Download The Vertebrates

The Vertebrates
What is a vertebrate?
Phylum Chordata: all members have a flexible supporting sturucture called a
notochord along the back
Subphylum vertebrata: bones called vertebrae replace notochord
Vertebrae are the central part of the skeleton:
Attachment place for the skull, arms and legs
Attachment for muscles
Protection for nerve cord
Trends in vertebrate evolution
Development of bony jaws
Muscles can create a hard bite
Teeth can grow on the jaw
Simple mouth opening becomes a useful feeding tool
Development of paired pectoral (arm) and pelvic (leg) girdles
Two kinds of skeletons: cartilage and bone
Most vertebrates are tetrapods (four legged)
Classification of vertebrates
Backbone
Two sets of appendages
Closed circulatory system with a ventral heart
Either gills or lings for breathing
Living Vertebrates (This is class level classification, not Phylum level!)
Jawless fishes (Agnatha) (lampreys and hagfish)
Specialized parasites and scavengers
Cartilaginous fishes (Chondrichthyes) (sharks, skates and rays)
Skeletons are made of cartilage
Bony fishes (Osteichthyes) (fish)
Two subclasses: ray fin fish and lobe fin fish
Almost all the fish are ray finned
More than half of all the vertebrates are ray finned fish
Only a few lobe finned fish exist today but they are evolutionarily
important since they are the ancestors of the tetrapods.
Amphibians (Amphibia) (newts, salamanders, frogs and toads)
Lay their eggs in water and spend part of their life in water
Adults live on land and brate through lunds
Usually need to keep the skin moist
Nwts and salamanders have tails
Hatch in water, immatures have gills
Gills are replaced by lungs in adult satge
Frogs and toads do not hav etials as adults
Tadpoles hatch in water and are completely different than th adult
Reptiles (Reptilia) reptiles
First of the entirely terrestrial vertebrates
Internal fertilization
Produce leathery covered eggs
Dry scaly skin protects against water loss
Breath through lungs
Birds (Aves) birds
Only vertebrates with feathers
Feathers conserve heat
Lay eggs also
Mammals (Mammalia) mammals
Mammary glands to produce milk to nourish young
Have hair to conserve body heat
Three main groups:
Monotremes (egg laying mammals)
Very rare, platypus and spiny anteater are the only ones
Marsupials (pouched mammals)
Bear their young alive but very early
Receive nourishment form the mother in the pouch
Koalas and kangaroos live in Australia
Opossum live in North America
Placental mammals
A placenta connects the mother to the developing embryo
Bats, primates, rodents, whales, carnivores are examples
Vertebrate anatomy and physiology
Support and movement
Endoskeleton surrounded by muscles
Central element of the skeleton is the vertebral column
Adaptation to land required a change in limb positions
Amphibians; limbs are horizontal to the body
Reptiles: limbs became more vertical to the body
Feeding and digestion
Each type of food presents problems
Adaptation to eating different food is seen in the teeth
Eating meat: teeth need to hold and tear the meat
Eating plants: teeth need to pulverize the plants
Digestion is different also
Meat: easy to digest, carnivores have short digestive tracts, secrete
enzymes to digest the meat
Plants: difficult to digest, herbivores have longer digestive tracts,
have places for bacteria to live to digest cellulose for them
Respiration
Different strategies depending on environment
Fish and amphibians
Fish rely on gills
Amphibian immatures rely on gills
Amphibian adults have lungs but they are not efficient, there are no
muscles in amphibians to inflate of deflate lungs
Amphibian adults rely on gas diffusion through their thin moist
skin
Reptiles
Fully developed lungs
Divided into small cambers (increases surface area, remember
why!!!!)
Muscles to inflate and deflate lungs are present
Mammals
Need high rate of gas exchange because of high metabolism
Lungs with very high surface area
Extensive branching to very small surfaces that are supplied with
blood
Inefficient in that inhalation and exhalation use the same
passageway
Birds
Highest metabolism of all the vertebrates
Bird flight is long term high intense exercise
Air is pumped in the bird lung in one direction
Birds have air sacs in their bones as well
Circulatory systems
Two main types: single loop and double loop
Diagram on page 792
Single loop
Typical in fish
Blood is pumped from the heart to the gills, from the gills to the
body and returns to the heart
Double loop
Vertebrates with lungs have this
Heart pumps blood to the lungs, blood returns to the heart, blood is
pumped to the rest of the body, returns to the heart
Temperature control
Fish, amphibian and reptiles rely on interaction with the environment to
control body temperature
They are called ectotherms for this reason
Mammals and birds generate heat in their body, and have insulating
tissues (fat, hair, feathers) to control heat loss
They are called endotherms for this reason
Why control heat? Chemistry happens at different rates at different
temperatures. Control temperature near the optimum temperature for most
enzymes means more effect reactions and utilization of energy
Excretion
Elimination of nitrogen waste is tied to water conservation
Fish and amphibians lose ammonia through their skins
Vertebrates developed kidneys (organ specialized for nitrogen excretion)
Mammalian kidney is the most complex
Urea/uric acid chemistry used here as well (like invertebrates)
Response
All vertebrates show high levels of cephalization (concentration of nerves
and sense organs in the head)
All vertebrates have a brain with a cerebrum and a cerebellum
Nerves run in and out of the spinal cord at the vertebrae joints
Reproduction
All vertebrate reproduce sexually
Fertilization can be external (fish and amphibians)
Fertilization is internal inside the body of the female (all others)
General trend is to go from external to internal fertilization as you move
from fish to mammals
External fertilization
Eggs produced by the thousands,
Sperm and eggs mixed in water
Immature hatches and develops in water
Internal fertilization
Fertilization occurs inside female body
Few eggs are produced
Eggs includes a food supply for the embryo, yolk,
Membranes to conserve water and a shell for protection and gas
exchange
This type of egg is called the amniotic egg (one of the membranes
is the amnion)
This type of egg was a significant adaptation to life on land
Different methods of handling the egg
Oviparous
“Lay the egg”
Eggs complete their development and hatch outside the
female body
Ovoviviparous
Eggs kept inside female body until they hatch (some sharks
and bony fishes do this)
Viviparous
Eggs have very little yolk
Embryo is kept inside the female body for long periods
Female supplies embryo with nourishment during
development
Young born alive, they do not “hatch”