Chordates 2

Question 1

Two major lineages of lobe-fined fish

Answer 1

1. Coelancanths
2. Lungfish
   • Lineage diverges from lungfish that eventually leads to tetrapods.

Question 2

The evolution of legs

Answer 2

• Fossil record shows clean progression from lobe-finned lungfish to tetrapod
• Tiktaalik is a fossil intermediate between lobe-finned fish and tetrapods
  
  1. Has many fish-like traits (e.g. fins, scales, primitive jaws)
  2. Has tetrapod-like traits (e.g. fins with wrist, neck, expanded ribs, flat head)
• Digit number highly variable in early tetrapodomoph legs.
• Successful tetrapods have 5 digits.

Question 3

Evolution of Amphibians

Answer 3

A. Once tetrapods successfully invade land, two major lineages diverge, one leading to the Amphibians, the other leading to the reptiles and mammals

B. Important traits

1. Breath through primitive lungs, juveniles and some adults have gills. Capable of cutaneous respiration (i.e. breath through skin)
2. Fertilization external
3. Reproduction tied to water

C. Amphibians are closely tied to water for reproduction! This limits their terrestrial range.

a. Evolved from the water but still tied to the water
b. Have not made a clean break from the water yet
c. Always go back to water to reproduce

Question 4

Evolution of the Amniotes

Answer 4

• Breaks the tie to water and allows creates to live 100% away from water

A. Amniotic egg – extraembryonic membranes

1. Amnion - protects and provides shock absorbtion
2. Yolk sac- stockpile of nutrients for embryo
3. Allantois - disposal sac for metabolic waste
4. Chorion - allows for respiration across shell

B. Amniotic egg allows for water independence during reproduction.

C. Water independent reproduction leads to internal fertilization

D. Legs rearranged for carrying weight out of water

a. From sides to underneath to keep body from dragging on ground
- Allows for eggs to be placed away from predators = greater success

Question 5

Amniotic egg – extraembryonic membranes

Answer 5

1. Amnion - protects and provides shock absorbtion
2. Yolk sac- stockpile of nutrients for embryo
3. Allantois - disposal sac for metabolic waste
4. Chorion - allows for respiration across shell

Question 6

The reptiles

Extant Reptile

Answer 6

• Turtles
• crocodilians
• birds
• tuatara
• squamates

Question 7

The reptiles

Extinct Reptiles

Answer 7

1. Pterosaurs – independent evolution of flight
   i. Not a dinosaur
2. Dinosaurs – terrestrial lineage of large reptiles; likely endothermic; some feathered; give rise to birds
3. Plesiosaurs and ichthyosaurs – reinvade the water;
   i. are not dinosaurs
   ii. aquatic reinvasion in the reptile line
   iii. ichthyosaurs
4. gave life birth

Question 8

The mammals

Answer 8

produce milk, have hair <- 2 traits not in any other

1. Monotremes
2. Marsupials
3. Eutherians

Question 9

The mammals

Monotremes

Answer 9

1. Lay eggs, produce milk (but no nipples)
   
   • only mammals to lay eggs
2. E.g. platypus and echidna
   
   • the only 2 species

Question 10

The mammals

Marsupials

Answer 10

1. Rudimentary placenta, nipples
2. Pouch for fetal development
3. e.g. kangaroos, opossum

Question 11

The mammals

Eutherians

Answer 11

where humans are

1. Complex placenta
2. e.g. rodents, whales, bats, primates, elephants
3. primates

Question 12

The mammals

Eutherians:

Primates(derived traits)

Answer 12

1. Opposable thumb
2. fingerprints
3. large brain

Question 13

The mammals

Eutherians:

Primates(two groups)

Answer 13

1. Prosimians(lemurs and tarsiers)
2. Anthropoids
   - monkeys
   - apes

Question 14

The mammals

Eutherians:

Primates:

Apes(Five genera)

Answer 14

• Gibbons
• orangutans
• gorilla,
• chimpanzee
• humans

Question 15

The mammals

Eutherians:

Primates:

Apes:

Genus Homo(humans and others)

Answer 15

1. Bipedal
   
   • changes the attachment of neck to body to be upright
2. Enlarged cranial cavity / brain
3. Reduced lower jaw
   
   • trade jaw power for brain power due to weight
   • “morphological tradeoff”
4. Many species of homo coexist

Question 16

Homo genus age

Answer 16

2.5 MYA

Question 17

Homo sapiens age

Answer 17

200,000 years ago

Question 18

Many Homo species lived with Homo sapiens until _____.

Answer 18

about 20,000 years ago.

Question 19

Humans are not______.

Answer 19

lobe-fins or Osteichthyans but the rest of the names we are.

Question 20

Tetrapods evolved from _____.

Answer 20

lungfish.

Question 21

Monkeys and apes are different

Answer 21

• Do not mix them

Question 22

Evolution of Amphibians:

Once tetrapods successfully invade land _______.

Answer 22

two major lineages diverge, one leading to the Amphibians, the other leading to the reptiles and mammals

Question 23

Evolution of Amphibians:

Important traits

Answer 23

1. Breath through primitive lungs, juveniles and some adults have gills. Capable of cutaneous respiration (i.e. breath through skin)
2. Fertilization external
3. Reproduction tied to water

Question 24

Evolution of Amphibians:

Amphibians are closely tied to water for reproduction! This limits their terrestrial range.

Answer 24

a. Evolved from the water but still tied to the water
b. Have not made a clean break from the water yet
c. Always go back to water to reproduce

Question 25

The reptiles Extinct Reptiles: Pterosaurs

Answer 25

independent evolution of flight | i. Not a dinosaur

Question 26

The reptiles Extinct Reptiles: Dinosaurs

Answer 26

terrestrial lineage of large reptiles; likely endothermic; some feathered; give rise to birds

Question 27

The reptiles Extinct Reptiles: Plesiosaurs and Ichthyosaurs

Answer 27

reinvade the water; i. are not dinosaurs ii. aquatic reinvasion in the reptile line iii. ichthyosaurs 1. gave life birth

Question 28

Amniotic egg – extraembryonic membranes: Amnion

Answer 28

protects and provides shock absorbtion

Question 29

Amniotic egg – extraembryonic membranes: Yolk sac

Answer 29

stockpile of nutrients for embryo

Question 30

Amniotic egg – extraembryonic membranes: Allantois

Answer 30

disposal sac for metabolic waste

Question 31

Amniotic egg – extraembryonic membranes: Chorion

Answer 31

allows for respiration across shell