CHAPTER 35 Flashcards by ryan Hamrick

Phylum Chordata

Chordates are deuterostome coelomates
Nearest relatives are echinoderms (the only other deuterostomes)
Fishes, amphibians, reptiles, birds, and mammals

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4 Features

Dorsal, hollow nerve cord
Notochord
May be replaced by vertebral column
Pharyngeal slits
Pharyngeal pouches present in all vertebrate embryos
Postanal tail

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All chordates have all four of these characteristics at some time in their lives
Other characteristics also distinguish chordates
Chordate muscles are arranged in segmented blocks called somites
Most chordates have an internal skeleton against which the muscles work

Phylum Chordata can be divided into three subphyla

Urochordata
Cephalochordata
Vertebrata

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Subphylum Urochordata

Tunicates and salps are marine animals
Larvae are tadpolelike and have notochord and nerve cord
Are free-swimming but do not feed
Adults typically lose the tail and notochord
Are immobile filter-feeders
Many secrete a tunic (cellulose sac) that surrounds the animal

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Subphylum Cephalochordata

Lancelets are scaleless chordates
Notochord persists throughout animal’s life
Spend most of their time partly buried
Have no distinguishable head
Feed on plankton using cilia-generated currents
Closest relatives to vertebrates

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Subphylum Vertebrata

Vertebrates are chordates with a VERTEBRAL column
Distinguished from nonvertebrates by
Vertebral column—bony or cartilagenous – Encloses and protects the dorsal nerve cord
Head – Distinct and well-differentiated possessing sensory organs

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Vertebrates also have
Neural crest – unique group of embryonic cells that forms many vertebrate structures
Internal organs – liver, kidneys, endocrine glands, heart, and closed circulatory system
Endoskeleton – made of cartilage or bone—living tissue that is strong but not brittle
Makes possible great size and extraordinary movement

The first vertebrates appeared in the oceans about 545 MYA
Mouth at one end, fin at the other
Jawed fishes soon became dominant
Amphibians invaded the land
Reptiles replaced them as the dominant land vertebrates
Birds and mammals became dominant after Cretaceous mass extinction

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Fishes

Most diverse vertebrate group
Over half of all vertebrates
Provided the evolutionary base for invasion of land by amphibians

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Fishes have the following characteristics
Vertebral column
Hagfish exception and lamprey rudamentary vertebrae of cartilage
Jaws and paired appendages
Hagfish and lamprey exceptions
Internal gills
Single-loop blood circulation
Nutritional deficiencies
Inability has been inherited by all their vertebrate descendants—cannot synthesize certain amino acids—must get them in their food.

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History of the Fishes

The first fishes had mouths with no jaws
Agnatha extant as hagfish (class Myxini) and lampreys (class Cephalaspidomorphi)
Ostracoderms (jawless) are now extinct—first vertebrates
The development of jaws occurred in the late Silurian period
Jaws evolved from the anterior gill arches that were made of cartilage

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Armored fishes (placoderms) and some spiny fishes (Acanthodians) both had jaws
Spiny fish were common during early Devonian – replacing ostracoderms
Cartilage skeleton but skin had small plates of bone
Extinct at close of Permian
Placoderms became common in late Devonian
Jaw more improved than spiny fishes’
Upper jaw fused to the skull and the skull hinged on the shoulder
Extinct by end of period

At the end of the Devonian period, essentially all of these pioneer vertebrates disappeared, replaced by sharks and bony fishes in one of several mass extinctions
Sharks and bony fishes first evolved in the early Devonian, 400 MYA
Jaw was improved even further allowing the mouth to open much wider than was previously possible

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Class Chondrichthyes

Sharks, skates, rays
Became the dominant sea predators in the Carboniferous period (360–280 MYA)
Cartilage skeleton “calcified” with granules of calcium carbonate
Light, strong skeleton
No swim bladder

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Sharks were among the first vertebrates to develop teeth
Evolved from rough scales on mouth’s skin
Not set into the jaw so easily lost but continuously replaced
Sharks (and bony fishes) have a fully developed lateral line system
Series of sensory organs under the skin that detects changes in pressure waves

Reproduction in sharks differs from that of other fishes
Eggs are fertilized internally
Most pups are born alive
A few species do lay fertilized eggs
Sharks have long gestation periods and relatively few offspring
Therefore, are not able to recover quickly from population declines

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Bony fishes

Evolved at the same time as sharks about 400 MYA
However, they adopted a heavy internal skeleton made completely of bone
Bony fishes are the most species-rich group of all vertebrates (> 30,000 living species)
Significant adaptations include swim bladder and gill cover

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Swim bladder
Gas-filled sac that allows bony fishes to regulate their buoyant density
In most modern fish, filled and drained with gases internally
Gill cover
Hard plate, the operculum, covers gills
Flexing plate permits water pumping over gills
Efficient bellows system when stationary

