Evolution Flashcards
Define evolution(3)
Accumulated, heritable changes within a population, over generations, giving rise to new species
- New species arise from earlier species
- Evolution is an observable fact. The process by which it has most likely occurred, natural selection, is a theory. Theory because we cannot observe it.
Why are mutations important?(3)
· Mutation rates can act as molecular clocks
· Mistakes/ mutations accumulate over time
· Species that share a recent common ancestor with fewer differences than species that are more distantly related
How are phylogenetic trees made?(2)
· Molecular differences can be used to construct phylogenetic trees.
· Myoglobin evolution- a molecular phylogenetic tree.
What is the difference between classification and taxonomy?
- Taxonomy- naming groups of organisms
- Classification- arranging taxa into an ordered hierarchical system
What is the difference between genetic flow and drift?
- Genetic drift- Variation in relative frequency of different genotypes in small populations
- Gene flow- transfer of alleles from one population to another
Describe the experimented conducted to show evolution using e.coli(4)
“• 12 colonies of E. coli all derived from a single clone.
The bacteria growing in citrate in the presence of oxygen. In low amounts of glucose their preferred energy source. High citrate levels cannot be used in oxygen
- Everyday for 31 years, 10 % of each have been removed for subculture
- Freeze culture samples every 500 generations 75 days • Over 73000 generations have been observed • Differences between cultures have emerged over the years “
What were the results of the e.coli experiment(3)
- One group developed ability to use citrate in oxygen evolved after about 30000 generations in one group
- E. coli can’t use citrate in oxygen because gene is turned off in oxygen
- Earlier generations from this same ancestral e. coli were repeatedly able to evolve the ability to use citrate at about the same time
Describe citrate use in e.coli(7)
→The ability of bacteria to utilise citrate is controlled by its citrate gene, controlled by the citrate promoter.
→gene is normally turned off in the presence of oxygen.
→ It is next to the RNK promoter, which controls the RNK gene.
→This is turned on in the presence of oxygen.
→in cultures that were able to utilise citrate, the citrate gene and RNK promoter were duplicated right after each other.
→this doesn’t affect the existing citrate gene, but the duplicated citrate has an RNK promoter before it which means it is under the control of the RNK promoter.
→citrate gene now works in the presence of oxygen.
So E.coli can survive in citrate
Describe the evidence of homology and analogy(3)
Humans have humerus, radius and the ulna and the metacarpals
That pattern is conserved through all tetrapods.
single element- stylopod, the paired element is zeugopod, autopods- hand digits.
In the horse- the radius and ulna have fused like the metacarpals have fused. “
what does analogous mean in relation to evolution?(3)
→ two structures are analogous when they have no common ancestor
→ the similar structures are produced by selection to meet similar function (convergent evolution)
→ they have different developmental mechanisms but some molecular components may be the same. An example would be insect wings and bird wings.
What are crystallins?(7)
crystallins are all proteins that have been adapted from their original function to be constituents of the optics of animal eyes • Alpha crystallins are related to HSPs- heat shock
- So have been recruited to a lens function
- Beta/gamma crystallins are homologous
- But many other different lens proteins exist in different species
- These tend to be enzymes/have enzymatic activity
- in addition to being soluble, stable, transparent & refractive
what does homologous mean in relation to evolution?(2)
→two structures are homologous when they are derived from a common ancestral version.
→these structures are derived from a common ancestor so they form by a common mechanism. An example would be tetrapod limbs.
Describe the difference between paralogues and orthologues and give examples with hox genes
• Two genes from same organism (by duplication) – paralogs- species (eg Mouse Hox a1, a2, a3, a4 etc are paralogues)
Two genes from different organisms (common ancestor) – orthologs eg the fruit fly Antennapedia gene is the orthologue of mouse Hox a6, b6, c6”
What are hox genes?(4)
Hox genes control the body plan of organisms with each hox gene coding for a specific body part.
- Hox genes represent transcription factors
- Hox genes bind DNA in a sequence-specific fashion and regulate the expression of adjacent/nearby genes
- Confer positional identity along the Anterior-Posterior (cranio-caudal) axis
Describe hox genes in Drosophilia(5)
• Segments in the larvae stage of the insect.
T2 and T3 is where antonpoedia gene is expressed- tells those segments to be thoraxic.
- Mutation is not disruption of gene but to mis expressed in the head region and directs appendages to form legs.
- there are 8 hox genes duplicated from an ancestral form.
- • Different hox genes are expressed in head to tail pattern in the organism and are homologues of one another. “
Describe hox gene evolution in humans(3)
“Ancestral hox gene emerged and it was duplicated and duplicate
- In vertebrates the cluster has been duplicated and duplicated again so that there are 4 gene clusters ranging from numbers 1-13.
- There have been losses of genes in the clusters but fundamentals has remained Genes toward the left is the head and genes toward the right is the tail end “
What are the shared characteristics between the three domains?
