Week 1: Animal diversity and phylogeny

Question 1

What is Krogh’s principle?

Answer 1

Model organisms are selected for particular characteristics to study specific physiology

Question 2

What are the 4 main deciding factors for which species are chosen to study?

Answer 2

Curiosity, applicability, utility (Krogh’s principle), the phylogenetic position

Question 3

What organism did Hodgkins and Huxley use to study the properties of nervous impulses?

Answer 3

Squid

Question 4

Why is squid a good model organism for studying neurobiology?

Answer 4

Gian axons, (stellate ganglion innervated by stellate nerve containing giant axon)

Question 5

What is the Latin name of the sea slug used as a model in neurobiology, established by Eric Kandel?

Answer 5

Aplysia californica

Question 6

Why is Aplysia californica a good model organism?

Answer 6

Simple nervous system, somata of neurons large (easy to repeatedly identify and stimulate)

Question 7

What is Apylsia californica used to study?

Answer 7

The underlying neurological basis of learning and memory

Question 8

Why is Drosophila melanogaster a good model organism?

Answer 8

4 pairs of chromosomes, short life cycle, small and inexpensive to culture, small genome

Question 9

When was the Drosophila melanogaster genome sequenced?

Answer 9

2000

Question 10

What is the name of the model organism nematode worm established by Brenner in 1965?

Answer 10

Caenorhabditis elegans

Question 11

What is the life cycle of caenorhabditis elegans?

Answer 11

3 days

Question 12

How many cells does caenorhabditis have?

Answer 12

~1000 cells (complete linkage of cells has been mapped)

Question 13

What is caenorhabdidtis elegans used to study?

Answer 13

Molecular and genetic basis of behavior using basis

Question 14

How many genes does caenorhabdidtis have and what else is interesting about its genome?

Answer 14

~19,000

First animal sequenced

Question 15

How are phylogenetic relationships among phyla established? (3 answers)

Answer 15

1. Comparative embrylogy
2. Comparative morphology
3. Molecular phylogenetics

Question 16

What are two things studied in molecular phylogenetics to establish phylogenetic relationships among phyla?

Answer 16

DNA sequence data

Genome organization

Question 17

What are the two types of development studied in comparative embryology that characterize 2 major clades of bilaterian animals?

Answer 17

Protosomes: blastopore becomes mouth
Deuterostomes: blastopore becomes anus

Question 18

What type of cleavage do protosomes and deuterostomes show?

Answer 18

Protosomes: spiral cleavage
Deuterostomes: radial cleavage

Question 19

What differences are there in the formation of the body cavity between protosomes and deuterostomes?

Answer 19

Protosome: mosaic embryo
Deuterostome: regulative embryo

Question 20

What does mosaic embryo mean?

Answer 20

Removal of a cell leads to development arrest

Question 21

What does regulative embryo mean?

Answer 21

Removal of a cell still becomes larvae

Question 22

What is comparative morphology?

Answer 22

Revealing relationships between species when looking at the adult form

Question 23

What cephalochordate used in comparative morphology has a notochord?

Answer 23

Branchiostoma floridae

Question 24

What other similarities does Branchiostoma floridae have?

Answer 24

Endostyle similar to the thyroid gland (contains iodine binding proteins)

Question 25

What is a major advantage to molecular based phylogenetics over comparative morphology and embryology?

Answer 25

Phylogenetic tree generated can give a geographical timescale to work out when the animals evolved

Question 26

Chordata contains which three phylums?

Answer 26

Vertebrata, urochordata, cephalochordata