venom glands.

Dermis: thickened, nerves and blood vessels

axial bone

appendicular bones

Hyoid and mandibular bone becomes otic bone

Shoulder girdle detaches from skull

The belt is connected to the spine

Limbs with digits (toes)

Trunk muscles: Specialization less obvious in aquatic species. The original segmentation phenomenon of terrestrial species has been destroyed and changed into longitudinal or oblique long muscle groups that control the movement of the skull and spine. The ventral muscles are mostly flaky and layered, and the muscle fibers of each layer have different directions.

Muscles of the limbs: The muscles of the limbs are distributed around the girdle bones and limb bones, so the movement function is greatly complicated.

Branchial muscles: degenerated. The remaining part is involved in controlling swallowing, tongue and larynx movements.

digestive tract

Digestive glands: liver, pancreas, salivary glands (amphibians began to appear to overcome the dryness of land and difficulty in swallowing. The secreted fluid has no digestive enzymes and no digestive function, and only helps to moisten food).

respiratory organs

Breathing method: Swallowing breathing

heart, blood vessel structure

Circulation pathway: incomplete double circulation.

Lymphatic system: lymphatic vessels, lymphatic cavity, lymphatic heart, lymph fluid, spleen, etc. It is an auxiliary structure of the vascular system.

Excretory organs: kidneys, skin, lungs, etc. The kidneys are the most important. Like fish, the adult kidney is mesonephros and the embryonic kidney is pronephros. Located on either side of the spine just behind the center of the body cavity.

ureter

bladder

Excretion: urea (same as breastfeeding)

Regulation of osmotic pressure

reproductive organs

Reproductive mode

Brain: Nerve cells appear on the surface - protoencephalon

Diencephalon: top with pineal gland

Midbrain: left and right optic lobes separate

Cerebellum: Underdeveloped (simple movement patterns)

Measuring line: Larvae and aquatic species have lateral lines, whose function and position are the same as those of fish.

Nose: External and internal nares appear. The nasal mucosa covers the inner surface of the nasal cavity, and the olfactory nerves are distributed on the membrane. Therefore, the nose is the respiratory passage and the sense of smell.

Eyes: The adjustment ability of the frog's eyes is limited. It is myopic on land. When immersed in water, the cornea becomes flat and can see farther.

Ear

Degeneration of appendages

scaly

biconcave vertebral body

No eardrum (vibration produces hearing)

With limbs and tail

naked body

Biconcave or retroconcave vertebral bodies

water life

Giant salamander, giant salamander

Tailless in adults

Anterior or posterior vertebral body concavity

caudal bone

with tympanic membrane and tympanum

Abnormality

With operculum

lateral line

caudal fin ray

internal nares

tympanum

Terrestrial vertebrate appendages

seven toes

Habitat degradation or loss

capture

pollute

Natural disasters and climate change

species intrinsic factors

interspecific effects

Epidermis: ectoderm, secretes mucus, single-cell glands (drag reduction/insect protection)

Dermis: mesoderm

Scales are located below the epidermis and above the dermis

Scales: The dermis forms the inner layer and the marrow, cartilaginous fish scales. (The scales are homologous to human teeth)

Bone scales (hard scales, round scales, comb scales): completely formed by dermal secretions, bony fish scales.

Cartilage (special connective tissue): composed of cells and intercellular matrix.

hard bones

axial skeleton

appendicular skeleton

mouth

Pharynx: gill rakers, pharyngeal teeth

Digestive canal: The digestive tract is a long and slender membranous tube. According to different functions and structures, it is divided into the oral cavity, pharynx, esophagus, stomach, small intestine and large intestine. There are spiral valves in the digestive tract of cartilaginous fish.

Digestive glands: Digestive glands are structures differentiated from epithelial tissue and come in two types: large and small. Small digestive glands are buried in the wall of the digestive tract, such as esophageal glands, gastric glands, and intestinal glands. Large digestive glands such as liver and pancreas.

Gills: Fish gills have two large gill covers, and the cavity inside the gill cover is called the gill cavity. When you lift the gill cover, you can see that there are four gills on each side of the throat. Each gill is divided into two rows of gill lamellae. Each row of gill lamellae is composed of many gill filaments, and many small gills grow on both sides of each gill filament. Small piece. There are capillaries in the gill lamellae. The epidermis here is very thin. When blood flows through it, gas exchange is completed.

Gill septum: The gill septum of cartilaginous fish reaches the skin and the gills are attached to it; the gill septum of bony fish is underdeveloped.

Water flows in the gills: the alternate opening and closing of the mouth and gill cover allows water to continuously enter the oral cavity from the mouth, reach the gill cavity through the pharynx, contact the gill filaments, and then be discharged to the outside through the gill pores.

Countercurrent exchange of oxygen: When water enters the fish's mouth, it passes through the gills and out from there. In this process, the direction of water flow is exactly opposite to the direction of blood flow in the gill plates, forming a countercurrent exchange system. This system can efficiently bring in oxygen and take away oxygen. The existence of this countercurrent exchange system allows fish to breathe efficiently in the water.

Cartilage fish have 4-7 pairs of gill slits, which open directly on the body surface.

swim bladder

Heart: The heart is an organ composed of muscles that beat on its own.

Blood vessel

Whole kidney (protokidney): Cyclostome hagfish, a few bony fishes

Embryos: anterior and mesonephros

Adult: posterior kidney

A few teleost adults still use pronephros for urination

bony fish reproductive organs

cartilaginous fish reproductive organs

Brain: olfactory center.

Diencephalon: thalamus, hypothalamus. There is the pineal gland at the top and the pituitary gland and vascular sac at the bottom.

Midbrain: optic lobes, midbrain nuclei. The left and right optic lobes are not separated.

Cerebellum: cerebellum, pons. developed.

Brain oblongata: It is the sensory center of the auditory capsule and lateral line.

Cranial nerves: 10 pairs

Lateral line organs: neuromasts, hair cells. Feel the current to locate predators or mates.

Lorenzini organ: detects prey and emits a weak electric field.

Weber's organ (Cyprinidae fish): also known as Weber's ossicles, anterior → posterior: band bone, transverse bone, intercalated bone and triangular bone. They are connected by membranes and ligaments, and the band-shaped bone and the ship-shaped bone are in contact with the perilymphatic cavity of the inner ear and communicate with the endolymphatic sinus. The rear tip of the tripod bone is buried in the connective tissue of the anterior chamber of the swim bladder, thus establishing the connection between the swim bladder and the inner ear. connections between. When external sound is transmitted to the fish body, the swim bladder can enhance the amplitude of the sound wave. Through Weber's organ, carps can feel high-frequency, low-intensity sounds.

Inner ear: semicircular canals, utricle, saccule, flask, otoliths. Mainly a balance organ. The flask-shaped sac in bony fishes develops into the cochlear duct in mammals.

Chondrichthyans

teleost fish

Placoderms: the ancestral group of cartilaginous fishes

Sticklebacks: ancestral group of bony fishes

Initial whole jaw fish

1 semicircular canal

1-16 external gill openings

multiple internal parasites

2 pairs of semicircular canals

7 external gill openings

ectoparasitism

Urochordates

Cephalochordates

Main features

Classification