Week 15 Flashcards
Of the following challenges faced by vertebrates moving from an aquatic to a terrestrial environment, which one was the most important?
Preventing the body from drying out
Amphibians have successfully invaded the land; however, most are tied to water for _____.
Blank 1: reproduction, reproducing, breeding, or reproduce
Which of the following was one of the biggest challenges to amphibians as they adapted to life on land?
Dehydration
Tetrapods spread from North America to Asia after the supercontinent, _____ , was formed
Pangea
Tiktaalik was probably an intermediate between ____
and tetrapods.
fish
Which of the following are challenges amphibians had to overcome when adapting to a life on land?
Obtaining enough oxygen without using gills
Prevent body from drying out
Needing water to complete the reproduction cycle
Delivering enough oxygen to muscles needed for land movement
Moving a large body mass without being buoyant in water
Which of the following accurately describe why amphibians are tied to water for reproduction?
To prevent eggs from drying out
Tetrapods became common during the ____
period (360 to 289 MYA).
Carboniferous
As ______were the first vertebrates to adapt to a _____ life, one of their biggest challenges was to prevent their bodies from drying out.
Blank 1: amphibians
Blank 2: terrestrial or land
Identify the three orders of amphibians:
Blank 1: Anura
Blank 2: Caudata
Blank 3: Apoda
The earliest fossils of the first tetrapods were found in what area?
Greenland
Which of the following amphibians do not have tails?
Frogs
Toads
The fossil, ____ , discovered in Canada in 2006 had gills and scales like a fish but a neck like an amphibian.
Tiktaalik
Larval salamanders have external gill and gill slits. During metamorphosis what happens to these structures?
They disappear.
Which amphibians are legless, wormlike creatures with small eyes and are often blind?
Caecilians
In the early Permian period, the tetrapods began migrating from marshes to which of the following habitats?
Dry uplands
The ______ egg is considered to be a “key innovation” because it permitted animals to lay their eggs in a greater variety of environments.
amniotic
During the ______
period, moist-skinned amphibians successfully invade the wet habitats world wide.
Tertiary
Identify the type of reproduction carried on by frogs and toads.
Sexual, external fertilization
Most salamanders practice which of the following types of reproducion?
Sexual, internal fertilization
Which order of amphibians includes a highly specialized group of tropical burrowing amphibians that are the Caecilians?
Apoda
What are the three orders of living amphibians?
i) Caecilians;
ii) Newts and Salamanders,
iii) Frogs and toads.
What does evidence from DNA sequencing tell us about Frog/Toad relations?
Evidence from DNA sequences suggests that the Frogs/Toads are more closely related to Salamanders, than Caecilians.
How far do Caecilian, Salamanders and frogs date?
From the fossil record, the earliest Caecilian is from the Early Jurassic (176-200 MYA), the earliest salamander is from the mid Jurassic (161-176 MYA) and the earliest frogs from the late Triassic (200-228 MYA).
However, as is usually the case, molecular DNA evidence (using molecular clocks) show that the divergences occurred earlier than the fossil evidence suggests.
Molecular clock evidence suggests these started to diversify from one another around the Carboniferous period (~350 MYA) during the Palaeozoic Era.
The basal divergence of the living members of the three living orders seems to have taken place around 250 MYA.
Summarise the clade 1- Caecilians
Order Apoda (Gymnophiona)
Elongate without limbs or limb girdles
Most have very small eyes; some species eye covered by skin
Smallest ~5cm, largest 150cm
Body segmented by annular grooves, some species have scales
Caecilians belong to the order
Apoda (- without feet), they are also known as Gymnophiona (gymnos – naked; ophis – snake)
How are Caecilians characteristised?
They are characterised as being elongate, without limbs or limb girdles. This is an example of a “secondary loss” of limbs
What do most Caecilians have?
Most have very small eyes, sometimes covered in skin or bone. They are typically small but vary between 5cm and 150cm in length. The body is segmented by annular grooves, and some species have scales.
What are Caecilians highly specialised for?
Caecilians are highly specialised for burrowing: their traits include heavy compact skulls and recessed mouths. The head acts as a battering ram, enabling the animal to force itself through the soil. Some aquatic species have a small, raised “fin” along the posterior portion of the body to aid in swimming and the result is an eel-like appearance. The left lung is reduced in size and rudimentary, probably a result of the evolution of the elongate body shape. Exactly the same adaptation has taken place in snakes: - an example of “convergent evolution”.
Where are the Caecilians found?
Moist forest soil, some in freshwaters
Tropical (so no UK species)
~ 170 species, in 6 families and 34 genera
Caecilians are typically found in moist forest soils, but some are found in freshwaters. They are tropical, and have a wide distribution including South America, Africa and Asia. In total there are an estimated 170 species, distributed in 6 families, and 34 genera.
Because caecilians are _____ _____, or _____ ____, and they have no ____ openings, other senses are important.
poorly sighted, or totally blind,
ear
What are features of the Caecilians sensory system?
They retractable tentacles on the head that carry chemical cues (odour particles) from the environment to the nasal cavity. They use this sensory system to, in part, locate their prey.
Have no ear openings.
Likely that they rely on retractable tentacles for sensing prey and mates.
Tentacles carry chemical cues from the environment to the nasal cavity.