Gases are taken from the blood, and the gas gland secretes the gases into the swim bladder; gas is released from the bladder by a muscular valve, the oval body

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Two Major Groups of Bony Fishes

Ray-finned fishes (class Actinopterygii)
Parallel bony rays support and stiffen each fin
There are no muscles within the fins
Lobe-finned fishes (class Sarcopterygii)
Have paired fins that consist of a long fleshy muscular lobe
Supported by central core of bones with fully articulated joints—muscles can move fin rays
Almost certainly the amphibian ancesto

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Class Amphibia

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First vertebrates to walk on land but tied to water for reproduction
Direct descendants of fishes

5 distinguishing amphibian features
Legs – adaptation to life on land
Lungs
Cutaneous respiration – supplement lungs
Pulmonary veins – separate pulmonary circuit allows higher pressure blood to tissues lungshearttissue
Partially divided heart – improves separation of pulmonary and systemic circuits—atria have separation but not ventricles—3 chambered heart

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Amphibia means “double life”
Successful invasion of land by vertebrates required several adaptations
Legs to support body’s weight
Lungs to extract oxygen from air
Redesigned heart and circulatory system to drive larger muscles
Reproduction still in water to prevent egg drying
System to prevent whole body desiccation—skin glands, lungs deep in body
Amphibians evolved from lobe-finned fish
Ichthyostega was one of the first amphibians

3 Modern Amphibian groups

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5,670 species in 37 different families 
Order Anura (“without tail”)
Order Caudata (“visible tail”) 
Order Apoda (“without legs”)

Order Anura (frogs and toads)

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Frogs have smooth, moist skin and long legs
Most live in or near water, aquatic tadpole stage before metamorphosis into adult
Toads have bumpy, dry skin and short legs
Most live in dry environments
Not a monophyletic group—some toads are more closely related to frogs than they are other toads
Eggs laid in water – lack watertight membranes
Eggs fertilized externally
Tadpole – swimming larval form
Gradual metamorphosis into adult form

Order Caudata (salamanders)
Have long bodies, tails, and smooth, moist skin
Live in moist places
Eggs are fertilized internally – females pick up male’s sperm packet
Larvae similar to adults
Order Apoda (caecilians)
Tropical, burrowing amphibians
Legless with small eyes and jaws with teeth
Fertilization is internal

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JACK

Class Reptilia

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Over 7000 living species
All living reptiles exhibit three key features
Amniotic eggs, which are watertight; have yolk that is a food source
Dry skin and scales which cover body and prevents water loss
Thoracic breathing (moving rib cage), which increases lung capacity

Reptiles, birds, and mammals are amniotes
The amniotic egg has four membranes
Chorion
Outermost layer, allows gas exchange
Amnion
Encases embryo in fluid-filled cavity
Yolk sac
Provides food
Allantois 
Contains excreted wastes from embryo

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Reptiles dominated earth for 250 million years
Reptiles are distinguished by the number of holes on side of the skull behind eye orbit
0 (anapsids), 1 (synapsids), 2 (diapsids)

The synapsids rose to dominance first
Pelycosaurs
First land vertebrates to kill beasts their own size
Therapsids
Replaced them about 250 MYA
May have been endotherms
“Mammal-like reptile
Most became extinct 170 MYA
One group survived and has living descendants today – the mammals

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HEY

Modern reptiles developed two important characteristics Internal fertilization Sperm fertilizes egg before protective membranes are formed Improved circulation Oxygen is provided to the body more efficiently Septum in heart extended to create partial wall between the ventricles Crocodiles, birds, and mammals have completely divided 4-chambered heart

All living reptiles are ectothermic Obtain heat from external sources Regulate body temperature by moving in and out of sunlight Compare to endothermic animals that generate their own heat internally

There are four surviving orders of reptiles Chelonia (turtles and tortoises) Rhynchocephalia (tuataras) Squamata (lizards and snakes) Crocodylia (crocodiles and alligators) About 7000 species Reptiles occur worldwide except in the coldest regions, where it is impossible for ectotherms to survive

Order Chelonia__Differ from all other reptiles because their bodies are encased within a protective shell Carapace (dorsal) and plastron (ventral) Tortoises are terrestrial while turtles are mostly aquatic Both lack teeth but have sharp beaks Marine turtles must return to land to lay eggs

Order Rhynchocephalia___Contains only two species of tuataras Large, lizardlike animals about half a meter long Only found on islands near New Zealand Parietal eye Eye with lens and retina concealed under layer of scales on top of head

Order Squamata-----A characteristic of this order is the presence of paired copulatory organs in the male Snakes – 3000 species Lack limbs (but evolved from a lizard with limbs), movable eyelids, and external ears Lizards – 3800 species Many have ability to regenerate lost tails

