mammals, reptiles, amphibians, and fishes are all classified as...
unique characteristics of vertebrates
the cranium (skull), the backbone, series of bones called vertebrae
all share four key features that appear in the emrbyo and sometimes in the adult.
four key features in chordata
1) a dorsal, hollow nerve chord 2) a notochord--which is a flexible, longitudinal rod located between the digestive tract and the nerve chord 3)pharyngeal slits--gill structures in the pharynx, the region of the digestive tube just behind the mouth 4) a post-anul tail--which is a tail to the rear of the anus
the pylum Chordata is divided into three subphyla
lancelets and tunicates (invertebrate chordates), and vertebrates (retains the basic chordate characteristics but has additional unique features)
the first vertebrates were
aquatic and probably evolved during the eary cambrian period about 542 million years ago. they lack jaws
jawless vertebrates fish. some are parasites that are suckers
first jawed vertebrates
fishes that evolved by about 444 million years ago. they also had two pairs of fins
two major types of living fishes
chondrichthyans (the sharks and rays) and the osteichthyans (bony fishes)
have a flexible skeleton made of cartilage. adept pradators, fast swimmers with streamlike bodies, special electrosensors on the head can detect muscle contractions of nearby animals. also have a lateral line system
lateral line system
a row of sensory organs running along each side of the body. sensitive to change in water pressure, enables them to detect minor vibrations
have skeletons that are reinforced by calcium. they have a lateral line system, keen sense of smell, and excellent eye sight. on each side of the head, a protective flap called the operculum covers the chamber housing gills. have a swim bladder
an organ that helps keep them buoyant, a gas filled sac. can conserve energy by remaining almost motionless, in contrast to sharks
largest group of vertebrates
ray finned fishes
bony fishes, including trout, bass, perch, and tuna. their fins are supported by thin, flexible skeletal rays
lobe finned fish
muscular fins supported by stout bones
exhibit a mixture of aquatic and terrestrial adaptations. tied to water because their eggs dry quickly in the air. account foronly about 8% of all living vertebrates
amphibians live a double life because...
amphibians were the first species to...
"four feet". terrestrial vertebrates, amphibians, reptiles, and mammals.
reptiles (including birds) are these. adaptations for living on land.
amniotes adaptation for living on land
amniotic egg--> a fluid filled egg enclosed in a shell inside of which the embryo develops. functions as a "self contained pond" that enables amniotes to complete their life cycle on land.
include snakes, lizards, turtles, crocs, alligators, and birds, along with extinct groups.
reptiles adaptations to live on land
scales-->which contain a protein called Keratin which helps to prevent dehydration in dry air. they cann'ot breathe therough their dry skin and so obtain most of their oxygen with their lungs
nonbird reptiles are sometimes referred to as
cold blooded because they do not use their matabolism extensively to control body temperature
lizards are ectotherms
by heating directly with solar energy rather than through the matabolic breakdown of food, a lizard can survive on less than 10% of the calories required by a mammal of equivalent size
during the last period of the mesozoiz era
global climate became cooler and more variable, this was a period of mass extinctions that clamimed all the dinos by about 65 million years ago
the lone surviving lineage of the dinos is by
a reptilian group known as birds
evolved from a lineage of small two legged dinos during the great reptilian radiation of the mesozoic era
almost every element of bird anatomy is modified is some way that enhances flight.
bones have a honeycombed structure that makes them strong but light. absence of certain internal organs, only one ovary, toothless (grind food in the gizzard)
birds are endotherms
meaning they use thier own metabolic heat to maintain a warm, contstant body temperature
the flight muscles are the...in turkeys or chickens
feathers are made of...are are used for...
keratin...insulation and now flight gear
two major lineages of amniotes
one led to the reptiles and one led to mammals
about 200 million years ago and were probably small, nocturnal insect eaters
mammals became more diverse when
fall of the dinos
most mammals are
terrestrial, however some are winged, some aquatic
two mammalian hallmarks
hair and mammary glands that produce milk to nourish the young
mammals, like birds, are
three major groups of mammals
monotremes, marsupials, eutherians
egg laying mammals, duck billed platapus and the echidna are the only exhisiting
during gestation in marsupials and eutherians, the embryos are nurtured inside the mother by this organ consisting of both embryonic and maternal tissues, which joinds the embryo to the mother within the uterus. the embryo is nurtured by maternal blood that flows close to the embryonic blood system in this.
pouched mammals, kangaroos, koalas, and opposums. brief gestation and give birth to tiny embryonic offspring that complete development while attached to the mother's nipples
placental mammals because their placentas provide a more intimate and longer lasting association between the mothjer and her developing young than do marsupial placentas. make up almost 95 % of the living mammals (dogs, cats, cows, rabbits, etc)