lecture 7 Flashcards
what were the 4 advantages to moving onto land for the early tetrapods?
- abundant food resources
- rarity of predators
- readily available oxygen
- warmer conditions increase metabolic rate so better performances
what 4 characteristics in the ancestor of the tetrapod preadapted them to life on land?
- strong fins for crawling on the muddy bottom
- strong vertebral column to support body
- nostrils and olfactory receptors
- lungs that supplement gill respiration
which are the 3 main characteristics of the amniotes that allowed them to become so successful? How are these characters similar to those that contributed to the success of insects?
- a tough, waterproof skin containing keratin and lipids= prevents dehydration
- amniote eggs=survive and develop on dry land
- semisolid uric acid as a waste product of nitrogen metabolism= prevents waterloss
which are the 2 main lineages within Amniota (both have amniote egg) ?
- synapsida =fur, milk
2. reptilia=scales with hard keratin
In addition to losing their legs over evolutionary time, how do the snakes differ from their lizard relatives?1
snakes have smaller skull bone with more elastic connections between them
How do the diets of lizards and snakes differ? How are the differences reflected in skeletal structure?
various species of lizards feed on vegetation, insects, or larger animals. Virtually all snakes are carnivores and they swallow their prey whole
what parts of the life cycle in most modern amphibians are dependent on water/ very moist habitats (2)
egg and larval stages
how does the overall structure of turtles distinguish them from other amniotes
turtles bodies are enclosed with a bony, keratin-cover shell
how did the evolution of the amniote egg free amniotes from a dependence on standing water
because the egg can survive on land. The shells of amniote eggs mediate gas exchange and water exchange with the environment
what 2 groups of animals are included in each of the 2 major amniote lineage
- Synapsida (includes the mammals)
2. Reptila (includes the turtles, lizards, snakes, crocodilians, and birds)
based on the evolutionary history of the amniotes, crocodillians more closely related to birds or lizards?
- lizards are lepidosaurs
- birds and crocodilians are archosaurs, crocodilians are more closely related to birds than they are to lizards
what were the 3 disadvantages to moving onto land for the early tetrapods?
- need for more skeletal support against gravity (air provides less support for animal’s body- water had buoyancy)
- mechanisms to prevent dehydration in air (evaporation)
- modification to sensory systems so that they would function in air
early tetrapods could detect sound in air because they had a
tympanum (membrane) is vibrated by airborne sounds, which are received by stapes (tiny bones), which transfer vibrations to sensory cells of an inner ear
amphibian reproduction 4
- eggs are laid in water
- hatch into larvae (tadpoles with external gills)
- metamorphosis
- adults may be aquatic or terrestrial
what are the 3 lineages of amphibians
- anura (frogs and toads)
- caudata (salamanders and newts)
- gymnophiona (caecilians)
2 properties of anura
- adults without tails
2. long hind legs with webbed feet
2 properties of caudata
- elongate, tail , 4 legs
2. lungless salamanders are fully terrestrial, use skin and lining of throat for gas exchange
3 properties of caecilians
- legless burrowing animals with wormlike bodies
- internal fertilization -females give birth to live young
- small scales
amniote egg has 2 components.
- shell
2. 4 extraembryonic membranes
the extraembryonic membranes have 4 functions
- protection
- gas exchange
- excretion
- provide nutrients
which are the 2 main lineages within Amniota (both have amniote egg) and how are they different to each other?
4 and 2 differences
Synapsida :
- glandular skin (milk glands)
- fur/hair
- give birth to live young
- suckle young
Reptilia:
- dry scaly non-glandular skin
- birds have feathers which are modified scales
2 lineages of reptilia
- lepidosauria
2. archelosauria
2 living lepidosaurs
- Squamata =lizards and nakes
2. Sphenodontia
Archelosauria include 3 living species (include phyla that fall under it)
- testudines
- ARCHOSAURIA -crocodilia
- DINOSAURIA- Aves
what specie does the sphenodontia include and one characteristic of it
tuatara-teeth fused to jaw
4 properties of squamata (snakes and lizards)
- moderately to high kinetic skulls- teeth arent fused to jaw
- overlapping, kerainised scales prevent dehydration
- periodically shed there skin as they grow
- regulate body temperature behaviourally
how and what do lizards eat
eat insects, leaves or meat.
can take bites out of food (due to kinetic skull)
3 well developed sensory systems that snakes have for detecting prey
- sensory receptors on roof of mouth
- heat sensing organs
- detect vibrations
how do snakes eat (2)
- Swallow prey whole - bone of skull connected by elastic ligaments.
- use venom or constriction
testudines include 2 species
turtles and tortoises
testudines lack teeth, what do they have instead?
a keratinized beak and powerful jaw muscles
testudines body plan includes 2 things (and 2 extra points under this)
Boxlike shell with a dorsal caraspace and a vental plastron
- ribs =used to caraspace
- pectoral and pelvic girdles lie within the ribcage
- large keratinized scales cover the bony plates of the shell
