Vertebrates

Vertebrates All vertebrates belong to the phylum chordata They are often called chordates All vertebrates have a back bone (vertebra)

Characteristics of Chordates All chordate embryo’s have a notochord The notochord is a flexible rod that extends through much of the length of the body In vertebrates the only remnant of the notochord is found in the cartilagenous discs of the backbone

Characteristics of Chordates In addition to the notochord all chordate embryos share three other features All have a dorsal hollow nerve cord that will eventually develop into the brain and spine All have pharyngeal slits these develop into the organs of respiration, hearing or the mouth in various species All chordates have a tail that extends beyond the anus

Invertebrate Chordates In two species (Tunicates and Lancets) the larval stage has all the characteristics of a chordate, however they are invertebrates in the adult stage

Tunicate Lancet

General Characteristics of Vertebrates In addition to the skull and backbone All vertebrates have an endoskeleton that may be composed of bone and cartilage (humans) or entirely of cartilage (sharks) All vertebrates have a hinged jaw. In mammals in unhinges in an up and down fashion. In reptiles (snakes) it unhinges up and down as well as left to right

Classes of Vertebrates Fish Amphibians Reptiles Birds Mammals

Classes of Vertebrates Fish Fish are divided into two groups - Cartilagenous fish (Chondrichthyes) so named because they have a flexible skeleton composed entirely of cartilage - These include the sharks and rays

Classes of Vertebrates Fish Fish are divided into two groups - Cartilagenous fish (Chondrichthyes) so named because they have a flexible skeleton composed entirely of cartilag - These include the sharks and rays - Bony fish (Osteichthyes) so named because they contain a true skeleton composed of hardened calcium components – This includes all other fish

Fish Adaptations Lateral Line System – is a series of sensory organs running along each side of the body that allows the shark to detect minute changes in water pressure indicating the presence of animals swimming by Swim bladder (bony fish) is a gas filled sac that enables a fish to control it density and therefore its depth in the water. Bony fish can remain motionless in water without sinking, sharks cannot All fish have a two-chambered heart

Classes of Vertebrates Amphibians Amphibians include the frogs and salamanders Amphibians are tetrapods – organisms with four limbs

Classes of Vertebrates - Amphibians Characteristics - Live part of their lifecycle in the water and part on land - The larval stage is generally spent in the water and the adult form on land - Larval amphibians have gills adults have lungs - The eggs of amphibians do not have shells and will dry out if left on land

Classes of Vertebrates - Amphibians All amphibians have a three-chambered heart (two atria and one ventricle) there is mixing of oxygenated and deoxygenated blood. This is why amphibians cannot maintain there body temperature and are called cold-blooded (ectotherms)

Classes of Vertebrates - Reptiles Reptiles were the first amniotes Amniotes (Reptiles, birds and Mammals) have an amniotic egg, internal fertilization and water tight skin Reptiles include snakes, turtles, tortoises, lizards, alligators and crocodiles

Classes of Vertebrates - Reptiles Amniotic egg – The amniotic egg means that it is water proof and has a shell. One membrane the amnion develops from the embryo. The amnion protects the embryo from drying out. Other membranes allow for gas exchange and cushioning. The amniotic eggs makes it possible for an embryo to develop on land. It was a tremendous evolutionary leap from amphibians

Classes of Vertebrates - Reptiles Internal fertilization – During internal fertilization the male deposits sperm into the female that swim toward the fallopian tubes for fertilization. External fertilization which can occur in water would be impossible on land

Classes of Vertebrates - Reptiles Water-tight skin – Amniotes have a water tight skin enriched with a waterproofing material called keratin. This “keratiniztion” prevents dehydration. Keratin is found in the scales of reptiles, the feathers of birds, and in the hair, nails and horns of mammals

Classes of Vertebrates - Reptiles There are about 6,500 classes of reptiles Reptiles began to evolve about 300 million years ago, however the true age of reptile and an explosion in diversity occurred about 55 million years ago.

Saltwater Crocodile American Alligator

Classes of Vertebrates – Aves (Birds) Molecular and fossil evidence indicates that dinosaurs, crocodiles and birds are very closely related

Classes of Vertebrates – Aves (Birds) Birds are endothermic amniotes with special adaptations for flight These adaptations include: Wing shape that provides lift for flight, feathers for flight and endothermy, and weight reducing features in the bone and among their internal organs (such as having only one ovary and not having teeth)

Classes of Vertebrates – Aves (Birds) Like mammals, birds have a very efficient four chambered heart with a two-loop circulation

Classes of Vertebrates – Aves (Birds) Gizzard- The gizzard is a muscular organ often containing small stones that are used for grinding seeds. Both crocodiles and alligators have a gizzard. Fossil evidence shows that some dinosaurs also had a gizzard Crop – The crop is a temporary storage site for food before it continues onto the stomach

Classes of Vertebrates – Aves (Birds) Cloaca – Like amphibians and reptiles, birds have a cloaca, the common opening for urine, feces, sperm and eggs

The Bernoulli Principle and flight

Classes of Vertebrates – Mammalia (Mammals) Mammals are endothermic animals that have body hair, produce live young (with three exceptions), have modified sweat glands that produce milk, nurse their young, have seven cervical vertebrae, have a solid lower jaw bone, have three bones in the ear (hammer, anvil, stirrup), have a diaphragm, and have one primary artery (the aorta) leaving the heart and bending to the left

Diversity Among Mammals All mammals are divided into three groups Monotremes – These are the egg laying mammals they are represented by the platypus and the echidnas. Monotremes have sloped shoulders like reptiles and a cloaca. However, they have hair, produce milk and nurse their young and are therefore classified as mammals DNA evidence shows that monotremes are very primitive and closely related to reptiles

Platypus Short-beaked Echidna Long-beaked Echidna

Diversity Among Mammals Marsupials – Marsupials also known as pouched mammals. The embryo’s of marsupials are born before they are fully mature, with 12-16 days in most species. The embryo’s finish their development in an external pouch

Diversity Among Mammals Placental Mammals – In placental or eutherian mammals the embryo completes its development while protected within the mother’s uterus. Inside the uterus an organ called the placenta provides the embryo with nutrition and oxygen and removes waste The embryo is bathed in fluid called the amniotic fluid (this is what leaks when a woman’s “water” breaks

Diversity Among Mammals From our perspective the most important group of mammals are the primates The primates include the new and old World monkeys as well as the apes The apes include gibbons, orangutans, chimpanzees, gorillas and man Humans and chimpanzees share 97% of the same DNA That 3% makes all the difference!

The “Great Ape” Family