Phylum Chordata

Phylum Chordata

• triploblastic

• coelom

• tough cartilaginous tissue (Notochord) → acts as endoskeleton

• pharyngeal slits

• hollow dorsal nerve chord

• notochord

• post anal tail

• ventral heart

• myostome muscles

Pharyngeal Slits

• filter feeding mechanisms

• in fish evolved to gill arches and gill slits

• primates evolved to the jaw and ear bones

Hollow Dorsal Nerve Chord

• becomes spinal cord in vertebrates

Notochord

• in invertebrate chordates the notochord is endoskeletal support tissue

• in vertebrates it forms the spinal column

• notochord tissue then forms the spinal cartilaginous discs

Post- Anal Tail

• lost in primates

• still visible in the embryonic stages

Myotome Muscles

• muscles arranged in blocks

• supplied by a single nerve → effective and efficient

• evidence of segmentation ancestry

Ventral Heart

• located on the ventral side unlike the dorsal heart of protostomes

• (located on the belly side)

Vertebrata

• all animals with skull and backbone

• vertebral column → segmented backbone joined by pectoral and pelvic gurdle

Evolution of a Circulatory System - explain advantages of a closed circulatory system

• vertebrates have a closed circulatory system with a multichambered heart

→ advantages

• More efficient blood flow

• Higher blood pressure

• Better control of blood distribution

• Efficient oxygen and nutrient delivery

Explain the heart of fish, amphibians, reptiles, birds and mammals

• fish: 2 chambered heart - single circulation

• amphibians: 3 chambered heart -2x circulation

• reptiles - 4 chambered heart - 2x

• birds and mammals - 2x and 4 chambered heart

Advantages of a double circulatory system? How does the four-chambered heart help this adaptation

• Keeps oxygen-rich and oxygen-poor blood separate → systemic circulation always has highest blood conc possible

• Maintains higher blood pressure for faster delivery

• Improves oxygen supply to body tissues

  4-chambered heart:

• Completely separates oxygenated and deoxygenated blood

• Prevents mixing, maximizing oxygen delivery and efficiency

Explain how fish are able to survive despite having the least efficient vertebrate circulatory system

• Lower oxygen demands (ectotherms, slower metabolism)

• Efficient gills that extract enough oxygen from water

• Living in buoyant aquatic environments, needing less energy for support and movement

The 4 chambered heart evolved twice independently - in crocodiles and in birds/mammals what does this tell us about the 4 chambered heart

It tells us that the 4-chambered heart is such a useful structure, it evolved more than once in different animals.

That makes it a great example of convergent evolution — when different animals evolve similar features to solve the same problem.

Pentadactyl Limb

• evolved from when Sarcopterygii developed lobed fins with bones

• grew stronger until they could support the weight of the animal off the ground

• evolved into 5 digits

• used to climb, crawl, fight

• humans developed opposable thumbs and are able to manipulate tools

Advantage of lifting body off the ground instead of dragging it along

• Less friction with the ground – makes movement easier and faster

• Improves speed and efficiency – less energy is wasted

• Prevents injury or wear – protects the body from scrapes and damage

• Better balance and coordination – especially important for walking or running

• Frees up limbs for other functions (e.g. grabbing, climbing, tool use in some animals)

Bones in the Hind legs

• femur

• tibia +fibula

• tarsals

• metatarsals and phalanges

Bones in Front limbs

• humerus

• radius + ulna

• carpals

• metacarpals + phalanges

Series of adaptations for animals to live outside of the water

• mineralized exoskeleton

• internalized respiratory organs

• cleidoic eggs with shell and extraembryonic membranes

• impermeable epidermis (minimize water loss)

Amniotic/Cleidoic Egg

• to protect the embryo

  • leathery shell in reptiles'/mammals

  • calcified shell in birds

• 4 membrane layers

• yolk sac

• amnion → embryonic protection

• chorion → gas exchange

• allantois → metabolic waste disposal/storage

later evolved viviparity - gave birth to live young instead

What are the advantages of transferring the contents of the cleidoic egg into the female’s body as what happened with placental mammals?

• Better protection: The developing embryo is protected from predators and environmental dangers.

• Controlled environment: The mother can regulate temperature, providing a stable developmental space.

• Efficient nutrient and oxygen supply: The placenta delivers nutrients directly, supporting faster growth.

• Waste removal: The placenta removes waste products, maintaining embryo health.

• Increased mobility: The mother can move freely, keeping the embryo safe while not having to guard eggs.

Class Mammalia

• sweat glands

• mammary glands

• hair

• external ear pinna

• 4 chambered heart

• placenta which connects embryo to uterus wall

• uterus

• embryo is contained in an amniotic sac