Vertebrate Lineages

Question 1

Reptiles

Answer 1

the dominant terrestrial vertebrates ~250-66 MYA, and clade of Sauropsides called DIAPSIDS, which are the ancestors of lizards, snakes, turtles, crocodilians, dinosaurs, and birds

Question 2

Diapsids

Answer 2

defined by the presence of 2 temporal openings (holes) in each side of the skull; this structure allows for attachment of larger + stronger jaw muscles and wider jaw openings, compared to Amniotes lacking these skull holes

Question 3

Reptiles: Respiration

Answer 3

• use lungs to breathe and have scaly skin containing keratin + waxy lipids, which reduces water loss from the skin
• this thick, impermeable skin means reptiles cannot use their skin for respiration like Amphibians, thus all breath with LUNGS

Question 4

Reptiles: Heat

Answer 4

• ECTOTHERMIC (main source of body heat comes from the environment)
• categorized as poikilotherms (animals whose body temp. vary rather than remain stable)
• they have behavioral adaptions to regulate body heat like basking in sunny or shady spots
• advantages of ectotherms is the low metabolic energy needed to survive

Question 5

Reptiles: Evolution

Answer 5

• earliest reptiles appear in the FR ~320 MYA, and the earliest known true reptile was an ANAPSID (unlike modern reptiles), meaning it had a solid skull with no holes
• no holes = smaller jaw muscles = weaker jaw strength

Question 6

Birds

Answer 6

only group of dinosaurs still living; evolved ~100-150 MYA from a group of dinosaurs called THEROPODS

Question 7

Birds: Evolution

Answer 7

• the Archaeoptery is a fossil of an animal intermediate between theropods and birds
• the fossil appears to have characteristics of both animals; the fossilized skeleton + teeth is that of a dinosaur and it had flight feathers like modern birds

Question 8

Birds: Feathers

Answer 8

• characteristic that sets birds apart from other modern vertebrates
• modified scales
• allow for flight
• effective insultation to decrease heat loss
• play roles in camouflage or social signaling

Question 9

Birds: Heat

Answer 9

• birds are ENDOTHERMIC (produce their own body heat via their metabolism)
• endothermy requires more energy + food
• since birds fly, they require high energy and have a high metabolic rate

Question 10

Mammals

Answer 10

evolved ~200-230 MYA from a group of reptile-like amniotes called SYNAPSIDS

Question 11

Synapsids

Answer 11

defined by the presence of a single hole in each side of the skull that allows for attachment of larger, stronger jaw muscles and wider jaw openings

Question 12

Mammals: Evolution

Answer 12

• evolved from a group of synapsids called Therapsids, and the cynodonts are the group of therapsids that include the MRCA of all mammals
• amniotes that retain the feature of the amniotic egg, though only one group (monotremes) still lay eggs
• all mammals produce milk from mammary glands for their offspring

Question 13

Mammals: Skeletal System

Answer 13

• lower jaw consists of just one bone
• additional jaw bones found in other vertebrates have been modified to function in hearing and form the 3 small bones in the mammalian ear (one way to distinguish mammals from other synapsids)
• the musculature of the jaw allows side to side movement and makes chewing possible
• Chewing is unique to mammals, and most have different types and shapes of teeth

Question 14

Mammals: Hair

Answer 14

heavily modified scales; hair, feathers, and scales are homologous structures of amniotes
- effective insulation to decrease the rate of heat loss
- hair coloration play roles in social signaling + camouflage

Question 15

Mammals: Heat

Answer 15

are ENDOTHERMIC; evolved independently in mammals and birds and is NOT a homologous trait

Question 16

Mammals: Clades

Answer 16

living mammals belong to 3 clades; many other clades are now extinct:
1. Eutherians (placental mammals like humans)
2. Marsupials (metatherians which have like birth but no placenta, and the young develop in a pouch (kangaroos)
3. Monotremes (lay eggs like platypus)

Question 17

Vertebrate Adaptations to Dry Environments OVER GEOLOGIC TIME

Answer 17

1. First vertebrates were fish-like aquatic animals that lived early-Paleozoic
2. The capable of leaving the water were amphibians (evolved mid-Paleozoic). This era featured swampy, wet conditions amphibs flourished in, where they could survive and reproduce. The Carboniferous Period saw amphibian tetrapods become dominant predators on land
3. First Amniotes evolved mid-Paleozoic, but were largely outcompeted by amphibians occupying many available land niches. As conditions became drier, amniotes flourished due to adaptations

Question 18

Amniotes Water to Land Adaptations

Answer 18

1. Amniotic Egg (allowed them to reproduce away from water)
2. Lungs (allowed for evolution of desiccation resistant skin covering like scales, feathers, and hair since gas exchange did not have to take place in the skin if lungs were present)
3. Scales/Feathers/Hair (provided protection against dehydration while moist amphibians required sufficient water to prevent dehydration)