The Animal Kingdom

Chordates

Phylum Chordata

ChordatesPossess all the characteristics of animals farther down on the evolutionary ladder: nucleus, multi-cellular, heterotrophic.Possess tissues, bilateral symmetry, a coelom, and a deuterostome.

The Animal Kingdom

Review branch points in animal evolution.1st = presence of tissues2nd = symmetry3rd = type of body cavity – a coelom

Acoelomate: Sponges, Cnidarians, Flatworm.sCoelomate: Nematodes, Annelids,

Mollusks, Arthropods, Echinoderms

4th = embryonic developmentProtostomes (blastopore becomes stomach): Mollusks & Arthropods.Deuterostomes (blastopore be- comes anus): Echinoderms,

Chordates

Phylum Chordata

Chordata includes 3 subphyla:the urochordates, cephalochordates, & vertebrates.

All share 4 anatomical structures at some point in life.

A notochord (in all embryos): a rod between the digestive tube and the nerve cord; provides skeletal support (in humans – it becomes the gelatinous material between vertebral disks.A dorsal nerve cord; it develops into the brain and spinal cordPharyngeal gill slits connect the pharynx to the outside. Slits allow water that enters the mouth to exit without continuing through the entire digestive tract. Slits have become modified for gas exchange (in aquatic vertebrates), jaw support, hearing, etc.Most chordates have a post-anal tail. In contrast, nonchordates have a digestive tract that extends nearly the whole length of the body.

Phylum Chordata

Chordata includes 3 subphyla:the urochordates, cephalochordates, & vertebrates.

All share 4 anatomical structures at some point in life.

A notochordA dorsal nerve cordPharyngeal gill slitsA post-anal tail

Phylum Chordata

Chordata includes 3 subphyla:Urochordates (called tunicates) adhere to rocks, docks, and boats.; they are suspension-feeders. Larvae have all four chordate characteristics, but adults possess only the gill slits.

Adult Larva

Phylum Chordata

Chordata includes 3 subphyla:Cephalochordates (called lancelets) have all four chordate characteristics

persisting through adulthood.

Lancets are just a few cm. They live with their posterior end buried. Also suspension feeders. Molecular evidence suggests that the vertebrates' closest relatives are the cephalochordates.

Phylum Chordata

Chordata includes 3 subphyla:Vertebrates possess an endoskeleton with a backbone, and a closed circulatory system, with a chambered heart for an active lifestyle that requires a large supply of fuel.

An endoskeleton can grow indefinitely, unlike an exo-

skeleton that must be re-placed from time to time.

Examples: fish, amphibians, reptiles, birds, mammals.

Vertebrates

An overview of vertebrate diversity.At the base are hagfishes and lampreys which lack hinged jaws.All others (gnathostomes) have true jaws & paired appendages.

In fishes, these paired appendages function in swimming.In tetrapods, the appen- dages become legs.

Amphibians lay eggs in water or a moist environment.Others are amniotes; pro- ducing shelled, water-retain- ing eggs allows them to com- plete their life cycles on land.

Ex: reptiles and birds. In mammals, offspring develop internally.

Vertebrates

Vertebrates evolved in the sea 530 mya. First ones had no jaws. Hagfish are the most primitive vertebrates around today. They are scavengers that feed on worms and dead fish. Skeleton of cartilage.Lampreys are parasites that use hook-like teeth, a rasping tongue, & a sucking mouth to scape skin from fish and drink its blood.

Hagfish

Vertebrates

Vertebrate jaws evolved from skeletal supports of pharyngeal slits. The remaining gill slits remained for respiration.

A common ancestor gave rise to sharks and bony fishes 425 to 450 million years ago.

Class Chondrichthyes

Cartilage fishesEx: sharks & rays – 850 species.

Endoskeleton of cartilage Paired fins: pectoral at front,

pelvic at back, dorsal on top, caudal at end (most fish).

Series of gill slits on side of body.

Class Chondrichthyes

Cartilage fishesEx: sharks & rays – 850 species.

Rough skin due to tooth-like scales in skin →

Rows of teeth in jaws replaced from behind as the old ones are lost.

No swim bladder, so they sink to bottom if not swimming.

Senses: good sense of smell, can sense electric currents in water,

pressure-sensitive cells on side of body (the lateral line) detects pres- sure as fish swim by, vision not too significant.Internal fertilization - pelvic fins adapted for clasping

Class Osteichthyes

Bony fishesEx: tuna, salmon – 21,000 species

Endoskeleton of bone.Scales usually made of

bone as well.Gills housed in one cham-

ber on each side of head covered by a bony plate

called the operculum.

Class Osteichthyes

Bony fishesEx: tuna, salmon – 21,000 species

Have a swim bladder, so they can maintain any

depth in water while standing still.

Senses: color vision is important, many sense

electric currents in the water, also have the lateral

line.Most fertilize eggs outside the body: external fertilization - guppies, mollies, swordtails are exceptions.

Class Osteichthyes

Bony fishesRay-finned - fan-shaped fins

supported by bony rays - majority of fish.

Ex. trout, marlin, grouper

Class Osteichthyes

Bony fishesLobe-finned - fleshy fins supported by bones.

Ex: coelocanth (deep ocean)Ex: & lungfish (functional lungs - live in stagnant area or places that dry up - must move or burrow into river bottom - the ancestor of amphibians from DNA comparison).

Lungfish

Class Amphibia

Amphibians - Greek: Amphi + bio = “double life”

referring to life stages in water (for reproduction) & on land

Evolved 350 mya during the early Carboniferous

Period from lungfish.

Class Amphibia

Amphibians - Greek: Amphi + bio = “double life”

referring to life stages in water (for reproduction) & on land.

Most have legs at right angle to body (not underneath).Gills as larvae & lungs as adults.

Gas exchange thru skin as well.External fertilization in water; eggs not water-tight.All carnivorous as adults; larvae usually herbivorous.

Class Amphibia

Caecilians Burrowing animals

with tail but nolegs, eat earth-

worms & small animals.

Class Amphibia

Salamanders & newtsDistinct head, trunk,

& tail with legs.

Class Amphibia

Frogs & toads No tail as adult; hind

limbs for jumping

Class Amphibia

Frogs & toads Anatomy of the grassfrog

Class Amphibia

Frogs & toads: evolution of the vertebrate heart

A fish heart has two chambers: a ventricle & an atrium

The ventricle pumps blood to the gills for O2.

Amphibians have 3 chambers: 2 atria & 1 ventricle.

The ventricle pumps blood into a forked artery that sends it to the skin & lungs or to the rest of the body.

The open ventricle mixes O2-rich and O2-poor blood: not efficient.

Fish Frog