UNIT 4 DAY 1 - Your Inner Fish

Question 1

what kind of rocks are the fossils found in

Answer 1

sedimentary rock (formed as small rock particles settled out of water)

Question 2

scientists who looked for a fossil intermediate between fishes and tetrapods found a fossil locality that…

Answer 2

had rocks right of the age, which are now located in the artic

Question 3

serendipity is the last step in finding fossils because

Answer 3

once looking in rocks of the right age and time, you still have to be lucky to find the fossils

Question 4

sonic hedgehog

Answer 4

gene that is turned on during development of limbs in vertebrae

Question 5

tikaalik

Answer 5

transitional fossil between fish and amphibians with a wrist

Question 6

ADD FIGURE

Answer 6

the vertebrate archeotype, which Charles Darwin viewed as the platonic form of all vertebrates

Question 7

homologies

Answer 7

similar structure but adapted for different purposes

Question 8

lines of evidence in reconstructing our history

Answer 8

• fossils
• genes
• embryos
• living adult bodies

Question 9

maximising chances of fossil finding

Answer 9

• identify time period
• find the rocks
• look for areas where rocks are accessible
• bones are “weathering out”
• planning takes palaeontologist to promising sites but also must think on their feet

Question 10

homologies

Answer 10

same organs in different animals under every variety of form and function

Question 11

tetrapod (Ancestral Terrestrial Vertebrate) pattern

Answer 11

1,2, many, 5

Question 12

sharing homologous organs

Answer 12

• group species within nested groups, but can have different lives

Question 13

forearm

Answer 13

humerus, radius & ulna, carpals, metacarpals & phalanges

Question 14

Grand Facts 2 and 3

Answer 14

• reflected aspects of gods mind in creation

Question 15

archetype

Answer 15

model summarising the homologies characteristics a group of organisms

Question 16

why do homologies exist

Answer 16

• homologies exist because species in evolving from one to another, pass on their descendant species, same structures they possessed
• structures modified as descendants of common ancestor evolve new ways of life, but still recognise similarity due to descent

Question 17

Phylogeny

Answer 17

history of life –> evolutionary tree

Question 18

How can we use the the features of living adult bodies to reconstruct evolutionary history of a group?

Answer 18

1. Everything in the figure has a head, so heads must be homologous structure that evolved in the ancestor of all four species of the page. We’ll place heads at the base of the tree
2. Humans, dogs, and salamanders also all have legs, so legs must have evolved in the ancestor of humans, dogs, and salamanders, after fish had branched off the tree
3. Humans and dogs both have hair and mammary glands (breast), so hair and breasts must have evolved in the ancestor of humans and dogs after salamanders had branched off the tree
4. Only humans walk on two legs, so that must have evolved in the ancestor of humans after dogs had branched off the tree

Question 19

How can we use the the features of fishes to reconstruct evolutionary history of a group?

Answer 19

1. the fossil amphibian Acanthostega (360 mya) had everything humans have, a humerus, radius, ulna, wrist, and digits
2. Based on this phylogeny, Shubin predicted that at 365 mya he would find a fish with a humera, radius, ulna, and wrist, but with fin instead of digits
3. The fossil fish Eusthenopteron (370 mya) had a humerus, radius, and ulna, with a fin at the end
4. Lungfish have a fin like zebrafish, but with much more robust supporting bones. The first bone is the homologue of our humerus bone
5. Zebrafish have pectoral fins homologous to human arms, but no supporting bones homologous to those of our arm. Instead they have a fin supported by bony ray

Question 20

fossil finding sites: North-central PA

Answer 20

• advantages: less expensive, time-consuming, well-understood catskill formation
• disadvantage: not the best exposure

Question 21

fossil finding sites: Ellesmere Island

Answer 21

• advantage: actually quite difficult
• disadvantage: expensive, difficult to travel to, danger latitude because Pangea had Ellesmere by the equator

Question 22

tiktaalik structure

Answer 22

• contains human and fish-like features and found on Ellesmere (has coasts) –> makes sense that it is an intermediate

Question 23

why do land animals differ from fish

Answer 23

• their heads are made more flat –> shape and size of similar structures varies between species

Question 24

Eusthenopteron

Answer 24

• bony formations begin to arise

Question 25

Tiktaalik

Answer 25

• neck formed, can move head without moving shoulders

Question 26

Acanthoslegy

Answer 26

• fully formed digits, real wrists, no fin webbing

Question 27

Shubin et al 2006

Answer 27

• paleontology papers describe functional anatomy, as well as phylogeny associated with fossils

Question 28

ZPA

Answer 28

zone of polarising activity

Question 29

how did scientists identify ZPA

Answer 29

• placing foil between ZPA patches and rest of limbs
  –> showed that ZPA controlled formation of digits

Question 30

forelimb of Tiktaalik is intermediate between Eusthernopteron and Acanthostega because

Answer 30

• has a humerus, radius/ulna and a wrist

Question 31

forelimb of lungfish

Answer 31

• has a single bone at base of forelimb (humerus)

Question 32

ZPA is …

Answer 32

an area of cells where the gene sonic hedgehog is active during the development of digits

Question 33

gene sonic hedgehog gets its name from

Answer 33

• the related gene hedgehog, which in fruit flies make the front of each segment different from the back

Question 34

what the trigeminal nerve innervates

Answer 34

• structures of the first embryonic arch