Tetropods Flashcards
what was one evolutionary step from sea to land?
- the presence of internal nostrils (opening from the nasal sac into the roof of the mouth)
- this was the first component of the tetrapod body plan to evolve
- it evolved from the displacement of an external nostril
- tetrapods only have one pair of external/anterior nostrils
- posterior –> internal nostrils called choanae
- posterior goes to throat and anterior goes to olfactory
Which structure gave rise to limbs with joins that allow vertebrates to move onto land?
- the lobe fins of the fish (lobe fins had skeleton and muscle to help them move and it had a homologous trait with all tetrodes which is the bone structure)
What are some reasons why they tranisitoned to life on land?
- continental drift and rise of pangaea
- plants beginning to colonize land and make forests
- arthropods and other invertebrates were colonizing land (they are food for tetrapods)
- most predators were aquatic
- fewer competitors on land
- new niches
What are 6 challenges of terrestrial life for organisms adapted to aquatic life?
- gravity –> most species were helped move by buoyancy in the water … air was buoyant and animals had to have supporting tissues
- desiccation: air is drier than water so they need some skin coating to prevent themselves from drying out and preventing body fluids from leaking out and protecting their embryo
- respiration: aquatic organisms exchange oxygen and co2 dissolved in water. in air these substances are gasses so they have to change the way they breathe
- reproduction –> aquatic organisms released gametes into water but this is less effective in air
- locomotion: aquatic animals can swim but they have to modified in terrestrial life
- temperature: temperatures fluctuate more in air than water –> they have to evolve adaptations to deal with fluctuations like homeostasis (maintaining internal temp through own metabolism)
How did early land plants like liverworts and mosses live? (not fully converted to terrestrial life)
- water played a huge role in their life cycle
- they had no cuticle, vascular tissue or woody tissue for structure support
- sperm needed water to swim (even in ferns)
- they couldn’t grow tall and were always restricted to wet envrionemnts
what were some adaptations for life on land in plants?
- waxy cuticles –> waterproof epidermis (helps with desiccation)
- Vascular tissue –> transports water to tissues and is used as structural support (helps with gravity)
- Stomata –> allows for gas exchange, minimizing desiccation (helps with respiration)
- Pollen, seeds, and dependent gametophyte –> new reproductive strategies for life on land (reproduction)
What species was an intermediate between fishes and tetrapods?
it was called tiktaalik (375 MYA)
- it had fishy features like scales, fins without digits and gills AND lungs
- it had tetrapod features like neck, ribs, fin skeleton and eyes on top of head (fish have eyes on the side)
What did the neck allow the tiktaalik to do? what were some features about its neck?
its neck allowed it to move head independently of body (up and down and side to side)
- their shoulder was also not fused to the skull like in tetrapods –> causing a NECK
What was the characteristics of the evolution of pelvic girdle seen tiktaalik?
- their pelvic girdle was not attached to vertebrate
- the shape and size of their hip pocket (pelvis) show that their fins could do a lot of things from swimming to supporting their weight a little bit
- overal structure of the pelvis is still more fish like because it is made of one bone when tetrapods have 3 parts of bone and its not attached to vertebrate like tetrapods pelvis are
What was the earliest tetrapod and what was it features?
- acanthostega –> primitive traits such as: gills, lateral line, long fin rays around rail
- it had no true elbows, knees wrists or ankles and did not bear its own weight
- it had derived traits –> 4 limbs with bony digits, and a pelvis thats weakly attached to vertebrate and they are also primarily aquatic … their limbs were used to eat stuff on the shore
What is the first evolved amphibian? What are its characteristics
- ichthyostega (early amphibian)
- this one had 7 digits instead of 5 digits per limb, which shows that 2 digits were lost during evolution
- its primitive traits were gills and lateral lines
- its derived traits were limbs attached to vertebrate, weight bearing joints like the ulna, and the fibula …etc.. like elbows, wrists, knees and ankles
- its hips also attached to the vertebrate which provided more structure support and could allow it to actually walk
describe the evolution of tetrapods in names of fish going down to human
starting from the oldest
- ray-finned fish –> bony skeleton lost
- coelacanth
- lungfish –> lobe fins
- euthenopteron —> lobe fins
- Tiktaalik
- acanthostega –> ribs and neck
- ichthyostega –> limbs w digits, pelvis attached to vertebrate
- humans/ and tetrapods today –> 5 digits and loss of fins
