lecture 18: 8- phylum: chordata

The phylum of Chordata includes four subphyla: 1- Subphylum: Vertebrataالفقاريات 2- Subphylum: Urochordataالذيل حبليات 3- Subphylum: Cephalochordataالرأس حبليات 4- Subphylum: Hemichordata النصف حبلياتAll vertebrates have backbones العمود الفقريHumans, mammals, birds, lizards, snakes, turtles,

amphibians, fishes are vertebrates.They share several unique features including a

backbone.

Lecture 18: 8- Phylum: Chordata

All animals are grouped as either an invertebrate or a vertebrate.95% of all animals are invertebrate organisms.

The animals do not have a backbone or vertebral column.5% of all animals are vertebrates.

These animals do have a backbone.

The subphylum of vertebrata includes seven classes:

1- Class: Cyclostomata)دائرية الفم )الالفكيات 2- Class: Chondrichthyesاألسماك الغضروفية 3- Class: Osteichthyesاألسماك العظمية 4- Class: Amphibia البرمائيات5- Class: Reptilia الزواحف6- Class: Aves الطيور7- Class: Mammalia الثدييات

Section 33-1Diversity of Chordates:

Why are fishes so successful?Adapt to environment.Extract oxygen from small amounts of oxygen per unit volume.Efficient locomotor structures. High sensory system.Efficient reproduction (produces overwhelming number of

offspring).

Most are predators (always searching for food):Swallow prey whole.Capture prey: suction-closing the opercula and rapidly

opening mouth.Some filter feeders- Gill rakers: trap plankton while the

fish is swimming with mouth open.Some herbivores and omnivores.

Nutrition and Digestion:

Oviparous: Lay undeveloped eggs, External fertilization (90% of bony fish), Internal fertilization (some sharks and rays) Fish lay huge numbers of eggs; a female cod may release 4-6

million eggs.Ovoviviparous: Internal development- without direct

maternal nourishment-Advanced at birth (most sharks + rays).Viviparous: Internal development- direct nourishment from

mother-Fully advanced at birth (some sharks)

Reproduction and Development:

Phylum: Chordataالحبليات Subphylum : Vertebrataالفقاريات Class: Amphibiaالبرمائيات Frog (amphibian)الضفدعة Amphibian means “two lives,” a reference to the metamorphosis of many frogs from an aquatic stage, the tadpole, to the terrestrial adult.

Tadpoles are usually aquatic herbivores with gillsخياشيم , a lateral line system, and swim by tail.

During metamorphosisالتحول , the tadpole develops legs, and gills are replaced by lungs.

Adult frogs are carnivorous hunters.Most amphibians retain close

ties with water and are most abundant in damp habitats.

External Structures:Mucous-covered skin: protection from

microorganisms, UV, desiccation, and mechanical injury.

Allows for: Gas exchange, temperature regulation, and absorption/storage of water.

Amphibians’ skin keeps them moist, aids in mating, can produce toxins, even change color.

All this without scales, feather or hair.Skin has lots of glands.

Nutrition and digestion:Adults:

Mostly carnivores feeding on invertebrates.Hunt by sight, wait for prey to pass by

Salamanders and caecilians use olfactory senses to help catch prey.

Larvae:Mostly herbivores

Vocalization:Usually used for mating.Attract females.Mark territory.Calls are species specific.Can give a distress call.Hopefully enough to scare a predator.Helps ensure a mate of the proper species is found.

Metamorphosis:Series of abrupt structural,

physiological, and behavioral changes.

Anurans have the most dramatic metamorphism:Limbs and lungs developGill are lostTail is reabsorbedSkin thickensHead and digestive tract change to allow

them to digest prey.