Order Crocodylia_)__25 species of large, primarily aquatic carnivorous reptiles Crocodiles Typically nocturnal Tropical and subtropical regions Alligators – only 2 species Bodies well adapted to stealth hunting Eyes on top of head, nostrils on top of snout, enormous mouth, strong necks

JACK

Class Aves___Birds are the most diverse of all terrestrial vertebrates 28 orders, 166 families, about 8600 species Success lies in unique structure – feather

``` Birds still retain many reptilian traits Amniotic eggs and scales on legs Lack teeth and tails of reptiles Two major distinguishing traits Feathers Modified scales of keratin Provide lift for flight and conserve heat Flight skeleton Bones are thin and hollow Many are fused for rigidity – anchor strong flight muscles ```

Feathers developed from reptile scales Linked structures provide continuous surface and a sturdy but flexible shape Keel-shaped sternum

Archaeopteryx is the first known bird Had skull with teeth, long reptilian tail Feathers on wings and tail Forelimbs nearly identical to those of theropods (dinosaur) Feather probably evolved for insulation

Modern Birds

Adaptations for flight--physiology Efficient respiration Air passes all the way through lungs in a single direction via air sacs Efficient circulation 4-chambered heart so muscles receive fully oxygenated blood Rapid heartbeat Endothermy Body temperature (40–42oC) permits higher metabolic rate

Class Mammalia-------2 fundamentally mammalian traits Hair Long, keratin-rich filaments that extend from hair follicles Insulation, camouflage, sensory structure Mammary glands Females possess mammary glands that secrete milk

Other notable features of mammals Endothermy depends on higher metabolic rate 4-chambered heart Respiration using diaphragm Placenta in most mammals Specialized organ that brings fetal and maternal blood into close contact

The mammalian lineage also gave rise to several adaptations in some groups Specialized teeth Different types of teeth are highly specialized to match particular eating habits Contrast carnivore teeth to herbivore teeth

``` Digestion of plants Herbivorous mammals rely on mutualistic partnerships with bacteria for cellulose breakdown Development of hooves and horns Hooves are specialized keratin pads Horns are bone surrounded by keratin Antlers are made of bone, not keratin ```

Flying mammals: Bats Only mammals capable of powered flight Wing is a leathery membrane of skin and muscle stretched over 4 finger bones Navigate in the dark by echolocation

HEY

History of Mammals

Mammals have been around since the time of the dinosaurs, about 220 MYA Tiny, shrewlike, insect-eating, tree-dwelling creatures May have been nocturnal – large eye sockets Mammals reached their maximum diversity in the Tertiary period (65–2 MYA) After mass extinction of dinosaurs Decline in the total number of mammalian species over last 15 million years

2 Subclasses of Mammals

``` Prototheria (most primitive) Lay shelled eggs Only living group is the monotremes Theria Viviparous – young are born alive Two living groups Marsupials or pouched mammals Placental mammals ```

Evolution of Primates

Primates are the mammals that gave rise to our own species Evolved two features that allowed them to succeed in an arboreal environment Grasping fingers and toes First digit (thumb) is opposable in many Binocular vision Eyes are shifted toward the front of the face Lets brain judge distances precisely

``` About 40 MYA, the earliest primates split into two groups Prosimians Only a few survive today Lemurs, lorises and tarsiers Large eyes with increased visual acuity Most are nocturnal Anthropoids ```

Anthropoids Include monkeys, apes, and humans Almost all diurnal Changes in eye design include color vision Expanded brain Live in groups with complex social interactions Care for young for extended period Long period of learning and brain development

30 MYA New World monkeys migrated to South America All arboreal; many have prehensile tail Old World monkeys and hominids remained in Africa No prehensile tails

Hominoids include Apes Gibbon, orangutan, gorilla, and chimpanzee Larger brains than monkeys and lack tails Paraphyletic group – some more closely related to hominids Hominids Humans Soon after the gorilla lineage diverged, the common ancestor of all hominids split off from the chimpanzee line to begin the evolutionary journey leading to humans

Apes vs. Hominids

The common ancestor of apes and hominids is thought to have been an arboreal climber Hominids became bipedal, walking upright Apes evolved knuckle-walking Differences related to bipedal locomotion Human vertebral column is more curved Spinal cord exits from bottom of skull Humans carry much of the body’s weight on the lower limbs

Modern Humans

``` Modern humans first appeared in Africa about 600,000 years ago Three species are thought to have evolved Homo heidelbergensis (oldest) Coexisted with H. erectus Homo neanderthalensis Shorter and stockier than modern humans Homo sapiens (“wise man”) Some lump all 3 into H. sapiens ```

CHAPTER 35 Flashcards

(41 cards)