Week 1: Animal diversity and phylogeny Flashcards
What is Krogh’s principle?
Model organisms are selected for particular characteristics to study specific physiology
What are the 4 main deciding factors for which species are chosen to study?
Curiosity, applicability, utility (Krogh’s principle), the phylogenetic position
What organism did Hodgkins and Huxley use to study the properties of nervous impulses?
Squid
Why is squid a good model organism for studying neurobiology?
Gian axons, (stellate ganglion innervated by stellate nerve containing giant axon)
What is the Latin name of the sea slug used as a model in neurobiology, established by Eric Kandel?
Aplysia californica
Why is Aplysia californica a good model organism?
Simple nervous system, somata of neurons large (easy to repeatedly identify and stimulate)
What is Apylsia californica used to study?
The underlying neurological basis of learning and memory
Why is Drosophila melanogaster a good model organism?
4 pairs of chromosomes, short life cycle, small and inexpensive to culture, small genome
When was the Drosophila melanogaster genome sequenced?
2000
What is the name of the model organism nematode worm established by Brenner in 1965?
Caenorhabditis elegans
What is the life cycle of caenorhabditis elegans?
3 days
How many cells does caenorhabditis have?
~1000 cells (complete linkage of cells has been mapped)
What is caenorhabdidtis elegans used to study?
Molecular and genetic basis of behavior using basis
How many genes does caenorhabdidtis have and what else is interesting about its genome?
~19,000
First animal sequenced
How are phylogenetic relationships among phyla established? (3 answers)
- Comparative embrylogy
- Comparative morphology
- Molecular phylogenetics
What are two things studied in molecular phylogenetics to establish phylogenetic relationships among phyla?
DNA sequence data
Genome organization
What are the two types of development studied in comparative embryology that characterize 2 major clades of bilaterian animals?
Protosomes: blastopore becomes mouth
Deuterostomes: blastopore becomes anus
What type of cleavage do protosomes and deuterostomes show?
Protosomes: spiral cleavage
Deuterostomes: radial cleavage
What differences are there in the formation of the body cavity between protosomes and deuterostomes?
Protosome: mosaic embryo
Deuterostome: regulative embryo
What does mosaic embryo mean?
Removal of a cell leads to development arrest
What does regulative embryo mean?
Removal of a cell still becomes larvae
What is comparative morphology?
Revealing relationships between species when looking at the adult form
What cephalochordate used in comparative morphology has a notochord?
Branchiostoma floridae
What other similarities does Branchiostoma floridae have?
Endostyle similar to the thyroid gland (contains iodine binding proteins)
What is a major advantage to molecular based phylogenetics over comparative morphology and embryology?
Phylogenetic tree generated can give a geographical timescale to work out when the animals evolved
Chordata contains which three phylums?
Vertebrata, urochordata, cephalochordata
