evolution II Flashcards
(15 cards)
what is the endosymbiosis theory?
→endosymbiotic theory deals with the origins of mitochondria and chloroplasts
→Mitochondria and chloroplasts are believed to have developed from symbiotic bacteria.
what is some evidence for the endosymbiotic evolution of eukaryotic cells?
→mitochondria have their own circular genome which replicates independently of nuclear DNA
→ new mitochondria are produced by fission of existing mitochondria
→ all mitochondrial genomes share similarity with the Typhus bacterium “Rickettsia prowazekii”
what are plastids and where are they found?
→the plastid is a major double-membrane organelle found in the cells of plants, algae, and some other eukaryotic organisms.
what are plastid genomes and what do they encode?
→plastids possess their own genome, the plastome, and a specific machinery to decode its genetic information.
→plastid genomes encode proteins necessary for plastid function.
what are the four basic processes of multicellularity?
→spatial organisation
→change in form
→growth
→differentiation
describe why the evolution of the eye is thought of as being convergent
→The diversity of eyes suggests that they have evolved several times independently (polyphyletic, convergent evolution).
→they also have features in common.
what are the common features in eukaryotic eyes?
→ALL eukaryotes use a homologous family of proteins, opsins, to detect light.
→Opsins are G-protein coupled receptors that convert light to nerve impulses.
→Eukaryotic opsins share sequence homology and have diverged to detect different wavelengths of light.
what are homologues, paralogues and orthologues?
→Homologues are related by descent from a common ancestor.
→Paralogues are homologues within the same species.
→ Orthologues are homologues between species.
how many Hox genes do vertebrates have and how have they arisen?
→Vertebrates have four Hox gene clusters
→which have arisen from two duplication events of an ancestral chromosome.
what does Pax 6 have to do with the development of the eye?
→Being eyeless is orthologous to Pax6 in humans and mice.
→The ectopic (differently placed) expression of the eyeless gene in drosophilia (fruit flies) leads to ectopic eyes.
→Pax6 is involved in eye development throughout the animal kingdom.
how can eye loss occur as a result of evolution? and give an example
→some animals have evolved from surface-dwelling forms to underground forms
→Eye loss is a common feature in such animals because eyes are energetically expensive
→ Mexican, blind cavefish
→Its surface-dwelling ancestor has eyes, but the derived, cave-dwelling form doesn’t.
why are there differences in morphology between animals which are genetically related?
→morphological differences are established during development.
→even though it’s reproductive, selective pressure acts on the adult form.
→animals share the vast majority of their genes, but the regulation of gene expression differs between them.
how do we know where Homo-sapiens come from?
→We can get evidence from the fossil record and from molecular analyses.
→Mitochondria are maternally inherited.
→The mitochondrial genome replicates independently of the nuclear genome and does not undergo recombination
→the male Y chromosome does not have a homologous female chromosome to recombine with.
→Changes in sequence of mtDNA and the Y chromosome are due to random mutations over time.
→analysis of mtDNA and Y chromosome sequence shows maternal and paternal origin, respectively.
what is the RNA world hypothesis?
→ early life is thought to have been based on self-replicating and self catalyzing RNA molecules
→ catalytic RNAs are present in organisms from bacteria to humans
why did RNA world evolve into DNA?
→DNA is more stable than RNA
→ there is a greater range of protein enzymes and they are more robust
