Week 15

Question 1

Of the following challenges faced by vertebrates moving from an aquatic to a terrestrial environment, which one was the most important?

Answer 1

Preventing the body from drying out

Question 2

Amphibians have successfully invaded the land; however, most are tied to water for _____.

Answer 2

Blank 1: reproduction, reproducing, breeding, or reproduce

Question 3

Which of the following was one of the biggest challenges to amphibians as they adapted to life on land?

Answer 3

Dehydration

Question 4

Tetrapods spread from North America to Asia after the supercontinent, _____ , was formed

Answer 4

Pangea

Question 5

Tiktaalik was probably an intermediate between ____

and tetrapods.

Answer 5

fish

Question 6

Which of the following are challenges amphibians had to overcome when adapting to a life on land?

Answer 6

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

Question 7

Which of the following accurately describe why amphibians are tied to water for reproduction?

Answer 7

To prevent eggs from drying out

Question 8

Tetrapods became common during the ____

period (360 to 289 MYA).

Answer 8

Carboniferous

Question 9

As ______were the first vertebrates to adapt to a _____ life, one of their biggest challenges was to prevent their bodies from drying out.

Answer 9

Blank 1: amphibians

Blank 2: terrestrial or land

Question 10

Identify the three orders of amphibians:

Answer 10

Blank 1: Anura
Blank 2: Caudata
Blank 3: Apoda

Question 11

The earliest fossils of the first tetrapods were found in what area?

Answer 11

Greenland

Question 12

Which of the following amphibians do not have tails?

Answer 12

Frogs

Toads

Question 13

The fossil, ____ , discovered in Canada in 2006 had gills and scales like a fish but a neck like an amphibian.

Answer 13

Tiktaalik

Question 14

Larval salamanders have external gill and gill slits. During metamorphosis what happens to these structures?

Answer 14

They disappear.

Question 15

Which amphibians are legless, wormlike creatures with small eyes and are often blind?

Answer 15

Caecilians

Question 16

In the early Permian period, the tetrapods began migrating from marshes to which of the following habitats?

Answer 16

Dry uplands

Question 17

The ______ egg is considered to be a “key innovation” because it permitted animals to lay their eggs in a greater variety of environments.

Answer 17

amniotic

Question 18

During the ______

period, moist-skinned amphibians successfully invade the wet habitats world wide.

Answer 18

Tertiary

Question 19

Identify the type of reproduction carried on by frogs and toads.

Answer 19

Sexual, external fertilization

Question 20

Most salamanders practice which of the following types of reproducion?

Answer 20

Sexual, internal fertilization

Question 21

Which order of amphibians includes a highly specialized group of tropical burrowing amphibians that are the Caecilians?

Answer 21

Apoda

Question 22

What are the three orders of living amphibians?

Answer 22

i) Caecilians;
ii) Newts and Salamanders,
iii) Frogs and toads.

Question 23

What does evidence from DNA sequencing tell us about Frog/Toad relations?

Answer 23

Evidence from DNA sequences suggests that the Frogs/Toads are more closely related to Salamanders, than Caecilians.

Question 24

How far do Caecilian, Salamanders and frogs date?

Answer 24

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.

Question 25

Summarise the clade 1- Caecilians

Answer 25

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

Question 26

Caecilians belong to the order

Answer 26

Apoda (- without feet), they are also known as Gymnophiona (gymnos – naked; ophis – snake)

Question 27

How are Caecilians characteristised?

Answer 27

They are characterised as being elongate, without limbs or limb girdles. This is an example of a “secondary loss” of limbs

Question 28

What do most Caecilians have?

Answer 28

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.

Question 29

What are Caecilians highly specialised for?

Answer 29

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”.

Question 30

Where are the Caecilians found?

Answer 30

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.

Question 31

Because caecilians are _____ _____, or _____ ____, and they have no ____ openings, other senses are important.

Answer 31

poorly sighted, or totally blind,

ear

Question 32

What are features of the Caecilians sensory system?

Answer 32

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.