Phylum Chordata Notes

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PHYLUM CHORDATA

Characteristcs of Chordates:
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1)
2)
3)
4)
all chordates have 4 characteristics in common at some point
in their life cycle:
dorsal, hollow nerve tube: in most adult chordates, the
posterior part develops into a spinal cord and the anterior
part develops into a brain
notochord: firm flexible tube just below the nerve
tube(backbone in vertebrates), where muscles can attach
gill slits: paired openings along the pharynx which
functions in filter feeding
post-anal tail: at some point during development, a tail
reaches beyond the anus
The Phylum Chordata Includes:
1.
2.
3.
Subphylum Cephalochordata (=lancelets)
Subphylum Urochordata (= tunicates)
Subphylum vertebrata:
•
Class Agnatha - jawless fish
•
Class Amphibia
•
Class Aves – birds
•
Class Chondrichthyes - cartilaginous fish
•
Class Osteichthyes - bony fish
•
Class Reptilia
•
Class Mammalia
Characteristics of All Vertebrates


1. have a backbone, which surrounds spinal cord, is made
up of bony segments called vertebrae
2. an endoskeleton which has two main parts:
i. Axial Skeleton: made up of the vertebral column,
skull & rib cage
- supports body and protects spinal column,
brain & other internal organs
ii) Appendicular Skeleton: made of the appendage
bones and wide flattened girdles to which they are
attached
- is attached to axial skeleton
- ex. arms, legs
3. Well developed brain & sensory organs
4. A closed circulatory system
5. Multi-chambered heart
6. Bilateral symmetry
7. Coelomates
8. Efficient respiratory systems
9. Only phylum to have bones
FISHES


Inhabit nearly every type of
aquatic environment on Earth
Can be grouped into 4 classes:

Super Class Agnatha:


1. Class Myxini: hagfish
2. Class Cephalaspidomorphi:
lampreys
3. Class Chondrichthyes:
cartilaginous fish (ex. Sharks &
rays)
 4. Class Osteichythes: bony fish
(ex. Swordfish, tuna, trout…)

Characteristics of All Fish

1. breathe using gills
•

as a fish takes water in through its mouth, water passes over the gills &
then out through slits at the side of the fish
2. have 2 chambered hearts
•
•
One chamber receives oxygen-poor blood from the body tissues
The other chamber pumps blood directly to the capillaries of the
gills, where oxygen is picked up & carbon dioxide released

3. reproduce sexually
•
•

Fertilization & development is external in MOST fishes
Eggs & sperm can be released directly into the water, or deposited in
more protected areas
4. highly developed sensory systems
Have eyes that allow them to see objects & contrasts between
light & dark in the water, but the amount of vision varies among fishes
•
SUPER CLASS AGNATHA



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jawless fish
lampreys & hagfish
have smooth, scaleless skin & long cylindrical body
Lampreys:


most are parasites that hitch rides on their hosts, often killing
its host as it sucks out its victim’s body fluids
Hagfish:


bottom dwellers that spend most of their time hiding in mud
& sand
scavenger that eats fish that are already dead or dying
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